State of California 

AIR RESOURCES BOARD 

STAFF REPORT: 

INITIAL STATEMENT OF REASONS FOR PROPOSED RULEMAKING 

Technical Status and Revisions to Malfunction and Diagnostic System Requirements for 

Heavy-Duty Engines (HD OBD) and Passenger Cars, Light-Duty Trucks, and MediumDuty Vehicles and Engines (OBD II) 

Date of Release: April 10, 2009 

Scheduled for Consideration: May 28, 2009 

This document has been reviewed by the staff of the California Air Resources Board 

and approved for publication. Approval does not signify that the contents necessarily 

reflect the views and policies for the Air Resources Board, nor does mention of trade 

names or commercial products constitute endorsement or recommendation for use. 
Table of Contents 

I. SUMMARY OF STAFF PROPOSAL AND RELATED POLICY ISSUES........................3

II. TECHNICAL STATUS UPDATE AND PROPOSED REVISIONS TO HEAVY-DUTY 

OBD MONITORING REQUIREMENTS..........................................................................8

A. INFREQUENT REGENERATION ADJUSTMENT FACTORS ......................................8

B. DIESEL FUEL SYSTEM MONITORING .....................................................................12

C. DIESEL EXHAUST GAS RECIRCULATION (EGR) SYSTEM MONITORING............14

D. DIESEL BOOST PRESSURE CONTROL SYSTEM MONITORING...........................15

E. DIESEL NON-METHANE HYDROCARBON (NMHC) CONVERTING CATALYST 

MONITORING..................................................................................................................16

F. DIESEL OXIDES OF NITROGEN (NOx) CONVERTING CATALYST MONITORING 21

G. DIESEL NOx ADSORBER MONITORING..................................................................25

H. DIESEL PARTICULATE MATTER (PM) FILTER MONITORING................................25

I. DIESEL EXHAUST GAS SENSOR MONITORING.....................................................29

J. GASOLINE FUEL SYSTEM MONITORING................................................................29

K. GASOLINE MISFIRE MONITORING ..........................................................................31

L. GASOLINE SECONDARY AIR SYSTEM MONITORING ...........................................32

M. GASOLINE EVAPORATIVE SYSTEM MONITORING................................................32

N. GASOLINE EXHAUST GAS SENSOR MONITORING ...............................................32

O. COLD START EMISSION REDUCTION STRATEGY MONITORING ........................35

P. ENGINE COOLING SYSTEM MONITORING.............................................................37

Q. CRANKCASE VENTILATION (CV) SYSTEM MONITORING .....................................40

R. COMPREHENSIVE COMPONENT MONITORING ....................................................41

S. EMISSION-RELATED COMPONENT FAILURE MODES...........................................44

T. EMISSION CONTROL STRATEGIES.........................................................................46

U. OTHER PROPOSED AMENDMENTS........................................................................47

III. PROPOSED REVISIONS TO OBD II REGULATION...................................................47

IV. PROPOSED REVISIONS TO HEAVY-DUTY OBD STANDARDIZATION 

REQUIREMENTS.........................................................................................................48

A. REFERENCE DOCUMENTS......................................................................................48

B. PERMANENT FAULT CODES....................................................................................48

C. ACCESS TO ADDITIONAL DATA THROUGH A GENERIC SCAN TOOL .................49

D. EMISSION-RELATED TEST RESULTS .....................................................................50

E. IDENTIFICATION AND VERIFICATION NUMBERS ..................................................50

F. EMISSION-INCREASING AUXILIARY EMISSION CONTROL DEVICE (EI-AECD) 

TRACKING.......................................................................................................................52

G. SERVICE INFORMATION REQUIREMENTS.............................................................54

V. PROPOSED REVISIONS TO HEAVY-DUTY OBD DEMONSTRATION TESTING 

REQUIREMENTS.........................................................................................................56

VI. PROPOSED REVISIONS TO HEAVY-DUTY OBD CERTIFICATION REQUIREMENTS62

A. CERTIFICATION APPLICATION ................................................................................62

B. IN-USE COMPLIANCE TESTING...............................................................................62

VII. PROPOSED REVISIONS TO HEAVY-DUTY OBD STANDARDIZED METHOD TO 

MEASURE REAL WORLD MONITORING PERFORMANCE ......................................63

VIII.PROPOSED REVISIONS TO OBD II REGULATION...................................................66

IX. PROPOSED HEAVY-DUTY OBD ENFORCEMENT REGULATION............................67
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A. OVERVIEW.................................................................................................................67

B. THE NEED FOR HD OBD-SPECIFIC ENFORCEMENT PROCEDURES ..................69

C. AUTHORITY TO ADOPT ENFORCEMENT PROCEDURES .....................................69

D. SUMMARY OF THE HD OBD COMPLIANCE/ENFORCEMENT REGULATION .......71

E. INTERIM IN-USE RELIEF...........................................................................................85

F. RESPONSIBLE PARTY..............................................................................................85

X. ANALYSIS OF ENVIRONMENTAL IMPACTS AND ENVIRONMENTAL JUSTICE 

ISSUES ........................................................................................................................85

XI. COST IMPACT OF THE PROPOSED REQUIREMENTS............................................87

A. COST OF THE PROPOSED REQUIREMENTS .........................................................87

B. COSTS OF THE HD OBD ENFORCEMENT PROGRAM...........................................88

C. COST EFFECTIVENESS OF THE PROPOSED REQUIREMENTS...........................90

XII. ECONOMIC IMPACT ANALYSIS.................................................................................90

A. LEGAL REQUIREMENTS...........................................................................................90

B. AFFECTED BUSINESSES AND POTENTIAL IMPACTS ...........................................91

C. POTENTIAL IMPACTS ON VEHICLE OPERATORS .................................................91

D. POTENTIAL IMPACTS ON BUSINESS COMPETITIVENESS...................................92

E. POTENTIAL IMPACTS ON EMPLOYMENT ...............................................................92

F. POTENTIAL IMPACT ON BUSINESS CREATION, ELIMINATION, OR EXPANSION92

REFERENCES....................................................................................................................93

APPENDIX I ........................................................................................................................95
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I. SUMMARY OF STAFF PROPOSAL AND RELATED POLICY ISSUES 

Background

On-board diagnostic (OBD) systems are comprised mainly of software designed into the 

vehicle’s on-board computer to detect emission control system malfunctions as they 

occur by monitoring virtually every component and system that can cause an increase 

in emissions. When an emission-related malfunction is detected, the OBD system 

alerts the vehicle owner by illuminating the malfunction indicator light (MIL) on the 

instrument panel. By alerting the owner of malfunctions as they occur, repairs can be 

sought promptly, which results in fewer emissions from the vehicle. Additionally, the 

OBD system stores important information including identification of the faulty 

component or system and the nature of the fault, which would allow for quick diagnosis 

and proper repair of the problem by technicians. This helps owners achieve less 

expensive repairs and promotes repairs done correctly the first time. 

The California Air Resources Board (ARB) originally adopted the light- and medium-duty 

vehicle OBD regulation (OBD II) in 1989 for the 1996 and newer model years. As 

directed by the Board, the regulation has been reviewed and updated at regular updates 

since then. ARB also adopted separate heavy-duty OBD requirements (HD OBD) in 

2005 that apply to 2010 and subsequent model year heavy-duty engines and vehicles 

(i.e., vehicles with a gross vehicle weight rating greater than 14,000 pounds). Again, as 

directed by the Board, ARB staff has been meeting with manufacturers since the 

original rulemaking to review progress in meeting the requirements and has identified a 

number of issues that necessitate amendments to the regulations. 

To address the issues, staff is proposing changes to the HD OBD regulation, California 

Code of Regulations (Cal. Code Regs.), title 13, section 1971.1 (included as Attachment 

A). Further, to harmonize these changes for heavy-duty engines and for medium-duty 

engines, staff is also proposing changes to the OBD II regulation, Cal. Code Regs., title 

13, section 1968.2 (included as Attachment B). Lastly, as ARB staff indicated during 

the 2005 HD OBD rulemaking process, staff is proposing adoption of a HD OBD 

enforcement regulation, Cal. Code Regs., title 13, section 1971.5 (included as 

Attachment C), which would establish enforcement procedures and requirements. 

Summary of Proposed Amendments

A summary of the issues and technical amendments is provided below while detailed 

explanations of each of these issues and amendments are provided in sections II 

through VII of this report. Of the proposed amendments to the HD OBD and OBD II 

regulations, many have been largely agreed upon between ARB and manufacturers 

based on various discussions and meetings, and include the following: 

• Clarifying storage and erasure of permanent fault codes. 

• Revising in-use monitoring frequency tracking for the particulate matter (PM) filter 

monitor. 
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• Revising the definition of “idle” for several tracking requirements. 

• Revising diesel fuel system monitoring requirements for non-common rail systems. 

• Revising the diesel PM filter monitor malfunction thresholds for 2010-2012 model 

years. 

• Delaying some monitoring requirements for catalyzed PM filters and diesel NMHC 

converting catalysts to the 2013 model year. 

• Deleting the monitoring requirement for MIL circuit faults. 

Staff is also proposing amendments to the HD OBD requirements for gasoline engines 

to be consistent with those already required in the OBD II regulation, including the 

following: 

• Requiring detection of air-fuel ratio cylinder imbalance failures. 

• Clarifying the gasoline primary and secondary oxygen sensor monitoring 

requirements. 

In addition to these proposed amendments, there are a few issues that ARB and 

manufacturers have not completely agreed upon. While manufacturers have 

expressed concerns with them, staff believes that they are necessary to ensure the 

integrity of the OBD systems. These amendments include: 

Monitoring of transmission vehicle speed sensors 

At the manufacturers’ request, the HD OBD regulation currently excludes transmission 

components from the system unless the manufacturer specifically uses such a 

component for other monitors (e.g., uses transmission vehicle speed sensor to 

enable/disable PM filter monitoring). However, manufacturers have now indicated they 

need to use the vehicle speed input from the transmission but do not want to thoroughly 

monitor the vehicle speed sensor itself or to cover it under the emission warranty if it 

fails. Fundamentally, staff disagrees and stands behind the OBD policy—if a 

component is used for monitoring something else, the component itself must be 

monitored to ensure the integrity of the whole system. Deviation from this policy would 

allow development of non-robust system designs in which certain components (e.g., 

speed sensor) could fail and disable monitoring of more crucial emission controls (e.g., 

PM filter), and yet go undetected and uncorrected for indefinite periods of time. 

NOx catalyst emission thresholds 

Another issue is the malfunction threshold for NOx converting catalysts such as 

selective catalytic reduction (SCR) systems. Currently, manufacturers are required to 

detect a catalyst fault before tailpipe emissions exceed 0.5 g/bhp-hr NOx on 2010 

engines with a NOx standard of 0.2 g/bhp-hr. Manufacturers have argued such a level 

is infeasible given current NOx sensor technology and that the threshold should be 

raised to 0.8 g/bhp-hr. After meeting with manufacturers, sensor suppliers, and 

analyzing what little data is available, ARB believes some increase is warranted 

although it is not convinced that the current NOx sensor capability necessitates raising 

the threshold as high as manufacturers have requested. Consequently, it is proposing a 

new threshold of 0.6 g/bhp-hr. ARB staff has identified several possible monitoring 

strategies that could be done with current NOX sensor technology and still meet the 
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proposed threshold. Additionally, manufacturers have not provided any data supporting 

their proposed threshold. 

AECD tracking 

Another proposed amendment of concern to heavy-duty manufacturers is the 

requirement to track in-use activity of auxiliary emission control devices (AECDs) that 

adversely affect emissions (emission-increasing AECDs, or EI-AECDs). Light- and 

medium-duty diesel manufacturers made similar arguments against tracking EI-AECDs 

when it was first adopted in the OBD II regulation in 2006. Then and now, 

manufacturers have argued that the OBD regulation is not the appropriate place for this 

requirement, that confidentiality would be compromised, and that the requirement would 

impose a large resource burden. Staff finds these arguments to be unsubstantiated and 

that this requirement is necessary to ensure that these EI-AECDs are active as 

infrequently as possible in-use (to minimize any associated adverse emission impact) 

and are implemented equitably by all manufacturers. In the OBD II regulation, staff 

modified its initial proposal to address or eliminate manufacturer concerns and the same 

amendments are now being proposed for the HD OBD regulation. 

In addition to the above issues, there are three issues where staff and industry have 

stronger disagreements. These ‘issues of controversy’ involve provisions of the new 

enforcement regulation, aging requirements for demonstration testing, and accounting 

for emissions from infrequent regeneration events (e.g., PM filter regenerations) when 

calibrating.

Enforcement regulation 

Manufacturers have objected to provisions within the newly-proposed HD OBD 

enforcement regulation (§1971.5) citing lack of legal authority and resource limitations. 

Specifically, the proposal requires manufacturers to perform testing on a limited number 

of their own engines after they have reached high mileage to ensure that OBD monitors 

are working properly. Since these requirements would require manufacturers to remove 

engines and emission controls from actual in-use vehicles and to emission test each 

threshold monitor on an engine dynamometer, manufacturers have argued that ARB 

has no authority to adopt requirements beyond certification and that this would impose 

significant added workload and costs that should instead be borne by ARB. Staff 

disagrees as ARB has clear authority to adopt enforcement test procedures to ensure 

its regulations are met and there is no restriction that such procedures are limited to 

items that are conducted prior to certification or limited to those carried out only by ARB. 

Further, performing these procedures would be a condition for certification and would be 

used to ensure engines are compliant with the other certification requirements 

consistent with other ARB regulations that require manufacturer compliance testing. 

Under the procedures, ARB would also have the authority to perform enforcement 

testing but given the complexity, expense, and lack of an ARB facility capable of such 

engine dynamometer emission testing, it is expected that ARB will be heavily reliant on 

the self-testing done by manufacturers for enforcement purposes. Manufacturers on the 

other hand, have the facilities and expertise to test their own engines and emission 

controls as it is already a necessary part of development, calibration, and certification. 
6

Regarding workload and costs to perform such testing, ARB is proposing manufacturers 

test 1-3 engines per year (depending on the number of engine families sold by the 

engine manufacturer) and has done a cost analysis (see section XI.) for this testing. 

Staff’s analysis found the increased costs to be less than $2 per engine produced by a 

typical manufacturer (or less than 0.01 percent of the engine retail cost). Given that the 

testing would not typically be conducted until three to four years after the engine is first 

sold, staff also believes that testing resources (personnel, lab availability, etc.) will be 

adequately available and will not infringe upon the testing needed for 2010 or 2013 

model year calibration workloads. Further, ARB investigated cheaper alternatives to 

engine dynamometer testing such as screening engines using portable emission 

measurement systems while the engine is still in the vehicle or using chassis (vehicle) 

dynamometers to determine if further testing is warranted. Unfortunately, several 

complications were encountered that, at this time, render such screening infeasible. 

Staff has discussed this with industry and, given that the first engines would not likely be 

tested until the 2013 calendar year, has indicated that it is still open to alternative testing 

suggestions that may be taken into consideration in a future regulatory update. 

Demonstration Testing 

An essential element of the current regulation requires manufacturers to perform 

demonstration testing prior to certification. Depending on the size of the manufacturer, 

manufacturers would have to perform a series of emission tests on 1-3 engine families 

per year to confirm a subset of OBD monitors are calibrated correctly (e.g., that a fault is 

detected before emissions exceed 2.0 times the tailpipe standards). While this ‘spotcheck’ testing is done on a prototype engine prior to certification, manufacturers and 

staff have disagreed as to the level of aging that is needed on the engine and emission 

controls for this testing. Staff has proposed amendments that would require a 

manufacturer, by 2016, to develop and validate aging procedures that would allow them 

to rapidly simulate high mileage and do the demonstration testing on a complete system 

(engine and emission controls) that is aged to the equivalent of full useful life (the point 

up to which the tailpipe emission standards apply such as 435,000 miles for the 

heaviest engines). Manufacturers have instead proposed that they be allowed to age 

only portions of the emission controls (specifically, the aftertreatment) and not age the 

engine or other emission controls. Further, they have proposed that they be required to 

age to a much lower mileage point and ‘extrapolate’ or project likely emission levels 

from there. They argue that staff’s proposed requirement that they validate their aging 

cycles by gathering data on actual in-use high mileage engines is unnecessary. Staff 

disagrees, having found that because diesel engines and emission controls are 

becoming more and more complex, staff’s proposal is the only way to accurately 

determine how high emissions will be when a fault occurs. Accordingly, manufacturers 

should be required to generate high-mileage systems that represent both the engine 

and emission controls in that it is the only way to ensure that a manufacturer’s aging 

procedure produces aged systems similar to those of engines in-use. 

Infrequent Regeneration Adjustment Factors (IRAFs) 

For normal tailpipe certification, manufacturers are currently required to include the 

emissions from infrequent regeneration events, such as a PM filter regeneration that 
7

may happen every 300 miles, and account for such emissions by averaging them out 

over the frequency with which they occur. For example, an event that happens once 

every ten FTP emission tests would be spread out over all ten so that 1/10th of the 

increase is added to each individual test before being compared to the emission 

standard. Similarly, when calibrating for OBD emission threshold monitors (e.g., NMHC 

catalyst conversion efficiency faults that must be detected before emissions exceed 2.5 

times the FTP standard), manufacturers are required to assess the impact of the fault 

on their baseline calculated IRAF so that a fault is detected before the emissions 

exceed the threshold including accounting for these infrequent regeneration events. 

Much concern has been raised by manufacturers about the current requirements to 

account for IRAFs when calibrating HD OBD systems including the necessity of it and 

especially the cost and resources to do so. Staff and manufacturers made progress 

towards a common ground by agreeing to account for IRAFs primarily by using 

engineering analysis and/or data to estimate modifications to the baseline IRAFs rather 

than full rigorous development of new IRAFs for each malfunction. However, staff and 

manufacturers have disagreed on how best to implement such engineering 

judgment/allowances in the regulation. The current proposal requires manufacturers to 

develop and submit their estimates to ARB and for ARB to approve the estimates upon 

the manufacturer providing data and/or engineering evaluation demonstrating the 

procedure used to develop the estimates is consistent with good engineering judgment. 

The manufacturers, however, have argued that they are unsure as to what constitutes 

good ‘enough’ engineering judgment to be accepted by ARB. Manufacturers have 

proposed modifications that would limit the number of monitors they would have to 

investigate or develop separate IRAFs for because they are concerned that staff will be 

unreasonable or disagree as to what is good engineering judgment. This argument 

seems specious in that sound engineering judgment underlies a number of OBD 

decisions that ARB must make and has not previously been a significant issue of 

controversy. This includes determining what kind of malfunction is most likely to yield 

the highest emissions for a given threshold-based monitored component and deciding 

what kind of driving cycle will reveal the highest emission increase to determine whether 

a component even needs to be functionally monitored. What matters most in all 

engineering evaluations is that the analysis and data used in arriving at the decision are 

documented and well-founded. Further, in the case of IRAF adjustment factors, should 

an engineering evaluation ultimately contain a flaw that isn’t easily anticipated by the 

manufacturer or ARB and results in higher than expected regeneration emission 

impacts during in-use compliance testing, the proposed heavy-duty OBD enforcement 

regulation provides relief in two forms. First, through the 2012 model year, ARB will use 

the adjusted IRAF estimated by the manufacturer at the time of certification for 

determining compliance even if testing of in-use engines shows the estimate to be 

wrong. Second, the ARB will not consider a system noncompliant if it is caused by 

something that could not have been reasonably foreseen by the manufacturer. 

Emission and cost impacts

Emission benefits, costs, and cost-effectiveness were calculated when the HD OBD 

regulation was originally adopted in 2005. While the proposed amendments to the HD 
8

OBD regulation do not materially alter the previously calculated values, changes to the 

base emission inventory in the last few years has necessitated new calculations. The 

proposed HD enforcement regulation also adds new costs that have not previously 

been considered. The new analysis has found the lifetime HD OBD emission benefits 

including the amendments would be 165 pounds of ROG, 2000 pounds of NOx, and 14 

pounds of PM per heavy-duty engine. It has further found that, including the proposed 

amendments, the HD OBD requirements result in a $132.39 increase in retail price of 

the engine plus an additional $1.97 for the new enforcement regulation. When 

combined with an estimated $496 increase in emission repair costs for items that 

previously would have gone undetected and uncorrected, the cost-effectiveness of the 

HD OBD program would be $0.15 per pound of ROG + NOx and $22.50 per pound of 

PM. Both values compare favorably with the cost-effectiveness of other recently 

adopted regulations. Further details of the emission benefit, costs, and costeffectiveness calculations are in sections X. and XI. 

Recommendation

ARB staff recommends that the Board adopt the amendments to the OBD II and HD 

OBD regulations and adopt the HD OBD enforcement regulation as proposed in the 

Initial Statement of Reasons. 

II. TECHNICAL STATUS UPDATE AND PROPOSED REVISIONS TO HEAVY-DUTY 

OBD MONITORING REQUIREMENTS 

A. INFREQUENT REGENERATION ADJUSTMENT FACTORS 

Diesel emission control technology has been rapidly evolving in recent years to allow 

engines to achieve compliance with lower tailpipe standards. However, some of the 

new emission controls do not work in a traditional manner of continuously reducing 

emissions. Instead, these components effectively reduce emissions for some amount of 

time and then temporarily require an alternate mode of operation to renew/regenerate 

the component before it can resume effectively reducing emissions. Two examples of 

such emission controls are the particulate matter (PM) filter, which typically requires an 

active regeneration event every 300 to 500 miles to burn off the accumulated soot, and 

an oxides of nitrogen (NOx) adsorber, which periodically requires a desulfurization 

event. When these infrequent, but periodic, events occur, tailpipe emissions can 

increase dramatically and exceed the allowable tailpipe standards. Accordingly, the 

tailpipe standards require diesel engine manufacturers to account for these infrequent 

emission increases and include them as part of their emission measurement when 

determining compliance with the tailpipe standard. Since these events occur 

infrequently, the emission test procedures define a method for manufacturers to account 

for the additional emissions by taking into account the frequency of the events, the 

magnitude of emission increase of the event, and the duration of the event. For a 

simple example, take a regeneration event that is active once within every ten emission 

tests, causes an emission increase of 1.3 grams per brake-horsepower hour (g/bhp-hr) 

NOx, and takes less than one emission test to complete. The emission test procedures 
9

would require one-tenth of the 1.3 g/bhp-hr increase, or 0.13 g/bhp-hr, to be added to 

emission test results obtained without the event, and this total would be compared to 

the tailpipe emission standard. This method allows the excess emissions generated 

during the infrequent event to be spread out across all emission tests between 

successive events and to provide a representative average emission level from the 

vehicle. Manufacturers are all aware of these provisions and have been performing 

such measurements as part of their certification process since they began using 

emission controls with infrequent regeneration events. 

Within OBD, there are several malfunctions that are required to be detected prior to 

emissions exceeding defined tailpipe levels (e.g., prior to emissions exceeding 2.0 times 

the standard). Because infrequent regeneration events do affect overall emissions from 

the vehicle, the OBD regulation also requires diesel engine manufacturers to account 

for these events when calibrating diagnostics that are tied to defined emission levels. 

Further, the presence of the malfunction itself can affect the regeneration event (in 

frequency, duration, or even magnitude of emission increase) so manufacturers are 

currently required to take those effects into account and calibrate such that the average 

emission level from the engine, including adjustments for infrequent regeneration events 

with a malfunction present, is at or below the required OBD malfunction threshold. 

However, engine manufacturers have requested this requirement to account for impacts 

on infrequent regeneration adjustment factors when calibrating OBD monitors 

(§1968.2(d)(6.2)) be eliminated or changed. 

First, manufacturers have argued that the additional testing time and resources to 

properly determine the adjustment factors are significant and costly. Second, the 

tailpipe emission certification process already ensures the emission solution is robust 

and includes the emission impact of the infrequent regeneration processes. Thus, they 

argue, there is little added benefit in determining unique infrequent regeneration 

adjustment factors (IRAFs) for each OBD malfunction. Accordingly, they have asked 

staff to eliminate the requirement to account for changes in IRAFs due to threshold 

parts and to either ignore IRAFs altogether or to allow the certification IRAFs to be 

applied instead. ARB, however, does not agree with the manufacturers' position and is 

not proposing elimination or modification of this requirement. 

Manufacturers have indicated it takes substantial test time and resources to establish 

IRAFs for tailpipe certification and repeating that process for each OBD threshold would 

be an enormous task. ARB staff, however, believes manufacturers would not need to 

repeat the entire process to determine what, if any, impact the presence of a 

malfunctioning component will have on IRAFs. The costs and resources necessary 

should be very limited, requiring only a small amount of additional resources and 

emission testing (if needed), and should be nowhere near the level of effort required to 

generate the baseline factors for tailpipe certification. For this reason, staff’s cost 

analysis apportioned only a small amount of resources to the specific task of 

determining unique IRAFs. The engineers that are carrying out calibration of OBD 

malfunctions (which involves iterative emission testing with a varying degree of a 

malfunctioning part) must have a detailed understanding of the engine and interactions 
10

between various components, especially in cases where a component is malfunctioning. 

This knowledge is necessary to design a robust diagnostic that will comprehend these 

interactions and still make correct decisions. This is the very same type of knowledge 

staff expects manufacturers to use to determine if there is an impact to the adjustment 

factors that warrants further analysis or testing to identify the magnitude of the change 

to the baseline factors. Specifically, the baseline factors would only be affected if the 

implanted malfunction causes significantly higher PM accumulation rates in the PM filter 

(such that active regeneration would be triggered more frequently) or causes emissions 

during an actual regeneration event to be significantly different. Staff expects 

manufacturers to be able to reasonably estimate whether either of those two cases is 

likely and, for those that are, use existing or additional emission test data to determine 

the impact. The baseline factors would then be scaled accordingly. 

Manufacturers have argued that they conduct lengthy test processes to accurately 

quantify the interval between regeneration events for tailpipe certification and repeating 

such tests would be a costly use of resources. However, it is not expected that a 

manufacturer would have to implant the fault and continue testing until a regeneration 

event occurs to be able to make that determination. Manufacturers would be able to 

reasonably extrapolate the impact using shorter test intervals by looking at data 

captured during the iterative emission testing being done for the OBD threshold 

calibration. As an example, by gathering data of the PM filter loading (e.g., by looking at 

engine-out PM emissions or more likely, the rate of accumulation for the various 

regeneration triggers) during testing with an implanted malfunction and comparing it to 

baseline testing, manufacturers would be able to determine if the malfunction is likely 

going to lead to more frequent or less frequent regeneration and by how much. Such 

data would be sufficient to determine the necessary adjustment to the baseline 

frequency factor. For those malfunctions that the manufacturer has determined are 

likely to have an impact on regeneration emissions themselves, manufacturers may 

have to carry out an additional test with a malfunctioning component present and 

regeneration active and compare the results to the baseline to determine the magnitude 

of the adjustment to the baseline factors. However, even this ‘additional’ test may likely 

be encountered during the normal calibration of the OBD threshold or could be 

intrusively triggered by inserting a loaded PM filter or altering the regeneration triggers 

to force the regeneration to happen while the faulty part is installed. As the 

manufacturer applies similar strategies and controls across its product line, this process 

would likely be refined even further to make capturing the necessary data an automatic 

step during the calibration process and thus, virtually eliminate the need for any 

additional testing. 

Some manufacturers have suggested they would encounter substantial additional 

testing to develop adjusted IRAFs in spite of staff examples of how the process could be 

shortened using engineering judgment. Manufacturers claim that they cannot be sure 

their own engineering judgment is “good enough.” They believe that, to ensure 

emissions are below required IRAF-based OBD thresholds with a faulty component 

present, nothing short of full-scale testing could be used. Manufacturers have even 

proposed modifications that would limit the number of monitors they would have to 
11

investigate or develop separate IRAFs for because they are concerned that staff will be 

unreasonable or disagree as to what good engineering judgment consists of. This 

argument seems specious, however, since a great deal of OBD decisions require sound 

engineering judgment to be applied - from determining what kind of malfunction is most 

likely to yield the highest emissions for a given threshold-based monitored component 

to deciding what kind of driving cycle will reveal the highest emission increase to 

determine whether a component even needs to be functionally monitored. What 

matters most is that the analysis and data used in arriving at the adjusted IRAF are 

documented and well-founded. Should an estimating methodology contain a flaw that 

isn’t easily anticipated, leading to higher than expected regeneration emission impacts 

during in-use compliance testing or some other reasonably non-anticipated effect takes 

place, the proposed heavy-duty OBD enforcement regulation (§1971.5) provides relief 

in that ARB may not consider a system noncompliant if it is caused by something that 

could not have been reasonably foreseen by the manufacturer. 

In OBD, there are several malfunction thresholds that require calibration to ensure 

malfunctions are detected before they exceed prescribed emission limits. These 

malfunctions may affect engine-out emission levels or aftertreatment performance (e.g., 

conversion efficiency of pollutants) which, in turn, can alter the regeneration frequency 

or emission levels during a regeneration event much more than when all components in 

the system are operating normally. Therefore, the manufacturers’ position that the 

baseline tailpipe emission certification process already accounts for the emission impact 

of the infrequent regeneration processes is incorrect. Without re-determining the 

frequency or measuring the new emission levels, a manufacturer cannot verify that the 

total emissions from the vehicle, on average, will be at or below the required OBD 

threshold levels when a fault is detected. For example, if manufacturers were not 

required to adjust the IRAF for a malfunctioning oxidation catalyst when calibrating the 

oxidation catalyst monitor, the manufacturer would likely be able to calibrate the system 

to only detect a fault when an oxidation catalyst was completely missing since the 

impact of the catalyst on emissions during non-regeneration is generally very small. 

However, during a regeneration event, where emission levels can be 10 or more times 

above the emission standard with a properly operating system, a missing catalyst can 

cause those emissions to be substantially higher still. One manufacturer reported to 

ARB that emissions were so high during a regeneration event with a malfunctioning 

catalyst that they were unable to measure the results in their emission test cell. The 

manufacturers’ suggested approaches of applying the baseline IRAFs and/or not taking 

into account the higher emissions would lead to a much higher emission level in the real 

world before a malfunctioning catalyst would be detected. 

After further discussions with engine manufacturers, the manufacturers have generally 

agreed to the need to account for IRAFs when calibrating malfunction thresholds, but 

have proposed language that imposes substantial limitations on what is required of 

manufacturers, attempts to define what data is good enough and acceptable for 

approval, and sets timelines for approval of a manufacturer’s IRAFs. Specifically, 

manufacturers proposed that the number of emission threshold monitors for which they 

would be required to obtain new data to support the IRAF estimations be limited (e.g., 
12

maximum of two to four monitors), regardless of how many monitors actually impact 

need new IRAF estimations. Additionally, they proposed that ARB be required to 

approve the IRAFs at least six months before the manufacturer’s target approval date 

for the OBD system or one month after they submitted the IRAF estimations and data 

for review and approval, and proposed that they be allowed to carry-over the IRAF 

estimations for up to three model years if errors were found in the estimation between 

the time of IRAF approval and the target OBD approval date. Staff does not believe any 

of the proposed modifications are appropriate and the manufacturers concerns are 

unfounded. As noted above, there are many aspects of emission regulations and 

compliance (and engine design, for that matter) that rely on manufacturers using sound 

engineering judgment. Further, the OBD staff has a demonstrated history of working 

with manufacturers for well over 10 years and the OBD program could not be where it is 

now if the staff was unreasonable with manufacturers on the eve of certification or could 

not reach common ground on what constitutes good engineering judgment. Artificially 

limiting the number of monitors for which a modified IRAF needs to be calculated when 

it is known that other monitors definitively adversely effect emissions in-use is also 

inappropriate. Manufacturers that define robust emission control solutions that are 

tolerant of faults will have fewer monitors that affect IRAFs while those that define less 

robust solutions may have more adverse interactions when components deteriorate. 

Limiting the number of monitors that have to be accounted for would reward those with 

inferior design solutions and result in higher in-use emissions when faults occur relative 

to those that design robust solutions. 

B. DIESEL FUEL SYSTEM MONITORING 

The regulation currently requires diesel manufacturers to continuously monitor for fuel 

system pressure control malfunctions. While some manufacturers have implemented 

common rail fuel systems, which can readily be monitored continuously for pressure 

malfunctions, others have expressed concerns that fuel pressure monitoring cannot be 

done continuously for non-common rail systems such as electronically controlled, 

mechanically actuated, unit injector systems . Based on the current design of the unit 

injector system, where fuel pressure is generated within each individual injector as 

opposed to via a high-pressure fuel pump as used in a common-rail system, the only 

method identified by the manufacturers to continuously monitor the fuel pressure would 

be to add a pressure sensor in each injector, which may not be a practical solution. 

Manufacturers contend there are no other viable solutions for continuous fuel pressure 

monitoring for unit injector systems. Manufacturers indicate, however, that they can 

monitor for fuel pressure faults by running an intrusive monitor once per trip under 

constrained conditions and believe such a monitor will be able to robustly detect all 

faults that would affect fuel pressure. Accordingly, manufacturers have asked ARB to 

change the regulation to only require monitoring to be conducted once per trip on noncommon rail systems. 

It is important to achieve proper fuel pressure in a diesel engine to maintain low 

emission levels. Continuous monitoring of the fuel pressure would ensure that if there 

was a problem, even it if only affected a portion of the engine operating conditions or if it 
13

had a varying impact (e.g., a big impact in some regions and a small impact in other 

regions), it would reliably get detected as long as operation in impacted regions was 

encountered. Conversely, with a once-per-trip monitor that only runs under a subset of 

engine operating conditions, only faults that impact the region where monitoring occurs 

will be reliably detected. 

However, ARB does agree that it would be very difficult, if possible, to continuously 

monitor the fuel pressure on unit injector systems or fuel systems that achieve injection 

fuel pressure within the injector or increase pressure within the injector (e.g. in the 

injector of an amplified common rail system) given their current design, and is thus 

proposing to not require continuous fuel pressure monitoring for these systems. Proper 

fuel pressure, however, is still critical for emissions and staff is concerned about 

different faults that may only impact specific regions of the engine operating conditions. 

As a compromise, staff is proposing a change that would allow once per trip monitoring 

of fuel pressure, but manufacturers would be required to demonstrate that the 

diagnostic (or diagnostics) can detect all failure modes which would lead to a fuel 

pressure problem within the entire range of engine operating conditions and before 

emissions exceed the OBD malfunction thresholds. A manufacturer would be required 

to submit details of their system and a failure analysis, such as a failure mode and 

effects analysis, identifying all possible failure modes and the effect each has on fuel 

pressure across the entire range of engine operating conditions. If different faults can 

cause pressure problems in exclusive regions (e.g., some only affect idle and some only 

affect off-idle), the manufacturer would be required to implement more than one 

diagnostic or enable the diagnostic in various operating conditions to cover the regions 

where faults could occur and use logic to ensure such faults are robustly detected. 

In addition to the above proposal, based on discussions with some manufacturers 

working on their fuel pressure control monitors, ARB has identified an area where 

further clarification would be beneficial. Specifically, manufacturers have asked 

questions about whether they should be using a single injector fault or a fault that 

equally affects all cylinders when calibrating the fuel pressure, quantity, and timing 

monitors to the OBD thresholds. Staff generally tries to pick a reasonable compromise 

between calibrating for all possible combinations of failures and a manageable number 

of combinations. Therefore, staff is proposing that for fuel pressure, quantity, and timing 

monitoring for systems that have single component failures which could affect a single 

injector (e.g., systems that build injection pressure within the injector that could have a 

single component pressure fault caused by the injector itself), manufacturers would be 

responsible for calibrating for both a single cylinder fault that causes the system to 

reach the malfunction criterion as well as a fault that equally affects all cylinders such 

that the malfunction criterion is reached starting in the 2013 model year. Staff believes 

this represents reasonable coverage for failures in use, be it a gradual deterioration or 

fault that affects all cylinders virtually equally or a more severe degradation or 

malfunction of a single injector that by itself causes such an emission increase. For 

systems that achieve injection pressure outside of the injector (e.g., common-rail 

systems), staff is proposing that for fuel quantity and timing monitoring, manufacturers 

would be required to calibrate for both a single cylinder fault and a fault that equally 
14

affects all cylinders, while for fuel pressure monitoring, manufacturers would only be 

required to calibrate for a fault that equally affects all cylinders. Staff’s rationale for the 

difference in fuel pressure monitoring is that systems like a common-rail system achieve 

injection pressure independent of the individual injectors and are unlikely to have a 

pressure fault affecting a single cylinder (but are still susceptible to quantity or timing 

faults that would affect a single cylinder or all cylinders equally). 

Staff is also proposing modifications to the MIL illumination and fault code storage 

protocol for fuel pressure control monitoring that are similar to the current requirements 

for gasoline fuel system monitoring. Specifically, the regulation would require fault 

detection to be more robust to failures that only occur within specific operating 

conditions by using similar conditions for maturing and clearing of faults. The use of 

similar conditions, which include engine speed, load, and warm-up status, provides for 

more consistent detection of faults that are routinely present in some operation 

conditions (e.g., high load) but are not present in others (e.g., idle). Manufacturers have 

indicated that they are controlling fuel pressure to substantially different levels during 

various engine operating conditions and staff is concerned that, as a result, faults are 

more likely to have inconsistent impacts across the engine speed and load map. 

Absent the use of similar conditions, a fault that is present every time high load 

conditions are encountered and absent every time idle is encountered could go for 

extended periods of time where the fault is detected and subsequently erased based 

solely on driver behavior. Similar conditions would only allow such a fault to be matured 

or erased under high load conditions and provide for more consistent detection. These 

modifications would apply to 2013 and subsequent model year engines. 

C. DIESEL EXHAUST GAS RECIRCULATION (EGR) SYSTEM MONITORING 

Staff is proposing amendments to the monitoring requirements that would clarify the 

requirements for various types of EGR systems. Currently, the monitoring requirements 

were written with the premise that the system would have direct feedback-control of 

EGR flow, as staff had believed that almost all manufacturers would use such systems. 

However, based on discussions with manufacturers as they review their plans for 2010 

and later engines, the monitoring requirements needed to be modified to account for a 

broader range of systems. Examples include control systems that technically use 

closed-loop control of other parameters such as fresh air flow or cylinder intake air 

concentration and control EGR flow to achieve the desired target instead of direct 

closed loop control of EGR flow. As detection of emission-related faults of these 

systems is important, regardless of whether or not they are directly feedback controlled, 

staff proposed amendments to the malfunction criteria for these monitors to indicate a 

fault tied to the “expected” EGR flow, rather than solely referring to the “commanded” 

EGR flow. 

Staff is also proposing amendments regarding EGR catalysts. Several manufacturers 

have implemented or proposed configurations which utilize a dedicated catalyst in the 

EGR system to convert hydrocarbons or soluble organic fractions (SOFs) prior to the 

exhaust gas being routed through the EGR cooler or valve. Manufacturers have 
15

indicated this catalyst reduces fouling of the cooler and/or valve, thereby prolonging the 

durability and performance of the EGR system. While manufacturers have argued that 

back to back tests comparing the emissions of a system with and without such a 

catalyst will show no measurable emission increase, they have acknowledged that a 

malfunction of the catalyst will eventually lead to higher emissions as the cooler and/or 

valve become fouled, reducing the effectiveness of the cooler or restricting flow through 

the system. Eventually, such fouling will cause an EGR cooler or flow fault to be 

detected but it is unclear how long higher emissions may be present or how much more 

rapidly a failed catalyst will cause subsequent failure of the cooler or valve. To avoid 

these excess emissions, the proposed amendments would require monitoring of EGR 

catalysts beginning with the 2013 model year. Staff believes that the current monitoring 

requirements would already require monitoring of this catalyst under the ‘other emission 

control’ section but discussions with manufacturers have indicated that this technology 

may also be phased out in the next few years as manufacturers determine such a part 

is not necessary. While it has not generally been acceptable to add an emission control 

component and have it be unmonitored, staff believes a deviation from policy until the 

2013 model year is appropriate for several reasons. Such reasons include failure of the 

catalyst does not immediately lead to an emission increase but rather a more rapid 

deterioration of another emission component, the other emission component (EGR 

cooler and/or EGR valve) is monitored and will eventually set a fault once its 

performance is compromised, and the component appears to be used by very few 

manufacturers in the interim but will not likely be used long term. Most manufacturers 

have systems that do not use this component and either do without it altogether, or in 

some limited cases, use the normal catalyst and/or PM filter in the exhaust to perform 

this function by putting the inlet to the EGR system further down the exhaust stream and 

after the catalyst or PM filter. In cases where such designs prevail, the additional 

leadtime until 2013 will allow manufacturers to transition to such designs. 

Additional proposed changes to the EGR system monitoring requirements are 

discussed under section II.T. (Emission Control Strategies) below. 

D. DIESEL BOOST PRESSURE CONTROL SYSTEM MONITORING 

For diesel boost pressure control systems, staff is proposing changes to account for 

systems that are not equipped with variable geometry turbochargers (VGT) systems. 

Currently, only VGT systems are monitored for slow response failures (e.g., 

malfunctions that cause the VGT itself to take longer than expected to achieve the 

desired VGT position.). Discussions with manufacturers have identified that 

malfunctions that cause the system to take longer to achieve desired boost levels can 

affect emissions, regardless of the boost hardware architecture. Accordingly, staff is 

broadening the slow response malfunction criteria to apply to all boost systems, 

regardless of whether the system uses a VGT, and to make the criteria based on the 

response of the system to achieve the actual boost rather than on the response of one 

of the individual actuators to achieve a certain position. It should be noted that most 

manufacturers have indicated that slow response boost failures rarely could get bad 

enough that they would cause emissions to exceed the OBD threshold and thus, are 
16

subject only to a functional monitor. Further, most manufacturers are able to 

demonstrate that the under and over boost monitors meet the definition of a functional 

check for slow response by demonstrating they detect induced response failures with 

such diagnostics before emissions are too high. This proposed requirement, however, 

will ensure that any manufacturer who has a larger sensitivity to slow response boost 

malfunctions will be required to detect faults before emissions exceed the prescribed 

threshold levels.

Similar to the proposed amendments for EGR system monitoring, staff is also proposing 

amendments to the monitoring requirements that would attempt to clarify the 

requirements for various types of boost pressure control systems. Currently, the 

monitoring requirements were written with the premise that all systems would have 

direct feedback-control of boost pressure, as staff had believed that almost all 

manufacturers would use such systems. However, based on discussions with 

manufacturers as they review their plans for 2010 and later engines, the monitoring 

requirements needed to be modified to account for a broader range of systems. 

Examples include open loop boost pressure systems or control systems that technically 

use closed-loop control of other parameters such as fresh air flow or cylinder intake air 

concentration and control boost pressure to achieve the desired target instead of direct 

closed loop control of boost pressure. As detection of emission-related faults of these 

systems is important, regardless of whether or not they are directly feedback controlled, 

staff proposed amendments to the malfunction criteria for these monitors to indicate a 

fault tied to the “expected” boost pressure, rather than solely referring to the 

“commanded” boost pressure. 

Additional proposed changes to the boost pressure control system monitoring 

requirements are discussed under section II.T. (Emission Control Strategies) below. 

E. DIESEL NON-METHANE HYDROCARBON (NMHC) CONVERTING CATALYST 

MONITORING 

The regulation currently requires diesel engine manufacturers to design the OBD 

system to detect an NMHC catalyst malfunction when the catalyst conversion capability 

decreases to the point that NMHC emissions exceed 2.5 times the applicable standard 

for 2010 model year engines. However, if a catalyst malfunction does not result in 

emissions exceeding this threshold, the regulation allows the manufacturer to detect a 

malfunction when the catalyst has no detectable amount of NMHC conversion 

capability. Monitoring of NMHC conversion performance is also required for catalyzed 

PM filters, with monitoring similarly required at 2.5 times the applicable standard or, if 

emissions cannot exceed that level, for complete failure of the NMHC-catalyzing 

function. The regulation also currently requires manufacturers to monitor the NMHC 

catalyst for its ability to perform other emission-related functions. Specifically, 

monitoring is required to ensure that the catalyst performance is sufficient to provide an 

exotherm necessary for PM filter regeneration and, if applicable, to generate a desired 

feedgas (e.g., nitrogen dioxide (NO2)) to promote better performance in a downstream 
17

aftertreatment component (e.g., for higher NOx conversion efficiency in a selective 

catalytic reduction (SCR) system). 

With respect to NMHC-converting catalyst monitoring, engine manufacturers are 

concerned that total failure of NMHC catalysts will push emissions over the threshold 

and force them to implement threshold monitors. Furthermore, they do not believe that 

there is any monitoring technology that can robustly detect anything other than a 

completely failed NMHC catalyst. Lastly, they believe the current requirement of 

determining and applying an adjusted IRAF when determining the emission level of a 

malfunctioning catalyst exacerbates this problem by requiring them to detect a less 

degraded catalyst. Accordingly, manufacturers have asked ARB to raise the threshold 

to 4.0 times the NMHC standard and remove the requirement to develop and apply an 

adjusted IRAF so that manufacturers would very likely only have to implement functional 

monitors. 

Staff, however, does not agree with the manufacturers’ assessment of the current 

monitoring technology, and is not proposing any changes to the current malfunction 

thresholds. Staff believes that there are currently feasible methods to perform threshold 

monitoring of the NMHC catalyst. For discerning a good from bad catalyst, 

manufacturers have primarily focused on whether the catalyst can generate a sufficient 

exotherm and have concluded that a catalyst is either able to produce a sufficient 

exotherm (and thus, is perfectly adequate) or it is unable to produce a sufficient 

exotherm (and thus, is completely failed). Manufacturers have concluded from such 

analysis that there is no level of catalyst degradation between perfectly adequate and 

completely failed and that an exotherm monitor can only discern those two states. 

However, in talking with suppliers and individual manufacturers, catalysts do indeed 

have intermediate levels of deterioration that cause increases in light-off temperature 

and lower conversion efficiencies. By looking more closely at the catalyst behavior 

during active regeneration (e.g., by investigating how much time and/or fuel is needed 

to generate an exotherm, tracking the actual temperature rise from the exotherm versus 

the expected, and using better temperature sensors), manufacturers may be able to 

better determine the characteristics exhibited as an NMHC catalyst degrades (even if it 

is still capable of eventually getting to a high enough exotherm to achieve regeneration 

of the PM filter). As an alternate approach, there are at least two light-duty 

manufacturers that are planning on monitoring the catalyst during a cold start. Often 

combined with an accelerated catalyst light-off strategy similar in concept to what many 

gasoline manufacturers use, this monitoring approach tracks the light-off and/or 

temperature rise characteristics to evaluate the catalyst during intrusive actions 

intended to bring the catalyst up to the desired temperature quickly after a cold start. 

Along with improved monitoring approaches, manufacturers have the ability to reduce 

the emission impact associated with a malfunctioning catalyst. For example, engine-out 

NMHC emission levels have a direct impact on the emission levels from a 

malfunctioning NMHC catalyst. The lower the engine-out emissions, the lower the 

tailpipe emissions for a given level of degraded catalyst. In addition to looking into 

reducing engine-out emissions, manufacturers can also look into reducing emissions 
18

during a regeneration event. Manufacturers have generally indicated that without an 

NMHC catalyst, baseline tailpipe NMHC emissions are very close to the NMHC 

standard (still under in some cases, slightly over in others) and nowhere near the OBD 

malfunction criteria of 2.5 times the standard. However, when an active regeneration of 

the PM filter occurs and the NMHC catalyst is degraded or non-functional, emissions 

can be very high. Accordingly, when defining the level of degraded catalyst that 

reaches the OBD malfunction threshold (e.g., 2.5 times the standard), the emissions 

during the PM filter regeneration are the primary emission contributors. Because 

manufacturers are required to account for changes in regeneration emissions in the 

form of an adjusted IRAF, the ‘threshold’ NMHC catalyst is almost exclusively defined 

by the impact on regeneration emissions. The more infrequent the regenerations or the 

smaller the emission increase during regeneration, the more tolerant the system is of a 

degraded catalyst before the OBD malfunction criterion is reached. Again, 

manufacturers have the ability to directly reduce the emission impact associated with a 

malfunctioning catalyst by minimizing emissions during a PM filter regeneration event. 

Manufacturers that have less refined control strategies for regeneration (e.g., injecting 

fixed quantities of fuel regardless of the observed temperature rise/reaction of the 

catalyst) will have higher associated emissions while those that more closely regulate 

the regeneration event can take quicker action to terminate or reduce fueling when the 

expected reaction does not occur. At least two manufacturers have taken this approach 

to be able to meet a lower tailpipe emission level with a degraded catalyst that their 

catalyst monitor is able to identify as a malfunction. 

Similar to their argument for NMHC converting catalyst monitoring, manufacturers have 

also asked for the 2010 model year threshold to be raised from 2.5 to 4.0 times the 

standard for catalyzed PM filter NMHC conversion monitoring to ensure that only a 

functional check would be needed. Staff has been talking with suppliers and individual 

manufacturers regarding the use and monitoring of catalyzed PM filters. While there is 

no consistent trend in industry, many are looking at catalyzed PM filters and 

acknowledging that the incremental cost of a catalyzed PM filter is not insignificant. As 

such, those that are using catalyzed PM filters are doing so because they are realizing 

actual benefits. Most have stated that it simply ‘helps out’ with regeneration without 

being able to quantify the actual impact. Discussions with others indicate that the 

catalyzed coating leads to higher levels of passive regeneration at lower exhaust 

temperatures, helps convert hydrocarbon (HC) and carbon monoxide created during an 

active regeneration, and can help generate NO2 feedgas for downstream SCR systems. 

Again, given the importance of these tasks and manufacturers’ acknowledgment that 

they are spending extra money to have these functions, it is appropriate that monitoring 

be required. If the reasoning behind having the catalyzed coating is the impact on 

passive regeneration, then this function should be able to be monitored by looking at 

regeneration frequency or rate of soot loading increase under conditions where high 

levels of passive regeneration are expected. At least one heavy-duty manufacturer 

believes that there will be a detectable difference in active regeneration frequency 

between a PM filter with and without the catalyzed coating and is designing their 2010 

monitor to detect this. However, staff acknowledges that manufacturers are scrambling 

to finish their systems for the 2010 model year and many are behind schedule on OBD 
19

development because the emission calibrations are not finalized. The success of the 

monitoring approaches outlined above may be highly dependent on the actual catalyst 

configuration, significance of the catalyst loading on the PM filter, and regeneration 

strategy (especially reliance on high levels of passive regeneration). Accordingly, staff 

is proposing to delay the monitoring requirements of the catalyst function of catalyzed 

PM filters until the 2013 model year to give manufacturers more time to refine their 

systems, optimize regeneration strategies, and better investigate the impacts of the 

catalyzed PM filter. 

For monitoring of the NMHC catalyst’s ability to generate a desired feedgas used to 

improve performance of a downstream aftertreatment component, manufacturers have 

indicated that insufficient knowledge exists about what property of the catalyst causes 

the desired feedgas and thus have argued that there is no feasible or known method to 

verify that such function is still properly operating. Further, manufacturers have 

indicated that the impact of such a failure is decreased efficiency of the downstream 

aftertreatment component (e.g., SCR system). Accordingly, manufacturers have asked 

ARB to eliminate the requirement to directly verify the NMHC catalyst generates 

sufficient feedgas for other components and to instead rely on monitoring of the 

downstream component (e.g., SCR system) to detect a failure if the impact is large 

enough to cause emissions to exceed the OBD malfunction criteria. 

However, the manufacturer’s claim that they have insufficient knowledge about the 

mechanism of the catalyst that creates the desirable feedgas is not supported. Staff 

has met with various suppliers to the manufacturers who have indicated that they 

understand the properties of the catalyst extremely well and alter specific components 

to achieve the feedgas generation the manufacturers are asking for. In most cases, the 

catalyst is being used to oxidize nitric oxide (NO) to NO2 to increase the relative NO2

levels, which can help oxidize soot in a PM filter (leading to higher levels of passive 

regeneration of the PM filter or more effective active regenerations) and, perhaps more 

importantly, can improve NOx conversion efficiency in an SCR system. Using a catalyst 

to generate such a feedgas is not that new of a technology as there are even retrofit 

devices certified by ARB for use on older model year diesel engines that take 

advantage of these catalyst properties. Further, discussions with suppliers indicate that 

this catalyst function is likely to be the first to deteriorate and would not be accompanied 

with a substantial change in the catalyst’s HC conversion efficiency or ability to generate 

an exotherm. As such, staff believes that being able to determine whether the catalyst 

is still performing this function is essential and is concerned that a failure of this function 

will not likely be detected by the NMHC catalyst monitoring strategies mentioned above. 

The manufacturers’ proposal would require the failure of this function to be detected 

only if it alone causes the SCR system conversion efficiency to drop so far that it 

exceeds the OBD thresholds for the SCR system (approximately 2.5 to 3.0 times the 

standard). Staff does not believe this is an acceptable solution because, while failure of 

this NMHC catalyst property will lead to decreased SCR NOx conversion efficiency and 

likely higher tailpipe NOx levels, it is not expected to cause a large enough impact to 

exceed the SCR catalyst threshold. Under this scenario, this NMHC catalyst property 
20

could be completely non-functional, tailpipe emissions will be increased by some 

amount, and the system will continue to operate without any indication to the operator 

that a malfunction has occurred. Further, if the SCR system itself eventually degraded 

enough that the combined impact of the upstream catalyst and the SCR catalyst 

efficiency exceeded the threshold and illuminated the MIL, technicians would likely only 

replace the SCR catalyst components to extinguish the MIL. This repair sequence 

would result in essentially a partial repair—emissions would never be returned to the 

levels they were at when the upstream catalyst was also properly functioning. At this 

time, the most promising monitoring technology for verifying this function of the catalyst 

is some form of an SCR system NOx conversion efficiency evaluation to detect lower 

than expected conversion efficiencies in the absence of the proper feedgas. One 

heavy-duty manufacturer has indicated its intent to detect such a malfunction by 

evaluating the NOx conversion efficiency across the SCR system during specific 

operating conditions. If successful, this manufacturer would be able to detect a fault 

when this property of the NMHC catalyst was gone but the SCR system was still 

operating properly. 

If the catalyst’s ability to generate NO2 also has a significant impact on PM filter 

regeneration, another possible monitoring approach would involve evaluation of PM 

filter regeneration characteristics. In cases where the catalyst is used to promote high 

levels of passive regeneration, manufacturers may be able to identify a malfunction 

when backpressure or other soot loading measures indicate much higher loading than 

expected if passive regeneration was working correctly. Given the importance of proper 

feedgas generation to PM filter regeneration and/or proper SCR system NOx 

conversion efficiency and the information from suppliers that this catalyst property will 

likely deteriorate first, staff is not proposing to adopt the changes suggested by the 

manufacturers. However, staff acknowledges that the monitoring approach of looking at 

SCR system conversion efficiency does ultimately rely on SCR system configuration 

and NOx sensor accuracy and is concerned that the monitor resolution may be 

insufficient in the 2010 timeframe. Additionally, for monitoring approaches looking at 

PM filter regeneration, the ability to discern properly operating systems from 

malfunctioning systems may be highly dependent on the manufacturer’s catalyst 

configuration and regeneration strategy. Accordingly, staff is proposing to delay 

functional monitoring of proper feedgas generation until the 2013 model year. This 

additional leadtime should provide manufacturers the ability to better understand the 

catalyst properties used to generate the feedgas, optimize and refine catalyst 

configurations and PM filter regeneration strategies, and gain experience with NOx 

sensors and SCR systems to investigate areas where feedgas generation is expected 

to be high or have a substantial impact on conversion efficiency and focus on those 

regions for possible monitoring approaches. 

Additionally, to be consistent with the recent OBD II regulation update, staff is proposing 

to add specific language detailing the requirements for manufacturers to functionally 

monitor an NMHC-converting catalyst used to prevent ammonia slip downstream of an 

SCR system. Under the current regulation, all NMHC-converting catalysts have to be 

monitored but specific details were only provided for the most common types of 
21

catalysts such as catalysts used to generate an exotherm for PM filter regeneration or 

catalyzed PM filters. As has been traditionally done in the OBD regulatory updates, as 

new emission control technologies become more defined, staff adds more specific 

language to clarify the requirements that apply to that technology. This often removes 

the need for manufacturers to submit a monitoring plan (e.g., as is required in the ‘other 

emission controls’ section) and gives clear direction to manufacturers as to what is 

expected. 

Staff is also proposing modifications to the emission thresholds manufacturers are 

required to calibrate NMHC catalyst monitors to. Currently, the HD OBD regulation 

requires manufacturers to detect an NMHC-converting catalyst malfunction before 

emissions exceed a specific NMHC emission threshold because staff thought that, in 

every case, NMHC emissions would be the dominant pollutant affected by a degraded 

NMHC catalyst system. However, as manufacturers finalize their designs for 2010, staff 

has observed a tremendous amount of variation in emission control solutions including 

many cases where the interactions of various emission controls and strategies cause 

previously unanticipated results. In some cases, a malfunction of a NMHC emission 

control component has caused a rather large increase in NOx emissions. As an 

example, a degraded NMHC catalyst can lead to more frequent or extended PM filter 

regeneration events. And, some manufacturers disable NOx controls during a PM filter 

regeneration event. Accordingly, more frequent and longer PM filter regeneration 

events lead to more operation with NOx controls disabled and significantly higher NOx 

emission levels. Thus, even though the root failure is of a component intended to 

reduce NMHC emissions, the in-use emissions impact may actually be dominated by 

NOx emissions. As the intent of OBD is to ensure malfunctions of emission 

components are detected before tailpipe emission levels of any criteria pollutant are too 

high, it would be inappropriate to allow excess emissions of one pollutant solely 

because the malfunctioning emission control is ‘primarily’ intended to control another 

pollutant. Thus, staff is proposing to require manufacturers to detect catalyst 

malfunctions before a specific NOx threshold is exceeded in addition to the currentlyrequired NMHC threshold. Specifically, starting with the 2013 model year, 

manufacturers would be required to detect a fault before NMHC emissions exceeded 

2.0 times the applicable standard or NOx emissions exceeded the applicable NOx 

standard by more than 0.2 g/bhp-hr, whichever occurs first. It is still expected in the 

vast majority of cases that the NMHC emission threshold will be the dominant factor 

when detecting malfunctioning NMHC converting catalyst systems. However, in the 

rare case that a manufacturer’s particular design has other interactions or synergistic 

effects that cause NOx emissions to substantially increase, this change will ensure that 

a fault is detected before NOx emissions are substantially higher. 

F. DIESEL OXIDES OF NITROGEN (NOx) CONVERTING CATALYST MONITORING 

The regulation currently requires diesel manufacturers to monitor the NOx catalyst(s) for 

proper conversion capability and to detect a catalyst malfunction before NOx emissions 

exceed the applicable NOx standard by more than 0.3 g/bhp-hr for the 2010 model 

year. The regulation also requires engines equipped with SCR systems or other 
22

catalyst systems that utilize an active/intrusive reductant injection to monitor these 

systems for proper performance. Manufacturers have expressed concern that the 

current NOx sensor technology will not provide the accuracy at low concentration levels 

necessary for OBD monitoring of the SCR catalyst. According to manufacturers, a fresh 

production NOx sensor currently has a tolerance of +/- 6 parts-per-million (ppm) while 

an aged NOx sensor currently has a tolerance of +/- 15 ppm. Further, they indicated 

that the average NOx emissions over the federal test procedure (FTP) transient cycle 

would have to be roughly 20 ppm to meet the 0.2 g/bhp-hr NOx tailpipe standards for 

2010 while concentrations would be roughly 50 ppm at the OBD threshold of 0.3 g/bhphr above the standard. Therefore, using an aged +/- 15 ppm NOx sensor to robustly 

discern a properly operating system at 20 ppm (that could read as high as 35 ppm) from 

a malfunctioning system at 50 ppm (that could read as low as 35 ppm) would not 

provide sufficient separation to be feasible. Based upon a paper assessment of the 

NOx sensor capability as an SCR monitoring device, manufacturers have indicated that 

to meet the 2010 model year requirements, an aged NOx sensor’s accuracy would need 

to be about +/- 5 ppm, and that a sensor with such an accuracy will not be available in 

time to meet the 2010 requirements. Thus, manufacturers have asked staff to relax the 

OBD malfunction threshold for the 2010 model year to a level of 0.6 g/bhp-hr (or 60 

ppm) above the NOx tailpipe standard instead of 0.3 g/bhp-hr (or 30 ppm) above the 

NOx tailpipe standard. 

ARB is not convinced that the current NOx sensor capability necessitates raising the 

SCR catalyst monitor threshold as high as manufacturers have requested. 

Manufacturers have not provided engineering test data from actual calibrations to 

support their assessment of SCR monitoring capability, even after staff sent specific 

requests for this supporting data, and have based their claims primarily on a paper 

assessment using ‘average’ concentrations over an entire emission test. Average 

concentrations generally are not very helpful in determining technical feasibility as an 

SCR catalyst diagnostic would typically be constrained to run under very specific 

operating conditions where the best separation between good and bad exists. It is 

expected that a degraded SCR catalyst would not lead to universally higher NOx 

emissions throughout the emission test but rather to larger increases during very 

specific conditions (e.g., accelerations, higher load cruises) and actual concentrations 

are only relevant during those specific conditions. Based on very limited data received, 

it appears that degraded catalysts do indeed affect emissions most in specific operating 

conditions where expected NOx concentrations are higher and current sensor accuracy 

is less of an issue. ARB does, however, believe that some interim relief is needed to 

address some remaining uncertainties with NOx sensor durability and separation at high 

mileage and is proposing to raise the OBD malfunction threshold to 0.4 g/bhp-hr (or 40 

ppm) above the NOx tailpipe standard for the 2010 through 2012 model years 

(concurrently, this same threshold will also apply for 2010 through 2012 model year 

NOx sensor performance monitoring). Based on the manufacturers’ over-simplified 

analysis, this would require discerning a 20 ppm system (reading as high as 35 ppm) 

from a 60 ppm system (reading as low as 45 ppm). As explained below, manufacturers 

should be able to be more selective when monitoring is conducted to provide even more 

separation than this. 
23

In addition to improved NOx sensors not being available for 2010, some manufacturers 

have argued that the OBD malfunction threshold for SCR catalyst monitoring should be 

raised more than the proposed 0.4 g/bhp-hr above the NOx tailpipe standard due to the 

effects of the surrounding exhaust heat on the electronic NOx sensor module tolerance. 

Manufacturers have stated that the sensor supplier will only warrant an accuracy of +/- 

18 ppm when NOx sensor module temperatures exceed an upper limit. Staff has 

considered this point but does not agree that the OBD malfunction threshold for SCR 

catalyst monitoring should be raised any higher for this reason. Staff believes most 

manufacturers will be able to design or configure an aftertreatment system to avoid 

exposing the electronic NOx sensor module to such excessive temperatures under the 

vast majority of vehicle operation and to keep the NOx sensor module within the 

supplier’s specifications. During rare extreme conditions when high temperatures 

cannot be avoided (e.g. particulate matter filter regeneration), manufacturers can 

disable the SCR catalyst monitor in these limited regions by using parameters within the 

OBD system to identify these extreme conditions. Staff considers it unacceptable to 

design a system that encounters these excessive temperatures in the majority of vehicle 

operation thereby preventing the SCR catalyst monitor from having a reasonable in-use 

monitoring frequency. 

Despite some manufacturers’ claims that improved NOx sensors are needed to monitor 

the SCR system, other manufacturers have identified different monitoring strategies that 

utilize current NOx sensor technology to successfully monitor the SCR catalyst. Most of 

these strategies rely upon monitoring the SCR catalyst only under normally occurring 

conditions where NOx concentrations are higher. Staff has been shown data indicating 

that sustained periods of operation above the ‘average’ 20 ppm NOx concentrations 

with a properly functioning SCR system are occurring during both the FTP transient 

cycle and the supplemental emission test (SET) cycle on engines designed to meet the 

2010 NOx standard. Some manufacturers have provided data showing sustained 

periods of operation above 60 ppm NOx concentrations that naturally occur during the 

SET cycle, usually during transient conditions from high load to lower load conditions. 

At higher NOx concentrations (greater than 60 ppm), the accuracy of the NOx sensor is 

not as critical (e.g., an accuracy of +/- 15 ppm has less relative influence if you are 

measuring a concentration of 60 ppm instead of 20 ppm for good system) and can 

provide sufficient separation between a good catalyst and a threshold catalyst. 

Manufacturers could design their SCR monitors to run when these higher NOx 

concentrations are either occurring naturally or created intrusively. Staff has data from 

a manufacturer that demonstrates the ability to intrusively increase the NOx output of an 

engine by decreasing exhaust gas recirculation (EGR) under specific engine operating 

conditions to run other emission-related diagnostics. Therefore, staff believes it is 

feasible to use the concept of intrusively increasing engine out NOx emissions and to 

calibrate an SCR catalyst monitor that will both be able to monitor the catalyst with 

currently available NOx sensors and be within the proposed OBD thresholds. An 

example of how this could be done is by defining specific engine operating conditions 

and intrusively reducing EGR flow to temporarily increase inlet (and outlet) SCR catalyst 
24

NOx concentrations. While intrusive diagnostics that increase emissions are generally 

avoided, the negative emission impact of intentionally increasing NOx to the SCR 

catalyst could be minimized by appropriately increasing reductant injection dosing to the 

SCR catalyst such that properly operating systems still result in low SCR outlet NOx 

concentrations while malfunctioning systems would show larger relative outlet levels 

due to the decreased conversion efficiency and increased inlet levels. 

In addition to monitoring only at higher NOx levels, alternative methods of monitoring 

the SCR catalyst conversion efficiency may be available. Staff believes it is feasible to 

intrusively perform SCR catalyst monitoring by temporarily disabling or altering 

reductant injection to optimize conditions for catalyst monitoring. Manufacturers have 

argued that they cannot afford to perform such intrusive strategies because of the 

negative emission consequence of reduced/disabled reductant injection. However, staff 

has data from an SCR system showing reductant injection being completely disabled 

temporarily with no adverse emission impact due to the reductant storage properties of 

an SCR catalyst. This data suggests that there may be a possibility to infer SCR 

catalyst NOx conversion efficiency by measuring reductant storage capability if the two 

parameters can be correlated. Such a strategy would require disabling the dosing and 

watching for a reaction in the rear NOx sensor. If the sensor saw an increase in NOx 

soon after disablement, it would indicate poor reductant storage (and potentially 

correlate to poor NOx conversion efficiency). If the sensor did not see an increase in 

NOx after some amount of time, the system could conclude the catalyst was working 

correctly and resume reductant delivery. This strategy offers the potential to avoid any 

negative emission consequence during monitoring of the SCR catalyst while the catalyst 

is good by terminating the monitor before any NOx breakthrough has occurred. 

Lastly, the HD OBD regulation requires manufacturers to detect a NOx converting 

catalyst malfunction before emissions exceed a specific NOx emission threshold. 

Originally, staff thought that, in every case, NOx emissions would be the dominant 

pollutant affected by a degraded NOx catalyst system such as SCR. However, as 

mentioned in section II.E. for NMHC converting catalysts, staff has observed a 

tremendous amount of variation in emission control solutions including many cases 

where the interactions of various emission controls and strategies cause previously 

unanticipated results. As the intent of OBD is to ensure malfunctions of emission 

components are detected before tailpipe emission levels of any criteria pollutant are too 

high, it would be inappropriate to allow excess emissions of one pollutant solely 

because the malfunctioning emission control is ‘primarily’ intended to control another 

pollutant. Thus, staff is proposing to add language to ensure that NOx converting 

catalyst malfunctions are detected before NOx or NMHC emissions, whichever happens 

first, exceed specified levels. It is still expected in the vast majority of cases that the 

NOx emission threshold will be the dominant factor when detecting malfunctioning NOx 

converting catalyst systems like SCR. However, in the rare case that a manufacturer’s 

particular design has other interactions or synergistic effects that cause NMHC 

emissions to substantially increase, this change will ensure that a fault is detected 

before NMHC emissions exceed 2.0 times the applicable standard. To ensure any 
25

manufacturer with such a rare interaction has sufficient leadtime to calibrate properly, 

the proposed NMHC threshold would not be applicable until the 2013 model year. 

G. DIESEL NOx ADSORBER MONITORING 

The HD OBD regulation currently requires manufacturers to detect NOx adsorber 

malfunctions before emissions exceeded a specific NOx threshold. Similar to the 

proposed NOx converting catalyst monitoring revisions mentioned above and for the 

same reasons, staff is also proposing to require manufacturers to detect NOx adsorber 

malfunctions before a specific NMHC threshold is exceeded in addition to the currentlyrequired NOx threshold. Specifically, starting with the 2013 model year, manufacturers 

would be required to detect a fault before NOx emissions exceeded the applicable NOx 

standard by more than 0.2 g/bhp-hr or NMHC emissions exceeded 2.0 times the 

applicable standard.

Additionally, staff is proposing language similar to what is currently required for NMHC 

and NOx converting catalyst monitoring regarding malfunction criteria determination 

with multiple adsorbers. Specifically, in order to determine the proper OBD malfunction 

threshold for the NOx adsorber, manufacturers would be required to progressively 

deteriorate or “age” the adsorber to the point where emissions exceed the malfunction 

threshold. The method used to age the adsorbers must be representative of real world 

adsorber deterioration under normal and malfunctioning operating conditions. For 

engines with aftertreatment systems that utilize multiple adsorbers, determining the 

OBD malfunction threshold becomes more complex since aging effects of the adsorber 

are dependent on many factors, including the locations of the adsorbers relative to the 

other aftertreatment technologies and the synergism between each component in the 

system. While a “one-size-fits-all” aging process that accurately represents every 

possible aftertreatment configuration is ideal, the diesel aftertreatment system designs 

are not yet at a level of stabilization (i.e., not yet limited in variation of configurations) to 

define such a process. Thus, until then, staff would require manufacturers to submit a 

system aging and monitoring plan to the Executive Officer for review and approval of 

the monitoring strategy, malfunction criteria, and aging process. Executive Officer 

approval would be based on the representativeness of the adsorber system aging to 

real world adsorber deterioration under normal and malfunctioning operating conditions, 

the effectiveness of the monitor to pinpoint the likely area of malfunction, and 

verification that each adsorber component is functioning as designed. 

H. DIESEL PARTICULATE MATTER (PM) FILTER MONITORING

The heavy-duty OBD regulation currently requires the OBD system to identify 

malfunctions of the PM filter when the filtering capability degrades to a level such that 

tailpipe emissions exceed a specific threshold. For the 2010 through 2015 model year 

engines, the threshold is the highest of the following thresholds: 0.05 g/bhp-hr as 

measured from an applicable emission test cycle (i.e., FTP or supplemental emission 

test (SET)) or the applicable standard plus 0.04 g/bhp-hr (e.g., 0.05 g/bhp-hr for a 

standard of 0.01 g/bhp-hr). 
26

Heavy-duty engine manufacturers have expressed concern that the current threshold is 

too stringent and is not technically feasible for the 2010 model year time frame. They 

contend that the current status of technology cannot support such a threshold. When 

ARB originally adopted the current requirement in 2005, staff proposed that improved 

differential pressure sensors and refined soot-loading models should allow 

manufacturers to comply with the above thresholds by the 2010 model year. 

Manufacturers insist that current differential pressure sensors cannot measure 

pressures with the accuracy necessary to comply with the required thresholds in the 

given timeframe and that there are a number of uncontrolled variables that affect the 

accuracy of soot-loading models, such as a “lack of rigid control of fuel specifications” 

and the increased usage of biodiesel fuels that cannot be accounted for in the models. 

Additionally, part-to-part variability of PM filters increases the uncertainty of the pressure 

sensor correlation with the emission threshold. In order to achieve the current emission 

thresholds for PM filter monitoring, manufacturers believe PM sensors are necessary. 

However, these sensors are not expected to be available in the 2010 time frame. 

ARB staff agrees that some relief is needed for these initial years of PM filter monitoring 

implementation based on discussions with manufacturers about their progress in 

meeting the monitoring requirements. Thus, staff is proposing to raise the PM filter 

threshold for the 2010 through the 2012 model year engines to 0.07 g/bhp-hr as 

measured from an applicable emission test cycle (i.e., FTP or SET) or the applicable 

standard plus 0.06 g/bhp-hr (e.g., 0.07 g/bhp-hr for a standard of 0.01 g/bhp-hr). Staff 

believes the increase of the emission threshold by up to 40 percent will sufficiently 

address manufacturers’ concerns on the technical feasibility of meeting the threshold. 

Two medium-duty diesel engines are already capable of detecting PM filter malfunctions 

below 0.07 g/bhp-hr and others are expected to meet these same levels soon. 

Additionally, two heavy-duty engine manufacturers have indicated that they are on track 

to detect malfunctions prior to PM emissions exceeding 0.05 g/bhp-hr but do not yet 

have final calibration data to conclusively demonstrate it. 

 

Additionally, heavy-duty diesel manufacturers will have the added knowledge gained 

from three years of equipping engines with PM filters prior to introducing monitors in 

2010 that comply with the 0.07 g/bhp-hr threshold. Staff projects that this additional 

experience should provide manufacturers the opportunity to further refine versions of 

the technology and components they currently use for the PM filter diagnostic such as 

soot loading models and differential pressure sensors. In general, the diagnostics 

typically involve a comparison of the expected differential pressure derived from the 

soot-loading model and the actual measured differential pressure sensor across the PM 

filter. If the measured differential pressure is too small compared to the modeled 

differential pressure, a malfunctioning PM filter can be determined. However, if the soot 

loading model and/or the differential pressure sensor are not accurate, it is difficult to 

discern a good PM filter from a bad one because the differential pressures for the good 

and bad filters would overlap. As a result, only higher thresholds can be monitored with 

a crude soot loading model. With improvements to soot loading models and differential 
27

pressure sensors, staff believes that most heavy-duty manufacturers will be able to 

reliably identify malfunctioning PM filters at the proposed 0.07 g/bhp-hr PM threshold in 

the 2010 timeframe. 

In addition to improving the monitoring stringency, more accurate soot loading models 

would allow manufacturers to operate their PM filter diagnostic more frequently than is 

currently possible with crude soot models. Under certain engine operating conditions 

such as driving with a clean PM filter (i.e., a PM filter clear of soot) or low exhaust flow 

rates, it may be difficult to discern a good PM filter from a bad PM filter, especially with a 

crude soot model. To compensate for the shortcomings of their soot models, some 

manufacturers have proposed monitoring the PM filter only under high speeds and 

loads and only during a limited manufacturer-specified period following a PM filter 

regeneration event. As a result, in-use monitoring frequency may be low for such 

strategies and may have difficulty complying with the in-use monitoring frequency 

requirements. However, if a more accurate soot loading model is utilized, monitoring 

can be achieved at a variety of PM soot loads, thereby increasing the monitoring 

frequency of the diagnostic and potentially improving the separation between a 

malfunctioning and good PM filter. Improvements to differential pressure sensors will 

also have a similar positive effect on PM filter monitoring. Therefore, further refinement 

of soot-loading models and differential pressure sensors would reduce much of the 

diagnostic measurement variation manufacturers are concerned about and allow 

monitoring at the proposed 0.07 g/bhp-hr level under a variety of operating conditions 

that are encountered frequently during in-use driving. 

Manufacturers can also directly impact the level of emissions with a malfunctioning PM 

filter by varying engine out emissions. Directionally, the lower the engine out PM 

emissions, the lower the tailpipe PM level will be when a fault is detected. Staff has 

seen great variance in the levels of engine out PM level from manufacturers as they 

each seek to optimize in different areas. Unfortunately, some manufacturers have 

chosen to optimize for other factors with little to no consideration on diagnostic 

monitoring capability and, as a result, those manufacturers are struggling. Other 

manufacturers that did include OBD capability or impacts in the final emission solution 

and calibration appear to be able to detect malfunctions at much lower PM levels. 

Other areas for improving the diagnostic’s accuracy include reducing the manufacturer 

tolerances in the engine, reducing the part-to-part variability of the backpressure 

characteristics of the PM filters, and correcting for the backpressure variations of PM 

filters caused by manufacturing tolerances. Generally, any improvements to aspects 

that reduce the variation of PM output of the engine or the backpressure characteristics 

of the PM filter would reduce diagnostic error. Manufacturers could demand tighter 

tolerances from their suppliers to reduce the variation in these parts to improve the 

accuracy of the diagnostic. While deviations in back pressure are probably not critical 

for the durability or trapping performance of the PM filter, they likely will be critical for 

diagnostic purposes. Sizing of the PM filter itself also plays a role in the backpressure 

levels and manufacturers are expected to still be gaining experience from the field to 

define the optimum characteristics to improve monitoring capability. 
28

Regarding manufacturer’s concerns on fuel specification variation and increased usage 

of biodiesel fuels causing uncertainty in the soot loading models, staff agrees that 

consistent fuel quality is an important aspect in ensuring accurate modeling of the soot 

loading. However, diesel fuel quality in the United States is consistent in quality and will 

deliver consistent performance on diesel vehicles. In order to sell diesel fuel, fuel 

producers must demonstrate that various constituents of their candidate fuel meet 

certain specifications, including sulfur content, aromatics, and lubricity, and that tailpipe 

emissions from using the fuel on a known engine do not exceed emissions of that 

emitted from a reference fuel on the same engine. Additionally, ARB has a fuel 

enforcement program where fuel inspectors conduct frequent, unannounced inspections 

of refineries, service stations, distribution and storage facilities, and other facilities to 

ensure California diesel fuel is of a consistent quality. Lastly, staff acknowledges that 

biodiesel fuels have been shown to reduce exhaust PM emissions and thereby affect 

the accuracy of soot loading models if its usage is unaccounted for. However, staff 

believes that biodiesel usage is still very small in California (less than 0.1%) and its 

effect on PM soot loading models is not significant in the more common forms available 

(i.e., B2 or two percent biodiesel content). If higher blends of biodiesel fuel do affect the 

robustness of the PM filter diagnostics, manufacturers can continue to do what they do 

today and limit their usage by specifying limits on biodiesel fuels which may be safely 

used to avoid voiding the engine warranty on parts that can be damaged by its usage, 

such as the PM filter, fuel injectors, seals, and rubber gaskets. Further, the 

uncertainties introduced by fuels would have a larger impact on soot loading models as 

the soot loading increases towards full. However, most manufacturers constrain 

monitoring to the period shortly after a regeneration event. Even if manufacturers 

extend the interval and/or wait until some minimum amount of soot is accumulated to 

achieve better separation between a good and malfunctioning PM filter, it is expected 

that manufacturers would still limit the loading to the lowest soot loading levels where 

they can achieve robust monitoring and where the uncertainties introduced by low levels 

of fuel variation should have minimal impact. 

As for PM sensors, staff agrees with industry that these sensors will not be 

commercially viable for the 2010 timeframe. However, PM sensor manufacturers are 

making progress and are continuing their development work towards developing a 

commercial product capable of meeting the 2013 model year PM filter thresholds. For 

the 2010 model year, as mentioned above, considering that some medium-diesel 

engine manufacturers are currently achieving the proposed 0.07 g/bhp-hr PM filter 

emission threshold without PM sensors for the 2007 model year, staff believes that 

heavy-duty diesel engine manufacturers should also be capable of meeting this 

threshold in the 2010 timeframe utilizing conventional technology (i.e., PM filter soot 

modeling and differential pressure sensors). 

In addition to the proposed amendment mentioned above, staff is also proposing 

changes to the malfunction criteria for PM filter frequent regeneration monitoring. 

Currently, the regulation requires manufacturers to indicate a frequent regeneration fault 

before emissions exceed 2.0 times the NMHC emission standards. However, in 
29

discussions with manufacturers and review of submitted emission data, NOx emissions 

have often increased significantly during PM filter regenerations. Depending on the 

manufacturer’s strategy, some NOx emission controls may be temporarily disabled or 

otherwise scaled back during regeneration events leading to a substantial NOx 

increase. In some cases, it appears that NOx emissions may be more affected than 

NMHC emissions as more frequent or extended regeneration events leads to more 

frequent and longer periods of reduced NOx control. Thus, staff is proposing to require 

manufacturers to indicate a fault before emissions exceed 2.0 times the NMHC 

standards or the applicable NOx standard by more than 0.2 g/bhp-hr, whichever occurs 

first, starting with the 2013 model year. 

Lastly, manufacturers have expressed concern about the current requirements for 

monitoring the NMHC conversion capability of catalyzed PM filters. Staff addressed this 

issue in section II. E (Diesel NMHC Converting Catalyst Monitoring) above. 

I. DIESEL EXHAUST GAS SENSOR MONITORING 

The HD OBD regulation currently details specific monitoring requirements for air-fuel 

ratio sensors and NOx sensors, while for other exhaust gas sensors such as PM 

sensors, manufacturers are required to submit a monitoring plan for ARB approval. PM 

sensors are less developed than NOx sensors, and thus, less is certain about the 

important characteristics of PM sensors relative to their use in emission control or their 

proper use as monitoring devices. However, staff has had discussions with sensor 

suppliers about PM sensor development and is encouraged by the early findings. 

Further, staff has held discussions with these suppliers about the need for diagnostics, 

and staff expects that basic diagnostics such as circuit checks, out-of-range values, and 

heater functionality will be easily implemented. For sensor response or other such 

characteristics, manufacturers may need to implement strategies similar to those being 

developed for NOx sensors and may require intrusive operation to verify sensor 

readings or response during known exhaust concentration conditions (e.g., during 

deceleration events where fueling is shut-off). Thus, staff is proposing to require 

manufacturers to monitor the PM sensors to the same specific requirements as those 

currently required for NOx sensors. 

J. GASOLINE FUEL SYSTEM MONITORING 

An important part of the emission control system on gasoline vehicles is the fuel system. 

Proper delivery of fuel is essential to maintain stoichiometric operation, maximize 

catalytic converter efficiency, and minimize tail pipe emissions. As such, the OBD 

regulations have always required fuel system malfunctions to be detected when the fuel 

system cannot maintain emissions below a specific threshold (e.g., 1.5 times the 

standards). 

Recent field testing of light- and medium-duty vehicles has revealed in-use fuel systemrelated malfunctions that OBD II systems generally cannot identify but which can cause 

emissions to exceed malfunction thresholds with no detection of a malfunction. ARB 
30

and manufacturers investigated this problem and found the cause to be cylinder-tocylinder differences or imbalances in the air-fuel ratio that are not properly corrected by 

the fuel control system. As stated, this type of malfunction or system deterioration can 

have a significant impact on emissions. The imbalances can be caused by fuel injector 

variation, unequal airflow into the cylinders, or uneven EGR distribution across the 

cylinders. In many cases, the front oxygen sensor, which is located in the manifold 

collector and is used for feedback fuel control, does not equally sense all cylinders and 

may cause the feedback fuel control system to be blind or overly sensitive to specific 

cylinders. This can result in improper fuel system corrections (i.e., the fuel system 

under-compensates or overcompensates for the imbalance) and higher emissions 

without detection of a malfunction. 

As this failure mode was not previously identified in the OBD II regulation, staff recently 

amended the OBD II regulation to include detection of this malfunction, and is currently 

proposing the same amendments to the HD OBD regulation. The staff is proposing that 

manufacturers be required to detect an air-fuel cylinder imbalance in one or more 

cylinders that causes the fuel delivery system to be unable to maintain emissions below 

a specified emission level. To provide manufacturers sufficient leadtime to comply with 

the new requirements, staff is proposing a phase-in during the 2014-2016 model years 

with a malfunction threshold of 3.0 times the standards, with all engines required to 

meet the final threshold of 1.5 times the standards in the 2017 model year. 

The staff is proposing a different phase-in schedule for vehicles equipped with certain 

types of EGR systems that have been found to be more prone to causing cylinder 

imbalance as the system deteriorates. The staff is proposing cylinder imbalance 

malfunctions be detected on all 2014 and subsequent model year engines equipped 

with EGR systems that have separate flow delivery passageways (internal or external) 

that deliver EGR flow to individual cylinders (e.g., an EGR system with individual 

delivery pipes to each cylinder). 

There are a number of monitoring strategies that may be used to detect cylinder 

imbalances. Monitoring of these types of failures may be accomplished by evaluating 

the front and/or rear oxygen sensor signals. During in-use testing of vehicles with 

cylinder imbalance malfunctions by ARB staff, one vehicle had a cylinder imbalance 

caused by intake valve deposits. The valve deposits caused an EGR effect in that 

cylinder that resulted in a rich air-fuel ratio relative to the other cylinders. Coincidentally, 

the oxygen sensor was oversensitive to the malfunctioning cylinder and the fuel system 

overcompensated by leaning out all the cylinders yielding an overall lean bias for the 

engine. The lean bias caused NOx emissions to significantly exceed the emission 

standards. The vehicle manufacturer analyzed the vehicle using special engineering 

tools to obtain a high-speed signal from the oxygen sensors. With the high speed data, 

the manufacturer observed that front oxygen sensor signal was noisy (i.e., there were 

rich spikes in the exhaust signal due the relatively rich air-fuel ratio in the cylinder that 

had the valve deposits). The noisy signal was an indicator that something was wrong 

with the system. Fuel system monitors generally use filtered or slower speed oxygen 

sensor signals to determine the average fuel system error caused by malfunctions that 
31

uniformly affect all cylinders. Therefore, typical fuel system monitors would not detect a 

noisy sensor as malfunctioning fuel system behavior. However, monitoring of the highspeed signal of the front sensor for this kind of behavior could be used to detect a 

cylinder imbalance fault. Additionally, the rear oxygen sensor signal also could show 

signs of cylinder imbalance. In the example discussed above, the rear oxygen sensor 

indicated a lean signal throughout the emission test cycle. However, depending on the 

fuel control strategy and the catalyst and sensor configuration, analysis of the rear 

sensor alone may not be sufficient for cylinder imbalance monitoring, nor would analysis 

of the rear oxygen sensor fuel control values be sufficient to cover all cases. 

(Monitoring of the downstream fuel control values will therefore remain a separate 

requirement in the regulation.) 

Staff is also proposing additional language regarding engines that employ engine 

shutoff strategies (e.g., hybrid buses that shut off the engine at idle) that was not 

comprehended in the current regulation. The HD OBD regulation currently requires 

manufacturers to detect fuel system malfunctions where the system fails to enter 

closed-loop operation within a certain time after engine start, which does not specifically 

address engines that can implement engine shutoff and restarts multiple times within 

the same driving cycle. Thus, staff is proposing to require manufacturers to detect fuel 

system malfunctions for these engines when the system fails to enter closed-loop 

operation within a certain time after every engine restart. 

Lastly, a minor change was made to harmonize with the light- and medium-duty 

regulation regarding secondary oxygen sensor fuel system monitors. Specifically, an 

allowance was added for manufacturers to eliminate the use of similar conditions for 

such monitors upon demonstration that the system only operates in sufficiently 

constrained conditions that there is no technical need to use similar conditions to ensure 

robust detection of faults.

K. GASOLINE MISFIRE MONITORING 

The staff is proposing to modify the gasoline misfire monitoring requirements in the HD 

OBD regulation to limit the monitoring of misfire during flare downs to just those 

occurring during positive torque conditions. Staff recently amended the OBD II 

regulation with the same change due to manufacturers’ arguments that, while there 

were no outside influences acting on the engine during the flare-down, the engine may 

be in negative torque and misfire monitoring accuracy could be affected. 

The HD OBD regulation currently requires manufacturers to monitor for misfire from no 

later than the end of the second crankshaft revolution after engine start. Similar to the 

issue for gasoline fuel system monitoring above, the language does not specifically 

address engines that employ engine shutoff strategies (e.g., hybrid buses that shut off 

the engine at idle) and can restart the engine multiple times within the same driving 

cycle. Thus, staff is proposing to require manufacturers to monitor for misfire no later 

than the end of the second crankshaft revolution after every engine restart. 
32

L. GASOLINE SECONDARY AIR SYSTEM MONITORING 

Secondary air systems are used on vehicles to reduce cold start exhaust emissions and 

typically consist of an electric air pump, hoses, and a check valve(s) to deliver outside 

air to the exhaust system upstream of the catalytic converter(s). The HD OBD 

regulation currently requires manufacturers to monitor the “air flow” delivered by the 

secondary air system and, in cases where there are more than one delivery hose (e.g., 

one to each side, or bank, of a V-6 engine), to verify that the proper amount of air is 

delivered through each hose. Industry, however, questioned the necessity of monitoring 

the air flow to each bank of the engine in cases where complete blockage of air delivery 

to one bank does not affect emissions. Thus, the staff is proposing modified language 

to exempt detection of flow to both banks if the manufacturer can show that complete 

blockage of air delivery to one bank does not cause a measurable increase in 

emissions. 

M. GASOLINE EVAPORATIVE SYSTEM MONITORING 

The HD OBD regulation currently requires monitoring of the complete evaporative 

system for vapor leaks to the atmosphere as well as verification of proper function of the 

purge valve. Traditionally, vehicles have used a single purge path to purge vapor from 

the system to the engine. However, some newer engines, especially turbo-charged 

engines, have implemented two paths to ensure sufficient purge during boost operation. 

For vehicles that rely on the proper function of both paths to maintain in-use emission 

levels, the requirement has been clarified to ensure that both purge paths are 

monitored. 

N. GASOLINE EXHAUST GAS SENSOR MONITORING 

The HD OBD regulation currently details specific monitoring requirements for “exhaust 

gas sensors,” with monitoring requirements split for exhaust gas sensors that are 

considered “primary” sensors versus “secondary” sensors. The OBD II regulation, by 

contrast, currently details specific monitoring requirements for oxygen sensors 

(conventional and wide-range or universal sensors), while manufacturers using other 

types of exhaust gas sensors (e.g., NOx sensors, PM sensors) are required to submit a 

monitoring plan for Executive Officer approval. Considering gasoline engines are 

generally not expected to utilize other exhaust gas sensors as much as oxygen sensors 

and to be consistent with the OBD II regulatory language, staff is proposing to modify 

the gasoline exhaust gas sensor monitoring language in the HD OBD regulation to 

detail specific requirements for oxygen sensors and require manufacturers to submit a 

plan for other exhaust gas sensors. 

Additionally, as is currently required in the OBD II regulation, staff is proposing to clarify 

what is expected of manufacturers when developing response rate monitors for primary 

oxygen sensors. Specifically, manufacturers would be required to detect both 

asymmetric malfunctions (i.e. faults that affect only the lean-to-rich response rate or 

only the rich-to-lean response rate) and symmetric malfunctions (i.e., faults that equally 
33

affect both the lean-to-rich and rich-to-lean response rates). These response rate faults 

include faults that affect the response either by delaying the initial reaction of sensor to 

an exhaust gas change (e.g., “delayed” response) or by delaying the transition from a 

rich reading to a lean reading (or vice-versa) (e.g., “slow transition”) (see Fig. 1 below). 

In previous years, while all light- and medium-duty manufacturers were currently 

capable of detecting each of these types of faults, not all of them had rigorously 

calibrated the monitors to ensure proper detection of the faults before emissions exceed 

1.5 times the standards. Accordingly, staff recently amended the OBD II regulation, and 

is currently proposing for the HD OBD regulation, to identify the failure modes for 

response that should be considered by manufacturers in calibrating the response 

diagnostic. Under the proposal, manufacturers would be required to consider six 

different response fault conditions when determining the worst case failure mode 

necessary for calibration: asymmetric lean-to-rich delayed response, asymmetric richto-lean delayed response, asymmetric lean-to-rich slow transition, asymmetric rich-tolean slow transition, symmetric delayed response, and symmetric slow transition. 

Manufacturers would be expected to determine an appropriate response monitor 

threshold(s) to ensure that all response failures are detected prior to exceeding 1.5 

times the standards. Further, beginning in the 2013 model year, manufacturers would 

be required to submit data and/or documentation demonstrating that they have used a 

calibration method that ensures that these criteria have been satisfied. 

Results from testing in-use light- and medium-duty gasoline vehicles by ARB staff have 

also reinforced the need for more rigorous monitoring of the secondary sensors used to 

monitor the catalyst for proper operation. For secondary oxygen sensors, the HD OBD 

Normal Signal 

Slow Transition (rich to lean) 

Time 

Volts 

Delayed Response (rich to lean) 

Fig. 1: O2 Sensor Deterioration Sketch 
34

regulation currently requires the diagnostic system to detect a fault, to the extent 

feasible, when the secondary oxygen sensor is no longer reliable for monitoring. Given 

the location of the sensor downstream of the catalyst, stringent monitoring of the sensor 

has been difficult to achieve or isolate from other effects (e.g., oxygen storage in the 

catalyst). Accordingly, staff had been accepting fairly simple “activity” diagnostics in 

light- and medium-duty OBD II vehicles that verify minimal operation of the sensor as 

acceptable monitoring techniques. Unfortunately, in-use vehicles with deteriorated 

secondary oxygen sensors and deteriorated catalysts were found to have high 

emissions and no MIL illumination. Staff found that replacement of the secondary 

oxygen sensor resulted in the diagnostic system being able to detect the malfunctioning 

catalyst and illuminate the MIL. Ideally, manufacturers’ secondary oxygen sensor 

monitors should be able to detect and illuminate the MIL for this fault (i.e., detect a 

malfunction for deteriorated sensors that cannot robustly detect a “threshold” catalyst). 

However, before the OBD II regulation was recently amended, very few manufacturers 

had monitors that met this ideal situation. Most monitors had a gap in the degree of 

sensor deterioration between where the sensor is no longer sufficient for catalyst 

monitoring and where the sensor itself can be detected as malfunctioning. Considering 

that catalyst fault codes are a significant percentage of the failures found in highmileage cars in I/M programs, the staff believed the OBD II regulation needed to be 

modified to make manufacturers better understand what is expected of the secondary 

oxygen sensor monitors and to avoid problems like these in the future. Further, recent 

improvements in monitoring techniques for the rear sensor were identified that enable 

more stringent monitoring of the sensor as well as improved monitoring techniques for 

the catalyst monitor that are less sensitive to secondary sensor performance 

degradation. 

Thus, staff recently amended the OBD II regulation to require better monitoring of the 

secondary sensors to ensure “sufficient” sensor performance for other monitors, and is 

currently proposing the same amendments for the HD OBD regulation. Specifically, the 

proposed amendments would require the OBD system be designed such that the worstperforming acceptable secondary sensor is able to detect the best-performing 

unacceptable system or component (e.g., catalyst) that uses the secondary sensor for 

monitoring. In other words, in the case of the catalyst monitor, the worst-performing 

secondary oxygen sensor that could “pass” the secondary sensor monitor should be 

able to detect a deteriorated catalyst that just barely “fails” the catalyst monitor (i.e., a 

catalyst deteriorated right to the threshold). If the OBD system is technically unable to 

meet this requirement, manufacturers would be required to submit a plan detailing how 

they will ultimately close the gap, and the proposed amendments would prescribe the 

minimum acceptable level of monitoring required of secondary oxygen sensors in the 

interim. Specifically, the OBD system would be required to detect a slow rich-to-lean 

response malfunction of the sensor during a fuel shut-off event (e.g., deceleration fuel 

cut event). This monitor would be required to monitor the response time during the 

following periods: (1) from a rich condition (e.g., 0.7 Volts) at the start of fuel shut-off to 

a lean condition (e.g., 0.1 Volts) expected during fuel shut-off conditions, and (2) the 

response time of the sensor in the intermediate sensor range (e.g., from 0.55 Volts to 

0.3 Volts). In order to develop a robust monitor, manufacturers would need to isolate 
35

the sensor response from catalyst effects and transport time as much as possible. 

Some manufacturers do not use fuel shut-off during deceleration to the degree or 

frequency that is necessary for the monitoring defined above. Therefore, in developing 

the proposed diagnostics, some manufacturers would have to make changes to their 

fuel control strategies to ensure that fuel shut-off is initiated from a rich condition (i.e., a 

sensor voltage that is greater than voltages necessary to make the response time 

measurements defined above) and occurs with sufficient in-use frequency to meet the 

minimum required monitoring frequency specified in the regulation. 

To allow time for manufacturers to make these changes across their product lines, the 

proposal would require all 2013 and subsequent model year engines to meet this 

requirement. The OBD system would be required to track and report the in-use 

monitoring frequency of this monitor starting with the 2013 model year. Additionally, 

prior to certification of 2013 model year engines, the manufacturers would be required 

to submit a comprehensive plan demonstrating the their efforts to minimize any gaps 

remaining between the worst-performing acceptable sensor and a “sufficient” sensor. 

O. COLD START EMISSION REDUCTION STRATEGY MONITORING 

In order to meet the standards, manufacturers have to use emission control strategies 

to minimize emissions during and after a cold engine start. The vast majority of 

emissions from gasoline engines during an FTP emission test are generated during the 

short period after engine start before the catalytic converter “lights off” (i.e., reaches the 

operating temperature where it begins to achieve high conversion efficiency). In order 

to minimize these cold start emissions, manufacturers use special strategies to 

maximize the heat transferred through the exhaust to the catalytic converter to 

accelerate light off. The most common elements of cold start strategies are 

modifications to engine speed and ignition timing. The idle speed is increased over the 

speed that is normally used, or is necessary, for a start-up. Increased idle speed 

increases exhaust mass flow. Ignition timing is also retarded from normal timing which 

makes the engine run less efficiently. Retarded ignition timing increases the exhaust 

temperature and further increases exhaust mass flow. Combined, the two elements 

generate hotter exhaust temperatures and more thermal mass that can be used to 

accelerate the light off of the catalyst. Staff required the monitoring of these cold start 

strategies in light- and medium-duty vehicles in 2002. The cold start monitoring 

requirements have been a difficult requirement for staff to administer. It requires a 

detailed disclosure by the manufacturers on how their cold start strategy works. At the 

same time, it requires an in depth understanding by both ARB staff and the 

manufacturers’ staff of how malfunctions, drivers’ actions, and vehicle operating 

conditions (e.g., fuel quality) can affect the proper execution of the cold start strategy. 

In reviewing the cold start monitoring strategies that manufacturers implemented in the 

OBD II systems, the staff has concluded that, in some cases, the monitors did not 

sufficiently ensure that the cold start strategies are successfully executed. For example, 

some monitors evaluated the combined effects of idle speed and ignition timing and 

only detected a malfunction when both elements (i.e., engine speed and ignition timing) 
36

of the emission reduction strategy have failed. The staff believes this is an 

inappropriate way to design the monitor because the OBD II system will not detect a 

malfunction until two failures have occurred. Other manufacturers have calibrated their 

monitors such that a malfunction will not be detected until the performance of the cold 

start system has deteriorated beyond what is required for normal warmed-up engine 

operation. For example, most manufacturers require increased idle speed during cold 

start. Some manufacturers, however, have implemented malfunction thresholds for the 

cold start monitor that require the engine speed to be less than the normal warmed up 

idle speed for a malfunction to be detected. While such an approach does indeed verify 

that the engine starts and idles, it does not verify that some amount of increased idle 

speed was achieved during the cold start. 

To address these issues, the staff amended to the cold start monitoring requirements in 

the OBD II regulation to ensure more consistent implementation of the requirements by 

all manufacturers. Specifically, the staff added language that described more specific 

malfunction criteria for the elements of the cold start monitoring strategy, requiring the 

OBD II system to detect a malfunction if either of two malfunction criteria is satisfied. 

For the first malfunction criterion, the OBD II system is required to detect a cold start 

malfunction if any single commanded element of the cold start strategy does not 

properly respond to the commanded action while the cold start strategy is active. A cold 

start strategy element has proper cold start response if the following conditions are 

satisfied: (i) the element responds by a robustly detectable amount; (ii) the element 

responds in the direction of the desired command; and (iii) the magnitude of response is 

above and beyond what the element would achieve on start-up without the cold start 

strategy active. For example, if the cold start strategy commands a higher idle engine 

speed, a fault must be detected if there is no detectable amount of engine speed 

increase above what the system would achieve without the cold start strategy active. 

For elements involving spark timing (e.g., retarded spark timing), the monitor may verify 

final commanded spark timing in lieu of verifying actual delivered spark timing. 

For the second malfunction criterion, the OBD II system is required to detect a cold start 

malfunction when any failure or deterioration of the cold start emission reduction control 

strategy causes a vehicle’s emissions to be equal to or above 1.5 times the applicable 

FTP standards. For this requirement, the OBD II system is required to either monitor all 

elements of the system as a whole (e.g., measuring air flow and modeling overall heat 

into the exhaust) or the individual elements (e.g., increased engine speed, commanded 

final spark timing) for failures that cause vehicle emissions to exceed the emission 

malfunction threshold. 

Staff is currently proposing these same modifications to the gasoline cold start emission 

reduction strategy monitoring requirements in the HD OBD regulation. Additionally, the 

staff is requiring heavy-duty diesel engines to monitor for malfunctions of the cold start 

emission reduction strategies. While not yet prevalent in heavy-duty engines, some 

light-duty diesel manufacturers have implemented such strategies and some heavy-duty 

manufacturers have indicated such strategies are being considered to reduce emissions 
37

shortly after engine start-up. The proposed amendments would ensure such strategies 

are monitored for proper operation when and if they are implemented. 

P. ENGINE COOLING SYSTEM MONITORING 

The heavy-duty OBD regulation requires manufacturers to monitor cooling systems for 

malfunctions that affect emissions or other diagnostics. Engine manufacturers often 

modify engine operation strategies based on engine coolant temperature (ECT) and 

utilize it to enable other OBD diagnostics. Malfunctions resulting in improper engine 

temperature regulation may disable OBD diagnostics, reduce OBD monitoring 

frequency, cause changes in engine and emission control operation, and cause an 

increase in vehicle emissions. Therefore, ARB has required cooling systems to be 

monitored to detect malfunctions if either of the following occurs: (i) the ECT does not 

reach the highest temperature required by the OBD system to enable other diagnostics, 

or (ii) the ECT does not reach a warmed-up temperature within 20 degrees Fahrenheit 

of the engine manufacturer’s nominal thermostat regulating temperature. Since engine 

manufacturers are responsible for designing their own OBD monitors, they have direct 

control over the first criteria by limiting how high they specify the enable temperature 

used for other monitors. Manufacturers that choose to design emission solutions that 

are less sensitive to temperature (or work effectively earlier in warm-up) and design 

diagnostics that are robust at lower warm-up temperatures can directly reduce the 

stringency of this monitor. 

Nonetheless, engine manufacturers have expressed difficulty in meeting these 

requirements primarily because the engine may be used in a variety of vehicles and 

with various other devices that affect the warm-up of the engine. Other than the 

assurance that there is sufficient cooling capacity at peak engine loads, historically, few 

constraints have been placed on vehicle manufacturers (i.e., truck builders) and thus, 

there is significant variance in the engine warm-up characteristics in individual vehicles. 

Due to this variety, engine manufacturers have commented that they cannot properly 

distinguish normal warm-up behavior from malfunctioning warm-up behavior. To 

address these concerns, manufacturers have proposed several modifications to the 

regulation they believe would make cooling system monitoring more feasible in the 2010 

timeframe. One such request involves a change that would allow cooling system 

monitors to take longer to make pass or fail decisions, spanning many more trips than 

the two-trip strategy currently allowed for decision making. Specifically, manufacturers 

have asked permission to only illuminate the MIL if a fault is detected on six consecutive 

trips. Engine manufacturers believe a 6-in-a-row monitoring strategy will effectively 

filter out abnormal drive patterns or anomalies in vehicle operation that may cause the 

system to occasionally be delayed in warm-up or not warm-up, yet they would still 

eventually detect a fault for systems with a true fault. 

ARB staff disagrees with the engine manufacturers’ request to use a longer statistical 

filter to detect faults because it does not adequately address the issue; these strategies 

simply allow for more time on less than sufficiently robust monitors hoping that false 

fails will not occur often enough or that the driver will not frequently or repeatedly 
38

engage in what they consider ‘abnormal driving patterns.’ A more appropriate solution 

is for engine manufacturers to better define enable conditions or the modeled coolant 

temperature to either account for or disable the monitor during such ‘abnormal’ driving 

conditions if an accurate pass/fail decision cannot be made. While this can result in 

less frequent monitoring and must be balanced with maintaining reasonable monitoring 

frequency under the breadth of conditions encountered in the real world, designing (or 

allowing) a monitor to run under conditions where it may make an incorrect decision is 

always inappropriate as it can lead to erroneous decisions in-use and undermine 

technician and vehicle operator confidence in the OBD system. Accordingly, staff will 

not be proposing a change to the currently required 2-in-a-row detection strategy. 

Engine manufacturers have also requested that cooling system monitoring be 

disabled/desensitized on engine starts with ambient or starting temperatures below 60 

degrees Fahrenheit. They believe this allowance will help reduce calibration burden 

and constrain monitoring to temperatures where truck cabin heat or other sources would 

be used minimally and would have less impact on delaying proper warm-up. The 

heavy-duty OBD regulation currently allows engine manufacturers, with Executive 

Officer approval, to use alternate malfunction criteria and/or monitoring conditions that 

are a function of temperature at engine start on engines that do not reach the 

temperatures specified in the malfunction criteria when the thermostat is functioning 

properly. Similarly, light- and medium-duty vehicles are given relief for engine starting 

temperatures below 50 degrees Fahrenheit and several engine manufacturers have 

used this provision for select vehicles (e.g., primarily vehicles with very large passenger 

compartments). ARB has recognized vehicle operation in California at temperatures 

below 50 degrees Fahrenheit is limited and accordingly, most ARB emission standards 

only apply down to 50 degrees Fahrenheit. However, the amount of vehicle activity in 

the temperature range from 50 to 60 degrees Fahrenheit is expected to be substantial in 

California, so monitoring to a less rigorous threshold in this temperature region could 

affect a substantial fraction of vehicle activity. As stated before, engine manufacturers 

have some control over the stringency of this monitor, as they have the ability to 

calibrate their OBD systems to use lower enable temperatures for appropriate monitors 

and still be robust in detecting faults. Thus, while ARB agrees that engine 

manufacturers should be allowed to desensitize the thermostat monitor on lower engine 

start temperatures, ARB is proposing to allow this on engine starts with temperatures 

below 50 degrees Fahrenheit, not 60 degrees Fahrenheit. 

Citing the difficulty in accounting for heat sinks, engine manufacturers have also 

requested that cooling system monitoring be limited to detection of malfunctions in 

which the thermostat is fully stuck open, irrespective of what temperature is or is not 

achieved. Manufacturers feel that simply verifying the thermostat is not fully stuck open 

would greatly simplify the monitoring process and allow manufacturers to design for a 

range of applications, ensuring some minimum capability on all applications. ARB, 

however, disagrees and believes failures that prevent proper warm-up for emissions 

and diagnostics need to be detected regardless of the failure mode (e.g., fully stuck 

open, partially stuck open, leaking, opening too early). 
39

Engine manufacturers would also be required to monitor for failures which cause the 

ECT to cool back down below diagnostic enablement temperatures after they have 

been reached (e.g. monitoring to ensure temperatures stay above thresholds after they 

are initially reached). In certain situations, an idling vehicle with a malfunctioning 

thermostat and low airflow across the engine bay can reach warmed-up temperatures 

and pass thermostat monitoring yet when the vehicle reaches higher speeds, additional 

cooling is introduced across the radiator and engine block, lowering the ECT below the 

temperature necessary for other OBD diagnostics. This situation could effectively 

disable all diagnostics that require off-idle operation without being detected as a cooling 

system fault as well as cause an increase in emissions in some instances (e.g., 

activation of low temperature AECDs that disable emission control functions, fall below 

optimal operating temperature windows for exhaust aftertreatment). The proposed 

revisions to the regulation include specific language identifying this malfunction and 

requiring monitoring for 2016 and subsequent model years. Staff has proposed longer 

leadtime for this specific requirement because of manufacturers’ previously stated 

concerns that they have insufficient control over truck builders with regards to equipping 

the engine with devices that prolong warm-up or cool the engine back down. By waiting 

until 2016 model year, manufacturers will have time to implement OBD across all 

engines and truck builders will become more aware of the choices they make and their 

impacts on proper operation of the OBD system. In some cases, this monitoring 

requirement could effectively impose design restrictions on the engine cooling system 

and force manufacturers to be more proscriptive in restricting what truck builders can 

and cannot add to an engine to remain in compliance. While this may be unfavorable, 

allowing truck builders to add equipment that effectively disables many OBD monitors 

and/or causes an engine to run below normal operating temperatures (and with an 

associated increase in emissions) is not an acceptable long term path for achieving and 

maintaining low emissions in-use. In some cases, a manufacturer may need to make 

design changes or include additional control strategies to ensure an engine stays above 

a minimum operating temperature under normal ambient conditions and the additional 

leadtime should allow manufacturers to investigate alternatives and/or implement such 

features. Further, as with other required thermostat monitoring, manufacturers will have 

the ability to constrain monitoring to operating conditions where they can robustly 

determine if the system is passing or failing and exclude conditions (e.g., very cold 

temperatures, very low speed driving) where such decisions cannot be made. 

 

Engine manufacturers have also expressed interest in allowing vehicle manufacturers 

some ability to calibrate their own cooling system criteria in order to properly account for 

appropriate heat/work losses in the final vehicle configuration. In recognizing the 

difficulty of engine manufacturers to calibrate for every type of vehicle the engine is 

likely to be used in, ARB believes giving vehicle manufacturers some capability to select 

between various calibration parameters to best match the specific vehicle configuration 

would be a workable solution. This would allow the OBD system to be better optimized 

for the specific truck configuration while still allowing vehicle manufacturers a wide 

range of authority in what they add to the system and how it impacts vehicle warm-up. 

While ARB feels this is a reasonable approach, engine manufacturers will need to take 

appropriate actions to ensure vehicle manufacturers are given proper instruction on how 
40

to determine the proper calibration to select and are not allowed to just default to one 

that would be inappropriate. Further, engine manufacturers are ultimately held 

responsible for OBD compliance in-use and inappropriate selection by vehicle 

manufacturers could result in enforcement action against the engine manufacturer. 

Q. CRANKCASE VENTILATION (CV) SYSTEM MONITORING 

During the engine combustion process, some exhaust gases can escape past the 

pistons into the crankcase and subsequently to the atmosphere. The CV system is 

used to contain these exhaust gases (also known as “blow-by”) and typically directs 

them to the intake to be re-routed through the engine. The CV system generally 

consists of a crankcase vapor outlet hose (through which the exhaust gas is directed 

from the crankcase to the intake ducting typically upstream of the compressor), and a 

CV valve to control the flow through the system. Many diesel systems also include a 

filter and/or oil separator to reduce the amount of oil and/or particulate matter that exits 

the CV system. As with CV systems on gasoline vehicles, staff believes the likely cause 

of CV system malfunctions and excess emissions is improper service or tampering of 

the CV system. These failures include misrouted or disconnected hoses, and missing 

or improperly installed valves, filters, or oil separators. Of these failures, hose 

disconnections on the vapor vent side of the systems and/or missing valves can cause 

emissions to be vented to the atmosphere. 

For vehicles with diesel engines, the HD OBD regulation currently requires 

manufacturers to submit a plan for Executive Officer approval of the monitoring strategy, 

malfunction criteria, and monitoring conditions prior to introduction on a production 

vehicle. Executive Officer approval is based on the effectiveness of the monitoring 

strategy to monitor the performance of the CV system to the extent feasible with respect 

to the proposed malfunction criteria detailed in the current regulation, which essentially 

requires the OBD system to monitor for disconnections between the crankcase and the 

CV valve and between the CV valve and the intake ducting. 

Instead of continuing to use the provision to require manufacturers to submit a 

monitoring plan for ARB approval, the staff is proposing to apply essentially the same 

monitoring requirements that are currently being required for gasoline vehicles and for 

light- and medium-duty diesel vehicles. Thus, the staff is proposing that manufacturers 

be required to monitor the CV system for disconnections between the crankcase and 

the CV valve and between the CV valve and the intake ducting. Regarding 

disconnection between the CV valve and the crankcase, detection would likely be 

significantly more difficult, and could require additional hardware such as a pressure 

switch to ensure flow in the system. However, in order to facilitate cost-effective 

compliance, the staff proposes to exempt manufacturers from detecting this type of 

disconnection if certain system design requirements are satisfied. Specifically, 

manufacturers can be exempted from monitoring in this area if the CV valve is fastened 

directly to the crankcase in a manner that makes technicians more likely to disconnect a 

monitored portion of the system (e.g., the line from the valve to the intake ducting 

provided this line is monitored) ) during service or if disconnection of the CV valve 
41

results in a rapid loss of oil such that the vehicle operator is certain to respond and have 

the vehicle repaired. Staff believes that this would eliminate most of the disconnected 

hose and valve events because technicians who do not reconnect the intake ducting 

hose when the service procedure is completed will be alerted to a diagnostic fault or oil 

leak that will lead the technician back to the improperly assembled component. 

Under the existing certification requirements for diesel engines, manufacturers are 

allowed to implement open CV systems (i.e., systems that release crankcase vapors to 

the atmosphere without routing them to the intake ducting or to the exhaust upstream of 

the aftertreatment) if the manufacturer accounts for the crankcase emissions to the 

atmosphere in the tailpipe certification values. Such systems have additional risk for 

emission failures because a malfunctioning filter or oil separator will result in much 

dirtier gases being vented directly to atmosphere instead of being routed into the 

engine. For these systems, the proposal would still require manufacturers to submit a 

monitoring plan for Executive Officer approval. The plan would be approved based on 

the effectiveness of the proposed monitor to detect disconnections and malfunctions in 

the system that prevent proper control of crankcase emissions (e.g., if the system is 

equipped with a filter to reduce crankcase emissions to the atmosphere, the OBD 

system shall monitor the integrity of the filter). 

In general, diesel engine manufacturers would be required to meet design requirements 

for most of system in lieu of actually monitoring many of the hoses for disconnection. 

Specifically, the proposed regulation would allow for an exemption for any portion of the 

system that is resistant to deterioration or accidental disconnection and not subject to 

disconnection during any of the manufacturer’s repair procedures for non-CV system 

repair work. These safeguards should eliminate most of the disconnected or improperly 

connected hoses while allowing manufacturers to meet the requirements without adding 

any additional hardware solely to meet the monitoring requirements. Where monitoring 

is required between the CV and the intake ducting, it is possible to use monitoring 

strategies similar to those used on gasoline vehicles. For example, if the components 

of the CV system are properly sized, a disconnected line will cause a large source of 

unmetered air to be inducted into the engine which can be detected by EGR or intake 

air mass flow rationality monitoring. 

R. COMPREHENSIVE COMPONENT MONITORING 

One of the most important elements of the OBD system is that it requires 

comprehensive monitoring of all electronic powertrain components or systems that 

either can affect emissions or are used as part of the OBD diagnostic strategy for 

another monitored component or system. This includes input components such as 

sensors and output components or systems such as valves, actuators, and solenoids. 

Monitoring of all these components is essential since their proper performance can be 

critical to the monitoring strategies of other components or systems. 

However, as engines and vehicles have become increasingly sophisticated, there has 

been a proliferation of electronic components much beyond the traditional electronic 

powertrain components that existed when OBD was started. Many of these 
42

components are peripheral components not related to fuel or emission control of the 

engine. Yet, by the most stringent of interpretations, these ancillary components could 

be considered subject to OBD because they are powertrain-related and could affect 

emissions indirectly by increasing electrical demand or load on the engine when 

malfunctioning. 

In order to keep OBD systems containable and focused on identifying the powertrain 

components more directly related to fuel or emission control, the staff is proposing 

changes to the heavy-duty OBD regulation similar to those recently added to the OBD II 

regulation to exclude certain types of powertrain components. Specifically, the 

proposed changes would exclude components that are driven by the engine or can 

increase emissions only by increasing electrical demand or load on the engine and are 

not related to fuel or emission control. Examples of such excluded components could 

include electric power steering systems or intelligent vehicle charging systems. 

Additionally, while hybrid powertrain components are subject to monitoring, the current 

regulation does not have very specific guidelines aimed at hybrid components, and 

some manufacturers have been unsure as to how to design their hybrid component 

diagnostics to be acceptable under the regulation. Ideally, the regulation would provide 

specific performance and diagnostic requirements for each and every hybrid 

component. Unfortunately, hybrids are still rapidly evolving and neither the staff nor 

manufacturers have developed sufficient experience to detail monitoring requirements 

for all hybrid components that would properly comprehend how they are used in all 

applications. Thus, the staff has proposed the inclusion of general guidelines specifying 

that monitoring would be required for (1) all components/systems used as part of the 

diagnostic strategy for other monitored component/systems, (2) all energy input devices 

to the electrical propulsion system, and (3) battery charging system performance, 

electric motor performance, and regenerative braking performance, and has added a 

provision that would require manufacturers to submit a monitoring plan for ARB’s review 

and approval. 

Manufacturers have expressed concerns about the specific requirement in the HD OBD 

regulation to monitor both the MIL and the wait-to-start lamp for circuit continuity 

malfunctions (e.g., burned out bulbs). Specifically, manufacturers have argued that, as 

engine builders/suppliers, they do not have control over the instrument panels and 

driver displays selected by truck builders in the final vehicle. In many of those systems, 

the warning lights are directly wired and controlled by the instrument panel itself, not the 

engine control unit (ECU), and it would require instrument panel changes and/or added 

hardware or software in the instrument panel to diagnose the lights and send that 

information back to the engine ECU. As another option, manufacturers would need to 

provide for and require that these warning lamps be directly hardwired to the engine 

ECU to ensure enough information is available to diagnose the circuits. Further, 

manufacturers have indicated a strong trend in industry to change from incandescent 

bulbs to light emitting diode (LED) technology for the warning lamps. Manufacturers 

have argued that LEDs are much less susceptible to burned out bulb failures, leaving 

only circuit faults to the LED as a likely failure mode. In some cases, the LEDs are 
43

directly attached to circuit boards, virtually eliminating any hardwiring. Lastly, one 

manufacturer has indicated that given the nature of an LED and its extremely low 

current draw levels, certain failure modes within the LED itself are not technically 

feasible to detect. 

Staff’s original intent for monitoring the wait-to-start lamp was different from the 

rationale for monitoring the MIL. For the wait-to-start lamp, monitoring has always been 

required in light-duty from the start of OBD II implementation. If this lamp does not 

function properly, a vehicle operator may crank the engine too soon, causing increased 

emissions from extended cranking or failed crank attempts before the engine is finally 

started. Further, if the lamp malfunctioned, the MIL would be illuminated to indicate the 

need for repair. Based on the potential for direct emission impact, staff is not proposing 

any changes to the requirements for wait-to-start lamp monitoring. For MIL monitoring, 

however, the rationale for monitoring was to simplify roadside or other inspections of 

heavy-duty vehicles. Rather than requiring an inspector to shut off the engine and enter 

the vehicle cab to visually look for the proper function of the MIL (and record that 

observation somehow), the intent was the entire inspection could be automated and all 

necessary information could be downloaded electronically via a scan tool. However, the 

presence of a non-functional MIL does not necessarily need to be considered in a 

roadside type inspection. Unlike the wait-to-start lamp, a malfunction of the MIL by itself 

does not lead to a direct emission impact. And, unlike other malfunctions that result in 

MIL illumination, a malfunction of the MIL itself prevents the MIL from illuminating, 

thereby largely eliminating the chance for the driver to be alerted and take appropriate 

action. If other emission-related faults are present, the data downloaded at inspection 

will properly indicate the fault data and lead to correct pass/fail decisions. Given the 

minimal additional benefit for roadside inspection and the reduced opportunity for a 

driver to voluntarily notice and take corrective action for a failed MIL, staff is proposing 

to eliminate the requirement to monitor the MIL for circuit malfunctions in the HD OBD 

regulation. 

Heavy-duty manufacturers have also expressed concern for potential monitoring of 

vehicle speed sensors located in the transmission. Manufacturers have indicated that 

the vehicle speed sensor may be needed to enable certain monitors, such as idle 

misfire monitoring. However, similar to the argument about the MIL and wait-to-start 

lamp monitoring, manufacturers have argued that, as engine builders/suppliers, they do 

not have control over the components in the transmission, including the vehicle speed 

sensor. Thus, manufacturers originally asked to be exempted from monitoring the 

vehicle speed sensor even though they would be using that sensor to enable other OBD 

monitors. After being told that would be unacceptable, manufacturers submitted an 

alternate plan that would including partial monitoring and MIL illumination for the vehicle 

speed sensor but would still require special handling as they wanted to exclude vehicle 

sensor failures from emission warranty, they wanted to exclude other transmission 

components from monitoring even though they were used to monitor the vehicle speed 

sensor itself, and they wanted to exclude disclosure and the review and approval 

process by ARB for these additional diagnostics. Staff, however, disagrees with 

manufacturers’ proposal. Staff believes if the manufacturer uses the vehicle speed 
44

sensor signal from the transmission to enable an OBD monitor, the manufacturer must 

monitor the sensor as required under the comprehensive component monitoring 

requirements (including monitoring of components used to monitor the vehicle speed 

sensor itself, MIL illumination and proper fault handling upon fault detection, and 

disclosure of such diagnostics to ARB for review and approval). Further, the emission 

performance warranty is clear that all items that turn on the MIL are subject to emission 

warranty and other provisions such as warranty reporting. Manufacturers have 

indicated that one transmission supplier in particular has informed them that they are 

prohibited from using information from their transmission for OBD purposes. Given that, 

there are still several options available to manufacturers including using alternate 

transmission suppliers (which will likely result in this transmission supplier reconsidering 

its position if its products are unable to be used with any heavy-duty engine). Other 

options including installing a dedicated vehicle speed sensor that is under the control of 

the engine manufacturer or using sources other than the transmission for vehicle speed 

information. Staff, however, still believes the best solution would be to have the 

transmission supplier provide a raw, undefaulted vehicle speed signal to the engine 

controller so that the engine controller could perform all of the necessary diagnostics. 

While this would still subject the vehicle speed sensor in the transmission to warranty 

requirements, this would avoid drawing other transmission components into the OBD 

system. 

Additionally, for 2013 and subsequent model year heavy-duty engines, manufacturers 

would be required to monitor fuel control system components (e.g., injectors, fuel 

pumps) that have tolerance compensation features implemented in hardware or 

software during production or repair procedures. Examples of these include individually 

coded injector-to-injector tolerances and fuel pumps that use in-line resistors to correct 

for differences in fuel pump volume output. Some manufacturers have indicated they 

are currently using or are planning to use such components to achieve more consistent 

emission performance from cylinder to cylinder and would be reliant on proper assembly 

as well as on repair technicians to properly reprogram engine computers with the right 

coding upon fuel system component replacement in the field (e.g., a new injector). Staff 

is concerned that such systems are more prone to erroneous or incomplete repairs and 

will result in undetected increases in emission levels. Accordingly, monitoring of such 

systems will be required to ensure that mis-assembly, erroneous programming, or 

incomplete repair procedures that result in incorrect adjustments being applied will be 

detected. 

S. EMISSION-RELATED COMPONENT FAILURE MODES 

The heavy-duty OBD regulation requires manufacturers to monitor “emission-related” 

components and systems that can either affect emissions or other OBD monitors. For 

major emission-related components or systems, functional monitors are generally 

required if a specific failure does not cause emissions to increase above the OBD 

emission threshold. For other emission-related input or output electronic components 

like sensors or valves, they are required to be monitored as completely as possible, 

regardless of the emission impact of individual failure modes of the component. This 
45

generally includes monitoring for circuit/out-of-range, rationality high and low, and 

functional faults. 

Manufacturers have expressed concerns with these requirements. Specifically, while 

the regulation specifies the components and systems that are required to be monitored, 

it does not distinguish between emission-related and non-emission-related “failure 

modes” of these components and systems. Manufacturers have indicated they should 

not have to monitor for specific failure modes of a component or system that do not 

impact emissions or other OBD monitors and believe the regulation language should be 

modified to allow manufacturers to be exempt from monitoring of these specific failure 

modes. For example, if a valve can only affect emissions when stuck closed, 

manufacturers argue they should not also have to detect stuck open failures. 

ARB staff, however, disagrees. Allowing regulation language that would exempt 

monitoring of specific failure modes would only lead to many more discussions and 

arguments between manufacturers and ARB staff regarding whether or not a specific 

failure mode does indeed affect emissions during any reasonable in-use driving 

condition. One area of contention could be the specific driving conditions or driving 

cycle under which the emission impact of the specific failure mode should be evaluated. 

A failure mode that does not cause any emission increase during cruising conditions, for 

example, may cause a considerable increase in emissions during higher load driving. 

Manufacturers would have to run many test cycles to determine which driving conditions 

would indeed impact emissions. Additionally, considering the many applications one 

engine can be used in, manufacturers would need to determine if the failure mode that 

does not affect emissions in one application (e.g., a bus that mostly experiences city 

driving) could affect emissions in another application (e.g., trucks that run mostly on the 

freeways). Another area of contention could be the actual impact of the specific failure 

mode on other OBD monitors. For example, a manufacturer may consider a particular 

failure mode to be non-emission-related because, in addition to not resulting in any 

emission increase, the failure mode would not directly cause the disablement of any of 

the OBD monitors. However, this failure mode may indirectly affect another component 

of the vehicle such that certain enable conditions of other OBD monitors may be harder 

to meet (e.g., a failure mode of one component could indirectly slow down the increase 

of the engine coolant temperature, thereby delaying enablement of other monitors tied 

to engine coolant temperature). This would require a lot of analysis and testing on the 

part of the manufacturer and ARB staff to rule out all these indirect consequences and 

to consider which other OBD monitors may be affected. For the few failure modes that 

may fall under such an exemption, the amount of workload required to determine if 

these failure modes are indeed exempt would be huge. It should also be noted that, 

under the current policy, manufacturers are not required to add any additional hardware 

just to accomplish monitoring of all failures—monitoring of all failures is limited to 

monitoring that is technically feasible. 

Thus, ARB is maintaining its current policy to require the complete monitoring of 

emission-related components and systems. A component that is experiencing a failure 

mode that does not have an emission impact or affect other OBD monitors is still clearly 
46

a malfunctioning component. If a repair technician sees an emission-related component 

experiencing this failure mode but with no MIL illuminated, this may cause confusion 

with the technician, which would undermine the confidence of the OBD system in the 

field. With the heavy-duty OBD regulation requiring the complete monitoring of these 

components, the extra workload to distinguish emission-related failure modes from nonemission-related failure modes will not be necessary and the confidence in OBD in the 

field will be sustained. 

T. EMISSION CONTROL STRATEGIES 

Based on recent meetings with manufacturers, staff has concerns that manufacturers 

are not designing OBD systems to monitor certain aspects of the emission control 

system, especially those that are not “specifically” identified in the regulation. The intent 

of OBD systems is to detect virtually any malfunction that leads to an emission increase 

yet staff is discovering some manufacturers have additional emission controls or 

strategies that they have not readily disclosed to the OBD staff nor been considered 

when developing diagnostics. Staff is proposing amendments to reiterate and clarify 

that, if there is an emission control strategy being used by the engine, manufacturers 

should be monitoring this strategy for proper operation to the extent possible. Such 

monitoring should include faults that disable, prevent, or delay the strategy from 

properly operating and faults that cause the strategy to reach adaptive or authority limits 

and be unable to achieve the desired goal under conditions where it should be able to 

achieve them. In most cases, this will include monitoring of input components that are 

used to enable the strategy or as feedback for feed-forward information, output 

components that are controlled by the strategy to achieve the desired goal, and the 

overall function of the strategy itself. 

In addition to proposed language in the other emission controls section and the 

comprehensive component sections for input and output components, staff proposed 

specific language for the EGR and boost monitors to further address this issue. The 

diesel EGR and boost pressure monitoring requirements include malfunction criteria tied 

to the system being unable to achieve proper closed loop control (e.g., not entering 

closed-loop control when it was expected to, reaching control limits when it should not 

have). These requirements could be interpreted as only applying if the system has 

direct feedback control of EGR flow or boost pressure (e.g., to a target EGR flow or 

boost pressure level). However, as mentioned above in sections II.C. and II.D. for 

diesel EGR and boost pressure control system monitoring, some manufacturers are 

using control systems with slightly different target parameters in lieu of EGR flow or 

boost pressure as staff originally anticipated (e.g., modify or control EGR flow not to 

achieve a target EGR flow rate but to achieve a target air-fuel ratio). Accordingly, these 

alternate systems should be similarly monitored for failures that affect proper closed 

loop operation. Staff is thus proposing to require manufacturers to submit a monitoring 

plan for ARB’s review and approval. This would allow manufacturers and ARB staff to 

evaluate the technology and determine an appropriate level of monitoring that is both 

feasible and consistent with the closed-loop monitoring requirements for the EGR and 

boost pressure control systems and would ensure that manufacturers cannot avoid 
47

monitoring of critical emission control systems simply by creating a new control 

parameter name. 

U. OTHER PROPOSED AMENDMENTS 

Staff is proposing modifications to better define “continuous” monitoring for several 

monitors in the HD OBD regulation. Currently, the regulation defines “continuously” in 

the context of monitoring conditions for comprehensive component circuit and out-ofrange monitors but not in the context of monitoring for other major monitors. 

Accordingly, this definition doesn’t apply for monitors such as diesel fuel pressure 

control monitoring and EGR system feedback control monitoring, which are also 

required to be monitored “continuously.” As these systems are typically continuously 

controlled, staff believed monitoring “continuously” was appropriate. However, staff 

acknowledges that there typically are conditions where control is not being done (e.g., 

shortly after engine start-up) and that there are conditions where robust monitoring 

could not be done (e.g., monitoring for too low EGR flow faults when EGR is 

commanded closed) and that continuous monitoring may not have been the most 

appropriate term. When used in the context of these monitors, staff intended for 

manufacturers to design the monitors to run virtually all the time except during 

conditions where robust fault detection is not possible. To avoid further confusion, staff 

modified the monitoring conditions requirement for these monitors to more explicitly 

state that. 

III. PROPOSED REVISIONS TO OBD II REGULATION 

At the request of medium-duty diesel manufacturers in order to maintain consistency 

between the HD OBD and OBD II diesel requirements, staff is proposing to carry over 

almost all of the proposed diesel-related changes mentioned above for the HD OBD 

regulation to the OBD II regulation, applying them to medium-duty diesel vehicles. The 

engines used in medium-duty diesel vehicles are often the same or similar to engines 

that also go in heavy-duty vehicles, are built and certified primarily by heavy-duty 

manufacturers, and often use the heavy-duty certification procedures as is currently 

allowed. Accordingly, the staff believes harmonization of the requirements is largely 

appropriate. The light- and medium-duty OBD II regulation is scheduled to begin a 

biennial review later this calendar year and further revisions for light-duty vehicles will 

be considered then. However, to avoid an interim mismatch in the requirements 

between the HD OBD regulation and the OBD II regulation, the changes that are 

applicable to medium-duty diesels are being proposed jointly. In some cases, the 

changes to medium-duty diesels involve clarification of requirements that are also 

applicable to light-duty diesels and will apply to both light- and medium-duty. However, 

modifications to specific emission threshold values (e.g., the interim higher threshold 

values for some diesel monitors) are proposed only for medium-duty vehicles and will 

not be applied to light-duty diesels. Any revisions to light-duty diesel emission 

thresholds will be considered and brought to the Board during the biennial review of the 

light-duty regulation scheduled to begin later this year. The specific proposed changes 

to the OBD II regulation can be found in Attachment B. 
48

Additionally, staff is proposing one change to the gasoline monitoring requirements in 

the OBD II regulation concerning the phase-in schedule for primary oxygen sensor 

response rate monitoring data submission. Currently, manufacturers are required to 

submit data and/or engineering analysis to demonstrate that their oxygen sensor 

monitors are able to detect all asymmetric and symmetric response rate malfunctions 

with a phase-in starting with the 2010 model year. However, recent discussions with 

manufacturers indicate that more time is needed to meet this requirement. Thus, staff is 

delaying the start of the phase-in from the 2010 model year to the 2011 model year, 

with all vehicles required to meet this requirement for the 2013 and subsequent model 

years. 

IV. PROPOSED REVISIONS TO HEAVY-DUTY OBD STANDARDIZATION 

REQUIREMENTS 

A. REFERENCE DOCUMENTS 

The staff is proposing amendments that would update the list of SAE and ISO 

documents that are incorporated by reference into the HD OBD regulation. As is 

common practice with technical standards, industry periodically updates the standards 

to add specification or clarity. The current HD OBD regulation incorporates the 2005 

version of technical standard SAE J1939 and associated documents. The proposal 

would update the regulation to incorporate the most recently adopted versions of each 

applicable part of SAE J1939.1

 The proposed amendments would also incorporate the 

most recently adopted versions of several other SAE (i.e., SAE J1930, J1979, J2012, 

and J2403) and ISO documents (i.e., ISO 15765-4). Several other SAE standards are 

currently being prepared for ballot and adoption. As these documents are only updated 

every few years, staff will monitor the progress of adoption of these updates and include 

them in this rulemaking (through staff suggested changes presented at the Board 

Hearing) if they are adopted within time. Furthermore, the staff is proposing to 

incorporate two additional SAE technical standard documents to the HD OBD 

regulation. Specifically, the staff is proposing to add: (1) SAE J1699-3 – “OBD II 

Compliance Test Cases”, May 2006; and (2) SAE J2534-1 – “Recommended Practice 

for Pass-Thru Vehicle Programming”, December 2004. SAE J1699 and SAE J2534-1 

are currently used by light- and medium-duty vehicle manufacturers for production 

engine/vehicle evaluation (PVE) testing of standardized requirements, and are expected 

to be used for PVE testing of heavy-duty engines (§1971.1(l)(1)) that use the ISO 

15765-4 protocol. 

B. PERMANENT FAULT CODES 

The HD OBD regulation currently requires the OBD system to store a “permanent” fault 

code for an emission-related fault in non-volatile memory that can only be erased if the 

 

1

 Staff had not yet obtained the SAE J1939 documents at the time this staff report was published. 

ARB will make these documents available as soon as it receives them, and will reference them and make 

them available for comment in a subsequent 15-Day Notice. 
49

monitor responsible for setting that fault code has run and passed enough times to 

confirm that the fault is no longer present. These fault codes are intended to address 

fraudulent inspection issues where vehicle owners or technicians could erase the 

emission-related fault information, including the fault codes, through a battery 

disconnection or by a scan tool command without repairing the fault. 

There have been a number of questions as to how specifically the OBD system would 

erase a permanent fault code, specifically after a clearing of all other fault information 

(through a battery disconnection or a scan tool clear command) and for continuous 

monitors versus monitors subject to the minimum in-use performance ratio requirements 

(e.g., once-per-trip monitors). For monitors that are designed to run continuously, 

including monitors that must wait until similar conditions are satisfied (e.g., misfire and 

fuel system monitors), there has been uncertainty about when a permanent fault code 

should be cleared since a continuously running monitor makes multiple pass/fail 

decisions throughout the driving cycle. Further, for monitors requiring similar conditions 

to be satisfied prior to extinguishing a MIL, there has been uncertainty since there is no 

requirement to store similar conditions in NVRAM along with the permanent fault code 

and thus, no way to know if similar conditions have been satisfied or not. Recently 

adopted language in the OBD II regulation requiring implementation of permanent fault 

codes included language that clarified the protocol under which the fault codes could be 

erased to ensure consistent implementation by all manufacturers and consistent 

methods for repair technicians to prepare vehicles for re-inspection by clearing 

permanent fault codes, and staff is currently proposing for the same amendments for 

the HD OBD regulation. The proposed amendments would require that the permanent 

fault code be erased only after the vehicle has been operated on a driving cycle in 

which both the monitor has run and passed without any indication of a malfunction and 

the criteria similar to those for a general denominator (§1971.1(d)(4.3.2)(B)) have been 

satisfied (with the exception that the general denominator conditions require ambient 

temperatures above 20 degrees Fahrenheit or below 8000 feet in elevation). This 

would ensure that the vehicle has been operated for a sufficient period of time to 

reasonably detect a recurrence of the malfunction but does not unnecessarily delay 

erasure of permanent fault codes. By eliminating the dependency on ambient 

temperature and altitude, the driving conditions can easily be met throughout California 

and the nation, regardless of location or seasonal temperatures. Further, in the special 

case of erasing a permanent fault code for a monitor that uses similar conditions 

following a code clear event, this eliminates the need for manufacturers to store similar 

conditions in NVRAM and actually prohibits manufacturers from using similar conditions 

to erase the permanent fault code. While this creates the possibility that a permanent 

fault code may be erased before the vehicle encounters similar conditions to those in 

which the malfunction was originally detected, this is a reasonable compromise since 

generic scan tools are not capable of reading similar conditions information, and repair 

technicians would be unable to determine how to operate the vehicle to erase a 

permanent fault code - a situation that would be unacceptable for inspection programs. 

C. ACCESS TO ADDITIONAL DATA THROUGH A GENERIC SCAN TOOL 
50

Currently, manufacturers are required to report certain “real-time” data parameters in a 

format that a generic scan tool can process and read so technicians can access the 

data for trouble-shooting malfunctions. In recent years, feedback from technicians in 

the field has identified the need for additional parameters to be made available by the 

OBD system to assist them in effective repair. Thus, the proposed amendments define 

some additional parameters (data stream and freeze frame values) that manufacturers 

would be required to report. These additional parameters would include values related 

to PM filter regeneration (e.g., average distances between regeneration events), EGR 

temperature, reductant level, and NOx adsorber regeneration and deSOx status. While 

the proposed data parameters would generally be used by technicians to assist them in 

repairs, some of the data could also used to facilitate inspection programs and 

compliance or enforcement testing by ARB staff. It is also expected that continued 

improvement and development in the in-use emission testing procedures and 

equipment currently being established for heavy-duty engines may identify the need for 

additional standardized parameters and/or modifications to proposed parameters that 

can be incorporated during a future regulatory revision. 

D. EMISSION-RELATED TEST RESULTS 

The heavy-duty OBD regulation currently requires a large number of monitors to report 

the test results of the most recent monitoring event. Some manufacturers have 

questioned the necessity of requiring continuous monitors to store test results, since the 

test results technicians will read from a scan tool will not reflect the most recent 

monitoring event anyways. Staff has reviewed the monitors subject to reporting test 

results and has identified and proposed language to exclude test results for several 

monitors related to feedback control. However, the proposed amendments do not 

remove the requirement to report results for continuous monitors. While staff 

recognizes that there will be a lag between decisions being made and those that the 

technician is currently looking at, the results could still be a benefit when diagnosing 

intermittent malfunctions. Such malfunctions may be present long enough for 

technicians to see them or, more likely, current scan tools will be able to continuously 

update test results and log them so a technician could scroll through the data to look for 

anomalies. Some manufacturers also indicated that for many of the continuous 

monitors, such as fuel pressure, a technician might be better served by watching the 

instantaneous fuel pressure rather than periodically updated test results. However, 

manufacturers often use complicated algorithms to determine if a system is passing or 

failing (e.g., integrated pressure error above and beyond a variable level of expected 

deviation from the commanded pressure) that would not be discernible to a technician 

visually observing instantaneous fuel pressure. Outputting the results that are already 

being calculated internally in the computer should be a trivial task for software designers 

and could provide tangible benefits to repair technicians. 

 

E. IDENTIFICATION AND VERIFICATION NUMBERS 

The HD OBD regulation currently requires OBD systems to support parameters 

identifying the current software “version” or calibration (CAL ID) and an internal 
51

calculated result to verify the integrity of the software (calibration verification number 

(CVN)). These two parameters are intended to be used to help verify that valid software 

is installed in the on-board computer and that the software has not been corrupted or 

tampered. As various states around the nation have begun to collect these data on 

OBD II vehicles, further revisions were found to be necessary based on feedback from 

the field to facilitate the usage of these parameters in inspection programs. Thus, staff 

recently adopted changes to the CAL ID and CVN requirements in the OBD II 

regulation, and is currently proposing similar amendments to the requirements in the HD 

OBD regulation. First, staff is proposing to require all engines to respond with an equal 

number of CAL IDs and CVNs and in the same order such that off-board equipment 

could match up each CAL ID with its corresponding CVN. Further, manufacturers are 

required to either design the engines to respond with a single CAL ID and CVN 

combination for each on-board computer or to respond with them in a fixed order of 

importance (from most critical for proper emission control to least critical). These two 

changes will allow reasonable size databases to be established to gather and use the 

CAL ID and CVN data in inspection programs. Lastly, the regulation currently requires 

the CAL ID and CVN information to be reported in a “standardized electronic format”, 

but with no information on what the standardized format is. Staff recently developed 

such a standardized template and will be sending it out to industry in an ARB mail-out 

and is proposing to bring amendments to the Board at the hearing to specifically refer to 

this mail-out in the regulation. This will provide a uniform format to receive the data 

from all manufacturers and facilitate further testing to incorporate usage of the data. 

Lastly, regarding CVN and CAL ID, a clarification was made by removing the word 

‘reprogrammable’ from the language. When originally adopted in the light-duty OBD II 

regulation, CVN was only required on reprogrammable computers. Subsequent 

revisions required CVN for all computers but the old language for reprogrammable was 

never removed and mistakenly included in the HD OBD regulation. To avoid further 

confusion, the term is being removed so that there is no conflict with the following 

sentence which requires CVN in every emission or diagnostic-critical computer. 

Staff is also proposing two additional pieces of information be made available from the 

HD OBD system to a scan tool. Specifically, as was previously adopted for light- and 

medium-duty vehicles, staff is proposing that 2013 and subsequent OBD systems 

support a function that associates a name or function with each electronic control unit 

(ECU) that responds to a generic scan tool. This ECU name function provides 

technicians with additional valuable information by allowing a scan tool to not only report 

data or fault information but tell the technician which ECU is reporting the data (e.g., 

engine controller, transmission controller). For some faults, diagnosis and repair can be 

greatly expedited by isolating which ECU is reporting the fault information especially in 

cases where data from a single component is used by several ECUs. Secondly, the 

proposed amendments include a requirement for the HD OBD system to report engine 

serial number (ESN) starting in the 2013 model year. Discussions with manufacturers 

and ARB staff from enforcement, roadside testing, and other sections has indicated that 

ESN is commonly used by industry to identify specific engine characteristics or 

configurations and is used by field inspectors when performing roadside inspections. 

As this parameter appears to already be supported and available in all engines, adding 
52

a requirement that it be available to generic scan tools should be a trivial change and 

will allow easier automated collection of data and identification of the engine. 

F. EMISSION-INCREASING AUXILIARY EMISSION CONTROL DEVICE (EI-AECD) 

TRACKING 

An additional important item relative to the effectiveness of diesel emission controls inuse is the usage of auxiliary emission control devices (AECDs). Typically, AECDs 

consist of alternate control strategies or actions taken by the engine controller for 

purposes of engine, engine component, or emission control component protection or 

durability. In some cases, activation of an AECD has been justified by the manufacturer 

as needed to protect the engine and it can result in substantial emission increases while 

the AECD is activated. AECDs have been an essential part of the certification process 

and the subject of numerous mail-outs and guidance by U.S. EPA and ARB to help 

ensure consistent interpretation and equity in usage among all manufacturers. Approval 

usually involves lengthy review and considerable scrutiny by ARB staff to try and 

understand the complex algorithms and strategies used by various manufacturers and 

additionally relies on data supplied by manufacturers as to the expected 

occurrence/operation of these items in-use. However, such data are often based on the 

operation of one or two trucks for a few hours of operation and are not likely to be 

representative of the extreme variances in engine duty cycles and vehicle operator 

habits that the diesel engines are exposed to in the real world. Further, the complicated 

algorithms and calculations used by manufacturers to activate such strategies are not 

easily decipherable nor comparable from one manufacturer to another, making 

consistent policy decisions and equity among all manufacturers extremely difficult, if not 

impossible, to achieve. 

To help alleviate this issue, the OBD II regulation was recently amended to require the 

on-board computer on light- and medium-duty diesel vehicles to keep track of 

cumulative time that a subset of these AECDs is active – the staff is now proposing 

similar requirements for the HD OBD regulation. Specifically, the proposed language 

would require tracking of AECDs that cause an emission increase (i.e., emission 

increasing AECDs or EI-AECDs) on 2013 and subsequent model year diesel engines. 

Further, the proposed language would only require tracking of EI-AECDs that are 

justified by the manufacturer as needed for engine protection. Additionally, the proposal 

would include a provision for some AECDs to be approved as not-to-exceed 

deficiencies and for any such AECDs to be automatically excluded from being 

considered an EI-AECD. In the rare instance (if any) that there is an EI-AECD that is 

justified as needed for engine protection but it actually is comprised of no sensed, 

calculated, or measured value and no corresponding commanded action by the onboard computer to act differently as a result, it would also be excluded from being 

tracked as an EI-AECD. Lastly, AECDs that are only invoked solely due to any of the 

following conditions would be excluded from being considered and EI-AECD: (1) 

operation of the vehicle above 8000 feet in elevation; (2) ambient temperature; (3) while 

the engine is warming up and cannot be reactivated once the engine has warmed up in 

the same driving cycle; (4) failure detection (storage of a fault code) by the OBD 
53

system; (5) execution of an OBD monitor; or (6) execution of an infrequent regeneration 

event. 

For those strategies that meet all the requirements above to be considered an 

EI-AECD, the on-board computer would be required to log cumulative time each one is 

active and update the stored counter at the end of each driving cycle with the total 

cumulative time during the driving cycle. Further, each EI-AECD would be counted and 

reported separately (EI-AECD #1, etc.). ARB staff would be able to use this data to 

confirm or refute previous assumptions about expected frequency of occurrence in-use 

and use the data to support modifications to future model year applications and better 

ensure equity among all manufacturers. This data will also help ARB staff identify “frail” 

engine designs that are under-designed relative to their competitors and inappropriately 

relying on EI-AECD activation to protect the under-designed system. 

Manufacturers have raised several concerns regarding this required tracking including 

technical concerns, confidentiality concerns, and the inappropriateness of including 

such a requirement in the OBD regulations. Regarding technical concerns, 

manufacturers have argued that determination of which AECDs are emission-increasing 

will require additional emission testing time. However, as was done with the same 

requirements in the OBD II regulation, staff has defined emission-increasing as reducing 

the emission control system effectiveness and thus, made the determination based on 

engineering analysis, not any emission test data. Industry has also argued that many 

EI-AECDs have varied levels of emission increase and they are not simple on/off 

switches, thereby complicating the counting process and making no distinction between 

items with a large emission impact and those with only a minor emission impact. To 

address this, staff split tracking of each EI-AECD that is not a simple on-off decision into 

two separate timers to separately track time spent with “mild” EI-AECD activation 

(defined as action taken up to 75 percent of the maximum action that particular EIAECD can take) and “severe” EI-AECD activation (defined as action taken from 75 to 

100 percent of the maximum action that particular EI-AECD can take). As an example, 

an EI-AECD that progressively derates and eventually shuts off EGR when the engine 

overheats would be tracked in the “mild” timer for time spent commanding EGR derating 

of 1 to 75 percent and tracked in the “severe” timer for time spent commanding EGR 

derating of 75 to 100 percent (fully closed). For EI-AECDs where it is harder to 

determine the 75 percent point (e.g., strategies that activate two different actions of 

varying levels), manufacturers would be required to present a plan for tracking the 

timers for ARB approval to ensure that the action that has the most impact on emissions 

is accurately accounted for. 

Manufacturers have also expressed concern about the complexity of tracking two EIAECDs that may be overlapping and both commanding action. After further discussion 

with individual manufacturers about how their strategies were structured, staff modified 

the proposal to require independent tracking of each unique EI-AECDs (defined as a 

combination of parameter used to trigger the action, state/value of the parameter that 

actually triggers the action, and commanded action) and not require the software to 

decipher which of the overlapping EI-AECDs was actually having the bigger impact and 
54

only accumulate time in that counter. Additional modifications are also being proposed 

to further clarify how different types of EI-AECDs are required to be tracked. 

Regarding confidentiality, manufacturers have indicated that their algorithms and 

strategies that comprise their EI-AECDs are extremely confidential and they do not want 

their competitors to know the details. Manufacturers have indicated that they believe 

staff’s proposal would provide competitors with more detail of their EI-AECDs and make 

reverse-engineering easier. Staff’s proposal, however, does not provide any additional 

information to make it easier to reverse-engineer a competitor’s strategies nor does it 

provide any detail about the strategies or algorithms used. The only data staff’s 

proposal would make available is cumulative time an engine is operated with a specific 

numbered EI-AECD active (e.g., EI-AECD #6). Only the certifying manufacturer and 

ARB would know for any particular engine what strategy or algorithm a particular EIAECD corresponded to. Further, since the cumulative time data is only updated at the 

end of a drive cycle, a competitor could only ascertain that, at some previous time in the 

operation of this engine, a particular EI-AECD was activated a cumulative amount of 

time. The data would not indicate at what specific time(s) during any previous drive 

cycles the EI-AECD was active, whether it was active for one long period or many short 

bursts of time, or the severity of the action (or even what action) was taken during the 

EI-AECD activation. As can be done today, a manufacturer would be better served 

emission testing the engine, identifying real time spikes in emissions, and analyzing the 

engine operating conditions where the spikes actually occurred to reverse engineer his 

competitor’s products rather than looking at data that does not tell him when the actual 

activation may have occurred. Lastly, given that the only items of discussion here are 

EI-AECDs justified by the need to protect the engine, a manufacturer’s desire for 

confidentiality can be motivated by only one concern—that it is currently activating an 

EI-AECD (and thus, protecting its engine) during conditions that its competitors are not 

(and thus, not equally protecting their engine) thereby giving the manufacturer a 

competitive advantage in engine durability. By definition, this means that the 

manufacturer is activating its EI-AECDs more often (in conditions where its competitors 

are not). But this is also some of the very same inequity that ARB staff struggle to 

eliminate in certification in cases where a manufacturer is overly conservative in 

concluding engine “protection” is necessary and/or staff use to distinguish a “frail” 

engine design relative to competitors’ engines. 

G. SERVICE INFORMATION REQUIREMENTS 

The heavy-duty OBD regulation currently contains requirements for service information 

that heavy-duty manufacturers are required to make available to the repair industry, 

which were not included in the stand-alone service information regulation, Cal. Code 

Regs., title 13, section 1969, at the time the heavy-duty OBD regulation was adopted in 

2005. Thus, the heavy-duty OBD regulation currently details requirements for heavyduty manufacturers to provide basic information including OBD monitor descriptions, 

information necessary to execute each monitor (e.g., enable conditions), and 

information on how to interpret the test data accessed from the on-board computer. 

Additionally, it requires manufacturers to make available repair procedures for OBD 
55

faults that either only require the use of a generic scan tool or require the use of a nongeneric scan tool as long as they make information available to the aftermarket scan 

tool industry to manufacture their own tools to perform the same functions. 

Furthermore, it includes language that clarifies that the stand-alone service information 

regulation, to the extent it is effective and operative, supersedes any redundant service 

information requirement in the heavy-duty OBD regulation. In 2006, section 1969 was 

updated to include OBD information manufacturers are required to make available for 

heavy-duty vehicles, including requirements to make available to independent service 

facilities service tools to access the OBD information. Thus, the heavy-duty industry 

has requested that the service information requirements in the heavy-duty OBD 

regulation be deleted. 

However, the updated detailed requirements in section 1969 only apply to 2013 and 

subsequent model year heavy-duty engines, while enhanced OBD systems are required 

on some 2010 through 2012 model year heavy-duty engines under the heavy-duty OBD 

regulation. For model years prior to 2013, section 1969 only requires heavy-duty 

manufacturers to make available information and tools they already currently provide to 

dealers and independent facilities. Thus, since heavy-duty manufacturers currently do 

not provide information regarding manufacturing of scan tools to perform the same 

functions as the non-generic scan tools, staff interpreted the requirements in section 

1969 as saying heavy-duty manufacturers are not obligated to provide this information 

for the 2010 through 2012 model year engines. Accordingly, section 1969 is not 

redundant to the service information requirements of the heavy-duty OBD regulation 

and does not automatically supersede it. Further, with such a position, manufacturers 

could provide access only for their authorized dealers to the heavy-duty OBD fault 

information and deny access to all independent repair facilities. Given the intent of the 

heavy-duty OBD system is to achieve early identification of the presence of a 

malfunction and prompt repair, it would be inappropriate to allow manufacturers to 

restrict access only to authorized dealer facilities. Therefore, ARB staff is not deleting 

the current service information requirements in the regulation as manufacturers 

suggested to prevent this problem for 2010 through 2012 model year heavy-duty 

engines with OBD systems. These requirements are important to prevent the heavyduty OBD program from getting off to a bad start. If repairs of OBD-related malfunctions 

can only be done by dealers (and not independent service facilities) during these first 

few years of heavy-duty OBD implementation, the overall intent of the program will be 

undermined and it could jeopardize the future acceptance of the system by the repair 

industry. 

Though staff is not deleting the service information requirements, it agrees that some 

clarification is needed in what exactly is required for the 2010 through 2012 model 

years. There have been different interpretations among engine manufacturers about 

the language in section 1969. As stated above, while a few (including ARB staff) 

believe the language only requires manufacturers to sell tools they “currently” make 

available to the aftermarket (which would not include tools that perform OBD-related 

diagnosis), some engine manufacturers believe that the language requires the 

manufacturers to sell their diagnostic tools that perform the OBD and emission-related 
56

diagnosis and repairs to the aftermarket industry during this timeframe. Since the 

original intent of ARB’s keeping the service information language was so that the 

aftermarket repair industry has a means to repair engines with HD OBD detected faults, 

staff agrees that this intent would be satisfied if manufacturers are indeed required to 

sell their tools to non-dealer repair facilities during this timeframe (which most of 

industry already says they are required to do). Thus, staff modified the service 

information language in the HD OBD regulation to make sale of a manufacturer’s 

service tool to non-dealers a clear option for compliance. 

 

V. PROPOSED REVISIONS TO HEAVY-DUTY OBD DEMONSTRATION TESTING 

REQUIREMENTS 

Manufacturers are required to design and calibrate the OBD system to detect some 

malfunctions before specific emission thresholds are exceeded at any time within the 

full useful life of the engine. Depending on the size of the heavy-duty vehicle, the useful 

life can be 110,000 miles, 185,000 miles, or 435,000 miles. The current regulation 

requires manufacturers to conduct emission demonstration testing prior to certification 

to ensure that the systems are indeed able to detect faults before the thresholds are 

exceeded. And, to ensure the emission thresholds are not exceeded for the full useful 

life, ideally, the manufacturers would age the whole system (i.e., the engine and all 

emission controls) to full useful life and then verify the calibration for each fault is 

correct. However, ARB recognizes that manufacturers have limited experience, 

resources, and time to age the engine, engine emission controls, and aftertreatment to 

full useful life prior to certification, especially for engines subject to a 435,000 mile 

useful life. Additionally, manufacturers have traditionally claimed that engines and 

engine components deteriorate very little based on past experience, and that this trend 

is expected to continue. ARB, therefore, compromised in 2005 by allowing 

manufacturers to simply ‘break-in’ the engine and engine components by aging for 125 

hours while requiring aging of only the aftertreatment to full useful life for demonstration 

tests. Further, since aging to accumulate the full mileage is time consuming, ARB also 

allows manufacturers to develop and use accelerated aging processes to simulate full 

useful life aging. Manufacturers would ideally develop and validate these processes 

with actual aged parts and are required to have these processes approved by ARB after 

a thorough review. 

Even with ARB’s compromise on the aging requirements, the manufacturers assert that 

they will not be able to create full useful life aged aftertreatment components or develop 

an accelerated aging process for the aftertreatment in time for the 2010 model year. 

Manufacturers cite the lack of time and experience in developing such a process and 

validating it with real data and the lack of experience with the new aftertreatment 

components in the field. Therefore, the manufacturers instead proposed a phase-in 

schedule that would allow for less rigorous aging to lower mileage goals in the initial 

years of implementation. Specifically, for the 2010 through 2012 model years, an 

engine manufacturer would age the aftertreatment to the level used to satisfy ARB 

certification requirements for determining the deterioration factor, whatever that 

intermediate mileage level for each manufacturer may be. For the 2013 through 2015 
57

model years, an engine manufacturer would age the aftertreatment up to 185,000 miles. 

And finally, for the 2016 and subsequent model years, an engine manufacturer would 

age the aftertreatment to the current requirement of full useful life. Additionally, the 

manufacturers proposed that the scope of the aftertreatment aging be limited to ‘key 

components’ only, specifically the diesel oxidation catalyst, diesel particulate filter, NOx 

aftertreatment catalyst, oxygen sensors, and NOx sensors. The manufacturers’ 

proposal also retained the requirement that the engine only be ‘broken-in’ with 125 

hours and aging only be required of the aftertreatment. 

After discussing engine manufacturers’ progress towards meeting the 2010 emission 

standards and OBD implementation, ARB recognized that manufacturers are further 

behind than anticipated. Thus, ARB agrees that interim relief is appropriate to allow 

manufacturers to build up the knowledge and field experience with these new 

components to understand the extent of deterioration during useful life. However, staff 

does not believe the schedule or scope of the manufacturers’ proposal really provides 

the necessary incremental steps towards a long term solution. The changes proposed 

by staff below are intended to focus on a successful long term solution and require 

manufacturers to meet interim requirements that are logical steps in the process. 

While this discussion is specific to the allowed aging during demonstration testing, it is 

important to remember that manufacturers are liable in-use for proper detection of faults 

before the OBD emission thresholds are exceeded at any time during the useful life. If 

manufacturers do not properly account for all the synergistic effects and total system 

deterioration that occurs during useful life, they risk non-compliance and recall, fines, or 

other remedial action. Thus, from ARB’s perspective, even for OBD monitor calibration 

purposes (not just demonstration testing), manufacturers need to (and are required and 

expected to) account for full useful life deterioration and base their calibration efforts on 

that. As is commonly done within the light-duty vehicle community, manufacturers are 

expected to develop engineering shortcuts and procedures to account for this full useful 

life performance. However, to be successful, these procedures have to accurately 

represent in-use deterioration and overall system performance. The only way a 

manufacturer can be sure that its procedure accurately represents in-use performance 

is to validate the systems (engine, engine component, and aftertreatment) created by 

their engineering procedures against actual full useful life (e.g., high mileage) systems. 

Based on discussions with manufacturers and suppliers as they are progressing 

towards finalizing 2010 model year system designs, ARB is especially concerned about 

engine (and component) deterioration and its synergetic effects with the aftertreatment. 

Despite manufacturers’ previous assertions that diesel engines and components 

deteriorate very little, ARB has seen fairly dramatic changes in diesel engines with 

control strategies and new components (including new EGR systems, EGR coolers, fuel 

injection system changes, turbo component changes, etc.) that operate in much more 

varied control points (e.g. near partial homogeneous charge compression ignition type 

operation with heavy EGR, tight air-fuel ratio control in specific regions). In light of such 

complicated system architecture and control strategies, previous conventions and 

knowledge about diesel engine and component deterioration no longer seem applicable. 
58

Until experience is gained with high mileage evaluations and real world experience, it 

would be inappropriate to assume past deterioration characteristics will continue on 

these new systems. With this perspective, an engine aged for 125 hours (which is 

currently required by the OBD regulation) would not likely be representative of one at 

full useful life, so calibration or demonstration testing with such an engine would not 

provide assurance of OBD compliance throughout useful life. Additionally, 

manufacturers appear to have insufficient experience and knowledge to be able to 

accurately account for or predict the cumulative aging effects of the total system by 

simply aging a few “key” components of the aftertreatment (as manufacturers have 

proposed). ARB believes the only long term solution to get compliance assurance is to 

require manufacturers to generate high mileage systems and/or to collect and use data 

from real world high mileage systems to develop and validate accelerated aging 

procedures for the entire system (i.e., the engine, engine components, and 

aftertreatment system). 

Thus, while agreeing that interim relief with lower aging mileage goals is appropriate, 

ARB is proposing to revise the requirements with a phase-in schedule containing higher 

interim goals than those proposed by the manufacturers. Additionally, for the reasons 

stated above, ARB believes that total system aging (engine plus the aftertreatment 

system) must be considered and is revising the requirements to achieve that in the long 

term. 

For the 2010 to 2012 model years, the proposed changes would continue to allow the 

use of an engine aged for 125 hours. However, in lieu of requiring the aftertreatment 

system to be aged and validated as representative of full useful life, the changes would 

allow manufacturers to only age the individual aftertreatment components (e.g., PM 

filter, oxidation catalyst) and exhaust gas sensors (e.g., NOx, lambda sensors) to the 

manufacturer’s best estimates of useful life without the rigors of validation that would 

normally be required for ARB to approve the system as representative of full useful life. 

In discussions with manufacturers and suppliers, it appears fairly straightforward for 

manufacturers, in consultation with their suppliers, to identify the key aging mechanism 

(e.g., time at or above specific temperatures), to calculate expected operation over 

useful life in those key conditions, and to develop an accelerated aging process to 

condense that aging into a reasonable timeframe. Where these approaches fall short is 

in validation to real world operation that the estimates of expected operation were 

correct and/or whether other component deterioration altered the outcome. However, 

the manufacturer’s responsibility to validate the accelerated aging process would be 

waived for these model years. 

In exchange for the relaxed requirements, a manufacturer would be required to collect 

and report in-use data from 2010 or later model year engines operated in the real world. 

The data collected would be from engines and systems operated for approximately 18 

months or longer and with mileages equal to the full useful life for engines subject to 

110,000 or 185,000 mile useful life and at least 185,000 miles for engines subject to 

435,000 mile useful life. Such data collection by manufacturers would require removing 

real world aged systems (engine and aftertreatment) from vehicles, installing the 
59

systems on engine dynamometers, running various emission tests to quantify the 

system deterioration, and reporting the data to ARB late in the 2011 calendar year. For 

2013 to 2015 model year engines subject to 110,000 or 185,000 mile useful life, a 

manufacturer would be required to use the knowledge gained from the collected data to 

modify (if needed) and validate its accelerated aging processes for ARB’s approval. For 

2013 to 2015 model year engines subject to 435,000 mile useful life, a manufacturer 

would also be required to use the collected data to validate and/or modify the 

accelerated aging procedure used in 2010 to better equate to real world deterioration, 

however, the manufacturer would still be allowed to use its best estimates for full useful 

life aging as the collected data would only allow validation up to 185,000 miles and not 

to the full useful life of 435,000 miles. 

For engines subject to 435,000 mile useful life, manufacturers would additionally be 

required to collect data from 2010 or newer model year real world aged systems with 

mileage equal to 435,000 miles and report the data to ARB in the 2014 calendar year. 

Identical to the data collected at 185,000 miles, the manufacturer would be required to 

obtain high mileage systems, perform various emission tests to quantify and understand 

the deterioration, and incorporate that knowledge to refine and validate its accelerated 

aging procedures to be representative of full useful life and used for certification of 2016 

and subsequent model year systems. 

The following table summarizes the proposed requirements. 
60

Table I: Phase-in aging data requirement schedule 

for engine and aftertreatment 

Aging data required 

at certification for accelerated aging 

Year 

Engine Aftertreatment 

2010-2012 model 

year 

125 hours aging Accelerated aged to best 

estimates of full useful life on 

aftertreatment components 

Report in-use 

data in 2011 

~18 months (for light and medium HDDE, full useful life, 

for heavy HDDE,185,000+ miles) 

real world aging data on 2010 model year engines 

2013-2015 model 

year 

For light and medium HDDE: accelerated aging to full useful life 

validated with real world aging data 

For heavy HDDE: Best estimates for accelerated aging to full useful 

life incorporating 185,000 real world aging data 

Report in-use 

data in 2014 

435,000 mile full useful life real world aging data on 2010 or later 

model year engines 

2016 model year 

and after 

Accelerated aging to full useful life validated with real world aging 

data 

Manufacturers had requested that ARB adopt the same proposed procedures that U.S. 

EPA is currently developing for determining deterioration factors (DFs) in lieu of staff’s 

proposal. Specifically, U.S. EPA’s plan would require manufacturers to do partial aging 

of the engines (i.e., not require aging to full-useful life) and extrapolation of the emission 

data to determine the projected emission levels at full useful life. While partial aging 

may be appropriate for determining the likely emission levels of non-malfunctioning 

engines at useful life, it is not appropriate for projecting emission levels of engines with 

emission-related malfunctions. As previously stated, manufacturers are liable in-use for 

proper detection of faults before the OBD emission thresholds are exceeded at any time 

during the full useful life. To accurately determine how high emissions will be when a 

malfunction occurs, the performance level of the engine and aftertreatment system aged 

to full useful life must be taken into consideration. For example, to accurately calibrate 

an EGR system monitor to the emission threshold, the manufacturer must know how 

much of the increased engine-out NOx emissions caused by a malfunctioning EGR 

system is going to be cleaned up by the downstream SCR system at full useful life. 

This determination cannot be “extrapolated” by implanting a fault at low mileage and 

measuring the reaction of a low mileage SCR system. Accordingly, staff has rejected 

the manufacturers’ suggestion to mimic EPA’s DF determination process and continue 
61

down the path of requiring manufacturers to develop validated rapid aging procedures 

to simulate full useful life aging. 

In addition to the aging requirements, staff is also proposing modifications to the 

malfunction simulation methods. Currently, the regulation allows manufacturers to 

electronically simulate malfunctions (e.g., use of an external simulator) but does not 

allow them to make modifications to the electronic control unit (on-board computer) 

except for a few limited monitors. In general, staff has severely limited the use of 

internal computer modifications because it results in special software (non-production 

intent) to run the demonstration tests and increases the risk that the system will perform 

differently with the special software than it would with the actual production intent 

software. However, given the wide variety of technologies and strategies being 

implemented by diesel manufacturers, staff believes there may be additional cases that 

arise where it is not technically feasible or very expensive, difficult, and resourceintensive to implant faults through hardware or an external simulator. Accordingly, the 

proposal includes a provision for manufacturers to request and receive ARB approval to 

use internal computer modifications for additional monitors upon demonstration or 

analysis that it is infeasible or disproportionally difficult and resource intensive to implant 

the fault externally. Further, the proposal clarifies that, in cases where a manufacturer 

elects to electronically simulate a fault through an external simulator or internal 

computer modifications, the manufacturer must demonstrate that the failure 

characteristics produced by the simulation are equivalent to an induced hardware 

failure. This ensures that manufacturers are calibrating and designing the monitor to 

detect failures that are related to actual hardware malfunctions and not purely 

theoretical or idealized simulations of a fault. 

Staff is also proposing modifications concerning the actual testing process. The current 

requirements were primarily copied from the test procedure for light-duty vehicles, 

however, recent discussions with manufacturers have revealed some fundamental 

differences in how heavy-duty emission tests are run. Unlike light-duty, the heavy-duty 

test procedure does not include a ‘preconditioning’ cycle the day before the emission 

test. To be consistent with the current heavy-duty test procedures and to eliminate 

unnecessary extra testing, the proposed amendments would eliminate the 

preconditioning cycle and require manufacturers to implant the fault and immediately 

perform the emission test. Further, because the previous test procedures anticipated 

the use of a preconditioning cycle, the procedure expected that the fault would be 

detected once during the preconditioning cycle and a second time during the first engine 

start of the emission test. In conjunction with eliminating the preconditioning, the 

language was modified to expect the fault to be first detected on the first engine start of 

the emission test and detected a second time during the second engine start of the 

emission test. The proposed language does still allow a manufacturer to request 

approval to use preconditioning cycles if technically justified to stabilize the emission 

control system. While manufacturers have not yet identified a need for this provision, it 

will be in place in case future emisison controls require such stabilization. 
62

Lastly, staff is also proposing modifications to the data collected during demonstration 

testing. The current regulatory language requires specific fault information (i.e., time 

after start when the MIL illuminated, fault code(s), freeze frame information, test results) 

to be collected. Staff is proposing that manufacturers also be required to collect other 

OBD electronic information as well, including readiness status, current data stream 

values, CAL ID, CVN, VIN, in-use performance ratios, and engine run time tracking 

data. Furthermore, staff is also proposing that manufacturers be required to collect all 

the test data immediately prior to or after each engine shut-down, such as at the end of 

the preconditioning cycle (if used), cold start FTP cycle, and warm start FTP cycle. By 

analyzing this data when reviewing the demonstration test results, staff will be able to 

better understand the scenario of events and ensure that the standardized data is 

outputting expected values during the test sequence. Historically, in testing done at 

ARB’s facility, review of such data has identified many other small issues and having 

this data at the time of certification would allow identified issues to be corrected sooner. 

VI. PROPOSED REVISIONS TO HEAVY-DUTY OBD CERTIFICATION 

REQUIREMENTS 

A. CERTIFICATION APPLICATION 

Based on the staff’s review of manufacturers’ OBD II applications in the past years, 

minor changes are being proposed to the HD OBD certification submittal requirements 

to expedite the OBD review and approval process. Specifically, the proposed 

amendments would require some information, including a checklist, the summary table, 

and misfire monitor disablement data, to be submitted in a standardized format that will 

be detailed in a future ARB mail-out to facilitate consistent and quick review by staff (the 

specific mail-out number will be made available at the Board Hearing and as part of the 

subsequent 15-day changes to the regulations). Staff is also proposing to require 

manufacturers to submit data supporting their infrequent regeneration adjustment 

factors and information regarding EI-AECDs. Lastly, the staff is also proposing to 

require manufacturers to include a cover letter with each OBD application identifying the 

deficiencies and concerns (if any exist) that apply to the equivalent engine family or 

OBD group in the previous model year and the changes and/or resolution of each 

concern or deficiency for the current model year. This would allow the ARB staff to 

spend less time determining if past problems have been corrected. 

B. IN-USE COMPLIANCE TESTING 

As a condition for certification, manufacturers would be required to perform in-use 

compliance testing on their own engines. The actual procedures are detailed in the 

proposed enforcement regulation (§1971.5) and would require manufacturers to procure 

actual in-use engines, at roughly 75 percent of full useful life mileage, and perform a 

series of engine dynamometer emission tests to confirm the OBD system will detect 

faults at the emission levels specified in the HD OBD regulation (§1971.1). ARB has 

previously adopted similar requirements for manufacturers to do their own in-use 

compliance testing. This includes the “CAP 2000” program adopted for light-duty 
63

vehicles that sets forth in-use compliance requirements and procedures in the test 

procedures incorporated by Cal. Code Regs., title 13, section 1961 and requires 

manufacturers to procure in-use vehicles, at various mileages, and perform emission 

tests to verify compliance with the tailpipe standards established in section 1961. It also 

includes the heavy-duty on-road manufacturer in-use compliance testing program in test 

procedures incorporated by Cal. Code Regs., title 13 sections 1956.1 and 1956.8 that 

requires manufacturers to procure in-use vehicles, equip them with emission 

measurement devices, and collect emission data to verify compliance with the not-toexceed (NTE) tailpipe standards established in sections 1956.1 and 1956.8. Cal. Code 

Regs., title 13, section 2438 establishes a manufacturer in-use testing program for large 

spark-ignition engines with greater than 1.0 Liter displacement. Similar to what is 

proposed for HD OBD compliance, this program requires manufacturers to procure a 

number of in-use engines with a minimum mileage, perform emission tests to verify 

compliance with the established tailpipe standards, perform further testing if initial tested 

engines fail, and ultimately, generate sufficient data to determine if the engines do not 

comply and if remedial action is warranted. Another similar program exists for sparkignition engines used in personal watercraft and outboard marine engines in Cal. Code 

Regs., title 13, section 2444.1 and requires manufacturers to procure in-use engines 

and perform emission testing to verify compliance with the established emission 

standards. Further, in the HD OBD (§1971.1(l)) and the OBD II (§1968.2(j)) regulations, 

manufacturers are also required to do other forms of production vehicle or engine 

evaluation testing to confirm various elements of their OBD systems comply with the 

certification standards and procedures established within the regulations themselves. 

In all of the above examples, the requirements are indeed mandatory requirements that 

apply to the manufacturers of applicable vehicles and engines. EMA has argued that 

the heavy-duty in-use compliance program is not a valid confirmation of ARB's authority 

to adopt similar requirements for HD OBD compliance because manufacturers agreed 

to do such testing during discussions and settlements in 1998 that ended with consent 

decrees to resolve engines produced in the 1990's that allowed the engines to comply 

with emission limits under certification conditions but caused significantly higher NOx 

emissions during highway driving. However, not all engine manufacturers were part of 

the settlements and consent decrees yet all manufacturers are now required to do the 

in-use compliance testing. In any case, this and the other programs cited above are not 

optional requirements or voluntary agreements entered into by the manufacturers with 

ARB. It is both consistent with past and current practice of ARB to have manufacturers 

do some form of self-testing for verifying compliance with adopted standards. 

VII. PROPOSED REVISIONS TO HEAVY-DUTY OBD STANDARDIZED METHOD TO 

MEASURE REAL WORLD MONITORING PERFORMANCE 

Currently, the HD OBD regulation requires manufacturers to track monitor performance 

by counting the number of monitoring events and the number of driving events. The 

number of monitoring events is defined as the numerator and the number of driving 

events is defined as the denominator. The ratio of these two numbers is referred to as 

the monitoring frequency and provides an indication of how often the monitor is 
64

operating relative to vehicle operation. It is important to note that the denominator is a 

measure of vehicle activity, not a measure of “monitoring opportunities”. The regulation 

requires manufacturers to design monitors that meet a minimum acceptable ratio, 

currently set at 0.1 for 2013 and subsequent model year engines. 

The current requirement for incrementing the general denominator is: 

1.) minimum engine run time of 10 minutes; 

2.) minimum of 5 minutes, cumulatively, of vehicle operation at vehicle speeds 

greater than 25 miles-per-hour (mph) for gasoline engines or calculated load 

greater than 15 percent for diesel engines; and 

3.) at least one continuous idle for a minimum of 30 seconds encountered; and 

the above three conditions met while: 

4.) ambient temperature above 20 degrees Fahrenheit and 

5.) altitude of </= 8000 feet. 

Industry has expressed concerns that some monitors may not execute on the 

denominator drive cycle defined above and, therefore, some vehicles may exhibit poor 

in-use ratios. However, industry has erroneously reached the conclusion that the 

denominator represents a drive cycle during which all monitors must be executed. On 

the contrary, manufacturers are not required to design monitors to execute during the 

denominator drive cycle but are required to design robust monitors that perform 

frequently in-use. Monitors are designed to run when specific engine operating 

conditions are met—not when a specific drive cycle is met—and the occurrence of 

those conditions happens independent of whether a denominator drive cycle is met. 

For example, a case may exist where a monitor never executes on the denominator 

cycle but the minimum in-use frequency ratio may still be satisfied because the monitor 

executes frequently on other drive cycles. The purpose of the denominator is not to 

provide industry with a drive cycle by which to run all monitors but to provide ARB with a 

measure of vehicle activity. 

Additionally, industry has requested changes in the definition of the denominator drive 

cycle. When the HD OBD regulation was adopted in 2005, diesel engine manufacturers 

indicated that they did not always have access to vehicle speed and thus, could not 

determine when a vehicle had spent five cumulative minutes above 25 mph. As an 

alternative, they proposed, and ARB accepted, five minutes above 15 percent engine 

load for diesel engines. At this time, however, diesel engine manufacturers have now 

indicated that 15 percent engine load is not a consistent indicator from engine to engine, 

since it could be satisfied at idle on some engines while it is satisfied with operation 

somewhere above 25 mph on other engines. Diesel engine manufacturers now 

propose greater than 50 percent calculated load for five cumulative minutes in lieu of 

greater than 15 percent for five cumulative minutes. Further, for those engines that do 

have access to vehicle speed, industry has requested permission to alternatively use 

the gasoline engine parameter of greater than 25 mph for five cumulative minutes on 

diesel engines in lieu of the greater than 15 percent load. 
65

Regarding the denominator drive cycle, ARB’s objective is to provide a common 

definition because manufacturers will be held to the same minimum in-use frequency 

ratio based on this definition and the use of different definitions would lead to inequity 

among manufacturers. Under the current regulation, while gasoline and diesel engines 

do not use the same definition, all diesels are required to use a consistent definition and 

all gasoline are required to use a consistent definition. This consistency among similar 

engines is imperative to ensure equivalent stringency in requirements among 

manufacturers and must be maintained. However, staff agrees that the 15 percent 

engine load criterion is inappropriate as a consistent measure of engine work or vehicle 

activity. To address industry’s concern and maintain commonality, staff is proposing to 

change this definition to exclude the calculated load parameter and instead include five 

cumulative minutes of engine speed at or above 1150 rpm for diesel engines. Staff 

believes 1150 revolutions-per-minute (rpm) represents an engine speed above idle in 

virtually all engines and is a positive indicator that the engine is being used to do work 

(e.g., move the vehicle, operate a substantial power take-off unit). Many engines have 

peak torque that occurs at 1200 rpm and above and most manufacturers’ engines are 

subject to the not-to-exceed emission standard at engine speeds above 1150 to 1200 

rpm. And, whenever the engine is doing work, it is vital that the emission controls are 

working properly so basing an in-use monitoring frequency relative to how often the 

engine is being used to do work is appropriate. Further, all manufacturers have access 

to engine speed and could accurately determine when this criteria was satisfied. With 

the 2010 model year production fast approaching, however, staff believes some lead 

time is necessary and is allowing 2010 through 2012 model year diesel engines to use 

the 15 percent calculated load criterion. Additionally, to maintain consistency of the 

denominator definition and equality among manufacturers, staff does not agree with 

manufacturers’ request to optionally use the vehicle speed criterion in lieu of the engine 

speed or load criterion. 

In addition to the proposed changes to the general denominator definition above, staff is 

proposing a separate denominator for PM filter monitoring. Currently, the regulation 

allows manufacturers to submit proposed criteria for incrementing the PM filter monitor 

denominator for ARB approval. Since the adoption of the requirement, staff has gained 

enough knowledge from discussions with engine manufacturers to propose specific 

criteria for the PM filter monitor, which engine manufacturers have indicated will most 

likely be tied to PM filter regeneration events. Thus, in addition to meeting the general 

denominator on at least one driving cycle, staff is proposing that the PM filter 

denominator be incremented after 750 minutes of cumulative engine run time. The 

basis for 750 minutes is calculated starting from a 300-500 mile interval that industry 

has indicated is typical of distance between PM filter regenerations and assuming an 

average vehicle speed of 40 mph (500 miles / 40 mph = 12.5 hours = 750 minutes). 

The proposed revised definition for the general rate-based denominator for diesel 

engines is: 

1.) minimum engine run time of 10 minutes; 
66

2.) minimum of 5 minutes, cumulatively, of engine operation with engine speed at 

or above 1150 rpm; and 

3.) at least one continuous idle for a minimum of 30 seconds encountered; and 

the above three conditions met while: 

4.) ambient temperature above 20 degrees Fahrenheit and 

5.) altitude of </= 8000 feet. 

The proposed definition for the PM filter rate-based denominator is: 

1.) minimum of 750 minutes of cumulative engine run time since the last time the 

PM filter denominator was incremented and 

2.) meeting the above requirements for the general denominator on at least one 

driving cycle. 

For the PM filter denominator, the proposed language also provides clarification 

regarding tracking the order of events when determining the criteria have been met. 

Specifically, the language identifies methods to first identify on a particular key start if a 

general denominator has been satisfied and subsequently to then determine if the 

cumulative engine run time has been satisfied. The language also provides direction to 

manufacturers on when the cumulative engine run time counter must be restarted. 

Staff is also proposing to modify the definition of “idle” operation (which is also referred 

to in the permanent fault code erasure requirements and the standardization tracking 

requirements of the regulation). “Idle” operation is currently defined as conditions where 

vehicle speed is less than or equal to one mph, among other criteria. As indicated 

above, some manufacturers have indicated that their engines do not utilize vehicle 

speed information and thus, cannot sense vehicle speed. They further indicated that 

engine speed is an acceptable surrogate to use to determine idle operation. Thus, ARB 

is proposing to define idle operation as conditions where, among other criteria, either 

the vehicle speed is less than or equal to one mph or engine speed is less than or equal 

to 200 rpm above the normal warmed-up idle speed. 

VIII. PROPOSED REVISIONS TO OBD II REGULATION 

At the request of medium-duty diesel manufacturers in order to maintain consistency 

between the HD OBD and OBD II diesel requirements, staff is proposing to carry over 

almost all of the proposed diesel-related changes mentioned above for the HD OBD 

regulation to the OBD II regulation, applying them to light- and medium-duty diesel 

vehicles. The only difference between what would be proposed for light-duty diesel 

vehicles versus medium-duty diesel vehicles is that any of the proposed changes 

related to modification of the specific malfunction emission threshold values would only 

apply to the medium-duty diesel vehicles. The specific proposed changes to the OBD II 

regulation can be found in Attachment B. 

Additionally, staff is proposing one change to the gasoline monitoring requirements in 

the OBD II regulation concerning the phase-in schedule for primary oxygen sensor 
67

response rate monitoring data submission. Currently, manufacturers are required to 

submit data and/or engineering analysis to demonstrate that their oxygen sensor 

monitors are able to detect all asymmetric and symmetric response rate malfunctions 

with a phase-in starting with the 2010 model year. However, recent discussions with 

manufacturers indicate that more time is needed to meet this requirement. Thus, staff is 

delaying the start of the phase-in from the 2010 model year to the 2011 model year, 

with all vehicles required to meet this requirement for the 2013 and subsequent model 

years. 

IX. PROPOSED HEAVY-DUTY OBD ENFORCEMENT REGULATION 

A. OVERVIEW 

The staff is proposing that the Board adopt a comprehensive in-use enforcement 

protocol that applies specifically to the HD OBD requirements (Cal Code Regs., title 13, 

§1971.1), pursuant to the Board’s general and specific authority to adopt procedures 

that ensure compliance.2

 The proposed HD OBD enforcement provisions would help 

ensure the effectiveness of the HD OBD regulation and the underlying more stringent 

emission standards that have been adopted for 2010 and subsequent model year heavy 

duty engines. Among other things, the staff is proposing procedures for the in-use 

testing of HD OBD systems installed on heavy-duty engines. The proposal would 

further provide the Executive Officer with authority to order engine manufacturers to 

take remedial action when in-use testing indicates that an HD OBD system within an 

identified engine class does not meet the certification requirements of Cal. Code Regs., 

title 13, section 1971.1. 

The staff believes that specific HD OBD enforcement provisions are necessary to better 

address and identify the special circumstances involved in in-use testing and remedying 

identified nonconformities with HD OBD systems. Past experience in light- and 

medium-duty revealed that the general enforcement procedures (Cal. Code Regs., title 

13, §2111-2135), which were specifically adopted to enforce noncompliance with 

tailpipe and evaporative emission standards, do not allow for effective enforcement of 

OBD requirements and standards. The general enforcement procedures do not neatly 

apply to OBD regulations for two main reasons. First, the OBD regulations include both 

emission standards and other non-emission-related requirements, such as test 

procedures and standardization requirements. Second, OBD systems are 

comprehensive and exceedingly complex; and, consequently, in-use enforcement of 

OBD systems involves a myriad of issues that do not arise in the enforcement of tailpipe 

and evaporative emission standards. Over time, it became apparent that the simplified 

general enforcement approach used for tailpipe noncompliance did not adequately 

address the unique issues involved in the in-use operation of OBD systems. 

In 2002, the Board adopted stand-alone specific enforcement procedures for the OBD II 

requirements (codified at Cal. Code Regs., title 13, §1968.5). Since adoption of the 

 

2

 Health and Safety Code, sections 39600, 39601, 43013(b), 43018, 43102, 43104, and 43105. 
68

enforcement regulation, ARB has applied its detailed protocols in addressing OBD II 

noncompliance. In general, the procedures provide for straight-forward evaluation and 

remediation (where necessary) of complex, OBD II-specific in-use issues. The detailed 

protocols have also provided clear direction to manufacturers as to the procurement, 

testing, sampling, and evaluation criteria that ARB staff uses to determine compliance 

with the OBD II requirements and has eliminated many uncertainties for manufacturers 

related to the procedures that ARB will follow in carrying out enforcement and the 

criteria ARB will use in determining compliance and appropriate corrective action. 

Further discussion about the need for an OBD specific enforcement procedure can be 

found in the staff report for the 2002 OBD II Board hearing available at ARB’s website 

(http://www.arb.ca.gov/msprog/obdprog/pastregs.htm) and incorporated by reference. 

During the 2005 HD OBD rulemaking process, staff indicated its intent to return to the 

Board with a proposal to adopt similar independent enforcement provisions for HD 

OBD. To that end, staff is now proposing adoption of section 1971.5, which would 

establish enforcement procedures and requirements for heavy-duty engines with HD 

OBD systems. It is ARB staff’s goal that the regulation becomes effective prior to 

implementation of HD OBD system requirements, which commence with the 2010 

model year. 

The proposed HD enforcement procedures are similar in comprehensiveness to those 

currently required for light-duty and medium-duty vehicles under the OBD II regulation. 

Both regulations include performance testing of emission-related monitors, downloading 

of data of in-use performance monitoring ratios, and evaluation of other OBD 

requirements (e.g., diagnostic connector location, communication protocol standards, 

MIL illumination protocol, etc.). But there are distinct differences, primarily because 

heavy-duty engines are certified on engine dynamometers and the testing of emissionrelated monitors on HD OBD systems will require the removal of engines from in-use 

vehicles for testing. Accordingly, the proposed regulation provides that, in addition to 

ARB-initiated enforcement testing, engine manufacturers will be responsible for 

compliance self-testing of OBD systems to ensure that the systems in-use actually meet 

certification requirements. 

One of the reasons manufacturer self-testing is necessary is because of the uniqueness 

of engine dynamometer testing. Unlike chassis dynamometer testing of the complete 

vehicle as is done in light-duty and can easily be replicated by ARB, manufacturers, and 

independent laboratories, engine dynamometer set-up and testing differs for each 

engine and involves the use of custom parts, modifications, and configurations. 

Because the engine is removed from the vehicle, various inputs and outputs to the 

engine control computer must be generated to simulate operation in a vehicle. Further, 

many engine components especially heat exchangers like the radiator, charge air 

cooler, and EGR cooler that rely on outside airflow (that would occur through the front of 

the engine compartment while driving on the road) must be removed and simulated 

because there is no comparable source of outside airflow in the test cell. Such 

simulations vary from manufacturer to manufacturer and engine model to engine model 

because they must duplicate the performance applicable to those components for that 
69

particular engine in a specific vehicle type. Some manufacturers have also indicated 

that certain software functions or features within the engine control unit must be 

disabled during engine dynamometer testing to prevent abnormal operation due to 

specific engine dynamics that occur during testing and disablement of such features 

requires manufacturer-specific tools and hardware to implement. Without intimate 

knowledge of all the individual component specifications and input and output signals, 

not to mention custom hardware and software to replace the removed components, or 

tremendous reliance on the voluntary cooperation and resources of the engine 

manufacturer, successful engine dynamometer testing is very difficult to perform. 

Engine manufacturers, who routinely perform engine dynamometer testing of their own 

engines, including testing for research, development, and tailpipe certification, have, by 

definition, the knowledge and equipment necessary to perform engine dynamometer 

testing. 

B. THE NEED FOR HD OBD-SPECIFIC ENFORCEMENT PROCEDURES 

The staff believes that specific HD OBD enforcement provisions are necessary to better 

address and identify the special circumstances involved in in-use testing and remedying 

identified nonconformities with HD OBD systems. As stated, experience with OBD II 

has revealed that the existing general enforcement procedures, which were specifically 

adopted to enforce noncompliance with tailpipe and evaporative emission standards, do 

not allow for effective enforcement of OBD requirements and standards. For example, 

the adoption of OBD II-specific enforcement provisions helped clarify that a 

manufacturer cannot escape liability for failing to comply with the OBD II standards and 

requirements by demonstrating that vehicles with the nonconforming OBD II system, on 

average, comply with certification standards for tailpipe and evaporative emissions. The 

OBD II emission standards and requirements serve very different purposes from the 

tailpipe and evaporative emission standards, and compliance with the latter two 

standards should not excuse noncompliance with the former. 

As with OBD II, to allow a heavy-duty engine manufacturer to overcome the need to 

remedy a nonconforming HD OBD system by showing that the failure would not result in 

the engine class, on average, to fail to conform to the tailpipe emission standards would 

undermine the purpose and intent of the 

HD OBD requirements. In adopting the HD OBD regulation, the Board specifically 

determined that functional OBD systems were necessary and should be equipped on all 

heavy-duty engines in the future. In so determining, the Board found that functional 

OBD systems are a vital complement to the success of the ARB’s heavy-duty engine 

emission reduction programs. The HD OBD system is intended to insure that 2010 and 

subsequent model year engines meet the adopted tailpipe emission standards in-use. 

The HD OBD systems are there to ensure that forecasted emission reductions will be 

achieved, and the proposed enforcement provisions are necessary to ensure that the 

adopted HD OBD requirements are fully effective in-use. 

C. AUTHORITY TO ADOPT ENFORCEMENT PROCEDURES 
70

Depending upon the nature of the nonconformity of the HD OBD system and the 

circumstances surrounding the nonconformity, recall may be an appropriate remedy. 

Health and Safety Code section 43105 authorizes the Executive Officer to order recalls, 

if a manufacturer has violated emission standards or test procedures and has failed to 

take corrective action. The HD OBD regulation, Cal. Code Regs., section 1971.1, 

establishes both emission standards and test procedures for certification to those 

standards. The ARB expressly adopted the HD OBD regulation pursuant to authority 

granted by the Legislature to adopt and implement emission standards and test 

procedures under the Health and Safety Code.3 In 2000, in adopting Senate Bill 1146, 

the Legislature expressly recognized ARB’s authority to adopt OBD regulations, finding 

that OBD requirements are emission standards, stating: 

Recent emission standards adopted and implemented by the State Air 

Resources board for motor vehicles manufactured after 1993 have resulted in the 

development by vehicle manufacturers of “on board diagnostic computers” that 

interface with the many component parts of a vehicle’s emission control system. 

(Stats. 2000, Ch. 1077, Sec. 1; emphasis added.) 

Similarly, in granting California a waiver of federal preemption for the 

OBD II regulation, pursuant to section 209(b) of the federal Clean Air Act, the 

U.S. Environmental Protection Agency (U.S. EPA) expressly found that the 

requirements of the California OBD II regulation were emission standards, 

stating. 

OBD requirements appear to be closer in their application and effect to 

standards than to enforcement procedures: they establish specific levels 

of emissions that beyond which the MIL must be illuminated and fault 

codes be stored; they create direct requirements on the manner in which 

manufacturers build their vehicles; the OBD II requirements set forth how 

a vehicle must operate at time of certification and in use, and not how the 

state would ensure that the vehicle is operating properly as is typical of an 

accompanying enforcement procedure. 

Beyond being emission standards, the HD OBD regulation sets forth specific test 

procedures that manufacturers must follow to assure certification and compliance to the 

established standards. Accordingly, Health and Safety Code section 43105 expressly 

authorizes the ARB to adopt regulations regarding corrective actions, including recall, 

that the Board may take for violations of the OBD II emission standards and the test 

procedures established to certify vehicles to those standards. 

In addition to the express authority of Health and Safety Code section 43105 to adopt 

enforcement procedures, the Board has unmistakable implied authority to adopt such 

regulations. The general powers granted to the Board in Health and Safety Code 

section 39600 provide that the Board shall do such acts as may be necessary for the 

proper execution of the powers and duties granted to it. The OBD II requirements were 

 

3

 See Health and Safety Code §§ 43013, 43018, 43101, 43104, and 43105. 
71

adopted pursuant to general authority granted under sections 43013, 43018, and 43101 

among others. Specifically, sections 43013(a) and 43101 authorize the Board to adopt 

and implement motor vehicle emission standards. And section 43018 directs the Board 

to take whatever actions are necessary, cost-effective, and technologically feasible in 

order to achieve specific emission reductions, including the adoption of standards and 

regulations that will result in, among other things, reductions in motor vehicle in-use 

emissions through improvements in emission system durability and performance. 

Although the Legislature did not expressly authorize the adoption and implementation of 

OBD II requirements, the Legislature recently gave its imprimatur to the regulation.4 

Having implicitly authorized the Board to adopt the OBD II regulations in furtherance of 

the Board’s mission, it cannot reasonably be argued that the Legislature has not also 

entrusted the Board with authority to properly enforce the adopted standards and test 

procedures to ensure compliance.5 

Such authority would extend to the requirements discussed below that require 

manufacturers to self-test HD OBD emission threshold monitors so long as those 

requirements do not impose a significant economic burden on manufacturers and are 

cost-effective. As stated manufacturers are in the best position, with specialized 

knowledge of how they tested engines for certification on the dynamometer and 

convenient access to the engine parts that enable accurate testing, to perform such 

self-testing. As explained below in the economic cost section, the enforcement selftesting provisions would not impose an excessive economic burden on manufacturers, 

and effective and accurate dynamometer testing that ensure that OBD systems work 

correctly and that forecasted emission reductions are achieved is unquestionably costeffective. 

D. SUMMARY OF THE HD OBD COMPLIANCE/ENFORCEMENT REGULATION 

1. General 

The main differences between the OBD II enforcement procedures and those proposed 

here for HD OBD involve non-compliance related to monitors exceeding the OBD 

emission malfunction thresholds (e.g., verifying that the fault is detected before 

emissions exceed 2.0 times the applicable tailpipe standard). The differences include 

the criteria that would need to be met for ARB to assume non-compliance and require 

further enforcement testing, and the specific testing procedures that would need to be 

carried out. For light-duty enforcement under the OBD II regulation, the enforcement 

protocol relied heavily on well established vehicle procurement, screening, and testing 

procedures used for tailpipe emission compliance testing. No such detailed protocol 

exists for heavy-duty OBD testing. To a large extent, the proposed procurement and 

selection process parallels the recently established procedures that EPA, ARB, and 

 

4

 See section 43105.5(a)(4), Stats. 2000, Ch. 1077, Sec. 4; see also Sec. 1. 

5

 See California Drive-In Restaurant Ass’n v. Clark (1943) 22 Cal.2d 287, 302 [140 P.2d 657], “the 

authority of an administrative board or officer, . . . to adopt reasonable rules and regulations, which are 

deemed necessary to the due and efficient exercise of the powers expressly granted, cannot be 

questioned.” 
72

manufacturers agreed to for the manufacturer self-testing for tailpipe emission 

compliance using portable emission measurement systems. 

The proposed regulation provides that ARB may conduct enforcement testing for 

emission threshold noncompliance by procuring engines from in-use vehicles and 

testing them on an engine dynamometer in accordance with the procurement, selection, 

and testing criteria noted above. ARB, however, has very limited experience with such 

testing and no existing facilities capable of conducting such testing of heavy-duty 

engines. To address this issue, the proposed regulation would also require 

manufacturers to perform self-testing for compliance on a limited number of engines 

each year. 

For each engine tested by the manufacturer, if the faults are detected prior to the 

prescribed emission levels being exceeded, the testing is completed. However, if initial 

testing indicates that the system fails to detect one or more faults before emissions 

exceed the emission thresholds of Cal. Code Regs., section 1971.1, the manufacturer 

would be required to procure, select, and test four more engines from the same engine 

family for that specific monitor. And, if two or more of the additional four engines fail, an 

additional five more engines are to be procured for testing of the failing monitor. At 

most, a manufacturer would have to test 10 engines from the same engine family. For 

both testing done by ARB and by the manufacturer, the monitor would be judged 

noncompliant if five or more of the 10 tested engines failed to detect the fault before the 

appropriate emission threshold is exceeded. 

Manufacturers have argued that it is inappropriate to require them to do their own 

compliance testing and that ARB has no authority to require them to do testing beyond 

certification. As previously indicated, staff disagrees as ARB clearly has authority to 

adopt test procedures, including in-use compliance testing, as part of the certification 

process to ensure that its regulations are met and there is no restriction that such 

procedures are limited to items that are conducted prior to certification. Further, ARB 

clearly has authority to adopt enforcement regulations and procedures to be used on 

engines and vehicles after certification and there is no restriction that these procedures 

be carried out exclusively by ARB. 

Staff did consider alternatives to the manufacturer self-testing element and to the 

engine dynamometer testing. Staff looked into various methods to contract out for and 

perform engine dynamometer testing. However, as noted above, engine dynamometer 

testing requires very detailed knowledge about the engine and often requires custom 

equipment or parts created by the manufacturer themselves to successfully conduct a 

test (e.g., water to air coolers to simulate on-vehicle air-to-air coolers, simulations of 

vehicle or transmission outputs to enable the engine to operate over the required speed 

and load regions). Engine manufacturers are uniquely qualified to test their own 

engines at a substantial economic savings relative to anyone else. Staff investigated 

methods to develop a ‘screening’ test of some sort using portable emission 

measurement systems (PEMS) which would allow testing while the engine is still in the 

vehicle. If such a method could identify whether an engine would likely pass or fail, then 
73

only engines that are more likely to fail could be sent on to engine dynamometer based 

testing for the ultimate compliance decision. Unfortunately, several complications were 

encountered that, at this time, render such a screening test infeasible. Staff has 

discussed this with industry and has indicated it is still open to suggestions that evolve 

in the future. And, because the first engines won’t need to be tested until 2013 calendar 

year, there is significant time between now and then for more ideas to surface and be 

considered during a future biennial review. Should such an idea surface and need to be 

used before a future biennial review can incorporate it, language is included in section 

1971.5 to allow the Executive Officer to accept alternative testing procedures upon the 

manufacturer demonstrating they will provide an equivalently robust determination as to 

the compliance of the OBD system on the engine. 

2. ARB Conducted Testing 

The structure of the proposed regulation is similar in many respects to the OBD II 

enforcement regulation, especially as it applies to the testing of OBD systems that 

would occur while the engine is installed in the vehicle. Under the proposed regulation, 

the ARB staff could elect to periodically evaluate engines from any certified engine 

class. It would be directly responsible for enforcement testing of all HD OBD 

requirements other than the testing of emission-related monitors, which require engine 

dynamometer testing. For example, ARB staff would conduct enforcement for testing of 

in-use performance monitoring ratios and other non-emission-threshold related 

requirements. For such non-emission related testing, the protocols that the ARB would 

use would closely follow the OBD II protocols for procuring, testing, and determining 

compliance of OBD systems. Additionally, ARB could elect to conduct testing on 

emission-threshold monitors that require engine dynamometer testing at an 

independent laboratory or at an ARB facility, but such testing is expected to be limited 

due to the difficulties in conducting such testing and lack of an ARB testing facility. 

The proposed procedures set forth detailed provisions on how ARB will conduct testing, 

including, among other things, how the staff would initially determine the scope of 

engines (the engine class) to be tested, the number of engines to be tested (i.e., the 

size of the test sample group), and the type of testing to be conducted. As indicated, 

ARB enforcement testing would be grouped into three different categories depending on 

the nature of the OBD II noncompliance issue to be tested. Specifically, the protocol 

proposes that separate guidelines and procedures be followed for in-use performance 

ratio testing, “other” HD OBD testing, and testing of emission-related threshold 

monitors. 

For OBD ratio testing, ARB staff would collect data from a test sample group of 30 

engines that have been properly procured and selected. In determining compliance 

with other requirements that do not require emission testing, the staff would determine, 

on a case by case basis, the number of engines needed to ensure that the results of 

such testing may be reasonably inferred to the engine class. The determination would 

be based upon the nature of the nonconformance and the scope of the engine class. 

The test sample group could be as few as two test engines. For OBD emission testing, 
74

the ARB staff would follow the provisions of Cal. Code Regs., title 13, section 2137 

regarding test sample size. In accordance with section 2137, the staff would test 10 

engines that have been properly procured and selected. 

The ratio testing procedures would be used when the in-use monitor performance is 

tested for compliance with the minimum acceptable in-use monitor performance 

requirements (i.e., does the monitor run often enough?). In cases where the monitor 

being tested has a ratio that is required to be tracked and reported to a scan tool in 

standardized manner, the actual ratio testing of procured vehicles would be a rather 

expeditious and straightforward process. The “testing” of the 30-plus engines would be 

as simple as electronically downloading the stored data from the engines with a 

diagnostic tool (e.g., an OBD scan tool). 

For testing of monitors that are required to meet the ratio but are not required to track 

the data in the on-board computer or report it in a standardized manner, the process 

would be lengthier and slightly more involved. In these cases, rather than downloading 

information stored in the on-board computer, each test engine would be equipped with 

instrumentation that would record and collect engine activity data and diagnostic 

activity. Each test vehicle would then be returned to the vehicle operator for 

accumulation of data. After collection of sufficient data (the same amount of data as 

required for the ratios that are tracked and reported), the data would be analyzed to 

determine the ratio for the tested monitor for each engine. This method is directly 

analogous to that used for the ratios that are required to be tracked and reported in the 

on-board computer by effectively tracking and reporting the ratio in an “off-board” 

computer (i.e., the instrumentation attached to the engine). 

Testing of HD OBD requirements other than rate-based monitoring or emission testing 

would be determined on a case-by-case basis because of the myriad of different 

requirements included in this residual category and the many nuances of the complex 

systems that they regulate that may affect some aspects of the system performance. 

Given this complexity, it is impossible to predict every possible permutation or 

noncompliance that might occur in the future. As such, it is impossible to prescribe 

exact test procedures that will adequately address every possible noncompliance 

scenario. For example, a problem could be as simple as a system not complying with 

the MIL display requirements (e.g., using an incorrect symbol or wording instead of the 

required engine symbol on the dashboard light). The noncompliance would likely be 

confirmed by using a visual examination of the procured vehicles. On the other hand, 

the problem could be complex such as the inability of the HD OBD system to properly 

detect malfunctioning thermostats that cause the engine to warm up too slowly. Such a 

malfunction could cause a vehicle to have increased emissions and/or cause the 

disablement of other diagnostics. In contrast to the first example, testing could not be 

conducted to confirm noncompliance by performing a visual inspection but would 

require implanting of a faulty thermostat and operation of the vehicle in various ambient 

and driving conditions to ensure the manufacturers’ disclosed monitoring conditions 

have been satisfied, all while recording results and data with an off-board tool. 

Accordingly, for the “other” HD OBD testing category, the proposed regulation defines 
75

general guidelines to be followed by the staff when conducting testing in this area. The 

Executive Officer would have discretion to determine, on a case-by-case basis, the 

most appropriate procedures for selection and testing of vehicles based on the nature of 

the noncompliance and the projected number of affected engines. The Executive 

Officer would be required to provide notice of the selection and testing procedures to 

the manufacturer of the engines subject to such testing (see discussion below). 

The HD OBD emission testing procedures would be used when the measurement of 

tailpipe emission levels relative to the tailpipe emission standards is essential to 

determining system compliance. Emission testing for HD OBD compliance is comprised 

of two distinct parts: (1) emission testing in accordance with the test procedures used by 

the Executive Officer for in-use testing of compliance with tailpipe emission standards in 

accordance with Cal. Code Regs., title 13, sections 2138 and 2139; and (2) on-road 

and/or dynamometer testing with the engine being operated in a manner that 

reasonably ensures that all of the monitoring conditions disclosed in the manufacturer's 

certification application for the tested monitor are encountered. The latter testing will be 

conducted to determine the MIL illumination point and the former testing will be 

conducted to determine the tailpipe emission level at the MIL illumination point. 

Together, these two parts of testing are necessary to determine if the MIL illuminates 

prior to exceeding the tailpipe emission levels as required in the 

HD OBD regulation. As stated, HD OBD emission-threshold monitoring requires engine 

dynamometer testing. For all such testing, the staff must implant a malfunction into the 

engine and then determine if the HD OBD system properly detects the malfunction at 

the required tailpipe emission levels. 

Like the OBD II regulation, the proposed HD OBD regulation sets forth the decision 

criteria that the Executive Officer would use to determine if a system is noncompliant for 

each type of testing. For example, for HD OBD minimum in-use monitoring frequency 

testing, the system would be noncompliant if the average in-use performance of the 

sample engines is below a critical ratio that indicates the average ratio for the entire 

engine class is below the required minimum in-use monitor performance ratio of 0.100 

set forth in Cal. Code Regs., title 13, section 1971.1(d)(3). For 2016 and subsequent 

model year engines, engines would be considered noncompliant with the in-use 

performance ratio requirement if either 66 percent or more of the 30-engine test sample 

had a ratio of less than 0.100 or the average of the ratios in the test sample was less 

than a critical ratio of 0.088. This critical ratio was calculated using the same method 

discussed in Appendix V of the 2002 OBD II Staff Report referenced above to provide 

statistical confidence that the results derived from the 30-engine sample represent the 

actual in-use performance of the affected engines. 

And, for the “other” testing category, the system would be determined to be 

noncompliant if 30 percent or more of the sample engines fail to meet the same 

requirement that falls within the residual-testing category. This criterion is consistent 

with the criterion set forth in the existing tailpipe emission enforcement procedures, 

which provides that a test group or sub-group of vehicles shall be considered 

nonconforming when a specific emission-related failure occurred in three or more test 
76

vehicles from a sample that includes a minimum of 10 in-use vehicles. The staff 

believes that use of the definitive 30 percent criterion is preferable to the use of the term 

“substantial number of a class or category of vehicles that ...experience a failure of the 

same emission-related component...”, that is used in the definition of nonconformity in 

the existing enforcement procedures.6 The specific percentage will provide clear notice

to all parties of what is expected for compliance with the regulations. 

For HD OBD emission testing, the regulation specifies that the system would be 

determined to be noncompliant if 50 percent or more of the tested sample engines are 

unable to properly detect a malfunction and illuminate the MIL before tailpipe emissions 

exceed the malfunction criteria thresholds set forth in Cal. Code Regs., title 13, section 

1971.1(e) and (f). Further details of the emission testing are provided in section IX. D.4. 

below 

If any of the above testing indicates that the HD OBD system is suspected of being 

noncompliant, the Executive Officer would be required to provide the manufacturer with 

a notice of the test results. The proposed regulation would require that such notice 

include all relevant supporting information that the Executive Officer relied upon in 

making his or her determination of nonconformance of the HD OBD system. 

Manufacturers would have the opportunity to respond to the preliminary notice and 

present test results and other data that they believe rebut the preliminary findings of 

noncompliance. Upon consideration of the information submitted by the manufacturer, 

the Executive Officer may decide to perform additional in-use testing if necessary. The 

Executive Officer would consider all information submitted by the manufacturer in 

ultimately determining whether an HD OBD system is nonconforming. 

Lastly, the Executive Officer would be required to issue a notice of final determination to 

the manufacturer as to whether the HD OBD system is nonconforming. If the Executive 

Officer finds the HD OBD system to be nonconforming, the regulation would require the 

notice to set forth the factual bases for the determination. After receiving the notice of 

noncompliance from the Executive Officer, a manufacturer would have 45 days to elect 

to conduct an influenced recall and repair of the affected vehicles. If the manufacturer 

were to take no action, the Executive Officer could order the manufacturer to take 

appropriate remedial action scaled to the level of noncompliance. The proposed 

regulation sets forth a detailed set of factors that the Executive Officer would consider in 

determining the appropriate remedy. Three distinct categories of remedial action are 

identified in the regulation and are discussed in section 4 below. 

3. Manufacturer Self-Conducted Compliance Testing 

Cal. Code Regs., title 13, section 1971.1, would require as a condition for certification 

that manufacturers conduct compliance testing of in-use engines to ensure that 

production engines in-use continue to meet the HD OBD requirements. The 

requirements for compliance testing are set forth as part of Cal. Code Regs., title 13, 

 

6

 Cal. Code Regs., title 13, section 2112(h) 
77

section 1971.5, and are discussed immediately below. ARB may use the results of 

such testing to determine if enforcement remedial action is necessary. A summary of 

the compliance test procedures that manufacturers would be required to follow is 

provided below. 

Specifically, manufacturers would be required to perform enforcement testing on one to 

three engine families per year, depending on the size of the manufacturer. For each 

engine family, manufacturers would be required to procure a single representative inuse engine with approximately 75 percent of full useful life mileage and remove it from 

the vehicle for engine dynamometer testing. For each tested engine, the manufacturer 

would run the same sequence of tests ARB would run—testing each threshold 

component one after the other and determining the emission level at which the fault is 

detected. Given the mileage for procurement, such testing would occur approximately 

three years after introduction of the engine into the marketplace so 2010 model year 

engines would first be tested in 2013 calendar year. 

Under the proposed procedures, an engine manufacturer would be required to submit a 

listing to the Executive Officer of all of the engine families and engine ratings within 

each family that have been certified for each model year. The Executive Officer would 

then select the engine family(ies) and the specific engine rating within the engine 

family(ies) that the manufacturer shall use as a test engine for the test sample group to 

provide emission test compliance data. For the 2010 model year, a manufacturer would 

be required to provide emission test data of a test engine from the OBD parent rating. 

In 2013 and subsequent model years, the number of test engines that a manufacturer 

would be required to provide emission test data from would depend upon the number of 

engine families that it certified in any model year: if from one to five engine families 

were certified, the manufacturer would be required to provide data from one engine 

rating; six to ten certified engine families would require data from two engine ratings; 

and eleven or more certified engine families would require data from three engine 

ratings. The Executive Officer could waive the requirement for submittal of data of one 

or more of the test engines if data have been previously submitted for all of the engine 

ratings. 

In selecting the test sample group, the engine manufacturer would be required to follow 

the same criteria that ARB would follow in conducting enforcement testing. Within three 

calendar years after the model year of the engine (e.g., by the end of calendar year 

2013 for a 2010 model year engine), the engine manufacturer would be required to 

complete compliance testing of the emission threshold monitors of the test engine. 

Prior to conducting any testing, the engine manufacturer would be required to replace 

components monitored by the OBD system with components that are sufficiently 

deteriorated or simulated to cause malfunctions that exceed the malfunction criteria 

established in Cal. Code Regs., title 13, sections 1971.1(e) through (g) in a properly 

operating system. The engine manufacturer would not be required to use components 

deteriorated or simulated to represent failure modes that could not have been foreseen 

to occur by the manufacturer. 
78

After the test engine(s) has been selected and procured, engine manufacturers would 

need to perform emission testing for all applicable components/systems according to 

the certification demonstration testing requirements of Cal. Code Regs., title 13, 

sections 1971.1(i)(3) and (i)(4), unless a manufacturer obtains approval from the 

Executive Officer to deviate from the procedures for the purpose of compliance testing. 

If the initial testing on the originally selected test engine indicates that the OBD system 

properly illuminates the MIL for all component/system monitors before emissions 

exceed the malfunction criteria defined in title 13, CCR sections 1971.1(e) through (g), 

no further testing is required. 

However, if the results of the OBD emission tests indicate that the OBD system does 

not properly illuminate the MIL for one or more of the component/system monitor(s) 

before emissions exceed the malfunction criteria defined in Cal. Code Regs., title 13, 

sections 1971.1(e) through (g), the engine manufacturer would need to conduct further 

testing on an additional four engines from the same engine rating and engine family as 

the test engine. The engine manufacturer would only be required to test the 

component/system monitor(s) for which the OBD emission test results exceeded the 

malfunction criteria specified in the HD OBD requirements. If the results indicate that 

the OBD system properly illuminates the MIL for the tested component/system 

monitor(s) before emissions exceed the malfunction criteria, on three or more of the 

additional test engines, the no further testing is required. If, however, two or more of the 

engines failed the second round of testing, the manufacturer would be required to test 

five more engines. At the conclusion of testing, if five or more of the ten total tested 

engines failed, the Executive Officer would make a determination that the engine family 

is noncompliant.

Under the proposed compliance/enforcement testing procedures, manufacturers would 

be required to allow ARB personnel access to any facility where a manufacturer 

performs any work related to procurement, selection, or testing and any facility where 

documents relating to the above are located. Among other things, ARB staff would be 

allowed to inspect and monitor work performed at these facilities, including the right to 

verify correlation or calibration of test equipment, inspect and photograph any part or 

aspect of the tested engine(s) and any components added to the engine(s) in 

conjunction with testing. ARB personnel would also have the right to inspect and make 

copies of any such records, designs, or other documents related to a tested engine and 

its testing. 

 

Within 30 days after completing testing of the initial engine, the manufacturer would be 

required to submit a report of the results of the testing as well as a detailed description 

of the conducted testing to the Executive Officer. If testing of additional engines is 

required, the manufacturer would have six months to complete the testing and would 

need to submit an additional report within 30 days of completing the additional testing. 

After the engine manufacturer has conducted testing pursuant to sections (c)(3) and 

(c)(4) and the Executive Officer has received the test results pursuant to section (c)(6) 

as described above, the Executive Officer shall make a finding of nonconformance of 
79

the OBD system in the engine class using the same criteria that is used in ARBconducted enforcement testing. The Executive Officer would provide the manufacturer 

of his or her compliance determination. In the case of a finding of noncompliance, the 

Executive would follow the procedures similar to that previously described for ARBconducted notices. 

4. Remedial Action 

A. Introduction 

After notification of noncompliance from the Executive Officer, a manufacturer would 

have 45 days to elect to conduct an influenced recall and repair of the affected engines. 

If the manufacturer takes no action, the Executive Officer could order the manufacturer 

to take appropriate remedial action scaled to the level of noncompliance. The 

regulation would set forth a detailed set of factors that the Executive Officer would 

consider in determining the appropriate remedy. 

The proposed regulation would provide for the recall of effectively nonfunctional HD 

OBD systems because the existence of such a noncomplying system effectively defeats 

the purposes and objectives of the HD OBD program and potentially undermines the 

emission reduction benefits that have been projected from recently adopted tailpipe 

standards for heavy-duty engines. It has been the long-standing position of the ARB 

that it is necessary to repair or replace such nonconforming systems because they are 

not capable of detecting future malfunctions of the engine’s emission control systems 

and that this would likely lead to future emission increases.7

 This position is consistent 

with the Senate Committee on Environment and Public Works when considering federal 

adoption of onboard diagnostic regulations.8 

 

7

 See e.g., Manufacturers Advisory Correspondence No. 87-06 (July 1, 1987), in which the ARB 

stated. 

A recall . . . would be appropriate based on . . . the underlying defect identified by the 

OBD system even where the vehicles could pass the FTP, assuming a substantial 

number of vehicles in the class or category being tested contained that defect. 

8

P.L. 101-549, Clean Air Act Amendments of 1989, S.Rep. 101-228, 101st Cong., lst Sess. 1989, 

1990 U.S.C.C.A.N. 33855, 1989 WL 2326970 et seq. , in which the Committee reported: 

The amended section 202 of the [CAA] authorizes the Administrator to promulgate regulations for 

[emission control diagnostics (ECD)]. Existing section 207(c) of the [CAA] provides for recall of 

vehicles which do not conform to the regulations adopted under section 202, thus providing clear 

authority for the Administrator to recall classes or categories of vehicles determined to have 

malfunctioning ECD systems during their full useful life. This authority will enable EPA to ensure 

that the emission components and the ECD system operate properly. A vehicle will be recalled or 

repaired if, during the useful life of the vehicle, the ECD system itself is broken or malfunctions 

such that it would no longer be able to serve its intended function of alerting the vehicle operator 

to the need for emission related maintenance and properly storing such information for 

subsequent retrieval by inspection or maintenance personnel. The ECD system is intended to 

alert the operator to the need for maintenance which may head off further emission deterioration 

or damage to the emission control system. Therefore, the Administrator may order a recall and a 
80

It is beyond dispute that as heavy-duty engines age and accumulate high mileage, their 

emission control systems deteriorate, increasingly malfunction, and cause emissions to 

increase. No one knows or can accurately predict how well emission control systems of 

different manufacturers will work 10, 20, or more years from now. This is especially true 

when heavy-duty engines are being required to meet increasingly stringent emission 

standards, requiring new and complex technologies to be utilized. 

B. Mandatory Recall 

The staff is proposing that the most seriously design-flawed nonconforming HD OBD 

systems discovered as part of manufacturer compliance testing or ARB enforcement 

testing be subject to mandatory recall. See Table 1 below. Under Cal. Code Regs., 

section 1971.5(d)(3) of the proposed regulation, the Executive Officer would be required 

to order the recall of HD OBD systems that have at least one major monitor that 

performs so egregiously that it cannot effectively detect malfunctions or cannot be 

validly tested in a roadside inspection or fleet self-inspection. The ARB adopted the HD 

OBD requirements to address this problem and, specifically, to provide assurance that 

when malfunctions in emission control systems do occur, they will be expeditiously 

discovered and repaired. To properly perform these objectives, the HD OBD system 

itself must be functional and capable of detecting malfunctions when they occur. To 

minimize potential emission increases in future years, it is imperative that the identified, 

effectively nonfunctional OBD systems be recalled and repaired at the time 

noncompliance of the systems is discovered. Monitors that perform at levels 

significantly below the established criteria thresholds in-use run the risk of undermining 

the potential benefits of the HD OBD program. The ARB staff has concluded that 

systems that operate below these levels are essentially nonfunctional and need to be 

repaired or replaced. 

By specifying minimum performance levels, below which a system would be considered 

nonfunctional and in need of recall, the Executive Officer would be providing 

manufacturers with clear notice and direction as to what the ARB considers to be a 

totally unacceptable system. With such knowledge, manufacturers can better plan and 

design their product lines and perform necessary internal testing to assure proper 

performance of the HD OBD systems that they manufacture and distribute. The 

minimum performance levels that would be established by the regulation for recall are 

fair and reasonable. The levels have been set so as to provide a liberal margin of error 

that distinguishes between a monitor that fails to meet the threshold levels required for 

proper detection of malfunctions and a monitor that performs so poorly that it cannot be 

considered functional. The proposed criteria for mandatory recall are summarized in 

Table 1 below. 

 

repair of the ECD system in cases wherever there is systematic misdiagnosis, even if the vehicle 

is passing emission standards, either by not alerting the operator to the need for necessary repair 

or by flagging a repair which is not necessary. 
81
82

Table 1: HD OBD Enforcement Regulation Mandatory Recall Criteria

parent *1 child *2

previous 2010-2012 phase-in engine family parent child

previous child from 2013-2015 al

Tailpipe Level < OBD threshold pass n/a pass pass n/a pass pa

> OBD threshold and < 2x OBD threshold pass n/a pass pass n/a pass

fafilt

> 2x and < 3x OBD threshold fail n/a fail fail n/a fail

farefilt

> 3x OBD threshold fail n/a

fail, mandatory recall

fail, mandatory recall n/a

fail, mandatory recall

fare

Applicable standard (FTP or SET)

Manufacturer determined at cert n/a

Manufacturer determined at cert

Manufacturer determined at cert n/a

Whichever is actual worst case

Wac

Recall Liability no mandatory n/a

mandatory at >3x OBD threshold

mandatory at >3x OBD threshold n/a

mandatory at >3x OBD threshold

mO(3m

Ratios > 0.100 ratio in reg n/a n/a pass pass pass pass pa

>0.05 and < 0.100 n/a n/a pass pass pass fail fa>0.033 and < 0.05 n/a n/a fail fail fail fail fa< 0.033 n/a n/a fail fail fail

fail, mandatory recall

fare

Recall Liability n/a n/a no mandatory no mandatory no mandatory

mandatory <0.033

m<0

Note: "2x OBD threshold" does not mean 2x standard. E.g., if OBD threshold is 2.5x std, 2x OBD threshold is 2x (2.5x std) = 5.0x std

*1 "Parent" in this table refers to a specific engine rating within an engine family that is required to be fully compliant with HD OBD*2 "Child" in this table refers to the other engine ratings within an engine family that are allowed to "carry over" calibrations from the par

engine and are not required to be fully compliant with HD OBD

2010-2012 2013-2015 2016-2
83

C. Discretionary Remedial Action 

The proposed regulation also provides the Executive Officer with discretionary authority 

to order remedial action when he or she finds a HD OBD system to be nonconforming 

for reasons other than those requiring mandatory recall. The Executive Officer would 

have discretion to order a graduating scale of remedies. In determining appropriate 

remedial action, the Executive Officer would consider all relevant circumstances 

surrounding the existence and discovery of the nonconformity, including the factors 

specifically set forth in section 1971.5(d)(4)(B). For example, in cases where the 

nonconformity is limited, the HD OBD system is largely functional, and the manufacturer 

has voluntarily identified the nonconformity, the Executive Officer would have authority 

to order a lesser form of remedial action, comparable to a deficiency. In the most 

serious cases, where the Executive Officer determines that the HD OBD system, when 

considered in its totality, is unacceptably ineffective, he or she would have discretion to 

order the recall of the nonconforming systems. 

D. Monetary Penalties 

Pursuant to authority granted under the Health and Safety Code,9 the Executive Officer 

would be able to seek monetary penalties against a manufacturer for a nonconforming 

HD OBD system on a case by case basis. In determining whether to seek penalties, 

the Executive Officer would consider all relevant circumstances, including, but not 

limited to, the factors set forth in Cal. Code Regs., title 13, section 1971.5(d)(5). 

E. Notice to Manufacturer of Remedial Order and Availability of Public Hearing 

The proposed regulation requires the Executive Officer to notify the manufacturer of the 

ordered remedial action and/or his or her intent to seek monetary penalties in an 

administrative or civil court. The notice would be required to include a description of 

each class of vehicles or engines covered by remedial action and the factual basis for 

the determination. The notice would further provide a date at least 45 days from the 

date of receipt of such notice for the manufacturer to submit a plan outlining how it 

proposes to comply with the remedial order or to request a public hearing to consider 

the merits of the ordered remedial action. 

F. Requirements for Implementing Remedial Action 

The proposed regulation sets forth requirements and procedures to be followed by the 

manufacturer in implementing either a voluntary, influenced, or ordered remedial action. 

Among other things, the regulation would establish specific provisions requiring 

manufacturers to establish remedial action plans, provide notice to owners of heavyduty vehicles and engines affected by the remedial action, and maintain and make 

available specific information regarding the remedial action. The proposed 

requirements and procedures are identical to the requirements of the OBD II 

enforcement regulation and similar, but not identical, to those required for tailpipe 

 

9

 See Health and Safety Code, sections 43016, 43154, 43211-43212.
84

enforcement remedial actions in Cal. Code Regs., title 13, sections 2113 – 2121 and 

sections 2123 – 2132.10 As with the existing enforcement provisions, the proposed 

requirements for implementing remedial action provide clear directions to a 

manufacturer subject to a remedial action on its obligations and responsibilities in 

carrying out a remedial action campaign. This should ensure effective and expeditious 

implementation of proposed remedial action plans and compliance with the HD OBD 

requirements. The proposed requirements should also ensure that all manufacturers 

follow consistent reporting requirements that allow for full and effective monitoring of the 

remedial action campaign by the ARB. 

Having determined the need for specific enforcement procedures, it makes sense that 

the requirements and procedures for implementing HD OBD-related remedial actions 

should be included within the self-contained HD OBD enforcement procedures. This 

follows closely with the procedures for remedial action that manufacturers must follow 

under the OBD II enforcement procedures. Having a single regulation with all HD OBD 

enforcement provisions should prove helpful and convenient to both affected 

manufacturers and ARB staff. The result should be a clearer, more readily 

understandable document. 

G. Penalties for Failing to Comply with the Requirements of Section 1971.5(e) 

The staff is proposing a provision that would make it clear that a manufacturer could be 

subject to penalties, in addition to any penalties that could be assessed for HD OBD 

nonconformance, for failing to comply with the proposed requirements for implementing 

remedial action. Such failures would be considered a violation of the Health and Safety 

Code and would subject the manufacturer to penalties prescribed under Health and 

Safety Code section 43016. The ability to assess monetary penalties should encourage 

compliance with the requirements for implementing recall actions and result in thorough 

and timely implementation of both voluntary and ordered remedial action campaigns. 

 

10 The proposal includes a requirement that manufacturers subject to an HD OBD recall be required to 

report on the progress of the remedial action campaign by submitting reports for eight consecutive 

quarters. See section 1971.5(e)(6)(B). Although the eight consecutive quarter requirement differs from 

the reporting requirements of Cal. Code Regs., title 13, sections 2119(a) and 2133(c), the proposal is in 

fact consistent with ARB practice. See “Voluntary and Influenced Recall Recordkeeping and Reporting,”

MAC #96-08, July 26, 1996. Similarly, the proposed reporting requirements require manufacturers 

subject to vehicle recall to provide the ARB with a list of data elements and designated positions in the 

submitted reports that indicate all vehicles or engines subject to the recall that have not as yet been 

corrected. Although not expressly set forth in the existing recall reporting requirements, the information 

required under the proposed provision has a long-standing ARB requirement and is consistent with OBD 

II enforcement. See “Revision to Mail-Out 91-13 (Implementation of Air Resources Board’s (ARB) and 

Department of Motor Vehicles’ Registration Renewal/Recall Tie-In Program), Mail-Out 91-19, April 10, 

1991. 
85

E. INTERIM IN-USE RELIEF 

With this proposed adoption, staff is also proposing to delete section 1971.1(m) of the 

HD OBD regulation, which detailed intermediate in-use compliance standards, as these 

criteria would be incorporated into the proposed stand-alone HD OBD enforcement 

regulation. These criteria provide interim relief by phasing in enforcement liability for 

manufacturers over the first years of HD OBD implementation. These criteria included 

higher interim in-use compliance standards for HD OBD monitors that are calibrated to 

specific emission thresholds as well as relaxed criteria for the minimum in-use 

frequency. This interim relief provides manufacturers with extra margin to fine-tune their 

calibration techniques and to gain experience with in-use operation, without imposing an 

excessive level of risk for mistakes. 

Under the existing regulation, an OBD monitor in 2010 through 2015 model year 

engines will be considered compliant (and not subject to enforcement action) unless 

emissions exceed twice the OBD threshold without detection of a fault. Additionally, the 

number of engines subject to liability in these years is limited. For example, for 2010 

through 2012 model years, manufacturers will only be liable for the highest sales 

volume engine rating (e.g., a specific rated power variant) within the one engine family 

that is required to have an OBD system. Other engine ratings within that engine family 

are not subject to liability even though they may fail to detect a fault at the specified 

emission threshold. For 2013 through 2015 model years, all engine ratings within this 

original OBD engine family are potentially liable if they fail to meet the emission 

thresholds. Further, a limited number of engine ratings in other engine families are 

subject to liability for in-use noncompliance in the 2013 model year. Emission threshold 

liability for all in-use engines does not become effective until the 2016 model year. 

F. RESPONSIBLE PARTY 

Under the proposed enforcement procedures, the engine manufacturer that is the 

certifying party would be the responsible party for all in-use compliance and 

enforcement actions. In this role, the engine manufacturer would be ARB’s sole point of 

contact for any noncompliance identified during in-use or enforcement testing. In cases 

where remedial action will be required (e.g., recall), the certifying party would be 

responsible for coordinating any actions to remediate the noncompliance (e.g., 

coordination with truck builders to contact vehicle owners or to provide service networks 

to conduct the recall work). To protect themselves, it is expected that engine 

manufacturers would require engine purchasers to sign indemnity clauses or other 

agreements to abide by the build specifications applicable to the engine and to bear 

ultimate financial responsibility for noncompliance caused by the engine purchaser. 

X. ANALYSIS OF ENVIRONMENTAL IMPACTS AND ENVIRONMENTAL JUSTICE 

ISSUES 

As stated, the proposed HD OBD and OBD II requirements and enforcement 

procedures help ensure that forecasted emission reduction benefits from adopted light-, 
86

medium-, and heavy-duty engine emission standards programs are achieved. Given 

the substantial shortfall in emission reductions still needed to attain the National and 

State Ambient Air Quality Standards and the difficulty in identifying further sources of 

cost-effective emission reductions, it is vital that the emission reductions projected for 

the light-, medium-, and heavy-duty vehicle programs be achieved. The OBD 

regulations are necessary to accomplish this goal, achieving these emission benefits in 

two distinct ways. First, to avoid customer dissatisfaction that may be caused by 

frequent illumination of the MIL because of emission-related malfunctions, it is 

anticipated that the manufacturers will produce increasingly durable, more robust 

emission-related components. Second, by alerting vehicle operators of emissionrelated malfunctions and providing precise information to the service industry for 

identifying and repairing detected malfunctions, emission systems will be quickly 

repaired. The benefits of the regulations become increasingly important as certification 

levels become more and more stringent and as a single malfunction has an increasingly 

greater impact relative to certification levels. 

Regarding the HD OBD regulation, the proposed amendments are not expected to 

significantly alter previously calculated emission benefits or findings. Though the 

proposed amendments for diesel engines would delay the starting implementation date 

of a few emission threshold monitoring requirements and would allow higher interim 

malfunction emission thresholds for some monitors, the staff believes these short term 

interim delays and higher thresholds are necessary considering the diesel emission 

control technologies involved are new and evolving and have never previously existed 

on diesel engines. 

For reference, during the 2005 HD OBD regulatory process, lifetime cumulative 

emission reductions attributable to the HD OBD program, on a per engine basis, were 

calculated to be 81 pounds of ROG, 5,735 pounds of NOx, and 24 pounds of PM. 

Details of the methodology can be found in the 2005 HD OBD staff report. However, 

staff has recalculated the benefits using the latest emission inventory models. The 

estimated emission benefits from HD OBD are significantly different from the 2005 

estimates due primarily to a recent update of the base emission inventory model 

(EMFAC). EMFAC was updated with new data for heavy-duty vehicle miles traveled 

and emission rates. In addition, an error was found in the 2005 estimates that resulted 

in an overestimation of the NOx and ROG benefits. As a result, the lifetime cumulative 

emission reductions for HD OBD, on a per engine basis calculated with the most recent 

version of EMFAC, are 165 pounds of ROG, 2000 pounds of NOx, and 14 pounds of 

PM. 

With this rulemaking, the primary amendments apply to the HD OBD regulation. As 

stated earlier, changes are also being made to the light- and medium-duty OBD II 

regulation to harmonize the medium-duty diesel requirements with the heavy-duty diesel 

requirements. The changes to the OBD II regulation, for both gasoline and diesel, are 

minor and are not expected to significantly alter previously calculated emission benefits 

or findings. 
87

For reference, during the 2002 OBD II regulatory update, staff calculated a combined 

benefit for OBD II and LEV II of 57 tons per day of ROG + NOx in the South Coast Air 

Basin alone. Details of the methodology can be found in the 2002 OBD II staff report. 

Given the substantial shortfall in emission reductions still needed to attain the National 

and State Ambient Air Quality Standards and the difficulty in identifying further sources 

of cost-effective emission reductions, it is vital that the emission reductions projected for 

the LEV II program be achieved. The proposed OBD II regulatory revisions apply 

almost exclusively to LEV II vehicles and better ensure these vehicles will continue to 

operate at the expected emission levels, a necessary step towards achieving this goal. 

Having identified that the proposed amendments to the regulations will not result in any 

adverse environmental impacts but rather will help ensure that measurable emission 

benefits are achieved both statewide and in the South Coast Air Basin, the amendments 

should not adversely impact any community in the State, especially low-income or 

minority communities. 

XI. COST IMPACT OF THE PROPOSED REQUIREMENTS 

A. COST OF THE PROPOSED REQUIREMENTS 

For HD OBD, like the modifications to the OBD II program, the revisions to the 

regulation (§1971.1) consist primarily of interim relief and clarification of existing 

requirements. As such, the previously calculated cost estimate is still applicable. 

However, ARB staff has performed a comprehensive cost analysis of the proposed HD 

OBD enforcement program to add to the previous estimate. The goal of this analysis is 

to estimate the “learned-out” costs of the program to a heavy-duty engine purchaser for 

a “typical” engine. The analysis estimates the incremental costs of implementing the 

HD OBD enforcement regulation for a “hypothetical” larger-than-average engine 

manufacturer. The hypothetical engine manufacturer is projected to include eight 

engine families and five ratings per engine family. In contrast, the “average” engine 

manufacturer according to U.S. EPA’s data of 2004 heavy-duty engines includes 6.5 

engine families and five ratings per engine family. To determine the average sales 

number of the hypothetical manufacturer, the staff took the national sales numbers for 

the top nine engine manufacturers and determined a composite average value of 

72,440. This number was rounded to 72,000 in the analysis. 

The various types of costs that are addressed in this analysis are variable costs, 

support costs, investment recovery costs, capital recovery costs, and truck/coach 

builder costs. Results of the analysis from the 2005 staff report indicate the learned-out 

costs per engine to comply with the proposed HD OBD regulation (§1971.1) would be 

$132.39 for diesel engines and $35.04 for gasoline engines. As note above, since the 

proposed modifications to the regulation consist mainly of threshold modifications for 

diesel engines to provide compliance relief, the previous cost estimates should still 

apply. In the very limited cases where a new monitor is required (e.g., cylinder air-fuel 

imbalance), lead time is provided to allow manufacturers to implement necessary 

changes in conjunction with scheduled vehicle upgrades. None of the new monitoring 

requirements should require any additional hardware for monitoring. It is projected that 
88

only software modifications will be required to comply with the any of the new 

requirements. 

B. COSTS OF THE HD OBD ENFORCEMENT PROGRAM 

As described in section IX, staff is proposing the adoption of Cal. Code Regs., title 13, 

section 1971.5 which would establish enforcement procedures and requirements for 

heavy-duty OBD systems. Costs were estimated utilizing the same methodology and 

assumptions as described above for the HD OBD regulation (i.e., costs were based on 

a hypothetical larger-than average engine manufacturer). Additionally, costs were only 

estimated for diesel engines since the costs for testing diesel engines are significantly 

higher than gasoline engines due to the cost of the engine and the associated 

aftertreatment components. Results of the analysis indicate the learned-out incremental 

retail costs to incorporate the proposed HD OBD enforcement regulation would be 

$1.97 per engine. Therefore, the estimated combined costs of the HD OBD regulation 

and the proposed HD OBD enforcement regulation are $134.36 per heavy-duty diesel 

engine and $37.01 per gasoline engine. Details of the cost analysis methodology are 

described in the heavy-duty OBD staff report of July 2005. The primary costs 

associated with the enforcement regulation are for the provisions that require ‘selftesting’ by the manufacturer at a rate of one to three engines per year, depending on 

the size of the manufacturer (two per year has been assumed for this cost analysis). 

The primary assumptions used include a cost of $23,150 per engine in procurement 

related expenses and just over $80,000 per engine in testing costs. Staff talked with 

manufacturers, EPA, and independent laboratories that perform such procurement and 

testing in developing these estimates. Tables 1 and 2 below summarize the results of 

the cost analysis when spread out across all engines produced by a manufacturer. 
89

Table 1: Incremental Consumer Cost of HDDE 

 

 

1971.1 

Costs 1971.5 Costs Total HD OBD Costs 

 (in dollars) (in dollars) (in dollars) 

Variable costs Component $37.18 $0.00 $37.18 

 Assembly $0.68 $0.00 $0.68 

 Warranty $1.64 $0.00 $1.64 

 Shipping $1.20 $0.00 $1.20 

Support costs Research $22.49 $0.00 $22.49 

 Engineering Support $0.14 $0.08 $0.22 

 Legal $0.35 $0.00 $0.35 

 Administrative $2.08 $0.16 $2.24 

Investment Mach. & equipment $0.00 $0.00 $0.00 

recovery costs Assembly plant changes $0.00 $0.00 $0.00 

 Development/Testing $57.34 $1.59 $58.93 

Capital recovery (a) $7.39 $0.11 $7.50 

Truck/Coach Builder costs Cost of capital recovery (b) $1.91 $0.03 $1.94 

Total cost $132.39 $1.97 $134.36 

 

(a) Cost of capital recovery was calculated at 6% of the total incremental costs. 

(b) Cost of capital recovery was calculated at 6%. Engines are assumed to remain in inventory for 3 months. 

 

Table 2: Incremental Consumer Cost of HDGE 

 

 

1971.1 

Costs 1971.5 Costs Total HD OBD Costs 

 (in dollars) (in dollars) (in dollars) 

Variable costs Component $30.00 $0.00 $30.00 

 Assembly $0.20 $0.00 $0.20 

 Warranty $0.07 $0.00 $0.07 

 Shipping $0.60 $0.00 $0.60 

Support costs Research $0.75 $0.00 $0.75 

 Engineering Support $0.00 $0.08 $0.08 

 Legal $0.00 $0.00 $0.00 

 Administrative $0.00 $0.16 $0.16 

Investment Mach. & equipment $0.00 $0.00 $0.00 

recovery costs Assembly plant changes $0.00 $0.00 $0.00 

 Development/Testing $0.96 $1.59 $2.55 

Capital recovery (a) $1.95 $0.11 $2.06 

Truck/Coach Builder costs Cost of capital recovery (b) $0.51 $0.03 $0.54 

Total cost $35.04 $1.97 $37.01 

 

(a) Cost of capital recovery was calculated at 6% of the total incremental costs. 

(b) Cost of capital recovery was calculated at 6%. Engines are assumed to remain in inventory for 3 months. 

 
90

C. COST EFFECTIVENESS OF THE PROPOSED REQUIREMENTS 

Based on the emission benefit analysis and the additional cost numbers identified 

above, the cost effectiveness of the OBD regulation was re-calculated. For the cost 

estimation, it was assumed that half of the cost was for PM emission benefit and the 

other half was for ROG+NOx benefit. Accordingly, the per engine cost to implement 

OBD ($134) was added to the per engine repair cost ($496) (from the cost analysis in 

the 2005 HD OBD Staff Report) for a total cost of $630 per engine. Splitting that in half, 

$315 was attributed to PM benefit for a cost-effectiveness of $22.50 per pound of PM. 

The other half of the cost was attributed to ROG+NOx benefit for a cost-effectiveness of 

$0.15 per pound of ROG+NOx. Both values compare favorably with the costeffectiveness of other, recently adopted regulations. 

As noted above, the proposed light-duty and medium-duty OBD II regulation revisions 

are not expected to add any significant cost to gasoline or diesel vehicles nor change 

any previously calculated emission benefits. Accordingly, the cost-effectiveness 

numbers calculated from the 2002 regulation update are still applicable. For reference, 

in 2002 staff calculated two separate cost-analyses for OBD II systems. The first 

covered the useful life period of the vehicle (typically the first 120,000 miles) and 

combined with the LEV II program, was $2.18 per pound of ROG + NOx reduced. The 

second analysis was for the second phase of the vehicle’s life, from 120,000 to 230,000 

miles, when increased reliance on OBD II is necessary to maintain low in-use vehicle 

emissions. That cost effectiveness was calculated to be $4.57 per pound of ROG + 

NOx reduced. The methodologies for both analyses were detailed in the 2002 OBD II 

staff report, which is incorporated by reference herein (a copy of which may be found at 

http://www.arb.ca.gov/regact/obd02/obd02.htm). 

XII. ECONOMIC IMPACT ANALYSIS 

Overall, the proposed amendments to the HD OBD and OBD II regulation are expected 

to have a negligible impact on the profitability of heavy-duty engine manufacturers and 

automobile manufacturers. It is anticipated that the proposed amendments would result 

in negligible costs to heavy-duty vehicle manufacturers. For light- and medium-duty 

vehicles, the manufacturers are large and mostly located outside of California with the 

exception of the New United Motor Manufacturing, Inc. (NUMMI), which is a joint 

venture between Toyota Motor Corporation and General Motors Corporation. The 

proposed changes involve minimal development and verification of software above what 

is already incorporated into HD OBD and OBD II systems. Staff believes, therefore, that 

the proposed requirements would cause no noticeable adverse impact in California 

employment, business status, and competitiveness. 

A. LEGAL REQUIREMENTS 

Section 11346.3 of the Government Code requires State agencies to assess the 

potential for adverse economic impacts on California business enterprises and 

individuals when proposing to adopt or amend any administrative regulation. Section 

43101 of the Health and Safety Code similarly requires that the Board consider the 
91

impact of adopted standards on the California economy. This assessment shall include 

a consideration of the impact of the proposed regulation on California jobs, business 

expansion, elimination, or creation, and the ability of California business to compete. 

B. AFFECTED BUSINESSES AND POTENTIAL IMPACTS 

Any business involved in manufacturing, purchasing, or servicing passenger cars, lightduty trucks, medium-duty vehicles, and heavy-duty engines and vehicles could be 

affected by the proposed amendments. Also affected are businesses that supply parts 

for these vehicles. 

There are 21 heavy-duty engine manufacturers, none of which is located in California. 

Of these businesses, two of the engine manufacturing companies are assumed to be 

“small businesses” (i.e., selling less than 150 engines per year based on California 

certification data). There are approximately 8 major heavy-duty vehicle manufacturers, 

but staff has been unable to obtain an estimation of the total number of vehicle 

manufacturers that manufacture and sell heavy-duty vehicles in California. Thus, staff 

is unable to determine how many of these companies are located in California and how 

many are considered “small businesses.” However, the cost related to vehicle 

manufacturers is determined to be negligible based on the minor effects these 

regulatory provisions might have on their operations. 

California accounts for only a small share of total nationwide light- and medium-duty 

motor vehicle and parts manufacturing. There are 34 companies worldwide that 

manufacture California-certified light- and medium-duty vehicles and heavy-duty 

gasoline engines. As stated, only one motor vehicle manufacturing plant is located in 

California, the NUMMI facility. 

C. POTENTIAL IMPACTS ON VEHICLE OPERATORS 

For heavy-duty engines and vehicles, the proposed amendments would provide OBD 

information and encourage manufacturers to build more durable engines, which would 

result in the need for fewer repairs and savings for vehicle owners. However, OBD is 

expected to detect malfunctions that may otherwise have gone undetected (and thus, 

unrepaired) by the vehicle owner. A single additional repair was estimated to occur on 

approximately two-thirds of the trucks over a 21 year lifetime as a result of OBD at an 

average cost of $741 per repair. This is a conservative cost estimate, since OBD will 

potentially result in savings by catching problems early before they adversely affect 

other components and systems in the engine. The proposed amendments are 

anticipated to have a negligible impact on new vehicle prices, since the calculated 

increase in retail price of an engine to meet OBD is less than one percent of the retail 

cost of the engine and less than 0.2 percent of the retail cost of a heavy-duty vehicle. 

For light- and medium-duty vehicles, the proposed amendments would provide 

improved OBD II information and encourage manufacturers to build more durable 

vehicles, which should result in the need for fewer vehicle repairs and savings for 

consumers. The proposed changes involve minimal development and verification of 
92

software above what is already incorporated into OBD II systems. Additionally, because 

manufacturers would be provided sufficient lead time to incorporate the minimal 

proposed changes, incorporation and verification of the revised OBD II software would 

be accomplished during the regular design process at virtually no additional cost. Any 

additional engineering resources needed to comply with the proposed program would 

be small, and when spread over several years of vehicle production, these costs would 

be negligible. Thus, the proposed amendments are anticipated to have a negligible 

impact on manufacturer costs and new vehicle prices. 

D. POTENTIAL IMPACTS ON BUSINESS COMPETITIVENESS 

The proposed amendments are not expected to adversely impact the ability of California 

businesses to compete with businesses in other states as the proposed standards are 

anticipated to have only a negligible impact on retail prices of new engines and vehicles. 

Additionally, U.S. EPA adopted federal OBD II and heavy-duty OBD requirements that 

are harmonized with those of ARB. Therefore, any increase in costs will also be 

experienced by non-California businesses due to federal requirements. Thus, any price 

increases of light-, medium-, and heavy-duty vehicles are not expected to dampen the 

demand for these vehicles in California relative to other states, since price increases 

would be the same nationwide. 

E. POTENTIAL IMPACTS ON EMPLOYMENT 

The proposed amendments are not expected to cause a noticeable change in California 

employment because California accounts for only a small share of motor vehicle, heavyduty engine, and parts manufacturing employment, and the minimal additional work 

done by heavy-duty vehicle manufacturers can be done with existing staff. 

However, some jobs may be created at heavy-duty engine manufacturing companies. 

Currently, heavy-duty engine manufacturers lack significant experience in designing and 

implementing OBD systems on heavy-duty engines. This may result in additional jobs 

for programmers and engineers. 

F. POTENTIAL IMPACT ON BUSINESS CREATION, ELIMINATION, OR 

EXPANSION 

The proposed amendments are not expected to affect business creation, elimination or 

expansion. 
93

REFERENCES 

Below is a list of documents and other information that the ARB staff relied upon in 

developing the Staff Report. 

1) Staff Report: Initial Statement of Reasons (ISOR): Technical Status and Revisions to 

Malfunction and Diagnostic System Requirements for 2004 and Subsequent Model 

Year Passenger Cars, Light-Duty Trucks, and Medium-Duty Vehicles and Engines 

(OBD II), March 8, 2002. 

2) Staff Report: Initial Statement of Reasons (ISOR): “Malfunction and Diagnostic 

System Requirements for 2010 and Subsequent Model Year Heavy-Duty Engines 

(HD OBD),” June 3, 2005. 

3) Staff Report: Initial Statement of Reasons (ISOR): “Technical Status and Revisions 

to Malfunction and Diagnostic System Requirements for Passenger Cars, Light-Duty 

Trucks, and Medium-Duty Vehicles and Engines (OBD II) and the Emission 

Warranty Regulation,” August 11, 2006 

Below is a list of documents newly incorporated by reference in the HD OBD and OBD II 

regulations. 

1) EMFAC2007 

2) EMFAC 2007 Technical Memo “EMFAC Modeling Change Technical Memo,” 

September 13, 2006 

3) International Standards Organization (ISO) 15765-4:2005 “Road Vehicles – 

Diagnostics on Controller Area Network (CAN) – Part 4: Requirements for emissionrelated systems,” January 2005. 

4) Society of Automotive Engineers (SAE) J1930 "Electrical/Electronic Systems 

Diagnostic Terms, Definitions, Abbreviations, and Acronyms – Equivalent to ISO/TR 

15031-2," October 2008. 

5) SAE J1978 "OBD II Scan Tool – Equivalent to ISO/DIS 15031-4:December 14, 

2001," April 2002. 

6) SAE J1979 "E/E Diagnostic Test Modes," May 2007.

7) SAE J2012 "Diagnostic Trouble Code Definitions," December 2007. 

8) SAE J2403 “Medium/Heavy-Duty E/E Systems Diagnosis Nomenclature,” August 

2007. 

9) SAE J1939 consisting of: 
94

J1939 Recommended Practice for a Serial Control and Communications Vehicle 

Network, March 2009; 

J1939/1 Recommended Practice for Control and Communications Network for 

On-Highway Equipment, September 2000; 

J1939/11 Physical Layer, 250K bits/s, Twisted Shielded Pair, September 2006; 

J1939/13 Off-Board Diagnostic Connector, March 2004; 

J1939/15 Reduced Physical Layer, 250K bits/sec, UN-Shielded Twisted Pair 

(UTP), August 2008; 

J1939/21 Data Link Layer, December 2006; 

J1939/31 Network Layer, April 2004; 

J1939/71 Vehicle Application Layer (Through February 2008), January 2009; 

J1939/73 Application Layer—Diagnostics, September 2006; 

J1939/81 Network Management, May 2003; and 

J1939/84 OBD Communications Compliance Test Cases For Heavy Duty 

Components and Vehicles, December 2008. 

10) SAE J1699-3 – “OBD II Compliance Test Cases”, May 2006. 

11) SAE J2534-1 – “Recommended Practice for Pass-Thru Vehicle Programming”, 

December 2004. 
95

APPENDIX I 

The following tables were used to support the cost estimates in Section XI. “Cost Impact 

of the Proposed Requirements” of the Staff Report. 
96

Manufacturer Self Testing Cost of Heavy-duty OBD Enforcement (Engineering Sup

Staff Number of Staff Staff Cost (a) 

Testing and 

Equipment Costs (d) Co

 (person yrs.) (in dollars) (in dollars) (dTest Cell Technician 0.13 $13,000 $262,662  Total 

Legal and Administrative costs 

 No. of Staff Number of Staff cost Co required years (in dollars) (doAdministrative 0.15 3 67,500  Total (a) Development cost includes personnel, overhead and other miscellaneous costs at a total rate of $

engineer and $100k/yr for a technician. (b) Testing Costs includes Labor Costs for Technicians needed to staff the Tests 

(c) Staff cost has been distributed over 72,000 engines per year for a total of 3 years. (d) Equipment costs have been distributed over 72,000 engines per year for a total of 3 years 
97

Incremental Consumer Cost of HDV OBD Enforcement Testing 

 

 HDV 

(in dollars) 

Variable costs Component $0.00 

 Assembly $0.00 

 Warranty $0.00 

 Shipping $0.00 

Support costs Research $0.00 

 Engineering Support $0.06 

 Legal $0.00 

 Administrative $0.16 

Investment Mach. & equipment $0.00 

recovery costs Assembly plant changes $0.00 

 Development/Testing $1.22 

Capital recovery (a) $0.09 

Truck/Coach Builder costs Cost of capital recovery (b) $0.02 

Total cost $1.55 

 

(a) Cost of capital recovery was calculated at 6% of the total incremental 

costs. 

(b) Cost of capital recovery was calculated at 6%. Engines are assumed to 

remain in inventory for 3 months. 
98

Long term Costs reg description 

# of engine families 

phase 1 test number 

phase 1 test percentage 

phase 2 test number 

phase 2 test percentage 

phase 3 test number 

phastest perce

1971.5 (c) 

manufacturer self testing 8 2 1 4 0.1 5 

cost per test hardware 

# of faults to be tested 

Engine dyno test cell hours 

Engine removal from Truck 

New engine install into truck 

Engine Install 

FTP/SET test Phase 1 

FTP/SET test Phases 2 &3 

Engine uninstall 

Procurement Cost per engine including aftertreatment

$21,488 16.3 130.4 1500 1500 2460 80196 9840 2460 $23,150 

Technician Manhours to run test - Phase 1 

Technician Manhours to run test - Phase 2 and 3 

cost per tech pY 

Hourly cost per tech 

Equipment/ test costs 

PY costs Total 

130.4 5 $100,000 

 $ 50 $ 262,662 

 $ 13,043 $275,705 
99

Parts Cost 

Task Description 

2016 Emissions/OBD 

Component List 

New 

Part 

Cost 

Limit 

Part 

Cost 

 

Fuel System 

fuel system injection quantity low/high Injector $200 $1,000 

fuel system pressure low/high Rail Pressure Sensor $200 $1,000 

fuel system injection timing advance/retard Injector $200 $1,000 

 

Misfire Monitor $0 $0 

 

Air Handling 

VGT Underboost/overboost/slow response VGT Actuator $500 $2,500 

CAC Undercooling Charge Air Cooler $25 $125 

 

EGR 

EGR low/high flow EGR Valve Actuator $500 $2,500 

EGR Undercooling EGR Cooler $25 $125 

 

Oxidation Catalyst 

NMHC cat conversion efficiency oxidation catalyst $1,000 $5,000 

 

SCR Catalyst 

SCR NOx cat conversion efficiency SCR Catalyst $2,000 $10,000

SCR reductant injection performance Urea Injector $300 $1,500 

 

PM Filter 

PM filter leak/missing substrate PM Filter $5,000 $6,000 

PM filter regeneration frequent PM Filter $5,000 $6,000 

PM filter regeneration incomplete PM Filter $5,000 $0 

NMHC conversion of catalyst oxidation catalyst $1,000 $5,000 

Active injection (in exhaust) (in-cylinder no 

cost) computer mod to post inj $0 $0 

 

NOx Sensors 

NOx sensor performance NOx sensor $75 $375 

NOx sensor offset NOx sensor $75 $375 

NOx sensor monitoring capability NOx sensor $75 $375 

 

Sensor Heaters 

Sensor heater performance 

computer mods to induce 

fault $0 $0 

 

ECT Sensor/Thermostat 

t-stat monitor warm-up performance $20 $100 

 

Total $42,975
i

ATTACHMENT A 

California Code of Regulations, Title 13, section 1971.1, On-Board Diagnostic 

System Requirements for 2010 and Subsequent Model-Year Heavy-Duty 

Engines (HD OBD) 

Set forth below are proposed amendments to California Code of Regulations, 

Title 13, §1971.1. The proposed amendments are shown in single underline to 

indicate additions and single strikeout to indicate deletions. 
ii

Table of Contents 

(a) PURPOSE................................................................................................................. 1 

(b) APPLICABILITY ...................................................................................................... 1 

(c) DEFINITIONS........................................................................................................... 1 

(d) GENERAL REQUIREMENTS................................................................................ 7 

(1) The OBD System. ............................................................................................ 7 

(2) MIL and Fault Code Requirements. .............................................................. 7 

(3) Monitoring Conditions.................................................................................... 14 

(4) In-Use Monitor Performance Ratio Definition............................................ 16 

(5) Standardized tracking and reporting of monitor performance. ............... 21 

(6) Malfunction Criteria Determination.............................................................. 23 

(7) Implementation Schedule ............................................................................. 24 

(e) MONITORING REQUIREMENTS FOR DIESEL/COMPRESSION-IGNITION 

ENGINES ........................................................................................................................ 26 

(1) FUEL SYSTEM MONITORING.................................................................... 26 

(2) MISFIRE MONITORING ............................................................................... 29 

(3) EXHAUST GAS RECIRCULATION (EGR) SYSTEM MONITORING... 32 

(4) BOOST PRESSURE CONTROL SYSTEM MONITORING.................... 35 

(5) NON-METHANE HYDROCARBON (NMHC) CONVERTING CATALYST

MONITORING ............................................................................................................ 39 

(6) OXIDES OF NITROGEN (NOx) CONVERTING CATALYST 

MONITORING............................................................................................................. 41 

(7) NOx ADSORBER MONITORING................................................................ 44 

(8) PARTICULATE MATTER (PM) FILTER MONITORING.......................... 47 

(9) EXHAUST GAS SENSOR MONITORING................................................. 49

(10) VARIABLE VALVE TIMING AND/OR CONTROL (VVT) SYSTEM 

MONITORING............................................................................................................. 53 

(11) COLD START EMISSION REDUCTION STRATEGY MONITORING.. 54 

(f) MONITORING REQUIREMENTS FOR GASOLINE/SPARK-IGNITED 

ENGINES ........................................................................................................................ 55 

(1) FUEL SYSTEM MONITORING.................................................................... 55 

(2) MISFIRE MONITORING ............................................................................... 58 

(3) EXHAUST GAS RECIRCULATION (EGR) SYSTEM MONITORING... 64 

(4) COLD START EMISSION REDUCTION STRATEGY MONITORING.. 65 

(5) SECONDARY AIR SYSTEM MONITORING............................................. 66 

(6) CATALYST MONITORING........................................................................... 67 

(7) EVAPORATIVE SYSTEM MONITORING ................................................. 69

(8) EXHAUST GAS SENSOR MONITORING................................................. 70

(9) VARIABLE VALVE TIMING AND/OR CONTROL (VVT) SYSTEM 

MONITORING............................................................................................................. 74 

(g) MONITORING REQUIREMENTS FOR ALL ENGINES.................................. 75 

(1) ENGINE COOLING SYSTEM MONITORING........................................... 75 

(2) CRANKCASE VENTILATION (CV) SYSTEM MONITORING ................ 78 

(3) COMPREHENSIVE COMPONENT MONITORING................................. 80 
iii

(4) OTHER EMISSION CONTROL SYSTEM MONITORING ...................... 87 

(5) EXCEPTIONS TO MONITORING REQUIREMENTS.............................. 87 

(h) STANDARDIZATION REQUIREMENTS........................................................... 89 

(1) Reference Documents:.................................................................................. 89 

(2) Diagnostic Connector:................................................................................... 90 

(3) Communications to a Scan Tool:................................................................. 92 

(4) Required Emission Related Functions: ...................................................... 92 

(5) Tracking Requirements:.............................................................................. 102 

(6) Service Information:..................................................................................... 105 

(7) Exceptions to Standardization Requirements. ........................................ 106 

(i) MONITORING SYSTEM DEMONSTRATION REQUIREMENTS FOR 

CERTIFICATION.......................................................................................................... 106 

(1) General. ......................................................................................................... 106 

(2) Selection of Test Engines:.......................................................................... 106 

(3) Required Testing:......................................................................................... 109 

(4) Testing Protocol: .......................................................................................... 113 

(5) Evaluation Protocol:..................................................................................... 115 

(6) Confirmatory Testing: .................................................................................. 117 

(j) CERTIFICATION DOCUMENTATION............................................................. 118 

(k) DEFICIENCIES .................................................................................................... 121 

(l) PRODUCTION ENGINE/VEHICLE EVALUATION TESTING..................... 122 

(1) Verification of Standardized Requirements. ............................................ 122 

(2) Verification of Monitoring Requirements. ................................................. 125 

(3) Verification and Reporting of In-use Monitoring Performance.............. 126 
§1971.1. On-Board Diagnostic System Requirements--2010 and Subsequent 

Model-Year Heavy-Duty Engines 

(a) PURPOSE 

The purpose of this regulation is to establish emission standards and other 

requirements for onboard diagnostic systems (OBD systems) that are installed on 

2010 and subsequent model-year engines certified for sale in heavy-duty 

applications in California. The OBD systems, through the use of an onboard 

computer(s), shall monitor emission systems in-use for the actual life of the engine 

and shall be capable of detecting malfunctions of the monitored emission systems, 

illuminating a malfunction indicator light (MIL) to notify the vehicle operator of 

detected malfunctions, and storing fault codes identifying the detected malfunctions. 

(b) APPLICABILITY 

Except as specified in section (d)(7) and elsewhere in this regulation (title 13, CCR 

section 1971.1), all 2010 and subsequent model-year heavy-duty engines shall be 

equipped with an OBD system that has been certified by the Executive Officer as

and shall meeting all applicable requirements of this regulation (title 13, CCR section 

1971.1).1 

(c) DEFINITIONS 

 “Actual life” refers to the entire period that an engine is operated on public roads 

in California up to the time an engine is retired from use. 

“Applicable standards” refers to the specific exhaust emission standards or 

family emission limits (FEL), including the Federal Test Procedure (FTP) and 

Supplemental Emission Test (SET) standards, to which the engine is certified. 

“Base fuel schedule” refers to the fuel calibration schedule programmed into the 

Powertrain Control Module or programmable read-only memory (PROM) when 

manufactured or when updated by some off-board source, prior to any learned 

on-board correction. 

“Auxiliary Emission Control Device (AECD)” refers to any approved AECD (as 

defined by 40 Code of Federal Regulations (CFR) 86.082-2 and 86.094-2).

“Emission Increasing Auxiliary Emission Control Device (EI-AECD)” refers to 

any approved AECD that: reduces the effectiveness of the emission control 

system under conditions which may reasonably be expected to be encountered 

in normal vehicle operation and use; and the need for the AECD is justified in 

terms of protecting the vehicle against damage or accident. An AECD that is 

certified as an NTE deficiency shall not be considered an EI-AECD. An AECD 

that does not sense, measure, or calculate any parameter or command or trigger 

any action, algorithm, or alternate strategy shall not be considered an EI-AECD. 

An AECD that is activated solely due to any of the following conditions shall not 

be considered an EI-AECD: (1) operation of the vehicle above 8000 feet in 

elevation; (2) ambient temperature; (3) when the engine is warming up and is not 

reactivated once the engine has warmed up in the same driving cycle; (4) failure 

detection (storage of a fault code) by the OBD system; (5) execution of an OBD 

monitor; or (6) execution of an infrequent regeneration event. 

 

1

 Unless otherwise noted, all section references refer to section 1971.1 of title 13, CCR. 
2

“Calculated load value” refers to the percent of engine capacity being used and 

is defined in Society of Automotive Engineers (SAE) J1979 "E/E Diagnostic Test 

Modes – Equivalent to ISO/DIS 15031-5:April 30, 2002," April 2002May 2007 (SAE 

J1979), incorporated by reference (section (h)(1.4)). For diesel applications, the 

calculated load value is determined by the ratio of current engine output torque to 

maximum engine output torque at current engine speed as defined by parameter 

definition 5.2.1.7 of SAE J1939-71 “Vehicle Application Layer (Through February 

2008),” January 2009. 

“Confirmed fault code,” for purposes of engines using International Standards 

Organization (ISO) 15765-4, is defined as the diagnostic trouble code stored when 

an OBD system has confirmed that a malfunction exists (e.g., typically on the 

second driving cycle that the malfunction is detected) in accordance with the 

requirements of sections (d)(2), (f), (g), and (h)(4.4). 

“Continuously,” if used in the context of monitoring conditions for circuit 

continuity, lack of circuit continuity, circuit faults, and out-of-range values, means 

monitoring is always enabled, unless alternate enable conditions have been 

approved by the Executive Officer in accordance with section (d)(3.1.1), and

sampling of the signal used for monitoring occurs at a rate no less than two samples 

per second. If a computer input component is sampled less frequently for engine 

control purposes, the signal of the component may instead be evaluated each time 

sampling occurs. 

“Deactivate” means to turn-off, shutdown, desensitize, or otherwise make 

inoperable through software programming or other means during the actual life of 

the engine. 

“Diagnostic or emission critical” electronic control unit refers to the engine and 

any other on-board electronic powertrain control unit containing software that: (1) 

has primary control over any of the monitors required by sections (e)(1) through 

(f)(9), (g)(1) through (g)(2), and (g)(4); or (2) excluding anti-lock brake system (ABS) 

control units or stability/traction control units, has primary control over the 

diagnostics for more than two of the components required to be monitored by 

section (g)(3). For purposes of criteria (2) above, all glow plugs in an engine shall 

be considered “one” component in lieu of each glow plug being considered a 

separate component.

“Diesel engine” refers to an engine using a compression ignition thermodynamic 

cycle. 

“Driving cycle” is defined as a trip that meets any of the four conditions below: 

(a) Begins with engine start and ends with engine shutoff; 

(b) Begins with engine start and ends after four hours of continuous engine-on 

operation; 

(c) Begins at the end of the previous four hours of continuous engine-on 

operation and ends after four hours of continuous engine-on operation; or 

(d) Begins at the end of the previous four hours of continuous engine-on 

operation and ends with engine shutoff. 

For monitors that run during engine-off conditions, the period of engine-off time 

following engine shutoff and up to the next engine start may be considered part of 

the driving cycle for conditions (a) and (d). For vehicles that employ engine shutoff 

strategies that do not require the vehicle operator to restart the engine to continue 

driving (e.g., hybrid bus with engine shutoff at idle), the manufacturer may request 
3

Executive Officer approval to use an alternate definition for driving cycle (e.g., key 

on and key off). Executive Officer approval of the alternate definition shall be based 

on equivalence to engine startup and engine shutoff signaling the beginning and 

ending of a single driving event for a conventional vehicle. Engine restarts following 

an engine shut-off that has been neither commanded by the vehicle operator nor by 

the engine control strategy but caused by an event such as an engine stall may be 

considered a new driving cycle or a continuation of the existing driving cycle. For 

engines that are not likely to be routinely operated for long continuous periods of 

time, a manufacturer may also request Executive Officer approval to use an 

alternate definition for driving cycle (e.g., solely based on engine start and engine 

shutoff without regard to four hours of continuous engine-on time). Executive 

Officer approval of the alternate definition shall be based on manufacturer-submitted 

data and/or information demonstrating the typical usage, operating habits, and/or 

driving patterns of these vehicles. 

 “Engine family” means a grouping of vehicles or engines in a manufacturer’s 

product line determined in accordance with 40 CFR 86.098-24. 

“Engine rating” means a unique combination of displacement, rated power, 

calibration (fuel, emission, and engine control), AECDs, and other engine and 

emission control components within an engine family. 

“OBD parent rating” means the specific engine rating selected according to 

section (d)(7.1.1) or (d)(7.2.2)(B) for compliance with section 1971.1. 

“OBD child rating” means an engine rating (other than the OBD parent rating) 

within the engine family containing the OBD parent rating selected according to 

section (d)(7.1.1) or an engine rating within the OBD group(s) defined according 

to section (d)(7.2.1) and subject to section (d)(7.2.3). 

“Engine misfire” means lack of combustion in the cylinder due to absence of 

spark, poor fuel metering, poor compression, or any other cause. This does not 

include lack of combustion events in non-active cylinders due to default fuel shut-off 

or cylinder deactivation strategies. 

“Engine start” is defined as the point when the engine reaches a speed 150 rpm 

below the normal, warmed-up idle speed (as determined in the drive position for 

vehicles equipped with an automatic transmission). For hybrid vehicles or for 

engines employing alternate engine start hardware or strategies (e.g., integrated 

starter and generators.), the manufacturer may request Executive Officer approval 

to use an alternate definition for engine start (e.g., ignition key “on”). Executive 

Officer approval of the alternate definition shall be based on equivalence to an 

engine start for a conventional vehicle. 

 “Family Emission Limit (FEL)” refers to the exhaust emission levels to which an

engine family is certified under the averaging, banking, and trading program 

incorporated by reference in title 13, CCR section 1956.8.

“Fault memory” means information pertaining to malfunctions stored in the 

onboard computer, including fault codes, stored engine conditions, and MIL status. 

“Federal Test Procedure (FTP) test” refers to an exhaust emission test 

conducted according to the test procedures incorporated by reference in title 13, 

CCR section 1956.8(b) and (d) that is used to determine compliance with the FTP 

standard to which an engine is certified. 

“FTP cycle”. For engines certified on an engine dynamometer, FTP cycle 

refers to the engine dynamometer schedule in 40 CFR appendix 1 of part 86, 
4

section (f)(1), entitled, “EPA Engine Dynamometer Schedule for Heavy-Duty 

Otto-Cycle Engines,” or section (f)(2), entitled, “EPA Engine Dynamometer 

Schedule for Heavy-Duty Diesel Engines.” 

“FTP standard” refers to the certification exhaust emission standards and test 

procedures applicable to the FTP cycle incorporated by reference in title 13, 

CCR sections 1956.8(b) and (d) to which the engine is certified. 

“Fuel trim” refers to feedback adjustments to the base fuel schedule. Short-term 

fuel trim refers to dynamic or instantaneous adjustments. Long-term fuel trim refers 

to much more gradual adjustments to the fuel calibration schedule than short-term 

trim adjustments. 

“Functional check” for an output component or system means verification of 

proper response of the component and system to a computer command. 

“Gasoline engine” refers to an Otto-cycle engine or an alternate-fueled engine. 

“Heavy-duty engine” means an engine that is used to propel a heavy-duty 

vehicle. 

“Heavy-duty vehicle” means any motor vehicle having a manufacturer’s gross 

vehicle weight rating (GVWR) greater than 14,000 pounds. 

“Ignition Cycle” means a driving cycle that begins with engine start, meets the 

engine start definition for at least two seconds plus or minus one second, and ends 

with engine shutoff. 

“Keep-alive memory (KAM),” for the purposes of this regulation, is defined as a 

type of memory that retains its contents as long as power is provided to the onboard control unit. KAM is not erased upon shutting off the engine but may be 

erased if power to the on-board control unit is interrupted (e.g., vehicle battery 

disconnected, fuse to control unit removed). In some cases, portions of KAM may 

be erased with a scan tool command to reset KAM. 

“Key on, engine off position” refers to a vehicle with the ignition key in the engine 

run position (not engine crank or accessory position) but with the engine not 

running. 

“Malfunction” means any deterioration or failure of a component that causes the 

performance to be outside of the applicable limits in sections (e) through (g). 

“Manufacturer” for the purpose of this regulation means the holder of the 

Executive Order for the engine family. 

“MIL-on fault code,” for purposes of engines using Society of Automotive 

Engineers (SAE) J1939, refers to the diagnostic trouble code stored when an OBD 

system has confirmed that a malfunction exists (e.g., typically on the second driving 

cycle that the malfunction is detected) and has commanded the MIL on in 

accordance with the requirements of sections (d)(2), (e), (g), and (h)(4.4). 

“Non-volatile random access memory (NVRAM),” for the purposes of this 

regulation, is defined as a type of memory that retains its contents even when power 

to the on-board control unit is interrupted (e.g., vehicle battery disconnected, fuse to 

control unit removed). NVRAM is typically made non-volatile either by use of a 

back-up battery within the control unit or through the use of an electrically erasable 

and programmable read-only memory (EEPROM) chip.

“Not-To-Exceed (NTE) control area” refers to the bounded region of the engine’s 

torque and speed map, as defined in 40 CFR 86.1370-2007, where emissions must 

not exceed a specific emission cap for a given pollutant under the NTE requirement. 
5

“Manufacturer-specific NOx NTE carve-out area” refers to regions within the 

NTE control area for NOx where the manufacturer has limited NTE testing as 

allowed by 40 CFR 86.1370-20071(b)(7). 

“Manufacturer-specific PM NTE carve-out area” refers to regions within the 

NTE control area for PM where the manufacturer has limited NTE testing as 

allowed by 40 CFR 86.1370-20071(b)(7). 

“NTE deficiency” refers to regions or conditions within the NTE control area 

for NOx or PM where the manufacturer has received a deficiency as allowed by 

40 CFR 86.007-11(a)(4)(iv). 

“Non-volatile random access memory (NVRAM),” for the purposes of this 

regulation, is defined as a type of memory that retains its contents even when power 

to the on-board control unit is interrupted (e.g., vehicle battery disconnected, fuse to 

control unit removed). NVRAM is typically made non-volatile either by use of a 

back-up battery within the control unit or through the use of an electrically erasable 

and programmable read-only memory (EEPROM) chip.

“OBD group” refers to a combination of engines, engine families, or engine 

ratings that use the same OBD strategies and similar calibrations. A manufacturer 

is required to submit a grouping plan for Executive Officer review and approval 

detailing the OBD groups and the engine families and engine ratings within each 

group for a model year. 

“Pending fault code” is defined as the diagnostic trouble code stored upon the 

initial detection of a malfunction (e.g., typically on a single driving cycle) prior to 

illumination of the MIL in accordance with the requirements of sections (d)(2), (e) 

through (g), and (h)(4.4). 

“Permanent fault code” is defined as a confirmed or MIL-on fault code that is 

currently commanding the MIL on and is stored in NVRAM as specified in sections 

(d)(2) and (h)(4.4). 

“Percentage of misfire” as used in sections (e)(2) and (f)(2) means the 

percentage of misfires out of the total number of firing events for the specified 

interval. 

“Power Take-Off (PTO) unit” refers to an engine driven output provision for the 

purposes of powering auxiliary equipment (e.g., a dump-truck bed, aerial bucket, or 

tow-truck winch). 

“Previously MIL-on fault code,” for purposes of engines using SAE J1939, is 

defined as the diagnostic trouble code stored when an OBD system has confirmed 

that a malfunction no longer exists (e.g., after the third consecutive driving cycle in 

which the corresponding monitor runs and the malfunction is not detected), 

extinguishes the MIL, and erases the corresponding MIL-on fault code in 

accordance with the requirements of sections (d)(2), (e), (g), and (h)(4.4). 

“Rationality fault diagnostic” for an input component means verification of the 

accuracy of the input signal while in the range of normal operation and when 

compared to all other available information. 

“Redline engine speed” shall be defined by the manufacturer as either the 

recommended maximum engine speed as normally displayed on instrument panel 

tachometers or the engine speed at which fuel shutoff occurs. 

“Response rate” for exhaust gas sensors refers to the delay from when the 

sensor is exposed to a different make-up of exhaust gas constituents until it outputs 

a signal reflecting the different make-up of exhaust gas constituents. For example, 
6

for oxygen sensors, response rate is the delay from when the oxygen sensor is 

exposed to a change in exhaust gas from richer/leaner than stoichiometric to 

leaner/richer than stoichiometric to the time when the oxygen sensor indicates the 

lean/rich condition. Similarly, for wide-range air-fuel (A/F) sensors, response rate is 

the delay from when the sensor is exposed to a different A/F ratio to the time it 

indicates the different A/F ratio. For NOx and PM sensors, response rate is the 

delay from when the sensor is exposed to a different NOx or PM exhaust gas level 

until it indicates the different NOx or PM exhaust gas levelbetween a change in 

sensor output in response to a commanded change in the sensed exhaust gas 

parameter. Specifically, the response rate is the delay from the time when the 

exhaust gas sensor is exposed to an increase/decrease of the exhaust gas 

parameter to the time when the exhaust gas sensor indicates the increase/decrease 

of the sensed parameter (e.g., for an oxygen sensor, response rate is the delay from 

the time when the sensor is exposed to a change in exhaust gas from richer/leaner 

than stoichiometric to leaner/richer than stoichiometric to the time when the sensor 

indicates the lean/rich condition; for a NOx sensor, response rate is the delay from 

the time when the sensor is exposed to an increase/decrease in NOx concentration 

to the time when the sensor indicates the increased/decreased NOx concentration). 

“Secondary air” refers to air introduced into the exhaust system by means of a 

pump or aspirator valve or other means that is intended to aid in the oxidation of HC 

and CO contained in the exhaust gas stream. 

“Similar conditions” as used in sections (e)(1), (e)(2), (f)(1), and (f)(2) means 

engine conditions having an engine speed within 375 rpm, load conditions within 20 

percent, and the same warm-up status (i.e., cold or hot) as the engine conditions 

stored pursuant to (e)(1.4.2)(E), (e)(2.4.2)(C), (f)(1.4.5), and (f)(2.4.4). The 

Executive Officer may approve other definitions of similar conditions based on 

comparable timeliness and reliability in detecting similar engine operation. 

“Start of production” is the time when the manufacturer has produced two 

percent of the projected volume for the engine or vehicle, whichever is being 

evaluated in accordance with section (l). 

“Supplemental Emission Test (SET) cycle” refers to the driving schedule defined 

as the “supplemental steady state emission test” in 40 CFR 86.1360-2007. 

“SET standard” refers to the certification exhaust emission standards and test 

procedures applicable to the SET cycle incorporated by reference in title 13, CCR 

sections 1956.8(b) and (d) to which the engine is certified 

“Warm-up cycle” means sufficient vehicle operation such that the coolant 

temperature has risen by at least 40 degrees Fahrenheit from engine start and 

reaches a minimum temperature of at least 160 degrees Fahrenheit (140 degrees 

Fahrenheit for applications with diesel engines). 

“Weighted sales number” means a manufacturer’s projected sales number for

engines to be used in California heavy-duty vehicles multiplied by a weight class 

factor. Sales numbers for diesel engines for heavy-duty vehicles less than 19,499 

pounds GVWR shall be multiplied by 1.0. Sales numbers for diesel engines for 

heavy-duty vehicles from 19,500 to 33,000 pounds shall be multiplied by 1.68. 

Sales numbers for diesel engines for heavy-duty vehicles greater than 33,000

pounds and urban buses shall be multiplied by 3.95. Sales numbers for all gasoline 

engines for heavy-duty vehicles shall be multiplied by 1.0.
7

(d) GENERAL REQUIREMENTS 

Section (d) sets forth the general requirements of the OBD system. Specific 

performance requirements for components and systems that shall be monitored are 

set forth in sections (e) through (g) below. The OBD system is required to detect all 

malfunctions specified in sections (e) through (g). However, except as specified 

elsewhere, the OBD system is not required to use a unique monitor to detect each 

malfunction specified. 

(1) The OBD System. 

(1.1) If a malfunction is present as specified in sections (e) through (g), the OBD 

system shall detect the malfunction, store a pending, confirmed, MIL-on, or 

previously MIL-on fault code in the onboard computer’s memory, and 

illuminate the MIL as required. 

(1.2) The OBD system shall be equipped with a standardized data link connector 

to provide access to the stored fault codes as specified in section (h). 

(1.3) The OBD system shall be designed to operate, without any required 

scheduled maintenance, for the actual life of the engine in which it is installed 

and may not be programmed or otherwise designed to deactivate based on 

age and/or mileage of the vehicle during the actual life of the engine. This 

section is not intended to alter existing law and enforcement practice 

regarding a manufacturer’s liability for an engine beyond its useful life, except 

where an engine has been programmed or otherwise designed so that an 

OBD system deactivates based on age and/or mileage of the engine. 

(1.4) Computer-coded engine operating parameters may not be changeable 

without the use of specialized tools and procedures (e.g. soldered or potted 

computer components or sealed (or soldered) computer enclosures). Subject 

to Executive Officer approval, manufacturers may exempt from this 

requirement those product lines that are unlikely to require protection. 

Criteria to be evaluated in making an exemption include current availability of 

performance chips, performance capability of the engine, and sales volume.

(2) MIL and Fault Code Requirements. 

(2.1) MIL Specifications. 

(2.1.1) The MIL shall be located on the driver's side instrument panel and be of 

sufficient illumination and location to be readily visible under all lighting 

conditions and shall be amber in color when illuminated. The MIL, when 

illuminated, shall display the International Standards Organization (ISO) 

engine symbol. There shall be only one MIL used to indicate all faults 

detected by the OBD system on a single vehicle. 

(2.1.2) The MIL shall illuminate in the key on, engine off position before engine 

cranking to indicate that the MIL is functional. The MIL shall continuously 

illuminate during this functional check for a minimum of 15-20 seconds. 

During this functional check of the MIL, the data stream value for MIL 

status shall indicate commanded off (see section (h)(4.2)) unless the MIL 

has also been commanded on for a detected malfunction. This functional 

check of the MIL is not required during vehicle operation in the key on, 

engine off position subsequent to the initial engine cranking of an ignition 

cycle (e.g., due to an engine stall or other non-commanded engine 

shutoff). 
8

(2.1.3) At the manufacturer's option, the MIL may be used to indicate readiness 

status in a standardized format (see section (h)(4.1.3)) in the key on, 

engine off position. 

(2.1.4) A manufacturer may request Executive Officer approval to also use the 

MIL to indicate which, if any, fault codes are currently stored (e.g., to 

“blink” the stored codes). The Executive Officer shall approve the request 

upon determining that the manufacturer has demonstrated that the 

method used to indicate the fault codes will not be unintentionally 

activated during a California inspection test or during routine driver 

operation. 

(2.1.5) The MIL may not be used for any purpose other than specified in this 

regulation. 

(2.2) MIL Illumination and Fault Code Storage Protocol. 

(2.2.1) For vehicles using the ISO 15765-4 protocol for the standardized functions 

required in section (h): 

(A) Upon detection of a malfunction, the OBD system shall store a pending 

fault code within 10 seconds indicating the likely area of the malfunction. 

(B) After storage of a pending fault code, if the identified malfunction is again 

detected before the end of the next driving cycle in which monitoring 

occurs, the OBD system shall illuminate the MIL continuously, keep the 

pending fault code stored, and store a confirmed fault code within 10 

seconds. If a malfunction is not detected before the end of the next 

driving cycle in which monitoring occurs (i.e., there is no indication of the 

malfunction at any time during the driving cycle), the corresponding 

pending fault code set according to section (d)(2.2.1)(A) shall be erased at 

the end of the driving cycle. 

(C) A manufacturer may request Executive Officer approval to employ 

alternate statistical MIL illumination and fault code storage protocols to 

those specified in these requirements. The Executive Officer shall grant 

approval upon determining that the manufacturer has provided data 

and/or engineering evaluation that demonstrate that the alternative 

protocols can evaluate system performance and detect malfunctions in a 

manner that is equally effective and timely. Strategies requiring on 

average more than six driving cycles for MIL illumination may not be 

accepted. 

(D) The OBD system shall store and erase “freeze frame” conditions (as 

defined in section (h)(4.3)) present at the time a malfunction is detected. 

The storage and erasure of freeze frame conditions shall be done in 

conjunction with the storage and erasure of either pending or confirmed 

fault codes as required elsewhere in section (d)(2.2). 

(E) The OBD system shall illuminate the MIL and store a confirmed fault code 

within 10 seconds to inform the vehicle operator whenever the engine 

enters a default or “limp home” mode of operation that can affect 

emissions or the performance of the OBD system or in the event of a 

malfunction of an on-board computer(s) itself that can affect the 

performance of the OBD system. If the default or “limp home” mode of 

operation is recoverable (i.e., the diagnostic or control strategy that 

caused the default or “limp home” mode of operation can run on the next 
9

driving cycle and confirm the presence of the condition that caused the 

default or “limp home” operationoperation automatically returns to normal 

at the beginning of the following ignition cycle), the OBD system may, in 

lieu of illuminating the MIL within 10 seconds on the first driving cycle 

where the default or “limp home” mode of operation is entered, delay 

illumination of wait and illuminate the MIL until the condition causing the 

default or “limp home” mode of operation is again detected before the end 

of the next driving cycle and store the confirmed fault code only if the 

default or “limp home” mode of operation is again entered before the end 

of the next ignition cycle in lieu of illuminating the MIL within 10 seconds 

on the first driving cycle where the default or “limp home” mode of 

operation is entered. 

(F) Before the end of an ignition cycle, the OBD system shall store confirmed 

fault codes that are currently causing the MIL to be illuminated in NVRAM 

as permanent fault codes (as defined in section (h)(4.4.1)(F)). 

(2.2.2) For vehicles using the SAE J1939 protocol for the standardized functions 

required in section (h): 

(A) Upon detection of a malfunction, the OBD system shall store a pending 

fault code within 10 seconds indicating the likely area of the malfunction. 

(B) After storage of a pending fault code, if the identified malfunction is again 

detected before the end of the next driving cycle in which monitoring 

occurs, the OBD system shall illuminate the MIL continuously, erase the 

pending fault code, and store a MIL-on fault code within 10 seconds. If a 

malfunction is not detected before the end of the next driving cycle in 

which monitoring occurs (i.e., there is no indication of the malfunction at 

any time during the driving cycle), the corresponding pending fault code 

set according to section (d)(2.2.2)(A) shall be erased at the end of the 

driving cycle. 

(C) A manufacturer may request Executive Officer approval to employ 

alternate statistical MIL illumination and fault code storage protocols to 

those specified in these requirements. The Executive Officer shall grant 

approval upon determining that the manufacturer has provided data 

and/or engineering evaluation that demonstrate that the alternative 

protocols can evaluate system performance and detect malfunctions in a 

manner that is equally effective and timely. Strategies requiring on 

average more than six driving cycles for MIL illumination may not be 

accepted. 

(D) Storage and erasure of freeze frame conditions.

(i) The OBD system shall store and erase “freeze frame” conditions (as 

defined in section (h)(4.3)) present at the time a malfunction is 

detected. 

(ii) The OBD system shall store freeze frame conditions in conjunction 

with the storage of a pending fault code. 

(iii) If the pending fault code is erased in the next driving cycle in which 

monitoring occurs and a malfunction is not detected (as described 

under section (d)(2.2.2)(B)), the OBD system may erase the 

corresponding freeze frame conditions. 
10

(iv) If the pending fault code matures to a MIL-on fault code (as described 

under section (d)(2.2.2)(B)), the OBD system shall either retain the 

currently stored freeze frame conditions or replace the stored freeze 

frame conditions with freeze frame conditions regarding the MIL-on 

fault code. The OBD system shall erase the freeze frame information 

in conjunction with the erasure of the previously MIL-on fault code (as 

described under section (d)(2.3.2)(C)). 

(E) The OBD system shall illuminate the MIL and store a MIL-on fault code 

within 10 seconds to inform the vehicle operator whenever the engine 

enters a default or “limp home” mode of operation that can affect 

emissions or the performance of the OBD system or in the event of a 

malfunction of an on-board computer(s) itself that can affect the 

performance of the OBD system. If the default or “limp home” mode of 

operation is recoverable (i.e., the diagnostic or control strategy that 

caused the default or “limp home” mode of operation can run on the next 

driving cycle and confirm the presence of the condition that caused the 

default or “limp home” operationoperation automatically returns to normal 

at the beginning of the following ignition cycle), the OBD system may, in 

lieu of illuminating the MIL within 10 seconds on the first driving cycle 

where the default or “limp home” mode of operation is entered, delay 

illumination of the MIL until the condition causing the default or “limp 

home” mode of operation is again detected before the end of the next 

driving cycle wait and illuminate the MIL only if the default or “limp home” 

mode of operation is again entered before the end of the next ignition 

cycle in lieu of illuminating the MIL within 10 seconds on the first driving 

cycle where the default or “limp home” mode of operation is entered. 

(F) Before the end of an ignition cycle, the OBD system shall store MIL-on 

fault codes that are currently causing the MIL to be illuminated in NVRAM 

as permanent fault codes (as defined in section (h)(4.4.2)(F)). 

(2.3) MIL Extinguishing and Fault Code Erasure Protocol.

(2.3.1) For vehicles using the ISO 15765-4 protocol for the standardized functions 

required in section (h): 

(A) Extinguishing the MIL. Except as otherwise provided in sections 

(f)(1.4.6), (f)(2.4.5), and (f)(7.4.2) for fuel system, misfire, and evaporative 

system malfunctions, once the MIL has been illuminated, it may be 

extinguished after three subsequent sequential driving cycles during which 

the monitoring system responsible for illuminating the MIL functions and 

the previously detected malfunction is no longer present provided no other 

malfunction has been detected that would independently illuminate the 

MIL according to the requirements outlined above. 

(B) Erasing a confirmed fault code. The OBD system may erase a confirmed 

fault code if the identified malfunction has not been again detected in at 

least 40 engine warm-up cycles and the MIL is presently not illuminated 

for that malfunction. 

(C) Erasing a permanent fault code. The OBD system shall erase a 

permanent fault code only if either of the following conditions occur:

(i) If the OBD system is commanding the MIL on, the OBD system shall 

erase a permanent fault code only if Tthe OBD system itself 
11

determines that the malfunction that caused the confirmed permanent 

fault code to be stored is no longer present and is not commanding the 

MIL on, concurrent withpursuant to the requirements of section 

(d)(2.3.1)(A) (which for the purposes of this section shall apply to all 

monitors). Erasure of the permanent fault code shall occur in 

conjunction with extinguishing the MIL or no later than the start of the 

first drive cycle that begins with the MIL commanded off., or

(ii) Subsequent to a clearing of theIf all fault information in the on-board 

computer other than the permanent fault code has been cleared (i.e., 

through the use of a scan tool or battery disconnect) and the OBD 

system is not commanding the MIL on, the diagnostic for the 

malfunction that caused the permanent fault code to be stored has 

fully executed (i.e., has executed the minimum number of checks 

necessary for MIL illumination) and determined the malfunction is no 

longer present.:

a. Except as provided for in section (d)(2.3.1)(C)(ii)c., if the monitor of 

the malfunction that caused the permanent fault code to be stored 

is subject to the minimum ratio requirements of section (d)(3.2) 

(e.g., catalyst monitor, comprehensive component input component 

rationality monitors), the OBD system shall erase the permanent 

fault code at the end of a driving cycle if the monitor has run and 

made one or more determinations during a driving cycle that the 

malfunction of the component or the system is not present and has 

not made any determinations within the same driving cycle that the 

malfunction is present.

b. If the monitor of the malfunction that caused the permanent fault 

code to be stored is not subject to the minimum ratio requirements 

of section (d)(3.2) (e.g., gasoline misfire monitor, gasoline fuel 

system monitor, comprehensive component circuit continuity 

monitors), the OBD system shall erase the permanent fault code at 

the end of a driving cycle if:

1. The monitor has run and made one or more determinations 

during a driving cycle that the malfunction of the component or 

the system is not present and has not made any determinations 

within the same driving cycle that the malfunction is present;

2. The monitor has not made any determinations that the 

malfunction is present subsequent to the most recent driving 

cycle in which the criteria of section (d)(2.3.1)(C)(ii)b.1. are met; 

and

3. The following criteria are satisfied on any single driving cycle 

(which may be a different driving cycle than that in which the 

criteria of section (d)( 2.3.1)(C)(ii)b.1. are satisfied):

i. Cumulative time since engine start is greater than or equal to 

600 seconds;

ii. Cumulative gasoline engine operation at or above 25 miles 

per hour or diesel engine operation at or above 1150 rpm, 

either of which occurs for greater than or equal to 300 

seconds; and
12

iii. Continuous vehicle operation at idle (i.e., accelerator pedal 

released by driver and either vehicle speed less than or 

equal to one mile per hour or engine speed less than or 

equal to 200 rpm above normal warmed-up idle (as 

determined in the drive position for vehicles equipped with 

an automatic transmission)) for greater than or equal to 30 

seconds;. and

iv. The monitor has not made any determinations that the 

malfunction is present. 

4. Monitors required to use “similar conditions” as defined in 

section (c) to store and erase pending and confirmed fault 

codes may not require that the similar conditions be met prior to 

erasure of the permanent fault code.

c. For monitors subject to section (d)(2.3.1)(C)(ii)a., the manufacturer 

may choose to erase the permanent fault code using the criteria 

under section (d)(2.3.1)(C)(ii)b. in lieu of the criteria under section 

(d)(2.3.1)(C)(ii)a.

d. For 2010 through 2012 model year engines, manufacturers may 

request Executive Officer approval to use alternate criteria to erase 

the permanent fault code. The Executive Officer shall approve 

alternate criteria that will not likely require driving conditions that 

are longer and more difficult to meet than those required under 

section (d)(2.3.1)(C)(ii)b.

(2.3.2) For vehicles using the SAE J1939 protocol for the standardized functions 

required in section (h): 

(A) Extinguishing the MIL. Except as otherwise provided in sections 

(e)(1.4.2)(F), (e)(2.4.2)(D) and (e)(6.4.2) for fuel system malfunctions, 

misfire malfunctions, and empty reductant tanks, once the MIL has been 

illuminated, it may be extinguished after three subsequent sequential 

driving cycles during which the monitoring system responsible for 

illuminating the MIL functions and the previously detected malfunction is 

no longer present provided no other malfunction has been detected that 

would independently illuminate the MIL according to the requirements 

outlined above. 

(B) Erasing a MIL-on fault code. The OBD system may erase a MIL-on fault 

code in conjunction with extinguishing the MIL as described under section 

(d)(2.3.2)(A). In addition to the erasure of the MIL-on fault code, the OBD 

system shall store a previously MIL-on fault code for that failure. 

(C) Erasing a previously MIL-on fault code. The OBD system may erase a 

previously MIL-on fault code if the identified malfunction has not been 

again detected in at least 40 engine warm-up cycles and the MIL is 

presently not illuminated for that malfunction. 

(D) Erasing a permanent fault code. The OBD system shall erase a 

permanent fault code only if either of the following conditions occur:

(i) If the OBD system is commanding the MIL on, the OBD system shall 

erase a permanent fault code only if Tthe OBD system itself 

determines that the malfunction that caused the MIL-onpermanent

fault code to be stored is no longer present and is not commanding the 
13

MIL on, concurrent withpursuant to the requirements of section 

(d)(2.3.2)(A) (which for the purposes of this section shall apply to all 

monitors). Erasure of the permanent fault code shall occur in 

conjunction with extinguishing the MIL or no later than the start of the 

first drive cycle that begins with the MIL commanded off., or

(ii) Subsequent to a clearing of theIf all fault information in the on-board 

computer has been cleared (i.e., through the use of a scan tool or 

battery disconnect) and the OBD system is not commanding the MIL 

on, the diagnostic for the malfunction that caused the permanent fault 

code to be stored has fully executed (i.e., has executed the minimum 

number of checks necessary for MIL illumination) and determined the 

malfunction is no longer present.:

a. Except as provided for in section (d)(2.3.2)(D)(ii)c., if the monitor of 

the malfunction that caused the permanent fault code to be stored 

is subject to the minimum ratio requirements of section (d)(3.2) 

(e.g., catalyst monitor, comprehensive component input component 

rationality monitors), the OBD system shall erase the permanent 

fault code at the end of a driving cycle if the monitor has run and 

made one or more determinations during a driving cycle that the 

malfunction of the component or the system is not present and has 

not made any determinations within the same driving cycle that the 

malfunction is present.

b. If the monitor of the malfunction that caused the permanent fault 

code to be stored is not subject to the minimum ratio requirements 

of section (d)(3.2) (e.g., continuous diesel fuel system monitors,

comprehensive component circuit continuity monitors), the OBD 

system shall erase the permanent fault code at the end of a driving 

cycle if:

1. The monitor has run and made one or more determinations 

during a driving cycle that the malfunction of the component or 

the system is not present and has not made any determinations 

within the same driving cycle that the malfunction is present;

2. The monitor has not made any determinations that the 

malfunction is present subsequent to the most recent driving 

cycle in which the criteria of section (d)(2.3.2)(D)(ii)b.1. are met; 

and

3. The following criteria are satisfied on any single driving cycle 

(which may be a different driving cycle than that in which the 

criteria of section (d)( 2.3.2)(D)(ii)b.1. are satisfied):

i. Cumulative time since engine start is greater than or equal to 

600 seconds;

ii. Cumulative gasoline engine operation at or above 25 miles 

per hour or diesel engine operation at or above 1150 rpm, 

either of which occurs for greater than or equal to 300 

seconds; and

iii. Continuous vehicle operation at idle (i.e., accelerator pedal 

released by driver and either vehicle speed less than or 

equal to one mile per hour or engine speed less than or 
14

equal to 200 rpm above normal warmed-up idle (as 

determined in the drive position for vehicles equipped with 

an automatic transmission)) for greater than or equal to 30 

seconds.

4. Monitors required to use “similar conditions” as defined in 

section (c) to store and erase pending and confirmed/MIL-on

fault codes may not require that the similar conditions be met 

prior to erasure of the permanent fault code.

c. For monitors subject to section (d)(2.3.2)(D)(ii)a., the manufacturer 

may choose to erase the permanent fault code using the criteria 

under section (d)(2.3.2)(D)(ii)b. in lieu of the criteria under section 

(d)(2.3.2)(D)(ii)a.

d. For 2010 through 2012 model year engines, manufacturers may 

request Executive Officer approval to use alternate criteria to erase 

the permanent fault code. The Executive Officer shall approve 

alternate criteria that will not likely require driving conditions that 

are longer and more difficult to meet than those required under 

section (d)(2.3.2)(D)(ii)b.

(2.4) Exceptions to MIL and Fault Code Requirements. 

(2.4.1) If the engine enters a default mode of operation, a manufacturer may 

request Executive Officer approval to be exempt from illuminating the MIL 

if any of the following conditions listed below occurs. The Executive 

Officer shall approve the request upon determining that the manufacturer 

has submitted data and/or engineering evaluation that verify the 

conditions below: 

(A) The default strategy (1) causes an overt indication (e.g., illumination of a

red engine shut-down warning light) such that the driver is certain to 

respond and have the problem corrected and (2) is not caused by or 

invoked to protect a component required to be monitored by the OBD 

system under sections (e) through (g); or

(B) The default strategy is an AECD that is properly activated due to the 

occurrence of conditions that have been approved by the Executive 

Officer. 

(2.4.2) For gasoline engines, a manufacturer may elect to meet the MIL and fault 

code requirements in title 13, CCR section 1968.2(d)(2) in lieu of meeting 

the requirements of (d)(2). 

(3) Monitoring Conditions. 

Section (d)(3) sets forth the general monitoring requirements while sections (e) 

through (g) sets forth the specific monitoring requirements as well as identifies 

which of the following general monitoring requirements in section (d)(3) are 

applicable for each monitored component or system identified in sections (e) 

through (g). 

(3.1) For all engines: 

(3.1.1) As specifically provided for in sections (e) through (g), manufacturers shall 

define monitoring conditions, subject to Executive Officer approval, for 

detecting malfunctions identified in sections (e) through (g). The 

Executive Officer shall approve manufacturer-defined monitoring 

conditions that are determined (based on manufacturer-submitted data 
15

and/or other engineering documentation) to be: technically necessary to 

ensure robust detection of malfunctions (e.g., avoid false passes and 

false indications of malfunctions); designed to ensure monitoring will occur 

under conditions that may reasonably be expected to be encountered in 

normal vehicle operation and use; and designed to ensure monitoring will 

occur during the FTP cycle. 

(3.1.2) Monitoring shall occur at least once per driving cycle in which the 

monitoring conditions are met. 

(3.1.3) Manufacturers may request Executive Officer approval to define 

monitoring conditions that are not encountered during the FTP cycle as 

required in section (d)(3.1.1). In evaluating the manufacturer's request, 

the Executive Officer shall consider the degree to which the requirement 

to run during the FTP cycle restricts in-use monitoring, the technical 

necessity for defining monitoring conditions that are not encountered 

during the FTP cycle, data and/or an engineering evaluation submitted by 

the manufacturer which demonstrate that the component/system does not 

normally function, or monitoring is otherwise not feasible, during the FTP 

cycle, and, where applicable in section (d)(3.2), the ability of the 

manufacturer to demonstrate the monitoring conditions will satisfy the 

minimum acceptable in-use monitor performance ratio requirement as 

defined in section (d)(3.2) (e.g., data which show in-use driving meets the 

minimum requirements). 

(3.2) As specifically provided for in sections (e) through (g), manufacturers shall 

define monitoring conditions in accordance with the criteria in sections 

(d)(3.2.1) through (3.2.3). 

(3.2.1) Manufacturers shall implement software algorithms in the OBD system to 

individually track and report in-use performance of the following monitors 

in the standardized format specified in section (d)(5): 

(A) NMHC converting catalyst (section (e)(5.3.1)) 

(B) NOx converting catalyst (section (e)(6.3.1)) 

(C) Catalyst (section (f)(6.3)); 

(D) Exhaust gas sensor (sections (e)(9.3.1)(A) or (f)(8.3.1)(A)); 

(E) Evaporative system (section (f)(7.3.2)); 

(F) EGR system (sections (e)(3.3.2) and (3.3.3) or (f)(3.3.1)) and VVT system 

(sections (e)(10.3) or (f)(9.3)); 

(G) Secondary air system (section (f)(5.3.1)); 

(H) PM filter (section (e)(8.3)); 

(I) Boost pressure control system (sections (e)(4.3.2) and (e)(4.3.3)); and

(J) NOx adsorber (section (e)(7.3.1)); 

(K) Fuel system (section (e)(1.3.3)); and

(L) Secondary oxygen sensor (section (f)(8.3.2)(A)). 

The OBD system is not required to track and report in-use performance 

for monitors other than those specifically identified above. 

(3.2.2) For all 2013 and subsequent model year engines, manufacturers shall 

define monitoring conditions that, in addition to meeting the criteria in 

sections (d)(3.1) and (d)(3.2.1), ensure that the monitor yields an in-use 

performance ratio (as defined in section (d)(4)) that meets or exceeds the 

minimum acceptable in-use monitor performance ratio for in-use vehicles. 
16

 For purposes of this regulation, the minimum acceptable in-use monitor 

performance ratio is 0.100 for all monitors specifically required in sections 

(e) through (g) to meet the monitoring condition requirements of section 

(d)(3.2). 

(3.2.3) Manufacturers may not use the calculated ratio (or any element thereof) or 

any other indication of monitor frequency as a monitoring condition for a 

monitor (e.g., using a low ratio to enable more frequent monitoring 

through diagnostic executive priority or modification of other monitoring 

conditions, or using a high ratio to enable less frequent monitoring). 

(3.2.4) Upon request of a manufacturer or upon the best engineering judgment of 

the ARB, the Executive Officer may revise the minimum acceptable in-use 

monitoring performance ratio specified in section (d)(3.2.2) for a specific 

monitor if the most reliable monitoring method developed requires a lower 

ratio. 

(4) In-Use Monitor Performance Ratio Definition. 

(4.1) For monitors required to meet the requirements in section (d)(3.2), the ratio 

shall be calculated in accordance with the following specifications for the 

numerator, denominator, and ratio. 

(4.2) Numerator Specifications 

(4.2.1) Definition: The numerator is defined as a measure of the number of times 

a vehicle has been operated such that all monitoring conditions necessary 

for a specific monitor to detect a malfunction have been encountered. 

(4.2.2) Specifications for incrementing: 

(A) Except as provided for in section (d)(4.2.2)(E), the numerator, when 

incremented, shall be incremented by an integer of one. The numerator 

may not be incremented more than once per driving cycle. 

(B) The numerator for a specific monitor shall be incremented within 10 

seconds if and only if the following criteria are satisfied on a single driving 

cycle: 

(i) Every monitoring condition necessary for the monitor of the specific 

component to detect a malfunction and store a pending fault code has 

been satisfied, including enable criteria, presence or absence of 

related fault codes, sufficient length of monitoring time, and diagnostic 

executive priority assignments (e.g., diagnostic “A” must execute prior 

to diagnostic “B”). For the purpose of incrementing the numerator, 

satisfying all the monitoring conditions necessary for a monitor to 

determine the component is passing may not, by itself, be sufficient to 

meet this criteria. 

(ii) For monitors that require multiple stages or events in a single driving 

cycle to detect a malfunction, every monitoring condition necessary for 

all events to have completed must be satisfied. 

(iii) For monitors that require intrusive operation of components to detect a 

malfunction, a manufacturer shall request Executive Officer approval 

of the strategy used to determine that, had a malfunction been 

present, the monitor would have detected the malfunction. Executive 

Officer approval of the request shall be based on the equivalence of 

the strategy to actual intrusive operation and the ability of the strategy 

to accurately determine if every monitoring condition necessary for the 
17

intrusive event to occur was satisfied. 

(iv) For the secondary air system monitor, the criteria in sections 

(d)(4.2.2)(B)(i) through (iii) above are satisfied during normal operation 

of the secondary air system. Monitoring during intrusive operation of 

the secondary air system later in the same driving cycle solely for the 

purpose of monitoring may not, by itself, be sufficient to meet this 

criteria. 

(C) For monitors that can generate results in a “gray zone” or “non-detection 

zone” (i.e., results that indicate neither a passing system nor a 

malfunctioning system) or in a “non-decision zone” (e.g., monitors that 

increment and decrement counters until a pass or fail threshold is 

reached), the manufacturer shall submit a plan for appropriate 

incrementing of the numerator to the Executive Officer for review and 

approval. In general, the Executive Officer shall not approve plans that 

allow the numerator to be incremented when the monitor indicates a result 

in the “non-detection zone” or prior to the monitor reaching a decision. In 

reviewing the plan for approval, the Executive Officer shall consider data 

and/or engineering evaluation submitted by the manufacturer 

demonstrating the expected frequency of results in the “non-detection 

zone” and the ability of the monitor to accurately determine if a monitor 

would have detected a malfunction instead of a result in the “nondetection zone” had an actual malfunction been present. 

(D) For monitors that run or complete during engine-off operation, the 

numerator shall be incremented within 10 seconds after the monitor has 

completed during engine-off operation or during the first 10 seconds of 

engine start on the subsequent driving cycle. 

(E) Except as specified in section (d)(4.2.2)(F) for exponentially weighted 

moving averages, Mmanufacturers utilizing alternate statistical MIL 

illumination protocols as allowed in sections (d)(2.2.1)(C) and (d)(2.2.2)(C) 

for any of the monitors requiring a numerator shall submit a plan for 

appropriate incrementing of the numerator to the Executive Officer for 

review and approval. Executive Officer approval of the plan shall be 

conditioned upon the manufacturer providing supporting data and/or 

engineering evaluation demonstrating the equivalence of the incrementing 

in the manufacturer's plan to the incrementing specified in section 

(d)(4.2.2) for monitors using the standard MIL illumination protocol and the 

overall equivalence of the manufacturer's plan in determining that the 

minimum acceptable in-use performance ratio in section (d)(3.2) is 

satisfied. 

(F) Manufacturers using an exponentially weighted moving average (EWMA) 

as the alternate statistical MIL illumination protocol approved in 

accordance with sections (d)(2.2.1)(C) and (d)(2.2.2)(C) shall increment 

the numerator as follows:

(i) Following a reset or erasure of the EWMA result, the numerator may 

not be incremented until after the requisite number of decisions 

necessary for MIL illumination have been fully executed.

(ii) After the number of decisions required in section (d)(4.2.2)(F)(i) above, 

the numerator, when incremented, shall be incremented by an integer 
18

of one and may not be incremented more than once per driving cycle. 

Incrementing of the numerator shall also be in accordance with 

sections (d)(4.2.2)(B), (C), and (D).

(4.3) Denominator Specifications 

(4.3.1) Definition: The denominator is defined as a measure of the number of 

times a vehicle has been operated as defined in (d)(4.3.2). 

(4.3.2) Specifications for incrementing: 

(A) The denominator, when incremented, shall be incremented by an integer 

of one. The denominator may not be incremented more than once per 

driving cycle. 

(B) The denominator for each monitor shall be incremented within 10 

seconds if and only if the following criteria are satisfied on a single driving 

cycle: 

(i) Cumulative time since start of driving cycle is greater than or equal to 

600 seconds while at an elevation of less than 8,000 feet above sea 

level and at an ambient temperature of greater than or equal to 20 

degrees Fahrenheit; 

(ii) Cumulative gasoline engine operation at or above 25 miles per hour or 

diesel engine operation at or above 15% calculated load1150 rpm, 

either of which occurs for greater than or equal to 300 seconds while 

at an elevation of less than 8,000 feet above sea level and at an 

ambient temperature of greater than or equal to 20 degrees 

Fahrenheit; and 

(iii) Continuous vehicle operation at idle (i.e.g., accelerator pedal released 

by driver and either vehicle speed less than or equal to one mile per 

hour or engine speed less than or equal to 200 rpm above normal 

warmed-up idle (as determined in the drive position for vehicles 

equipped with an automatic transmission)) for greater than or equal to 

30 seconds while at an elevation of less than 8,000 feet above sea 

level and at an ambient temperature of greater than or equal to 20 

degrees Fahrenheit. 

(iv) For 2010 through 2012 model year diesel engines, manufacturers may 

use diesel engine operation at or above 15% calculated load in lieu of 

1150 rpm for the criterion in section (d)(4.3.2)(B)(ii) above.

(C) In addition to the requirements of section (d)(4.3.2)(B) above, the 

evaporative system monitor denominator(s) shall be incremented if and 

only if: 

(i) Cumulative time since start of driving cycle is greater than or equal to 

600 seconds while at an ambient temperature of greater than or equal 

to 40 degrees Fahrenheit but less than or equal to 95 degrees 

Fahrenheit; and 

(ii) Engine cold start occurs with engine coolant temperature at engine 

start greater than or equal to 40 degrees Fahrenheit but less than or 

equal to 95 degrees Fahrenheit and less than or equal to 12 degrees 

Fahrenheit higher than ambient temperature at engine start. 

(D) In addition to the requirements of section (d)(4.3.2)(B) above, the 

denominator(s) for the following monitors shall be incremented if and only 

if the component or strategy is commanded “on” for a cumulative time 
19

greater than or equal to 10 seconds: 

(i) Secondary Air System (section (f)(5)) 

(ii) Cold Start Emission Reduction Strategy (sections (e)(11) or (f)(4)) 

(iii) Components or systems that operate only at engine start-up (e.g., 

glow plugs, intake air heaters) and are subject to monitoring under 

“other emission control systems” (section (g)(4)) or comprehensive 

component output components (section (g)(3)) 

For purposes of determining this commanded “on” time, the OBD system 

may not include time during intrusive operation of any of the components 

or strategies later in the same driving cycle solely for the purposes of 

monitoring. 

(E) In addition to the requirements of section (d)(4.3.2)(B) above, the 

denominator(s) for the following monitors of output components (except 

those operated only at engine start-up and subject to the requirements of 

the previous section (d)(4.3.2)(D)) shall be incremented if and only if the 

component is commanded to function (e.g., commanded “on”, “open”, 

“closed”, “locked”) on two or more occasions for greater than two seconds 

during the driving cycle or for a cumulative time greater than or equal to 

10 seconds, whichever occurs first: 

(i) Variable valve timing and/or control system (sections (e)(10) or (f)(9)) 

(ii) “Other emission control systems” (section (g)(4)) 

(iii) Comprehensive component output component (section (g)(3)) (e.g., 

turbocharger waste-gates, variable length manifold runners) 

(F) For monitors of the following components, the manufacturer may request 

Executive Officer approval to use alternate or additional criteria to that set 

forth in section (d)(4.3.2)(B) above for incrementing the denominator. 

Executive Officer approval of the proposed criteria shall be based on the 

equivalence of the proposed criteria in measuring the frequency of 

monitor operation relative to the amount of vehicle operation in 

accordance with the criteria in section (d)(4.3.2)(B) above: 

(i) Engine cooling system input components (section (g)(1)) 

(ii) “Other emission control systems” (section (g)(4)) 

(iii) Comprehensive component input components that require extended 

monitoring evaluation (section (g)(3)) (e.g., stuck fuel level sensor 

rationality) 

(iv) Comprehensive component input component temperature sensor

rationality monitors (section (g)(3)) (e.g., intake air temperature sensor, 

ambient temperature sensor, fuel temperature sensor)

(v) PM filter frequent regeneration (section (e)(8.2.2))

(G) For monitors of the following components or other emission controls that 

experience infrequent regeneration events, the manufacturer may request 

Executive Officer approval to use alternate or additional criteria to that set 

forth in section (d)(4.3.2)(B) above for incrementing the denominator. 

Executive Officer approval of the proposed criteria shall be based on the 

effectiveness of the proposed criteria in measuring the frequency of 

monitor operation relative to the amount of vehicle operationthe 

denominator(s) shall be incremented by one if and only if, in addition to 

meeting the requirements of section (d)(4.3.2)(B) on the current driving 
20

cycle, at least 750 minutes of cumulative engine run time have occurred 

since the last time the denominator was incremented. The 750-minute 

engine run time counter shall be reset to zero and begin counting again 

after the denominator has been incremented and no later than the start of 

the next ignition cycle: 

(i) Oxidation Diesel NMHC converting catalyst (section (e)(5)) 

(ii) Particulate matter filters (sections (e)(8.2.1), (8.2.4), and (8.2.5)) 

(H) In addition to the requirements of section (d)(4.3.2)(B) above, the 

denominator(s) for the following monitors shall be incremented if and only 

if a regeneration event is commanded for a time greater than or equal to 

10 seconds:

(i) PM filter incomplete regeneration (section (e)(8.2.3))

(ii) PM filter active/intrusive injection (section (e)(8.2.6))

(H)(I) For hybrid vehicles, vehicles that employ alternate engine start 

hardware or strategies (e.g., integrated starter and generators), or 

alternate fuel vehicles (e.g., dedicated, bi-fuel, or dual-fuel applications), 

the manufacturer may request Executive Officer approval to use alternate 

criteria to that set forth in section (d)(4.3.2)(B) above for incrementing the 

denominator. In general, the Executive Officer shall not approve alternate 

criteria for vehicles that only employ engine shut off at or near idle/vehicle 

stop conditions. Executive Officer approval of the alternate criteria shall 

be based on the equivalence of the alternate criteria to determine the 

amount of vehicle operation relative to the measure of conventional 

vehicle operation in accordance with the criteria in section (d)(4.3.2)(B) 

above. 

(4.4) Ratio Specifications 

(4.4.1) Definition: The ratio is defined as the numerator divided by the 

denominator. 

(4.5) Disablement of Numerators and Denominators 

(4.5.1) Within 10 seconds of a malfunction being detected (i.e., a pending, 

confirmed, or MIL-on fault code being stored) that disables a monitor 

required to meet the monitoring conditions in section (d)(3.2), the OBD 

system shall disable further incrementing of the corresponding numerator 

and denominator for each monitor that is disabled. When the malfunction 

is no longer detected (e.g., the pending code is erased through selfclearing or through a scan tool command), incrementing of all 

corresponding numerators and denominators shall resume within 10 

seconds. 

(4.5.2) Within 10 seconds of the start of a PTO (see section (c)) operation that 

disables a monitor required to meet the monitoring conditions in section 

(d)(3.2), the OBD system shall disable further incrementing of the 

corresponding numerator and denominator for each monitor that is 

disabled. When the PTO operation ends, incrementing of all 

corresponding numerators and denominators shall resume within 10 

seconds. 

(4.5.3) The OBD system shall disable further incrementing of all numerators and 

denominators within 10 seconds if a malfunction of any component used 

to determine if the criteria in sections (d)(4.3.2)(B) through (C) are 
21

satisfied (i.e., vehicle speed/calculated load, ambient temperature, 

elevation, idle operation, engine cold start, or time of operation) has been 

detected (i.e., a pending, confirmed, or MIL-on fault code has been 

stored)and the corresponding pending fault code has been stored. 

Incrementing of all numerators and denominators shall resume within 10 

seconds when the malfunction is no longer present (e.g., pending code 

erased through self-clearing or by a scan tool command). 

(5) Standardized tracking and reporting of monitor performance. 

(5.1) For monitors required to track and report in-use monitor performance in 

section (d)(3.2), the performance data shall be tracked and reported in 

accordance with the specifications in sections (d)(4), (d)(5), and (h)(5.1). The 

OBD system shall separately report an in-use monitor performance 

numerator and denominator for each of the following components: 

(5.1.1) For diesel engines, fuel system, NMHC catalyst bank 1, NMHC catalyst 

bank 2, NOx catalyst bank 1, NOx catalyst bank 2, exhaust gas sensor 

bank 1, exhaust gas sensor bank 2, EGR/VVT system, PM filter, boost 

pressure control system, and NOx adsorber. The OBD system shall also 

report a general denominator and an ignition cycle counter in the 

standardized format specified in sections (d)(5.5), (d)(5.6), and (h)(5.1). 

(5.1.2) For gasoline engines, catalyst bank 1, catalyst bank 2, primary oxygen 

sensor bank 1, primary oxygen sensor bank 2, secondary oxygen sensor 

evaporative leak detection system, EGR/VVT system, and secondary air 

system. The OBD system shall also report a general denominator and an 

ignition cycle counter in the standardized format specified in sections 

(d)(5.5), (d)(5.6), and (h)(5.1). 

(5.2) Numerator 

(5.2.1) The OBD system shall report a separate numerator for each of the 

components listed in section (d)(5.1). 

(5.2.2) For specific components or systems that have multiple monitors that are 

required to be reported under section (e) (e.g., exhaust gas sensor bank 1 

may have multiple monitors for sensor response or other sensor 

characteristics), the OBD system shall separately track numerators and 

denominators for each of the specific monitors and report only the 

corresponding numerator and denominator for the specific monitor that 

has the lowest numerical ratio. If two or more specific monitors have 

identical ratios, the corresponding numerator and denominator for the 

specific monitor that has the highest denominator shall be reported for the 

specific component. 

(5.2.3) The numerator(s) shall be reported in accordance with the specifications 

in section (h)(5.1.2)(A). 

(5.3) Denominator 

(5.3.1) The OBD system shall report a separate denominator for each of the 

components listed in section (d)(5.1). 

(5.3.2) The denominator(s) shall be reported in accordance with the 

specifications in section (h)(5.1.2)(A). 

(5.4) Ratio 

(5.4.1) For purposes of determining which corresponding numerator and 

denominator to report as required in section (d)(5.2.2), the ratio shall be 
22

calculated in accordance with the specifications in section (h)(5.1.2)(B). 

(5.5) Ignition cycle counter 

(5.5.1) Definition: 

(A) The ignition cycle counter is defined as a counter that indicates the 

number of ignition cycles a vehicle has experienced as defined in section 

(d)(5.5.2)(B). 

(B) The ignition cycle counter shall be reported in accordance with the 

specifications in section (h)(5.1.2)(A). 

(5.5.2) Specifications for incrementing: 

(A) The ignition cycle counter, when incremented, shall be incremented by an 

integer of one. The ignition cycle counter may not be incremented more 

than once per ignition cycle. 

(B) The ignition cycle counter shall be incremented within 10 seconds if and 

only if the engine exceeds an engine speed of 50 to 150 rpm below the 

normal, warmed-up idle speed (as determined in the drive position for 

vehicles equipped with an automatic transmission) for at least two 

seconds plus or minus one second. 

(C) The OBD system shall disable further incrementing of the ignition cycle 

counter within 10 seconds if a malfunction of any component used to 

determine if the criteria in section (d)(5.5.2)(B) are satisfied (i.e., engine 

speed or time of operation) has been detected and the corresponding 

pending fault code has been stored. The ignition cycle counter may not 

be disabled from incrementing for any other condition. Incrementing of 

the ignition cycle counter shall resume within 10 seconds when the 

malfunction is no longer present (e.g., pending code erased through selfclearing or by a scan tool command). 

(5.6) General Denominator 

(5.6.1) Definition: 

(A) The general denominator is defined as a measure of the number of times 

a vehicle has been operated as defined in section (d)(5.6.2)(B). 

(B) The general denominator shall be reported in accordance with the 

specifications in section (h)(5.1.2)(A). 

(5.6.2) Specifications for incrementing: 

(A) The general denominator, when incremented, shall be incremented by an 

integer of one. The general denominator may not be incremented more 

than once per driving cycle. 

(B) The general denominator shall be incremented within 10 seconds if and 

only if the criteria identified in section (d)(4.3.2)(B) are satisfied on a single 

driving cycle. 

(C) The OBD system shall disable further incrementing of the general 

denominator within 10 seconds if a malfunction of any component used to 

determine if the criteria in section (d)(4.3.2)(B) are satisfied (i.e., vehicle 

speed/load, ambient temperature, elevation, idle operation, or time of 

operation) has been detected and the corresponding pending fault code 

has been stored. The general denominator may not be disabled from 

incrementing for any other condition (e.g., the disablement criteria in 

sections (d)(4.5.1) and (d)(4.5.2) may not disable the general 

denominator). Incrementing of the general denominator shall resume 
23

within 10 seconds when the malfunction is no longer present (e.g., 

pending code erased through self-clearing or by a scan tool command). 

(6) Malfunction Criteria Determination. 

(6.1) In determining the malfunction criteria for diesel engine monitors in sections 

(e) and (g) that are required to indicate a malfunction before emissions 

exceed an emission threshold based on any applicable standard (e.g., 2.0 

times any of the applicable standards), the manufacturer shall: 

(6.1.1) Use the emission test cycle and standard (i.e., FTP or SET) determined 

by the manufacturer, through use of data and/or engineering analysis, to 

be more stringent (i.e., to result in higher emissions with the same level of 

monitored component malfunction) as the “applicable standard”. The 

manufacturer shall use data and/or engineering analysis to determine the 

test cycle and standard that is more stringent. 

(6.1.2) Identify in the certification documentation required under section (j), the 

test cycle and standard determined by the manufacturer to be the 

mostmore stringent for each applicable monitor. 

(6.1.3) If the Executive Officer reasonably believes that a manufacturer has 

incorrectly determined the test cycle and standard that is most more

stringent, the Executive Officer shall require the manufacturer to provide 

emission data and/or engineering analysis showing that the other test 

cycle and standard are less stringent. 

(6.2) On engines equipped with emission controls that experience infrequent 

regeneration events, a manufacturer shall adjust the emission test results that 

are used to determine the malfunction criterion for monitors that are required 

to indicate a malfunction before emissions exceed a certain emission 

threshold (e.g., 2.0 times any of the applicable standards). Except as 

provided in section (d)(6.2.3), Ffor each monitor, the manufacturer shall 

adjust the emission result using the procedure described in CFR title 40, part 

86.004-28(i) with the component for which the malfunction criteria is being 

established deteriorated to the malfunction threshold. The adjusted emission 

value shall be used for purposes of determining whether or not the specified 

emission threshold is exceeded (e.g., a malfunction must be detected before 

the adjusted emission value exceeds 2.0 times any applicable standard). 

(6.2.1) For purposes of section (d)(6.2), “regeneration” means an event during 

which emissions levels change while the emission control performance is 

being restored by design.

(6.2.2) For purposes of section (d)(6.2), “infrequent” means having an expected 

frequency of less than once per FTP cycle.

(6.2.3) In lieu of using the procedure described in CFR title 40, part 86.004-28(i), 

the manufacturer may submit an alternate plan to calculate the 

adjustment factors for determining the adjusted emission values to the 

Executive Officer for review and approval. Executive Officer approval of 

the plan shall be conditioned upon the manufacturer providing data and/or 

engineering evaluation demonstrating the procedure is consistent with

good engineering judgment in determining appropriate modifications to 

the tailpipe certification adjustment factors.

(6.3) In lieu of meeting the malfunction criteria for gasoline engine monitors in 

sections (f) and (g), the manufacturer may request Executive Officer approval 
24

to utilize OBD systems certified to the requirements of title 13, CCR section 

1968.2 on medium-duty engines or vehicles. The Executive Officer shall 

approve the request upon finding that the manufacturer has used good 

engineering judgment in determining equivalent malfunction detection criteria 

on the heavy-duty engine.

(7) Implementation Schedule 

(7.1) Except as specified in sections (d)(7.4) and (d)(7.5) for small volume 

manufacturers and alternate-fueled engines, for the 2010 through 2012 

model year engines:

(7.1.1) Full OBD. Except as specified in section (d)(7.1.3) below, a manufacturer 

shall implement an OBD system meeting the requirements of section 

1971.1 on one engine rating (i.e., the OBD parent rating) within one of the 

manufacturer’s engine families. The OBD parent rating shall be from the 

manufacturer’s heavy-duty engine family with the highest weighted sales 

number for the 2010 model year and shall be the engine rating with the 

highest weighted sales number within that engine family.

(7.1.2) Extrapolated OBD. For all other engine ratings within the engine family 

selected according to section (d)(7.1.1) (i.e., the OBD child ratings), 

except as specified in section (d)(7.1.3) below), a manufacturer shall 

implement an OBD system meeting the requirements of section 1971.1 

with the exception that the OBD system is not required to detect a 

malfunction prior to exceeding the emission thresholds specified in the 

malfunction criteria in sections (e) through (g). In lieu of detecting a 

malfunction prior to exceeding the emission thresholds, a manufacturer 

shall submit a plan for Executive Officer review and approval detailing the 

engineering evaluation the manufacturer will use to establish the 

malfunction criteria for the OBD child ratings. The Executive Officer shall 

approve the plan upon determining that the manufacturer is using good 

engineering judgment to establish the malfunction criteria for robust 

detection of malfunctions, including consideration of differences of base 

engine, calibration, emission control components, and emission control 

strategies. 

(7.1.3) For all engine ratings (i.e., OBD parent and OBD child ratings) within the 

engine family selected according to (d)(7.1.1): 

(A) The OBD system is exempt from having to comply with the 

standardization requirements set forth in the incorporated documents to 

this regulation (e.g., SAE J1939 defined format) within the following 

sections: 

(i) (d)(1.2) and (h)(2) (standardized connector) 

(ii) (d)(2.1.1) and (2.1.5) (dedicated standardized MIL) 

(iii) (h)(3) (communication protocol) 

(iv) (h)(4) (standardized communication functions with respect to the 

requirements to make the data available in a standardized format or in 

accordance with SAE J1979/1939 specifications) 

(v) (h)(5.1.1) and (h)(5.2.1) with respect to the requirements to make the 

data available in a standardized format or in accordance with SAE 

J1979/1939 specifications. 

(B) The OBD system shall meet the requirements of either sections (d)(2.2.1) 
25

and (2.3.1) or (d)(2.2.2) and (2.3.2) regardless of the communication 

protocol (e.g., standardized, proprietary) used by the OBD system. 

(7.1.4) Engine Manufacturer Diagnostic (EMD) Systems. For all engine ratings in 

the manufacturer’s engine families not selected according to section 

(d)(7.1.1), a manufacturer shall: 

(A) Implement an EMD system meeting the requirements of title 13, CCR 

section 1971 in lieu of meeting the requirements of section 1971.1; and 

(B) Monitor the NOx aftertreatment (i.e., catalyst, adsorber) on engines soequipped. A malfunction shall be detected if:

(i) The NOx aftertreatment system has no detectable amount of NOx 

aftertreatment capability (i.e., NOx catalyst conversion or NOx 

adsorption); 

(ii) The NOx aftertreatment substrate is completely destroyed, removed, 

or missing; or 

(iii) The NOx aftertreatment assembly is replaced with a straight pipe.

(7.2) Except as specified in section (d)(7.5) for alternate-fueled engines, for the 

2013 through 2015 model year engines:

(7.2.1) A manufacturer shall be required to define one or more OBD groups to 

cover all engine ratings in all engine families.

(7.2.2) Full OBD. A manufacturer shall implement an OBD system meeting the 

requirements of section 1971.1:

(A) On all engine ratings (i.e., OBD parent and OBD child ratings) within the 

engine family selected according to section (d)(7.1.1); and 

(B) On one engine rating (i.e., OBD parent rating) within each of the 

manufacturer’s OBD groups. The OBD parent rating shall be the engine 

rating with the highest weighted sales number for the 2013 model year 

within each OBD group.

(7.2.3) Extrapolated OBD. For all engine ratings not subject to section (d)(7.2.2) 

(i.e., OBD child ratings), a manufacturer shall implement an OBD system 

meeting the requirements of section 1971.1 with the exception that the 

OBD system is not required to detect a malfunction prior to exceeding the 

emission thresholds specified in the malfunction criteria in sections (e) 

through (g). In lieu of detecting a malfunction prior to exceeding the 

emission thresholds, a manufacturer shall submit a plan for Executive 

Officer review and approval detailing the engineering evaluation the 

manufacturer will use to establish the malfunction criteria for the OBD 

child ratings. The Executive Officer shall approve the plan upon 

determining that the manufacturer is using good engineering judgment to 

establish the malfunction criteria for robust detection of malfunctions, 

including consideration of differences of base engine, calibration, 

emission control components, and emission control strategies.

(7.3) Except as specified in section (d)(7.5) for alternate-fueled engines, for the 

2016 and subsequent model year engines:

(7.3.1) A manufacturer shall implement an OBD system meeting the 

requirements of section 1971.1 on all engine ratings in all engine families.

(7.4) Small volume manufacturers shall be exempt from the requirements of 

section 1971.1 for 2010 through 2012 model year engines. For purposes of 

this requirement, a small volume manufacturer is defined as a manufacturer 
26

with projected engine sales for California heavy-duty vehicles of less than 

1200 engines per year for the 2010 model year. 

(7.5) For alternate-fueled engines:

(7.5.1) For 2010 through 2012 model year engines, a manufacturer shall be 

exempt from the requirements of section 1971.1.

(7.5.2) For 2013 through 2019 model year engines, the manufacturer shall:

(A) Implement an EMD system meeting the requirements of title 13, CCR 

section 1971 in lieu of meeting the requirements of section 1971.1; and 

(B) Monitor the NOx aftertreatment (i.e., catalyst, adsorber) on engines soequipped. A malfunction shall be detected if:

(i) The NOx aftertreatment system has no detectable amount of NOx 

aftertreatment capability (i.e., NOx catalyst conversion or NOx 

adsorption); 

(ii) The NOx aftertreatment substrate is completely destroyed, removed, 

or missing; or 

(iii) The NOx aftertreatment assembly is replaced with a straight pipe.

(7.5.3) For 2020 and subsequent model year engines, a manufacturer shall 

implement an OBD system meeting the requirements of section 1971.1. 

(e) MONITORING REQUIREMENTS FOR DIESEL/COMPRESSION-IGNITION 

ENGINES 

(1) FUEL SYSTEM MONITORING 

(1.1) Requirement: 

The OBD system shall monitor the fuel delivery system to determine its ability 

to comply with emission standards. The individual electronic components 

(e.g., actuators, valves, sensors, pumps) that are used in the fuel system and 

not specifically addressed in this section shall be monitored in accordance 

with the comprehensive component requirements in section (g)(3). 

(1.2) Malfunction Criteria: 

(1.2.1) Fuel system pressure control: The OBD system shall detect a malfunction 

of the fuel system pressure control system (e.g., fuel, hydraulic fluid) when 

the fuel system pressure control system is unable to maintain an engine’s 

NMHC, NOx, or CO emissions at or below 2.0 times the applicable 

standards or the engine’s PM emissions at or below the applicable 

standard plus 0.02 grams per brake horsepower-hour (g/bhp-hr). For 

engines in which no failure or deterioration of the fuel system pressure 

control could result in an engine’s emissions exceeding these emission 

levels, the OBD system shall detect a malfunction when the system has 

reached its control limits such that the commanded fuel system pressure 

cannot be delivered. 

(1.2.2) Injection quantity: The OBD system shall detect a malfunction of the fuel 

injection system when the system is unable to deliver the commanded 

quantity of fuel necessary to maintain an engine’s NMHC, CO, and NOx 

emissions at or below 2.0 times the applicable standards or the engine’s 

PM emissions at or below the applicable standard plus 0.02 g/bhp-hr. For 

engines in which no failure or deterioration of the fuel injection quantity 

could result in an engine’s emissions exceeding these emission levels, the 
27

OBD system shall detect a malfunction when the system has reached its 

control limits such that the commanded fuel quantity cannot be delivered. 

(1.2.3) Injection Timing: The OBD system shall detect a malfunction of the fuel 

injection system when the system is unable to deliver fuel at the proper 

crank angle/timing (e.g., injection timing too advanced or too retarded) 

necessary to maintain an engine’s NMHC, CO, and NOx emissions at or 

below 2.0 times the applicable standards or the engine’s PM emissions at 

or below the applicable standard plus 0.02 g/bhp-hr. For engines in which 

no failure or deterioration of the fuel injection timing could result in an 

engine’s emissions exceeding these emission levels, the OBD system 

shall detect a malfunction when the system has reached its control limits 

such that the commanded fuel injection timing cannot be achieved. 

(1.2.4) Feedback control: Except as provided for in section (e)(1.2.5), if the 

engine is equipped with feedback or feed-forward control of the fuel 

system (e.g., feedback control of pressure or pilot injection quantity), the 

OBD system shall detect a malfunction: 

(A) If the system fails to begin feedback control within a manufacturer 

specified time interval; 

(B) If a failure or deterioration causes open loop or default operation; or 

(C) If feedback the control system has used up all of the adjustment allowed 

by the manufacturer or reached its maximum authority and cannot 

achieve the target. 

(1.2.5) A manufacturer may request Executive Officer approval to temporarily 

disable monitoring for the malfunction criteria specified in section 

(e)(1.2.4)(C) during conditions that a manufacturer cannot robustly 

distinguish between a malfunctioning system and a properly operating 

system. The Executive Officer shall approve the disablement upon the 

manufacturer submitting data and/or analysis demonstrating that the 

control system, when operating as designed on an engine with all 

emission controls working properly, routinely operates during these 

conditions with all of the adjustment allowed by the manufacturer used up. 

(1.2.6) In lieu of detecting the malfunctions specified in sections (e)(1.2.4)(A) and 

(B) with a fuel system-specific monitor, the OBD system may monitor the 

individual parameters or components that are used as inputs for fuel 

system feedback control provided that the monitors detect all malfunctions 

that meet the criteria in sections (e)(1.2.4)(A) and (B).

(1.2.7) For purposes of determining the fuel system malfunction criteria in 

sections (e)(1.2.1) through (1.2.3):

(A) For 2010 through 2012 model year engines, the malfunction criteria shall 

be established by using a fault that affects either a single injector or all 

injectors equally. 

(B) For 2013 and subsequent model year engines, for section (e)(1.2.1), the 

malfunction criteria shall be established by using a fault that affects all 

injectors equally. Additionally, for systems that have single component 

failures which could affect a single injector (e.g., systems that build 

injection pressure within the injector that could have a single component 

pressure fault caused by the injector itself), the malfunction criteria shall 

also be established by using a fault that affects a single injector.
28

(C) For 2013 and subsequent model year engines, for sections (e)(1.2.2) 

through (1.2.3), the malfunction criteria shall be established by both (1) a 

fault that affects all the injectors equally and (2) a fault that affects only 

one injector.

(1.3) Monitoring Conditions: 

(1.3.1) Except as provided in sections (e)(1.3.2) and (e)(1.3.4), Tthe OBD system 

shall monitor continuously for malfunctions identified in sections (e)(1.2.1) 

and (e)(1.2.4) (i.e., fuel pressure control and feedback operation). 

(1.3.2) For fuel systems that achieve injection fuel pressure within the injector or 

increase pressure within the injector (e.g. in the injector of an amplified 

common rail system), manufacturers may request Executive Officer 

approval to define the monitoring conditions for malfunctions identified in 

sections (e)(1.2.1) in accordance with sections (d)(3.1) and (d)(3.2) (i.e., 

minimum ratio requirements). The Executive Officer shall approve the 

monitoring conditions upon the manufacturer submitting data and/or 

analysis identifying all possible failure modes and the effect each has 

(e.g., failure modes and effects analysis) on fuel pressure across the 

entire range of engine operating conditions, and upon the Executive 

Officer determining based on the data and/or analysis that the monitoring 

conditions allow for robust detection of all causes of fuel pressure 

malfunctions.

(1.3.2)(1.3.3) Manufacturers shall define the monitoring conditions for 

malfunctions identified in sections (e)(1.2.2) and (e)(1.2.3) (i.e., injection 

quantity and timing) in accordance with sections (d)(3.1) and (d)(3.2) (i.e., 

minimum ratio requirements). For all 2013 and subsequent model year 

engines, for purposes of tracking and reporting as required in section 

(d)(3.2.1), all monitors used to detect malfunctions identified in sections

(e)(1.2.2) and (e)(1.2.3) shall be tracked separately but reported as a 

single set of values as specified in section (d)(5.2.2).

(1.3.4) Manufacturers may request Executive Officer approval to temporarily 

disable continuous monitoring under conditions technically necessary to 

ensure robust detection of malfunctions and to avoid false passes and 

false indications of malfunctions. The Executive Officer shall approve the 

request upon determining that the manufacturer has submitted data 

and/or an engineering evaluation which demonstrate that a properly 

operating system cannot be distinguished from a malfunctioning system 

and that the disablement interval is limited only to that which is technically 

necessary.

(1.4) MIL Illumination and Fault Code Storage: 

(1.4.1) General requirements for MIL illumination and fault code storage are set 

forth in section (d)(2).

(1.4.2) Additionally, for malfunctions identified in section (e)(1.2.1) (i.e., fuel 

pressure control) on all 2013 and subsequent model year vehicles:

(A) A pending fault code shall be stored immediately upon the fuel system 

exceeding the malfunction criteria established pursuant to section 

(e)(1.2.1).

(B) Except as provided below, if a pending fault code is stored, the OBD

system shall immediately illuminate the MIL and store a confirmed/MIL-on
29

fault code if a malfunction is again detected during either of the following 

two events: (a) the driving cycle immediately following the storage of the 

pending fault code, regardless of the conditions encountered during the 

driving cycle; or (b) on the next driving cycle in which similar conditions 

(see section (c)) to those that occurred when the pending fault code was 

stored are encountered.

(C) The pending fault code may be erased at the end of the next driving cycle 

in which similar conditions have been encountered without an exceedance 

of the specified fuel system malfunction criteria. The pending code may 

also be erased if similar conditions are not encountered during the 80 

driving cycles immediately after the initial detection of a malfunction for 

which the pending code was set.

(D) Storage of freeze frame conditions.

(i) A manufacturer shall store and erase freeze frame conditions either in 

conjunction with storing and erasing a pending fault code or in 

conjunction with storing and erasing a confirmed/MIL-on fault code.

(ii) If freeze frame conditions are stored for a malfunction other than 

misfire (see section (e)(2)) or fuel system malfunction when a fault 

code is stored as specified in section (e)(1.4.2) above, the stored 

freeze frame information shall be replaced with freeze frame 

information regarding the fuel system malfunction.

(E) Storage of fuel system conditions for determining similar conditions of 

operation. 

(i) Upon detection of a fuel system malfunction under section (e)(1.4.2), 

the OBD system shall store the engine speed, load, and warm-up 

status of the first fuel system malfunction that resulted in the storage of 

the pending fault code.

(ii) The manufacturer may request Executive Officer approval to use an 

alternate definition of similar conditions in lieu of the definition 

specified in section (c). The Executive Officer shall approve the 

alternate definition upon the manufacturer providing data or analysis 

demonstrating that the alternate definition provides for equivalent 

robustness in detection of fuel system faults that vary in severity 

depending on engine speed, load, and/or warm-up status.

(F) Extinguishing the MIL. The MIL may be extinguished after three 

sequential driving cycles in which similar conditions have been 

encountered without a malfunction of the fuel system.

(2) MISFIRE MONITORING 

(2.1) Requirement: 

(2.1.1) The OBD system shall monitor the engine for misfire causing excess 

emissions. The OBD system shall be capable of detecting misfire 

occurring in one or more cylinders. To the extent possible without adding 

hardware for this specific purpose, the OBD system shall also identify the 

specific misfiring cylinder. 

(2.1.2) If more than one cylinder is continuously misfiring, a separate fault code 

shall be stored indicating that multiple cylinders are misfiring. When 

identifying multiple cylinder misfire, the manufacturer OBD system is not 
30

required to also identify each of the continuously misfiring cylinders 

individually through separate fault codes. 

(2.2) Malfunction Criteria: 

(2.2.1) The OBD system shall detect a misfire malfunction when one or more 

cylinders are continuously misfiring. 

(2.2.2) Additionally, for 2013 and subsequent model year engines equipped with 

sensors that can detect combustion or combustion quality (e.g., for use in 

homogeneous charge compression ignition (HCCI) control systems), the 

OBD system shall detect a misfire malfunction causing the engine’s 

NMHC, CO, or NOx emissions to exceed 2.0 times the applicable 

standards or the engine’s PM emissions to exceed the applicable 

standard plus 0.02 g/bhp-hr. 

(A) Manufacturers shall determine the percentage of misfire evaluated in 

1000 revolution increments that would cause NMHC, CO, or NOx 

emissions from an emission durability demonstration engine to exceed 2.0 

times any of the applicable standards or PM emissions to exceed the 

applicable standard plus 0.02 g/bhp-hr if the percentage of misfire were 

present from the beginning of the test. To establish this percentage of 

misfire, the manufacturer shall utilize misfire events occurring at equally 

spaced, complete engine cycle intervals, across randomly selected 

cylinders throughout each 1000-revolution increment. If this percentage 

of misfire is determined to be lower than one percent, the manufacturer 

may set the malfunction criteria at one percent. 

(B) Subject to Executive Officer approval, a manufacturer may employ other 

revolution increments. The Executive Officer shall grant approval upon 

determining that the manufacturer has demonstrated that the strategy 

would be equally effective and timely in detecting misfire. 

(2.2.3) A malfunction shall be detected if the percentage of misfire established in 

section (e)(2.2.2)(A) is exceeded regardless of the pattern of misfire 

events (e.g., random, equally spaced, continuous). 

(2.2.4) For multiple cylinder misfire situations that result in a misfire rate greater 

than or equal to 50 percent, the OBD system shall only be required to 

detect a misfire malfunction for situations that are caused by a single 

component failure. 

(2.3) Monitoring Conditions: 

(2.3.1) The OBD system shall monitor for misfire during engine idle conditions at 

least once per driving cycle in which the monitoring conditions for misfire 

are met. A manufacturer shall submit monitoring conditions to the 

Executive Officer for approval. The Executive Officer shall approve 

manufacturer-defined monitoring conditions that are determined (based 

on manufacturer-submitted data and/or other engineering documentation) 

to: (i) be technically necessary to ensure robust detection of malfunctions 

(e.g., avoid false passes and false detection of malfunctions), (ii) require 

no more than 1000 cumulative engine revolutions, and (iii) do not require 

any single continuous idle operation of more than 15 seconds to make a 

determination that a malfunction is present (e.g., a decision can be made 

with data gathered during several idle operations of 15 seconds or less); 
31

or satisfy the requirements of (d)(3.1) with alternative engine operating 

conditions. 

(2.3.2) Manufacturers may request Executive Officer approval to use alternate 

monitoring conditions (e.g., off-idle). The Executive Officer shall approve 

alternate monitoring conditions that are determined (based on 

manufacturer-submitted data and/or other engineering documentation) to 

ensure equivalent robust detection of malfunctions and equivalent 

timeliness in detection of malfunctions. 

(2.3.3) Additionally, for 2013 and subsequent model year engines equipped with 

sensors that can detect combustion or combustion quality: 

(A) The OBD system shall continuously monitor for misfire under all positive 

torque engine speeds and load conditions. 

(B) If a monitoring system cannot detect all misfire patterns under all required 

engine speed and load conditions as required in section (e)(2.3.23)(A), 

the manufacturer may request Executive Officer approval to accept the 

monitoring system. In evaluating the manufacturer’s request, the 

Executive Officer shall consider the following factors: the magnitude of the 

region(s) in which misfire detection is limited, the degree to which misfire 

detection is limited in the region(s) (i.e., the probability of detection of 

misfire events), the frequency with which said region(s) are expected to be 

encountered in-use, the type of misfire patterns for which misfire detection 

is troublesome, and demonstration that the monitoring technology 

employed is not inherently incapable of detecting misfire under required 

conditions (i.e., compliance can be achieved on other engines). The 

evaluation shall be based on the following misfire patterns: equally spaced 

misfire occurring on randomly selected cylinders, single cylinder 

continuous misfire, and paired cylinder (cylinders firing at the same crank 

angle) continuous misfire. 

(2.4) MIL Illumination and Fault Code Storage: 

(2.4.1) General requirements for MIL illumination and fault code storage are set 

forth in section (d)(2). 

(2.4.2) Additionally, for 2013 and subsequent model year engines equipped with 

sensors that can detect combustion or combustion quality: 

(A) Upon detection of the percentage of misfire specified in section 

(e)(2.2.2)(A), the following criteria shall apply for MIL illumination and fault 

code storage: 

(i) A pending fault code shall be stored no later than after the fourth 

exceedance of the percentage of misfire specified in section (e)(2.2.2) 

during a single driving cycle. 

(ii) If a pending fault code is stored, the OBD system shall illuminate the 

MIL and store a confirmed/MIL-on fault code within 10 seconds if the 

percentage of misfire specified in section (e)(2.2.2) is again exceeded 

four times during: (a) the driving cycle immediately following the 

storage of the pending fault code, regardless of the conditions 

encountered during the driving cycle; or (b) on the next driving cycle in 

which similar conditions (see section (c)) to the engine conditions that 

occurred when the pending fault code was stored are encountered. 
32

(iii) The pending fault code may be erased at the end of the next driving 

cycle in which similar conditions to the engine conditions that occurred 

when the pending fault code was stored have been encountered 

without an exceedance of the specified percentage of misfire. The 

pending code may also be erased if similar conditions are not 

encountered during the next 80 driving cycles immediately following 

initial detection of the malfunction. 

(B) Storage of freeze frame conditions. 

(i) The OBD system shall store and erase freeze frame conditions either in 

conjunction with storing and erasing a pending fault code or in 

conjunction with storing a confirmed/MIL-on fault code and erasing a 

confirmed/previously MIL-on fault code. 

(ii) If freeze frame conditions are stored for a malfunction other than a 

misfire malfunction when a fault code is stored as specified in section 

(e)(2.4.2), the stored freeze frame information shall be replaced with 

freeze frame information regarding the misfire malfunction. 

(C) Storage of misfire conditions for similar conditions determination. Upon 

detection of misfire under section (e)(2.4.2), the OBD system shall store 

the following engine conditions: engine speed, load, and warm-up status 

of the first misfire event that resulted in the storage of the pending fault 

code. 

(D) Extinguishing the MIL. The MIL may be extinguished after three 

sequential driving cycles in which similar conditions have been 

encountered without an exceedance of the specified percentage of 

misfire. 

(3) EXHAUST GAS RECIRCULATION (EGR) SYSTEM MONITORING 

(3.1) Requirement: 

(3.1.1) The OBD system shall monitor the EGR system on engines so-equipped 

for low flow rate, high flow rate, and slow response malfunctions. For 

engines equipped with EGR coolers (e.g., heat exchangers), the OBD 

system shall monitor the cooler system for insufficient cooling 

malfunctions. The individual electronic components (e.g., actuators, 

valves, sensors) that are used in the EGR system shall be monitored in 

accordance with the comprehensive component requirements in section 

(g)(3). 

(3.1.2) For engines with other charge control strategies that affect EGR flow (e.g., 

systems that modify EGR flow to achieve a desired fresh air flow rate

instead of a desired EGR flow rate), the manufacturer shall submit a 

monitoring plan to the Executive Officer for approval. The Executive 

Officer shall approve the request upon determining that the manufacturer 

has submitted data and an engineering evaluation that demonstrate that 

the monitoring plan is as reliable and effective as the monitoring plan 

required for EGR systems under section (e)(3).

(3.2) Malfunction Criteria: 

(3.2.1) Low Flow: The OBD system shall detect a malfunction of the EGR system 

prior to a decrease from the manufacturer's specified EGR flow rate that 

would cause an engine’s NMHC, CO, or NOx emissions to exceed 2.0 
33

times any of the applicable standards or the engine’s PM emissions to 

exceed the applicable standard plus 0.02 g/bhp-hr. For engines in which 

no failure or deterioration of the EGR system that causes a decrease in 

flow could result in an engine’s emissions exceeding these levels, the 

OBD system shall detect a malfunction when either the EGR system has 

reached its control limits such that it cannot increase EGR flow to achieve 

the commanded flow rate or, for non-feedback controlled EGR systems, 

the EGR system has no detectable amount of EGR flow when EGR flow is 

expected. 

(3.2.2) High Flow: The OBD system shall detect a malfunction of the EGR 

system, including a leaking EGR valve (i.e., exhaust gas flowing through 

the valve when the valve is commanded closed), prior to an increase from 

the manufacturer's specified EGR flow rate that would cause an engine’s 

NMHC, CO, or NOx emissions to exceed 2.0 times any of the applicable 

standards or the engine’s PM emissions to exceed the applicable 

standard plus 0.02 g/bhp-hr. For engines in which no failure or 

deterioration of the EGR system that causes an increase in flow could 

result in an engine’s emissions exceeding these levels, the OBD system 

shall detect a malfunction when either the EGR system has reached its 

control limits such that it cannot reduce EGR flow to achieve the 

commanded flow rate or, for non-feedback controlled EGR systems, the 

EGR system has maximum detectable EGR flow when little or no EGR 

flow is expected. 

(3.2.3) Slow Response: The OBD system shall detect a malfunction of the EGR 

system prior to any failure or deterioration in the capability of the EGR 

system response (e.g., capability to achieve the commandedspecified flow 

rate within a manufacturer-specified time) that would cause an engine’s 

NMHC, CO, or NOx emissions to exceed 2.0 times any of the applicable 

standards or the engine’s PM emissions to exceed the applicable 

standard plus 0.02 g/bhp-hr. The OBD system shall monitor both the 

capability of the EGR system response under both increasing and 

decreasing EGR flow ratesto respond to a commanded/expected increase 

in flow and the capability of the EGR system to respond to a commanded

decrease in flow. For engines in which no failure or deterioration of the 

EGR system response could result in an engine’s emissions exceeding 

these levels, the OBD system shall detect a malfunction of the EGR

system when no detectable response to a change in commanded or 

expected flow rate occurs.

(3.2.4) Feedback control: Except as provided for in section (e)(3.2.6), if the 

engine is equipped with feedback or feed-forward control of the EGR 

system (e.g., feedback control of flow, valve position, pressure differential 

across the valve via intake throttle or exhaust backpressure), the OBD 

system shall detect a malfunction: 

(A) If the system fails to begin feedback control within a manufacturer 

specified time interval; 

(B) If a failure or deterioration causes open loop or default operation; or 
34

(C) If feedback the control system has used up all of the adjustment allowed 

by the manufacturer or reached its maximum authority and cannot 

achieve the target. 

(3.2.5) EGR Cooler Performance: The OBD system shall detect a malfunction of 

the EGR cooler system cooler prior to a reduction from the manufacturer's 

specified cooling performance that would cause an engine’s NMHC, CO, 

or NOx emissions to exceed 2.0 times any of the applicable standards or 

the engine’s PM emissions to exceed the applicable standard plus 0.02 

g/bhp-hr. For engines in which no failure or deterioration of the EGR 

cooler system cooler could result in an engine’s emissions exceeding 

these levels, the OBD system shall detect a malfunction when the system 

has no detectable amount of EGR cooling.

(3.2.6) EGR Catalyst Performance: For catalysts located in the EGR system on 

2013 and subsequent model year engines and used to convert 

constituents to reduce emissions or protect or extend the durability of 

other emission-related components (e.g., to reduce fouling of an EGR 

cooler or valve), the OBD system shall detect a malfunction when the 

catalyst has no detectable amount of constituent (e.g., hydrocarbons, 

soluble organic fractions) oxidation.

(3.2.6)(3.2.7) A manufacturer may request Executive Officer approval to 

temporarily disable monitoring for the malfunction criteria specified in 

section (e)(3.2.4)(C) during conditions that a manufacturer cannot robustly 

distinguish between a malfunctioning system and a properly operating 

system. The Executive Officer shall approve the disablement upon the 

manufacturer submitting data and/or analysis demonstrating that the 

control system, when operating as designed on an engine with all 

emission controls working properly, routinely operates during these 

conditions with all of the adjustment allowed by the manufacturer used up. 

(3.2.7)(3.2.8) In lieu of detecting the malfunctions specified in sections 

(e)(3.2.4)(A) and (B) with an EGR system-specific monitor, the OBD 

system may monitor the individual parameters or components that are 

used as inputs for EGR system feedback control provided that the 

monitors detect all malfunctions that meet the criteria in sections 

(e)(3.2.4)(A) and (B). 

(3.2.9) For purposes of determining the EGR cooler performance malfunction 

criteria in section (e)(3.2.5) for EGR cooler systems that consist of more 

than one cooler (e.g., a pre-cooler and a main cooler, two or more coolers 

in series), the manufacturer shall submit an EGR cooler system aging and 

monitoring plan to the Executive Officer for review and approval. The plan 

shall include the description and location of each component, the 

monitoring strategy for each component and combination of components, 

and the method for determining the malfunction criteria of section 

(e)(3.2.5) including the deterioration/aging process. Executive Officer 

approval of the plan shall be based on the representativeness of the aging 

to real world EGR cooler system component deterioration under normal 

and malfunctioning engine operating conditions and the effectiveness of 

the method used to determine the malfunction criteria of section 

(e)(3.2.5).
35

(3.3) Monitoring Conditions: 

(3.3.1) Except as provided in section (e)(3.3.4), Tthe OBD system shall monitor 

continuously for malfunctions identified in sections (e)(3.2.1), (3.2.2), and 

(e)(3.2.4) (i.e., EGR low and high flow, feedback control). 

(3.3.2) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (e)(3.2.3) (i.e., slow response) in accordance with 

sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements), with the 

exception that monitoring shall occur every time the monitoring conditions 

are met during the driving cycle in lieu of once per driving cycle as 

required in section (d)(3.1.2). For purposes of tracking and reporting as 

required in section (d)(3.2.1), all monitors used to detect malfunctions 

identified in section (e)(3.2.3) shall be tracked separately but reported as 

a single set of values as specified in section (d)(5.2.2). 

(3.3.3) Manufacturers shall define the monitoring conditions for malfunctions 

identified in sections (e)(3.2.5) and (e)(3.2.6) (i.e., cooler performance and 

EGR catalyst performance) in accordance with sections (d)(3.1) and 

(d)(3.2) (i.e., minimum ratio requirements). For purposes of tracking and 

reporting as required in section (d)(3.2.1), all monitors used to detect 

malfunctions identified in section (e)(3.2.5) shall be tracked separately but 

reported as a single set of values as specified in section (d)(5.2.2). 

(3.3.4) Manufacturers may request Executive Officer approval to temporarily 

disable the EGR system checkcontinuous monitoring, under specific 

conditions technically necessary to ensure robust detection of

malfunctions and to avoid false passes and false indications of 

malfunctions (e.g., disable EGR low flow monitoring when no or very little 

flow is commanded, disable EGR high and low flow monitoring when 

freezing may affect performance of the system). The Executive Officer 

shall approve the request upon determining that the manufacturer has 

submitted data and/or an engineering evaluation which demonstrate that a 

reliable check cannot be made when these conditions exist properly 

operating EGR system cannot be distinguished from a malfunctioning 

EGR system and that the disablement interval is limited only to that which 

is technically necessary. 

(3.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(4) BOOST PRESSURE CONTROL SYSTEM MONITORING 

(4.1) Requirement: 

(4.1.1) The OBD system shall monitor the boost pressure control system (e.g., 

turbocharger) on engines so-equipped for under and over boost 

malfunctions and slow response malfunctions. For engines equipped with 

variable geometry turbochargers (VGT), the OBD system shall monitor the 

VGT system for slow response malfunctions. For engines equipped with 

charge air cooler systems, the OBD system shall monitor the charge air 

cooler system for cooling system performance malfunctions. The 

individual electronic components (e.g., actuators, valves, sensors) that are 

used in the boost pressure control system shall be monitored in 
36

accordance with the comprehensive component requirements in section 

(g)(3). 

(4.1.2) For engines with other charge control strategies that affect boost pressure 

(e.g., systems that modify boost pressure to achieve a desired air-fuel 

ratio instead of a desired boost pressure), the manufacturer shall submit a 

monitoring plan to the Executive Officer for approval. The Executive 

Officer shall approve the request upon determining that the manufacturer 

has submitted data and an engineering evaluation that demonstrate that 

the monitoring plan is as reliable and effective as the monitoring plan 

required for boost pressure control systems under section (e)(4).

(4.2) Malfunction Criteria:

(4.2.1) Underboost: The OBD system shall detect a malfunction of the boost 

pressure control system prior to a decrease from the manufacturer's 

commanded or expected boost pressure that would cause an engine’s 

NMHC, CO, or NOx emissions to exceed 2.0 times any of the applicable 

standards or the engine’s PM emissions to exceed the applicable 

standard plus 0.02 g/bhp-hr. For engines in which no failure or 

deterioration of the boost pressure control system that causes a decrease 

in boost could result in an engine’s emissions exceeding these levels, the 

OBD system shall detect a malfunction when either the boost system has 

reached its control limits such that it cannot increase boost to achieve the 

commanded boost pressure or, for non-feedback controlled boost 

systems, the boost system has no detectable amount of boost when boost 

is expected. 

(4.2.2) Overboost: The OBD system shall detect a malfunction of the boost 

pressure control system prior to an increase from the manufacturer's 

commanded or expected boost pressure that would cause an engine's 

NMHC, CO, or NOx emissions to exceed 2.0 times any of the applicable 

standards or the engine’s PM emissions to exceed the applicable 

standard plus 0.02 g/bhp-hr. For engines in which no failure or 

deterioration of the boost pressure control system that causes an increase 

in boost could result in an engine’s emissions exceeding these levels, the 

OBD system shall detect a malfunction when either the boost system has 

reached its control limits such that it cannot decrease boost to achieve the 

commanded boost pressure or, for non-feedback controlled boost 

systems, the boost system has maximum detectable boost when little or 

no boost is expected. 

(4.2.3) VGT sSlow response: 

(A) For 2010 through 2012 model year engines equipped with variable 

geometry turbochargers (VGT), Tthe OBD system shall detect a 

malfunction prior to any failure or deterioration in the capability of the VGT 

system to achieve the commanded turbocharger geometry within a 

manufacturer-specified time that would cause an engine's NMHC, CO, or 

NOx emissions to exceed 2.0 times any of the applicable standards or the 

engine’s PM emissions to exceed the applicable standard plus 0.02 

g/bhp-hr. For engines in which no failure or deterioration of the VGT 

system response could result in an engine’s emissions exceeding these 

levels, the OBD system shall detect a malfunction of the VGT system 
37

when proper functionalno detectable response of the system to computer 

a change in commandsed turbocharger geometry does not occurs.

(B) For 2013 and subsequent model year engines, the OBD system shall 

detect a malfunction prior to any failure or deterioration in the boost 

pressure control system response (e.g., capability to achieve the 

commanded or expected boost pressure within a manufacturer-specified 

time) that would cause an engine's NMHC, CO, or NOx emissions to 

exceed 2.0 times any of the applicable standards or the engine’s PM 

emissions to exceed the applicable standard plus 0.02 g/bhp-hr. For 

engines in which no failure or deterioration of the boost system response 

could result in an engine’s emissions exceeding these levels, the OBD 

system shall detect a malfunction of the boost system when no detectable 

response to a commanded or expected change in boost pressure occurs.

(4.2.4) Charge Air Undercooling: The OBD system shall detect a malfunction of 

the charge air cooling system prior to a decrease from the manufacturer's 

specified cooling rate that would cause an engine’s NMHC, CO, or NOx 

emissions to exceed 2.0 times any of the applicable standards or the 

engine’s PM emissions to exceed the applicable standard plus 0.02 

g/bhp-hr. For engines in which no failure or deterioration of the charge air 

cooling system that causes a decrease in cooling performance could 

result in an engine’s emissions exceeding these levels, the OBD system 

shall detect a malfunction when the system has no detectable amount of 

charge air cooling.

(4.2.5) Feedback control: Except as provided for in section (e)(4.2.6), if the 

engine is equipped with feedback or feed-forward control of the boost 

pressure system (e.g., control of VGT variable geometry turbocharger 

position, turbine speed, manifold pressure) the OBD system shall detect a 

malfunction: 

(A) If the system fails to begin feedback control within a manufacturer 

specified time interval; 

(B) If a failure or deterioration causes open loop or default operation; or 

(C) If feedback the control system has used up all of the adjustment allowed 

by the manufacturer or reached its maximum authority and cannot 

achieve the target. 

(4.2.6) A manufacturer may request Executive Officer approval to temporarily 

disable monitoring for the malfunction criteria specified in section 

(e)(4.2.5)(C) during conditions that a manufacturer cannot robustly 

distinguish between a malfunctioning system and a properly operating 

system. The Executive Officer shall approve the disablement upon the 

manufacturer submitting data and/or analysis demonstrating that the 

control system, when operating as designed on an engine with all 

emission controls working properly, routinely operates during these 

conditions with all of the adjustment allowed by the manufacturer used up. 

(4.2.7) In lieu of detecting the malfunctions specified in sections (e)(4.2.5)(A) and 

(B) with a boost pressure system-specific monitor, the OBD system may 

monitor the individual parameters or components that are used as inputs 

for boost pressure system feedback control provided that the monitors 
38

detect all malfunctions that meet the criteria in sections (e)(4.2.5)(A) and 

(B). 

(4.2.8) For purposes of determining the charge air cooling performance 

malfunction criteria in section (e)(4.2.4) for charge air cooling systems that 

consist of more than one cooler (e.g., a pre-cooler and a main cooler, two 

or more coolers in series), the manufacturer shall submit a charge air 

cooling system aging and monitoring plan to the Executive Officer for 

review and approval. The plan shall include the description and location 

of each component, the monitoring strategy for each component and 

combination of components, and the method for determining the 

malfunction criteria of section (e)(4.2.4) including the deterioration/aging 

process. Executive Officer approval of the plan shall be based on the 

representativeness of the aging to real world charge air cooling system 

component deterioration under normal and malfunctioning engine 

operating conditions and the effectiveness of the method used to 

determine the malfunction criteria of section (e)(4.2.4).

(4.3) Monitoring Conditions: 

(4.3.1) Except as provided in section (e)(4.3.4), Tthe OBD system shall monitor 

continuously for malfunctions identified in sections (e)(4.2.1), (4.2.2), and 

(4.2.5) (i.e., over and under boost, feedback control). 

(4.3.2) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (e)(4.2.3) (i.e., VGT slow response) in accordance 

with sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements), with 

the exception that monitoring shall occur every time the monitoring 

conditions are met during the driving cycle in lieu of once per driving cycle 

as required in section (d)(3.1.2). For purposes of tracking and reporting 

as required in section (d)(3.2.1), all monitors used to detect malfunctions 

identified in section (e)(4.2.3) shall be tracked separately but reported as 

a single set of values as specified in section (d)(5.2.2). 

(4.3.3) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (e)(4.2.4) (i.e., charge air cooler performance) in 

accordance with sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio 

requirements). For purposes of tracking and reporting as required in 

section (d)(3.2.1), all monitors used to detect malfunctions identified in 

section (e)(4.2.4) shall be tracked separately but reported as a single set 

of values as specified in section (d)(5.2.2). 

(4.3.4) Manufacturers may request Executive Officer approval to temporarily 

disable continuous monitoring under conditions technically necessary to 

ensure robust detection of malfunctions and to avoid false passes and 

false indications of malfunctions (e.g., disable monitoring of underboost 

when commanded or expected boost pressure is very low). The 

Executive Officer shall approve the request upon determining that the 

manufacturer has submitted data and/or an engineering evaluation which 

demonstrate that a properly operating system cannot be distinguished 

from a malfunctioning system and that the disablement interval is limited 

only to that which is technically necessary.

(4.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 
39

(5) NON-METHANE HYDROCARBON (NMHC) CONVERTING CATALYST

MONITORING 

(5.1) Requirement: The OBD system shall monitor the NMHC converting 

catalyst(s) for proper NMHC conversion capability. For engines equipped 

with catalyzed PM filters that convert NMHC emissions, the catalyst function 

of the PM filter shall be monitored in accordance with the PM filter 

requirements in section (e)(8). 

(5.2) Malfunction Criteria: 

(5.2.1) For purposes of section (e)(5), each catalyst in a series configuration that 

converts NMHC shall be monitored either individually or in combination 

with others. 

(5.2.2) Conversion Efficiency: 

(A) For 2010 through 2012 model year engines, Tthe OBD system shall 

detect an NMHC catalyst malfunction when the catalyst conversion 

capability decreases to the point that NMHC emissions exceed 2.0 times 

any of the applicable standards. 

(B) For 2013 and subsequent model year engines, the OBD system shall 

detect an NMHC catalyst malfunction when the catalyst conversion 

capability decreases to the point that NMHC emissions exceed 2.0 times 

any of the applicable standards or NOx emissions exceed any of the 

applicable standards by more than 0.2 g/bhp-hr (e.g., cause emissions to 

exceed 0.4 g/bhp-hr if the emission standard is 0.2 g/bhp-hr). 

(B)(C) If no failure or deterioration of the catalyst NMHC conversion capability 

could result in an engine’s NMHC or NOx emissions exceeding 2.0 times 

any of the applicable standardsmalfunction criteria of section (e)(5.2.2), 

the OBD system shall detect a malfunction when the catalyst has no 

detectable amount of NMHC or NOx conversion capability. 

(5.2.3) Other Aftertreatment Assistance Functions: 

(A) For catalysts used to generate an exotherm to assist PM filter 

regeneration, the OBD system shall detect a malfunction when the 

catalyst is unable to generate a sufficient exotherm to achieve 

regeneration of the PM filter. 

(B) For 2013 and subsequent model year engines, Ffor catalysts used to 

generate a feedgas constituency to assist SCR systems (e.g., to increase 

NO2 concentration upstream of an SCR system), the OBD system shall 

detect a malfunction when the catalyst is unable to generate the 

necessary feedgas constituents for proper SCR system operation. 

(C) For catalysts located downstream of a PM filter and used to convert 

NMHC emissions during PM filter regeneration, the OBD system shall 

detect a malfunction when the catalyst has no detectable amount of 

NMHC conversion capability. 

(D) For catalysts located downstream of an SCR system (e.g., to prevent 

ammonia slip), the OBD system shall detect a malfunction when the 

catalyst has no detectable amount of NMHC, CO, NOx, or PM conversion

capability. Monitoring of the catalyst is not required if there is no 

measurable emission impact on the criteria pollutants (i.e., NMHC, CO, 
40

NOx, and PM) during any reasonable driving condition where the catalyst 

is most likely to affect criteria pollutants (e.g., during conditions most likely 

to result in ammonia generation or excessive reductant delivery).

(5.2.4) Catalyst System Aging and Monitoring 

(A) For purposes of determining the catalyst malfunction criteria in sections 

(e)(5.2.2) and (5.2.3) for individually monitored catalysts, the manufacturer 

shall use a catalyst deteriorated to the malfunction criteria using methods 

established by the manufacturer to represent real world catalyst 

deterioration under normal and malfunctioning engine operating 

conditions. If the catalyst system contains catalysts in parallel (e.g., a two 

bank exhaust system where each bank has its own catalyst), the 

malfunction criteria shall be determined with the “parallel” catalysts equally 

deteriorated.

(B) For purposes of determining the catalyst malfunction criteria in sections 

(e)(5.2.2) and (5.2.3) for catalysts monitored in combination with others, 

the manufacturer shall submit a catalyst system aging and monitoring plan 

to the Executive Officer for review and approval. The plan shall include 

the description, emission control purpose, and location of each 

component, the monitoring strategy for each component and/or 

combination of components, and the method for determining the 

malfunction criteria of sections (e)(5.2.2) and (5.2.3) including the 

deterioration/aging process. If the catalyst system contains catalysts in 

parallel (e.g., a two bank exhaust system where each bank has its own 

catalyst), the malfunction criteria shall be determined with the “parallel” 

catalysts equally deteriorated. Executive Officer approval of the plan shall 

be based on the representativeness of the aging to real world catalyst 

system component deterioration under normal and malfunctioning engine 

operating conditions, the effectiveness of the method used to determine 

the malfunction criteria of section (e)(5.2), the ability of the component 

monitor(s) to pinpoint the likely area of malfunction and ensure the correct 

components are repaired/replaced in-use, and the ability of the 

component monitor(s) to accurately verify that each catalyst component is 

functioning as designed and as required in sections (e)(5.2.2) and (5.2.3). 

(5.3) Monitoring Conditions: 

(5.3.1) Manufacturers shall define the monitoring conditions for malfunctions 

identified in sections (e)(5.2.2) and (5.2.3) in accordance with sections 

(d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). For purposes of 

tracking and reporting as required in section (d)(3.2.1), all monitors used 

to detect malfunctions identified in sections (e)(5.2.2) and (5.2.3) shall be 

tracked separately but reported as a single set of values as specified in 

section (d)(5.2.2). 

(5.4) MIL Illumination and Fault Code Storage: 

(5.4.1) General requirements for MIL illumination and fault code storage are set 

forth in section (d)(2). 

(5.4.2) The monitoring method for the catalyst(s) shall be capable of detecting all 

instances, except diagnostic self-clearing, when a catalyst fault code has 

been cleared but the catalyst has not been replaced (e.g., catalyst 

overtemperature histogram approaches are not acceptable). 
41

(6) OXIDES OF NITROGEN (NOx) CONVERTING CATALYST MONITORING 

(6.1) Requirement: The OBD system shall monitor the NOx converting catalyst(s) 

for proper conversion capability. For engines equipped with selective 

catalytic reduction (SCR) systems or other catalyst systems that utilize an 

active/intrusive reductant injection (e.g., active lean NOx catalysts utilizing 

diesel fuel injection), the OBD system shall monitor the SCR or 

active/intrusive reductant injection system for proper performance. The 

individual electronic components (e.g., actuators, valves, sensors, heaters, 

pumps) in the SCR or active/intrusive reductant injection system shall be 

monitored in accordance with the comprehensive component requirements in 

section (g)(3). 

(6.2) Malfunction Criteria: For purposes of section (e)(6), each catalyst in a series 

configuration that converts NOx shall be monitored either individually or in 

combination with others. 

(6.2.1) Conversion Efficiency: 

(A) For 2010 through 2012 model year engines: 

(i) The OBD system shall detect a catalyst malfunction when the catalyst 

conversion capability decreases to the point that would cause an 

engine's NOx emissions to exceed any of the applicable standards by 

more than 0.34 g/bhp-hr (e.g., cause emissions to exceed 0.56 g/bhphr if the emission standard is 0.2 g/bhp-hr) as measured from an 

applicable cycle emission test (i.e., FTP or SET). 

(ii) If no failure or deterioration of the catalyst NOx conversion capability 

could result in an engine’s NOx emissions exceeding any of the 

applicable standards by more than 0.34 g/bhp-hr, the OBD system 

shall detect a malfunction when the catalyst has no detectable amount 

of NOx conversion capability. 

(B) For 2013 and subsequent model year engines: 

(i) The OBD system shall detect a catalyst malfunction when the catalyst 

conversion capability decreases to the point that would cause an 

engine's NOx emissions to exceed any of the applicable NOx 

standards by more than 0.2 g/bhp-hr (e.g., cause emissions to exceed 

0.4 g/bhp-hr if the emission standard is 0.2 g/bhp-hr) as measured 

from an applicable cycle emission test or 2.0 times the applicable 

NMHC standard. 

(ii) If no failure or deterioration of the catalyst system NOx conversion 

capability could result in an engine’s NOx or NMHC emissions 

exceeding any of the applicable standards by more than 0.2 g/bhp-hr

the applicable malfunction criteria of section (e)(6.2.1)(B)(i), the OBD 

system shall detect a malfunction when the catalyst has no detectable 

amount of NOx or NMHC conversion capability. 

(6.2.2) Selective Catalytic Reduction (SCR) or Other Active/Intrusive Reductant 

Injection System Performance: 

(A) Reductant Delivery Performance: 

(i) For 2010 through 2012 model year engines, the OBD system shall 

detect a malfunction prior to any failure or deterioration of the system 

to properly regulate reductant delivery (e.g., urea injection, separate 
42

injector fuel injection, post injection of fuel, air assisted 

injection/mixing) that would cause an engine's NOx emissions to 

exceed any of the applicable standards by more than 0.34 g/bhp-hr 

(e.g., cause emissions to exceed 0.56 g/bhp-hr if the emission 

standard is 0.2 g/bhp-hr) as measured from an applicable cycle 

emission test (i.e., FTP or SET). If no failure or deterioration of the 

SCR system could result in an engine’s NOx emissions exceeding any 

of the applicable standards by more than 0.34 g/bhp-hr, the OBD 

system shall detect a malfunction when the system has reached its 

control limits such that it is no longer able to deliver the desired 

quantity of reductant. 

(ii) For 2013 and subsequent model year engines, the OBD system shall 

detect a system malfunction prior to any failure or deterioration of the 

system to properly regulate reductant delivery (e.g., urea injection, 

separate injector fuel injection, post injection of fuel, air assisted 

injection/mixing) that would cause an engine’s NOx emissions to 

exceed any of the applicable NOx standards by more than 0.2 g/bhphr (e.g., cause emissions to exceed 0.4 g/bhp-hr if the emission 

standard is 0.2 g/bhp-hr) as measured from an applicable cycle 

emission test or 2.0 times the applicable NMHC standard. If no failure 

or deterioration of the SCR system could result in an engine’s NOx or 

NMHC emissions exceeding the applicable standards by more than 

0.2 g/bhp-hr applicable malfunction criteria above, the OBD system 

shall detect a malfunction when the system has reached its control 

limits such that it is no longer able to deliver the desired quantity of 

reductant. 

(B) If the catalyst system uses a reductant other than the fuel used for the 

engine or uses a reservoir/tank for the reductant that is separate from the 

fuel tank used for the engine, the OBD system shall detect a malfunction 

when there is no longer sufficient reductant available to properly operate 

the reductant system (e.g., the reductant tank is empty). 

(C) If the catalyst system uses a reservoir/tank for the reductant that is 

separate from the fuel tank used for the engine, the OBD system shall 

detect a malfunction when an improper reductant is used in the reductant 

reservoir/tank (e.g., the reductant tank is filled with something other than 

the reductant). 

(D) Feedback control: Except as provided for in section (e)(6.2.2)(E), if the 

engine is equipped with feedback or feed-forward control of the reductant 

injection, the OBD system shall detect a malfunction: 

(i) If the system fails to begin feedback control within a manufacturer 

specified time interval; 

(ii) If a failure or deterioration causes open loop or default operation; or 

(iii) If the feedback control system has used up all of the adjustment 

allowed by the manufacturer or reached its maximum authority and 

cannot achieve the target. 

(E) A manufacturer may request Executive Officer approval to temporarily 

disable monitoring for the malfunction criteria specified in section 

(e)(6.2.2)(D)(iii) during conditions that a manufacturer cannot robustly 
43

distinguish between a malfunctioning system and a properly operating 

system. The Executive Officer shall approve the disablement upon the 

manufacturer submitting data and/or analysis demonstrating that the 

control system, when operating as designed on an engine with all 

emission controls working properly, routinely operates during these 

conditions with all of the adjustment allowed by the manufacturer used up. 

(F) In lieu of detecting the malfunctions specified in sections (e)(6.2.2)(D)(i) 

and (ii) with a reductant injection system-specific monitor, the OBD system 

may monitor the individual parameters or components that are used as 

inputs for reductant injection feedback control provided that the monitors 

detect all malfunctions that meet the criteria in sections (e)(6.2.2)(D)(i) 

and (ii). 

(6.2.3) Catalyst System Aging and Monitoring 

(A) For purposes of determining the catalyst malfunction criteria in section 

(e)(6.2.1) for individually monitored catalysts, the manufacturer shall use a 

catalyst deteriorated to the malfunction criteria using methods established 

by the manufacturer to represent real world catalyst deterioration under 

normal and malfunctioning engine operating conditions. If the catalyst 

system contains catalysts in parallel (e.g., a two bank exhaust system 

where each bank has its own catalyst), the malfunction criteria shall be 

determined with the “parallel” catalysts equally deteriorated.

(B) For purposes of determining the catalyst malfunction criteria in section 

(e)(6.2.1) for catalysts monitored in combination with others, the 

manufacturer shall submit a catalyst system aging and monitoring plan to 

the Executive Officer for review and approval. The plan shall include the 

description, emission control purpose, and location of each component, 

the monitoring strategy for each component and/or combination of 

components, and the method for determining the malfunction criteria of 

section (e)(6.2.1) including the deterioration/aging process. If the catalyst 

system contains catalysts in parallel (e.g., a two bank exhaust system 

where each bank has its own catalyst), the malfunction criteria shall be 

determined with the “parallel” catalysts equally deteriorated. Executive 

Officer approval of the plan shall be based on the representativeness of 

the aging to real world catalyst system component deterioration under 

normal and malfunctioning engine operating conditions, the effectiveness 

of the method used to determine the malfunction criteria of section 

(e)(6.2.1), the ability of the component monitor(s) to pinpoint the likely 

area of malfunction and ensure the correct components are 

repaired/replaced in-use, and the ability of the component monitor(s) to 

accurately verify that each catalyst component is functioning as designed 

and as required in section (e)(6.2.1). 

(6.3) Monitoring Conditions: 

(6.3.1) Manufacturers shall define the monitoring conditions for malfunctions 

identified in sections (e)(6.2.1) and (e)(6.2.2)(C) (i.e., catalyst efficiency, 

improper reductant) in accordance with sections (d)(3.1) and (d)(3.2) (i.e., 

minimum ratio requirements). For purposes of tracking and reporting as 

required in section (d)(3.2.1), all monitors used to detect malfunctions 
44

identified in section (e)(6.2.1) shall be tracked separately but reported as 

a single set of values as specified in section (d)(5.2.2). 

(6.3.2) Except as provided in section (e)(6.3.3), Tthe OBD system shall monitor 

continuously for malfunctions identified in sections (e)(6.2.2)(A), (B), and 

(D) (e.g., SCR performance, insufficient reductant, feedback control). 

(6.3.3) Manufacturers may request Executive Officer approval to temporarily 

disable continuous monitoring under conditions technically necessary to 

ensure robust detection of malfunctions and to avoid false passes and 

false indications of malfunctions. The Executive Officer shall approve the 

request upon determining that the manufacturer has submitted data 

and/or an engineering evaluation which demonstrate that a properly 

operating system cannot be distinguished from a malfunctioning system 

and that the disablement interval is limited only to that which is technically 

necessary.

(6.4) MIL Illumination and Fault Code Storage: 

(6.4.1) Except as provided below for reductant faults, general requirements for 

MIL illumination and fault code storage are set forth in section (d)(2). 

(6.4.2) If the OBD system is capable of discerning that a system fault is being 

caused by a empty reductant tank: 

(A) The manufacturer may request Executive Officer approval to delay 

illumination of the MIL if the vehicle is equipped with an alternative 

indicator for notifying the vehicle operator of the malfunction. The 

Executive Officer shall approve the request upon determining the 

alternative indicator is of sufficient illumination and location to be readily 

visible under all lighting conditions and provides equivalent assurance that 

a vehicle operator will be promptly notified and that corrective action will 

be undertaken. 

(B) If the vehicle is not equipped with an alternative indicator and the MIL 

illuminates, the MIL may be immediately extinguished and the 

corresponding fault codes erased once the OBD system has verified that 

the reductant tank has been properly refilled and the MIL has not been 

illuminated for any other type of malfunction. 

(C) The Executive Officer may approve other strategies that provide 

equivalent assurance that a vehicle operator will be promptly notified and 

that corrective action will be undertaken. 

(6.4.3) The monitoring method for the catalyst(s) shall be capable of detecting all 

instances, except diagnostic self-clearing, when a catalyst fault code has 

been cleared but the catalyst has not been replaced (e.g., catalyst 

overtemperature histogram approaches are not acceptable). 

(7) NOx ADSORBER MONITORING 

(7.1) Requirement: The OBD system shall monitor the NOx adsorber(s) on engines 

so-equipped for proper performance. For engines equipped with 

active/intrusive injection (e.g., in-exhaust fuel and/or air injection) to achieve 

desorption of the NOx adsorber(s), the OBD system shall monitor the 

active/intrusive injection system for proper performance. The individual 

electronic components (e.g., injectors, valves, sensors) that are used in the 
45

active/intrusive injection system shall be monitored in accordance with the 

comprehensive component requirements in section (g)(3). 

(7.2) Malfunction Criteria: 

(7.2.1) NOx adsorber capability: 

(A) For 2010 through 2012 model year engines, the OBD system shall detect 

a NOx adsorber system malfunction when the NOx adsorber system 

capability decreases to the point that would cause an engine's NOx 

emissions to exceed any of the applicable standards by more than 0.3 

g/bhp-hr (e.g., cause emissions to exceed 0.5 g/bhp-hr if the emission 

standard is 0.2 g/bhp-hr) as measured from an applicable cycle emission 

test (i.e., FTP or SET). If no failure or deterioration of the NOx adsorber 

system capability could result in an engine’s NOx emissions exceeding 

any of the applicable standards by more than 0.3 g/bhp-hr, the OBD 

system shall detect a malfunction when the system has no detectable 

amount of NOx adsorber capability. 

(B) For 2013 and subsequent model year engines, the OBD system shall 

detect a NOx adsorber system malfunction when the NOx adsorber 

capability decreases to the point that would cause an engine's NOx 

emissions to exceed any of the applicable NOx standards by more than 

0.2 g/bhp-hr (e.g., cause emissions to exceed 0.4 g/bhp-hr if the emission 

standard is 0.2 g/bhp-hr) as measured from an applicable cycle emission 

test (i.e., FTP or SET) or 2.0 times the applicable NMHC standard. If no 

failure or deterioration of the NOx adsorber capability could result in an 

engine’s NOx or NMHC emissions exceeding the applicable malfunction 

criteria aboveany of the applicable standards by more than 0.2 g/bhp-hr, 

the OBD system shall detect a malfunction when the system has no 

detectable amount of NOx adsorber capability. 

(7.2.2) For systems that utilize active/intrusive injection (e.g., in-cylinder post fuel 

injection, in-exhaust air-assisted fuel injection) to achieve desorption of 

the NOx adsorber, the OBD system shall detect a malfunction if any 

failure or deterioration of the injection system’s ability to properly regulate 

injection causes the system to be unable to achieve desorption of the NOx 

adsorber. 

(7.2.3) Feedback control: Except as provided for in section (e)(7.2.4), if the 

engine is equipped with feedback or feed-forward control of the NOx 

adsorber or active/intrusive injection system (e.g., feedback control of 

injection quantity, time), the OBD system shall detect a malfunction: 

(A) If the system fails to begin feedback control within a manufacturer 

specified time interval; 

(B) If a failure or deterioration causes open loop or default operation; or 

(C) If feedback the control system has used up all of the adjustment allowed 

by the manufacturer or reached its maximum authority and cannot 

achieve the target. 

(7.2.4) A manufacturer may request Executive Officer approval to temporarily 

disable monitoring for the malfunction criteria specified in section 

(e)(7.2.3)(C) during conditions that a manufacturer cannot robustly 

distinguish between a malfunctioning system and a properly operating 

system. The Executive Officer shall approve the disablement upon the 
46

manufacturer submitting data and/or analysis demonstrating that the 

control system, when operating as designed on an engine with all 

emission controls working properly, routinely operates during these 

conditions with all of the adjustment allowed by the manufacturer used up. 

(7.2.5) In lieu of detecting the malfunctions specified in sections (e)(7.2.3)(A) and 

(B) with a NOx adsorber-specific monitor, the OBD system may monitor 

the individual parameters or components that are used as inputs for NOx 

adsorber or active/intrusive injection system feedback control provided 

that the monitors detect all malfunctions that meet the criteria in sections 

(e)(7.2.3)(A) and (B). 

(7.2.6) For purposes of determining the NOx adsorber system malfunction criteria 

in section (e)(7.2.1) for NOx adsorber systems that consist of more than 

one NOx adsorber (e.g., two or more adsorbers in series), the 

manufacturer shall submit a system aging and monitoring plan to the 

Executive Officer for review and approval. The plan shall include the 

description and location of each component, the monitoring strategy for 

each component and/or combination of components, and the method for 

determining the malfunction criteria of section (e)(7.2.1) including the 

deterioration/aging process. Executive Officer approval of the plan shall 

be based on the representativeness of the aging to real world NOx 

adsorber system component deterioration under normal and 

malfunctioning engine operating conditions, the effectiveness of the 

method used to determine the malfunction criteria of section (e)(7.2.1), 

the ability of the component monitor(s) to pinpoint the likely area of 

malfunction and ensure the correct components are repaired/replaced inuse, and the ability of the component monitor(s) to accurately verify that 

each NOx adsorber system component is functioning as designed and as 

required in section (e)(7.2.1).

(7.3) Monitoring Conditions: 

(7.3.1) Manufacturers shall define the monitoring conditions for malfunctions 

identified in sections (e)(7.2.1) (i.e., adsorber capability) in accordance 

with sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). For 

purposes of tracking and reporting as required in section (d)(3.2.1), all 

monitors used to detect malfunctions identified in sections (e)(7.2.1) shall 

be tracked separately but reported as a single set of values as specified in 

section (d)(5.2.2). 

(7.3.2) Except as provided in section (e)(7.3.3), Tthe OBD system shall monitor 

continuously for malfunctions identified in sections (e)(7.2.2) and (7.2.3) 

(e.g., injection function, feedback control). 

(7.3.3) Manufacturers may request Executive Officer approval to temporarily 

disable continuous monitoring under conditions technically necessary to 

ensure robust detection of malfunctions and to avoid false passes and 

false indications of malfunctions. The Executive Officer shall approve the 

request upon determining that the manufacturer has submitted data 

and/or an engineering evaluation which demonstrate that a properly 

operating system cannot be distinguished from a malfunctioning system 

and that the disablement interval is limited only to that which is technically 

necessary.
47

(7.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(8) PARTICULATE MATTER (PM) FILTER MONITORING 

(8.1) Requirement: The OBD system shall monitor the PM filter on engines soequipped for proper performance. For engines equipped with active 

regeneration systems that utilize an active/intrusive injection (e.g., in-exhaust 

fuel injection, in-exhaust fuel/air burner), the OBD system shall monitor the 

active/intrusive injection system for proper performance. The individual 

electronic components (e.g., injectors, valves, sensors) that are used in the 

active/intrusive injection system shall be monitored in accordance with the 

comprehensive component requirements in section (g)(3). 

(8.2) Malfunction Criteria: 

(8.2.1) Filtering Performance: 

(A) Except as specified in section (e)(8.2.1.)(B) below, fFor 2010 through 

2015 2012 model year engines, the OBD system shall detect a 

malfunction prior to a decrease in the filtering capability of the PM filter 

(e.g., cracking) that would cause an engine's PM emissions to exceed 

either of the following thresholds, whichever is higher: 0.07 g/bhp-hr as 

measured from an applicable emission test cycle (i.e., FTP or SET); or the 

applicable standard plus 0.06 g/bhp-hr (e.g., 0.07 g/bhp-hr if the emission 

standard is 0.01 g/bhp-hr). If no failure or deterioration of the PM filtering 

performance could result in an engine’s PM emissions exceeding these 

levels, the OBD system shall detect a malfunction when no detectable 

amount of PM filtering occurs.

(B) Except as specified in section (e)(8.2.1.)(C) below, for 2013 through 2015 

model year engines, the OBD system shall detect a malfunction prior to a 

decrease in the filtering capability of the PM filter (e.g., cracking) that 

would cause an engine's PM emissions to exceed either of the following 

thresholds, whichever is higher: 0.05 g/bhp-hr as measured from an 

applicable emission test cycle (i.e., FTP or SET); or the applicable 

standard plus 0.04 g/bhp-hr (e.g., 0.05 g/bhp-hr if the emission standard is 

0.01 g/bhp-hr). If no failure or deterioration of the PM filtering 

performance could result in an engine’s PM emissions exceeding these 

levels, the OBD system shall detect a malfunction when no detectable 

amount of PM filtering occurs. 

(B)(C) For 2013 through 2015 model year engines subject to (d)(7.2.2)(A) 

and for all 2016 and subsequent model year engines, the OBD system 

shall detect a malfunction prior to a decrease in the filtering capability of 

the PM filter that would cause an engine's PM emissions to exceed either 

of the following thresholds, whichever is higher: 0.03 g/bhp-hr as 

measured from an applicable emission test cycle (i.e., FTP or SET); or the 

applicable standard plus 0.02 g/bhp-hr (e.g., 0.03 g/bhp-hr if the emission 

standard is 0.01 g/bhp-hr). If no failure or deterioration of the PM filtering 

performance could result in an engine’s PM emissions exceeding these 

levels, the OBD system shall detect a malfunction when no detectable 

amount of PM filtering occurs. 
48

(8.2.2) Frequent Regeneration: The OBD system shall detect a malfunction when 

the PM filter regeneration occurs more frequencytly increases fromthan

(i.e., occurs more often than) the manufacturer’s specified regeneration 

frequency to a level such that it would cause an engine's NMHC 

emissions to exceed the following:

(A) For 2010 through 2012 model year engines, 2.0 times the applicable 

NMHC standards.

(B) For 2013 and subsequent model year engines, 2.0 times the applicable 

NMHC standards or the applicable NOx standard by more than 0.2 g/bhphr (e.g., cause NOx emissions to exceed 0.4 g/bhp-hr if the emission 

standard is 0.2 g/bhp-hr). 

(C) If no failure or deterioration causes an increase in the PM filter 

regeneration frequency that could result in an engine’s NMHC emissions 

exceeding 2.0 times the applicable standardsthe emission levels specified

above, the OBD system shall detect a malfunction when the PM filter 

regeneration frequency exceeds the manufacturer’s specified design limits 

for allowable regeneration frequency. 

(8.2.3) Incomplete regeneration: The OBD system shall detect a regeneration 

malfunction when the PM filter does not properly regenerate under 

manufacturer-defined conditions where regeneration is designed to occur. 

(8.2.4) NMHC conversion: For 2013 and subsequent model year engines, Ffor 

catalyzed PM filters that convert NMHC emissions, the OBD system shall 

monitor the catalyst function of the PM filter and detect a malfunction 

when the NMHC conversion capability decreases to the point that NMHC 

emissions exceed 2.0 times the applicable standards. If no failure or 

deterioration of the NMHC conversion capability could result in an 

engine’s NMHC emissions exceeding 2.0 times the applicable standards, 

the OBD system shall detect a malfunction when the system has no 

detectable amount of NMHC conversion capability. 

(8.2.5) Missing substrate: The OBD system shall detect a malfunction if either the 

PM filter substrate is completely destroyed, removed, or missing, or if the 

PM filter assembly is replaced with a muffler or straight pipe. 

(8.2.6) Active/Intrusive Injection: For systems that utilize active/intrusive injection 

(e.g., in-cylinder post fuel injection, in-exhaust air-assisted fuel injection) 

to achieve regeneration of the PM filter, the OBD system shall detect a 

malfunction if any failure or deterioration of the injection system’s ability to 

properly regulate injection causes the system to be unable to achieve 

regeneration of the PM filter. 

(8.2.7) Feedback Control: Except as provided for in section (e)(8.2.8), if the 

engine is equipped with feedback or feed-forward control of the PM filter 

regeneration (e.g., feedback control of oxidation catalyst inlet 

temperature, PM filter inlet or outlet temperature, in-cylinder or in-exhaust 

fuel injection), the OBD system shall detect a malfunction: 

(A) If the system fails to begin feedback control within a manufacturer 

specified time interval; 

(B) If a failure or deterioration causes open loop or default operation; or 
49

(C) If feedback the control system has used up all of the adjustment allowed 

by the manufacturer or reached its maximum authority and cannot 

achieve the target. 

(8.2.8) A manufacturer may request Executive Officer approval to temporarily 

disable monitoring for the malfunction criteria specified in section 

(e)(8.2.7)(C) during conditions that a manufacturer cannot robustly 

distinguish between a malfunctioning system and a properly operating 

system. The Executive Officer shall approve the disablement upon the 

manufacturer submitting data and/or analysis demonstrating that the 

control system, when operating as designed on an engine with all 

emission controls working properly, routinely operates during these 

conditions with all of the adjustment allowed by the manufacturer used up. 

(8.2.9) In lieu of detecting the malfunctions specified in sections (e)(8.2.7)(A) and 

(B) with a PM filter-specific monitor, the OBD system may monitor the 

individual parameters or components that are used as inputs for PM filter 

regeneration feedback control provided that the monitors detect all 

malfunctions that meet the criteria in sections (e)(8.2.7)(A) and (B). 

(8.3) Monitoring Conditions: 

(8.3.1) Manufacturers shall define the monitoring conditions for malfunctions 

identified in sections (e)(8.2.1) through (8.2.76) in accordance with 

sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements), with the 

exception that monitoring shall occur every time the monitoring conditions 

are met during the driving cycle in lieu of once per driving cycle as 

required in section (d)(3.1.2). For purposes of tracking and reporting as 

required in section (d)(3.2.1), all monitors used to detect malfunctions 

identified in sections (e)(8.2.1) shall be tracked separately but reported as 

a single set of values as specified in section (d)(5.2.2).

(8.3.2) Except as provided in section (e)(8.3.3), the OBD II system shall monitor 

continuously for malfunctions identified in section (e)(8.2.7) (i.e., PM filter 

feedback control).

(8.3.3) Manufacturers may request Executive Officer approval to temporarily 

disable continuous monitoring under conditions technically necessary to 

ensure robust detection of malfunctions and to avoid false passes and 

false indications of malfunctions. The Executive Officer shall approve the 

request upon determining that the manufacturer has submitted data 

and/or an engineering evaluation which demonstrate that a properly 

operating system cannot be distinguished from a malfunctioning system 

and that the disablement interval is limited only to that which is technically 

necessary.

(8.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(9) EXHAUST GAS SENSOR MONITORING 

(9.1) Requirement: 

(9.1.1) The OBD system shall monitor all exhaust gas sensors (e.g., oxygen, airfuel ratio, NOx) used for emission control system feedback (e.g., EGR 

control/feedback, SCR control/feedback, NOx adsorber control/feedback)
50

or as a monitoring device for proper output signal, activity, response rate, 

and any other parameter that can affect emissions. 

(9.1.2) For engines equipped with heated exhaust gas sensors, the OBD system 

shall monitor the heater for proper performance. 

(9.2) Malfunction Criteria: 

(9.2.1) Air-Fuel Ratio Sensors: 

(A) For sensors located upstream of the exhaust aftertreatment: 

(i) Sensor performance faults: The OBD system shall detect a malfunction 

prior to any failure or deterioration of the sensor voltage, resistance, 

impedance, current, response rate, amplitude, offset, or other 

characteristic(s) that would cause an engine's NMHC, CO, or NOx 

emissions to exceed 2.0 times any of the applicable standards or the 

engine’s PM emissions to exceed any of the applicable standards plus 

0.02 g/bhp-hr. 

(ii) Circuit faults: The OBD system shall detect malfunctions of the sensor 

caused by either a lack of circuit continuity or out-of-range values. 

(iii) Feedback faults: The OBD system shall detect a malfunction of the 

sensor when a sensor failure or deterioration causes an emission 

control system (e.g., EGR, SCR, or NOx adsorber) to stop using that 

sensor as a feedback or feed-forward input (e.g., causes default or 

open-loop operation). 

(iv) Monitoring capability: To the extent feasible, the OBD system shall 

detect a malfunction of the sensor when the sensor output voltage, 

resistance, impedance, current, amplitude, activity, offset, or other 

characteristics are no longer sufficient for use as an OBD system 

monitoring device (e.g., for catalyst, EGR, SCR, or NOx adsorber 

monitoring). 

(B) For sensors located downstream of the exhaust aftertreatment: 

(i) Sensor performance faults: 

a. For 2010 through 2012 model year engines, the OBD system shall 

detect a malfunction prior to any failure or deterioration of the 

sensor voltage, resistance, impedance, current, response rate, 

amplitude, offset, or other characteristic(s) that would cause an 

engine's NMHC emissions to exceed 2.5 times any of the 

applicable standards, cause an engine's NOx emissions to exceed 

any of the applicable standards by more than 0.3 g/bhp-hr (e.g., 

cause emissions to exceed 0.5 g/bhp-hr if the emission standard is 

0.2 g/bhp-hr) as measured from an applicable cycle emission test 

(i.e., FTP or SET), or cause an engine’s PM emissions to exceed 

(whichever is higher): 0.05 g/bhp-hr as measured from an 

applicable cycle emission test (i.e., FTP or SET); or any of the 

applicable standards by more than 0.04 g/bhp-hr (e.g., cause 

emissions to exceed 0.05 g/bhp-hr if the emission standard is 0.01 

g/bhp-hr). 

b. For 2013 and subsequent model year engines, the OBD system 

shall detect a malfunction prior to any failure or deterioration of the 

sensor voltage, resistance, impedance, current, response rate, 

amplitude, offset, or other characteristic(s) that would cause an 
51

engine's NMHC emissions to exceed 2.0 times any of the 

applicable standards, cause an engine's NOx emissions to exceed 

any of the applicable standards by more than 0.2 g/bhp-hr (e.g., 

cause emissions to exceed 0.4 g/bhp-hr if the emission standard is 

0.2 g/bhp-hr) as measured from an applicable cycle emission test 

(i.e., FTP or SET), or cause an engine's PM emissions to exceed 

(whichever is higher): 0.03 g/bhp-hr as measured from an 

applicable cycle emission test (i.e., FTP or SET); or any of the 

applicable standards by more than 0.02 g/bhp-hr (e.g., cause 

emissions to exceed 0.03 g/bhp-hr if the emission standard is 0.01 

g/bhp-hr). 

(ii) Circuit faults: The OBD system shall detect malfunctions of the sensor 

caused by either a lack of circuit continuity or out-of-range values. 

(iii) Feedback faults: The OBD system shall detect a malfunction of the 

sensor when a sensor failure or deterioration causes an emission 

control system (e.g., EGR, SCR, or NOx adsorber) to stop using that 

sensor as a feedback or feed-forward input (e.g., causes default or 

open-loop operation). 

(iv) Monitoring capability: To the extent feasible, the OBD system shall 

detect a malfunction of the sensor when the sensor output voltage, 

resistance, impedance, current, amplitude, activity, offset, or other 

characteristics are no longer sufficient for use as an OBD system 

monitoring device (e.g., for catalyst, EGR, SCR, or NOx adsorber 

monitoring). 

(9.2.2) NOx and PM sensors: 

(A) Sensor performance faults: 

(i) For 2010 through 2012 model year engines, the OBD system shall 

detect a malfunction prior to any failure or deterioration of the sensor 

voltage, resistance, impedance, current, response rate, amplitude, 

offset, or other characteristic(s) that would cause an engine's NOx 

emissions to exceed any of the applicable standards by more than 

0.34 g/bhp-hr (e.g., cause emissions to exceed 0.56 g/bhp-hr if the 

emission standard is 0.2 g/bhp-hr) as measured from an applicable 

cycle emission test (i.e., FTP or SET), or cause an engine's PM 

emissions to exceed (whichever is higher): 0.05 g/bhp-hr as measured 

from an applicable cycle emission test (i.e., FTP or SET); or any of the 

applicable standards by more than 0.04 g/bhp-hr (e.g., cause 

emissions to exceed 0.05 g/bhp-hr if the emission standard is 0.01 

g/bhp-hr). 

(ii) For 2013 and subsequent model year engines, the OBD system shall 

detect a malfunction prior to any failure or deterioration of the sensor 

voltage, resistance, impedance, current, response rate, amplitude, 

offset, or other characteristic(s) that would cause an engine's NOx 

emissions to exceed any of the applicable standards by more than 0.2 

g/bhp-hr (e.g., cause emissions to exceed 0.4 g/bhp-hr if the emission 

standard is 0.2 g/bhp-hr) as measured from an applicable cycle 

emission test (i.e., FTP or SET), or cause an engine's PM emissions to 

exceed (whichever is higher): 0.03 g/bhp-hr as measured from an 
52

applicable cycle emission test (i.e., FTP or SET); or any of the 

applicable standards by more than 0.02 g/bhp-hr (e.g., cause 

emissions to exceed 0.03 g/bhp-hr if the emission standard is 0.01 

g/bhp-hr). 

(B) Circuit faults: The OBD system shall detect malfunctions of the sensor 

caused by either a lack of circuit continuity or out-of-range values. 

(C) Feedback faults: The OBD system shall detect a malfunction of the 

sensor when a sensor failure or deterioration causes an emission control 

system (e.g., EGR, SCR, or NOx adsorber) to stop using that sensor as a 

feedback or feed-forward input (e.g., causes default or open-loop 

operation). 

(D) Monitoring capability: To the extent feasible, the OBD system shall detect 

a malfunction of the sensor when the sensor output voltage, resistance, 

impedance, current, amplitude, activity, offset, or other characteristics are 

no longer sufficient for use as an OBD system monitoring device (e.g., for 

catalyst, EGR, PM filter, SCR, or NOx adsorber monitoring). 

(9.2.3) Other exhaust gas sensors: 

(A) For other exhaust gas sensors, the manufacturer shall submit a 

monitoring plan to the Executive Officer for approval. The Executive 

Officer shall approve the request upon determining that the manufacturer 

has submitted data and an engineering evaluation that demonstrate that 

the monitoring plan is as reliable and effective as the monitoring plan 

required for air-fuel ratio sensors, and NOx sensors, and PM sensors

under sections (e)(9.2.1) and (e)(9.2.2). 

(9.2.4) Sensor Heaters: 

(A) The OBD system shall detect a malfunction of the heater performance 

when the current or voltage drop in the heater circuit is no longer within 

the manufacturer's specified limits for normal operation (i.e., within the 

criteria required to be met by the component vendor for heater circuit 

performance at high mileage). Subject to Executive Officer approval, 

other malfunction criteria for heater performance malfunctions may be 

used upon the Executive Officer determining that the manufacturer has 

submitted data and/or an engineering evaluation that demonstrate the 

monitoring reliability and timeliness to be equivalent to the stated criteria 

in section (e)(9.2.4)(A). 

(B) The OBD system shall detect malfunctions of the heater circuit including 

open or short circuits that conflict with the commanded state of the heater 

(e.g., shorted to 12 Volts when commanded to 0 Volts (ground)). 

(9.3) Monitoring Conditions: 

(9.3.1) Exhaust Gas Sensors 

(A) Manufacturers shall define the monitoring conditions for malfunctions 

identified in sections (e)(9.2.1)(A)(i), (9.2.1)(B)(i), and (9.2.2)(A) (e.g., 

sensor performance faults) in accordance with sections (d)(3.1) and 

(d)(3.2) (i.e., minimum ratio requirements). For purposes of tracking and 

reporting as required in section (d)(3.2.1), all monitors used to detect 

malfunctions identified in sections (e)(9.2.1)(A)(i), (9.2.1)(B)(i), and 

(9.2.2)(A) shall be tracked separately but reported as a single set of 

values as specified in section (d)(5.2.2). 
53

(B) Manufacturers shall define the monitoring conditions for malfunctions 

identified in sections (9.2.1)(A)(iv), (9.2.1)(B)(iv), and (9.2.2)(D) (e.g., 

monitoring capability) in accordance with sections (d)(3.1) and (d)(3.2) 

(i.e., minimum ratio requirements) with the exception that monitoring shall 

occur every time the monitoring conditions are met during the driving cycle 

in lieu of once per driving cycle as required in section (d)(3.1.2). 

(C) Except as provided in section (e)(9.3.1)(D), monitoring for malfunctions 

identified in sections (e)(9.2.1)(A)(ii), (9.2.1)(A)(iii), (9.2.1)(B)(ii), 

(9.2.1)(B)(iii), (9.2.2)(B), and (9.2.2)(C) (i.e., circuit continuity, and openloop malfunctions) shall be conducted continuously.

(D) A manufacturer may request Executive Officer approval to disable 

continuous exhaust gas sensor monitoring when an exhaust gas sensor 

malfunction cannot be distinguished from other effects (e.g., disable outof-range low monitoring during fuel cut conditions). The Executive Officer 

shall approve the disablement upon determining that the manufacturer 

has submitted test data and/or documentation that demonstrate a properly 

functioning sensor cannot be distinguished from a malfunctioning sensor 

and that the disablement interval is limited only to that necessary for 

avoiding false detection. 

(9.3.2) Sensor Heaters 

(A) Manufacturers shall define monitoring conditions for malfunctions 

identified in section (e)(9.2.4)(A) (i.e., sensor heater performance) in 

accordance with sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio

requirements). 

(B) Monitoring for malfunctions identified in section (e)(9.2.4)(B) (i.e., circuit 

malfunctions) shall be conducted continuously. 

(9.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(10) VARIABLE VALVE TIMING AND/OR CONTROL (VVT) SYSTEM 

MONITORING 

(10.1) Requirement: The OBD system shall monitor the VVT system on engines 

so-equipped for target error and slow response malfunctions. The individual 

electronic components (e.g., actuators, valves, sensors) that are used in the 

VVT system shall be monitored in accordance with the comprehensive 

components requirements in section (g)(3). 

(10.2) Malfunction Criteria: 

(10.2.1) Target Error: The OBD system shall detect a malfunction prior to any 

failure or deterioration in the capability of the VVT system to achieve the 

commanded valve timing and/or control within a crank angle and/or lift 

tolerance that would cause an engine's NHMC, NOx, or CO emissions to 

exceed 2.0 times any of the applicable standards or an engine’s PM 

emissions to exceed a threshold of the applicable standard plus 0.02 

g/bhp-hr. 

(10.2.2) Slow Response: The OBD system shall detect a malfunction prior to any 

failure or deterioration in the capability of the VVT system to achieve the 

commanded valve timing and/or control within a manufacturer-specified 

time that would cause an engine's NHMC, NOx, or CO emissions to 
54

exceed 2.0 times any of the applicable standards or an engine’s PM 

emissions to exceed a threshold of the applicable standard plus 0.02 

g/bhp-hr. 

(10.2.3) For engines in which no failure or deterioration of the VVT system could 

result in an engine’s emissions exceeding the thresholds of sections 

(e)(10.2.1) or (10.2.2), the OBD system shall detect a malfunction of the 

VVT system when proper functional response of the system to computer 

commands does not occur. 

(10.3) Monitoring Conditions: Manufacturers shall define the monitoring conditions 

for VVT system malfunctions identified in section (e)(10.2) in accordance with 

sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements), with the 

exception that monitoring shall occur every time the monitoring conditions are 

met during the driving cycle in lieu of once per driving cycle as required in 

section (d)(3.1.2). For purposes of tracking and reporting as required in 

section (d)(3.2.1), all monitors used to detect malfunctions identified in 

section (e)(10.2) shall be tracked separately but reported as a single set of 

values as specified in section (d)(5.2.2). 

(10.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(11) COLD START EMISSION REDUCTION STRATEGY MONITORING

(11.1) Requirement:

(11.1.1) For all 2013 and subsequent model year engines, if an engine

incorporates a specific engine control strategy to reduce cold start 

emissions, the OBD system shall monitor the system to verify the strategy 

achieves the desired effect (e.g., to achieve accelerated catalyst light-off 

temperature) and monitor the commanded elements/components for 

proper function (e.g., injection timing, increased engine idle speed, 

increased engine load via intake or exhaust throttle activation) while the 

control strategy is active to ensure proper operation of the control 

strategy.

(11.2) Malfunction Criteria: The OBD system shall, to the extent feasible, detect a 

malfunction if either of the following occurs:

(11.2.1) Any single commanded element/component does not properly respond 

to the commanded action while the cold start strategy is active. For 

purposes of this section, “properly respond” is defined as when the 

element responds:

(A) by a robustly detectable amount by the monitor; and 

(B) in the direction of the desired command; and

(C) above and beyond what the element/component would achieve on startup without the cold start strategy active (e.g., if the cold start strategy 

commands a higher idle engine speed, a fault must be detected if there is 

no detectable amount of engine speed increase above what the system 

would achieve without the cold start strategy active);

(11.2.2) Any failure or deterioration of the cold start emission reduction control 

strategy that would cause an engine’s NMHC, NOx, or CO emissions to 

exceed 2.0 times the applicable standards or the engine’s PM emissions

to exceed the applicable standard plus 0.02 g/bhp-hr.
55

(11.2.3) For section (e)(11.2.2), to the extent feasible (without adding hardware 

for this purpose), the OBD system shall monitor the ability of the system to 

achieve the desired effect (e.g., strategies used to accelerate catalyst 

light-off by increasing catalyst inlet temperature shall verify the catalyst 

inlet temperature actually achieves the desired temperatures within an 

Executive Officer approved time interval after starting the engine) for 

failures that cause emissions to exceed the applicable emission levels 

specified in section (e)(11.2.2). For strategies where it is not feasible to 

be monitored as a system, the OBD system shall monitor the individual

elements/components (e.g., increased engine speed, increased engine 

load from restricting an exhaust throttle) for failures that cause emissions 

to exceed the applicable emission levels specified in section (e)(11.2.2).

(11.3) Monitoring Conditions: Manufacturers shall define the monitoring conditions 

for malfunctions identified in section (e)(11.2) in accordance with sections 

(d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements).

(11.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2).

(f) MONITORING REQUIREMENTS FOR GASOLINE/SPARK-IGNITED ENGINES 

(1) FUEL SYSTEM MONITORING 

(1.1) Requirement: The OBD system shall monitor the fuel delivery system to 

determine its ability to provide compliance with emission standards. 

(1.2) Malfunction Criteria: 

(1.2.1) The OBD system shall detect a malfunction of the fuel delivery system 

(including feedback control based on a secondary oxygen sensor) when:

(A) tThe fuel delivery system is unable to maintain an engine's emissions at 

or below 1.5 times the applicable standards; or.

(B) If equipped, the feedback control based on a secondary oxygen or 

exhaust gas sensor is unable to maintain a vehicle’s emissions (except as 

a result of a malfunction specified in section (f)(1.2.1)(C)) at or below 1.5 

times any of the applicable standards; or

(C) Except as required in section (f)(1.2.6), for 2014 and subsequent model 

year vehicles, an air-fuel ratio cylinder imbalance (e.g., the air-fuel ratio in 

one or more cylinders is different than the other cylinders due to a cylinder 

specific malfunction such as an intake manifold leak at a particular 

cylinder, fuel injector problem, an individual cylinder EGR runner flow 

delivery problem, an individual variable cam lift malfunction such that an 

individual cylinder is operating on the wrong cam lift profile, or other 

similar problems) occurs in one or more cylinders such that the fuel 

delivery system is unable to maintain a vehicle’s emissions at or below: 

3.0 times the applicable standards for the 2014 through 2016 model 

years; and 1.5 times the applicable FTP standards for all 2017 and 

subsequent model year vehicles. 

(1.2.2) Except as provided for in section (f)(1.2.3) below, if the engine is equipped 

with adaptive feedback control, the OBD system shall detect a malfunction 

when the adaptive feedback control has used up all of the adjustment 

allowed by the manufacturer. 
56

(1.2.3) If the engine is equipped with feedback control that is based on a 

secondary oxygen (or equivalent) sensor, the OBD system is not required 

to detect a malfunction of the fuel system solely when the feedback 

control based on a secondary oxygen sensor has used up all of the 

adjustment allowed by the manufacturer. However, if a failure or 

deterioration results in engine emissions that exceed the malfunction 

criteria in section (f)(1.2.1)(B), the OBD system is required to detect a 

malfunction. 

(1.2.4) The OBD system shall detect a malfunction whenever the fuel control 

system fails to enter closed-loop operation within an Executive Officerapproved time interval after engine start. Executive Officer approval of 

the time interval shall be granted upon determining that the data and/or 

engineering evaluation submitted by the manufacturer supports the 

specified times. 

(1.2.5) For engines that employ engine shutoff strategies that do not require the 

vehicle operator to restart the engine to continue driving (e.g., hybrid bus 

with engine shutoff at idle), the OBD system shall detect whenever the 

fuel control system fails to enter closed-loop operation within an Executive 

Officer-approved time interval after an engine restart. Executive Officer 

approval of the time interval shall be granted upon determining that the 

data and/or engineering evaluation submitted by the manufacturer 

supports the specified times.

(1.2.5)Manufacturers may adjust the malfunction criteria and/or monitoring 

conditions to compensate for changes in altitude, for temporary 

introduction of large amounts of purge vapor, or for other similar 

identifiable operating conditions when they occur.

(1.2.6) Notwithstanding the phase-in specified in section (f)(1.2.1)(C), if a vehicle 

is equipped with separate EGR flow delivery passageways (internal or 

external) that deliver EGR flow to individual cylinders (e.g., an EGR 

system with individual delivery pipes to each cylinder), the OBD system 

shall monitor the fuel delivery system for malfunctions specified in section 

(f)(1.2.1)(C) on all 2014 and subsequent model year vehicles so 

equipped.

(1.3) Monitoring Conditions: 

(1.3.1) Except as provided in section (f)(1.3.5), Tthe OBD system shall monitor 

fuel system shall be monitored continuously for the presence of a 

malfunctions identified in sections (f)(1.2.1)(A) and (B) (e.g., fuel delivery 

system, secondary feedback control). 

(1.3.2) Manufacturers shall define monitoring conditions for malfunctions 

identified in section (f)(1.2.1)(C) (i.e., air-fuel ratio cylinder imbalance 

malfunctions) in accordance with sections (d)(3.1) and (d)(3.2) (i.e., 

minimum ratio requirements). 

(1.3.3) Manufacturers shall define monitoring conditions for malfunctions 

identified in section (f)(1.2.4) in accordance with sections (d)(3.1).

(1.3.4) Manufacturers shall define monitoring conditions for malfunctions 

identified in section (f)(1.2.5) in accordance with sections (d)(3.1) with the 

exception that monitoring shall occur every time the monitoring conditions 
57

are met during the driving cycle in lieu of once per driving cycle as 

required in section (d)(3.1.2).

(1.3.5) Manufacturers may request Executive Officer approval to temporarily 

disable continuous monitoring under conditions technically necessary to 

ensure robust detection of malfunctions and to avoid false passes and 

false indications of malfunctions (e.g., for temporary introduction of large 

amounts of purge vapor). The Executive Officer shall approve the request 

upon determining that the manufacturer has submitted data and/or an 

engineering evaluation which demonstrate that a properly operating 

system cannot be distinguished from a malfunctioning system and that the 

disablement interval is limited only to that which is technically necessary.

(1.4) MIL Illumination and Fault Code Storage: For malfunctions described under 

section (f)(1.2.1)(C) (i.e., air-fuel ratio cylinder imbalance malfunctions), 

general requirements for MIL illumination and fault code storage are set forth 

in section (d)(2). For all other fuel system malfunctions, the MIL illumination 

and fault code storage requirements are set forth in sections (f)(1.4.1) 

through (1.4.6) below.

(1.4.1) A pending fault code shall be stored immediately upon the fuel system 

exceeding the malfunction criteria established pursuant to section (f)(1.2). 

(1.4.2) Except as provided below, if a pending fault code is stored, the OBD 

system shall immediately illuminate the MIL and store a confirmed fault 

code if a malfunction is again detected during either of the following two 

events: (a) the driving cycle immediately following the storage of the 

pending fault code, regardless of the conditions encountered during the 

driving cycle; or (b) on the next driving cycle in which similar conditions 

(see section (c)) to those that occurred when the pending fault code was 

stored are encountered. 

(1.4.3) The pending fault code may be erased at the end of the next driving cycle 

in which similar conditions have been encountered without an exceedance 

of the specified fuel system malfunction criteria. The pending code may 

also be erased if similar conditions are not encountered during the 80 

driving cycles immediately after the initial detection of a malfunction for 

which the pending code was set. 

(1.4.4) Storage of freeze frame conditions. 

(A) The OBD system shall store and erase freeze frame conditions either in 

conjunction with storing and erasing a pending fault code or in conjunction 

with storing and erasing a confirmed fault code. 

(B) If freeze frame conditions are stored for a malfunction other than a misfire 

(see section (f)(2)) or fuel system malfunction when a fault code is stored 

as specified in section (f)(1.4.1) or (f)(1.4.2) above, the stored freeze 

frame information shall be replaced with freeze frame information 

regarding the fuel system malfunction. 

(1.4.5) Storage of fuel system conditions for determining similar conditions of 

operation. 

(A) Upon detection of a fuel system malfunction under section (f)(1.2), the 

OBD system shall store the engine speed, load, and warm-up status of 

the first fuel system malfunction that resulted in the storage of the pending 

fault code.
58

(B) For fuel system faults detected using feedback control that is based on a 

secondary oxygen (or equivalent) sensor, the manufacturer may request 

Executive Officer approval to use an alternate definition of similar 

conditions in lieu of the definition specified in section (c). The Executive 

Officer shall approve the alternate definition upon the manufacturer 

providing data or analysis demonstrating that the alternate definition 

provides for equivalent robustness in detection of fuel system faults that 

vary in severity depending on engine speed, load, and/or warm-up status.

(1.4.6) Extinguishing the MIL. The MIL may be extinguished after three 

sequential driving cycles in which similar conditions have been 

encountered without a malfunction of the fuel system. 

(2) MISFIRE MONITORING 

(2.1) Requirement: 

(2.1.1) The OBD system shall monitor the engine for misfire causing catalyst 

damage and misfire causing excess emissions. 

(2.1.2) The OBD system shall identify the specific cylinder that is experiencing 

misfire. Manufacturers may request Executive Officer approval to store a 

general misfire fault code instead of a cylinder specific fault code under 

certain operating conditions. The Executive Officer shall approve the 

request upon determining that the manufacturer has submitted data 

and/or an engineering evaluation that demonstrate that the misfiring 

cylinder cannot be reliably identified when the conditions occur. 

(2.1.3) If more than one cylinder is misfiring, a separate fault code shall be stored 

indicating that multiple cylinders are misfiring except as allowed below. 

When identifying multiple cylinder misfire, the OBD system is not required 

to also identify each of the misfiring cylinders individually through separate 

fault codes. If more than 90 percent of the detected misfires occur in a 

single cylinder, the OBD system may elect to store the appropriate fault 

code indicating the specific misfiring cylinder in lieu of the multiple cylinder 

misfire fault code. If, however, two or more cylinders individually have 

more than 10 percent of the total number of detected misfires, a multiple 

cylinder fault code must be stored. 

(2.2) Malfunction Criteria: The OBD system shall detect a misfire malfunction 

pursuant to the following: 

(2.2.1) Misfire causing catalyst damage:

(A) Manufacturers shall determine the percentage of misfire evaluated in 200 

revolution increments for each engine speed and load condition that 

would result in a temperature that causes catalyst damage. The 

manufacturer shall submit documentation to support this percentage of 

misfire as required in section (j)(2.5). For every engine speed and load 

condition that this percentage of misfire is determined to be lower than 

five percent, the manufacturer may set the malfunction criteria at five 

percent.

(B) Subject to Executive Officer approval, a manufacturer may employ a 

longer interval than 200 revolutions but only for determining, on a given 

driving cycle, the first misfire exceedance as provided in section 

(f)(2.4.1)(A) below. Executive Officer approval shall be granted upon 
59

determining that the manufacturer has submitted data and/or an 

engineering evaluation that demonstrate that catalyst damage would not 

occur due to unacceptably high catalyst temperatures before the interval 

has elapsed.

(C) A misfire malfunction shall be detected if the percentage of misfire 

established in section (f)(2.2.1)(A) is exceeded. For multiple cylinder 

misfire situations that result in a misfire rate greater than or equal to 50 

percent, the OBD system shall only be required to detect a misfire 

malfunction for situations that are caused by a single component failure.

(D) For purposes of establishing the temperature at which catalyst damage 

occurs as required in section (f)(2.2.1)(A), manufacturers may not define 

catalyst damage at a temperature more severe than what the catalyst 

system could be operated at for 10 consecutive hours and still meet the 

applicable standards. 

(2.2.2) Misfire causing emissions to exceed 1.5 times the applicable standards: 

(A) Manufacturers shall determine the percentage of misfire evaluated in 

1000 revolution increments that would cause emissions from an emission 

durability demonstration engine to exceed 1.5 times any of the applicable 

standards if the percentage of misfire were present from the beginning of 

the test. To establish this percentage of misfire, the manufacturer shall 

utilize misfire events occurring at equally spaced, complete engine cycle 

intervals, across randomly selected cylinders throughout each 1000-

revolution increment. If this percentage of misfire is determined to be 

lower than one percent, the manufacturer may set the malfunction criteria 

at one percent. 

(B) Subject to Executive Officer approval, a manufacturer may employ other 

revolution increments. The Executive Officer shall grant approval upon 

determining that the manufacturer has demonstrated that the strategy 

would be equally effective and timely in detecting misfire. 

(C) A malfunction shall be detected if the percentage of misfire established in 

section (f)(2.2.2)(A) is exceeded regardless of the pattern of misfire 

events (e.g., random, equally spaced, continuous). 

(2.3) Monitoring Conditions: 

(2.3.1) The OBD system shall continuously monitor for misfire under the following 

conditions: 

(A) From no later than the end of the second crankshaft revolution after 

engine start, 

(B) While under positive torque conditions Dduring the rise time and settling 

time for engine speed to reach the desired idle engine speed at engine 

start-up (i.e., “flare-up” and “flare-down”), and 

(C) Under all positive torque engine speeds and load conditions except within 

the following range: the engine operating region bound by the positive 

torque line (i.e., engine load with the transmission in neutral), and the two 

following engine operating points: an engine speed of 3000 rpm with the 

engine load at the positive torque line, and the redline engine speed 

(defined in section (c)) with the engine's manifold vacuum at four inches of 

mercury lower than that at the positive torque line. 
60

(2.3.2) If a monitoring system cannot detect all misfire patterns under all required 

engine speed and load conditions as required in section (f)(2.3.1) above, 

the manufacturer may request Executive Officer approval to accept the 

monitoring system. In evaluating the manufacturer’s request, the 

Executive Officer shall consider the following factors: the magnitude of the 

region(s) in which misfire detection is limited, the degree to which misfire 

detection is limited in the region(s) (i.e., the probability of detection of 

misfire events), the frequency with which said region(s) are expected to be 

encountered in-use, the type of misfire patterns for which misfire detection 

is troublesome, and demonstration that the monitoring technology 

employed is not inherently incapable of detecting misfire under required 

conditions (i.e., compliance can be achieved on other engines). The 

evaluation shall be based on the following misfire patterns: equally spaced 

misfire occurring on randomly selected cylinders, single cylinder 

continuous misfire, and paired cylinder (cylinders firing at the same crank 

angle) continuous misfire. 

(2.3.3) A manufacturer may request Executive Officer approval of a monitoring 

system that has reduced misfire detection capability during the portion of 

the first 1000 revolutions after engine start that a cold start emission 

reduction strategy that reduces engine torque (e.g., spark retard 

strategies) is active. The Executive Officer shall approve the request 

upon determining that the manufacturer has demonstrated that the 

probability of detection is greater than or equal to 75 percent during the 

worst case condition (i.e., lowest generated torque) for a vehicle operated 

continuously at idle (park/neutral idle) on a cold start between 50 and 86 

degrees Fahrenheit and that the technology cannot reliably detect a 

higher percentage of the misfire events during the conditions. 

(2.3.4) A manufacturer may request Executive Officer approval to disable misfire 

monitoring or employ an alternate malfunction criterion when misfire 

cannot be distinguished from other effects. 

(A) Upon determining that the manufacturer has presented documentation 

that demonstrates the disablement interval or period of use of an alternate 

malfunction criterion is limited only to that necessary for avoiding false 

detection, the Executive Officer shall approve the disablement or use of 

the alternate malfunction criterion for conditions involving: 

(i) rough road, 

(ii) fuel cut, 

(iii) gear changes for manual transmission vehicles, 

(iv) traction control or other vehicle stability control activation such as antilock braking or other engine torque modifications to enhance vehicle 

stability, 

(v) off-board control or intrusive activation of vehicle components or 

diagnostics during service or assembly plant testing, 

(vi) portions of intrusive evaporative system or EGR diagnostics that can 

significantly affect engine stability (i.e., while the purge valve is open 

during the vacuum pull-down of a evaporative system leak check but 

not while the purge valve is closed and the evaporative system is 
61

sealed or while an EGR diagnostic causes the EGR valve to be 

intrusively cycled on and off during positive torque conditions), or 

(vii) engine speed, load, or torque transients due to throttle movements 

more rapid than occurs over the FTP cycle for the worst case engine 

within each engine family. 

(B) Additionally, the Executive Officer will approve a manufacturer's request 

in accordance with sections (g)(5.3), (g)(5.4), and (g)(5.6) to disable 

misfire monitoring when the fuel level is 15 percent or less of the nominal 

capacity of the fuel tank, when PTO units are active, or while engine 

coolant temperature is below 20 degrees Fahrenheit. The Executive 

Officer will approve a request to continue disablement on engine starts 

when engine coolant temperature is below 20 degrees Fahrenheit at 

engine start until engine coolant temperature exceeds 70 degrees 

Fahrenheit. 

(C) In general, the Executive Officer shall not approve disablement for 

conditions involving normal air conditioning compressor cycling from onto-off or off-to-on, automatic transmission gear shifts (except for shifts 

occurring during wide open throttle operation), transitions from idle to offidle, normal engine speed or load changes that occur during the engine 

speed rise time and settling time (i.e., “flare-up” and “flare-down”) 

immediately after engine starting without any vehicle operator-induced 

actions (e.g., throttle stabs), or excess acceleration (except for 

acceleration rates that exceed the maximum acceleration rate obtainable 

at wide open throttle while the vehicle is in gear due to abnormal 

conditions such as slipping of a clutch). 

(D) The Executive Officer may approve misfire monitoring disablement or use 

of an alternate malfunction criterion for any other condition on a case by 

case basis upon determining that the manufacturer has demonstrated that 

the request is based on an unusual or unforeseen circumstance and that 

it is applying the best available computer and monitoring technology. 

(2.3.5) For engines with more than eight cylinders that cannot meet the 

requirements of section (f)(2.3.1), a manufacturer may request Executive 

Officer approval to use alternative misfire monitoring conditions. The 

Executive Officer shall approve the request upon determining that the 

manufacturer has submitted data and/or an engineering evaluation that 

demonstrate that misfire detection throughout the required operating 

region cannot be achieved when employing proven monitoring technology 

(i.e., a technology that provides for compliance with these requirements 

on other engines) and provided misfire is detected to the fullest extent 

permitted by the technology. However, the Executive Officer may not 

grant the request if the misfire detection system is unable to monitor 

during all positive torque operating conditions encountered during an FTP 

cycle. 

(2.3.6) For engines that employ engine shutoff strategies that do not require the 

vehicle operator to restart the engine to continue driving (e.g., hybrid bus 

with engine shutoff at idle), the OBD system shall monitor for misfire from 

no later than the end of the second crankshaft revolution after each 

engine restart.
62

(2.4) MIL Illumination and Fault Code Storage: 

(2.4.1) Misfire causing catalyst damage. Upon detection of the percentage of misfire 

specified in section (f)(2.2.1) above, the following criteria shall apply for MIL 

illumination and fault code storage: 

(A) Pending fault codes 

(i) A pending fault code shall be stored immediately if, during a single 

driving cycle, the specified percentage of misfire is exceeded three 

times when operating in the positive torque region encountered during 

an FTP cycle or is exceeded on a single occasion when operating at 

any other engine speed and load condition in the positive torque 

region defined in section (f)(2.3.1). 

(ii) Immediately after a pending fault code is stored as specified in section 

(f)(2.4.1)(A)(i) above, the MIL shall blink once per second at all times 

while misfire is occurring during the driving cycle. 

a. The MIL may be extinguished during those times when misfire is not 

occurring during the driving cycle. 

b. If, at the time a misfire malfunction occurs, the MIL is already 

illuminated for a malfunction other than misfire, the MIL shall blink 

as previously specified in section (f)(2.4.1)(A)(ii) while misfire is 

occurring. If misfiring ceases, the MIL shall stop blinking but 

remain illuminated as required by the other malfunction. 

(B) Confirmed fault codes 

(i) If a pending fault code for exceeding the percentage of misfire set forth 

in section (f)(2.2.1) is stored, the OBD system shall immediately store 

a confirmed fault code if the percentage of misfire specified in section 

(f)(2.2.1) is again exceeded one or more times during either: (a) the 

driving cycle immediately following the storage of the pending fault 

code, regardless of the conditions encountered during the driving 

cycle; or (b) on the next driving cycle in which similar conditions (see 

section (c)) to the engine conditions that occurred when the pending 

fault code was stored are encountered. 

(ii) If a pending fault code for exceeding the percentage of misfire set forth 

in section (f)(2.2.2) is stored from a previous driving cycle, the OBD 

system shall immediately store a confirmed fault code if the 

percentage of misfire specified in section (f)(2.2.1) is exceeded one or 

more times regardless of the conditions encountered. 

(iii) Upon storage of a confirmed fault code, the MIL shall blink as 

specified in subparagraph (f)(2.4.1)(A)(ii) above as long as misfire is 

occurring and the MIL shall remain continuously illuminated if the 

misfiring ceases. 

(C) Erasure of pending fault codes 

Pending fault codes shall be erased at the end of the next driving cycle in 

which similar conditions to the engine conditions that occurred when the 

pending fault code was stored have been encountered without any 

exceedance of the specified percentage of misfire. The pending code 

may also be erased if similar driving conditions are not encountered 

during the next 80 driving cycles subsequent to the initial detection of a 

malfunction. 
63

(D) Exemptions for engines with fuel shutoff and default fuel control. 

Notwithstanding sections (f)(2.4.1)(A) and (B) above, in engines that 

provide for fuel shutoff and default fuel control to prevent over fueling 

during catalyst damage misfire conditions, the MIL is not required to blink. 

 Instead, the MIL may illuminate continuously in accordance with the 

requirements for continuous MIL illumination in sections (f)(2.4.1)(B)(iii) 

above upon detection of misfire, provided that the fuel shutoff and default 

control are activated as soon as misfire is detected. Fuel shutoff and 

default fuel control may be deactivated only to permit fueling outside of 

the misfire range. Manufacturers may also periodically, but not more than 

once every 30 seconds, deactivate fuel shutoff and default fuel control to 

determine if the specified catalyst damage percentage of misfire is still 

being exceeded. Normal fueling and fuel control may be resumed if the 

specified catalyst damage percentage of misfire is no longer being 

exceeded. 

(E) Manufacturers may request Executive Officer approval of strategies that 

continuously illuminate the MIL in lieu of blinking the MIL during extreme 

catalyst damage misfire conditions (i.e., catalyst damage misfire occurring 

at all engine speeds and loads). Executive Officer approval shall be 

granted upon determining that the manufacturer employs the strategy only 

when catalyst damage misfire levels cannot be avoided during reasonable 

driving conditions and the manufacturer has demonstrated that the 

strategy will encourage operation of the vehicle in conditions that will 

minimize catalyst damage (e.g., at low engine speeds and loads). 

(2.4.2) Misfire causing emissions to exceed 1.5 times the FTP standards. Upon 

detection of the percentage of misfire specified in section (f)(2.2.2), the 

following criteria shall apply for MIL illumination and fault code storage: 

(A) Misfire within the first 1000 revolutions after engine start. 

(i) A pending fault code shall be stored no later than after the first 

exceedance of the specified percentage of misfire during a single 

driving cycle if the exceedance occurs within the first 1000 revolutions 

after engine start (defined in section (c)) during which misfire detection 

is active. 

(ii) If a pending fault code is stored, the OBD system shall illuminate the 

MIL and store a confirmed fault code within 10 seconds if an 

exceedance of the specified percentage of misfire is again detected in 

the first 1000 revolutions during any subsequent driving cycle, 

regardless of the conditions encountered during the driving cycle. 

(iii) The pending fault code shall be erased at the end of the next driving 

cycle in which similar conditions to the engine conditions that occurred 

when the pending fault code was stored have been encountered 

without an exceedance of the specified percentage of misfire. The 

pending code may also be erased if similar conditions are not 

encountered during the next 80 driving cycles immediately following 

the initial detection of the malfunction. 

(B) Exceedances after the first 1000 revolutions after engine start. 
64

(i) A pending fault code shall be stored no later than after the fourth 

exceedance of the percentage of misfire specified in section (f)(2.2.2) 

during a single driving cycle. 

(ii) If a pending fault code is stored, the OBD system shall illuminate the 

MIL and store a confirmed fault code within 10 seconds if the 

percentage of misfire specified in section (f)(2.2.2) is again exceeded 

four times during: (a) the driving cycle immediately following the 

storage of the pending fault code, regardless of the conditions 

encountered during the driving cycle; or (b) on the next driving cycle in 

which similar conditions (see section (c)) to the engine conditions that 

occurred when the pending fault code was stored are encountered. 

(iii) The pending fault code may be erased at the end of the next driving 

cycle in which similar conditions to the engine conditions that occurred 

when the pending fault code was stored have been encountered 

without an exceedance of the specified percentage of misfire. The 

pending code may also be erased if similar conditions are not 

encountered during the next 80 driving cycles immediately following 

initial detection of the malfunction. 

(2.4.3) Storage of freeze frame conditions. 

(A) The OBD system shall store and erase freeze frame conditions either in 

conjunction with storing and erasing a pending fault code or in conjunction 

with storing and erasing a confirmed fault code. 

(B) If freeze frame conditions are stored for a malfunction other than a misfire 

or fuel system malfunction (see section (f)(1)) when a fault code is stored 

as specified in section (f)(2.4) above, the stored freeze frame information 

shall be replaced with freeze frame information regarding the misfire 

malfunction. 

(2.4.4) Storage of misfire conditions for similar conditions determination. Upon 

detection of misfire under sections (f)(2.4.1) or (2.4.2), the OBD system 

shall store the following engine conditions: engine speed, load, and 

warm-up status of the first misfire event that resulted in the storage of the 

pending fault code. 

(2.4.5) Extinguishing the MIL. The MIL may be extinguished after three 

sequential driving cycles in which similar conditions have been 

encountered without an exceedance of the specified percentage of 

misfire. 

(3) EXHAUST GAS RECIRCULATION (EGR) SYSTEM MONITORING 

(3.1) Requirement: The OBD system shall monitor the EGR system on engines 

so-equipped for low and high flow rate malfunctions. The individual electronic 

components (e.g., actuators, valves, sensors) that are used in the EGR 

system shall be monitored in accordance with the comprehensive component 

requirements in section (g)(3). 

(3.2) Malfunction Criteria: 

(3.2.1) The OBD system shall detect a malfunction of the EGR system prior to a 

decrease from the manufacturer's specified EGR flow rate that would 

cause an engine's emissions to exceed 1.5 times any of the applicable 

standards. For engines in which no failure or deterioration of the EGR 
65

system that causes a decrease in flow could result in an engine’s 

emissions exceeding 1.5 times any of the applicable standards, the OBD 

system shall detect a malfunction when the system has no detectable 

amount of EGR flow. 

(3.2.2) The OBD system shall detect a malfunction of the EGR system prior to an 

increase from the manufacturer's specified EGR flow rate that would 

cause an engine's emissions to exceed 1.5 times any of the applicable 

standards. For engines in which no failure or deterioration of the EGR 

system that causes an increase in flow could result in an engine’s 

emissions exceeding 1.5 times any of the applicable standards, the OBD 

system shall detect a malfunction when the system has reached its control 

limits such that it cannot reduce EGR flow. 

(3.3) Monitoring Conditions: 

(3.3.1) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (f)(3.2) (i.e., flow rate) in accordance with sections 

(d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). For purposes of 

tracking and reporting as required in section (d)(3.2.1), all monitors used 

to detect malfunctions identified in section (f)(3.2) shall be tracked 

separately but reported as a single set of values as specified in section 

(d)(5.2.2). 

(3.3.2) Manufacturers may request Executive Officer approval to temporarily 

disable the EGR system check under conditions when monitoring may not 

be reliable (e.g., when freezing may affect performance of the system). 

The Executive Officer shall approve the request upon determining that the 

manufacturer has submitted data and/or an engineering evaluation which 

demonstrate that a reliable check cannot be made when these conditions 

exist. 

(3.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(4) COLD START EMISSION REDUCTION STRATEGY MONITORING 

(4.1) Requirement: If an engine incorporates a specific engine control strategy to 

reduce cold start emissions, the OBD system shall monitor the key 

components commanded elements/components for proper function (e.g.,

increased engine idle speed, mass air flow, commanded ignition timing retard

idle air control valve), other than secondary air, while the control strategy is 

active to ensure proper operation of the control strategy. Secondary air 

systems shall be monitored under the provisions of section (f)(5). 

(4.2) Malfunction Criteria: 

(4.2.1) For 2010 through 2012 model year engines: 

(A) The OBD system shall detect a malfunction prior to any failure or 

deterioration of the individual elements/components associated with the 

cold start emission reduction control strategy that would cause an 

engine’s emissions to exceed 1.5 times the applicable standards. 

Manufacturers shall: 

(A)(i) Establish the malfunction criteria based on data from one or more 

representative engine(s). 
66

(B)(ii) Provide an engineering evaluation for establishing the malfunction 

criteria for the remainder of the manufacturer’s product line. The 

Executive Officer shall waive the evaluation requirement each year if, 

in the judgment of the Executive Officer, technological changes do not 

affect the previously determined malfunction criteria. 

(4.2.2)(B) For components where no failure or deterioration of the 

element/component used for the cold start emission reduction strategy 

could result in an engine’s emissions exceeding 1.5 times the applicable 

standards, the individual element/component shall be monitored for 

proper functional response in accordance with the malfunction criteria in 

section (g)(3.2) while the control strategy is active. 

(4.2.2) For 2013 and subsequent model year engines, the OBD system shall, to 

the extent feasible, detect a malfunction if either of the following occurs:

(A) Any single commanded element/component does not properly respond to 

the commanded action while the cold start strategy is active. For 

elements/components involving spark timing (e.g., retarded spark timing), 

the monitor may verify final commanded spark timing in lieu of verifying 

actual delivered spark timing. For purposes of this section, “properly 

respond” is defined as when the element responds:

(i) by a robustly detectable amount; and 

(ii) in the direction of the desired command; and

(iii) above and beyond what the element/component would achieve on 

start-up without the cold start strategy active (e.g., if the cold start 

strategy commands a higher idle engine speed, a fault must be 

detected if there is no detectable amount of engine speed increase 

above what the system would achieve without the cold start strategy 

active);

(B) Any failure or deterioration of the cold start emission reduction control 

strategy that would cause an engine’s emissions to be equal to or above

1.5 times the applicable standards. For this requirement, the OBD 

system shall either monitor the combined effect of the 

elements/components of the system as a whole (e.g., measuring air flow 

and modeling overall heat into the exhaust) or the individual

elements/components (e.g., increased engine speed, commanded final 

spark timing) for failures that cause engine emissions to exceed 1.5 times 

the applicable standards.

(4.3) Monitoring Conditions: Manufacturers shall define the monitoring conditions 

for malfunctions identified in section (f)(4.2) in accordance with sections 

(d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). 

(4.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(5) SECONDARY AIR SYSTEM MONITORING 

(5.1) Requirement: 

(5.1.1) The OBD system on engines equipped with any form of secondary air 

delivery system shall monitor the proper functioning of the secondary air 

delivery system including all air switching valve(s). The individual 

electronic components (e.g., actuators, valves, sensors) in the secondary 
67

air system shall be monitored in accordance with the comprehensive 

component requirements in section (g)(3). 

(5.1.2) For purposes of section (f)(5), “air flow” is defined as the air flow delivered 

by the secondary air system to the exhaust system. For engines using 

secondary air systems with multiple air flow paths/distribution points, the 

air flow to each bank (i.e., a group of cylinders that share a common 

exhaust manifold, catalyst, and control sensor) shall be monitored in 

accordance with the malfunction criteria in section (f)(5.2) unless complete 

blocking of air delivery to one bank does not cause a measurable increase 

in emissions. 

(5.1.3) For purposes of section (f)(5), “normal operation” is defined as the 

condition when the secondary air system is activated during catalyst 

and/or engine warm-up following engine start. “Normal operation” does 

not include the condition when the secondary air system is intrusively 

turned on solely for the purpose of monitoring. 

(5.2) Malfunction Criteria: 

(5.2.1) Except as provided in section (f)(5.2.3), the OBD system shall detect a 

secondary air system malfunction prior to a decrease from the 

manufacturer's specified air flow during normal operation that would 

cause an engine's emissions to exceed 1.5 times any of the applicable 

standards. 

(5.2.2) Except as provided in section (f)(5.2.3), the OBD system shall detect a 

secondary air system malfunction prior to an increase from the 

manufacturer's specified air flow during normal operation that would 

cause an engine's emissions to exceed 1.5 times any of the applicable 

standards. 

(5.2.3) For engines in which no deterioration or failure of the secondary air 

system would result in an engine’s emissions exceeding 1.5 times any of 

the applicable standards, the OBD system shall detect a malfunction 

when no detectable amount of air flow is delivered during normal 

operation of the secondary air system. 

(5.3) Monitoring Conditions: 

(5.3.1) Manufacturers shall define the monitoring conditions in accordance with 

sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). For 

purposes of tracking and reporting as required in section (d)(3.2.1), all 

monitors used to detect malfunctions identified in section (f)(5.2) during 

normal operation of the secondary air system shall be tracked separately 

but reported as a single set of values as specified in section (d)(5.2.2). 

(5.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(6) CATALYST MONITORING 

(6.1) Requirement: The OBD system shall monitor the catalyst system for proper 

conversion capability. 

(6.2) Malfunction Criteria: 

(6.2.1) The OBD system shall detect a catalyst system malfunction when the 

catalyst system’s conversion capability decreases to the point that any of 

the following occurs: 
68

(A) Non-Methane Hydrocarbon (NMHC) emissions exceed 1.75 times the 

applicable standards to which the engine has been certified. 

(B) The average FTP test NMHC conversion efficiency of the monitored 

portion of the catalyst system falls below 50 percent (i.e., the cumulative 

NMHC emissions measured at the outlet of the monitored catalyst(s) are 

more than 50 percent of the cumulative engine-out emissions measured 

at the inlet of the catalyst(s)). With Executive Officer approval, 

manufacturers may use a conversion efficiency malfunction criteria of less 

than 50 percent if the catalyst system is designed such that the monitored 

portion of the catalyst system must be replaced along with an adjacent 

portion of the catalyst system sufficient to ensure that the total portion 

replaced will meet the 50 percent conversion efficiency criteria. Executive 

Officer approval shall be based on data and/or engineering evaluation 

demonstrating the conversion efficiency of the monitored portion and the 

total portion designed to be replaced, and the likelihood of the catalyst 

system design to ensure replacement of the monitored and adjacent 

portions of the catalyst system. 

(C) Oxides of nitrogen (NOx) emissions exceed 1.75 times the applicable 

NOx standard to which the engine has been certified. 

(6.2.2) For purposes of determining the catalyst system malfunction criteria in 

section (f)(6.2.1): 

(A) The manufacturer shall use a catalyst system deteriorated to the 

malfunction criteria using methods established by the manufacturer to 

represent real world catalyst deterioration under normal and 

malfunctioning operating conditions. 

(B) Except as provided below in section (f)(6.2.2)(C), the malfunction criteria 

shall be established by using a catalyst system with all monitored and 

unmonitored (downstream of the sensor utilized for catalyst monitoring) 

catalysts simultaneously deteriorated to the malfunction criteria. 

(C) For engines using fuel shutoff to prevent over-fueling during misfire 

conditions (see section (f)(2.4.1)(D)), the malfunction criteria shall be 

established by using a catalyst system with all monitored catalysts 

simultaneously deteriorated to the malfunction criteria while unmonitored 

catalysts shall be deteriorated to the end of the engine's useful life. 

(6.3) Monitoring Conditions: Manufacturers shall define the monitoring conditions 

for malfunctions identified in section (f)(6.2) in accordance with sections 

(d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). For purposes of 

tracking and reporting as required in section (d)(3.2.1), all monitors used to 

detect malfunctions identified in section (f)(6.2) shall be tracked separately 

but reported as a single set of values as specified in section (d)(5.2.2). 

(6.4) MIL Illumination and Fault Code Storage: 

(6.4.1) General requirements for MIL illumination and fault code storage are set 

forth in section (d)(2). 

(6.4.2) The monitoring method for the catalyst(s) shall be capable of detecting 

when a catalyst fault code has been cleared (except OBD system 

self-clearing), but the catalyst has not been replaced (e.g., catalyst 

overtemperature histogram approaches are not acceptable). 
69

(7) EVAPORATIVE SYSTEM MONITORING 

(7.1) Requirement: The OBD system shall verify purge flow from the evaporative 

system and shall monitor the complete evaporative system, excluding the 

tubing and connections between the purge valve and the intake manifold, for 

vapor leaks to the atmosphere. Individual components of the evaporative 

system (e.g. valves, sensors) shall be monitored in accordance with the 

comprehensive components requirements in section (g)(3) (e.g., for circuit 

continuity, out of range values, rationality, proper functional response). 

Vehicles not required to be equipped with evaporative emission systems shall 

be exempt from monitoring of the evaporative system.

(7.2) Malfunction Criteria: 

(7.2.1) For purposes of section (f)(7), an “orifice” is defined as an O’Keefe 

Controls Co. precision metal “Type B” orifice with NPT connections with a 

diameter of the specified dimension (e.g., part number B-31-SS for a 

stainless steel 0.031 inch diameter orifice). 

(7.2.2) The OBD system shall detect an evaporative system malfunction when 

any of the following conditions exist: 

(A) No purge flow from the evaporative system to the engine can be detected 

by the OBD system; or 

(B) The complete evaporative system contains a leak or leaks that 

cumulatively are greater than or equal to a leak caused by a 0.150 inch 

diameter orifice. 

(7.2.3) A manufacturer may request the Executive Officer to revise the orifice size 

in section (f)(7.2.2)(B) if the most reliable monitoring method available 

cannot reliably detect a system leak of the magnitudes specified. The 

Executive Officer shall approve the request upon determining that the 

manufacturer has provided data and/or engineering analysis that 

demonstrate the need for the request. 

(7.2.4) Upon request by the manufacturer and upon determining that the 

manufacturer has submitted data and/or engineering evaluation which 

support the request, the Executive Officer shall revise the orifice size in 

section (f)(7.2.2)(B) upward to exclude detection of leaks that cannot 

cause evaporative or running loss emissions to exceed 1.5 times the 

applicable evaporative emission standards. 

(7.2.5) For vehicles that utilize more than one purge flow path (e.g., a turbocharged engine with a low pressure purge line and a high pressure purge 

line), the OBD system shall verify the criteria of (f)(7.2.2)(A) (i.e., purge 

flow to the engine) for both purge flow paths. If a manufacturer 

demonstrates that blockage, leakage, or disconnection of one of the 

purge flow paths cannot cause a measurable emission increase during 

any reasonable in-use driving conditions, monitoring of that flow path is 

not required.

(7.3) Monitoring Conditions: 

(7.3.1) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (f)(7.2.2)(A) (i.e., purge flow) in accordance with 

sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). 

(7.3.2) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (f)(7.2.2)(B) (i.e., 0.150 inch leak detection) in 
70

accordance with sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio 

requirements). For purposes of tracking and reporting as required in 

section (d)(3.2.1), all monitors used to detect malfunctions identified in 

section (f)(7.2.2)(B) shall be tracked separately but reported as a single 

set of values as specified in section (d)(5.2.2). 

(7.3.3) Manufacturers may disable or abort an evaporative system monitor when 

the fuel tank level is over 85 percent of nominal tank capacity or during a 

refueling event. 

(7.3.4) Manufacturers may request Executive Officer approval to execute the 

evaporative system monitor only on driving cycles determined by the 

manufacturer to be cold starts if the condition is needed to ensure reliable 

monitoring. The Executive Officer shall approve the request upon 

determining that data and/or an engineering evaluation submitted by the 

manufacturer demonstrate that a reliable check can only be made on 

driving cycles when the cold start criteria are satisfied. However, in 

making a decision, the Executive Officer will not approve conditions that 

exclude engine starts from being considered as cold starts solely on the 

basis that ambient temperature exceeds (i.e., indicates a higher 

temperature than) engine coolant temperature at engine start. 

(7.3.5) Manufacturers may temporarily disable the evaporative purge system to 

perform an evaporative system leak check. 

(7.4) MIL Illumination and Fault Code Storage: 

(7.4.1) Except as provided below for fuel cap leaks, general requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(7.4.2) If the OBD system is capable of discerning that a system leak is being 

caused by a missing or improperly secured fuel cap:

(A) The manufacturer is not required to illuminate the MIL or store a fault 

code if the vehicle is equipped with an alternative indicator for notifying 

the vehicle operator of the malfunction. The alternative indicator shall be 

of sufficient illumination and location to be readily visible under all lighting 

conditions. 

(B) If the vehicle is not equipped with an alternative indicator and the MIL 

illuminates, the MIL may be extinguished and the corresponding fault 

codes erased once the OBD system has verified that the fuel cap has 

been securely fastened and the MIL has not been illuminated for any 

other type of malfunction. 

(C) The Executive Officer may approve other strategies that provide 

equivalent assurance that a vehicle operator will be promptly notified of a 

missing or improperly secured fuel cap and that corrective action will be 

undertaken. 

(8) EXHAUST GAS SENSOR MONITORING 

(8.1) Requirement: 

(8.1.1) The OBD system shall monitor the output signal, response rate, and any 

other parameter which can affect emissions of all primary (fuel control) 

exhaust gas oxygensensors (conventional switching sensors and wide 

range or universal sensorse.g., oxygen, wide-range air/fuel) for 
71

malfunction. Both the lean-to-rich and rich-to-lean response rates shall be 

monitored.

(8.1.2) The OBD system shall also monitor all secondary exhaust gasoxygen

sensors (those used for secondary fuel trim control or as a monitoring 

device) for proper output signal, activity, and response rate. 

(8.1.3) For engines equipped with heated exhaust gasoxygen sensors, the OBD 

system shall monitor the heater for proper performance. 

(8.1.4) For other types of sensors (e.g., hydrocarbon sensors, NOx sensors), the 

manufacturer shall submit a monitoring plan to the Executive Officer for 

approval. The Executive Officer shall approve the request upon 

determining that the manufacturer has submitted data and an engineering 

evaluation that demonstrate that the monitoring plan is as reliable and 

effective as the monitoring plan required for conventional sensors under 

section (f)(8).

(8.2) Malfunction Criteria: 

(8.2.1) Primary Sensors: 

(A) The OBD system shall detect a malfunction prior to any failure or 

deterioration of the exhaust gasoxygen sensor output voltage, resistance, 

impedance, current, response rate, amplitude, offset, or other 

characteristic(s) (including drift or bias corrected for by secondary 

sensors) that would cause an engine's emissions to exceed 1.5 times any 

of the applicable standards. For response rate (see section (c)), the OBD 

system shall detect asymmetric malfunctions (i.e., malfunctions that 

primarily affect only the lean-to-rich response rate or only the rich-to-lean 

response rate) and symmetric malfunctions (i.e., malfunctions that affect 

both the lean-to-rich and rich-to-lean response rates). As defined in 

section (c), response rate includes delays in the sensor to initially react to 

a change in exhaust gas composition as well as delays during the 

transition from a rich-to-lean (or lean-to-rich) sensor output. For 2013 and 

subsequent model year engines, the manufacturer shall submit data 

and/or engineering analysis to demonstrate that the calibration method 

used ensures proper detection of all symmetric and asymmetric response 

rate malfunctions as part of the certification application.

(B) The OBD system shall detect malfunctions of the exhaust gas oxygen 

sensor caused by either a lack of circuit continuity or out-of-range values. 

(C) The OBD system shall detect a malfunction of the exhaust gasoxygen

sensor when a sensor failure or deterioration causes the fuel system to 

stop using that sensor as a feedback input (e.g., causes default or openloop operation) or causes the fuel system to fail to enter closed-loop

operation within a manufacturer-specified time interval. 

(D) The OBD system shall detect a malfunction of the exhaust gasoxygen

sensor when the sensor output voltage, resistance, impedance, current, 

amplitude, activity, or other characteristics are no longer sufficient for use 

as an OBD system monitoring device (e.g., for catalyst monitoring). 

(8.2.2) Secondary Sensors: 

(A) The OBD system shall detect a malfunction prior to any failure or 

deterioration of the exhaust gasoxygen sensor voltage, resistance, 

impedance, current, response rate, amplitude, offset, or other 
72

characteristic(s) that would cause an engine's emissions to exceed 1.5 

times any of the applicable standards. 

(B) The OBD system shall detect malfunctions of the exhaust gasoxygen

sensor caused by a lack of circuit continuity. 

(C) Sufficient sensor performance for other monitors.

(C)(i) To the extent feasible, tThe OBD system shall detect a malfunction 

of the exhaust gasoxygen sensor when the sensor output voltage, 

resistance, impedance, current, amplitude, activity, offset, or other 

characteristics are no longer sufficient for use as an OBD system 

monitoring device (e.g., for catalyst monitoring). For this requirement, 

“sufficient” is defined as the capability of the worst performing 

acceptable sensor to detect the best performing unacceptable other 

monitored system or component (e.g., catalyst).

(ii) For systems where it is not technically feasible to satisfy the criteria of 

section (f)(8.2.2)(C)(i) completely, the OBD system shall, at a 

minimum, detect a slow rich-to-lean response malfunction during a fuel 

shut-off event (e.g., deceleration fuel cut event) on all 2013 and 

subsequent model year engines. The rich-to-lean response check 

shall monitor both the sensor response time from a rich condition (e.g., 

0.7 Volts) prior to the start of fuel shut-off to a lean condition (e.g., 0.1 

Volts) expected during fuel shut-off conditions and the sensor 

transition time in the intermediate sensor range (e.g., from 0.55 Volts 

to 0.3 Volts).

(iii) Additionally, for systems where it is not technically feasible to satisfy 

the criteria in section (f)(8.2.2)(C)(i), prior to certification of 2013 model 

year engines, the manufacturer must submit a comprehensive plan to 

the Executive Officer demonstrating the manufacturer’s efforts to 

minimize any gap remaining between the worst performing acceptable 

sensor and a sufficient sensor. The plan should include quantification 

of the gap and supporting documentation for efforts to close the gap 

including sensor monitoring improvements, other system component 

monitor improvements (e.g., changes to make the catalyst monitor less 

sensitive to oxygen sensor response), and sensor specification 

changes, if any. The Executive Officer shall approve the plan upon 

determining the submitted information supports the necessity of the 

gap and the plan demonstrates that the manufacturer is taking 

reasonable efforts to minimize or eliminate the gap in a timely manner.

(D) The OBD system shall detect malfunctions of the exhaust gasoxygen

sensor caused by out-of-range values. 

(E) The OBD system shall detect a malfunction of the exhaust gasoxygen

sensor when a sensor failure or deterioration causes the fuel system (e.g., 

fuel control) to stop using that sensor as a feedback input (e.g., causes 

default or open-loop operation). 

(8.2.3) Sensor Heaters: 

(A) The OBD system shall detect a malfunction of the heater performance 

when the current or voltage drop in the heater circuit is no longer within 

the manufacturer's specified limits for normal operation (i.e., within the 

criteria required to be met by the component vendor for heater circuit 
73

performance at high mileage). Subject to Executive Officer approval, 

other malfunction criteria for heater performance malfunctions may be 

used upon the Executive Officer determining that the manufacturer has 

submitted data and/or an engineering evaluation that demonstrate the 

monitoring reliability and timeliness to be equivalent to the stated criteria 

in section (f)(8.2.3)(A). 

(B) The OBD system shall detect malfunctions of the heater circuit including 

open or short circuits that conflict with the commanded state of the heater 

(e.g., shorted to 12 Volts when commanded to 0 Volts (ground)). 

(8.3) Monitoring Conditions: 

(8.3.1) Primary Sensors 

(A) Manufacturers shall define the monitoring conditions for malfunctions 

identified in sections (f)(8.2.1)(A) and (D) (e.g., proper response rate) in 

accordance with sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio 

requirements). For purposes of tracking and reporting as required in 

section (d)(3.2.1), all monitors used to detect malfunctions identified in 

sections (f)(8.2.1)(A) and (D) shall be tracked separately but reported as a 

single set of values as specified in section (d)(5.2.2). 

(B) Except as provided in section (f)(8.3.1)(C), monitoring for malfunctions 

identified in sections (f)(8.2.1)(B) and (C) (i.e., circuit continuity, out-ofrange, and open-loop malfunctions) shall be conducted continuously. 

(C) A manufacturer may request Executive Officer approval to disable 

continuous exhaust gas sensor monitoring when an exhaust gas sensor 

malfunction cannot be distinguished from other effects (e.g., disable outof-range low monitoring during fuel cut conditions). The Executive Officer 

shall approve the disablement upon determining that the manufacturer 

has submitted test data and/or documentation that demonstrate a properly 

functioning sensor cannot be distinguished from a malfunctioning sensor 

and that the disablement interval is limited only to that necessary for 

avoiding false detection. 

(8.3.2) Secondary Sensors 

(A) Manufacturers shall define monitoring conditions for malfunctions 

identified in sections (f)(8.2.2)(A), (B), and (C) (e.g., proper sensor activity) 

in accordance with sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio 

requirements). For all 2013 and subsequent model year engines meeting 

the monitoring requirements of section (f)(8.2.2)(C)(i) or (ii), for purposes 

of tracking and reporting as required in section (d)(3.2.1), all monitors 

used to detect malfunctions identified in sections (f)(8.2.2)(A) and (C) shall 

be tracked separately but reported as a single set of values as specified in 

section (d)(5.2.2).

(B) Except as provided in section (f)(8.3.2)(C), monitoring for malfunctions 

identified in sections (f)(8.2.2)(B), (D), and (E) (i.e., open circuit, out-ofrange malfunctions, open-loop malfunctions) shall be conducted 

continuously. 

(C) A manufacturer may request Executive Officer approval to disable 

continuous exhaust gas sensor monitoring when an exhaust gasoxygen

sensor malfunction cannot be distinguished from other effects (e.g., 

disable out-of-range low monitoring during fuel cut conditions). The 
74

Executive Officer shall approve the disablement upon determining that the 

manufacturer has submitted test data and/or documentation that 

demonstrate a properly functioning sensor cannot be distinguished from a 

malfunctioning sensor and that the disablement interval is limited only to 

that necessary for avoiding false detection. 

(8.3.3) Sensor Heaters 

(A) Manufacturers shall define monitoring conditions for malfunctions 

identified in section (f)(8.2.3)(A) (i.e., sensor heater performance) in 

accordance with sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio

requirements). 

(B) Monitoring for malfunctions identified in section (f)(8.2.3)(B) (i.e., circuit 

malfunctions) shall be conducted continuously. 

(8.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(9) VARIABLE VALVE TIMING AND/OR CONTROL (VVT) SYSTEM 

MONITORING 

(9.1) Requirement: The OBD system shall monitor the VVT system on engines 

so-equipped for target error and slow response malfunctions. The individual 

electronic components (e.g., actuators, valves, sensors) that are used in the 

VVT system shall be monitored in accordance with the comprehensive 

components requirements in section (g)(3). 

(9.2) Malfunction Criteria: 

(9.2.1) Target Error: The OBD system shall detect a malfunction prior to any 

failure or deterioration in the capability of the VVT system to achieve the 

commanded valve timing and/or control within a crank angle and/or lift 

tolerance that would cause an engine’s emissions to exceed 1.5 times any 

of the applicable standards. 

(9.2.2) Slow Response: The OBD system shall detect a malfunction prior to any 

failure or deterioration in the capability of the VVT system to achieve the 

commanded valve timing and/or control within a manufacturer-specified 

time that would cause an engine’s emissions to exceed 1.5 times any of 

the applicable standards for gasoline engines. 

(9.2.3) For engines in which no failure or deterioration of the VVT system could 

result in an engine’s emissions exceeding 1.5 times any of the applicable 

standards, the OBD system shall detect a malfunction of the VVT system 

when proper functional response of the system to computer commands 

does not occur. 

(9.3) Monitoring Conditions: Manufacturers shall define the monitoring conditions 

for VVT system malfunctions identified in section (f)(9.2) in accordance with 

sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements), with the 

exception that monitoring shall occur every time the monitoring conditions are 

met during the driving cycle in lieu of once per driving cycle as required in 

section (d)(3.1.2). For purposes of tracking and reporting as required in 

section (d)(3.2.1), all monitors used to detect malfunctions identified in 

section (f)(9.2) shall be tracked separately but reported as a single set of 

values as specified in section (d)(5.2.2). 
75

(9.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(g) MONITORING REQUIREMENTS FOR ALL ENGINES 

(1) ENGINE COOLING SYSTEM MONITORING 

(1.1) Requirement: 

(1.1.1) The OBD system shall monitor the thermostat on engines so-equipped for 

proper operation. 

(1.1.2) The OBD system shall monitor the engine coolant temperature (ECT) 

sensor for circuit continuity, out-of-range values, and rationality faults. 

(1.1.3) For engines that use a system other than the cooling system and ECT 

sensor (e.g., oil temperature, cylinder head temperature) for an indication 

of engine operating temperature for emission control purposes (e.g., to 

modify spark or fuel injection timing or quantity), the manufacturer shall 

submit a monitoring plan to the Executive Officer for approval. The 

Executive Officer shall approve the request upon determining that the 

manufacturer has submitted data and an engineering evaluation that 

demonstrate that the monitoring plan is as reliable and effective as the 

monitoring required for the engine cooling system under section (g)(1). 

(1.2) Malfunction Criteria: 

(1.2.1) Thermostat 

(A) The OBD system shall detect a thermostat malfunction if, within an 

Executive Officer-approved time interval after engine start, any of the 

following conditions occur: 

(i) The coolant temperature does not reach the highest temperature 

required by the OBD system to enable other diagnostics; 

(ii) The coolant temperature does not reach a warmed-up temperature 

within 20 degrees Fahrenheit of the manufacturer’s nominal thermostat 

regulating temperature. Subject to Executive Officer approval, a 

manufacturer may utilize lower temperatures for this criterion upon the 

Executive Officer determining that the manufacturer has demonstrated 

that the fuel, spark timing, and/or other coolant temperature-based 

modifications to the engine control strategies would not cause an 

emission increase of 50 or more percent of any of the applicable 

standards (e.g., 50 degree Fahrenheit emission test). 

(B) For 2016 and subsequent model year engines, the OBD system shall 

detect a thermostat fault if, after the coolant temperature has reached the 

temperatures indicated in sections (g)(1.2.1)(A)(i) and (ii), the coolant 

temperature drops below the temperature indicated in section 

(g)(1.2.1)(A)(i).

(B)(C) Executive Officer approval of the time interval after engine start under 

section (g)(1.2.1)(A) above shall be granted upon determining that the 

data and/or engineering evaluation submitted by the manufacturer 

supports the specified times. 

(C)(D) For monitoring of malfunctions under section (g)(1.2.1)(A), Wwith 

Executive Officer approval, a manufacturer may use alternate malfunction 

criteria and/or monitoring conditions (see section (g)(1.3)) that are a 

function of temperature at engine start on engines that do not reach the 
76

temperatures specified in the malfunction criteria when the thermostat is 

functioning properly. Executive Officer approval shall be granted upon 

determining that the manufacturer has submitted data that demonstrate 

that a properly operating system does not reach the specified 

temperatures, that the monitor is capable of meeting the specified 

malfunction criteria at engine start temperatures greater than 50 degrees 

Fahrenheit, and that the possibility for cooling system malfunctions to go 

undetected and disable other OBD monitors is minimized to the extent 

technically feasible. 

(D)(E) A manufacturer may request Executive Officer approval to be 

exempted from the requirements of thermostat monitoring. Executive 

Officer approval shall be granted upon determining that the manufacturer 

has demonstrated that a malfunctioning thermostat cannot cause a 

measurable increase in emissions during any reasonable driving condition 

nor cause any disablement of other monitors. 

(1.2.2) ECT Sensor 

(A) Circuit Continuity. The OBD system shall detect a malfunction when a 

lack of circuit continuity or out-of-range values occur. 

(B) Time to Reach Closed-Loop/Feedback Enable Temperature. 

(i) The OBD system shall detect a malfunction if the ECT sensor does not 

achieve the highest stabilized minimum temperature which is needed 

for closed-loop/feedback control of all emission control systems (e.g., 

fuel system, EGR system) within an Executive Officer-approved time 

interval after engine start. 

(ii) The time interval shall be a function of starting ECT and/or a function 

of intake air temperature. Executive Officer approval of the time 

interval shall be granted upon determining that the data and/or 

engineering evaluation submitted by the manufacturer supports the 

specified times. 

(iii) Manufacturers are exempted from the requirements of section 

(g)(1.2.2)(B) if the manufacturer does not utilize ECT to enable closedloop/feedback control of any emission control system. 

(C) Stuck in Range Below the Highest Minimum Enable Temperature. To the 

extent feasible when using all available information, the OBD system shall 

detect a malfunction if the ECT sensor inappropriately indicates a 

temperature below the highest minimum enable temperature required by 

the OBD system to enable other diagnostics (e.g., an OBD system that 

requires ECT to be greater than 140 degrees Fahrenheit to enable a 

diagnostic must detect malfunctions that cause the ECT sensor to 

inappropriately indicate a temperature below 140 degrees Fahrenheit). 

Manufacturers are exempted from this requirement for temperature 

regions in which the monitors required under sections (g)(1.2.1) or 

(g)(1.2.2)(B) will detect ECT sensor malfunctions as defined in section 

(g)(1.2.2)(C). 

(D) Stuck in Range Above the Lowest Maximum Enable Temperature. 

(i) To the extent feasible when using all available information, the OBD 

system shall detect a malfunction if the ECT sensor inappropriately 

indicates a temperature above the lowest maximum enable 
77

temperature required by the OBD system to enable other diagnostics 

(e.g., an OBD system that requires ECT to be less than 90 degrees 

Fahrenheit at engine start to enable a diagnostic must detect 

malfunctions that cause the ECT sensor to inappropriately indicate a 

temperature above 90 degrees Fahrenheit). 

(ii) Manufacturers are exempted from this requirement for temperature 

regions in which the monitors required under sections (g)(1.2.1), 

(g)(1.2.2)(B), or (g)(1.2.2)(C) (i.e., ECT sensor or thermostat 

malfunctions) will detect ECT sensor malfunctions as defined in 

section (g)(1.2.2)(D) or in which the MIL will be illuminated under the 

requirements of sections (d)(2.2.1)(E) or (d)(2.2.2)(E) for default mode 

operation (e.g., overtemperature protection strategies). 

(iii) Manufacturers are exempted from the requirements of section 

(g)(1.2.2)(D) for temperature regions where the temperature gauge 

indicates a temperature in the red zone (engine overheating zone) for 

vehicles that have a temperature gauge (not a warning light) on the 

instrument panel and utilize the same ECT sensor for input to the OBD 

system and the temperature gauge. 

(1.3) Monitoring Conditions: 

(1.3.1) Thermostat 

(A) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (g)(1.2.1)(A) in accordance with section (d)(3.1)

except as provided for in section (g)(1.3.1)(E). Additionally, except as 

provided for in sections (g)(1.3.1)(B) and (C), monitoring for malfunctions 

identified in section (g)(1.2.1)(A) shall be conducted once per driving cycle 

on every driving cycle in which the ECT sensor indicates, at engine start, 

a temperature lower than the temperature established as the malfunction 

criteria in section (g)(1.2.1)(A). 

(B) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (g)(1.2.1)(B) in accordance with section (d)(3.1) with 

the exception that monitoring shall occur every time the monitoring 

conditions are met during the driving cycle in lieu of once per driving cycle.

(B)(C) Manufacturers may disable thermostat monitoring at ambient engine 

start temperatures below 20 degrees Fahrenheit. 

(C)(D) Manufacturers may request Executive Officer approval to suspend or 

disable thermostat monitoring if the vehicle is subjected to conditions 

which could lead to false diagnosis (e.g., vehicle operation at idle for more 

than 50 percent of the warm-up time, hot restart conditions). In general, 

the Executive Officer shall not approve disablement of the monitor on 

engine starts where the ECT at engine start is more than 35 degrees 

Fahrenheit lower than the thermostat malfunction threshold temperature 

determined under section (g)(1.2.1)(A). The Executive Officer shall 

approve the request upon determining that the manufacturer has provided 

data and/or engineering analysis that demonstrate the need for the 

request. 

(E) With respect to defining enable conditions that are encountered during 

the FTP cycle as required in (d)(3.1.1) for malfunctions identified in 
78

section (g)(1.2.1)(A), the FTP cycle shall refer to on-road driving following 

the FTP cycle in lieu of testing on an engine dynamometer.

(1.3.2) ECT Sensor 

(A) Except as provided below in section (g)(1.3.2)(E), monitoring for 

malfunctions identified in section (g)(1.2.2)(A) (i.e., circuit continuity and 

out-of-range) shall be conducted continuously. 

(B) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (g)(1.2.2)(B) in accordance with section (d)(3.1). 

Additionally, except as provided for in section (g)(1.3.2)(D), monitoring for 

malfunctions identified in section (g)(1.2.2)(B) shall be conducted once 

per driving cycle on every driving cycle in which the ECT sensor indicates 

a temperature lower than the closed-loop enable temperature at engine 

start (i.e., all engine start temperatures greater than the ECT sensor outof-range low temperature and less than the closed-loop enable 

temperature). 

(C) Manufacturers shall define the monitoring conditions for malfunctions 

identified in sections (g)(1.2.2)(C) and (D) in accordance with sections 

(d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). 

(D) Manufacturers may suspend or delay the time to reach closed-loop 

enable temperature diagnostic if the vehicle is subjected to conditions 

which could lead to false diagnosis (e.g., vehicle operation at idle for more 

than 50 to 75 percent of the warm-up time). 

(E) A manufacturer may request Executive Officer approval to disable 

continuous ECT sensor monitoring when an ECT sensor malfunction 

cannot be distinguished from other effects. The Executive Officer shall 

approve the disablement upon determining that the manufacturer has 

submitted test data and/or engineering evaluation that demonstrate a 

properly functioning sensor cannot be distinguished from a malfunctioning 

sensor and that the disablement interval is limited only to that necessary 

for avoiding false detection. 

(1.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(2) CRANKCASE VENTILATION (CV) SYSTEM MONITORING 

(2.1) Requirement: 

(2.1.1)The OBD system shall monitor the CV system on engines so-equipped 

for system integrity. Engines not required subject to crankcase emission 

control requirements be equipped with CV systems shall be exempt from 

monitoring of the CV system. 

(2.1.1)For diesel engines, the manufacturer shall submit a plan for Executive 

Officer approval of the monitoring strategy, malfunction criteria, and 

monitoring conditions prior to OBD certification. Executive Officer 

approval shall be based on the effectiveness of the monitoring strategy to 

monitor the performance of the CV system to the extent feasible with 

respect to the malfunction criteria in section (g)(2.2) below and the 

monitoring conditions required by the diagnostic.

(2.2) Malfunction Criteria: 
79

(2.2.1) For the purposes of section (g)(2), “CV system” is defined as any form of 

crankcase ventilation system, regardless of whether it utilizes positive 

pressure or whether it vents to the atmosphere, the intake, or the exhaust. 

 “CV valve” is defined as any form of valve or orifice, and/or 

filter/separator used to restrict, or control, or alter the composition (e.g., 

remove oil vapor or particulate matter) of the crankcase vapor flow. 

Further, any additional external CV system tubing or hoses used to 

equalize crankcase pressure or to provide a ventilation path between 

various areas of the engine (e.g., crankcase and valve cover) are 

considered part of the CV system “between the crankcase and the CV 

valve” and subject to the malfunction criteria in section (g)(2.2.2) below. 

(2.2.2) Except as provided below, the OBD system shall detect a malfunction of 

the CV system when a disconnection of the system occurs between either 

the crankcase and the CV valve, or between the CV valve and the intake 

manifoldducting. 

(2.2.3) If disconnection in the system results in a rapid loss of oil or other overt 

indication of a CV system malfunction such that the vehicle operator is 

certain to respond and have the vehicle repaired, the Executive Officer 

shall exempt the manufacturer from detection of that disconnection.

(2.2.3)(2.2.4) The Executive Officer shall exempt a manufacturer from detecting a 

disconnection between the crankcase and the CV valve upon determining 

that the disconnection cannot be made without first disconnecting a 

monitored portion of the system (e.g., the CV system is designed such 

that the CV valve is fastened directly to the crankcase in a manner which 

makes it significantly more difficult to remove the valve from the 

crankcase rather than disconnect the line between the valve and the 

intake manifold/ducting (taking aging effects into consideration)) and the

line between the valve and the intake ducting is monitored for 

disconnection. The manufacturer shall file a request and submit data 

and/or engineering evaluation in support of the exemption. 

(2.2.4)(2.2.5) Subject to The Executive Officer approval, shall exempt a 

manufacturer from detecting a disconnection between the crankcase and 

the CV valve for system designs that utilize tubing between the valve and 

the crankcase shall be exempted from the monitoring requirement for 

detection of disconnection upon determining that the connections 

between the CV valve and the crankcase. The manufacturer shall file a 

request and submit data and/or engineering evaluation in support of the 

request. The Executive Officer shall approve the request upon 

determining that the connections between the valve and the crankcase

are: (1) resistant to deterioration or accidental disconnection, (2) 

significantly more difficult to disconnect than the line between the valve 

and the intake manifold/ducting, and (3) not subject to disconnection per 

manufacturer’s maintenance, service, and/or repair procedures for nonCV system repair work. The manufacturer shall file a request and submit 

data and/or engineering evaluation in support of the exemption.

(2.2.5)(2.2.6) The Executive Officer shall exempt a manufacturer from detecting a 

disconnection between the CV valve and the intake manifold upon 

determining that the disconnection (1) causes the vehicle to stall 
80

immediately during idle operation; or (2) is unlikely to occur due to a CV 

system design that is integral to the induction system (e.g., machined 

passages rather than tubing or hoses). The manufacturer shall file a 

request and submit data and/or engineering evaluation in support of the 

exemption. 

(2.2.7) For engines certified on an engine dynamometer having an open CV 

system (i.e., a system that releases crankcase emissions to the 

atmosphere without routing them to the intake ducting or to the exhaust 

upstream of the aftertreatment), the manufacturer shall submit a plan for 

Executive Officer approval of the monitoring strategy, malfunction criteria, 

and monitoring conditions prior to OBD certification. Executive Officer 

approval shall be based on the effectiveness of the monitoring strategy to 

(i) monitor the performance of the CV system to the extent feasible with 

respect to the malfunction criteria in section (g)(2.2.1) through (g)(2.2.4) 

and the monitoring conditions required by the diagnostic, and (ii) monitor 

the ability of the CV system to control crankcase vapor emitted to the 

atmosphere relative to the manufacturer’s design and performance 

specifications for a properly functioning system (e.g., if the system is 

equipped with a filter and/or separator to reduce crankcase emissions to 

the atmosphere, the OBD system shall monitor the integrity of the filter

and/or function of the separator).

(2.3) Monitoring Conditions: Manufacturers shall define the monitoring conditions 

for malfunctions identified in section (g)(2.2) in accordance with sections 

(d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). 

(2.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). The stored 

fault code need not specifically identify the CV system (e.g., a fault code for 

idle speed control or fuel system monitoring can be stored) if the 

manufacturer demonstrates that additional monitoring hardware would be 

necessary to make this identification, and provided the manufacturer’s 

diagnostic and repair procedures for the detected malfunction include 

directions to check the integrity of the CV system.

(3) COMPREHENSIVE COMPONENT MONITORING 

(3.1) Requirement: 

(3.1.1) Except as provided in sections (g)(3.1.4), (g)(3.1.5), and (g)(4), the OBD 

system shall monitor for malfunction any electronic engine 

component/system not otherwise described in sections (e)(1) through 

(g)(2) that either provides input to (directly or indirectly) or receives 

commands from the on-board computer(s), and: (1) can affect emissions 

during any reasonable in-use driving condition, or (2) is used as part of 

the diagnostic strategy for any other monitored system or component. 

(A) Input Components: Input components required to be monitored may 

include the crank angle sensor, knock sensor, throttle position sensor, 

cam position sensor, intake air temperature sensor, boost pressure 

sensor, manifold pressure sensor, mass air flow sensor, exhaust 

temperature sensor, exhaust pressure sensor, fuel pressure sensor, fuel 

composition sensor (e.g. flexible fuel vehicles), and electronic 
81

components used to comply with any applicable engine idling 

requirements of title 13, CCR section 1956.8. 

(B) Output Components/Systems: Output components/systems required to be 

monitored may include the idle speed control system, fuel injectors, glow 

plug system, variable length intake manifold runner systems, 

supercharger or turbocharger electronic components, heated fuel 

preparation systems, and the wait-to-start lamp on diesel applications, 

and the MIL. 

(3.1.2) For purposes of criteria (1) in section (g)(3.1.1) above, the manufacturer 

shall determine whether an engine input or output component/system can 

affect emissions. If the Executive Officer reasonably believes that a 

manufacturer has incorrectly determined that a component/system cannot 

affect emissions, the Executive Officer shall require the manufacturer to 

provide emission data showing that the component/system, when 

malfunctioning and installed in a suitable test vehicle, does not have an 

emission effect. The Executive Officer may request Eemission data may 

be requested for any reasonable driving condition. 

(3.1.3) Manufacturers shall monitor for malfunction electronic powertrain input or 

output components/systems associated with an electronic transfer case, 

electronic power steering system, or other components that are driven by 

the engine and not related to the control of fueling, air handling, or 

emissions only if the transfer case component or system is used as part of 

the diagnostic strategy for any other monitored system or componentFor 

purposes of section (g)(3), ”electronic engine components/systems” does 

not include components that are driven by the engine and are not related 

to the control of the fueling, air handling, or emissions of the engine (e.g., 

PTO components, air conditioning system components, and power 

steering components). 

(3.1.4) Except as specified for hybrids in section (g)(3.1.5), manufacturers shall 

monitor for malfunction electronic powertrain input or output 

components/systems associated with components that only affect 

emissions by causing additional electrical load to the engine and are not 

related to the control of fueling, air handling, or emissions only if the 

component or system is used as part of the diagnostic strategy for any 

other monitored system or component.

(3.1.5) For hybrids, manufacturers shall submit a plan to the Executive Officer for 

approval of the hybrid components determined by the manufacturer to be 

subject to monitoring in section (g)(3.1.1). In general, the Executive 

Officer shall approve the plan if it includes monitoring of all 

components/systems used as part of the diagnostic strategy for any other 

monitored system or component, monitoring of all energy input devices to 

the electrical propulsion system, monitoring of battery and charging 

system performance, monitoring of electric motor performance, and 

monitoring of regenerative braking performance.

(3.2) Malfunction Criteria: 

(3.2.1) Input Components: 

(A) The OBD system shall detect malfunctions of input components caused 

by a lack of circuit continuity, out-of-range values, and, where feasible, 
82

rationality faults. To the extent feasible, the rationality fault diagnostics 

shall verify that a sensor output is neither inappropriately high nor 

inappropriately low (i.e., shall be “two-sided” diagnostics). 

(B) To the extent feasible, the OBD system shall separately detect and store 

different fault codes that distinguish rationality faults from lack of circuit 

continuity and out-of-range faults. For input component lack of circuit 

continuity and out-of-range faults, the OBD system shall, to the extent 

feasible, separately detect and store different fault codes for each distinct 

malfunction (e.g., out-of-range low, out-of-range high, open circuit). The 

OBD system is not required to store separate fault codes for lack of circuit 

continuity faults that cannot be distinguished from other out-of-range 

circuit faults. 

(C) For input components that are used to activate alternate strategies that 

can affect emissions (e.g., AECDs, engine shutdown systems or 

strategies to meet NOx idling standards required by title 13, CCR section 

1956.8), the OBD system shall detect rationality malfunctions that cause 

the system to erroneously activate or deactivate the alternate strategy. To 

the extent feasible when using all available information, the rationality fault 

diagnostics shall detect a malfunction if the input component 

inappropriately indicates a value that activates or deactivates the alternate 

strategy. For example, if an alternate strategy requires the intake air 

temperature to be greater than 120 degrees Fahrenheit to activate, the 

OBD system shall detect malfunctions that cause the intake air 

temperature sensor to inappropriately indicate a temperature above 120 

degrees Fahrenheit. 

(D) For input components that are directly or indirectly used for any emission 

control strategies that are not covered under sections (e), (f), and (g)(1) 

(e.g., exhaust temperature sensors used for a control strategy that 

regulates SCR catalyst inlet temperature within a target window), the OBD 

system shall detect rationality malfunctions that prevent the component 

from correctly sensing any condition necessary for the strategy to operate 

in its intended manner. These malfunctions include faults that 

inappropriately prevent or delay the activation of the emission control 

strategy, cause the system to erroneously exit the emission control 

strategy, or where the control strategy has used up all of the adjustments 

or authority allowed by the manufacturer and is still unable to achieve the 

desired condition. The Executive Officer may waive detection of specific 

malfunctions upon determining that the manufacturer has submitted data 

and/or an engineering evaluation that demonstrate that reliable detection 

of the malfunction is technically infeasible or would require additional 

hardware.

(D)(E) For engines that require precise alignment between the camshaft and 

the crankshaft, the OBD system shall monitor the crankshaft position 

sensor(s) and camshaft position sensor(s) to verify proper alignment 

between the camshaft and crankshaft in addition to monitoring the 

sensors for circuit continuity and rationality malfunctions. Proper 

alignment monitoring between a camshaft and a crankshaft shall only be 

required in cases where both are equipped with position sensors. For 
83

engines equipped with VVT systems and a timing belt or chain, the OBD 

system shall detect a malfunction if the alignment between the camshaft 

and crankshaft is off by one or more cam/crank sprocket cogs (e.g., the 

timing belt/chain has slipped by one or more teeth/cogs). If a 

manufacturer demonstrates that a single tooth/cog misalignment cannot 

cause a measurable increase in emissions during any reasonable driving 

condition, the OBD system shall detect a malfunction when the minimum 

number of teeth/cogs misalignment needed to cause a measurable 

emission increase has occurred. 

(3.2.2) Output Components/Systems: 

(A) The OBD system shall detect a malfunction of an output 

component/system when proper functional response of the component 

and system to computer commands does not occur. If a functional check 

is not feasible, the OBD system shall detect malfunctions of output 

components/systems caused by a lack of circuit continuity or circuit fault 

(e.g., short to ground or high voltage). For output component lack of 

circuit continuity faults and circuit faults, the OBD system is not required to 

store different fault codes for each distinct malfunction (e.g., open circuit, 

shorted low). Manufacturers are not required to activate an output 

component/system when it would not normally be active exclusively for 

the purposes of performing functional monitoring of output 

components/systems as required in section (g)(3). 

(B) The idle control system shall be monitored for proper functional response 

to computer commands. 

(i) For gasoline engines using monitoring strategies based on deviation 

from target idle speed, a malfunction shall be detected when either of 

the following conditions occur: 

a. The idle speed control system cannot achieve the target idle speed 

within 200 revolutions per minute (rpm) above the target speed or 

100 rpm below the target speed. The Executive Officer shall allow 

larger engine speed tolerances upon determining that a 

manufacturer has submitted data and/or an engineering evaluation 

which demonstrate that the tolerances can be exceeded without a 

malfunction being present. 

b. The idle speed control system cannot achieve the target idle speed 

within the smallest engine speed tolerance range required by the 

OBD system to enable any other monitors. 

(ii) For diesel engines, a malfunction shall be detected when either any of 

the following conditions occur: 

a. The idle fuel control system cannot achieve or maintain the target 

idle speed or fuel injection quantity within +/-50 percent of the 

manufacturer-specified fuel quantity and target or desired engine 

speed tolerances. 

b. The idle fuel control system cannot achieve the target or desired idle 

speed or fueling quantity within the smallest engine speed or 

fueling quantity tolerance range required by the OBD system to 

enable any other monitors. 

c. For 2013 and subsequent model year engines, the idle control 
84

system cannot achieve the fueling quantity within the smallest 

fueling quantity tolerance range required by the OBD system to 

enable any other monitors.

d. For 2013 and subsequent model year engines, the idle control 

system cannot achieve the target idle speed with a fuel injection 

quantity within +/-50 percent of the fuel quantity necessary to 

achieve the target idle speed for a properly functioning engine and 

the given operating conditions.

(C) Glow plugs/intake air heater systems shall be monitored for proper 

functional response to computer commands and for circuit continuity 

faults. The glow plug/intake air heater circuit(s) shall be monitored for 

proper current and voltage drop. The Executive Officer shall approve 

other monitoring strategies based on manufacturer’s data and/or 

engineering analysis demonstrating equally reliable and timely detection 

of malfunctions. Except as provided below, the OBD system shall detect 

a malfunction when a single glow plug no longer operates within the 

manufacturer’s specified limits for normal operation. If a manufacturer 

demonstrates that a single glow plug failure cannot cause a measurable 

increase in emissions during any reasonable driving condition, the OBD 

system shall detect a malfunction for the minimum number of glow plugs 

needed to cause an emission increase. Further, to the extent feasible on 

existing engine designs (without adding additional hardware for this 

purpose) and on all new 2013 and subsequent model year design 

engines, the stored fault code shall identify the specific malfunctioning 

glow plug(s). 

(D) The wait-to-start lamp circuit and the MIL circuit shall be monitored for 

malfunctions that cause either the lamp to fail to illuminate when 

commanded on (e.g., burned out bulb). 

(E) For output components/systems that are directly or indirectly used for any 

emission control strategies that are not covered under sections (e), (f), 

and (g)(1) (e.g., an intake throttle used for a control strategy that adjusts 

intake throttle position to regulate SCR catalyst inlet temperature within a 

target window), the OBD system shall detect functional malfunctions that 

prevent the component/system from achieving the desired functional 

response necessary for the strategy to operate in its intended manner. 

These malfunctions include faults that inappropriately prevent or delay the 

activation of the emission control strategy, cause the system to 

erroneously exit the emission control strategy, or where the control 

strategy has used up all of the adjustments or authority allowed by the 

manufacturer and is still unable to achieve the desired condition. The 

Executive Officer may waive detection of specific malfunctions upon 

determining that the manufacturer has submitted data and/or an 

engineering evaluation that demonstrate that reliable detection of the 

malfunction is technically infeasible or would require additional hardware.

(F) For 2013 and subsequent model year engines that utilize fuel control 

system components (e.g., injectors, fuel pump) that have tolerance 

compensation features implemented in hardware or software during 

production or repair procedures (e.g., individually coded injectors for flow 
85

characteristics that are programmed into an electronic control unit to 

compensate for injector to injector tolerances, fuel pumps that use in-line 

resistors to correct for differences in fuel pump volume output), the 

components shall be monitored to ensure the proper compensation is 

being used. The system shall detect a fault if the compensation being 

used by the control system does not match the compensation designated 

for the installed component (e.g., the flow characteristic coding designated 

on a specific injector does not match the compensation being used by the 

fuel control system for that injector). If a manufacturer demonstrates that 

a single component (e.g., injector) using the wrong compensation cannot 

cause a measurable increase in emissions during any reasonable driving 

condition, the manufacturer shall detect a malfunction for the minimum 

number of components using the wrong compensation needed to cause 

an emission increase. Further, the stored fault code shall identify the 

specific component that does not match the compensation.

(3.3) Monitoring Conditions: 

(3.3.1) Input Components: 

(A) Except as provided in section (g)(3.3.1)(C), input components shall be 

monitored continuously for proper range of values and circuit continuity. 

(B) For rationality monitoring (where applicable) manufacturers shall define 

the monitoring conditions for detecting malfunctions in accordance with 

sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements), with the 

exception that rationality monitoring shall occur every time the monitoring 

conditions are met during the driving cycle in lieu of once per driving cycle 

as required in section (d)(3.1.2). 

(C) A manufacturer may request Executive Officer approval to disable 

continuous input component proper range of values or circuit continuity 

monitoring when a malfunction cannot be distinguished from other effects. 

 The Executive Officer shall approve the disablement upon determining 

that the manufacturer has submitted test data and/or documentation that 

demonstrate a properly functioning input component cannot be 

distinguished from a malfunctioning input component and that the 

disablement interval is limited only to that necessary for avoiding false 

detection. 

(3.3.2) Output Components/Systems: 

(A) Except as provided in section (g)(3.3.2)(D), monitoring for circuit 

continuity and circuit faults shall be conducted continuously. 

(B) Except as provided in section (g)(3.3.2)(C), for functional monitoring, 

manufacturers shall define the monitoring conditions for detecting 

malfunctions in accordance with sections (d)(3.1) and (d)(3.2) (i.e., 

minimum ratio requirements). 

(C) For the idle control system, manufacturers shall define the monitoring 

conditions for functional monitoring in accordance with sections (d)(3.1) 

and (d)(3.2) (i.e., minimum ratio requirements), with the exception that 

functional monitoring shall occur every time the monitoring conditions are 

met during the driving cycle in lieu of once per driving cycle as required in 

section (d)(3.1.2). 
86

(D) A manufacturer may request Executive Officer approval to disable 

continuous output component circuit continuity or circuit fault monitoring 

when a malfunction cannot be distinguished from other effects. The 

Executive Officer shall approve the disablement upon determining that the 

manufacturer has submitted test data and/or documentation that 

demonstrate a properly functioning output component cannot be 

distinguished from a malfunctioning output component and that the 

disablement interval is limited only to that necessary for avoiding false 

detection. 

(3.4) MIL Illumination and Fault Code Storage: 

(3.4.1) Except as provided in sections (g)(3.4.2) and (3.4.4) and (3.4.3) below, 

general requirements for MIL illumination and fault code storage are set 

forth in section (d)(2). 

(3.4.2) Exceptions to general requirements for MIL illumination. MIL illumination 

is not required in conjunction with storing a confirmed or MIL-on fault code 

for any comprehensive component if: 

(A) the component or system, when malfunctioning, could not cause engine 

emissions to increase by 15 percent or more of the FTP standard during 

any reasonable driving condition; and 

(B) the component or system is not used as part of the diagnostic strategy for 

any other monitored system or component. 

(3.4.3)Exceptions for MIL circuit faults. MIL illumination is not required if a 

malfunction in the MIL circuit that prevents the MIL from illuminating (e.g., 

burned out bulb or LED) has been detected. However, the electronic MIL 

status (see section (h)(4.2)) shall be reported as MIL commanded-on and 

a confirmed or MIL-on fault code (see section (h)(4.4)) shall be stored.

(3.4.3) For purposes of determining the emission increase in section 

(g)(3.4.2)(A), the manufacturer shall request Executive Officer approval of 

the test cycle/vehicle operating conditions for which the emission increase 

will be determined. Executive Officer approval shall be granted upon 

determining that the manufacturer has submitted data and/or engineering 

evaluation that demonstrate that the testing conditions represent in-use 

driving conditions where emissions are likely to be most affected by the 

malfunctioning component. For purposes of determining whether the 

specified percentages in section (g)(3.4.2)(A) are exceeded, if the 

approved testing conditions are comprised of an emission test cycle with 

an emission standard, the measured increase shall be compared to a 

percentage of the emission standard (e.g., if the increase is equal to or 

more than 15 percent of the emission standard for that test cycle). If the 

approved testing conditions are comprised of a test cycle or vehicle 

operating condition that does not have an emission standard, the 

measured increase shall be calculated as a percentage of the baseline 

test (e.g., if the increase from a back-to-back test sequence between 

normal and malfunctioning condition is equal to or more than 15 percent 

of the baseline test results from the normal condition).

(3.4.4) For malfunctions required to be detected by section (g)(3.2.2)(B)(ii)d. (idle 

control fuel injection quantity faults), the stored fault code is not required 

to specifically identify the idle control system (e.g., a fault code for cylinder 
87

fuel injection quantity imbalance or combustion quality monitoring can be 

stored).

(4) OTHER EMISSION CONTROL SYSTEM MONITORING 

(4.1) Requirement: For other emission control systems that are: (1) not identified or 

addressed in sections (e)(1) through (g)(3) (e.g., hydrocarbon traps, 

homogeneous charge compression ignition (HCCI) control systems), or (2) 

identified or addressed in section (g)(3) but not corrected or compensated for 

by an adaptive control system (e.g., swirl control valves), manufacturers shall 

submit a plan for Executive Officer approval of the monitoring strategy, 

malfunction criteria, and monitoring conditions prior to introduction on a 

production engine. Executive Officer approval shall be based on the 

effectiveness of the monitoring strategy, the malfunction criteria utilized, the 

monitoring conditions required by the diagnostic, and, if applicable, the 

determination that the requirements of section (g)(4.2) and (g)(4.3) below are 

satisfied. 

(4.2) For engines that utilize emission control systems that alter intake air flow or 

cylinder charge characteristics by actuating valve(s), flap(s), etc. in the intake 

air delivery system (e.g., swirl control valve systems), the manufacturers, in 

addition to meeting the requirements of section (g)(4.1) above, may elect to 

have the OBD system monitor the shaft to which all valves in one intake bank 

are physically attached in lieu of monitoring the intake air flow, cylinder 

charge, or individual valve(s)/flap(s) for proper functional response. For nonmetal shafts or segmented shafts, the monitor shall verify all shaft segments 

for proper functional response (e.g., by verifying the segment or portion of the 

shaft furthest from the actuator properly functions). For systems that have 

more than one shaft to operate valves in multiple intake banks, 

manufacturers are not required to add more than one set of detection 

hardware (e.g., sensor, switch) per intake bank to meet this requirement. 

(4.3) For emission control strategies that are not covered under sections (e), (f), 

and (g)(1) (e.g., a control strategy that regulates SCR catalyst inlet 

temperatures within a target window), Executive Officer approval shall be 

based on the effectiveness of the plan in detecting malfunctions that prevent 

the strategy from operating in its intended manner. These malfunctions 

include faults that inappropriately prevent or delay the activation of the 

emission control strategy, faults that cause the system to erroneously exit the 

emission control strategy, and faults where the control strategy has used up 

all of the adjustments or authority allowed by the manufacturer and is still 

unable to achieve the desired condition. The Executive Officer may waive 

detection of specific malfunctions upon determining that the manufacturer 

has submitted data and/or an engineering evaluation that demonstrate that 

reliable detection of the malfunction is technically infeasible or would require 

additional hardware.

(5) EXCEPTIONS TO MONITORING REQUIREMENTS 

(5.1) Upon request of a manufacturer or upon the best engineering judgment of the 

ARB, the Executive Officer may revise the emission threshold for any monitor 

in sections (e) through (g) or revise the PM filter malfunction criteria of section 
88

(e)(8.2.1) to exclude detection of specific failure modes (e.g., partially melted 

substrates) if the most reliable monitoring method developed requires a 

higher threshold (or, in the case of section (e)(8.2.1), the exclusion of specific 

failure modes) to prevent significant errors of commission in detecting a 

malfunction. 

(5.2) For 2010 through 2012 model year diesel engines, in determining the 

malfunction criteria for diesel engine monitors in sections (e)(1), (3), (4), (5), 

(8.2.2), (8.2.4), (9.2.1)(A), and (e)(10), the manufacturer shall use a threshold 

of 2.5 times any of the applicable NMHC, CO, or NOx standards in lieu of 2.0 

times any of the applicable standards.

(5.3) Manufacturers may request Executive Officer approval to disable an OBD 

system monitor at ambient engine start temperatures below 20 degrees 

Fahrenheit (low ambient temperature conditions may be determined based 

on intake air or engine coolant temperature at engine start) or at elevations 

above 8000 feet above sea level. The Executive Officer shall approve the 

request upon determining that the manufacturer has provided data and/or an 

engineering evaluation that demonstrate that monitoring during the conditions 

would be unreliable. A manufacturer may further request, and the Executive 

Officer shall approve, that an OBD system monitor be disabled at other 

ambient engine start temperatures upon determining that the manufacturer

has demonstrated with data and/or an engineering evaluation that 

misdiagnosis would occur at the ambient temperatures because of its effect 

on the component itself (e.g., component freezing).

(5.4) Manufacturers may request Executive Officer approval to disable monitoring 

systems that can be affected by low fuel level or running out of fuel (e.g., 

misfire detection) when the fuel level is 15 percent or less of the nominal 

capacity of the fuel tank. The Executive Officer shall approve the request 

upon determining that the manufacturer has submitted data and/or an 

engineering evaluation that demonstrate that monitoring at the fuel levels 

would be unreliable and the OBD system is able to detect a malfunction if the 

component(s) used to determine fuel level erroneously indicates a fuel level 

that causes the disablement. 

(5.5) Manufacturers may disable monitoring systems that can be affected by 

vehicle battery or system voltage levels. 

(5.5.1) For monitoring systems affected by low vehicle battery or system voltages, 

manufacturers may disable monitoring systems when the battery or 

system voltage is below 11.0 Volts. Manufacturers may request Executive 

Officer approval to utilize a voltage threshold higher than 11.0 Volts to 

disable system monitoring. The Executive Officer shall approve the 

request upon determining that the manufacturer has submitted data 

and/or an engineering evaluation that demonstrate that monitoring at the 

voltages would be unreliable and that either operation of a vehicle below 

the disablement criteria for extended periods of time is unlikely or the 

OBD system monitors the battery or system voltage and will detect a 

malfunction at the voltage used to disable other monitors. 

(5.5.2) For monitoring systems affected by high vehicle battery or system 

voltages, manufacturers may request Executive Officer approval to 

disable monitoring systems when the battery or system voltage exceeds a 
89

manufacturer-defined voltage. The Executive Officer shall approve the 

request upon determining that the manufacturer has submitted data 

and/or an engineering evaluation that demonstrate that monitoring above 

the manufacturer-defined voltage would be unreliable and that either the 

electrical charging system/alternator warning light is illuminated (or voltage 

gauge is in the “red zone”) or the OBD system monitors the battery or 

system voltage and will detect a malfunction at the voltage used to disable 

other monitors. 

(5.6) A manufacturer may disable affected monitoring systems in vehicles 

designed to accommodate the installation of PTO units (as defined in section 

(c)), provided disablement occurs only while the PTO unit is active, and the 

OBD readiness status is cleared by the on-board computer (i.e., all monitors 

set to indicate “not complete”) while the PTO unit is activated (see section 

(h)(4.1) below). If the disablement occurs, the readiness status may be 

restored to its state prior to PTO activation when the disablement ends. 

(5.7) Whenever the requirements in sections (e) through (g) of this regulation 

require monitoring “to the extent feasible”, the manufacturer shall submit its 

proposed monitor(s) for Executive Officer approval. The Executive Officer 

shall approve the proposal upon determining that the proposed monitor(s) 

meets the criteria of “to the extent feasible” by considering the best available 

monitoring technology to the extent that it is known or should have been 

known to the manufacturer and given the limitations of the manufacturer’s 

existing hardware, the extent and degree to which the monitoring 

requirements are met in full, the limitations of monitoring necessary to 

prevent significant errors of commission and omission, and the extent to 

which the manufacturer has considered and pursued alternative monitoring 

concepts to meet the requirements in full. The manufacturer’s consideration 

and pursuit of alternative monitoring concepts shall include evaluation of

other modifications to the proposed monitor(s), the monitored components 

themselves, and other monitors that use the monitored components (e.g., 

altering other monitors to lessen the sensitivity and reliance on the 

component or characteristic of the component subject to the proposed 

monitor(s)).

 

(h) STANDARDIZATION REQUIREMENTS 

(1) Reference Documents: 

The following Society of Automotive Engineers (SAE) and International 

Organization of Standards (ISO) documents are incorporated by reference into 

this regulation: 

(1.1) SAE J1930 "Electrical/Electronic Systems Diagnostic Terms, Definitions, 

Abbreviations, and Acronyms – Equivalent to ISO/TR 15031-2:April 30, 

2002", April 2002October 2008 (SAE J1930). 

(1.2) SAE J1962 "Diagnostic Connector – Equivalent to ISO/DIS 15031-3: 

December 14, 2001", April 2002 (SAE J1962). 

(1.3) SAE J1978 "OBD II Scan Tool – Equivalent to ISO/DIS 15031-4: December 

14, 2001", April 2002 (SAE J1978). 

(1.4) SAE J1979 "E/E Diagnostic Test Modes – Equivalent to ISO/DIS 15031-

5:April 30, 2002", April 2002May 2007 (SAE J1979). 
90

(1.5) SAE J2012 "Diagnostic Trouble Code Definitions – Equivalent to ISO/DIS 

15031-6:April 30, 2002", April 2002December 2007 (SAE J2012). 

(1.6) ISO 15765-4:20015 "Road Vehicles-Diagnostics on Controller Area Network 

(CAN) - Part 4: Requirements for emission-related systems", December 

2001January 2005 (ISO 15765-4). 

(1.7) SAE J1939 consisting of:

(1.7.1) J1939 Recommended Practice for a Serial Control and Communications 

Vehicle Network, March 2009;

(1.7.2) J1939/1 Recommended Practice for Control and Communications 

Network for On-Highway Equipment, September 2000;

(1.7.3) J1939/11 Physical Layer, 250K bits/s, Twisted Shielded Pair, September

2006;

(1.7.4) J1939/13 Off-Board Diagnostic Connector, March 2004;

(1.7.5) J1939/15 Reduced Physical Layer, 250K bits/sec, UN-Shielded Twisted 

Pair (UTP), August 2008;

(1.7.6) J1939/21 Data Link Layer, December 2006;

(1.7.7) J1939/31 Network Layer, April 2004;

(1.7.8) J1939/71 Vehicle Application Layer (Through February 2008), January

2009;

(1.7.9) J1939/73 Application Layer—Diagnostics, September 2006;

(1.7.10) J1939/81 Network Management, May 2003; and

(1.7.11) J1939/84 OBD Communications Compliance Test Cases For Heavy Duty 

Components and Vehicles, December 2008.March 2005 -“Recommended 

Practice for a Serial Control and Communications Vehicle Network” and 

the associated subparts included in SAE HS-1939, “Truck and Bus 

Control and Communications Network Standards Manual”, 2005 Edition 

(SAE J1939).

(1.8) SAE J2403 “Medium/Heavy-Duty E/E Systems Diagnosis Nomenclature,” 

August 2004 2007 (SAE J2403). 

(1.9) SAE J1699-3 – “OBD II Compliance Test Cases”, May 2006 (SAE J1699-3).

(1.10) SAE J2534-1 – “Recommended Practice for Pass-Thru Vehicle 

Programming”, December 2004 (SAE J2534-1).

(2) Diagnostic Connector: 

A standard data link connector conforming to SAE J1962 or SAE J1939-13 

specifications (except as specified in section (h)(2.3)) shall be incorporated in 

each vehicle. 

(2.1) For the 2010 through 2012 model year engines:

(2.1.1) The connector shall be located in the driver’s side foot-well region of the 

vehicle interior in the area bound by the driver’s side of the vehicle and 

the driver's side edge of the center console (or the vehicle centerline if the 

vehicle does not have a center console) and at a location no higher than 

the bottom of the steering wheel when in the lowest adjustable position. 

The connector may not be located on or in the center console (i.e., neither 

on the horizontal faces near the floor-mounted gear selector, parking 

brake lever, or cup-holders nor on the vertical faces near the car stereo, 

climate system, or navigation system controls). 
91

(2.1.2) If the connector is covered, the cover must be removable by hand without 

the use of any tools and be labeled “OBD” to aid technicians in identifying 

the location of the connector. Access to the diagnostic connector may not 

require opening or the removal of any storage accessory (e.g., ashtray, 

coinbox). The label shall be submitted to the Executive Officer for review 

and approval, at or before the time the manufacturer submits its 

certification application. The Executive Officer shall approve the label 

upon determining that it clearly identifies that the connector is located 

behind the cover and is consistent with language and/or symbols 

commonly used in the automotive industry.

(2.2) For 2013 and subsequent model year engines:

(2.2.1) The connector shall be located in the driver’s side foot-well region of the 

vehicle interior in the area bound by the driver’s side of the vehicle and 

the foot pedal closest to the driver’s side of the vehicle (left most pedal in 

a left hand drive vehicle) excluding a foot-activated emergency brake if 

equipped (e.g., typically the brake pedal for an automatic transmission 

equipped vehicle or the clutch pedal for a manual transmission equipped 

vehicle) and at a location no higher than the bottom of the steering wheel 

when in the lowest adjustable position.

(2.2.2) The connector shall be mounted in an uncovered location and may not be 

covered with or located behind any form of panel, access door, or storage 

device (e.g., fuse panel cover, hinged door, ashtray, coinbox) that requires 

opening or removal to access the connector. The connector may be 

equipped with a dust cap in the shape and size of the diagnostic 

connector for environmental protection purposes but the dust cap must be 

removable by hand without the use of any tools and be labeled “OBD” to 

aid technicians in identifying the connector.

(2.2.3) The connector shall be mounted in a manner that allows vehicle operation 

and driving (e.g., does not interfere with use of driver controls such as the 

clutch, brake, and accelerator pedal) while a scan tool is connected to the 

vehicle. 

(2.3) The location of the connector shall be capable of being easily identified and 

accessed (e.g., to connect an off-board tool). For vehicles equipped with a 

driver’s side door, the connector shall be capable of being easily identified 

and accessed by a technician standing (or “crouched”) on the ground outside 

the driver’s side of the vehicle with the driver’s side door open.

(2.3)(2.4) If the ISO 15765-4 protocol (see section (h)(3)) is used for the required 

OBD standardized functions, the connector shall meet the “Type A” 

specifications of SAE J1962. Any pins in the connector that provide electrical 

power shall be properly fused to protect the integrity and usefulness of the 

connector for diagnostic purposes and may not exceed 20.0 Volts DC 

regardless of the nominal vehicle system or battery voltage (e.g., 12V, 24V, 

42V). 

(2.4)(2.5) If the SAE J1939 protocol (see section (h)(3)) is used for the required 

OBD standardized functions, the connector shall meet the specifications of 

SAE J1939-13. Any pins in the connector that provide electrical power shall 

be properly fused to protect the integrity and usefulness of the connector for 

diagnostic purposes. 
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(2.5)(2.6) Manufacturers may equip vehicles with additional diagnostic connectors 

for manufacturer-specific purposes (i.e., purposes other than the required 

OBD functions). However, if the additional connector conforms to the “Type 

A” specifications of SAE J1962 or the specifications of SAE J1939-13 and is 

located in the vehicle interior near the required connector of section (h)(2.3)

or (2.4), the connector(s) must be clearly labeled to identify which connector 

is used to access the standardized OBD information required in section (h). 

(3) Communications to a Scan Tool: 

All OBD control modules (e.g., engine, auxiliary emission control module) on a 

single vehicle shall use the same protocol for communication of required 

emission-related messages from on-board to off-board network communications 

to a scan tool meeting SAE J1978 specifications or designed to communicate 

with an SAE J1939 network. Engine manufacturers shall not alter normal 

operation of the engine emission control system due to the presence of off-board 

test equipment accessing information required by section (h). The OBD system 

shall use one of the following standardized protocols: 

(3.1) ISO 15765-4. All required emission-related messages using this protocol 

shall use a 500 kbps baud rate. 

(3.2) SAE J1939. This protocol may only be used on vehicles with diesel engines. 

(4) Required Emission Related Functions: 

The following standardized functions shall be implemented in accordance with 

the specifications in SAE J1979 or SAE J1939 to allow for access to the required 

information by a scan tool meeting SAE J1978 specifications or designed to 

communicate with an SAE J1939 network: 

(4.1) Readiness Status: In accordance with SAE J1979/J1939-73 specifications, 

the OBD system shall indicate “complete” or “not complete” since the fault 

memory was last cleared for each of the installed monitored components and 

systems identified in sections (e)(1) through (f)(9), and (g)(3) except (e)(11) 

and (f)(4). All components or systems identified in (f)(1), (f)(2), or (g)(3) that 

are monitored continuously shall always indicate “complete”. Components or 

systems that are not subject to continuous monitoring shall immediately 

indicate “complete” upon the respective diagnostic(s) being fully executed 

and determining that the component or system is not malfunctioning. A 

component or system shall also indicate “complete” if after the requisite 

number of decisions necessary for determining MIL status has been fully 

executed, the monitor indicates a malfunction for the component or system. 

The status for each of the monitored components or systems shall indicate 

“not complete” whenever fault memory has been cleared or erased by a 

means other than that allowed in section (d)(2). Normal vehicle shut down 

(i.e., key off, engine off) may not cause the status to indicate “not complete”. 

(4.1.1) Subject to Executive Officer approval, a manufacturer may request that 

the readiness status for a monitor be set to indicate “complete” without 

monitoring having been completed if monitoring is disabled for a multiple 

number of driving cycles due to the continued presence of extreme 

operating conditions (e.g., cold ambient temperatures, high altitudes). 

Executive Officer approval shall be based on the conditions for monitoring 
93

system disablement and the number of driving cycles specified without 

completion of monitoring before readiness is indicated as “complete”. 

(4.1.2) For the evaporative system monitor, the readiness status shall be set in 

accordance with section (h)(4.1) when both the functional check of the 

purge valve and, if applicable, the leak detection monitor of the orifice size 

specified in section (f)(7.2.2)(B) (e.g., 0.150 inch) indicate that they are 

complete. 

(4.1.3) If the manufacturer elects to additionally indicate readiness status through 

the MIL in the key on, engine off position as provided for in section 

(d)(2.1.3), the readiness status shall be indicated in the following manner: 

If the readiness status for all monitored components or systems is 

“complete”, the MIL shall remain continuously illuminated in the key on, 

engine off position for at least 15-20 seconds. If the readiness status for 

one or more of the monitored components or systems is “not complete”, 

after 15-20 seconds of operation in the key on, engine off position with the 

MIL illuminated continuously, the MIL shall blink once per second for 5-10 

seconds. The data stream value for MIL status (section (h)(4.2)) shall 

indicate “commanded off” during this sequence unless the MIL has also 

been “commanded on” for a detected fault. 

(4.2) Data Stream: The following signals shall be made available on demand 

through the standardized data link connector in accordance with SAE 

J1979/J1939 specifications. The actual signal value shall always be used 

instead of a default or limp home value. 

(4.2.1) For all gasoline engines: 

(A) Calculated load value, engine coolant temperature, engine speed, vehicle 

speed, time elapsed since engine start; and 

(B) Absolute load, fuel level (if used to enable or disable any other 

diagnostics), barometric pressure (directly measured or estimated), 

engine control module system voltage, commanded equivalence ratio; 

and 

(C) Number of stored confirmed fault codes, catalyst temperature (if directly 

measured or estimated for purposes of enabling the catalyst monitor(s)), 

monitor status (i.e., disabled for the rest of this driving cycle, complete this 

driving cycle, or not complete this driving cycle) since last engine shut-off 

for each monitor used for readiness status, distance traveled (or engine 

run time for engines not utilizing vehicle speed information) while MIL 

activated, distance traveled (or engine run time for engines not utilizing 

vehicle speed information) since fault memory last cleared, and number of 

warm-up cycles since fault memory last cleared, OBD requirements to 

which the engine is certified (e.g., California OBD, EPA OBD, European 

OBD, non-OBD) and MIL status (i.e., commanded-on or commanded-off). 

(4.2.2) For all diesel engines: 

(A) Calculated load (engine torque as a percentage of maximum torque 

available at the current engine speed), driver’s demand engine torque (as 

a percentage of maximum engine torque), actual engine torque (as a 

percentage of maximum engine torque), reference engine maximum 

torque, reference maximum engine torque as a function of engine speed 

(suspect parameter numbers (SPN) 539 through 543 defined by SAE 
94

J1939 within parameter group number (PGN) 65251 for engine 

configuration), engine coolant temperature, engine oil temperature (if used 

for emission control or any OBD diagnostics), engine speed, time elapsed 

since engine start; and

(B) Fuel level (if used to enable or disable any other diagnostics), vehicle 

speed (if used for emission control or any OBD diagnostics), barometric 

pressure (directly measured or estimated), engine control module system 

voltage; and

(C) Number of stored confirmed/MIL-on fault codes, monitor status (i.e., 

disabled for the rest of this driving cycle, complete this driving cycle, or not 

complete this driving cycle) since last engine shut-off for each monitor 

used for readiness status, distance traveled (or engine run time for 

engines not utilizing vehicle speed information) while MIL activated, 

distance traveled (or engine run time for engines not utilizing vehicle 

speed information) since fault memory last cleared, number of warm-up 

cycles since fault memory last cleared, OBD requirements to which the 

engine is certified (e.g., California OBD, California OBD-child rating (i.e., 

for engines subject to (d)(7.1.2) or (d)(7.2.3)) EPA OBD, European OBD, 

non-OBD), and MIL status (i.e., commanded-on or commanded-off); 

(D) NOx NTE control area status (i.e., inside control area, outside control 

area, inside manufacturer-specific NOx NTE carve-out area, or deficiency 

active area), and PM NTE control area status (i.e., inside control area, 

outside control area, inside manufacturer-specific PM NTE carve-out area, 

or deficiency active area);

(E) For 2013 and subsequent model year engines, normalized trigger for PM 

filter regeneration, PM filter regeneration status; and

(F) For 2013 and subsequent model year engines, average distance (or 

engine run time for engines not utilizing vehicle speed information)

between PM filter regenerations.

(E)(G) For purposes of the calculated load and torque parameters in section 

(h)(4.2.2)(A), manufacturers shall report the most accurate values that are 

calculated within the applicable electronic control unit (e.g., the engine 

control module). “Most accurate values”, in this context, shall be of 

sufficient accuracy, resolution, and filtering to be used for the purposes of 

in-use emission testing with the engine still in a vehicle (e.g., using 

portable emission measurement equipment). 

(4.2.3) For all engines so equipped: 

(A) Absolute throttle position, relative throttle position, fuel control system 

status (e.g., open loop, closed loop), fuel trim, fuel pressure, ignition 

timing advance, fuel injection timing, intake air/manifold temperature, 

engine intercooler temperature, manifold absolute pressure, air flow rate 

from mass air flow sensor, secondary air status (upstream, downstream, 

or atmosphere), ambient air temperature, commanded purge valve duty 

cycle/position, commanded EGR valve duty cycle/position, actual EGR 

valve duty cycle/position, EGR error between actual and commanded, 

PTO status (active or not active), redundant absolute throttle position (for 

electronic throttle or other systems that utilize two or more sensors), 

absolute pedal position, redundant absolute pedal position, commanded 
95

throttle motor position, fuel rate, boost pressure, commanded/target boost 

pressure, turbo inlet air temperature, fuel rail pressure, commanded fuel 

rail pressure, PM filter inlet pressure, PM filter inlet temperature, PM filter 

outlet pressure, PM filter outlet temperature, PM filter delta pressure, 

exhaust pressure sensor output, exhaust gas temperature sensor output, 

injection control pressure, commanded injection control pressure, 

turbocharger/turbine speed, variable geometry turbo position, commanded 

variable geometry turbo position, turbocharger compressor inlet 

temperature, turbocharger compressor inlet pressure, turbocharger 

turbine inlet temperature, turbocharger turbine outlet temperature, 

wastegate valve position, glow plug lamp status; and

(B) For 2013 and subsequent model year engines, EGR temperature,

variable geometry turbo control status (e.g., open loop, closed loop), 

reductant level (e.g., urea tank fill level), alcohol fuel percentage, type of 

fuel currently being used, NOx adsorber regeneration status, NOx 

adsorber deSOx status, hybrid battery pack remaining charge; 

(C) Oxygen sensor output, air/fuel ratio sensor output, NOx sensor output, 

and evaporative system vapor pressure; and

(D) For 2013 and subsequent model year engines, PM sensor output and 

distance traveled while low/empty SCR reductant driver 

warning/inducement active. 

(4.3) Freeze Frame:.

(4.3.1) “Freeze frame” information required to be stored pursuant to sections 

(d)(2.2.1)(D), (d)(2.2.2)(D), (e)(1.4.2)(D), (e)(2.4.2)(B), (f)(1.4.4), and 

(f)(2.4.3) shall be made available on demand through the standardized 

data link connector in accordance with SAE J1979/J1939-73 

specifications. 

(4.3.2) “Freeze frame” conditions must include the fault code which caused the 

data to be stored and all of the signals required in sections (h)(4.2.1)(A) 

and (4.2.2)(A). Freeze frame conditions shall also include all of the 

signals required on the engine in sections (h)(4.2.1)(B), (4.2.2)(B),

(4.2.2)(E), and (4.2.3)(A), and (4.2.3)(B) that are used for diagnostic or 

control purposes in the specific diagnostic or emission-critical powertrain 

control unit that stored the fault code. 

(4.3.3) Only one frame of data is required to be recorded. Manufacturers may 

choose to store additional frames provided that at least the required frame 

can be read by a scan tool meeting SAE J1978 specifications or designed 

to communicate with an SAE J1939 network. 

(4.4) Fault Codes:

(4.4.1) For vehicles using the ISO 15765-4 protocol for the standardized functions 

required in section (h): 

(A) For all monitored components and systems, stored pending, confirmed, 

and permanent fault codes shall be made available through the diagnostic 

connector in a standardized format in accordance with SAE J1979 

specifications. Standardized fault codes conforming to SAE J2012 shall 

be employed. 

(B) The stored fault code shall, to the fullest extent possible, pinpoint the 

likely cause of the malfunction. To the extent feasible, manufacturers 
96

shall use separate fault codes for every diagnostic where the diagnostic 

and repair procedure or likely cause of the failure is different. In general, 

rationality and functional diagnostics shall use different fault codes than 

the respective circuit continuity diagnostics. Additionally, input component 

circuit continuity diagnostics shall use different fault codes for distinct 

malfunctions (e.g., out-of-range low, out-of-range high, open circuit). 

(C) Manufacturers shall use appropriate SAE-defined fault codes of SAE 

J2012 (e.g., P0xxx, P2xxx) whenever possible. With Executive Officer 

approval, manufacturers may use manufacturer-defined fault codes in 

accordance with SAE J2012 specifications (e.g., P1xxx). Factors to be 

considered by the Executive Officer for approval shall include the lack of 

available SAE-defined fault codes, uniqueness of the diagnostic or 

monitored component, expected future usage of the diagnostic or 

component, and estimated usefulness in providing additional diagnostic 

and repair information to service technicians. Manufacturer-defined fault 

codes shall be used consistently (i.e., the same fault code may not be 

used to represent two different failure modes) across a manufacturer’s 

entire product line. 

(D) A pending or confirmed fault code (as required in sections (d) and (e) 

through (g)) shall be stored and available to an SAE J1978 scan tool 

within 10 seconds after a diagnostic has determined that a malfunction 

has occurred. A permanent fault code shall be stored and available to an 

SAE J1978 scan tool no later than the end of an ignition cycle (including 

electronic control unit shutdown) in which the corresponding confirmed 

fault code causing the MIL to be illuminated has been stored. 

(E) Pending fault codes: 

(i) Pending fault codes for all components and systems (including 

continuously and non-continuously monitored components) shall be 

made available through the diagnostic connector in accordance with 

SAE J1979 specifications (e.g., Mode/Service $07). 

(ii) A pending fault code(s) shall be stored and available through the 

diagnostic connector for all currently malfunctioning monitored 

component(s) or system(s), regardless of the MIL illumination status or 

confirmed fault code status (e.g., even after a pending fault has 

matured to a confirmed fault code and the MIL is illuminated, a 

pending fault code shall be stored and available if the most recent 

monitoring event indicates the component is malfunctioning). 

(iii) Manufacturers using alternate statistical protocols for MIL illumination 

as allowed in section (d)(2.2.1)(C) shall submit to the Executive Officer 

a protocol for setting pending fault codes. The Executive Officer shall 

approve the proposed protocol upon determining that, overall, it is 

equivalent to the requirements in sections (h)(4.4.1)(E)(i) and (ii) and 

that it effectively provides service technicians with a quick and 

accurate indication of a pending failure. 

(F) Permanent fault codes: 

(i) Permanent fault codes for all components and systems shall be made 

available through the diagnostic connector in a standardized format 
97

that distinguishes permanent fault codes from both pending fault 

codes and confirmed fault codes. 

(ii) A confirmed fault code shall be stored as a permanent fault code no 

later than the end of the ignition cycle and subsequently at all times 

that the confirmed fault code is commanding the MIL on (e.g., for 

currently failing systems but not during the 40 warm-up cycle selfhealing process described in section (d)(2.3.1)(B)). 

(iii) Permanent fault codes shall be stored in NVRAM and may not be 

erasable by any scan tool command (generic or enhanced) or by 

disconnecting power to the on-board computer. 

(iv) Permanent fault codes shall bemay not be erasableed if when the 

engine control module containing the permanent fault code is 

reprogrammed unless and the readiness status (refer to section 

(h)(4.1)) for all monitored components and systems are set to “not 

complete.” in conjunction with the reprogramming event.

(v) The OBD system shall have the ability to store a minimum of four 

current confirmed fault codes as permanent fault codes in NVRAM. If 

the number of confirmed fault codes currently commanding the MIL on 

exceeds the maximum number of permanent fault codes that can be 

stored, the OBD system shall store the earliest detected confirmed 

fault codes as permanent fault codes. If additional confirmed fault 

codes are stored when the maximum number of permanent fault 

codes is already stored in NVRAM, the OBD system may not replace 

any existing permanent fault code with the additional confirmed fault 

codes. 

(4.4.2) For vehicles using the SAE J1939 protocol for the standardized functions 

required in section (h): 

(A) For all monitored components and systems, stored pending, MIL-on, and 

previously MIL-on fault codes shall be made available through the 

diagnostic connector in a standardized format in accordance with SAE 

J1939 specifications (i.e., Diagnostic Message (DM) 6, DM12, and DM23). 

 Standardized fault codes conforming to SAE J1939 shall be employed. 

(B) The stored fault code shall, to the fullest extent possible, pinpoint the 

likely cause of the malfunction. To the extent feasible, manufacturers 

shall use separate fault codes for every diagnostic where the diagnostic 

and repair procedure or likely cause of the failure is different. In general, 

rationality and functional diagnostics shall use different fault codes than 

the respective circuit continuity diagnostics. Additionally, input component 

circuit continuity diagnostics shall use different fault codes for distinct 

malfunctions (e.g., out-of-range low, out-of-range high, open circuit). 

(C) Manufacturers shall use appropriate SAE-defined fault codes of SAE 

J939 whenever possible. With Executive Officer approval, manufacturers 

may use manufacturer-defined fault codes in accordance with SAE J1939 

specifications. Factors to be considered by the Executive Officer for 

approval shall include the lack of available SAE-defined fault codes, 

uniqueness of the diagnostic or monitored component, expected future 

usage of the diagnostic or component, and estimated usefulness in 

providing additional diagnostic and repair information to service 
98

technicians. Manufacturer-defined fault codes shall be used consistently 

(i.e., the same fault code may not be used to represent two different 

failure modes) across a manufacturer’s entire product line. 

(D) A pending or MIL-on fault code (as required in sections (d), (e), and (g)) 

shall be stored and available to an SAE J1939 scan tool within 10 

seconds after a diagnostic has determined that a malfunction has 

occurred. A permanent fault code shall be stored and available to an SAE 

J1939 scan tool no later than the end of an ignition cycle (including 

electronic control unit shutdown) in which the corresponding MIL-on fault 

code causing the MIL to be illuminated has been stored. 

(E) Pending fault codes: 

(i) Pending fault codes for all components and systems (including 

continuously and non-continuously monitored components) shall be 

made available through the diagnostic connector in accordance with 

SAE J1939 specifications (i.e., DM6). 

(ii) Manufacturers using alternate statistical protocols for MIL illumination 

as allowed in section (d)(2.2.2)(C) shall submit to the Executive Officer 

a protocol for setting pending fault codes. The Executive Officer shall 

approve the proposed protocol upon determining that, overall, it is 

equivalent to the requirements in sections (h)(4.4.2)(E)(i) and that it 

effectively provides service technicians with a quick and accurate 

indication of a pending failure. 

(F) Permanent fault codes: 

(i) Permanent fault codes for all components and systems shall be made 

available through the diagnostic connector in a standardized format 

that distinguishes permanent fault codes from pending fault codes, 

MIL-on fault codes, and previously MIL-on fault codes. 

(ii) A MIL-on fault code shall be stored as a permanent fault code no later 

than the end of the ignition cycle and subsequently at all times that the 

MIL-on fault code is commanding the MIL on (e.g., for currently failing 

systems). 

(iii) Permanent fault codes shall be stored in NVRAM and may not be 

erasable by any scan tool command (generic or enhanced) or by 

disconnecting power to the on-board computer. 

(iv) Permanent fault codes shall bemay not be erasableed if when the 

engine control module containing the permanent fault codes is 

reprogrammed unlessand the readiness status (refer to section 

(h)(4.1)) for all monitored components and systems are set to “not 

complete.” in conjunction with the reprogramming event.

(v) The OBD system shall have the ability to store a minimum of four 

current MIL-on fault codes as permanent fault codes in NVRAM. If the 

number of MIL-on fault codes currently commanding the MIL on 

exceeds the maximum number of permanent fault codes that can be 

stored, the OBD system shall store the earliest detected MIL-on fault 

codes as permanent fault codes. If additional MIL-on fault codes are 

stored when the maximum number of permanent fault codes is already 

stored in NVRAM, the OBD system may not replace any existing 

permanent fault code with the additional MIL-on fault codes. 
99

(4.5) Test Results:

(4.5.1) Except as provided in section (h)(4.5.7), for all monitored components and 

systems identified in sections (e)(1) through (f)(9), results of the most 

recent monitoring of the components and systems and the test limits 

established for monitoring the respective components and systems shall 

be stored and available through the data link in accordance with the 

standardized format specified in SAE J1979 for the ISO 15765-4 protocol 

or SAE J1939. 

(4.5.2) The test results shall be reported such that properly functioning 

components and systems (e.g., “passing” systems) do not store test 

values outside of the established test limits. Test limits shall include both 

minimum and maximum acceptable values and shall be defined so that a 

test result equal to either test limit is a “passing” value, not a “failing” 

value. 

(4.5.3) The test results shall be standardized such that the name of the monitored 

component (e.g., catalyst bank 1) can be identified by a generic scan tool 

and the test results and limits can be scaled and reported with the 

appropriate engineering units by a generic scan tool. 

(4.5.4) The test results shall be stored until updated by a more recent valid test 

result or the fault memory of the OBD system computer is cleared.

(4.5.5) Upon fault memory being cleared, test results reported for monitors that 

have not yet completed with valid test results since the last time the fault 

memory was cleared shall report values of zero for the test result and test 

limits.If the OBD system fault memory is cleared, all test results shall 

report values of zero for the test result and test limits. The test results 

shall be updated once the applicable monitor has run and has valid test 

results and limits to report.

(4.5.5)All test results and test limits shall always be reported and the test results 

shall be stored until updated by a more recent valid test result or the fault 

memory of the OBD system computer is cleared.

(4.5.6) All test results and test limits shall always be reported. The OBD system 

shall store and report unique test results for each separate diagnostic. 

(4.5.7) The requirements of section (h)(4.5) do not apply to continuous gasoline 

fuel system monitoring specified under sections (f)(1.2.1)(A), (f)(1.2.1)(B), 

(f)(1.2.4), and (f)(1.2.5), gasoline exhaust gas sensor monitoring specified 

under sections (f)(8.2.1)(C) and (f)(8.2.2)(E), cold start emission reduction 

strategy monitoring, and continuous circuit monitoring, continuous out-ofrange monitoring, and diesel feedback control monitoring specified under 

sections (e)(1.2.4), (e)(3.2.4), (e)(4.2.5), (e)(6.2.2)(D), (e)(7.2.3), and 

(e)(8.2.7).

(4.6) Software Calibration Identification:

(4.6.1) Except as provided for in section (h)(4.6.3), Oon all vehicles, a single 

software calibration identification number (CAL ID) for each diagnostic or 

emission critical control unit(s) shall be made available through the 

standardized data link connector in accordance with the SAE 

J1979/J1939 specifications. 

(4.6.2) A unique CAL ID shall be used for every emission-related calibration 

and/or software set having at least one bit of different data from any other 
100

emission-related calibration and/or software set. Control units coded with 

multiple emission or diagnostic calibrations and/or software sets shall 

indicate a unique CAL ID for each variant in a manner that enables an offboard device to determine which variant is being used by the vehicle. 

Control units that utilize a strategy that will result in MIL illumination if the 

incorrect variant is used (e.g., control units that contain variants for 

manual and automatic transmissions but will illuminate the MIL if the 

variant selected does not match the type of transmission on the vehicle) 

are not required to use unique CAL IDs.

(4.6.3) Manufacturers may request Executive Officer approval to respond with 

more than one CAL ID per diagnostic or emission critical powertrain 

control unit. Executive Officer approval of the request shall be based on 

the method used by the manufacturer to ensure each control unit will 

respond to a generic scan tool with the CAL IDs in order of highest to 

lowest priority with regards to areas of the software most critical to 

emission and OBD system performance.

(4.7) Software Calibration Verification Number:

(4.7.1) All vehicles shall use an algorithm to calculate a single calibration 

verification number (CVN) that verifies the on-board computer software 

integrity for each diagnostic or emission critical electronically

reprogrammable control unit. The CVN shall be made available through 

the standardized data link connector in accordance with the SAE 

J1979/J1939 specifications. The CVN shall be capable of being used to 

determine if the emission-related software and/or calibration data are valid 

and applicable for that vehicle and CAL ID. 

(4.7.2) One CVN shall be made available for each CAL ID made available. For 

diagnostic or emission critical powertrain control units with more than one 

CAL ID, each CVN shall be output to a generic scan tool in the same 

order as the CAL IDs are output to the generic scan tool to allow the scan 

tool to match each CVN to the corresponding CAL ID.

(4.7.2)(4.7.3) Manufacturers shall submit information for Executive Officer 

approval of the algorithm used to calculate the CVN. Executive Officer 

approval of the algorithm shall be based on the complexity of the 

algorithm and the determination that the same CVN is difficult to achieve 

with modified calibration values. 

(4.7.3)(4.7.4) The CVN shall be calculated at least once per driving ignition cycle 

and stored until the CVN is subsequently updated. Except for 

immediately after a reprogramming event or a non-volatile memory clear 

or for the first 30 seconds of engine operation after a volatile memory 

clear or battery disconnect, the stored value shall be made available 

through the data link connector to a generic scan tool in accordance with 

SAE J1979/J1939 specifications. The stored CVN value may not be 

erased when fault memory is erased by a generic scan tool in accordance 

with SAE J1979/J1939 specifications or during normal vehicle shut down 

(i.e., key off, engine off). 

(4.7.4)(4.7.5) For purposes of Inspection and Maintenance (I/M) testing, 

manufacturers shall make the CVN and CAL ID combination information 

available for all vehicles in a standardized electronic format that allows for 
101

off-board verification that the CVN is valid and appropriate for a specific 

vehicle and CAL ID. The standardized electronic format is detailed in

Attachment XX of ARB Mail-Out #MSC XX-XX, Month Date, Year, 

incorporated by reference. Manufacturers shall submit the CVN and CAL 

ID information to the Executive Officer not more than 25 days after the 

close of a calendar quarter.

(4.8) Vehicle and Engine Identification Numbers: 

(4.8.1) All vehicles shall have the vehicle identification number (VIN) available in 

a standardized format through the standardized data link connector in 

accordance with SAE J1979/J1939 specifications. Only one electronic 

control unit per vehicle shall report the VIN to an SAE J1978/J1939 scan 

tool. 

(4.8.2) All 2013 and subsequent model year engines shall have the engine serial 

number (ESN) available in a standardized format through the

standardized data link connector. Only one electronic control unit per 

vehicle shall report the ESN to an SAE J1978/J1939 scan tool.

(4.8.2)(4.8.3) If the VIN or ESN is reprogrammable, all emission-related diagnostic

information identified in section (h)(4.9.1) shall be erased in conjunction 

with reprogramming of the VIN or the ESN. 

(4.9) ECU Name: For 2013 and subsequent model year engines, the name of each 

electronic control unit that responds to an SAE J1978/J1939 scan tool with a 

unique address or identifier shall be communicated in a standardized format 

in accordance with SAE J1979/J1939 (e.g., ECUNAME in Service/Mode $09, 

InfoType $0A in SAE J1979).

(4.9)(4.10) Erasure of Emission-Related Diagnostic Information: 

(4.9.1)(4.10.1) For purposes of section (h)(4.910), “emission-related diagnostic 

information” includes all the following: 

(A) Readiness status (section (h)(4.1)) 

(B) Data stream information (section (h)(4.2)) including number of stored 

confirmed/MIL-on fault codes, distance traveled while MIL activated, 

number of warm-up cycles since fault memory last cleared, and distance 

traveled since fault memory last cleared. 

(C) Freeze frame information (section (h)(4.3)) 

(D) Pending, confirmed, MIL-on, and previously MIL-on fault codes (section 

(h)(4.4.)) 

(E) Test results (section (h)(4.5)) 

(4.9.2)(4.10.2) For all vehicles, the emission-related diagnostic information shall 

be erased if commanded by a scan tool (generic or enhanced) and may 

be erased if the power to the on-board computer is disconnected. If any 

of the emission-related diagnostic information is commanded to be erased 

by a scan tool (generic or enhanced), all emission-related diagnostic 

information from all diagnostic or emission critical control units shall be 

erased. The OBD system may not allow a scan tool to erase a subset of 

the emission-related diagnostic information (e.g., the OBD system may 

not allow a scan tool to erase only one of three stored fault codes or only 

information from one control unit without erasing information from the 

other control unit(s)). 
102

(5) Tracking Requirements: 

(5.1) In-use Performance Ratio Tracking Requirements: 

(5.1.1) For each monitor required in sections (e) through (g) to separately report 

an in-use performance ratio, manufacturers shall implement software 

algorithms to report a numerator and denominator in the standardized 

format specified below and in accordance with the SAE J1979/J1939 

specifications. 

(5.1.2) Numerical Value Specifications: 

(A) For the numerator, denominator, general denominator, and ignition cycle 

counter: 

(i) Each number shall have a minimum value of zero and a maximum 

value of 65,535 with a resolution of one. 

(ii) Each number shall be reset to zero only when a non-volatile random 

access memory (NVRAM) reset occurs (e.g., reprogramming event) or, 

if the numbers are stored in keep-alive memory (KAM), when KAM is 

lost due to an interruption in electrical power to the control module 

(e.g., battery disconnect). Numbers may not be reset to zero under 

any other circumstances including when a scan tool command to clear 

fault codes or reset KAM is received. 

(iii) If either the numerator or denominator for a specific component 

reaches the maximum value of 65,535 ±2, both numbers shall be 

divided by two before either is incremented again to avoid overflow 

problems. 

(iv) If the ignition cycle counter reaches the maximum value of 65,535 ±2, 

the ignition cycle counter shall rollover and increment to zero on the 

next ignition cycle to avoid overflow problems. 

(v) If the general denominator reaches the maximum value of 65,535 ±2, 

the general denominator shall rollover and increment to zero on the 

next driving cycle that meets the general denominator definition to 

avoid overflow problems. 

(vi) If a vehicle is not equipped with a component (e.g., oxygen sensor 

bank 2, secondary air system), the corresponding numerator and 

denominator for that specific component shall always be reported as 

zero. 

(B) For the ratio: 

(i) The ratio shall have a minimum value of zero and a maximum value of 

7.99527 with a resolution of 0.000122. 

(ii) A ratio for a specific component shall be considered to be zero 

whenever the corresponding numerator is equal to zero and the 

corresponding denominator is not zero. 

(iii) A ratio for a specific component shall be considered to be the 

maximum value of 7.99527 if the corresponding denominator is zero or 

if the actual value of the numerator divided by the denominator 

exceeds the maximum value of 7.99527. 

(5.2) Engine Run Time Tracking Requirements: 

(5.2.1) For all gasoline and diesel engines, manufacturers shall implement 

software algorithms to individually track and report in a standardized 

format the engine run time while being operated in the following 
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conditions: 

(A) Total engine run time; 

(B) Total idle run time (with “idle” defined as accelerator pedal released by 

driver, vehicle speed less than or equal to one mile per hour, engine 

speed greater than or equal to 50 to 150 rpm below the normal, warmedup idle speed (as determined in the drive position for vehicles equipped 

with an automatic transmission), and PTO not active), and either vehicle 

speed less than or equal to one mile per hour or engine speed less than 

or equal to 200 rpm above normal warmed-up idle, and; 

(C) Total run time with PTO active.;

(D) For 2013 and subsequent model year diesel engines only,: 

(i) total run time with EI-AECD #1active;

(ii) total run time with EI-AECD #2 active; and so on up to

(iii) total run time with EI-AECD #n active.

(5.2.2) Numerical Value Specifications: For each counter specified in section 

(h)(5.2.1):

(A)For each counter specified in section (h)(5.2.1):

(i)(A) Each number shall be a four-byte value with a minimum value of zero, a 

resolution of one second per bit, and an accuracy of +/- ten seconds per 

driving cycle.conform to the standardized format specified in SAE

J1979/J1939.

(ii)(B) Each number shall be reset to zero only when a non-volatile memory 

reset occurs (e.g., reprogramming event). Numbers may not be reset to 

zero under any other circumstances including when a scan tool (generic 

or enhanced) command to clear fault codes or reset KAM is received. 

(iii)(C) If any of the individual counters reach the maximum value, all counters 

shall be divided by two before any are incremented again to avoid 

overflow problems. 

(iv)(D) The counters shall be made available to a generic scan tool in 

accordance with the SAE J1979/J1939 specifications and may be 

rescaled when transmitted, if required by the SAE specifications, from a 

resolution of one second per bit to no more than three minutes per bit. 

(5.2.3) Specifications of EI-AECDs

(A) For purposes of section (h)(5.2.3), the following terms shall be defined as 

follows:

(i) “Purpose” is defined as the objective of the EI-AECD when it is 

activated (e.g., EGR valve protection);

(ii) “Action” is defined as a specific component/element act that is 

commanded when the EI-AECD is activated (e.g., EGR system is 

derated);

(iii) “Parameter” is defined as a component/element (e.g., ECT, oil 

temperature) used to determine when to activate the EI-AECD; and 

(iv) “Condition” is defined as the specific characteristic/state exhibited by 

the parameter (e.g., ECT above 100 degrees Celsius) that triggers 

activation of the EI-AECD. 

(B) Each unique combination of action, parameter, and condition within a 

purpose shall be tracked as a separate EI-AECD and increment the 

timer(s) at all times the condition necessary to activate the EI-AECD is 
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present.

(i) For EI-AECDs that implement an action of variable degree based on 

the varying characteristics of a parameter (e.g., derate EGR more 

aggressively as engine oil temperature continues to increase), the EIAECD shall be tracked by incrementing two separate timers within a 

single EI-AECD (e.g., EI-AECD #1 timer 1 and EI-AECD #1 timer 2) as 

follows:

a. The first of the two timers shall be incremented whenever the EIAECD is commanding some amount of reduced emission control 

effectiveness up to but not including 75 percent of the maximum 

reduced emission control effectiveness that the EI-AECD is 

capable of commanding during in-use vehicle or engine operation.

For example, an overheat protection strategy that progressively 

derates EGR and eventually shuts off EGR as oil temperature 

increases would accumulate time for the first timer from the time 

derating of EGR begins up to the time that EGR is derated 75 

percent. As a second example, an overheat protection strategy 

that advances fuel injection timing progressively up to a maximum 

advance of 15 degrees crank angle as the engine coolant 

temperature increases would accumulate time for the first timer 

from the time advance is applied up to the time that advance 

reaches 11.25 degrees (75 percent of the maximum 15 degrees).

b. The second of the two timers shall be incremented whenever the EIAECD is commanding 75 percent or more of the maximum reduced 

emission control effectiveness that the EI-AECD is capable of 

commanding during in-use vehicle or engine operation. For 

example, the second timer for the first example EI-AECD identified 

in section (h)(5.2.3)(B)(i) would accumulate time from the time that 

EGR is derated 75 percent up to and including when EGR is 

completely shut off. For the second example EI-AECD identified in 

section (h)(5.2.3)(B)(i), the second timer would accumulate time 

from the time fuel injection timing advance is at 11.25 degrees up 

to and including the maximum advance of 15 degrees.

(C) A manufacturer may request Executive Officer approval to combine 

multiple unique actions, parameters, and/or conditions to be tracked within 

a single EI-AECD. The manufacturer shall submit a plan for combining, 

tracking, and incrementing the EI-AECD to the Executive Officer for 

approval. Executive Officer approval of the plan shall be based on the 

effectiveness and the equivalence of the incrementing plan to determine 

the amount of EI-AECD activity per condition relative to the measure of 

EI-AECD activity under section (h)(5.2.3)(B). 

(D) For EI-AECDs that are activated solely due to elevation, the timer shall be 

incremented only for the portion of EI-AECD activation when the elevation 

is below 8000 feet (e.g., the timer for an EI-AECD that is activated when 

the elevation is above 5000 feet shall be incremented only when the EIAECD is active and the elevation is below 8000 feet).

(E) For EI-AECDs that are initially activated due to engine warm-up and are 

subsequently reactivated after the engine has warmed up, the timer shall 
105

be incremented only when the EI-AECD is active after the initial engine 

warm-up (e.g., an EI-AECD that turns off an emission control at low 

engine coolant temperature would not increment the timer during initial

warm-up but would increment the timer if coolant temperature 

subsequently dropped below the low temperature and reactivated the EIAECD later in the drive cycle).

(F) If more than one EI-AECD is currently active, the timers for both EIAECDs shall accumulate time, regardless if there is overlap or 

redundancy in the commanded action (e.g., two different EI-AECDs 

independently but simultaneously commanding EGR off shall both 

accumulate time in their respective timers).

(6) Service Information: 

(6.1) Engine manufacturers shall provide the aftermarket service and repair 

industry emission-related service information as set forth in sections (h)(6.3) 

through (6.5). 

(6.2) The Executive Officer shall waive the requirements of sections (h)(6.3) 

through (6.5) upon determining that the ARB or U.S. EPA has adopted a 

service information regulation or rule that is in effect and operative and 

requires engine manufacturers to provide emission-related service 

information: 

(A) of comparable or greater scope than required under these provisions; 

(B) in an easily accessible format and in a timeframe that is equivalent to or 

exceeds the timeframes set forth below; and 

(C) at fair and reasonable cost. 

(6.3) Manufacturers shall make readily available, at a fair and reasonable price to 

the automotive repair industry, vehicle repair procedures which allow effective 

emission-related diagnosis and repairs to be performed using only the SAE 

J1978/J1939 generic scan tool and commonly available, non-microprocessor 

based tools. 

(6.4) As an alternative to publishing repair procedures required under section 

(h)(6.3), a manufacturer may publish repair procedures referencing the use of 

manufacturer-specific or enhanced equipment provided the manufacturer 

meets one of the following conditions: 

(6.4.1) makes available to the aftermarket scan tool industry the information 

needed to manufacture scan tools to perform the same emission-related 

diagnosis and repair procedures (excluding any reprogramming) in a 

comparable manner as the manufacturer-specific diagnostic scan tool,. or

(6.4.2) makes available for purchase, at a fair and reasonable price to the 

automotive repair industry, a manufacturer-specific or enhanced tool to 

perform the emission-related diagnosis and repair procedures (excluding 

any reprogramming).

(6.5) Manufacturers shall make available: 

(6.5.1) Information to utilize the test results reported as required in section 

(h)(4.5). The information must include a description of the test and test 

result, typical passing and failing values, associated fault codes with the 

test result, and scaling, units, and conversion factors necessary to convert 

the results to engineering units. 
106

(6.5.2) A generic description of each of the diagnostics used to meet the 

requirements of this regulation. The generic description must include a 

text description of how the diagnostic is performed, typical enable 

conditions, typical malfunction thresholds, typical monitoring time, fault 

codes associated with the diagnostic, and test results (section (h)(4.5)) 

associated with the diagnostic. Vehicles that have diagnostics not 

adequately represented by the typical values identified above shall be 

specifically identified along with the appropriate typical values. 

(6.5.3) Information necessary to execute each of the diagnostics used to meet 

the requirements of sections (e)(1) through (f)(9). The information must 

include either a description of sample driving patterns designed to be 

operated in-use or a written description of the conditions the vehicle 

needs to operate in to execute each of the diagnostics necessary to 

change the readiness status from “not complete” to “complete” for all 

monitors. The information shall be able to be used to exercise all 

necessary monitors in a single driving cycle as well as be able to be used 

to exercise the monitors to individually change the readiness status for 

each specific monitor from “not complete” to “complete”. 

(7) Exceptions to Standardization Requirements.

(7.1) For 2020 and subsequent model year alternate-fueled engines derived from a 

diesel-cycle engine, a manufacturer may meet the standardized requirements 

of section (h) that are applicable to diesel engines in lieu of the requirements 

applicable to gasoline engines. 

(i) MONITORING SYSTEM DEMONSTRATION REQUIREMENTS FOR 

CERTIFICATION 

(1) General. 

(1.1) Certification requires that manufacturers submit emission test data from one 

or more durability demonstration test engines (test engines). 

(1.2) The Executive Officer may approve other demonstration protocols if the 

manufacturer can provide comparable assurance that the malfunction criteria 

are chosen based on meeting the malfunction criteria requirements and that 

the timeliness of malfunction detection is within the constraints of the 

applicable monitoring requirements. 

(1.3) For flexible fuel engines capable of operating on more than one fuel or fuel 

combinations, the manufacturer shall submit a plan for providing emission 

test data to the Executive Officer for approval. The Executive Officer shall 

approve the plan if it is determined to be representative of expected in-use 

fuel or fuel combinations and provides accurate and timely evaluation of the 

monitored systems. 

(2) Selection of Test Engines: 

(2.1) Prior to submitting any applications for certification for a model year, a 

manufacturer shall notify the Executive Officer of the engine families and 

engine ratings within each family planned for that model year. The Executive 

Officer will then select the engine family(ies) and the specific engine rating 

within the engine family(ies) that the manufacturer shall use as demonstration 

test engines to provide emission test data. The selection of test vehicles for 
107

production vehicle evaluation, as specified in section (l)(2), may take place 

during this selection process. 

(2.2) Number of test engines: 

(2.2.1) For the 2010 model year, a manufacturer shall provide emission test data 

of a test engine from the OBD parent rating. 

(2.2.2) For the 2011 and 2012 model years, a manufacturer certifying one to 

seven engine families in a model year shall provide emission test data of 

a test engine from one OBD child rating. A manufacturer certifying eight 

or more engine families in a model year shall provide emission test data of 

test engines from two OBD child ratings. The Executive Officer may 

waive the requirement for submittal of data of one or more of the test 

engines if data have been previously submitted for all of the OBD parent 

and OBD child ratings. 

(2.2.3) For the 2013 and subsequent model years, a manufacturer certifying one 

to five engine families in a model year shall provide emission test data of 

a test engine from one engine rating. A manufacturer certifying six to ten 

engine families in a model year shall provide emission test data from test 

engines from two engine ratings. A manufacturer certifying eleven or 

more engine families in a model year shall provide emission test data of 

test engines from three engine ratings. The Executive Officer may waive 

the requirement for submittal of data of one or more of the test engines if 

data have been previously submitted for all of the engine ratings. 

(2.2.4) For a given model year, a manufacturer may elect to provide emission 

data of test engines from more engine ratings than required by section 

(i)(2.2.1) through (2.2.3). For each additional engine rating tested in that 

given model year, the Executive Officer shall reduce the number of engine 

ratings required for testing in one future model year under sections 

(i)(2.2.2) through (2.2.3) by one. 

(2.3) Aging and data collection of diesel test engines: 

(2.3.1) For 2010 through 2012 model year test engines, For the test engine(s), a 

manufacturer shall use an engine(s) aged for a minimum of 125 hours 

plus exhaust aftertreatment emission controls aged by an accelerated 

aging process to be representative of full useful life. Manufacturers are 

required to submit for Executive Officer approval a description of the 

accelerated aging process and/or supporting data. The Executive Officer 

shall approve the process upon determining that the submitted description 

and/or data demonstrate that the process ensures that deterioration of the 

exhaust aftertreatment emission controls is stabilized sufficiently such that 

it is representative of the manufacturer’s best estimates for the 

performance of the emission control at the end of the useful life. The 

Executive Officer may not require manufacturers to provide actual in-use 

or high mileage data to verify or validate that the aging is equivalent to full 

useful life for purposes of section (i)(2.3.1).

(2.3.2) For 2013 through 2015 model year test engines:

(A) A manufacturer shall collect emission and deterioration data from an 

actual high mileage system(s) (consisting of the engine, engine emission

controls, and aftertreatment) to validate its accelerated aging process. 

The manufacturer shall collect the data from a 2010 or newer model year 
108

system that is the most representative of system designs planned for the 

2013 model year and has a minimum actual mileage of full useful life or 

185,000 miles, whichever is lower. The manufacturer shall collect and 

report the data to ARB prior to the end of 2011. The manufacturer shall 

submit a plan for system selection, procurement, and data collection to 

the Executive Officer for approval prior to proceeding with the data 

collection. The Executive Officer shall approve the plan upon determining 

that the submitted description will result in the manufacturer gathering 

data necessary to quantify emission performance and deterioration of the 

system elements in a manner that will allow comparison to deterioration 

and performance levels achieved with the manufacturer’s accelerated 

aging process.

(B) For testing of 2013 through 2015 model year engines, a manufacturer 

shall use a system (engine, engine emission controls, and aftertreatment) 

aged by an accelerated aging process to be representative of full useful 

life. Manufacturers are required to submit for Executive Officer approval a 

description of the accelerated aging process and supporting data. The 

Executive Officer shall approve the process upon determining that the 

submitted description and data demonstrate that the aging process will 

result in a system representative of the manufacturer’s best estimates of 

the system performance at full useful life and that the manufacturer has 

utilized the data collected under section (i)(2.3.2)(A) to validate the 

correlation of the aging process to actual high mileage systems up to a 

minimum of full useful life or 185,000 miles.

(2.3.3) For 2016 and subsequent model year test engines:

(A) A manufacturer shall collect emission and deterioration data from an 

actual high mileage system(s) (consisting of the engine, engine emission 

controls, and aftertreatment) to validate its accelerated aging process. 

The manufacturer shall collect the data from a 2010 or newer model year 

system that is the most representative of system designs planned for the 

2016 model year and has a minimum actual mileage of full useful life. 

The manufacturer shall collect and report the data to ARB prior to the end 

of 2014. The manufacturer shall submit a plan for system selection, 

procurement, and data collection to the Executive Officer for approval 

prior to proceeding with the data collection. The Executive Officer shall 

approve the plan upon determining that the submitted description will 

result in the manufacturer gathering data necessary to quantify emission 

performance and deterioration of the system elements in a manner that 

will allow comparison to deterioration and performance levels achieved 

with the manufacturer’s accelerated aging process.

(B) For testing of 2016 and subsequent model year engines, a manufacturer 

shall use a system (engine, engine emission controls, and aftertreatment) 

aged by an accelerated aging process to be representative of full useful 

life. Manufacturers are required to submit for Executive Officer approval a 

description of the accelerated aging process and supporting data. The 

Executive Officer shall approve the process upon determining that the 

submitted description and data demonstrate that the aging process will 

result in a system representative of the manufacturer’s best estimates of 
109

the system performance at full useful life and that the manufacturer has 

utilized the data collected under section (i)(2.3.3)(A) to validate the 

correlation of the aging process to actual high mileage systems up to a 

minimum of full useful life.

(2.4) Aging of gasoline engines: For the test engine(s), a manufacturer shall use a 

certification emission durability test engine(s) system (i.e., consisting of the 

engine, engine emission controls, and aftertreatment), a representative high 

mileage engine(s) system, or an engine(s) system aged to the end of the full 

useful life using an ARB-approved alternative durability procedure (ADP).

(3) Required Testing: 

Except as provided below, the manufacturer shall perform single-fault testing 

based on the applicable test with the following components/systems set at their 

malfunction criteria limits as determined by the manufacturer for meeting the 

requirements of sections (e), (f), and (g) or sections (d)(7.1.2) and (d)(7.2.3) for 

extrapolated OBD systems. 

(3.1) Required testing for Diesel/Compression Ignition Engines: 

(3.1.1) Fuel System: The manufacturer shall perform a separate test for each 

malfunction limit established by the manufacturer for the fuel system 

parameters (e.g., fuel pressure, injection timing) specified in sections 

(e)(1.2.1) through (e)(1.2.3). When performing a test for a specific 

parameter, the fuel system shall be operating at the malfunction criteria 

limit for the applicable parameter only. All other parameters shall be with 

normal characteristics. In conducting the fuel system demonstration tests, 

the manufacturer may use computer modifications to cause the fuel 

system to operate at the malfunction limit if the manufacturer can 

demonstrate to the Executive Officer that the computer modifications 

produce test results equivalent to an induced hardware malfunction.

(3.1.2) Misfire Monitoring: For 2010 through 2012 model year engines, a misfire 

demonstration test is not required for diesel engines. For 2013 and 

subsequent model year engines, the manufacturer shall perform a test at 

the malfunction criteria limit specified in section (e)(2.2.2). 

(3.1.3) EGR System: The manufacturer shall perform a test at each flow, slow 

response, and cooling limit calibrated to the malfunction criteria (e.g., 2.0 

times the standard) in sections (e)(3.2.1) through (3.2.3) and (e)(3.2.5). In 

conducting the EGR cooler performance demonstration test, the EGR 

cooler(s) being evaluated shall be deteriorated to the applicable 

malfunction criteria using methods established by the manufacturer in 

accordance with section (e)(3.2.9). In conducting the EGR system slow 

response demonstration tests, the manufacturer may use computer 

modifications to cause the EGR system to operate at the malfunction limit 

if the manufacturer can demonstrate to the Executive Officer that the 

computer modifications produce test results equivalent to an induced 

hardware malfunction or that there is no reasonably feasible method to 

induce a hardware malfunction. 

(3.1.4) Boost Pressure Control System: The manufacturer shall perform a test at 

each boost, response, and cooling limit calibrated to the malfunction 

criteria (e.g., 2.0 times the FTP standard) in sections (e)(4.2.1) through 

(4.2.3) and (e)(4.2.4). In conducting the charge air undercooling 
110

demonstration test, the charge air cooler(s) being evaluated shall be 

deteriorated to the applicable malfunction criteria established by the 

manufacturer in section (e)(4.2.4) using methods established by the 

manufacturer in accordance with section (e)(4.2.8).

(3.1.5) NMHC Catalyst: The manufacturer shall perform a separate test for each 

monitored NMHC catalyst(s) (e.g., oxidation catalyst) that is used for a 

different purpose (e.g., oxidation catalyst upstream of a PM filter, NMHC 

catalyst used downstream of an SCR catalyst). The catalyst(s) being 

evaluated shall be deteriorated to the applicable malfunction criteria 

established by the manufacturer in section (e)(5.2.2)(A) and (e)(5.2.2)(B)

using methods established by the manufacturer in accordance with 

section (e)(5.2.4). For each monitored NMHC catalyst(s), the 

manufacturer shall also demonstrate that the OBD system will detect a 

catalyst malfunction with the catalyst at its maximum level of deterioration 

(i.e., the substrate(s) completely removed from the catalyst container or 

“empty” can). Emission data are not required for the empty can 

demonstration. 

(3.1.6) NOx Catalyst: The manufacturer shall perform a separate test for each 

monitored NOx catalyst(s) (e.g., SCR catalyst) that is used for a different 

purpose (e.g., passive lean NOx catalyst, SCR catalyst). The catalyst(s) 

being evaluated shall be deteriorated to the applicable malfunction criteria 

established by the manufacturer in sections (e)(6.2.1)(A)(i), 

(e)(6.2.1)(B)(i), and (e)(6.2.2)(A) using methods established by the 

manufacturer in accordance with section (e)(6.2.3). For each monitored 

NOx catalyst(s), the manufacturer shall also demonstrate that the OBD 

system will detect a catalyst malfunction with the catalyst at its maximum 

level of deterioration (i.e., the substrate(s) completely removed from the 

catalyst container or “empty” can). Emission data are not required for the 

empty can demonstration. 

(3.1.7) NOx Adsorber: The manufacturer shall perform a test using a NOx 

adsorber(s) deteriorated to the malfunction criteria in section (e)(7.2.1). 

The manufacturer shall also demonstrate that the OBD system will detect 

a NOx adsorber malfunction with the NOx adsorber at its maximum level 

of deterioration (i.e., the substrate(s) completely removed from the 

container or “empty” can). Emission data are not required for the empty 

can demonstration. 

(3.1.8) PM Filter: The manufacturer shall perform a test using a PM filter(s) 

deteriorated to each applicable malfunction criteria in sections (e)(8.2.1), 

(e)(8.2.2), and (e)(8.2.4). The manufacturer shall also demonstrate that 

the OBD system will detect a PM filter malfunction with the filter at its 

maximum level of deterioration (i.e., the filter(s) completely removed from 

the filter container or “empty” can). Emission data are not required for the 

empty can demonstration. 

(3.1.9) Exhaust Gas Sensor: The manufacturer shall perform a test for each 

exhaust gas sensor parameter calibrated to the malfunction criteria (e.g., 

2.0 times the FTP standard) in sections (e)(9.2.1)(A)(i), (e)(9.2.1)(B)(i)a. 

through b., and (e)(9.2.2)(A)(i) through (ii). When performing a test, all 

exhaust gas sensors used for the same purpose (e.g., for the same 
111

feedback control loop, for the same control feature on parallel exhaust 

banks) shall be operating at the malfunction criteria limit for the applicable 

parameter only. All other exhaust gas sensor parameters shall be with 

normal characteristics. 

(3.1.10) VVT System: The manufacturer shall perform a test at each target error 

limit and slow response limit calibrated to the malfunction criteria (e.g., 2.0 

times the FTP standard) in sections (e)(10.2.1) and (e)(10.2.2). In 

conducting the VVT system demonstration tests, the manufacturer may 

use computer modifications to cause the VVT system to operate at the 

malfunction limit if the manufacturer can demonstrate to the Executive 

Officer that the computer modifications produce test results equivalent to 

an induced hardware malfunction. 

(3.1.11) Cold Start Emission Reduction Strategy: The manufacturer shall perform 

a test at the malfunction criteria for the system or for each component 

monitored according to section (e)(11.2.2).

(3.1.11)(3.1.12) For each of the testing requirements of section (i)(3.1), if the 

manufacturer has established that only a functional check is required 

because no failure or deterioration of the specific tested system could 

result in an engine’s emissions exceeding the emission malfunction 

criteria (e.g., 2.0 times any of the applicable standards), the manufacturer 

is not required to perform a demonstration test; however the manufacturer 

is required to provide the data and/or engineering analysis used to 

determine that only a functional test of the system(s) is required. 

(3.2) Required testing for Gasoline/Spark-Ignited Engines: 

(3.2.1) Fuel System: 

(A) For engines with adaptive feedback based on the primary fuel control 

sensor(s), the manufacturer shall perform a test with the adaptive 

feedback based on the primary fuel control sensor(s) at the rich limit(s) 

and a test at the lean limit(s) established by the manufacturer in section 

(f)(1.2.1) to detect a malfunction before emissions exceed 1.5 times the 

applicable standards. 

(B) For engines with feedback based on a secondary fuel control sensor(s) 

and subject to the malfunction criteria in section (f)(1.2.1), the 

manufacturer shall perform a test with the feedback based on the 

secondary fuel control sensor(s) at the rich limit(s) and a test at the lean 

limit(s) established by the manufacturer in section (f)(1.2.1) to detect a 

malfunction before emissions exceed 1.5 times the applicable standards. 

(C) For other fuel metering or control systems, the manufacturer shall perform 

a test at the criteria limit(s). 

(D) For purposes of fuel system testing, the fault(s) induced may result in a 

uniform distribution of fuel and air among the cylinders. Non-uniform 

distribution of fuel and air used to induce a fault may not cause misfire. In 

conducting the fuel system demonstration tests, the manufacturer may 

use computer modifications to cause the fuel system to operate at the 

malfunction limit if the manufacturer can demonstrate to the Executive 

Officer that the computer modifications produce test results equivalent to 

an induced hardware malfunction. 

(3.2.2) Misfire: The manufacturer shall perform a test at the malfunction criteria 
112

limit specified in section (f)(2.2.2). 

(3.2.3) EGR System: The manufacturer shall perform a test at each flow limit 

calibrated to the malfunction criteria (e.g., 1.5 times the standard) in 

sections (f)(3.2.1) and (f)(3.2.2).

(3.2.4) Cold Start Emission Reduction Strategy: The manufacturer shall perform a 

test at the malfunction criteria for each component monitored according to 

section (f)(4.2.1)(A) or (f)(4.2.2)(B). 

(3.2.5) Secondary Air System: The manufacturer shall perform a test at each flow 

limit calibrated to the malfunction criteria in sections (f)(5.2.1) and 

(f)(5.2.2). 

(3.2.6) Catalyst: The manufacturer shall perform a test using a catalyst system 

deteriorated to the malfunction criteria in section (f)(6.2.1) using methods 

established by the manufacturer in accordance with section (f)(6.2.2). 

The manufacturer shall also demonstrate that the OBD system will detect 

a catalyst system malfunction with the catalyst system at its maximum 

level of deterioration (i.e., the substrate(s) completely removed from the 

catalyst container or “empty” can). Emission data are not required for the 

empty can demonstration. 

(3.2.7) Exhaust Gas Sensor: 

(A) The manufacturer shall perform a test with all primary exhaust gasoxygen

sensors (conventional switching sensors and wide range or universal 

sensors) used for fuel control simultaneously possessing a response rate 

deteriorated to the malfunction criteria limit in section (f)(8.2.1)(A). 

Manufacturers shall also perform a test for any other primary or secondary 

exhaust gas oxygen sensor parameter under sections (f)(8.2.1)(A) and 

(f)(8.2.2)(A) that can cause engine emissions to exceed the malfunction 

threshold (e.g., 1.5 times the applicable standards (e.g.,due to a shift in 

air/fuel ratio at which oxygen sensor switches, decreased amplitude). 

When performing additional test(s), all primary and secondary (if 

applicable) exhaust gasoxygen sensors used for emission fuel control 

shall be operating at the malfunction criteria limit for the applicable 

parameter only. All other primary and secondary exhaust gasoxygen

sensor parameters shall be with normal characteristics.

(B) For engines utilizing sensors other than oxygen sensors for primary fuel 

control (e.g., hydrocarbon sensors), the manufacturer shall submit, for 

Executive Officer approval, a demonstration test plan for performing 

testing of all of the sensor parameters that can cause engine emissions to 

exceed the malfunction threshold (e.g., 1.5 times the applicable 

standards). The Executive Officer shall approve the plan if it is 

determined that it will provide data that will assure proper performance of 

the diagnostics of the sensors, consistent with the intent of section (i).

(3.2.8) VVT System: The manufacturer shall perform a test at each target error 

limit and slow response limit calibrated to the malfunction criteria (e.g., 1.5 

times the FTP standard) in sections (f)(9.2.1) and (f)(9.2.2). In conducting 

the VVT system demonstration tests, the manufacturer may use computer 

modifications to cause the VVT system to operate at the malfunction limit 

if the manufacturer can demonstrate to the Executive Officer that the 

computer modifications produce test results equivalent to an induced 
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hardware malfunction. 

(3.2.9) For each of the testing requirements of section (i)(3.2), if the manufacturer 

has established that only a functional check is required because no failure 

or deterioration of the specific tested system could result in an engine’s 

emissions exceeding the emission malfunction criteria (e.g., 1.5 times any 

of the applicable standards), the manufacturer is not required to perform a 

demonstration test; however the manufacturer is required to provide the 

data and/or engineering analysis used to determine that only a functional 

test of the system(s) is required. 

(3.3) Required Testing for All Engines: 

(3.3.1) Other Emission Control Systems: The manufacturer shall conduct 

demonstration tests for all other emission control components (e.g., 

hydrocarbon traps, adsorbers) designed and calibrated to an emission 

threshold malfunction criteria (e.g., 1.5 times the applicable emission 

standards) under the provisions of section (g)(4). 

(3.3.2) For each of the testing requirements of section (i)(3.3), if the manufacturer 

has established that only a functional check is required because no failure 

or deterioration of the specific tested system could result in an engine’s 

emissions exceeding the emission malfunction criteria (e.g., 1.5 times any 

of the applicable standards), the manufacturer is not required to perform a 

demonstration test; however the manufacturer is required to provide the 

data and/or engineering analysis used to determine that only a functional 

test of the system(s) is required. 

(3.4) The manufacturer may electronically simulate deteriorated components if the 

manufacturer can demonstrate to the Executive Officer that the computer 

modifications produce test results equivalent to an induced hardware 

malfunction but may not make any engine control unit modifications (unless 

otherwise provided above or exempted pursuant to this section) when 

performing demonstration tests. All equipment necessary to duplicate the 

demonstration test must be made available to the ARB upon request. A 

manufacturer may request Executive Officer approval to electronically 

simulate a deteriorated component with engine control unit modifications. 

 The Executive Officer shall approve the request upon determining the 

manufacturer has submitted data and/or engineering analysis demonstrating 

that is technically infeasible, very difficult, and/or resource intensive to implant 

the fault with modifications external to the engine control unit.

(3.5) For each of the testing requirements of (i)(3), when performing a test, all 

components or systems used in parallel for the same purpose (e.g., separate 

VVT actuators on the intake valves for Bank 1 and Bank 2, separate NOx 

converting catalysts on parallel exhaust banks) shall be simultaneously 

deteriorated to the malfunction criteria limit. Components or systems in 

series or used for different purposes (e.g., upstream and downstream 

exhaust gas sensors in a single exhaust bank, separate high pressure and 

low pressure EGR systems) may not be simultaneously deteriorated to the 

malfunction criteria limit. 

(4) Testing Protocol: 

(4.1) Preconditioning: .The manufacturer may request Executive Officer approval 

to shall use a an applicable cycle for preconditioning cycle test engines prior 
114

to conducting each of the above emission tests. The Executive Officer shall 

approve the request Uupon determining that a manufacturer has provided 

data and/or engineering evaluation that demonstrate that additional the 

preconditioning is necessary to stabilize the emission control system. The 

manufacturer may also request Executive Officer approval to use an 

additional identical preconditioning cycle following a 20 minute hot soak after 

the initial preconditioning cycle. , tThe Executive Officer shall approve the 

request upon determining that a manufacturer has provided data and/or 

engineering evaluation that demonstrate that the additional preconditioning is 

necessary to stabilize the emission control systemallow the manufacturer to 

perform a single additional preconditioning cycle, identical to the initial 

preconditioning cycle following a 20 minute hot soak after the initial 

preconditioning cycle. . The manufacturer may not require the test engine to

be cold soaked prior to conducting preconditioning cycles in order for the 

monitoring system testing to be successful. If a second preconditioning cycle 

is permitted, the manufacturer may adjust the system or component to be 

tested before conducting the second preconditioning cycle. The 

manufacturer may not replace, modify, or adjust the system or component 

after the last preconditioning cycle has taken place.

(4.2) Test Sequence: 

(4.2.1) The manufacturer shall set the system or component on the test engine 

for which detection is to be tested at the criteria limit(s) prior to conducting 

the applicable preconditioning cycle(s)emission test (or preconditioning, if 

approved). If a second preconditioning cycle is permitted in accordance 

with section (i)(4.1) above, the manufacturer may adjust the system or 

component to be tested before conducting the second preconditioning 

cycle. The manufacturer may not replace, modify, or adjust the system or 

component after the last preconditioning cycle has taken place.

(4.2.2) After preconditioning, tThe test engine shall be operated over the first 

engine start of the applicable FTP emission test (i.e., the cold start) cycle 

or a SET cycle to allow for the initial detection of the tested system or 

component malfunction. If required by the designated monitoring 

strategy, an additional cold soak and first engine start of the FTP cycle 

(i.e., the cold start) may be performed prior to conducting this test cycle

(e.g., for two-trip monitors that only run during cold starts). This test cycle 

may be omitted from the testing protocol if it is unnecessary. If required 

by the designated monitoring strategy, a cold soak may be performed 

prior to conducting this test cycle.

(4.2.3) The test engine shall then be operated over the applicable second engine 

start of the FTP exhaust emission test (i.e., the hot start) or an SET 

emission test. The second SET cycle may be omitted from the testing

protocol if it is unnecessary (e.g., one-trip fault detection strategies that 

run on the SET).

(4.3) Test Data Collection: 

(4.3.1) During the test sequence of section (i)(4.2), the manufacturer shall collect 

data immediately prior to each engine shut-down (e.g., the end of each 

preconditioning cycle in section (i)(4.2.1), the end of the cold start FTP 

cycle in section (i)(4.2.3), the end of the warm start FTP cycle in section 
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(i)(4.2.3)). If the data cannot be collected immediately prior to engine 

shut-down, the data shall be collected immediately after engine shutdown.

(4.3.2) The manufacturer shall be required to collect the following data:

(A) Approximate time on the test cycle (in seconds after engine start) when 

the MIL illuminates (e.g., MIL illuminated at 402 seconds into the cold start 

FTP cycle);

(B) All data required by sections (h)(4.1) through (h)(4.9) and (h)(5) including 

readiness status, current data stream values, fault code(s), freeze frame 

data, test results, CAL ID, CVN, VIN, ESN, ECU Name, in-use 

performance ratios, and engine run time tracking data.

(4.4) A manufacturer required to test more than one test engine (section (i)(2.2)) 

may utilize internal calibration sign-off test procedures (e.g., forced cool 

downs, less frequently calibrated emission analyzers) instead of official test 

procedures to obtain the emission test data required in section (i) for all but 

one of the required test engines. The manufacturer may elect this option if 

the data from the alternative test procedure are representative of official 

emission test results. Manufacturers using this option are still responsible for 

meeting the malfunction criteria specified in sections (e) through (g) when 

emission tests are performed in accordance with official test procedures. 

(4.4)(4.5) A manufacturer may request Executive Officer approval to utilize an 

alternate testing protocol for demonstration of MIL illumination if the engine 

dynamometer emission test cycle does not allow all of a monitor’s enable 

conditions to be satisfied. A manufacturer may request the use of an 

alternate engine dynamometer test cycle or the use of chassis testing to 

demonstrate proper MIL illumination. In evaluating the manufacturer's 

request, the Executive Officer shall consider the technical necessity for using 

an alternate test cycle and the degree to which the alternate test cycle 

demonstrates that in-use operation with the malfunctioning component will 

properly result in MIL illumination. 

(5) Evaluation Protocol: 

(5.1) Full OBD engine ratings subject to sections (d)(7.1.1), (d)(7.2.2), or (d)(7.3) 

shall be evaluated according to the following protocol. 

(5.1.1) For all tests conducted under section (i), the MIL shall be illuminated upon 

detection of the tested system or component malfunction before the end 

of the first engine start portion of the exhaust emission test specified in 

(i)(4.2.3)of the complete applicable test in accordance with the 

requirements of sections (e) through (g). 

(5.1.2) If the MIL illuminates prior to emissions exceeding the applicable 

malfunction criteria specified in sections (e) through (g), no further 

demonstration is required. With respect to the misfire monitor 

demonstration test, if a manufacturer has elected to use the minimum 

misfire malfunction criteria of one percent as allowed in sections 

(e)(2.2.2)(A) and (f)(2.2.2)(A), no further demonstration is required if the 

MIL illuminates with misfire implanted at the malfunction criteria limit. 

(5.1.3) If the MIL does not illuminate when the system or component is set at its 

limit(s), the criteria limit or the OBD system is not acceptable. 

(A) Except for testing of the catalyst (i.e., components monitored under 
116

sections (e)(5.2.2), (e)(6.2.1), (e)(7.2.1), and (f)(6.2.1)) or PM filter system

(i.e., (e)(8.2.1) and (e)(8.2.4)), if the MIL first illuminates after emissions 

exceed the applicable malfunction criteria specified in sections (e) through 

(g), the test engine shall be retested with the tested system or component 

adjusted so that the MIL will illuminate before emissions exceed the 

applicable malfunction criteria specified in sections (e) through (g). If the 

component cannot be adjusted to meet this criterion because a default 

fuel or emission control strategy is used when a malfunction is detected 

(e.g., open loop fuel control used after an oxygen sensor malfunction is 

determined), the test engine shall be retested with the component 

adjusted to the worst acceptable limit (i.e., the applicable monitor 

indicates the component is performing at or slightly better than the 

malfunction criteria). When tested with the component adjusted to the 

worst acceptable limit, the MIL must not illuminate during the test and the 

engine emissions must be below the applicable malfunction criteria 

specified in sections (e) through (g). 

(B) In testing the catalyst (i.e., components monitored under sections 

(e)(5.2.2), (e)(6.2.1), (e)(7.2.1), and (f)(6.2.1)) or PM filter system (i.e., 

(e)(8.2.1) and (e)(8.2.4)), if the MIL first illuminates after emissions exceed 

the applicable emission threshold(s) specified in sections (e) and (f), the 

tested engine shall be retested with a less deteriorated catalyst/PM filter 

system (i.e., more of the applicable engine out pollutants are converted or 

trapped). For the OBD system to be approved, testing shall be continued 

until either of the following conditions are satisfied: 

(i) The MIL is illuminated and emissions do not exceed the thresholds 

specified in sections (e) or (f); or 

(ii) The manufacturer demonstrates that the MIL illuminates within the 

upper and lower limits of the threshold identified below. The 

manufacturer shall demonstrate acceptable limits by continuing testing 

until the test results show: 

a. The MIL is illuminated and emissions exceed the thresholds 

specified in sections (e) or (f) by 10 percent or less of the 

applicable standard (e.g., emissions are less than 1.85 times the 

applicable standard for a malfunction criterion of 1.75 times the 

standard); and 

b. The MIL is not illuminated and emissions are below the thresholds 

specified in sections (e) or (f) by no more than 20 percent of the 

standard (e.g., emissions are between 1.55 and 1.75 times the 

applicable standard for a malfunction criterion of 1.75 times the 

standard). 

(5.1.4) If an OBD system is determined unacceptable by the above criteria, the 

manufacturer may recalibrate and retest the system on the same test 

engine. In such a case, the manufacturer must confirm, by retesting, that 

all systems and components that were tested prior to recalibration and are 

affected by the recalibration function properly under the OBD system as 

recalibrated. 

(5.2) OBD child ratings subject to sections (d)(7.1.2) or (d)(7.2.3) (i.e., extrapolated 

OBD) shall be evaluated according to the following protocol. 
117

(5.2.1) For all tests conducted under section (i), the MIL shall be illuminated upon 

detection of the tested system or component malfunction before the end 

of the first engine start portion of the exhaust test emission test of the 

complete applicable test specified in (i)(4.2.3) in accordance with the 

malfunction criteria established by the manufacturer under sections 

(d)(7.1.2) and (d)(7.2.3).

(5.2.2) Except for testing of the catalyst or PM filter system, if the MIL first 

illuminates after the tested component or system significantly exceeds the 

applicable malfunction criteria established by the manufacturer, the test 

engine shall be retested with the tested system or component adjusted so 

that the MIL will illuminate at the applicable malfunction criteria 

established by the manufacturer.

(5.2.3) In testing the catalyst or PM filter system, if the MIL first illuminates after 

the tested component or system significantly exceeds the applicable 

malfunction criteria established by the manufacturer, the tested engine 

shall be retested with a less deteriorated catalyst/PM filter system (i.e., 

more of the applicable engine out pollutants are converted or trapped). 

For the OBD system to be approved, testing shall be continued until either 

of the following conditions are satisfied: 

(A) The MIL is illuminated and the tested component or system is at the 

applicable malfunction criteria established by the manufacturer; or 

(B) The manufacturer demonstrates that the MIL illuminates within the upper 

and lower limits of the threshold identified below. The manufacturer shall 

demonstrate acceptable limits by continuing testing until the test results 

show: 

(i) The MIL is illuminated and monitoring results indicate the tested 

component or system exceeds the malfunction criteria established by 

the manufacturer by 10 percent or less of the monitored parameter; 

and 

(ii) The MIL is not illuminated and monitoring results indicate the tested 

component or system is below the malfunction criteria established by 

the manufacturer by 10 percent or less of the monitored parameter. 

(6) Confirmatory Testing: 

(6.1) The ARB may perform confirmatory testing to verify the emission test data 

submitted by the manufacturer under the requirements of section (i) comply 

with the requirements of section (i) and the malfunction criteria identified in 

sections (e) through (g). This confirmatory testing is limited to the engine 

rating represented by the demonstration engine(s). 

(6.2) The ARB or its designee may install appropriately deteriorated or 

malfunctioning components (or simulate a deteriorated or malfunctioning 

component) in an otherwise properly functioning test engine of an engine 

rating represented by the demonstration test engine(s) in order to test any of 

the components or systems required to be tested in section (i). Upon request 

by the Executive Officer, the manufacturer shall make available an engine 

and all test equipment (e.g., malfunction simulators, deteriorated 

components) necessary to duplicate the manufacturer’s testing. The 

Executive Officer shall make the request within six months of reviewing and 

approving the demonstration test engine data submitted by the manufacturer 
118

for the specific engine rating. 

(j) CERTIFICATION DOCUMENTATION 

(1) When submitting an application for certification of an engine, the manufacturer 

shall submit the following documentation. If any of the items listed below are 

standardized for all of a manufacturer’s engines, the manufacturer may, for each 

model year, submit one set of documents covering the standardized items for all 

of its engines. 

(1.1) For the required documentation not standardized across all engines, the 

manufacturer may propose to the Executive Officer that it be allowed to 

submit documentation for certification from one engine that is representative 

of other engines. The Executive Officer shall approve the engine as 

representative if the engine possesses the most stringent emission standards 

and OBD monitoring requirements and covers all of the emission control 

devices for the engines covered by the submitted documentation. Upon 

approval, this grouping shall be known as an “OBD certification 

documentation group”. 

(1.2) With Executive Officer approval, one or more of the documentation 

requirements of section (j) may be waived or modified if the information 

required would be redundant or unnecessarily burdensome to generate. 

(1.3) To the extent possible, the certification documentation shall use SAE J1930 

or J2403 terms, abbreviations, and acronyms. 

(2) The following information shall be submitted as part of the certification 

application. Except as provided below for demonstration data, the Executive 

Officer will not issue an Executive Order certifying the covered engines without 

the information having been provided. The information must include: 

(2.1) A description of the functional operation of the OBD system including a 

complete written description for each monitoring strategy that outlines every 

step in the decision-making process of the monitor. Algorithms, diagrams, 

samples of data, and/or other graphical representations of the monitoring 

strategy shall be included where necessary to adequately describe the 

information. 

(2.2) A table, in the standardized format detailed in Attachment A XX of ARB MailOut #95-20XX-XX, May 22, 1995 Month Date, Year, incorporated by 

reference. 

(2.2.1) The table must include the following information for each monitored 

component or system (either computer-sensed or -controlled) of the 

emission control system: 

(A) Corresponding fault code 

(B) Monitoring method or procedure for malfunction detection 

(C) Primary malfunction detection parameter and its type of output signal 

(D) Fault criteria limits used to evaluate output signal of primary parameter 

(E) Other monitored secondary parameters and conditions (in engineering 

units) necessary for malfunction detection 

(F) Monitoring time length and frequency of checks 

(G) Criteria for storing fault code 

(H) Criteria for illuminating malfunction indicator light 
119

(I) Criteria used for determining out-of-range values and input component 

rationality checks 

(2.2.2) Wherever possible, the table shall use the following engineering units: 

(A) Degrees Celsius (°C) for all temperature criteria 

(B) KiloPascals (KPa) for all pressure criteria related to manifold or 

atmospheric pressure 

(C) Grams (g) for all intake air mass criteria 

(D) Pascals (Pa) for all pressure criteria related to evaporative system vapor 

pressure 

(E) Miles per hour (mph) for all vehicle speed criteria 

(F) Relative percent (%) for all relative throttle position criteria (as defined in 

SAE J1979/J1939) 

(G) Voltage (V) for all absolute throttle position criteria (as defined in SAE 

J1979/J1939) 

(H) Per crankshaft revolution (/rev) for all changes per ignition event based 

criteria (e.g., g/rev instead of g/stroke or g/firing) 

(I) Per second (/sec) for all changes per time based criteria (e.g., g/sec) 

(J) Percent of nominal tank volume (%) for all fuel tank level criteria 

(2.3) A logic flowchart describing the step-by-step evaluation of the enable criteria 

and malfunction criteria for each monitored emission-related component or 

system. 

(2.4) Emission test data, a description of the testing sequence (e.g., the number 

and types of preconditioning cycles), approximate time (in seconds) of MIL 

illumination during the test, fault code(s) and freeze frame information stored 

at the time of detection, corresponding test results (e.g. SAE J1979 

Mode/Service $06, SAE J1939 Diagnostic Message 8 (DM8)) stored during 

the testthe data required to be collected in section (i)(4.3), and a description 

of the modified or deteriorated components used for fault simulation with 

respect to the demonstration tests specified in section (i). The freeze frame 

data are not required for engines subject to sections (d)(7.1.2) or (d)(7.2.3). 

The Executive Officer may approve conditional certification of an engine prior 

to the submittal of this data for ARB review and approval. Factors to be 

considered by the Executive Officer in approving the late submission of 

information identified in section (j)(2.4) shall include the reason for the delay 

in the data collection, the length of time until data will be available, and the 

demonstrated previous success of the manufacturer in submitting the data 

prior to certification. 

(2.5) For gasoline engines, data supporting the misfire monitor, including: 

(2.5.1) The established percentage of misfire that can be tolerated without 

damaging the catalyst over the full range of engine speed and load 

conditions. 

(2.5.2) Data demonstrating the probability of detection of misfire events of the 

misfire monitoring system over the full engine speed and load operating 

range for the following misfire patterns: random cylinders misfiring at the 

malfunction criteria established in section (f)(2.2.2), one cylinder 

continuously misfiring, and paired cylinders continuously misfiring. 

(2.5.3) Data identifying all disablement of misfire monitoring that occurs during 

the FTP. For every disablement that occurs during the cycles, the data 
120

should identify: when the disablement occurred relative to the driver’s 

trace, the number of engine revolutions that each disablement was 

present for, and which disable condition documented in the certification 

application caused the disablement. 

(2.5.4) Manufacturers are not required to use the durability demonstration engine 

to collect the misfire data for sections (j)(2.5.1) through (2.5.3). 

(2.6) Data supporting the limit for the time between engine starting and attaining 

the designated heating temperature for after-start heated catalyst systems. 

(2.7) Data supporting the criteria used to detect a malfunction of the fuel system, 

EGR system, boost pressure control system, catalyst, NOx adsorber, PM 

filter, cold start emission reduction strategy, secondary air, evaporative 

system, VVT system, exhaust gas sensors, and other emission controls 

which causes emissions to exceed the applicable malfunction criteria 

specified in sections (e), (f), and (g). For diesel engine monitors in sections 

(e) and (g) that are required to indicate a malfunction before emissions 

exceed an emission threshold based on any applicable standard (e.g., 1.5 

times any of the applicable standards), the test cycle and standard 

determined by the manufacturer to be the most stringent for each applicable 

monitor in accordance with section (d)(6.1) and the adjustment factors 

determined by the manufacturer for each applicable monitor in accordance 

with section (d)(6.2). 

(2.8) A listing of all electronic powertrain input and output signals (including those 

not monitored by the OBD system) that identifies which signals are monitored 

by the OBD system. For input and output signals that are monitored as 

comprehensive components, the listing shall also identify the specific fault 

code for each malfunction criteria (e.g., out of range low, out of range high, 

open circuit, rationality low, rationality high). 

(2.9) A written description of all parameters and conditions necessary to begin 

closed-loop/feedback control of emission control systems (e.g., fuel system, 

boost pressure, EGR flow, SCR reductant delivery, PM filter regeneration, 

fuel system pressure). 

(2.10) A written identification of the communication protocol utilized by each engine 

for communication with an SAE J1978/J1939 scan tool. 

(2.11) A pictorial representation or written description of the diagnostic connector 

location including any covers or labels. 

(2.12) A written description of the method used by the manufacturer to meet the 

requirements of section (g)(2) for CV system monitoring including diagrams or 

pictures of valve and/or hose connections. 

(2.13) A written description of each AECD utilized by the manufacturer including the 

sensor signals and/or calculated values used to invoke each AECD, the 

engineering data and/or analysis demonstrating the need for such an AECD, 

the actions taken when each AECD is activated, the expected in-use 

frequency of operation of each AECD, and the expected emission impact 

from each AECD activation, and ,. for diesel engines, the identification of 

each AECD that has been determined by the manufacturer to be an EI-AECD 

and the assignment by the manufacturer to the data required to be tracked 

and reported in the standardized format specified in section (h)(6) (e.g., the 

AECD of “engine overheat protection as determined by coolant temperature 
121

greater than...” is an EI-AECD and is reported as EI-AECD #1 to a generic 

scan tool).

(2.14) A written description of each NOx and PM NTE deficiency and emission 

carve-out utilized by the manufacturer including the sensor signals and/or 

calculated values used to invoke each NTE deficiency or carve-out, the 

engineering data and/or analysis demonstrating the need for such an NTE 

deficiency or carve-out, the actions taken when each NTE deficiency or 

carve-out is activated, the expected in-use frequency of operation of each 

NTE deficiency or carve-out, and the expected emission impact from each 

NTE deficiency or carve-out activation. 

(2.15) Build specifications provided to engine purchasers or chassis manufacturers 

detailing all specifications or limitations imposed on the engine purchaser 

relevant to OBD requirements or emission compliance (e.g., allowable MIL 

locations, connector location specifications, cooling system heat rejection 

rates). A description of the method or copies of agreements used to ensure 

engine purchasers or chassis manufacturers will comply with the OBD and 

emission relevant build specifications (e.g., signed agreements, required 

audit/evaluation procedures). 

(2.16) A cover letter identifying all concerns and deficiencies applicable to the 

equivalent previous model year engine and the changes and/or resolution of 

each concern or deficiency for the current model year engine.

(2.17) A checklist of all the malfunction criteria in sections (e) or (f) and the 

corresponding diagnostic noted by fault code for each malfunction criterion. 

The formats of the checklists are detailed in Attachments XX and XX of ARB 

Mail-Out #MSC XX-XX, Month Date, Year, incorporated by reference. 

(2.18) Any other information determined by the Executive Officer to be necessary to 

demonstrate compliance with the requirements of this regulation. 

(k) DEFICIENCIES 

(1) The Executive Officer, upon receipt of an application from the manufacturer, may 

certify OBD systems installed on engines even though the systems do not 

comply with one or more of the requirements of title 13, CCR section 1971.1. In 

granting the certification, the Executive Officer shall consider the following 

factors: the extent to which the requirements of section 1971.1 are satisfied 

overall based on a review of the engine applications in question, the relative 

performance of the resultant OBD system compared to systems fully compliant 

with the requirements of section 1971.1, and a demonstrated good-faith effort on 

the part of the manufacturer to: (1) meet the requirements in full by evaluating 

and considering the best available monitoring technology; and (2) come into 

compliance as expeditiously as possible. 

(2) For 2013 and subsequent model year engines, manufacturers of OBD systems 

for which deficiencies have been granted are subject to fines pursuant to section 

43016 of the California Health and Safety Code. The specified fines apply to: (1) 

the third and subsequently identified deficiency(ies), ordered according to section 

(k)(3), and (2) a monitoring system deficiency where a required monitoring 

strategy is completely absent from the OBD system. 

(3) The fines for engines specified in section (k)(2) above are in the amount of $50 

per deficiency per engine for non-compliance with any of the monitoring 
122

requirements specified in sections (e), (f), and (g)(4), and $25 per deficiency per 

engine for non-compliance with any other requirement of section 1971,1. In 

determining the identified order of deficiencies, deficiencies subject to a $50 fine 

are identified first. Total fines per engine under section (k) may not exceed $500 

per engine and are payable to the State Treasurer for deposit in the Air Pollution 

Control Fund. 

(4) Manufacturers must re-apply for Executive Officer approval of a deficiency each 

model year. In considering the request to carry-over a deficiency, the Executive 

Officer shall consider the factors identified in section (k)(1) including the 

manufacturer’s progress towards correcting the deficiency. The Executive 

Officer may not allow manufacturers to carry over monitoring system deficiencies 

for more than two model years unless it can be demonstrated that substantial 

engine hardware modifications and additional lead time beyond two years would 

be necessary to correct the deficiency, in which case the Executive Officer shall 

allow the deficiency to be carried over for three model years. 

(5) Except as allowed in section (k)(6), deficiencies may not be retroactively granted 

after certification. 

(6) Request for retroactive deficiencies 

(6.1) During the first 6 months after commencement of normal production, 

manufacturers may request that the Executive Officer grant a deficiency and 

amend an engine’s certification to conform to the granting of the deficiencies 

for each aspect of the monitoring system: (a) identified by the manufacturer 

(during testing required by section (l)(2) or any other testing) to be functioning 

different than the certified system or otherwise not meeting the requirements 

of any aspect of section 1971.1; and (b) reported to the Executive Officer. If 

the Executive Officer grants the deficiencies and amended certification, their 

approval would be retroactive to the start of production. 

(6.2) Executive Officer approval of the request for a retroactive deficiency shall be 

granted provided that the conditions necessary for a pre-certification 

deficiency determination are satisfied (see section (k)(1)) and the 

manufacturer could not have reasonably anticipated the identified problem 

before commencement of production. 

(6.3) In granting the amended certification, the Executive Officer shall include any 

approved post-production deficiencies together with all previously approved 

deficiencies in computing fines in accordance with section (k)(2). 

(l) PRODUCTION ENGINE/VEHICLE EVALUATION TESTING 

(1) Verification of Standardized Requirements. 

(1.1) Requirement: Manufacturers shall perform testing to verify that 2013 and 

subsequent model year production vehicles meet the requirements of section 

(h)(3) and (h)(4) relevant to proper communication of required emissionrelated messages to an SAE J1978/J1939 scan tool. 

(1.2) Selection of Test Vehicles: 

(1.2.1) Engine manufacturers shall perform this testing every model year on ten 

unique production vehicles (i.e., engine rating and chassis application 

combination) per engine family. If there are less than ten unique 

production vehicles for a certain engine family, the manufacturer shall test 

each unique production vehicle in that engine family. Manufacturers shall 
123

perform this testing within either three months of the start of engine 

production or one month of the start of vehicle production, whichever is 

later. Manufacturers may request Executive Officer approval to group 

multiple production vehicles together and test one representative vehicle 

per group. The Executive Officer shall approve the request upon finding 

that the software and hardware designed to comply with the 

standardization requirements of section (h) (e.g., communication protocol 

message timing, number of supported data stream parameters, engine 

and vehicle communication network architecture) in the representative 

vehicle are identical to all others in the group and that any differences in 

the production vehicles are not relevant with respect to meeting the 

criteria in section (l)(1.4). 

(1.2.2) For 2016 and subsequent model year engines, the Executive Officer shall 

reduce the maximum required number of vehicles to be tested from ten 

per engine family to five per engine family for a manufacturer based on 

the demonstrated previous success of the manufacturer to meet the 

requirements of section (l)(1). For purposes of this requirement, a 

manufacturer shall be determined to be successful in meeting the 

requirements of section (l)(1) if zero vehicles fail the testing required by 

section (l)(1) for two consecutive years. 

(1.2.3) For 2019 and subsequent model year engines, the Executive Officer shall 

further reduce the maximum required number of vehicles to be tested to 

three per engine family for a manufacturer based on the demonstrated 

previous success of the manufacturer to meet the requirements of section 

(l)(1). For purposes of this requirement, a manufacturer shall be 

determined to be successful in meeting the requirements of section (l)(1) if 

zero vehicles fail the testing required by section (l)(1) for three 

consecutive years. 

(1.2.4) The Executive Officer may waive the requirement for submittal of data 

from one or more of the production vehicles if data have been previously 

submitted for all of the production vehicles. Manufacturers may request 

Executive Officer approval to carry over data collected in previous model 

years. The Executive Officer shall approve the request upon finding that 

the software and hardware designed to comply with the standardization 

requirements of section (h) are identical to the previous model year and 

no other hardware or software changes that affect compliance with the 

standardization requirements have been made. 

(1.3) Test Equipment: For the testing required in section (l)(1), manufacturers shall 

utilize an off-board device to conduct the testing. Prior to conducting testing, 

manufacturers are required to request and receive Executive Officer approval 

of the off-board device that the manufacturer will use to perform the testing.

(1.3.1) For vehicles using the ISO 15765-4 protocol for the standardized functions 

required in section (h), the Executive Officer shall approve the request 

upon determining that the manufacturer has submitted data, 

specifications, and/or engineering analysis that demonstrate that the offboard device meets the minimum requirements to conduct testing 

according to SAE J1699-3 using the software developed and maintained 

for the SAE J1699-3 committee and available through
124

www.sourceforge.net and SAE J2534 compliant hardware configured 

specifically for SAE J1699-3 testing.

(1.3.2) For vehicles using the SAE J1939 protocol for the standardized functions 

required in section (h), Tthe Executive Officer shall approve the request 

upon determining that the manufacturer has submitted data, 

specifications, and/or engineering analysis that demonstrate that the offboard device is able to verify that vehicles tested are able to perform all of 

the required functions in section (l)(1.4) with any other off-board device 

designed and built in accordance with the SAE J1978/J1939 generic scan 

tool specifications. 

(1.4) Required Testing: 

(1.4.1) The testing shall verify that communication can be properly established 

between all emission-related on-board computers and any SAE 

J1978/J1939 scan tool designed to adhere strictly to the communication 

protocols allowed in section (h)(3); 

(1.4.2) The testing shall verify that all emission-related information is properly 

communicated between all emission-related on-board computers and any 

SAE J1978/J1939 scan tool in accordance with the requirements of 

section (h) and the applicable ISO and SAE specifications including 

specifications for physical layer, network layer, message structure, and 

message content. 

(1.4.3) The testing shall further verify that the following information can be 

properly communicated to any SAE J1978/J1939 scan tool: 

(A) The current readiness status from all on-board computers required to 

support readiness status in accordance with SAE J1979/J1939-73 and 

section (h)(4.1) in the key on, engine off position and while the engine is 

running; 

(B) The MIL command status while the MIL is commanded off and while the 

MIL is commanded on in accordance with SAE J1979/J1939 and section 

(h)(4.2) in the key on, engine off position and while the engine is running, 

and in accordance with SAE J1979/J1939 and sections (d)(2.1.2) during 

the MIL functional check and, if applicable, (h)(4.1.3) during the MIL 

readiness status check while the engine is off; 

(C) All data stream parameters required in section (h)(4.2) in accordance with 

SAE J1979/J1939 including, if applicable, the proper identification of each 

data stream parameter as supported in SAE J1979 (e.g., Mode/Service 

$01, PID $00); 

(D) The CAL ID, CVN, ESN, and VIN in accordance with SAE J1979/J1939 

and sections (h)(4.6) through (4.8); 

(E) An emission-related fault code (permanent, confirmed, pending, MIL-on, 

and previously MIL-on) in accordance with SAE J1979/J1939-73 

(including correctly indicating the number of stored fault codes (e.g., 

Mode/Service $01, PID $01, Data A for SAE J1979)) and section (h)(4.4); 

(1.4.4) The testing shall also verify that the on-board computer(s) can properly 

respond to any SAE J1978/J1939 scan tool request to clear emissionrelated fault codes and reset readiness status in accordance with section 

(h)(4.910). 

(1.5) Reporting of Results: 
125

(1.5.1) The manufacturer shall submit to the Executive Officer the following, 

based on the results of testing: 

(A) If a variant meets all the requirements of section (l)(1.4), a statement 

specifying that the variant passed all the tests, or 

(B) If any variant does not meet the requirements of section (l)(1.4), a written 

report to the Executive Officer for approval within one month of testing the 

specific variant. The written report shall include the problem(s) identified 

and the manufacturer’s proposed corrective action (if any) to remedy the 

problem(s). Factors to be considered by the Executive Officer in 

approving the proposed corrective action shall include the severity of the 

problem(s), the ability of the vehicle to be tested in a California inspection 

program (e.g., roadside inspection, fleet self-inspection program), the 

ability of service technicians to access the required diagnostic information, 

the impact on equipment and tool manufacturers, and the amount of time 

prior to implementation of the proposed corrective action. 

(1.5.2) Upon request of the Executive Officer, a manufacturer shall submit a 

report of the results of any testing conducted pursuant to section (l)(1) to 

the Executive Officer for review. 

(1.5.3) In accordance with section (k)(6), manufacturers may request Executive 

Officer approval for a retroactive deficiency to be granted for items 

identified during this testing. 

(1.6) Alternative Testing Protocols. Manufacturers may request Executive Officer 

approval to use other testing protocols. The Executive Officer shall approve 

the protocol if the manufacturer can demonstrate that the alternate testing 

methods and equipment provide an equivalent level of verification of 

compliance with the standardized requirements to the requirements of section 

(l)(1). 

(2) Verification of Monitoring Requirements. 

(2.1) Within either the first six months of the start of engine production or the first 

three months of the start of vehicle production, whichever is later, 

manufacturers shall conduct a complete evaluation of the OBD system of one 

or more production vehicles (test vehicles) and submit the results of the 

evaluation to the Executive Officer. 

(2.2) Selection of test vehicles: 

(2.2.1) For each engine selected for monitoring system demonstration in section 

(j), the manufacturer shall evaluate one production vehicle equipped with 

an engine from the same engine family and rating as the demonstration 

engine. The Executive Officer shall select the specific production 

vehicle(s) to be tested. 

(2.2.2) A manufacturer required to test more than one test vehicle may test an 

engine in lieu of a vehicle for all but one of the required test vehicles. 

(2.2.3) The Executive Officer may waive the requirements for submittal of 

evaluation results from one or more of the test vehicles if data have been 

previously submitted for all of the engine ratings and variants. 

(2.3) Evaluation requirements: 

(2.3.1) The evaluation shall demonstrate the ability of the OBD system on the 

selected production vehicle to detect a malfunction, illuminate the MIL, 
126

and, where applicable, store an appropriate fault code readable by a scan 

tool conforming to SAE J1978/J1939 when a malfunction is present and 

the monitoring conditions have been satisfied for each individual 

diagnostic required by title 13, CCR section 1971.1. 

(2.3.2) The evaluation shall verify that malfunctions detected by non-MIL 

illuminating diagnostics of components used to enable any other OBD 

system diagnostic (e.g., fuel level sensor) will not inhibit the ability of other 

OBD system diagnostics to properly detect malfunctions. 

(2.3.3) The evaluation shall verify that the software used to track the numerator 

and denominator for purposes of determining in-use monitoring frequency 

correctly increments as required in section (d)(4).

(2.3.4) Malfunctions may be mechanically implanted or electronically simulated 

but internal on-board computer hardware or software changes may not be 

used to simulate malfunctions. For monitors that are required to indicate 

a malfunction before emissions exceed an emission threshold based on 

any applicable standard (e.g., 2.0 times any of the applicable standards), 

manufacturers are not required to use malfunctioning 

components/systems set exactly at their malfunction criteria limits. 

Emission testing to confirm that the malfunction is detected before the 

appropriate emission standards are exceeded is not required. 

(2.3.5) Manufacturers shall submit a proposed test plan for Executive Officer 

approval prior to evaluation testing being performed. The test plan shall 

identify the method used to induce a malfunction for each diagnostic. If 

the Executive Officer determines that the requirements of section (l)(2) are 

satisfied, the proposed test plan shall be approved. 

(2.3.6) Subject to Executive Officer approval, manufacturers may omit 

demonstration of specific diagnostics. The Executive Officer shall 

approve a manufacturer's request if the demonstration cannot be 

reasonably performed without causing physical damage to the vehicle 

(e.g., on-board computer internal circuit faults). 

(2.3.7) For evaluation of test vehicles selected in accordance with section (l)(2.2), 

manufacturers are not required to demonstrate diagnostics that were 

previously demonstrated prior to certification as required in section (i). 

(2.4) Manufacturers shall submit a report of the results of all testing conducted 

pursuant to section (l)(2) to the Executive Officer for review. This report shall 

identify the method used to induce a malfunction in each diagnostic, the MIL 

illumination status, and the fault code(s) stored. 

(2.5) In accordance with section (k)(6), manufacturers may request Executive 

Officer approval for a retroactive deficiency to be granted for items identified 

during this testing. 

(3) Verification and Reporting of In-use Monitoring Performance. 

(3.1) Manufacturers are required to collect and report in-use monitoring 

performance data representative of production vehicles (i.e., engine rating 

and chassis application combination). Manufacturers shall collect and report 

the data to the ARB within twelve months after the production vehicles were 

first introduced into commerce. 
127

(3.2) Manufacturers shall separate production vehicles into monitoring 

performance groups, as defined by sections (l)(3.2.1) and (3.2.2) below, and 

submit data representative of each group: 

(3.2.1) Emission architecture. Engines shall be separated by emission 

architecture. All engines that use the same or similar emission control 

architecture and monitoring system shall be in the same emission 

architecture category. 

(3.2.2) Monitoring performance group. Within an emission architecture category, 

engines shall be separated by vehicle application. The separate 

monitoring performance groups shall be based on three classifications: 

engines intended primarily for line-haul chassis applications, engines 

intended primarily for urban delivery chassis applications, and all other 

engines. 

(3.3) Manufacturers may request Executive Officer approval to use an alternate 

grouping method to collect representative data. Executive Officer approval 

shall be granted upon determining that the proposed groupings include 

production vehicles using similar emission controls, OBD strategies, 

monitoring condition calibrations, and vehicle application driving/usage 

patterns such that they are expected to have similar in-use monitoring 

performance. If approved by the Executive Officer, the manufacturer may 

submit one set of data for each of the approved groupings. 

(3.4) For each group, the data must include all of the in-use performance tracking 

data reported through SAE J1979/J1939 (i.e., all numerators, denominators, 

the general denominator, and the ignition cycle counter), the date the data 

were collected, the odometer reading, the VIN, and the ECM software 

calibration identification number. 

(3.5) Manufacturers shall submit a plan to the Executive Officer for review and 

approval that details the types of production vehicles in each group, the 

number of vehicles per group to be sampled, the sampling method, the time 

line to collect the data, and the reporting format. The Executive Officer shall 

approve the plan upon determining that it provides for effective collection of 

data from a sample of vehicles that, at a minimum, is fifteen vehicles per 

group, will likely result in the collection and submittal of data within the 

required time frame, will generate data that are representative of California 

drivers and temperatures, and does not, by design, exclude or include 

specific vehicles in an attempt to collect data only from vehicles with the 

highest in-use performance ratios. 

(3.6) Upon request of the manufacturer, the Executive Officer may for good cause 

extend the twelve month time requirement set forth in section (l)(3.1) up to a 

maximum of eighteen months. In granting additional time, the Executive 

Officer shall consider, among other things, information submitted by the 

manufacturer to justify the delay, sales volume of the group(s), and the 

sampling mechanism utilized by the manufacturer to procure vehicles for data 

collection. If an extension beyond twelve months is granted, the 

manufacturer shall additionally be required to submit an interim report within 

twelve months for data collected up to the time of the interim report. 

(4) Verification of In-Use Compliance
128

(4.1) As a condition for certification, manufacturers are required to perform 

compliance testing on in-use engines as specified in California Code of 

Regulations, title 13, section 1971.5(c).

(m)INTERMEDIATE IN-USE COMPLIANCE STANDARDS

(1)For 2010 through 2012 model year engines:

(1.1)For monitors that are required to indicate a malfunction before emissions 

exceed a certain emission threshold (e.g., 2.5 times any of the applicable 

standards):

(1.1.1)On the OBD parent rating (i.e., the engine rating subject to the “full OBD” 

requirement under section (d)(7.1.1)), the Executive Officer may not 

consider an OBD system noncompliant unless a representative sample 

indicates emissions exceed 2.0 times the malfunction criteria (e.g., 5.0 

times the standard if the malfunction criterion is 2.5 times the standard) 

without MIL illumination on either of the applicable standards (i.e., FTP or 

SET).

(1.1.2)On the OBD child ratings (i.e., the engine ratings subject to the 

“extrapolated OBD” requirement under section (d)(7.1.2)), the Executive 

Officer may not consider an OBD system noncompliant based on 

emission levels.

(1.2)The Executive Officer shall use only the test cycle and standard determined and 

identified by the manufacturer at the time of certification in accordance with 

section (d)(6.1) as the most stringent for purposes of determining OBD 

system noncompliance in section (m)(1.1.1).

The Executive Officer shall use the adjustment factors determined by the 

manufacturer at the time of certification in accordance with section (d)(6.2) for 

purposes of determining OBD system noncompliance in section (m)(1.1.1).

(2)For 2013 through 2015 model year engines:

(2.1)For monitors that are required to indicate a malfunction before emissions 

exceed a certain emission threshold (e.g., 2.0 times any of the applicable 

standards):

(2.1.1)On all OBD parent ratings and OBD child ratings subject to section 

(d)(7.2.2), the Executive Officer may not consider an OBD system 

noncompliant unless a representative sample indicates emissions exceed 

2.0 times the malfunction criteria (e.g., 4.0 times the standard if the 

malfunction criterion is 2.0 times the standard) without MIL illumination on 

either of the applicable standards (i.e., FTP or SET).

(2.1.2)On all other engine ratings, the Executive Officer may not consider an 

OBD system noncompliant based on emission levels.

(2.2)The Executive Officer shall use only the test cycle and standard determined and 

identified by the manufacturer at the time of certification in accordance with 

section (d)(6.1) as the most stringent for purposes of determining OBD 

system noncompliance in section (m)(2.1.1).

(2.3)For monitors subject to meeting the minimum in-use monitor performance ratio 

of 0.100 in section (d)(3.2.2), the Executive Officer may not consider an OBD 

system noncompliant unless a representative sample indicates the in-use 

ratio is below 0.050.

(3)For 2016 through 2019 model year engines:
129

(3.1)For monitors of the PM filter subject to the malfunction criteria of section

(e)(8.2.1)(B), the Executive Officer may not consider the PM filter monitor 

noncompliant with the malfunction threshold of section (e)(8.2.1)(B) unless a 

representative sample indicates emissions exceed 2.0 times the malfunction 

criteria (e.g., PM emission level of 0.06 g/bhp-hr if the malfunction criterion is 

0.03 g/bhp-hr) without MIL illumination on either of the applicable standards 

(i.e., FTP or SET).

(3.2)For all engine ratings subject to section (d)(7.2.3) for extrapolated OBD in 2013 

through 2015, the Executive Officer may not consider an OBD system 

noncompliant unless a representative sample indicates emissions exceed 2.0 

times the malfunction criteria (e.g., 4.0 times the standard if the malfunction 

criterion is 2.0 times the standard) without MIL illumination on either of the 

applicable standards (i.e., FTP or SET), 

(4)For 2010 and subsequent model year engines, the Executive Officer may not 

consider an OBD system noncompliant solely due to a failure or deterioration 

mode of a monitored component or system that could not have been reasonably 

foreseen to occur by the manufacturer. 

NOTE: Authority cited: Sections 39600, 39601, 43000.5, 43013, 43018, 43100, 43101, 

43104, 43105, 43105.5, and 43106, Health and Safety Code. Reference: Sections 

39002, 39003, 39010-39060, 39515, 39600-39601, 43000, 43000.5, 43004, 43006, 

43013, 43016, 43018, 43100, 43101, 43102, 43104, 43105,43105.5, 43106, 43150-

43156, 43204, 43211, and 43212, Health and Safety Code. 
i

ATTACHMENT B 

California Code of Regulations, Title 13, section 1968.2, Malfunction and 

Diagnostic System Requirements for 2004 and Subsequent Model-Year 

Passenger Cars, Light-Duty Trucks, and Medium-Duty Vehicles and Engines 

(OBD II) 

Set forth below are proposed amendments to California Code of Regulations, 

Title 13, §1968.2. The proposed amendments are shown in single underline to 

indicate additions and single strikeout to indicate deletions. 
ii

Table of Contents 

(a) PURPOSE................................................................................................................. 1 

(b) APPLICABILITY. ...................................................................................................... 1 

(c) DEFINITIONS........................................................................................................... 1 

(d) GENERAL REQUIREMENTS................................................................................ 8 

(1) The OBD II System.......................................................................................... 8 

(2) MIL and Fault Code Requirements. .............................................................. 8 

(3) Monitoring Conditions.................................................................................... 12 

(4) In-Use Monitor Performance Ratio Definition............................................ 14 

(5) Standardized tracking and reporting of monitor performance. ............... 19 

(6) Malfunction Criteria Determination for Diesel Vehicles............................ 21 

(7) Enforcement Testing. .................................................................................... 24 

(e) MONITORING REQUIREMENTS FOR GASOLINE/SPARK-IGNITED 

ENGINES. ....................................................................................................................... 24 

(1) CATALYST MONITORING........................................................................... 24 

(2) HEATED CATALYST MONITORING ......................................................... 27 

(3) MISFIRE MONITORING ............................................................................... 27 

(4) EVAPORATIVE SYSTEM MONITORING ................................................. 34

(5) SECONDARY AIR SYSTEM MONITORING............................................. 37 

(6) FUEL SYSTEM MONITORING.................................................................... 38 

(7) EXHAUST GAS SENSOR MONITORING................................................. 41

(8) EXHAUST GAS RECIRCULATION (EGR) SYSTEM MONITORING... 44 

(9) POSITIVE CRANKCASE VENTILATION (PCV) SYSTEM 

MONITORING............................................................................................................. 45 

(10) ENGINE COOLING SYSTEM MONITORING........................................... 46 

(11) COLD START EMISSION REDUCTION STRATEGY MONITORING.. 50 

(12) AIR CONDITIONING (A/C) SYSTEM COMPONENT MONITORING... 51 

(13) VARIABLE VALVE TIMING AND/OR CONTROL (VVT) SYSTEM 

MONITORING............................................................................................................. 52 

(14) DIRECT OZONE REDUCTION (DOR) SYSTEM MONITORING.......... 53 

(15) COMPREHENSIVE COMPONENT MONITORING................................. 54 

(16) OTHER EMISSION CONTROL OR SOURCE SYSTEM MONITORING

 58 

(17) EXCEPTIONS TO MONITORING REQUIREMENTS.............................. 59 

(f) MONITORING REQUIREMENTS FOR DIESEL/COMPRESSION-IGNITION 

ENGINES. ....................................................................................................................... 62 

(1) NON-METHANE HYDROCARBON (NMHC) CONVERTING CATALYST 

MONITORING............................................................................................................. 62 

(2) OXIDES OF NITROGREN (NOx) CONVERTING CATALYST 

MONITORING............................................................................................................. 65 

(3) MISFIRE MONITORING ............................................................................... 69 

(4) FUEL SYSTEM MONITORING.................................................................... 71 

(5) EXHAUST GAS SENSOR MONITORING................................................. 76

(6) EXHAUST GAS RECIRCULATION (EGR) SYSTEM MONITORING... 81 
iii

(7) BOOST PRESSURE CONTROL SYSTEM MONITORING.................... 85 

(8) NOx ADSORBER MONITORING................................................................ 89 

(9) PARTICULATE MATTER (PM) FILTER MONITORING.......................... 91 

(10) CRANKCASE VENTILATION (CV) SYSTEM MONITORING ................ 94 

(11) ENGINE COOLING SYSTEM MONITORING........................................... 96 

(12) COLD START EMISSION REDUCTION STRATEGY MONITORING.. 99 

(13) VARIABLE VALVE TIMING AND/OR CONTROL (VVT) SYSTEM 

MONITORING........................................................................................................... 101 

(14) [RESERVED] ................................................................................................ 102 

(15) COMPREHENSIVE COMPONENT MONITORING............................... 102 

(16) OTHER EMISSION CONTROL OR SOURCE SYSTEM MONITORING

 107 

(17) EXCEPTIONS TO MONITORING REQUIREMENTS............................ 109 

(g) STANDARDIZATION REQUIREMENTS. ........................................................ 112 

(1) Reference Documents:................................................................................ 112 

(2) Diagnostic Connector:................................................................................. 113 

(3) Communications to a Scan Tool:............................................................... 113 

(4) Required Emission Related Functions: .................................................... 114 

(5) In-use Performance Ratio Tracking Requirements: ............................... 122 

(6) Engine Run Time Tracking Requirements:.............................................. 123 

(7) Exceptions to Standardization Requirements. ........................................ 126 

(h) MONITORING SYSTEM DEMONSTRATION REQUIREMENTS FOR 

CERTIFICATION.......................................................................................................... 126 

(1) General. ......................................................................................................... 126 

(2) Selection of Test Vehicles: ......................................................................... 127 

(3) Required Testing for Gasoline/Spark-ignited vehicles:.......................... 127 

(4) Required Testing for Diesel/Compression-ignition vehicles: ................ 129 

(5) Testing Protocol: .......................................................................................... 131 

(6) Evaluation Protocol:..................................................................................... 132 

(7) Confirmatory Testing: .................................................................................. 134 

(i) CERTIFICATION DOCUMENTATION. ............................................................ 134 

(j) PRODUCTION VEHICLE EVALUATION. TESTING. .................................... 138 

(1) Verification of Standardized Requirements. ............................................ 138 

(2) Verification of Monitoring Requirements. ................................................. 139 

(3) Verification and Reporting of In-use Monitoring Performance.............. 141 

(k) DEFICIENCIES. ................................................................................................... 142
§1968.2. Malfunction and Diagnostic System Requirements--2004 and 

Subsequent Model-Year Passenger Cars, Light-Duty Trucks, and Medium-Duty 

Vehicles and Engines 

(a) PURPOSE.

The purpose of this regulation is to establish emission standards and other 

requirements for onboard diagnostic systems (OBD II systems) that are installed on 

2004 and subsequent model-year passenger cars, light-duty trucks, and 

medium-duty vehicles and engines certified for sale in California. The OBD II 

systems, through the use of an onboard computer(s), shall monitor emission 

systems in-use for the actual life of the vehicle and shall be capable of detecting 

malfunctions of the monitored emission systems, illuminating a malfunction indicator 

light (MIL) to notify the vehicle operator of detected malfunctions, and storing fault 

codes identifying the detected malfunctions. 

(b) APPLICABILITY.

Except as specified elsewhere in this regulation (title 13, CCR section 1968.2), all 

2004 and subsequent model-year vehicles, defined as passenger cars, light-duty 

trucks, and medium-duty vehicles, including medium-duty vehicles with engines 

certified on an engine dynamometer and medium-duty passenger vehicles, shall be 

equipped with an OBD II system and shall meet all applicable requirements of this 

regulation (title 13, CCR section 1968.2). Except as specified in section (d)(2.2.5), 

medium-duty vehicles with engines certified on an engine dynamometer may comply 

with these requirements on an engine model year certification basis rather than a 

vehicle model year basis. 

(c) DEFINITIONS.

 “Actual life” refers to the entire period that a vehicle is operated on public roads 

in California up to the time a vehicle is retired from use. 

“Alternate phase-in” is a phase-in schedule that achieves equivalent compliance 

volume by the end of the last year of a scheduled phase-in provided in this 

regulation. The compliance volume is the number calculated by multiplying the 

percent of vehicles (based on the manufacturer’s projected sales volume of all 

vehicles) meeting the new requirements per year by the number of years 

implemented prior to and including the last year of the scheduled phase-in and then 

summing these yearly results to determine a cumulative total (e.g., a three year, 

30/60/100 percent scheduled phase-in would be calculated as (30*3 years) + (60*2 

years) + (100*1 year) = 310). On phase-ins scheduled to begin prior to the 2004 

model year, manufacturers are allowed to include vehicles introduced before the 

first year of the scheduled phase-in (e.g., in the previous example, 10 percent 

introduced one year before the scheduled phase-in begins would be calculated as 

(10*4 years) and added to the cumulative total). However, on phase-ins scheduled 

to begin in 2004 or subsequent model years, manufacturers are only allowed to 

include vehicles introduced up to one model year before the first year of the 

scheduled phase-in. The Executive Officer shall consider acceptable any alternate 

phase-in that results in an equal or larger cumulative total by the end of the last year 

of the scheduled phase-in and ensures that all vehicles subject to the phase-in will 
2

comply with the respective requirements no later than two model years following the 

last year of the scheduled phase-in. 

For alternate phase-in schedules resulting in all vehicles complying one 

model year following the last year of the scheduled phase-in, the compliance 

volume shall be calculated as described directly above. For example, a 

30/60/100 percent scheduled phase-in during the 2010-2012 model years would 

have a cumulative total of 310. If the manufacturer’s planned alternate phase-in 

schedule is 40/50/80/100 percent during the 2010-2013 model years, the final 

compliance volume calculation would be (40*3 years) + (50*2 years) + (80*1 

year) = 300, which is less than 310 and therefore would not be acceptable as an 

alternate phase-in schedule. 

For alternate phase-in schedules resulting in all vehicles complying two 

model years following the last year of the scheduled phase-in, the compliance 

volume calculation shall be calculated as described directly above and shall also 

include a negative calculation for vehicles not complying until one or two model 

years following the last year of the scheduled phase-in. The negative calculation 

shall be calculated by multiplying the percent of vehicles not meeting the new 

requirements in the final year of the phase-in by negative one and the percent of 

vehicles not meeting the new requirements in the one year after the final year of 

the phase-in by negative two. For example, if 10 percent of a manufacturer’s 

vehicles did not comply by the final year of the scheduled phase-in and 5 percent 

did not comply by the end of the first year after the final year of the scheduled 

phase-in, the negative calculation result would be (10*(-1 years)) + (5*(-2 years)) 

= -20. The final compliance volume calculation is the sum of the original 

compliance volume calculation and the negative calculation. For example, a 

30/60/100 percent scheduled phase-in during the 2010-2012 model years would 

have a cumulative total of 310. If a manufacturer’s planned alternate phase-in 

schedule is 40/70/80/90/100 percent during the 2010-2014 model years, the final 

compliance volume calculation would be (40*3 years) + (70*2 years) + (80*1 

year) + (20*(-1 year)) + (10*(-2 years)) = 300, which is less than 310 and 

therefore would not be acceptable as an alternate phase-in schedule. 

“Applicable standards” refers to the specific exhaust emission standards or 

family emission limits (FEL) of the Federal Test Procedure (FTP) to which the 

vehicle or engine is certified. For 2010 and subsequent model year diesel engines, 

“applicable standards” shall also refer to the specific exhaust emission standards or 

family emission limits (FEL) of either the FTP or the Supplemental Emission Test 

(SET) to which the engine is certified, as determined according to section (d)(6). 

“Auxiliary Emission Control Device (AECD)” refers to any approved AECD (as 

defined by 40 Code of Federal Regulations (CFR) 86.082-2 and 86.094-2). 

“Emission Increasing Auxiliary Emission Control Device (EI-AECD)” refers to 

any approved AECD that: reduces the effectiveness of the emission control 

system under conditions which may reasonably be expected to be encountered 

in normal vehicle operation and use; and the need for the AECD is justified in 

terms of protecting the vehicle against damage or accident. For medium-duty 

vehicles certified to an engine dynamometer tailpipe emission standard, an 

AECD that is certified as an NTE deficiency shall not be considered an EI-AECD. 

An AECD that does not sense, measure, or calculate any parameter or 

command or trigger any action, algorithm, or alternate strategy shall not be 
3

considered an EI-AECD. An AECD that is activated solely due to any of the 

following conditions operation of the vehicle above 8000 feet in elevation shall 

not be considered an EI-AECD: (1) operation of the vehicle above 8000 feet in 

elevation; (2) ambient temperature; (3) when the engine is warming up and is not 

reactivated once the engine has warmed up in the same driving cycle; (4) failure 

detection (storage of a fault code) by the OBD system; (5) execution of an OBD 

monitor; or (6) execution of an infrequent regeneration event. 

“Base fuel schedule” refers to the fuel calibration schedule programmed into the 

Powertrain Control Module or PROM when manufactured or when updated by some 

off-board source, prior to any learned on-board correction. 

“Calculated load value” refers to an indication of the percent engine capacity that 

is being used and is defined in Society of Automotive Engineers (SAE) J1979 "E/E 

Diagnostic Test Modes – Equivalent to ISO/DIS 15031-5:April 30, 2002", April 2002 

(SAE J1979), incorporated by reference (section (g)(1.4)1). For diesel applications, 

the calculated load value is determined by the ratio of current output torque to 

maximum output torque at current engine speed as defined by suspect parameter 

number (SPN) 92 of SAE J1939 “Recommended Practice for a Serial Control and 

Communications Vehicle Network” (SAE J1939), incorporated by reference. 

“Confirmed fault code” is defined as the diagnostic trouble code stored when an 

OBD II system has confirmed that a malfunction exists (e.g., typically on the second 

driving cycle that the malfunction is detected) in accordance with the requirements 

of sections (e), (f), and (g)(4.4). 

“Continuously,” if used in the context of monitoring conditions for circuit 

continuity, lack of circuit continuity, circuit faults, and out-of-range values, means 

monitoring is always enabled, unless alternate enable conditions have been 

approved by the Executive Officer in accordance with section (d)(3.1.1), and 

sampling of the signal used for monitoring occurs at a rate no less than two samples 

per second. If for control purposes, a computer input component is sampled less 

frequently, the signal of the component may instead be evaluated each time 

sampling occurs. 

“Deactivate” means to turn-off, shutdown, desensitize, or otherwise make 

inoperable through software programming or other means during the actual life of 

the vehicle. 

“Diagnostic or emission critical” electronic powertrain control unit refers to the 

engine and transmission control unit(s). For the 2005 and subsequent model years, 

it also includes any other on-board electronic powertrain control unit containing 

software that: (1) has primary control over any of the monitors required by sections 

(e)(1.0) through (e)(14.0), (e)(16.0), (f)(1) through (f)(14), and (f)(16) or, (2) 

excluding anti-lock brake system (ABS) control units or stability/traction control units, 

has primary control over the diagnostics for more than two of the components 

required to be monitored by sections (e)(15.0) and (f)(15). For purposes of criterion

(2) above, all glow plugs in an engine shall be considered “one” component in lieu of 

each glow plug being considered a separate component.

“Diesel engines” refers to engines using a compression ignition thermodynamic 

cycle. 

 

1

 Unless otherwise noted, all section references refer to section 1968.2 of title 13, CCR. 
4

“Driving cycle” consists of engine startup and engine shutoff and includes the 

period of engine off time up to the next engine startup. For vehicles that employ 

engine shutoff strategies (e.g., engine shutoff at idle), the manufacturer may request 

Executive Officer approval to use an alternate definition for driving cycle (e.g., key 

on and key off). Executive Officer approval of the alternate definition shall be based 

on equivalence to engine startup and engine shutoff signaling the beginning and 

ending of a single driving event for a conventional vehicle. For applications that are 

used in both medium-duty and heavy-duty classes, the manufacturer may use the 

driving cycle definition of title 13, CCR, section 1971.1 in lieu of this definition. 

Engine restarts following an engine shut-off that has been neither commanded by 

the vehicle operator nor by the engine control strategy but caused by an event such 

as an engine stall may be considered a new driving cycle or a continuation of the 

existing driving cycle. 

“Engine misfire” means lack of combustion in the cylinder due to absence of 

spark, poor fuel metering, poor compression, or any other cause. This does not 

include lack of combustion events in non-active cylinders due to default fuel shut-off 

or cylinder deactivation strategies. 

“Engine start” is defined as the point when the engine reaches a speed 150 rpm 

below the normal, warmed-up idle speed (as determined in the drive position for 

vehicles equipped with an automatic transmission). For hybrid vehicles or for 

engines employing alternate engine start hardware or strategies (e.g., integrated 

starter and generators, etc.), the manufacturer may request Executive Officer 

approval to use an alternate definition for engine start (e.g., ignition key “on”). 

Executive Officer approval of the alternate definition shall be based on equivalence 

to an engine start for a conventional vehicle. 

“Family Emission Limit (FEL)” refers to the exhaust emission levels to which an

engine family is certified under the averaging, banking, and trading program 

incorporated by reference in title 13, CCR section 1956.8. 

“Fault memory” means information pertaining to malfunctions stored in the 

onboard computer, including fault codes, stored engine conditions, and MIL status. 

“Federal Test Procedure (FTP) test” refers to an exhaust emission test 

conducted according to the test procedures incorporated by reference in title 13, 

CCR section 1961(d) that is used to determine compliance with the FTP standard to 

which a vehicle is certified. 

“FTP cycle”. For passenger vehicles, light-duty trucks, and medium-duty 

vehicles certified on a chassis dynamometer, FTP cycle refers to the driving 

schedule in Code of Federal Regulations (CFR) 40, Appendix 1, Part 86, section 

(a) entitled, “EPA Urban Dynamometer Driving Schedule for Light-Duty Vehicles 

and Light-Duty Trucks.” For medium-duty engines certified on an engine 

dynamometer, FTP cycle refers to the engine dynamometer schedule in CFR 40, 

Appendix 1, Part 86, section (f)(1), entitled, “EPA Engine Dynamometer 

Schedule for Heavy-Duty Otto-Cycle Engines,” or section (f)(2), entitled, “EPA 

Engine Dynamometer Schedule for Heavy-Duty Diesel Engines.” 

“FTP standard” refers to the certification tailpipe exhaust emission full useful 

life standards and test procedures applicable to the FTP cycle and to the class to 

which the vehicle is certified. 

“FTP full useful life standard” refers to the FTP standard applicable when the 

vehicle reaches the end of its full useful life as defined in the certification 
5

requirements and test procedures incorporated by reference in title 13, CCR 

section 1961(d). 

“Fuel trim” refers to feedback adjustments to the base fuel schedule. Short-term 

fuel trim refers to dynamic or instantaneous adjustments. Long-term fuel trim refers 

to much more gradual adjustments to the fuel calibration schedule than short-term 

trim adjustments. 

“Functional check” for an output component or system means verification of 

proper response of the component and system to a computer command. 

“Gasoline engine” refers to an Otto-cycle engine or an alternate-fueled engine. 

“Keep-alive memory (KAM),” for the purposes of this regulation, is defined as a 

type of memory that retains its contents as long as power is provided to the onboard control unit. KAM is not erased upon shutting off the engine but may be 

erased if power to the on-board control unit is interrupted (e.g., vehicle battery 

disconnected, fuse to control unit removed). In some cases, portions of KAM may 

be erased with a scan tool command to reset KAM. 

“Key on, engine off position” refers to a vehicle with the ignition key in the engine 

run position (not engine crank or accessory position) but with the engine not 

running. 

“Light-duty truck” is defined in title 13, CCR section 1900 (b). 

“Low Emission Vehicle I application” refers to a vehicle or engine certified in 

California to the exhaust emission standards defined in title 13, CCR sections 

1956.8(g), 1960.1(g)(1), and 1960.1(h)(1) for any of the following vehicle emission 

categories: Transitional Low Emission Vehicle (TLEV), Low Emission Vehicle (LEV), 

Ultra Low Emission Vehicle (ULEV), or Super Ultra Low Emission Vehicle (SULEV). 

 Additionally, vehicles certified to Federal emission standards (bins) in California but 

categorized in a Low Emission Vehicle I vehicle emission category for purposes of 

calculating NMOG fleet average in accordance with the certification requirements 

and test procedures incorporated by reference in title 13, CCR section 1961 (d) are 

subject to all monitoring requirements applicable to Low Emission Vehicle I 

applications but shall use the Federal tailpipe emission standard (i.e., the Federal 

bin) for purposes of determining the malfunction thresholds in sections (e) and (f).

“MDV SULEV vehicles” refer only to medium-duty Low Emission Vehicle I 

applications certified to the SULEV vehicle emission category. 

“TLEV vehicles” refer only to Low Emission Vehicle I applications certified to 

the TLEV vehicle emission category. 

“LEV vehicles” refer only to Low Emission Vehicle I applications certified to 

the LEV vehicle emission category. 

“ULEV vehicles” refer only to Low Emission Vehicle I applications certified to 

the ULEV vehicle emission category. 

“Low Emission Vehicle II application” refers to a vehicle or engine certified in 

California to the exhaust emission standards defined in title 13, CCR section 1961, 

or optionally certified to the exhaust emission standards defined in title 13, CCR 

section 1956.8, for any of the following emission categories: LEV, ULEV, or SULEV. 

 Additionally, except as provided for in sections (e)(17.1.3) and (f)(17.1.2), vehicles 

certified to Federal emission standards (bins) in California but categorized in a Low 

Emission Vehicle II vehicle emission category for purposes of calculating NMOG 

fleet average in accordance with the certification requirements and test procedures 
6

incorporated by reference in title 13, CCR section 1961 (d) are subject to all 

monitoring requirements applicable to Low Emission Vehicle II applications but shall 

use the Federal tailpipe emission standard (i.e., the Federal bin) for purposes of 

determining the malfunction thresholds in sections (e) and (f). 

“PC/LDT SULEV II vehicles” refer only to passenger car and light-duty truck 

Low Emission Vehicle II applications certified to the SULEV vehicle emission 

category. 

“MDV SULEV II vehicles” refer only to medium-duty Low Emission Vehicle II 

applications certified to the SULEV vehicle emission category. 

“LEV II vehicles” refer only to Low Emission Vehicle II applications certified to 

the LEV vehicle emission category. 

“ULEV II vehicles” refer only to Low Emission Vehicle II applications certified 

to the ULEV vehicle emission category. 

“Malfunction” means any deterioration or failure of a component that causes the 

performance to be outside of the applicable limits in sections (e) and (f).

“Medium-duty vehicle” is defined in title 13, CCR section 1900 (b). 

“Medium-duty passenger vehicle” or “MDPV” is defined in Title 40, Section 

86.1803-01, Code of Federal Regulations. 

“Non-volatile random access memory (NVRAM),” for the purposes of this 

regulation, is defined as a type of memory that retains its contents even when power 

to the on-board control unit is interrupted (e.g., vehicle battery disconnected, fuse to 

control unit removed). NVRAM is typically made non-volatile either by use of a 

back-up battery within the control unit or through the use of an electrically erasable 

and programmable read-only memory (EEPROM) chip. 

“Not-To-Exceed (NTE) control area” refers to the bounded region of the engine’s 

torque and speed map, as defined in 40 CFR 86.1370-2007, where emissions must 

not exceed a specific emission cap for a given pollutant under the NTE requirement. 

“Manufacturer-specific NOx NTE carve-out area” refers to regions within the 

NTE control area for NOx where the manufacturer has limited NTE testing as 

allowed by 40 CFR 86.1370-2007(b)(7). 

“Manufacturer-specific PM NTE carve-out area” refers to regions within the 

NTE control area for PM where the manufacturer has limited NTE testing as 

allowed by 40 CFR 86.1370-2007(b)(7). 

“NTE deficiency” refers to regions or conditions within the NTE control area 

for NOx or PM where the manufacturer has received a deficiency as allowed by 

40 CFR 86.007-11(a)(4)(iv). 

“Normal production” is the time after the start of production when the

manufacturer has produced two percent of the projected volume for the test group 

or calibration, whichever is being evaluated in accordance with section (j). 

“Passenger car” is defined in title 13, CCR section 1900 (b). 

“Pending fault code” is defined as the diagnostic trouble code stored upon the 

initial detection of a malfunction (e.g., typically on a single driving cycle) prior to 

illumination of the MIL in accordance with the requirements of sections (e), (f), and 

(g)(4.4). 

“Percentage of misfire” as used in (e)(3.2) and (f)(3.2) means the percentage of 

misfires out of the total number of firing events for the specified interval. 
7

“Permanent fault code” is defined as a confirmed fault code that is currently 

commanding the MIL on and is stored in NVRAM as specified in sections (d)(2) and 

(g)(4.4). 

“Power Take-Off (PTO) unit” refers to an engine driven output provision for the 

purposes of powering auxiliary equipment (e.g., a dump-truck bed, aerial bucket, or 

tow-truck winch). 

“Rationality fault diagnostic” for an input component means verification of the 

accuracy of the input signal while in the range of normal operation and when 

compared to all other available information. 

“Redline engine speed” shall be defined by the manufacturer as either the

recommended maximum engine speed as normally displayed on instrument panel 

tachometers or the engine speed at which fuel shutoff occurs. 

“Response rate” for exhaust gas sensors refers to the delay from when the 

sensor is exposed to a different make-up of exhaust gas constituents until it outputs 

a signal reflecting the different make-up of exhaust gas constituents. For example, 

for oxygen sensors, response rate is the delay from when the oxygen sensor is 

exposed to a change in exhaust gas from richer/leaner than stoichiometric to 

leaner/richer than stoichiometric to the time when the oxygen sensor indicates the 

lean/rich condition. Similarly, for wide-range air-fuel (A/F) sensors, response rate is 

the delay from when the sensor is exposed to a different A/F ratio to the time it 

indicates the different A/F ratio. For NOx and PM sensors, response rate is the 

delay from when the sensor is exposed to a different NOx or PM exhaust gas level 

until it indicates the different NOx or PM exhaust gas level. 

“SC03 emission standards” refers to the certification tailpipe exhaust emission 

standards for the air conditioning (A/C) test of the Supplemental Federal Test 

Procedure Off-Cycle Emission Standards specified in title 13, CCR section 1961(a) 

applicable to the class to which the vehicle is certified. 

“Secondary air” refers to air introduced into the exhaust system by means of a 

pump or aspirator valve or other means that is intended to aid in the oxidation of HC 

and CO contained in the exhaust gas stream. 

“Similar conditions” as used in sections (e)(3), (e)(6), (f)(3), and (f)(4) means 

engine conditions having an engine speed within 375 rpm, load conditions within 20 

percent, and the same warm-up status (i.e., cold or hot) as the engine conditions 

stored pursuant to (e)(3.4.4), (e)(6.4.5), (f)(3.4.2)(C), and (f)(4.4.2)(E). The 

Executive Officer may approve other definitions of similar conditions based on 

comparable timeliness and reliability in detecting similar engine operation. 

“Small volume manufacturer” is defined in title 13, CCR section 1900(b). 

However, for a manufacturer that transitions from a small volume manufacturer to a 

non-small volume manufacturer, the manufacturer is still considered a small volume 

manufacturer for the first three model years that it no longer meets the definition in 

title 13, CCR section 1900(b). 

“Supplemental Emission Test (SET) cycle” refers to the driving schedule defined 

as the “supplemental steady state emission test” in 40 CFR 86.1360-2007, as 

amended July 13, 2005.

“SET standard” refers to the certification exhaust emission standards and test 

procedures applicable to the SET cycle incorporated by reference in title 13, CCR 

sections 1956.8(b) and (d) to which the engine is certified. 
8

“Unified cycle” is defined in “Speed Versus Time Data for California’s Unified 

Driving Cycle”, dated December 12, 1996, incorporated by reference. 

“US06 cycle” refers to the driving schedule in 40 CFR 86, Appendix 1, section 

(g), as amended July 13, 2005, entitled, “EPA US06 Driving Schedule for Light-Duty 

Vehicles and Light-Duty Trucks.” 

“Warm-up cycle” means sufficient vehicle operation such that the coolant 

temperature has risen by at least 40 degrees Fahrenheit from engine starting and 

reaches a minimum temperature of at least 160 degrees Fahrenheit (140 degrees 

Fahrenheit for applications with diesel engines). 

(d) GENERAL REQUIREMENTS. 

Section (d) sets forth the general requirements of the OBD II system. Specific 

performance requirements for components and systems that shall be monitored are 

set forth in sections (e) and (f) below. 

(1) The OBD II System. 

(1.1) If a malfunction is present as specified in sections (e) and (f), the OBD II 

system shall detect the malfunction, store a pending or confirmed fault code 

in the onboard computer’s memory, and illuminate the MIL as required. 

(1.2) The OBD II system shall be equipped with a standardized data link connector 

to provide access to the stored fault codes as specified in section (g). 

(1.3) The OBD II system shall be designed to operate, without any required 

scheduled maintenance, for the actual life of the vehicle in which it is installed 

and may not be programmed or otherwise designed to deactivate based on 

age and/or mileage of the vehicle during the actual life of the vehicle. This 

section is not intended to alter existing law and enforcement practice 

regarding a manufacturer’s liability for a vehicle beyond its useful life, except 

where a vehicle has been programmed or otherwise designed so that an 

OBD II system deactivates based on age and/or mileage of the vehicle. 

(1.4) Computer-coded engine operating parameters may not be changeable 

without the use of specialized tools and procedures (e.g. soldered or potted 

computer components or sealed (or soldered) computer enclosures). Subject 

to Executive Officer approval, manufacturers may exempt from this 

requirement those product lines that are unlikely to require protection. 

Criteria to be evaluated in making an exemption include current availability of 

performance chips, high performance capability of the vehicle, and sales 

volume.

(2) MIL and Fault Code Requirements. 

(2.1) MIL Specifications. 

(2.1.1) The MIL shall be located on the driver's side instrument panel and be of 

sufficient illumination and location to be readily visible under all lighting 

conditions and shall be amber in color when illuminated. The MIL, when 

illuminated, shall display the phrase “Check Engine” or “Service Engine 

Soon”. The word “Powertrain” may be substituted for “Engine” in the 

previous phrases. Alternatively, the International Standards Organization 

(ISO) engine symbol may be substituted for the word “Engine” or for the 

entire phrase. 
9

(2.1.2) The MIL shall illuminate in the key on, engine off position before engine 

cranking to indicate that the MIL is functional. For all 2005 and 

subsequent model year vehicles, the MIL shall continuously illuminate 

during this functional check for a minimum of 15-20 seconds. During this 

functional check of the MIL, the data stream value for MIL status shall 

indicate commanded off (see section (g)(4.2)) unless the MIL has also 

been commanded on for a detected malfunction. This functional check of 

the MIL is not required during vehicle operation in the key on, engine off 

position subsequent to the initial engine cranking of each driving cycle 

(e.g., due to an engine stall or other non-commanded engine shutoff). 

(2.1.3) At the manufacturer's option, the MIL may be used to indicate readiness 

status in a standardized format (see section (g)(4.1.3)) in the key on, 

engine off position. 

(2.1.4) A manufacturer may request Executive Officer approval to also use the 

MIL to indicate which, if any, fault codes are currently stored (e.g., to 

“blink” the stored codes). The Executive Officer shall approve the request 

upon determining that the manufacturer has demonstrated that the 

method used to indicate the fault codes will not be activated during a 

California Inspection and Maintenance test or during routine driver 

operation. 

(2.1.5) The MIL may not be used for any purpose other than specified in this 

regulation. 

(2.2) MIL Illumination and Fault Code Storage Protocol. 

(2.2.1) Upon detection of a malfunction, the OBD system shall store a pending 

fault code within ten seconds indicating the likely area of the malfunction. 

(2.2.2) After storage of a pending fault code, if the identified malfunction is again 

detected before the end of the next driving cycle in which monitoring 

occurs, the MIL shall illuminate continuously and a confirmed fault code 

shall be stored within 10 seconds. If a malfunction is not detected before 

the end of the next driving cycle in which monitoring occurs (i.e., there is 

no indication of the malfunction at any time during the driving cycle), the 

corresponding pending fault code set according to section (d)(2.2.1) shall 

be erased at the end of the driving cycle. 

(2.2.3) The OBD system shall illuminate the MIL and store a fault code within 10 

seconds to inform the vehicle operator whenever the powertrain enters a 

default or “limp home” mode of operation that can affect emissions or the 

performance of the OBD II system or in the event of a malfunction of an 

on-board computer(s) itself that can affect the performance of the OBD II 

system. 

(A) If the default or “limp home” mode of operation is recoverable (i.e., the 

diagnostic or control strategy that caused the default or “limp home” mode 

of operation can run on the next driving cycle and confirm the presence of 

the condition that caused the default or “limp home” operation), the OBD II 

system may, in lieu of illuminating the MIL within 10 seconds on the first 

driving cycle where the default or “limp home” mode of operation is 

entered, delay illumination of the MIL until the condition causing the 

default or “limp home” mode of operation is again detected before the end 

of the next driving cycle. 
10

(B) MIL illumination and fault code storage is not required for engine 

overtemperature default strategies that are only initiated after the 

temperature gauge indicates a temperature in the red zone, or after an 

overtemperature “hot” light is illuminated, or due to the verified occurrence 

of severe operating conditions (e.g., extended trailer towing up a grade). 

(2.2.4) For all 2010 and subsequent model year vehicles, the OBD II system shall 

default to a MIL on state if the instrument panel receives and/or processes 

instructions or commands from other diagnostic or emission critical 

electronic powertrain control units to illuminate the MIL and a malfunction 

occurs (e.g., communication is lost) such that the instrument panel is no 

longer able to properly receive the MIL illumination requests. Storage of a 

fault code is not required for this malfunction. 

(2.2.5) For 50 percent of all 2010, 75 percent of all 2011, and 100 percent of all 

2012 and subsequent model year vehicles (including 2012 model year 

medium-duty vehicles with 2011 model year engines certified on an 

engine dynamometer), before the end of an ignition cycle, the OBD II 

system shall store confirmed fault codes that are currently causing the 

MIL to be illuminated in NVRAM as permanent fault codes (as defined in 

section (g)(4.4.6)). 

(2.2.6) A manufacturer may request Executive Officer approval to employ 

alternate statistical MIL illumination and fault code storage protocols to 

those specified in these requirements. The Executive Officer shall grant 

approval upon determining that the manufacturer has provided data 

and/or engineering evaluation that demonstrate that the alternative 

protocols can evaluate system performance and detect malfunctions in a 

manner that is equally effective and timely. Except as otherwise provided 

in section (e) for evaporative system malfunctions, strategies requiring on 

average more than six driving cycles for MIL illumination may not be 

accepted. 

(2.2.7) A manufacturer shall store and erase “freeze frame” conditions (as 

defined in section (g)(4.3)) present at the time a malfunction is detected. 

A manufacturer shall store and erase freeze frame conditions in 

conjunction with storage and erasure of either pending or confirmed fault 

codes as required elsewhere in section (d)(2.2). 

(2.3) Extinguishing the MIL. 

Except as otherwise provided in sections (e)(3.4.5), (e)(4.4.2), (e)(6.4.6), 

(f)(3.4.2)(D), and (f)(4.4.2)(F) for misfire, evaporative system, and fuel system 

malfunctions, once the MIL has been illuminated it may be extinguished after 

three subsequent sequential driving cycles during which the monitoring 

system responsible for illuminating the MIL functions and the previously 

detected malfunction is no longer present provided no other malfunction has 

been detected that would independently illuminate the MIL according to the 

requirements outlined above. 

(2.4) Erasing a confirmed fault code. 

The OBD II system may erase a confirmed fault code if the identified 

malfunction has not been again detected in at least 40 engine warm-up 

cycles, and the MIL is presently not illuminated for that malfunction. 

(2.5) Erasing a permanent fault code. 
11

(2.5.1) If the OBD II system is commanding the MIL on, the OBD II system shall 

erase a permanent fault code only if the OBD II system itself determines 

that the malfunction that caused the permanent fault code to be stored is 

no longer present and is not commanding the MIL on, pursuant to the 

requirements of section (d)(2.3) (which for purposes of this section shall 

apply to all monitors). 

(2.5.2) If all fault information in the on-board computer other than the permanent 

fault code has been cleared (i.e., through the use of a scan tool or battery 

disconnect) and the OBD II system is not commanding the MIL on: 

(A) Except as provided for in sections (d)(2.5.2)(C) through (E), if the monitor 

of the malfunction that caused the permanent fault code to be stored is 

subject to the minimum ratio requirements of section (d)(3.2) (e.g., 

catalyst monitor, comprehensive component input component rationality 

monitors), the OBD II system shall erase the permanent fault code at the 

end of a driving cycle if the monitor has run and made one or more 

determinations during a driving cycle that the malfunction of the 

component or the system is not present and has not made any 

determinations within the same driving cycle that the malfunction is 

present. 

(B) Except as provided for in sections (d)(2.5.2)(D) and (E), if the monitor of 

the malfunction that caused the permanent fault code to be stored is not 

subject to the minimum ratio requirements of section (d)(3.2) (e.g., 

gasoline misfire monitor, fuel system monitor, comprehensive component 

circuit continuity monitors), the OBD II system shall erase the permanent 

fault code at the end of a driving cycle if: 

(i) The monitor has run and made one or more determinations during a 

driving cycle that the malfunction of the component or the system is 

not present and has not made any determinations within the same 

driving cycle that the malfunction is present; 

(ii) The monitor has not made any determinations that the malfunction is 

present subsequent to the most recent driving cycle in which the 

criteria of section (d)(2.5.2)(B)(i) are met; and 

(iii) The following criteria are satisfied on any single driving cycle (which 

may be a different driving cycle than that in which the criteria of section 

(d)(2.5.2)(B)(i) are satisfied): 

a. Cumulative time since engine start is greater than or equal to 600 

seconds; 

b. Except as provided in section (d)(2.5.2)(B)(iii)e. below, Ccumulative 

vehicle operation at or above 25 miles per hour occurs for greater 

than or equal to 300 seconds (medium-duty vehicles with diesel 

engines certified on an engine dynamometer may use cumulative 

operation at or above 15% calculated load1150 rpm in lieu of at or 

above 25 miles per hour for purposes of this criteria); and

c. Continuous vehicle operation at idle (i.e., accelerator pedal released 

by driver and either vehicle speed less than or equal to one mile 

per hour or engine speed less than or equal to 200 rpm above 

normal warmed-up idle (as determined in the drive position for 
12

vehicles equipped with an automatic transmission)) for greater than 

or equal to 30 seconds; and

d. The monitor has not made any determination that the malfunction is 

present.

e. For 2004 through 2012 model year medium-duty vehicles with diesel 

engines certified on an engine dynamometer, manufacturers may 

use diesel engine operation at or above 15 percent calculated load 

in lieu of 1150 rpm for the criterion in section (d)(2.5.2)(B)(iii)b.

above.

(iv) Monitors required to use “similar conditions” as defined in section (c) 

to store and erase pending and confirmed fault codes may not require 

that the similar conditions be met prior to erasure of the permanent 

fault code. 

(C) For monitors subject to section (d)(2.5.2)(A), the manufacturer may 

choose to erase the permanent fault code using the criteria under section 

(d)(2.5.2)(B) in lieu of the criteria under section (d)(2.5.2)(A). 

(D) For 2009 and 2010 model year vehicles meeting the permanent fault 

code requirements of section (d)(2.2.5), manufacturers may request 

Executive Officer approval to use alternate criteria to erase the permanent 

fault code. The Executive Officer shall approve alternate criteria that: 

(i) Will not likely require driving conditions that are longer and more 

difficult to meet than those required under section (d)(2.5.2)(B), and 

(ii) Do not require access to enhanced scan tools (i.e., tools that are not 

generic SAE J1978 scan tools) to determine conditions necessary to 

erase the permanent fault code. 

(E) If alternate criteria to erase the permanent fault code are approved by the 

Executive Officer under section (d)(2.5.2)(D), a manufacturer may 

continue to use the approved alternate criteria for 2011 model year 

vehicles previously certified in the 2009 or 2010 model year to the 

alternate criteria and carried over to the 2011 model year. 

(3) Monitoring Conditions. 

Section (d)(3) sets forth the general monitoring requirements while sections (e) 

and (f) set forth the specific monitoring requirements as well as identify which of 

the following general monitoring requirements in section (d)(3) are applicable for 

each monitored component or system identified in sections (e) and (f). 

(3.1) For all 2004 and subsequent model year vehicles: 

(3.1.1) As specifically provided for in sections (e) and (f), manufacturers shall 

define monitoring conditions, subject to Executive Officer approval, for 

detecting malfunctions identified in sections (e) and (f). The Executive 

Officer shall approve manufacturer defined monitoring conditions that are 

determined (based on manufacturer submitted data and/or other 

engineering documentation) to be: technically necessary to ensure robust 

detection of malfunctions (e.g., avoid false passes and false indications of 

malfunctions), designed to ensure monitoring will occur under conditions 

which may reasonably be expected to be encountered in normal urban 

vehicle operation and use, and designed to ensure monitoring will occur 

during the FTP cycle or Unified cycle. 

(3.1.2) Monitoring shall occur at least once per driving cycle in which the 
13

monitoring conditions are met. 

(3.1.3) Manufacturers may request Executive Officer approval to define 

monitoring conditions that are not encountered during the FTP cycle or 

Unified cycle as required in section (d)(3.1.1). In evaluating the 

manufacturer's request, the Executive Officer shall consider the degree to 

which the requirement to run during the FTP or Unified cycle restricts inuse monitoring, the technical necessity for defining monitoring conditions 

that are not encountered during the FTP or Unified cycle, data and/or an 

engineering evaluation submitted by the manufacturer which demonstrate 

that the component/system does not normally function, or monitoring is 

otherwise not feasible, during the FTP or Unified cycle, and, where 

applicable in section (d)(3.2), the ability of the manufacturer to 

demonstrate the monitoring conditions will satisfy the minimum acceptable 

in-use monitor performance ratio requirement as defined in section 

(d)(3.2) (e.g., data which show in-use driving meets the minimum 

requirements). 

(3.2) As specifically provided for in sections (e) and (f), manufacturers shall define 

monitoring conditions in accordance with the criteria in sections (d)(3.2.1) 

through (3.2.3). The requirements of section (d)(3.2) shall be phased in as 

follows: 30 percent of all 2005 model year vehicles, 60 percent of all 2006 

model year vehicles, and 100 percent of all 2007 and subsequent model year 

vehicles. Manufacturers may use an alternate phase-in schedule in lieu of 

the required phase-in schedule if the alternate phase-in schedule provides for 

equivalent compliance volume as defined in section (c) with the exception 

that 100 percent of 2007 and subsequent model year vehicles shall comply 

with the requirements. Small volume manufacturers shall meet the 

requirements on 100 percent of 2007 and subsequent model year vehicles 

but shall not be required to meet the specific phase-in requirements for the 

2005 and 2006 model years. 

(3.2.1) Manufacturers shall define monitoring conditions that, in addition to 

meeting the criteria in section (d)(3.1), ensure that the monitor yields an 

in-use performance ratio (as defined in section (d)(4)) that meets or 

exceeds the minimum acceptable in-use monitor performance ratio on inuse vehicles. For purposes of this regulation, except as provided below in 

section (d)(3.2.1)(D), the minimum acceptable in-use monitor performance 

ratio is: 

(A) 0.260 for secondary air system monitors and other cold start related 

monitors utilizing a denominator incremented in accordance with section 

(d)(4.3.2)(E); 

(B) For evaporative system monitors: 

(i) 0.260 for monitors designed to detect malfunctions identified in section 

(e)(4.2.2)(C) (i.e., 0.020 inch leak detection); and 

(ii) 0.520 for monitors designed to detect malfunctions identified in section 

(e)(4.2.2)(A) and (B) (i.e., purge flow and 0.040 inch leak detection); 

(C) 0.336 for catalyst, oxygen sensor, EGR, VVT system, and all other 

monitors specifically required in sections (e) and (f) to meet the monitoring 

condition requirements of section (d)(3.2); 

(D) For introductory years: 
14

(i) through the 2007 model year, for the first three years a vehicle is 

certified to the in-use performance ratio monitoring requirements of 

section (d)(3.2), 0.100 for all monitors specified in section (d)(3.2.1)(A) 

through (C) above. For example, the 0.100 ratio shall apply to the 

2004, 2005, and 2006 model years for vehicles first certified in the 

2004 model year and to the 2007, 2008, and 2009 model years for 

vehicles first certified in the 2007 model year. 

(ii) through the 2014 model year, for fuel system air-fuel ratio cylinder 

imbalance monitors, 0.100; 

(iii) through the 2011 model year, for secondary exhaust gas sensor 

monitors specified in (e)(7.2.2)(C), 0.100; 

(iv) through the 2012 model year, for vehicles subject to the monitoring 

requirements of section (f), 0.100 for all monitors specified in section 

(d)(3.2.1)(C) above. 

(3.2.2) In addition to meeting the requirements of section (d)(3.2.1), 

manufacturers shall implement software algorithms in the OBD II system 

to individually track and report in-use performance of the following 

monitors in the standardized format specified in section (d)(5): 

a. Catalyst (section (e)(1.3) or, where applicable, (f)(1.3)); 

b. Oxygen/exhaust gas sensor (section (e)(7.3.1)(A) or, where 

applicable, (f)(5.3.1)(A)); 

c. Evaporative system (section (e)(4.3.2)); 

d. EGR system (section (e)(8.3.1)) and VVT system (section (e)(13.3) 

or, where applicable, (f)(6.3.1)(A), (f)(6.3.2), (f)(6.3.4), and, 

(f)(13.3)); 

e. Secondary air system (section (e)(5.3.2)(B)); 

f. PM filter (section (f)(9.3)); 

g. NOx adsorber (section (f)(8.3.1)) and NOx catalyst (section 

(f)(2.3.1)); 

h. Secondary oxygen sensor (section (e)(7.3.2)(A)); and

i. Boost pressure control system (sections (f)(7.3.2) and (f)(7.3.3)); and

j. Fuel system (section (f)(4.3.3)). 

The OBD II system is not required to track and report in-use performance 

for monitors other than those specifically identified above. 

(3.2.3) Manufacturers may not use the calculated ratio (or any element thereof) or 

any other indication of monitor frequency as a monitoring condition for any 

monitor (e.g., using a low ratio to enable more frequent monitoring 

through diagnostic executive priority or modification of other monitoring 

conditions, or using a high ratio to enable less frequent monitoring). 

(4) In-Use Monitor Performance Ratio Definition. 

(4.1) For monitors required to meet the minimum in-use monitor performance ratio 

in section (d)(3.2.1), the ratio shall be calculated in accordance with the 

following specifications for the numerator, denominator, and ratio. 

(4.2) Numerator Specifications 

(4.2.1) Definition: The numerator is defined as a measure of the number of times 

a vehicle has been operated such that all monitoring conditions necessary 

for a specific monitor to detect a malfunction have been encountered. 

(4.2.2) Specifications for incrementing: 
15

(A) Except as provided for in sections (d)(4.2.2)(E) and (F), the numerator, 

when incremented, shall be incremented by an integer of one. The 

numerator may not be incremented more than once per driving cycle. 

(B) The numerator for a specific monitor shall be incremented within ten 

seconds if and only if the following criteria are satisfied on a single driving 

cycle: 

(i) Every monitoring condition necessary for the monitor of the specific 

component to detect a malfunction and store a pending fault code has 

been satisfied, including enable criteria, presence or absence of 

related fault codes, sufficient length of monitoring time, and diagnostic 

executive priority assignments (e.g., diagnostic “A” must execute prior 

to diagnostic “B”, etc.). For the purpose of incrementing the 

numerator, satisfying all the monitoring conditions necessary for a 

monitor to determine the component is passing may not, by itself, be 

sufficient to meet this criteria; 

(ii) For monitors that require multiple stages or events in a single driving 

cycle to detect a malfunction, every monitoring condition necessary for 

all events to have completed must be satisfied; 

(iii) For monitors that require intrusive operation of components to detect a 

malfunction, a manufacturer shall request Executive Officer approval 

of the strategy used to determine that, had a malfunction been 

present, the monitor would have detected the malfunction. Executive 

Officer approval of the request shall be based on the equivalence of 

the strategy to actual intrusive operation and the ability of the strategy 

to accurately determine if every monitoring condition necessary for the 

intrusive event to occur was satisfied. 

(iv) In addition to the requirements of section (d)(4.2.2)(B)(i) through (iii) 

above, the secondary air system monitor numerator(s) shall be 

incremented if and only if the criteria in section (B) above have been 

satisfied during normal operation of the secondary air system for 

vehicles that require monitoring during normal operation (sections 

(e)(5.2.2) through (5.2.4)). Monitoring during intrusive operation of the 

secondary air system later in the same driving cycle solely for the 

purpose of monitoring may not, by itself, be sufficient to meet this 

criteria. 

(C) For monitors that can generate results in a “gray zone” or “non-detection 

zone” (i.e., results that indicate neither a passing system nor a 

malfunctioning system) or in a “non-decision zone” (e.g., monitors that 

increment and decrement counters until a pass or fail threshold is 

reached), the manufacturer shall submit a plan for appropriate 

incrementing of the numerator to the Executive Officer for review and 

approval. In general, the Executive Officer shall not approve plans that 

allow the numerator to be incremented when the monitor indicates a result 

in the “non-detection zone” or prior to the monitor reaching a decision. In 

reviewing the plan for approval, the Executive Officer shall consider data 

and/or engineering evaluation submitted by the manufacturer 

demonstrating the expected frequency of results in the “non-detection 

zone” and the ability of the monitor to accurately determine if a monitor 
16

would have detected a malfunction instead of a result in the “nondetection zone” had an actual malfunction been present. 

(D) For monitors that run or complete during engine off operation, the 

numerator shall be incremented within 10 seconds after the monitor has 

completed during engine off operation or during the first 10 seconds of 

engine start on the subsequent driving cycle. 

(E) Except as specified in section (d)(4.2.2)(F) for exponentially weighted 

moving averages, manufacturers utilizing alternate statistical MIL 

illumination protocols as allowed in section (d)(2.2.6) for any of the 

monitors requiring a numerator shall submit a plan for appropriate 

incrementing of the numerator to the Executive Officer for review and 

approval. Executive Officer approval of the plan shall be conditioned 

upon the manufacturer providing supporting data and/or engineering 

evaluation for the proposed plan, the equivalence of the incrementing in 

the manufacturer's plan to the incrementing specified in section (d)(4.2.2) 

for monitors using the standard MIL illumination protocol, and the overall 

equivalence of the manufacturer's plan in determining that the minimum 

acceptable in-use performance ratio in section (d)(3.2.1) is satisfied. 

(F) Manufacturers using an exponentially weighted moving average (EWMA) 

as the alternate statistical MIL illumination protocol approved in 

accordance with section (d)(2.2.6) shall increment the numerator as 

follows: 

(i) Following a reset or erasure of the EWMA result, the numerator may 

not be incremented until after the requisite number of decisions 

necessary for MIL illumination have been fully executed. 

(ii) After the number of decisions required in section (d)(4.2.2)(F)(i) above, 

the numerator, when incremented, shall be incremented by an integer 

of one and may not be incremented more than once per driving cycle. 

Incrementing of the numerator shall also be in accordance with 

sections (d)(4.2.2)(B), (C), and (D). 

(4.3) Denominator Specifications 

(4.3.1) Definition: The denominator is defined as a measure of the number of 

times a vehicle has been operated as defined in (d)(4.3.2). 

(4.3.2) Specifications for incrementing: 

(A) The denominator, when incremented, shall be incremented by an integer 

of one. The denominator may not be incremented more than once per 

driving cycle. 

(B) The denominator for each monitor shall be incremented within ten 

seconds if and only if the following criteria are satisfied on a single driving 

cycle: 

(i) Cumulative time since engine start is greater than or equal to 600 

seconds while at an elevation of less than 8,000 feet above sea level 

and at an ambient temperature of greater than or equal to 20 degrees 

Fahrenheit; 

(ii) Except as provided in section (d)(4.3.2)(B)(iv) below, Ccumulative 

vehicle operation at or above 25 miles per hour occurs for greater than 

or equal to 300 seconds while at an elevation of less than 8,000 feet 

above sea level and at an ambient temperature of greater than or 
17

equal to 20 degrees Fahrenheit (medium-duty vehicles with diesel 

engines certified on an engine dynamometer may use cumulative 

operation at or above 15% calculated load1150 rpm in lieu of at or 

above 25 miles per hour for purposes of this criteria); 

(iii) Continuous vehicle operation at idle (i.e., accelerator pedal released 

by driver and either vehicle speed less than or equal to one mile per 

hour or engine speed less than or equal to 200 rpm above normal 

warmed-up idle (as determined in the drive position for vehicles 

equipped with an automatic transmission)) for greater than or equal to 

30 seconds while at an elevation of less than 8,000 feet above sea 

level and at an ambient temperature of greater than or equal to 20 

degrees Fahrenheit;.

(iv) For 2004 through 2012 model year medium-duty vehicles with diesel 

engines certified on an engine dynamometer, manufacturers may use 

diesel engine operation at or above 15 percent calculated load in lieu 

of 1150 rpm for the criterion in section (d)(4.3.2)(B)(ii) above. 

(C) In addition to the requirements of section (d)(4.3.2)(B) above, the 

secondary air system monitor denominator(s) shall be incremented if and 

only if commanded “on” operation of the secondary air system occurs for 

a time greater than or equal to ten seconds. For purposes of determining 

this commanded “on” time, the OBD II system may not include time during 

intrusive operation of the secondary air system solely for the purposes of 

monitoring; 

(D) In addition to the requirements of section (d)(4.3.2)(B) above, the 

evaporative system monitor denominator(s) shall be incremented if and 

only if: 

(i) Cumulative time since engine start is greater than or equal to 600 

seconds while at an ambient temperature of greater than or equal to 

40 degrees Fahrenheit but less than or equal to 95 degrees 

Fahrenheit; and 

(ii) Engine cold start occurs with engine coolant temperature at engine 

start greater than or equal to 40 degrees Fahrenheit but less than or 

equal to 95 degrees Fahrenheit and less than or equal to 12 degrees 

Fahrenheit higher than ambient temperature at engine start. 

(E) In addition to the requirements of section (d)(4.3.2)(B) above, the 

denominator(s) for the following monitors shall be incremented if and only 

if the component or strategy is commanded “on” for a time greater than or 

equal to ten seconds: 

(i) Heated catalyst (section (e)(2)) 

(ii) Cold Start Emission Reduction Strategy (sections (e)(11) and (f)(12)) 

(iii) Components or systems that operate only at engine start-up (e.g., 

glow plugs, intake air heaters, etc.) and are subject to monitoring 

under “other emission control or source devices” (sections (e)(16) and 

(f)(16)) or comprehensive component output components (sections 

(e)(15) and (f)(15)) 

For purposes of determining this commanded “on” time, the OBD II 

system may not include time during intrusive operation of any of the 

components or strategies later in the same driving cycle solely for the 
18

purposes of monitoring. 

(F) In addition to the requirements of section (d)(4.3.2)(B) above, the 

denominator(s) for the following monitors of output components (except 

those operated only at engine start-up and subject to the requirements of 

the previous section (d)(4.3.2)(E)) shall be incremented if and only if the 

component is commanded to function (e.g., commanded “on”, “open”, 

“closed”, “locked”, etc.) on two or more occasions for greater than two 

seconds during the driving cycle or for a cumulative time greater than or 

equal to ten seconds, whichever occurs first: 

(i) Air conditioning system (section (e)(12)) 

(ii) Variable valve timing and/or control system (sections (e)(13) and 

(f)(13)) 

(iii) “Other emission control or source device” (sections (e)(16) and (f)(16)) 

(iv) Comprehensive component output component (sections (e)(15) and 

(f)(15)) (e.g., turbocharger waste-gates, variable length manifold 

runners, torque converter clutch lock-up solenoids, etc.) 

(G) For the following monitors, the denominator(s) shall be incremented by 

one if and only if, in addition to meeting the requirements of section 

(d)(4.3.2)(B) on at least one driving cycle, at least 500 cumulative miles of 

vehicle operation have been experienced since the last time the 

denominator was incremented: 

(i) Diesel NMHC converting catalyst (section (f)(1)) 

(ii) Diesel PM filter (section (f)(9)) 

(H) For monitors of the following components, the manufacturer may request 

Executive Officer approval to use alternate or additional criteria to that set 

forth in section (d)(4.3.2)(B) above for incrementing the denominator. 

Executive Officer approval of the proposed criteria shall be based on the 

equivalence of the proposed criteria in measuring the frequency of 

monitor operation relative to the amount of vehicle operation in 

accordance with the criteria in section (d)(4.3.2)(B) above: 

(i) Engine cooling system input components (sections (e)(10) and (f)(11)) 

(ii) Air conditioning system input components (section (e)(12)) 

(iii) Direct ozone reduction systems (section (e)(14)) 

(iv) “Other emission control or source devices” (sections (e)(16) and 

(f)(16)) 

(v) Comprehensive component input components that require extended 

monitoring evaluation (sections (e)(15) and (f)(15)) (e.g., stuck fuel 

level sensor rationality) 

(vi) Comprehensive component input component temperature sensor 

rationality monitors (sections (e)(15) and (f)(15)) (e.g, intake air 

temperature sensor, ambient temperature sensor, fuel temperature 

sensor) 

(vii) PM filter frequent regeneration (section (f)(9.2.2))

(I) In addition to the requirements of section (d)(4.3.2)(B) above, the 

denominator(s) for the following monitors shall be incremented if and only 

if a regeneration event is commanded for a time greater than or equal to 

ten seconds:

(i) PM filter incomplete regeneration (section (f)(9.2.3))
19

(ii) PM filter active/intrusive injection (section (f)(9.2.6))

(I)(J) For hybrid vehicles, vehicles that employ alternate engine start 

hardware or strategies (e.g., integrated starter and generators), or 

alternate fuel vehicles (e.g., dedicated, bi-fuel, or dual-fuel applications), 

the manufacturer may request Executive Officer approval to use alternate 

criteria to that set forth in section (d)(4.3.2)(B) above for incrementing the 

denominator. In general, the Executive Officer shall not approve alternate 

criteria for vehicles that only employ engine shut off at or near idle/vehicle 

stop conditions. Executive Officer approval of the alternate criteria shall 

be based on the equivalence of the alternate criteria to determine the 

amount of vehicle operation relative to the measure of conventional 

vehicle operation in accordance with the criteria in section (d)(4.3.2)(B) 

above. 

(4.4) Ratio Specifications 

(4.4.1) Definition: The ratio is defined as the numerator divided by the 

denominator. 

(4.5) Disablement of Numerators and Denominators 

(4.5.1) Within ten seconds of a malfunction that disables a monitor required to 

meet the monitoring conditions in section (d)(3.2.1) being detected (i.e., a 

pending or confirmed code is stored), the OBD II system shall disable 

further incrementing of the corresponding numerator and denominator for 

each monitor that is disabled. When the malfunction is no longer 

detected (i.e., the pending code is erased through self-clearing or through 

a scan tool command), incrementing of all corresponding numerators and 

denominators shall resume within ten seconds. 

(4.5.2) Within ten seconds of the start of a PTO (see section (c)) operation that 

disables a monitor required to meet the monitoring conditions in section 

(d)(3.2.1), the OBD II system shall disable further incrementing of the 

corresponding numerator and denominator for each monitor that is 

disabled. When the PTO operation ends, incrementing of all 

corresponding numerators and denominators shall resume within ten 

seconds. 

(4.5.3) The OBD II system shall disable further incrementing of all numerators 

and denominators within ten seconds if a malfunction of any component 

used to determine if the criteria in sections (d)(4.3.2)(B) through (D) are 

satisfied (i.e., vehicle speed, ambient temperature, elevation, idle 

operation, engine cold start, or time of operation) has been detected (i.e., 

a pending or confirmed fault code has been stored)and the corresponding 

pending fault code has been stored. Incrementing of all numerators and 

denominators shall resume within ten seconds when the malfunction is no 

longer present (e.g., pending code erased through self-clearing or by a 

scan tool command). 

(5) Standardized tracking and reporting of monitor performance. 

(5.1) For monitors required to track and report in-use monitor performance in 

section (d)(3.2.2), the performance data shall be tracked and reported in 

accordance with the specifications in sections (d)(4), (d)(5), and (g)(5). The 

OBD II system shall separately report an in-use monitor performance 

numerator and denominator for each of the following components: catalyst 
20

bank 1, catalyst bank 2, primary oxygen/exhaust gas sensor bank 1, primary 

oxygen/exhaust gas sensor bank 2, evaporative 0.020 inch leak detection 

system, EGR/VVT system, secondary air system, diesel fuel system, PM 

filter, NOx aftertreatment (e.g., NOx adsorber, NOx catalyst), secondary 

oxygen sensor, and boost pressure control system. The OBD II system shall 

also report a general denominator and an ignition cycle counter in the 

standardized format specified in sections (d)(5.5), (d)(5.6) and (g)(5). 

(5.2) Numerator 

(5.2.1) The OBD II system shall report a separate numerator for each of the 

components listed in section (d)(5.1). 

(5.2.2) For specific components or systems that have multiple monitors that are 

required to be reported under sections (e) or (f) (e.g., oxygen sensor bank 

1 may have multiple monitors for sensor response or other sensor 

characteristics), the OBD II system shall separately track numerators and 

denominators for each of the specific monitors and report only the 

corresponding numerator and denominator for the specific monitor that 

has the lowest numerical ratio. If two or more specific monitors have 

identical ratios, the corresponding numerator and denominator for the 

specific monitor that has the highest denominator shall be reported for the 

specific component. 

(5.2.3) The numerator(s) shall be reported in accordance with the specifications 

in section (g)(5.2.1). 

(5.3) Denominator 

(5.3.1) The OBD II system shall report a separate denominator for each of the 

components listed in section (d)(5.1). 

(5.3.2) The denominator(s) shall be reported in accordance with the 

specifications in section (g)(5.2.1). 

(5.4) Ratio 

(5.4.1) For purposes of determining which corresponding numerator and 

denominator to report as required in section (d)(5.2.2), the ratio shall be 

calculated in accordance with the specifications in section (g)(5.2.2). 

(5.5) Ignition cycle counter 

(5.5.1) Definition: 

(A) The ignition cycle counter is defined as a counter that indicates the 

number of ignition cycles a vehicle has experienced as defined in section 

(d)(5.5.2)(B). 

(B) The ignition cycle counter shall be reported in accordance with the 

specifications in section (g)(5.2.1). 

(5.5.2) Specifications for incrementing: 

(A) The ignition cycle counter, when incremented, shall be incremented by an 

integer of one. The ignition cycle counter may not be incremented more 

than once per driving cycle. 

(B) The ignition cycle counter shall be incremented within ten seconds if and 

only if the vehicle meets the engine start definition (see section (c)) for at 

least two seconds plus or minus one second. 

(C) The OBD II system shall disable further incrementing of the ignition cycle 

counter within ten seconds if a malfunction of any component used to 
21

determine if the criteria in section (d)(5.5.2)(B) are satisfied (i.e., engine 

speed or time of operation) has been detected and the corresponding 

pending fault code has been stored. The ignition cycle counter may not 

be disabled from incrementing for any other condition. Incrementing of 

the ignition cycle counter shall resume within ten seconds when the 

malfunction is no longer present (e.g., pending code erased through selfclearing or by a scan tool command). 

(5.6) General Denominator 

(5.6.1) Definition: 

(A) The general denominator is defined as a measure of the number of times 

a vehicle has been operated as defined in section (d)(5.6.2)(B). 

(B) The general denominator shall be reported in accordance with the 

specifications in section (g)(5.2.1). 

(5.6.2) Specifications for incrementing: 

(A) The general denominator, when incremented, shall be incremented by an 

integer of one. The general denominator may not be incremented more 

than once per driving cycle. 

(B) The general denominator shall be incremented within ten seconds if and 

only if the criteria identified in section (d)(4.3.2)(B) are satisfied on a single 

driving cycle. 

(C) The OBD II system shall disable further incrementing of the general 

denominator within ten seconds if a malfunction of any component used 

to determine if the criteria in section (d)(4.3.2)(B) are satisfied (i.e., vehicle 

speed, ambient temperature, elevation, idle operation, or time of 

operation) has been detected and the corresponding pending fault code 

has been stored. The general denominator may not be disabled from 

incrementing for any other condition (e.g., the disablement criteria in 

sections (d)(4.5.1) and (d)(4.5.2) may not disable the general 

denominator). Incrementing of the general denominator shall resume 

within ten seconds when the malfunction is no longer present (e.g., 

pending code erased through self-clearing or by a scan tool command). 

(6) Malfunction Criteria Determination for Diesel Vehicles. 

(6.1) For 2010 and subsequent model year medium-duty vehicles certified to an 

engine dynamometer exhaust emission standard, in determining the 

malfunction criteria for diesel engine monitors in section (f) that are required 

to indicate a malfunction before emissions exceed an emission threshold 

based on the applicable standard, the manufacturer shall: 

(6.1.1) Use the emission test cycle and standard (i.e., FTP or SET) determined 

by the manufacturer, through use of data and/or engineering analysis, to 

be more stringent (i.e., to result in higher emissions with the same level of 

monitored component malfunction) as the “applicable standard”. 

(6.1.2) Identify in the certification documentation required under section (i) the 

test cycle and standard determined by the manufacturer to be more 

stringent for each applicable monitor. 

(6.1.3) If the Executive Officer reasonably believes that a manufacturer has 

incorrectly determined the test cycle and standard that is more stringent, 

the Executive Officer shall require the manufacturer to provide emission 
22

data and/or engineering analysis showing that the other test cycle and 

standard are less stringent. 

(6.2) For 2007 and subsequent model year light-duty and medium-duty vehicles 

equipped with emission controls that experience infrequent regeneration 

events (e.g., active PM filter regeneration, NOx adsorber desulfation), a 

manufacturer shall adjust the emission test results that are used to determine 

the malfunction criterion for monitors that are required to indicate a 

malfunction before emissions exceed a certain emission threshold. Except 

as provided in section (d)(6.2.7), Ffor each monitor on medium-duty vehicles 

using engines certified on an engine dynamometer, the manufacturer shall 

adjust the emission result using the procedure described in CFR title 40, part 

86.004-28(i) with the component for which the malfunction criteria is being 

established deteriorated to the malfunction threshold. For light-duty and 

medium-duty vehicles certified on a chassis dynamometer, the manufacturer 

shall submit a plan for Executive Officer approval to adjust the emission 

results using an approach similar to the procedure described in CFR title 40, 

part 86.004-28(i). Executive Officer approval shall be based on the 

effectiveness of the proposed plan to quantify the emission impact and 

frequency of regeneration events. The adjusted emission value shall be used 

for purposes of determining whether or not the specified emission threshold 

is exceeded (e.g., a malfunction must be detected before the adjusted 

emission value exceeds 1.5 times any applicable standard). 

(6.2.1) For purposes of section (d)(6.2), “regeneration” means an event during 

which emission levels change while the emission control performance is 

being restored by design.

(6.2.2) For purposes of section (d)(6.2), “infrequent” means having an expected 

frequency of less than once per FTP cycle.

(6.2.3) Except as specified in section (d)(6.2.4) for NMHC catalyst monitoring, for 

2007 through 2009 model year vehicles, in lieu of establishing the 

adjustment factor for each monitor with the component for which the 

malfunction criteria is being established deteriorated to the malfunction 

threshold as required in section (d)(6.2), the manufacturer may use the 

adjustment factor established for certification (e.g., without components 

deteriorated to the malfunction threshold).

(6.2.4) For NMHC catalyst monitoring (section (f)(1)) on 2008 and subsequent 

model year vehicles, a manufacturer shall establish the adjustment factor 

for the NMHC catalyst monitor with the NMHC catalyst deteriorated to the 

malfunction threshold as required in section (d)(6.2). In lieu of 

establishing this adjustment factor for 2008 and 2009 model year vehicles, 

a manufacturer may provide emission data demonstrating that the worst 

case emission levels from a deteriorated NMHC catalyst are below the 

malfunction threshold specified in section (f)(1.2.2). The demonstration 

shall include emission testing with a NMHC catalyst deteriorated to the 

malfunction threshold or worse and with both the infrequent regeneration 

event occurring and without it occurring. The manufacturer shall calculate 

the worst case emission level by applying the frequency factor (“F” as 

calculated according to CFR, title 40, part 86.004-28(i)) of the infrequent 

regeneration event used for tailpipe certification to the measured 
23

emissions with the infrequent regeneration event occurring and adding 

that result to the measured emissions without the infrequent regeneration 

event occurring. This calculated final sum shall be used as the adjusted 

emission level and compared to the malfunction threshold for purposes of 

determining compliance with the monitoring requirements. The 

manufacturer shall submit a test plan for Executive Officer approval 

describing the emission testing procedure and how the worst case 

components will be established. The Executive Officer shall approve it 

upon finding the test procedure and components used will likely generate 

a worst case emission level.

(6.2.5) For purposes of determining the adjustment factors for each monitor, the 

manufacturer shall submit engineering data, analysis, and/or emission 

data to the Executive Officer for approval. The Executive Officer shall 

approve the factors upon finding the submitted information supports the 

adjustment factors.

(6.2.6) For purposes of enforcement testing in accordance with section (d)(7) and 

title 13, CCR section 1968.5, the adjustment factors established for each 

monitor by the manufacturer according to section (d)(6.2) shall be used 

when determining compliance with emission thresholds.

(6.2.7) In lieu of using the procedure described in CFR title 40, part 86.004-28(i), 

the manufacturer may submit an alternate plan to calculate the 

adjustment factors for determining the adjusted emission values to the 

Executive Officer for review and approval. Executive Officer approval of 

the plan shall be conditioned upon the manufacturer providing data and/or 

engineering evaluation demonstrating the procedure is consistent with 

good engineering judgment in determining appropriate modifications to 

the tailpipe certification adjustment factors.

(6.3) For every 2007 through 2012 model year light-duty vehicle test group certified 

to the higher allowable emission thresholds specified in section (f) (e.g., 5.0 

or 3.0 times the applicable standards for NMHC converting catalyst 

monitoring) for vehicles prior to the 2013 model year: 

(6.3.1) The manufacturer shall conduct in-use enforcement testing for compliance 

with the tailpipe emission standards in accordance with title 13, CCR 

sections 2136 through 2140. Within six months after OBD II certification 

of a test group, the manufacturer shall submit a plan for conducting the 

testing to the Executive Officer for approval. The Executive Officer shall 

approve the plan upon determining that the testing will be done in 

accordance with the procedures used by ARB when conducting such 

testing, that the plan will allow for a valid sample of at least 10 vehicles in 

the mileage range of 30,000 to 40,000 miles for comparison to the FTP 

intermediate (e.g., 50,000 mile) useful life standard and at least 10 

vehicles in the mileage range of 90,000 to 100,000 miles for comparison 

to the FTP full useful life standard, and that copies of all records and data 

collected during the program will be provided to ARB. Manufacturers may 

also submit testing plans and supporting data for Executive Officer 

approval that differ from compliance testing under title 13, CCR, sections 

2136 through 2140. The Executive Officer shall also approve the plans 

upon determining that the plan provides equivalent assurance in verifying 
24

vehicles are meeting the tailpipe emission standards within the useful life. 

 The Executive Officer may use the submitted data in lieu of or in addition 

to data collected pursuant to title 13, CCR section 2139 for purposes of 

the notification and use of test results described in title 13, CCR section 

2140; and

(6.3.2) The certification shall be conditioned upon the manufacturer agreeing 

that, for any test group(s) determined to be noncompliant in accordance 

with title 13, CCR section 2140 or title 13, CCR section 1968.5, the 

Executive Officer shall determine the excess emissions caused by the 

noncompliance and the manufacturer shall fund a program(s) that will 

offset any such excess emissions. 

(7) Enforcement Testing. 

(7.1) The procedures used to assure compliance with the requirements of title 13, 

CCR section 1968.2 are set forth in title 13, CCR section 1968.5. 

(7.2) Consistent with the requirements of title 13, CCR section 1968.5(b)(4)(A) for 

enforcement OBD II emission testing, the manufacturer shall make available 

upon request by the Executive Officer all test equipment (e.g., malfunction 

simulators, deteriorated “threshold” components, etc.) necessary to 

determine the malfunction criteria in sections (e) and (f) for major monitors 

subject to OBD II emission testing as defined in title 13, CCR section 1968.5. 

 To meet the requirements of this section, the manufacturers shall only be 

required to make available test equipment necessary to duplicate “threshold” 

testing performed by the manufacturer. This test equipment shall include, but 

is not limited to, aged “threshold” catalyst systems and computer equipment 

used to simulate misfire, oxygen sensor, fuel system, VVT system, and cold 

start reduction strategy system faults. The manufacturer is not required to 

make available test equipment for vehicles that exceed the applicable full 

useful life age (e.g., 10 years for vehicles certified to a full useful life of 10 

years and 100,000 miles). 

(e) MONITORING REQUIREMENTS FOR GASOLINE/SPARK-IGNITED ENGINES. 

(1) CATALYST MONITORING

(1.1) Requirement: The OBD II system shall monitor the catalyst system for proper 

conversion capability. 

(1.2) Malfunction Criteria: 

(1.2.1) Low Emission Vehicle I applications: The OBD II system shall detect a 

catalyst system malfunction when the catalyst system’s conversion 

capability decreases to the point that either of the following occurs: 

(A) Non-Methane Organic Gas (NMOG) emissions exceed 1.75 times the 

FTP full useful life standards to which the vehicle has been certified with 

NMOG emissions multiplied by the certification reactivity adjustment factor 

for the vehicle; 

(B) The average FTP test Non-Methane Hydrocarbon (NMHC) conversion 

efficiency of the monitored portion of the catalyst system falls below 50 

percent (i.e., the cumulative NMHC emissions measured at the outlet of 

the monitored catalyst(s) are more than 50 percent of the cumulative 

engine-out emissions measured at the inlet of the catalyst(s)). With 

Executive Officer approval, manufacturers may use a conversion 
25

efficiency malfunction criteria of less than 50 percent if the catalyst system 

is designed such that the monitored portion of the catalyst system must be 

replaced along with an adjacent portion of the catalyst system sufficient to 

ensure that the total portion replaced will meet the 50 percent conversion 

efficiency criteria. Executive Officer approval shall be based on data 

and/or engineering evaluation demonstrating the conversion efficiency of 

the monitored portion and the total portion designed to be replaced, and 

the likelihood of the catalyst system design to ensure replacement of the 

monitored and adjacent portions of the catalyst system. 

(1.2.2) Low Emission Vehicle II applications and all 2009 and subsequent model 

year vehicles: 

(A) 2004 model year vehicles. 

(i) All LEV II, ULEV II, and MDV SULEV II vehicles shall use the 

malfunction criteria specified for Low Emission Vehicle I applications in 

section (e)(1.2.1). 

(ii) All PC/LDT SULEV II vehicles shall use the malfunction criteria 

specified for Low Emission Vehicle I applications in section (e)(1.2.1) 

except the malfunction criterion in paragraph (e)(1.2.1)(A) shall be 2.5 

times the applicable FTP full useful life NMOG standard. 

(B) Except as provided below in section (e)(1.2.4), for 2005 through 2008 

model years, the OBD II system shall detect a catalyst system malfunction 

when the catalyst system’s conversion capability decreases to the point 

that any of the following occurs: 

(i) For all vehicles other than PC/LDT SULEV II vehicles. 

a. NMOG emissions exceed the criteria specified for Low Emission 

Vehicle I applications in section (e)(1.2.1)(A). 

b. The average FTP test NMHC conversion efficiency is below the 

criteria specified for Low Emission Vehicle I applications in section 

(e)(1.2.1)(B). 

c. Oxides of nitrogen (NOx) emissions exceed 3.5 times the FTP full 

useful life NOx standard to which the vehicle has been certified. 

(ii) PC/LDT SULEV II vehicles shall use the same malfunction criteria as 

2005 through 2008 model year LEV II, ULEV II, and MDV SULEV II 

vehicles (section (e)(1.2.2)(B)(i)) except the malfunction criteria in 

paragraph a. shall be 2.5 times the applicable FTP full useful life 

NMOG standard. 

(C) Except as provided below in section (e)(1.2.5), for 2009 and subsequent 

model years, the OBD II system shall detect a catalyst system malfunction 

when the catalyst system’s conversion capability decreases to the point 

that any of the following occurs. 

(i) For all vehicles other than PC/LDT SULEV II vehicles. 

a. NMOG emissions exceed the criteria specified for Low Emission 

Vehicle I applications in section (e)(1.2.1)(A). 

b. The average FTP test NMHC conversion efficiency is below the 

criteria specified for Low Emission Vehicle I applications in section 

(e)(1.2.1)(B). 

c. NOx emissions exceed 1.75 times the FTP full useful life NOx 

standard to which the vehicle has been certified. 
26

(ii) For PC/LDT SULEV II vehicles. 

a. NMOG emissions exceed 2.5 times the applicable FTP full useful 

life NMOG standard to which the vehicle has been certified. 

b. The average FTP test NMHC conversion efficiency is below the 

criteria specified for Low Emission Vehicle I applications in section 

(e)(1.2.1)(B). 

c. NOx emissions exceed 2.5 times the applicable FTP full useful life 

NOx standard to which the vehicle has been certified. 

(1.2.3) 2004 through 2008 model year non-Low Emission Vehicle I or II 

applications: The OBD II system shall detect a catalyst system 

malfunction when the catalyst system’s conversion capability decreases to 

the point that NMHC emissions increase by more than 1.5 times the 

applicable FTP full useful life standards over an FTP test performed with a 

representative 4000 mile catalyst system. 

(1.2.4) In lieu of using the malfunction criteria in section (e)(1.2.2)(B) for all 2005 

and 2006 model year Low Emission Vehicle II applications, a 

manufacturer may phase-in the malfunction criteria on a portion of its Low 

Emission Vehicle II applications as long as that portion of Low Emission 

Vehicle II applications comprises at least 30 percent of all 2005 model 

year vehicles and 60 percent of all 2006 model year vehicles. For 2005 

and 2006 model year Low Emission Vehicle II applications not included in 

the phase-in, the malfunction criteria in section (e)(1.2.2)(A) shall be used. 

(1.2.5) In lieu of using the malfunction criteria in section (e)(1.2.2)(C) for all 2009 

model year vehicles, for the 2009 model year only, a manufacturer may 

continue to use the malfunction criteria in section (e)(1.2.2)(B) for any 

vehicles previously certified in the 2005, 2006, 2007, or 2008 model year 

to the malfunction criteria in section (e)(1.2.2.)(B) and carried over to the 

2009 model year. 

(1.2.6) For purposes of determining the catalyst system malfunction criteria in 

sections (e)(1.2.1), (1.2.2)(A), and (1.2.3), the malfunction criteria shall be 

established by using a catalyst system with all monitored catalysts 

simultaneously deteriorated to the malfunction criteria while unmonitored 

catalysts shall be deteriorated to the end of the vehicle's full useful life. 

(1.2.7) For purposes of determining the catalyst system malfunction criteria in 

sections (e)(1.2.2)(B) and (C): 

(A) The manufacturer shall use a catalyst system deteriorated to the 

malfunction criteria using methods established by the manufacturer to 

represent real world catalyst deterioration under normal and 

malfunctioning operating conditions. 

(B) Except as provided below in section (e)(1.2.7)(C), the malfunction criteria 

shall be established by using a catalyst system with all monitored and 

unmonitored (downstream of the sensor utilized for catalyst monitoring) 

catalysts simultaneously deteriorated to the malfunction criteria. 

(C) For vehicles using fuel shutoff to prevent over-fueling during misfire 

conditions (see section (e)(3.4.1)(D)), the malfunction criteria shall be 

established by using a catalyst system with all monitored catalysts 

simultaneously deteriorated to the malfunction criteria while unmonitored 

catalysts shall be deteriorated to the end of the vehicle's full useful life. 
27

(1.3) Monitoring Conditions: Manufacturers shall define the monitoring conditions 

for malfunctions identified in section (e)(1.2) in accordance with sections 

(d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). For purposes of 

tracking and reporting as required in section (d)(3.2.2), all monitors used to 

detect malfunctions identified in section (e)(1.2) shall be tracked separately 

but reported as a single set of values as specified in section (d)(5.2.2). 

(1.4) MIL Illumination and Fault Code Storage: 

(1.4.1) General requirements for MIL illumination and fault code storage are set 

forth in section (d)(2). 

(1.4.2) The monitoring method for the catalyst(s) shall be capable of detecting 

when a catalyst fault code has been cleared (except OBD II system 

self-clearing), but the catalyst has not been replaced (e.g., catalyst 

overtemperature approaches may not be acceptable). 

(2) HEATED CATALYST MONITORING

(2.1) Requirement: 

(2.1.1) The OBD II system shall monitor all heated catalyst systems for proper 

heating. 

(2.1.2) The efficiency of heated catalysts shall be monitored in conjunction with 

the requirements of section (e)(1). 

(2.2) Malfunction Criteria: 

(2.2.1) The OBD II system shall detect a catalyst heating system malfunction 

when the catalyst does not reach its designated heating temperature 

within a requisite time period after engine starting. The manufacturer shall 

determine the requisite time period, but the time period may not exceed 

the time that would cause emissions from a vehicle equipped with the 

heated catalyst system to exceed 1.75 times any of the applicable FTP full 

useful life standards. 

(2.2.2) Manufacturers may use other monitoring strategies for the heated catalyst 

but must submit the alternate plan to the Executive Officer for approval. 

The Executive Officer shall approve alternate strategies for monitoring 

heated catalyst systems based on comparable reliability and timeliness to 

these requirements in detecting a catalyst heating malfunction. 

(2.3) Monitoring Conditions: Manufacturers shall define the monitoring conditions 

for malfunctions identified in section (e)(2.2) in accordance with sections 

(d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). 

(2.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(3) MISFIRE MONITORING

(3.1) Requirement: 

(3.1.1) The OBD II system shall monitor the engine for misfire causing catalyst 

damage and misfire causing excess emissions. 

(3.1.2) The OBD II system shall identify the specific cylinder that is experiencing 

misfire. Manufacturers may request Executive Officer approval to store a 

general misfire fault code instead of a cylinder specific fault code under 

certain operating conditions. The Executive Officer shall approve the 
28

request upon determining that the manufacturer has submitted data 

and/or an engineering evaluation that demonstrate that the misfiring 

cylinder cannot be reliably identified when the conditions occur. 

(3.1.3) If more than one cylinder is misfiring, a separate fault code shall be stored 

indicating that multiple cylinders are misfiring except as allowed below. 

When identifying multiple cylinder misfire, the manufacturer is not required 

to also identify each of the misfiring cylinders individually through separate 

fault codes. For 2005 and subsequent model year vehicles, if more than 

90 percent of the detected misfires occur in a single cylinder, the 

manufacturer may elect to store the appropriate fault code indicating the 

specific misfiring cylinder in lieu of the multiple cylinder misfire fault code. 

If, however, two or more cylinders individually have more than 10 percent 

of the total number of detected misfires, a multiple cylinder fault code 

must be stored. 

(3.2) Malfunction Criteria: The OBD II system shall detect a misfire malfunction 

pursuant to the following: 

(3.2.1) Misfire causing catalyst damage:

(A) Manufacturers shall determine the percentage of misfire evaluated in 200 

revolution increments for each engine speed and load condition that 

would result in a temperature that causes catalyst damage. The 

manufacturer shall submit documentation to support this percentage of 

misfire as required in section (i)(2.5). For every engine speed and load 

condition that this percentage of misfire is determined to be lower than 

five percent, the manufacturer may set the malfunction criteria at five 

percent.

(B) Subject to Executive Officer approval, a manufacturer may employ a 

longer interval than 200 revolutions but only for determining, on a given 

driving cycle, the first misfire exceedance as provided in section 

(e)(3.4.1)(A) below. Executive Officer approval shall be granted upon 

determining that the manufacturer has submitted data and/or an 

engineering evaluation that demonstrate that catalyst damage would not 

occur due to unacceptably high catalyst temperatures before the interval 

has elapsed.

(C) A misfire malfunction shall be detected if the percentage of misfire 

established in section (e)(3.2.1)(A) is exceeded. 

(D) For purposes of establishing the temperature at which catalyst damage 

occurs as required in section (e)(3.2.1)(A), on 2005 and subsequent 

model year vehicles, manufacturers may not define catalyst damage at a 

temperature more severe than what the catalyst system could be 

operated at for ten consecutive hours and still meet the applicable FTP 

full useful life standards.

(3.2.2) Misfire causing emissions to exceed 1.5 times the FTP standards: 

(A) Manufacturers shall determine the percentage of misfire evaluated in 

1000 revolution increments that would cause emissions from an emission 

durability demonstration vehicle to exceed 1.5 times any of the applicable 

FTP standards if the percentage of misfire were present from the 

beginning of the test. To establish this percentage of misfire, the 

manufacturer shall utilize misfire events occurring at equally spaced, 
29

complete engine cycle intervals, across randomly selected cylinders 

throughout each 1000-revolution increment. If this percentage of misfire 

is determined to be lower than one percent, the manufacturer may set the 

malfunction criteria at one percent. 

(B) Subject to Executive Officer approval, a manufacturer may employ other 

revolution increments. The Executive Officer shall grant approval upon 

determining that the manufacturer has demonstrated that the strategy 

would be equally effective and timely in detecting misfire. 

(C) A malfunction shall be detected if the percentage of misfire established in 

section (3.2.2)(A) is exceeded regardless of the pattern of misfire events 

(e.g., random, equally spaced, continuous, etc.). 

(3.3) Monitoring Conditions: 

(3.3.1) Manufacturers shall continuously monitor for misfire under the following 

conditions: 

(A) From no later than the end of the second crankshaft revolution after 

engine start, 

(B) While under positive torque conditions during the rise time and settling 

time for engine speed to reach the desired idle engine speed at engine 

start-up (i.e., “flare-up” and “flare-down”), and 

(C) Under all positive torque engine speeds and load conditions except within 

the following range: the engine operating region bound by the positive 

torque line (i.e., engine load with the transmission in neutral), and the two 

following engine operating points: an engine speed of 3000 rpm with the 

engine load at the positive torque line, and the redline engine speed 

(defined in section (c)) with the engine's manifold vacuum at four inches of 

mercury lower than that at the positive torque line. 

(3.3.2) If a monitoring system cannot detect all misfire patterns under all required 

engine speed and load conditions as required in section (e)(3.3.1) above, 

the manufacturer may request Executive Officer approval to accept the 

monitoring system. In evaluating the manufacturer’s request, the 

Executive Officer shall consider the following factors: the magnitude of the 

region(s) in which misfire detection is limited, the degree to which misfire 

detection is limited in the region(s) (i.e., the probability of detection of 

misfire events), the frequency with which said region(s) are expected to be 

encountered in-use, the type of misfire patterns for which misfire detection 

is troublesome, and demonstration that the monitoring technology 

employed is not inherently incapable of detecting misfire under required 

conditions (i.e., compliance can be achieved on other engines). The 

evaluation shall be based on the following misfire patterns: equally spaced 

misfire occurring on randomly selected cylinders, single cylinder 

continuous misfire, and paired cylinder (cylinders firing at the same crank 

angle) continuous misfire. 

(3.3.3) A manufacturer may request Executive Officer approval of a monitoring 

system that has reduced misfire detection capability during the portion of 

the first 1000 revolutions after engine start that a cold start emission 

reduction strategy that reduces engine torque (e.g., spark retard 

strategies) is active. The Executive Officer shall approve the request 

upon determining that the manufacturer has demonstrated that the 
30

probability of detection is greater than or equal to 75 percent during the 

worst case condition (i.e., lowest generated torque) for a vehicle operated 

continuously at idle (park/neutral idle) on a cold start between 50-86 

degrees Fahrenheit and that the technology cannot reliably detect a 

higher percentage of the misfire events during the conditions. 

(3.3.4) A manufacturer may request Executive Officer approval to disable misfire 

monitoring or employ an alternate malfunction criterion when misfire 

cannot be distinguished from other effects. 

(A) Upon determining that the manufacturer has presented documentation 

that demonstrates the disablement interval or period of use of an alternate 

malfunction criterion is limited only to that necessary for avoiding false 

detection, the Executive Officer shall approve the disablement or use of 

the alternate malfunction criterion for conditions involving: 

(i) rough road, 

(ii) fuel cut, 

(iii) gear changes for manual transmission vehicles, 

(iv) traction control or other vehicle stability control activation such as antilock braking or other engine torque modifications to enhance vehicle 

stability, 

(v) off-board control or intrusive activation of vehicle components or 

diagnostics during service or assembly plant testing, 

(vi) portions of intrusive evaporative system or EGR diagnostics that can 

significantly affect engine stability (i.e., while the purge valve is open 

during the vacuum pull-down of a evaporative system leak check but 

not while the purge valve is closed and the evaporative system is 

sealed or while an EGR diagnostic causes the EGR valve to be 

intrusively cycled on and off during positive torque conditions), or 

(vii) engine speed, load, or torque transients due to throttle movements 

more rapid than occurs over the US06 cycle for the worst case vehicle 

within each test group. 

(B) Additionally, the Executive Officer will approve a manufacturer's request 

in accordance with sections (e)(17.3), (17.4), and (17.6) to disable misfire 

monitoring when fuel level is 15 percent or less of the nominal capacity of 

the fuel tank, when PTO units are active, or while engine coolant 

temperature is below 20 degrees Fahrenheit. The Executive Officer will 

approve a request to continue disablement on engine starts when engine 

coolant temperature is below 20 degrees Fahrenheit at engine start until 

engine coolant temperature exceeds 70 degrees Fahrenheit. 

(C) In general, for 2005 and subsequent model year vehicles, the Executive 

Officer shall not approve disablement for conditions involving normal air 

conditioning compressor cycling from on-to-off or off-to-on, automatic 

transmission gear shifts (except for shifts occurring during wide open 

throttle operation), transitions from idle to off-idle, normal engine speed or 

load changes that occur during the engine speed rise time and settling 

time (i.e., “flare-up” and “flare-down”) immediately after engine starting 

without any vehicle operator-induced actions (e.g., throttle stabs), or 

excess acceleration (except for acceleration rates that exceed the 
31

maximum acceleration rate obtainable at wide open throttle while the 

vehicle is in gear due to abnormal conditions such as slipping of a clutch). 

(D) The Executive Officer may approve misfire monitoring disablement or use 

of an alternate malfunction criterion for any other condition on a case by 

case basis upon determining that the manufacturer has demonstrated that 

the request is based on an unusual or unforeseen circumstance and that 

it is applying the best available computer and monitoring technology. 

(3.3.5) For engines with more than eight cylinders that cannot meet the 

requirements of section (e)(3.3.1), a manufacturer may request Executive 

Officer approval to use alternative misfire monitoring conditions. The 

Executive Officer shall approve the request upon determining that the 

manufacturer has submitted data and/or an engineering evaluation which 

demonstrate that misfire detection throughout the required operating 

region cannot be achieved when employing proven monitoring technology 

(i.e., a technology that provides for compliance with these requirements 

on other engines) and provided misfire is detected to the fullest extent 

permitted by the technology. However, the Executive Officer may not 

grant the request if the misfire detection system is unable to monitor 

during all positive torque operating conditions encountered during an FTP 

cycle. 

(3.4) MIL Illumination and Fault Code Storage: 

(3.4.1) Misfire causing catalyst damage. Upon detection of the percentage of misfire 

specified in section (e)(3.2.1) above, the following criteria shall apply for MIL 

illumination and fault code storage: 

(A) Pending fault codes 

(i) A pending fault code shall be stored immediately if, during a single 

driving cycle, the specified percentage of misfire is exceeded three 

times when operating in the positive torque region encountered during 

an FTP cycle or is exceeded on a single occasion when operating at 

any other engine speed and load condition in the positive torque 

region defined in section (e)(3.3.1). 

(ii) Immediately after a pending fault code is stored as specified in section 

(e)(3.4.1)(A)(i) above, the MIL shall blink once per second at all times 

while misfire is occurring during the driving cycle. 

a. The MIL may be extinguished during those times when misfire is not 

occurring during the driving cycle. 

b. If, at the time a misfire malfunction occurs, the MIL is already 

illuminated for a malfunction other than misfire, the MIL shall blink 

as previously specified in section (e)(3.4.1)(A)(ii) while misfire is 

occurring. If misfiring ceases, the MIL shall stop blinking but 

remain illuminated as required by the other malfunction. 

(B) Confirmed fault codes 

(i) If a pending fault code for exceeding the percentage of misfire set forth 

in section (e)(3.2.1) is stored, the OBD II system shall immediately 

store a confirmed fault code if the percentage of misfire specified in 

section (e)(3.2.1) is again exceeded one or more times during either: 

(a) the driving cycle immediately following the storage of the pending 

fault code, regardless of the conditions encountered during the driving 
32

cycle; or (b) on the next driving cycle in which similar conditions (see 

section (c)) to the engine conditions that occurred when the pending 

fault code was stored are encountered. 

(ii) If a pending fault code for exceeding the percentage of misfire set forth 

in section (e)(3.2.2) is stored from a previous drive cycle, the OBD II 

system shall immediately store a confirmed fault code if the 

percentage of misfire specified in section (e)(3.2.1) is exceeded one or 

more times regardless of the conditions encountered. 

(iii) Upon storage of a confirmed fault code, the MIL shall blink as 

specified in subparagraph (e)(3.4.1)(A)(ii) above as long as misfire is 

occurring and the MIL shall remain continuously illuminated if the 

misfiring ceases. 

(C) Erasure of pending fault codes 

Pending fault codes shall be erased at the end of the next driving cycle in 

which similar conditions to the engine conditions that occurred when the 

pending fault code was stored have been encountered without any 

exceedance of the specified percentage of misfire. The pending code 

may also be erased if similar driving conditions are not encountered 

during the next 80 driving cycles subsequent to the initial detection of a 

malfunction. 

(D) Exemptions for vehicles with fuel shutoff and default fuel control. 

Notwithstanding sections (e)(3.4.1)(A) and (B) above, in vehicles that 

provide for fuel shutoff and default fuel control to prevent over fueling 

during catalyst damage misfire conditions, the MIL need not blink. 

Instead, the MIL may illuminate continuously in accordance with the 

requirements for continuous MIL illumination in sections (e)(3.4.1)(B)(iii) 

above upon detection of misfire, provided that the fuel shutoff and default 

control are activated as soon as misfire is detected. Fuel shutoff and 

default fuel control may be deactivated only to permit fueling outside of 

the misfire range. Manufacturers may also periodically, but not more than 

once every 30 seconds, deactivate fuel shutoff and default fuel control to 

determine if the specified percentage of misfire for catalyst damage is still 

being exceeded. Normal fueling and fuel control may be resumed if the 

specified percentage of misfire for catalyst damage is no longer being 

exceeded. 

(E) Manufacturers may request Executive Officer approval of strategies that 

continuously illuminate the MIL in lieu of blinking the MIL during extreme 

catalyst damage misfire conditions (i.e., catalyst damage misfire occurring 

at all engine speeds and loads). Executive Officer approval shall be 

granted upon determining that the manufacturer employs the strategy only 

when catalyst damage misfire levels cannot be avoided during reasonable 

driving conditions and the manufacturer has demonstrated that the 

strategy will encourage operation of the vehicle in conditions that will 

minimize catalyst damage (e.g., at low engine speeds and loads). 

(3.4.2) Misfire causing emissions to exceed 1.5 times the FTP standards. Upon 

detection of the percentage of misfire specified in section (e)(3.2.2), the 

following criteria shall apply for MIL illumination and fault code storage: 
33

(A) Misfire within the first 1000 revolutions after engine start. 

(i) A pending fault code shall be stored no later than after the first 

exceedance of the specified percentage of misfire during a single 

driving cycle if the exceedance occurs within the first 1000 revolutions 

after engine start (defined in section (c)) during which misfire detection 

is active. 

(ii) If a pending fault code is stored, the OBD II system shall illuminate the 

MIL and store a confirmed fault code within ten seconds if an 

exceedance of the specified percentage of misfire is again detected in 

the first 1000 revolutions during any subsequent driving cycle, 

regardless of the conditions encountered during the driving cycle. 

(iii) The pending fault code shall be erased at the end of the next driving 

cycle in which similar conditions to the engine conditions that occurred 

when the pending fault code was stored have been encountered 

without an exceedance of the specified percentage of misfire. The 

pending code may also be erased if similar conditions are not 

encountered during the next 80 driving cycles immediately following 

the initial detection of the malfunction. 

(B) Exceedances after the first 1000 revolutions after engine start. 

(i) A pending fault code shall be stored no later than after the fourth 

exceedance of the percentage of misfire specified in section (e)(3.2.2) 

during a single driving cycle. 

(ii) If a pending fault code is stored, the OBD II system shall illuminate the 

MIL and store a confirmed fault code within ten seconds if the 

percentage of misfire specified in section (e)(3.2.2) is again exceeded 

four times during: (a) the driving cycle immediately following the 

storage of the pending fault code, regardless of the conditions 

encountered during the driving cycle; or (b) on the next driving cycle in 

which similar conditions (see section (c)) to the engine conditions that 

occurred when the pending fault code was stored are encountered. 

(iii) The pending fault code may be erased at the end of the next driving 

cycle in which similar conditions to the engine conditions that occurred 

when the pending fault code was stored have been encountered 

without an exceedance of the specified percentage of misfire. The 

pending code may also be erased if similar conditions are not 

encountered during the next 80 driving cycles immediately following 

initial detection of the malfunction. 

(3.4.3) Storage of freeze frame conditions. 

(A) A manufacturer shall store and erase freeze frame conditions either in 

conjunction with storing and erasing a pending fault code or in conjunction 

with storing and erasing a confirmed fault code. 

(B) If freeze frame conditions are stored for a malfunction other than misfire 

or fuel system malfunction (see section (e)(6)) when a fault code is stored 

as specified in section (e)(3.4) above, the stored freeze frame information 

shall be replaced with freeze frame information regarding the misfire 

malfunction. 

(3.4.4) Storage of misfire conditions for similar conditions determination. Upon 

detection of misfire under sections (e)(3.4.1) or (3.4.2), manufacturers 
34

shall store the following engine conditions: engine speed, load, and 

warm-up status of the first misfire event that resulted in the storage of the 

pending fault code. 

(3.4.5) Extinguishing the MIL. The MIL may be extinguished after three 

sequential driving cycles in which similar conditions have been 

encountered without an exceedance of the specified percentage of 

misfire. 

(4) EVAPORATIVE SYSTEM MONITORING

(4.1) Requirement: The OBD II system shall verify purge flow from the evaporative 

system and shall monitor the complete evaporative system, excluding the 

tubing and connections between the purge valve and the intake manifold, for 

vapor leaks to the atmosphere. Individual components of the evaporative 

system (e.g. valves, sensors, etc.) shall be monitored in accordance with the 

comprehensive components requirements in section (e)(15) (e.g., for circuit 

continuity, out of range values, rationality, proper functional response, etc.). 

Vehicles not required to be equipped with evaporative emission systems shall 

be exempt from monitoring of the evaporative system. 

(4.2) Malfunction Criteria: 

(4.2.1) For purposes of section (e)(4), an orifice shall be defined as an O’Keefe 

Controls Co. precision metal “Type B” orifice with NPT connections with a 

diameter of the specified dimension (e.g., part number B-20-SS for a 

stainless steel 0.020 inch diameter orifice). 

(4.2.2) The OBD II system shall detect an evaporative system malfunction when 

any of the following conditions exist: 

(A) No purge flow from the evaporative system to the engine can be detected 

by the OBD II system; 

(B) The complete evaporative system contains a leak or leaks that 

cumulatively are greater than or equal to a leak caused by a 0.040 inch 

diameter orifice; or 

(C) The complete evaporative system contains a leak or leaks that 

cumulatively are greater than or equal to a leak caused by a 0.020 inch 

diameter orifice. 

(4.2.3) On vehicles with fuel tank capacity greater than 25.0 gallons, a 

manufacturer may request the Executive Officer to revise the orifice size 

in sections (e)(4.2.2)(B) and/or (C) if the most reliable monitoring method 

available cannot reliably detect a system leak of the magnitudes specified. 

 The Executive Officer shall approve the request upon determining that 

the manufacturer has provided data and/or engineering analysis that 

demonstrate the need for the request. 

(4.2.4) Upon request by the manufacturer and upon determining that the 

manufacturer has submitted data and/or engineering evaluation which 

support the request, the Executive Officer shall revise the orifice size in 

sections (e)(4.2.2)(B) and/or (C) upward to exclude detection of leaks that 

cannot cause evaporative or running loss emissions to exceed 1.5 times 

the applicable standards. 

(4.2.5) A manufacturer may request Executive Officer approval to revise the 

orifice size in section (e)(4.2.2)(B) to a 0.090 inch diameter orifice. The 
35

Executive Officer shall approve the request upon the manufacturer 

submitting data and/or engineering analysis and the Executive Officer 

finding that: 

(A) the monitoring strategy for detecting orifices specified in section 

(e)(4.2.2)(C) meets the monitoring conditions requirements of section 

(e)(4.3.2); and 

(B) the monitoring strategy for detecting 0.090 inch diameter orifices yields an 

in-use monitor performance ratio (as defined in section (d)(4)) that meets 

or exceeds 0.620. 

(4.2.6) For the 2004 and 2005 model years only, manufacturers that use 

separate monitors to identify leaks (as specified in (e)(4.2.2.)(B) or (C)) in 

different portions of the complete evaporative system (e.g., separate 

monitors for the fuel tank to canister portion and for the canister to purge 

valve portion of the system) may request Executive Officer approval to 

revise the malfunction criteria in sections (e)(4.2.2)(B) and (C) to identify a 

malfunction when the separately monitored portion of the evaporative 

system (e.g., the fuel tank to canister portion) has a leak (or leaks) that is 

greater than or equal to the specified size in lieu of when the complete 

evaporative system has a leak (or leaks) that is greater than or equal to 

the specified size. The Executive Officer shall approve the request upon 

determining that the manufacturer utilized the same monitoring strategy 

(e.g., monitoring portions of the complete system with separate monitors) 

on vehicles prior to the 2004 model year and that the monitoring strategy 

provides further isolation of the malfunction for repair technicians by 

utilizing separate fault codes for each monitored portion of the evaporative 

system. 

(4.2.7) For vehicles that utilize more than one purge flow path (e.g., a turbocharged engine with a low pressure purge line and a high pressure purge 

line), the OBD II system shall verify the criteria of (e)(4.2.2)(A) (i.e., purge 

flow to the engine) for both purge flow paths. If a manufacturer 

demonstrates that blockage, leakage, or disconnection of one of the 

purge flow paths cannot cause a measurable emission increase during 

any reasonable in-use driving conditions, monitoring of that flow path is 

not required. 

(4.3) Monitoring Conditions: 

(4.3.1) Manufacturers shall define the monitoring conditions for malfunctions 

identified in sections (e)(4.2.2)(A) and (B) (i.e., purge flow and 0.040 inch 

leak detection) in accordance with sections (d)(3.1) and (d)(3.2) (i.e., 

minimum ratio requirements). 

(4.3.2) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (e)(4.2.2)(C) (i.e., 0.020 inch leak detection) in 

accordance with sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio 

requirements). For purposes of tracking and reporting as required in 

section (d)(3.2.2), all monitors used to detect malfunctions identified in 

section (e)(4.2.2)(C) shall be tracked separately but reported as a single 

set of values as specified in section (d)(5.2.2). 
36

(4.3.3) Manufacturers may disable or abort an evaporative system monitor when 

the fuel tank level is over 85 percent of nominal tank capacity or during a 

refueling event. 

(4.3.4) Manufacturers may request Executive Officer approval to execute the 

evaporative system monitor only on driving cycles determined by the 

manufacturer to be cold starts if the condition is needed to ensure reliable 

monitoring. The Executive Officer may not approve criteria that exclude 

engine starts from being considered as cold starts solely on the basis that 

ambient temperature exceeds (i.e., indicates a higher temperature than) 

engine coolant temperature at engine start. The Executive Officer shall 

approve the request upon determining that data and/or an engineering 

evaluation submitted by the manufacturer demonstrate that a reliable 

check can only be made on driving cycles when the cold start criteria are 

satisfied. 

(4.3.5) Manufacturers may temporarily disable the evaporative purge system to 

perform an evaporative system leak check. 

(4.4) MIL Illumination and Fault Code Storage: 

(4.4.1) Except as provided below for fuel cap leaks and alternate statistical MIL 

illumination protocols, general requirements for MIL illumination and fault 

code storage are set forth in section (d)(2). 

(4.4.2) If the OBD II system is capable of discerning that a system leak is being 

caused by a missing or improperly secured fuel cap:

(A) The manufacturer is not required to illuminate the MIL or store a fault 

code if the vehicle is equipped with an alternative indicator for notifying 

the vehicle operator of the malfunction. The alternative indicator shall be 

of sufficient illumination and location to be readily visible under all lighting 

conditions. 

(B) If the vehicle is not equipped with an alternative indicator and the MIL 

illuminates, the MIL may be extinguished and the corresponding fault 

codes erased once the OBD II system has verified that the fuel cap has 

been securely fastened and the MIL has not been illuminated for any 

other type of malfunction. 

(C) The Executive Officer may approve other strategies that provide 

equivalent assurance that a vehicle operator will be promptly notified of a 

missing or improperly secured fuel cap and that corrective action will be 

undertaken. 

(4.4.3) Notwithstanding section (d)(2.2.6), manufacturers may request Executive 

Officer approval to use alternative statistical MIL illumination and fault 

code storage protocols that require up to twelve driving cycles on average 

for monitoring strategies designed to detect malfunctions specified by 

section (e)(4.2.2)(C). Executive Officer approval shall be granted in 

accordance with the bases identified in section (d)(2.2.6) and upon 

determination that the manufacturer has submitted data and/or an 

engineering analysis demonstrating that the most reliable monitoring 

method available cannot reliably detect a malfunction of the specified size 

without the additional driving cycles and that the monitoring system will 

still meet the monitoring conditions requirements specified in sections 

(d)(3.1) and (3.2). 
37

(5) SECONDARY AIR SYSTEM MONITORING

(5.1) Requirement: The OBD II system on vehicles equipped with any form of 

secondary air delivery system shall monitor the proper functioning of the 

secondary air delivery system including all air switching valve(s). The 

individual electronic components (e.g., actuators, valves, sensors, etc.) in the 

secondary air system shall be monitored in accordance with the 

comprehensive component requirements in section (e)(15). 

(5.2) Malfunction Criteria: 

(5.2.1) For purposes of section (e)(5), “air flow” is defined as the air flow delivered 

by the secondary air system to the exhaust system. For vehicles using 

secondary air systems with multiple air flow paths/distribution points, the 

air flow to each bank (i.e., a group of cylinders that share a common 

exhaust manifold, catalyst, and control sensor) shall be monitored in 

accordance with the malfunction criteria in sections (e)(5.2.3) and (5.2.4) 

unless complete blocking of air delivery to one bank does not cause a 

measurable increase in emissions. 

(5.2.2) For all Low Emission Vehicle I applications: 

(A) Except as provided in sections (e)(5.2.2)(B) and (e)(5.2.4), the OBD II 

system shall detect a secondary air system malfunction prior to a 

decrease from the manufacturer's specified air flow that would cause a 

vehicle's emissions to exceed 1.5 times any of the applicable FTP 

standards. 

(B) Manufacturers may request Executive Officer approval to detect a 

malfunction when no detectable amount of air flow is delivered in lieu of 

the malfunction criteria in section (e)(5.2.2)(A). The Executive Office shall 

grant approval upon determining that deterioration of the secondary air 

system is unlikely based on data and/or engineering evaluation submitted 

by the manufacturer demonstrating that the materials used for the 

secondary air system (e.g., air hoses, tubing, valves, connectors, etc.) are 

inherently resistant to disconnection, corrosion, or other deterioration. 

(5.2.3) For all Low Emission Vehicle II applications and all 2009 and subsequent 

model year vehicles: 

(A) For 2004 and 2005 model year vehicles, manufacturers shall use the 

malfunction criteria specified for Low Emission Vehicle I applications in 

section (e)(5.2.2). 

(B) For 2006 and subsequent model year vehicles, except as provided in 

sections (e)(5.2.3)(C) and (e)(5.2.4), the OBD II system shall detect a 

secondary air system malfunction prior to a decrease from the 

manufacturer's specified air flow during normal operation that would 

cause a vehicle's emissions to exceed 1.5 times any of the applicable 

FTP standards. For purposes of sections (e)(5.2) and (5.3), “normal 

operation” shall be defined as the condition when the secondary air 

system is activated during catalyst and/or engine warm-up following 

engine start and may not include the condition when the secondary air 

system is intrusively turned on solely for the purpose of monitoring. 

(C) For 2006 and 2007 model year vehicles only, a manufacturer may 

request Executive Officer approval to detect a malfunction when no 
38

detectable amount of air flow is delivered during normal operation in lieu 

of the malfunction criteria in section (e)(5.2.3)(B) (e.g., 1.5 times the 

standard) during normal operation. Executive Officer approval shall be 

granted upon determining that the manufacturer has submitted data 

and/or engineering analysis that demonstrate that the monitoring system 

is capable of detecting malfunctions prior to a decrease from the 

manufacturer's specified air flow that would cause a vehicle's emissions to 

exceed 1.5 times any of the applicable FTP standards during an intrusive 

operation of the secondary air system later in the same driving cycle. 

(5.2.4) For vehicles in which no deterioration or failure of the secondary air 

system would result in a vehicle’s emissions exceeding 1.5 times any of 

the applicable standards, the OBD II system shall detect a malfunction 

when no detectable amount of air flow is delivered. For vehicles subject 

to the malfunction criteria in section (e)(5.2.3)(B), this monitoring for no 

detectable amount of air flow shall occur during normal operation of the 

secondary air system. 

(5.3) Monitoring Conditions: 

(5.3.1) For all Low Emission Vehicle I applications: Manufacturers shall define the 

monitoring conditions in accordance with section (d)(3.1). 

(5.3.2) For all Low Emission Vehicle II applications and all 2009 and subsequent 

model year vehicles: 

(A) For 2004 and 2005 model year vehicles, manufacturers shall define the 

monitoring conditions in accordance with section (d)(3.1). 

(B) For 2006 and subsequent model year vehicles, manufacturers shall 

define the monitoring conditions in accordance with sections (d)(3.1) and 

(d)(3.2) (i.e., minimum ratio requirements). For purposes of tracking and 

reporting as required in section (d)(3.2.2), all monitors used to detect 

malfunctions identified in section (e)(5.2) during normal operation of the 

secondary air system shall be tracked separately but reported as a single 

set of values as specified in section (d)(5.2.2). 

(5.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(6) FUEL SYSTEM MONITORING

(6.1) Requirement: 

(6.1.1) The OBD II system shall monitor the fuel delivery system to determine its 

ability to provide compliance with emission standards. 

(6.2) Malfunction Criteria: 

(6.2.1) The OBD II system shall detect a malfunction of the fuel delivery system 

when: 

(A) The fuel delivery system is unable to maintain a vehicle's emissions at or 

below 1.5 times any of the applicable FTP standards; or 

(B) If equipped, the feedback control based on a secondary oxygen or 

exhaust gas sensor is unable to maintain a vehicle’s emissions (except as 

a result of a malfunction specified in section (e)(6.2.1)(C)) at or below 1.5 

times any of the applicable FTP standards; or 

(C) Except as required in section (e)(6.2.6), for 25 percent of all 2011 model 

year vehicles, 50 percent of all 2012 model year vehicles, 75 percent of all 
39

2013 model year vehicles, and 100 percent of all 2014 model year 

vehicles, an air-fuel ratio cylinder imbalance (e.g., the air-fuel ratio in one 

or more cylinders is different than the other cylinders due to a cylinder 

specific malfunction such as an intake manifold leak at a particular 

cylinder, fuel injector problem, an individual cylinder EGR runner flow 

delivery problem, an individual variable cam lift malfunction such that an 

individual cylinder is operating on the wrong cam lift profile, or other 

similar problems) occurs in one or more cylinders such that the fuel 

delivery system is unable to maintain a vehicle’s emissions at or below: 

4.0 times the applicable FTP standards for PC/LDT SULEV II vehicles and 

3.0 times the applicable FTP standards for all other vehicles for the 2011 

through 2013 model years; and 1.5 times the applicable FTP standards 

for all 2014 and subsequent model year vehicles. In lieu of using 1.5 

times the applicable FTP standards for all 2014 model year applications, 

for the 2014 model year only, a manufacturer may continue to use 4.0 

times the applicable FTP standards for PC/LDT SULEV II vehicles and 3.0 

times the applicable FTP standards for other applications previously 

certified in the 2011, 2012, or 2013 model year to 4.0 times or 3.0 times 

the applicable FTP standards and carried over to the 2014 model year. 

(6.2.2) Except as provided for in section (e)(6.2.3) below, if the vehicle is 

equipped with adaptive feedback control, the OBD II system shall detect a 

malfunction when the adaptive feedback control has used up all of the 

adjustment allowed by the manufacturer. 

(6.2.3) If the vehicle is equipped with feedback control that is based on a 

secondary oxygen (or equivalent) sensor, the OBD II system is not 

required to detect a malfunction of the fuel system solely when the 

feedback control based on a secondary oxygen sensor has used up all of 

the adjustment allowed by the manufacturer. However, if a failure or 

deterioration results in vehicle emissions that exceed the malfunction 

criteria in section (e)(6.2.1), the OBD II system is required to detect a 

malfunction. 

(6.2.4) The OBD II system shall detect a malfunction whenever the fuel control 

system fails to enter closed-loop operation (if employed) within a 

manufacturer specified time interval. 

(6.2.5) Manufacturers may adjust the criteria and/or limit(s) to compensate for 

changes in altitude, for temporary introduction of large amounts of purge 

vapor, or for other similar identifiable operating conditions when they 

occur. 

(6.2.6) Notwithstanding the phase-in specified in section (e)(6.2.1)(C), if a vehicle 

is equipped with separate EGR flow delivery passageways (internal or 

external) that deliver EGR flow to individual cylinders (e.g., an EGR 

system with individual delivery pipes to each cylinder), the OBD II system 

shall monitor the fuel delivery system for malfunctions specified in section 

(e)(6.2.1)(C) on all 2011 and subsequent model year vehicles so 

equipped. 

(6.3) Monitoring Conditions: 

(6.3.1) Except as provided in section (e)(6.3.2), the fuel system shall be 

monitored continuously for the presence of a malfunction. 
40

(6.3.2) Manufacturers shall define monitoring conditions for malfunctions 

identified in section (e)(6.2.1)(C) (i.e., air-fuel ratio cylinder imbalance 

malfunctions) in accordance with sections (d)(3.1) and (d)(3.2) (i.e., 

minimum ratio requirements). 

(6.4) MIL Illumination and Fault Code Storage: For malfunctions described under 

section (6.2.1)(C) (i.e., air-fuel ratio cylinder imbalance malfunctions), general 

requirements for MIL illumination and fault code storage are set forth in 

section (d)(2). For all other fuel system malfunctions, the MIL illumination 

and fault code storage requirements are set forth in sections (e)(6.4.1) 

through (6.4.6) below. 

(6.4.1) A pending fault code shall be stored immediately upon the fuel system 

exceeding the malfunction criteria established pursuant to section (e)(6.2). 

(6.4.2) Except as provided below, if a pending fault code is stored, the OBD II 

system shall immediately illuminate the MIL and store a confirmed fault 

code if a malfunction is again detected during either of the following two 

events: (a) the driving cycle immediately following the storage of the 

pending fault code, regardless of the conditions encountered during the 

driving cycle; or (b) on the next driving cycle in which similar conditions 

(see section (c)) to those that occurred when the pending fault code was 

stored are encountered. 

(6.4.3) The pending fault code may be erased at the end of the next driving cycle 

in which similar conditions have been encountered without an exceedance 

of the specified fuel system malfunction criteria. The pending code may 

also be erased if similar conditions are not encountered during the 80 

driving cycles immediately after the initial detection of a malfunction for 

which the pending code was set. 

(6.4.4) Storage of freeze frame conditions. 

(A) The OBD II system shall store and erase freeze frame conditions either in 

conjunction with storing and erasing a pending fault code or in conjunction 

with storing and erasing a confirmed fault code. 

(B) If freeze frame conditions are stored for a malfunction other than misfire 

(see section (e)(3)) or fuel system malfunction when a fault code is stored 

as specified in section (e)(6.4) above, the stored freeze frame information 

shall be replaced with freeze frame information regarding the fuel system 

malfunction. 

(6.4.5) Storage of fuel system conditions for determining similar conditions of 

operation. 

(A) Upon detection of a fuel system malfunction under section (e)(6.2), the 

OBD II system shall store the engine speed, load, and warm-up status of 

the first fuel system malfunction that resulted in the storage of the pending 

fault code. 

(B) For fuel system faults detected using feedback control that is based on a 

secondary oxygen (or equivalent) sensor, the manufacturer may request 

Executive Officer approval to use an alternate definition of similar 

conditions in lieu of the definition specified in section (c). The Executive 

Officer shall approve the alternate definition upon the manufacturer 

providing data or analysis demonstrating that the alternate definition 
41

provides for equivalent robustness in detection of fuel system faults that 

vary in severity depending on engine speed, load, and/or warm-up status. 

(6.4.6) Extinguishing the MIL. The MIL may be extinguished after three 

sequential driving cycles in which similar conditions have been 

encountered without a malfunction of the fuel system. 

(7) EXHAUST GAS SENSOR MONITORING

(7.1) Requirement: 

(7.1.1) The OBD II system shall monitor the output voltage, response rate, and 

any other parameter which can affect emissions of all primary (fuel 

control) oxygen sensors (conventional switching sensors and wide range 

or universal sensors) for malfunction. 

(7.1.2) The OBD II system shall also monitor all secondary oxygen sensors 

(those used for fuel trim control or as a monitoring device) for proper 

output voltage, activity, and/or response rate. 

(7.1.3) For vehicles equipped with heated oxygen sensors, the OBD II system 

shall monitor the heater for proper performance. 

(7.1.4) For other types of sensors (e.g., hydrocarbon sensors, NOx sensors), the 

manufacturer shall submit a monitoring plan to the Executive Officer for 

approval. The Executive Officer shall approve the request upon 

determining that the manufacturer has submitted data and an engineering 

evaluation that demonstrate that the monitoring plan is as reliable and 

effective as the monitoring plan required for conventional sensors under 

section (e)(7). 

(7.2) Malfunction Criteria: 

(7.2.1) Primary Sensors: 

(A) The OBD II system shall detect a malfunction prior to any failure or 

deterioration of the oxygen sensor voltage, response rate, amplitude, or 

other characteristic(s) (including drift or bias corrected for by secondary 

sensors) that would cause a vehicle's emissions to exceed 1.5 times any 

of the applicable FTP standards. For response rate (see section (c)), the 

OBD II system shall detect asymmetric malfunctions (i.e., malfunctions 

that primarily affect only the lean-to-rich response rate or only the 

rich-to-lean response rate) and symmetric malfunctions (i.e., malfunctions 

that affect both the lean-to-rich and rich-to-lean response rates). As 

defined in section (c), response rate includes delays in the sensor to 

initially react to a change in exhaust gas composition as well as delays 

during the transition from a rich-to-lean (or lean-to-rich) sensor output. 

For 25 percent of 20102011, 50 percent of 20112012, and 100 percent of 

2012 2013 and subsequent model year vehicles, the manufacturer shall 

submit data and/or engineering analysis to demonstrate that the 

calibration method used ensures proper detection of all symmetric and 

asymmetric response rate malfunctions as part of the certification 

application. 

(B) The OBD II system shall detect malfunctions of the oxygen sensor caused 

by either a lack of circuit continuity or out-of-range values. 

(C) The OBD II system shall detect a malfunction of the oxygen sensor when 

a sensor failure or deterioration causes the fuel system to stop using that 
42

sensor as a feedback input (e.g., causes default or open loop operation) 

or causes the fuel system to fail to enter closed-loop operation within a 

manufacturer-specified time interval. 

(D) The OBD II system shall detect a malfunction of the oxygen sensor when 

the sensor output voltage, amplitude, activity, or other characteristics are 

no longer sufficient for use as an OBD II system monitoring device (e.g., 

for catalyst monitoring). 

(7.2.2) Secondary Sensors: 

(A) The OBD II system shall detect a malfunction prior to any failure or 

deterioration of the oxygen sensor voltage, response rate, amplitude, or 

other characteristic(s) that would cause a vehicle's emissions to exceed 

1.5 times any of the applicable FTP standards. 

(B) The OBD II system shall detect malfunctions of the oxygen sensor caused 

by a lack of circuit continuity. 

(C) Sufficient sensor performance for other monitors. 

(i) The OBD II system shall detect a malfunction of the oxygen sensor 

when the sensor output voltage, amplitude, activity, or other 

characteristics are no longer sufficient for use as an OBD II system 

monitoring device (e.g., for catalyst monitoring). For this requirement, 

“sufficient” is defined as the capability of the worst performing 

acceptable sensor to detect the best performing unacceptable other 

monitored system or component (e.g., catalyst). 

(ii) For systems where it is not technically feasible to satisfy the criteria of 

section (e)(7.2.2)(C)(i) completely, the OBD II system shall, at a 

minimum, detect a slow rich-to-lean response malfunction during a fuel 

shut-off event (e.g., deceleration fuel cut event). The rich-to-lean 

response check shall monitor both the sensor response time from a 

rich condition (e.g., 0.7 Volts) prior to the start of fuel shut-off to a lean 

condition (e.g., 0.1 Volts) expected during fuel shut-off conditions and 

the sensor transition time in the intermediate sensor range (e.g., from 

0.55 Volts to 0.3 Volts). Monitoring of the rich-to-lean response shall 

be phased in on at least 25 percent of the 2009, 50 percent of the 

2010, and 100 percent of the 2011 model year vehicles. For purposes 

of this phase-in, vehicles meeting the criteria of section (e)(7.2.2)(C)(i) 

shall be counted as vehicles meeting the rich-to-lean response rate 

monitoring requirement of section (e)(7.2.2)(C)(ii). 

(iii) Additionally, for systems where it is not technically feasible to satisfy 

the criteria in section (e)(7.2.2)(C)(i), prior to certification of 2009 

model year vehicles, the manufacturer must submit a comprehensive 

plan to the Executive Officer demonstrating the manufacturer’s efforts 

to minimize any gap remaining between the worst performing 

acceptable sensor and a sufficient sensor. The plan should include 

quantification of the gap and supporting documentation for efforts to 

close the gap including sensor monitoring improvements, other system 

component monitor improvements (e.g., changes to make the catalyst 

monitor less sensitive to oxygen sensor response), and sensor 

specification changes, if any. The Executive Officer shall approve the 

plan upon determining the submitted information supports the 
43

necessity of the gap and the plan demonstrates that the manufacturer 

is taking reasonable efforts to minimize or eliminate the gap in a timely 

manner. 

(D) The OBD II system shall detect malfunctions of the oxygen sensor 

caused by out-of-range values. 

(7.2.3) Sensor Heaters: 

(A) The OBD II system shall detect a malfunction of the heater performance 

when the current or voltage drop in the heater circuit is no longer within 

the manufacturer's specified limits for normal operation (i.e., within the 

criteria required to be met by the component vendor for heater circuit 

performance at high mileage). Subject to Executive Officer approval, 

other malfunction criteria for heater performance malfunctions may be 

used upon the Executive Officer determining that the manufacturer has 

submitted data and/or an engineering evaluation that demonstrate the 

monitoring reliability and timeliness to be equivalent to the stated criteria 

in section (e)(7.2.3)(A). 

(B) The OBD II system shall detect malfunctions of the heater circuit including 

open or short circuits that conflict with the commanded state of the heater 

(e.g., shorted to 12 Volts when commanded to 0 Volts (ground), etc.). 

(7.3) Monitoring Conditions: 

(7.3.1) Primary Sensors 

(A) Manufacturers shall define the monitoring conditions for malfunctions 

identified in sections (e)(7.2.1)(A) and (D) (e.g., proper response rate) in 

accordance with sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio 

requirements). For purposes of tracking and reporting as required in 

section (d)(3.2.2), all monitors used to detect malfunctions identified in 

sections (e)(7.2.1)(A) and (D) shall be tracked separately but reported as 

a single set of values as specified in section (d)(5.2.2). 

(B) Except as provided in section (e)(7.3.1)(C), monitoring for malfunctions 

identified in sections (e)(7.2.1)(B) and (C) (i.e., circuit continuity, out-ofrange, and open-loop malfunctions) shall be: 

(i) Conducted in accordance with title 13, CCR section 1968.1 for Low 

Emission Vehicle I applications and 2004 and 2005 model year Low 

Emission Vehicle II applications; 

(ii) Conducted continuously for all 2006 through 2008 model year Low 

Emission Vehicle II applications and all 2009 and subsequent model 

year vehicles. 

(C) A manufacturer may request Executive Officer approval to disable 

continuous oxygen sensor monitoring when an oxygen sensor malfunction 

cannot be distinguished from other effects (e.g., disable out-of-range low 

monitoring during fuel cut conditions). The Executive Officer shall 

approve the disablement upon determining that the manufacturer has 

submitted test data and/or documentation that demonstrate a properly 

functioning sensor cannot be distinguished from a malfunctioning sensor 

and that the disablement interval is limited only to that necessary for 

avoiding false detection. 

(7.3.2) Secondary Sensors 

(A) Manufacturers shall define monitoring conditions for malfunctions 
44

identified in sections (e)(7.2.2)(A) and (C) (e.g., proper sensor activity) in 

accordance with sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio 

requirements). For all 2010 and subsequent model year vehicles meeting 

the monitoring requirements of section (e)(7.2.2)(C)(i) or (ii), for purposes 

of tracking and reporting as required in section (d)(3.2.2), all monitors 

used to detect malfunctions identified in sections (e)(7.2.2)(A) and (C) 

shall be tracked separately but reported as a single set of values as 

specified in section (d)(5.2.2). 

(B) Except as provided in section (e)(7.3.2)(C), monitoring for malfunctions 

identified in sections (e)(7.2.2)(B) and (D) (i.e., open circuit, out-of-range 

malfunctions) shall be: 

(i) Conducted in accordance with title 13, CCR section 1968.1 for Low 

Emission Vehicle I applications and 2004 and 2005 model year Low 

Emission Vehicle II applications; 

(ii) Conducted continuously for all 2006 through 2008 model year Low 

Emission Vehicle II applications and all 2009 and subsequent model 

year vehicles. 

(C) A manufacturer may request Executive Officer approval to disable 

continuous oxygen sensor monitoring when an oxygen sensor malfunction 

cannot be distinguished from other effects (e.g., disable out-of-range low 

monitoring during fuel cut conditions). The Executive Officer shall 

approve the disablement upon determining that the manufacturer has 

submitted test data and/or documentation that demonstrate a properly 

functioning sensor cannot be distinguished from a malfunctioning sensor 

and that the disablement interval is limited only to that necessary for 

avoiding false detection. 

(7.3.3) Sensor Heaters 

(A) Manufacturers shall define monitoring conditions for malfunctions 

identified in section (e) (7.2.3)(A) (e.g., sensor heater performance) in 

accordance with sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio 

requirements). 

(B) Monitoring for malfunctions identified in section (e)(7.2.3)(B) (e.g., circuit 

malfunctions) shall be: 

(i) Conducted in accordance with title 13, CCR section 1968.1 for 2004 

and 2005 model year vehicles; 

(ii) Conducted continuously for all 2006 and subsequent model year 

vehicles. 

(7.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(8) EXHAUST GAS RECIRCULATION (EGR) SYSTEM MONITORING

(8.1) Requirement: The OBD II system shall monitor the EGR system on vehicles 

so-equipped for low and high flow rate malfunctions. The individual electronic 

components (e.g., actuators, valves, sensors, etc.) that are used in the EGR 

system shall be monitored in accordance with the comprehensive component 

requirements in section (e)(15). 

(8.2) Malfunction Criteria: 
45

(8.2.1) The OBD II system shall detect a malfunction of the EGR system prior to 

an increase or decrease from the manufacturer's specified EGR flow rate 

that would cause a vehicle's emissions to exceed 1.5 times any of the 

applicable FTP standards. 

(8.2.2) For vehicles in which no failure or deterioration of the EGR system could 

result in a vehicle’s emissions exceeding 1.5 times any of the applicable 

standards, the OBD II system shall detect a malfunction when the system 

has no detectable amount of EGR flow. 

(8.3) Monitoring Conditions: 

(8.3.1) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (e)(8.2) (e.g., flow rate) in accordance with sections 

(d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). For purposes of 

tracking and reporting as required in section (d)(3.2.2), all monitors used 

to detect malfunctions identified in section (e)(8.2) shall be tracked 

separately but reported as a single set of values as specified in section 

(d)(5.2.2). 

(8.3.2) Manufacturers may request Executive Officer approval to temporarily 

disable the EGR system check under specific conditions (e.g., when 

freezing may affect performance of the system). The Executive Officer 

shall approve the request upon determining that the manufacturer has 

submitted data and/or an engineering evaluation which demonstrate that a 

reliable check cannot be made when these conditions exist. 

(8.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(9) POSITIVE CRANKCASE VENTILATION (PCV) SYSTEM MONITORING

(9.1) Requirement: 

(9.1.1) On all 2004 and subsequent model year vehicles, manufacturers shall 

monitor the PCV system on vehicles so-equipped for system integrity. A 

manufacturer may use an alternate phase-in schedule in lieu of meeting 

the requirements of section (e)(9) on all 2004 model year vehicles if the 

alternate phase-in schedule provides for equivalent compliance volume 

(as defined in section (c)) to the phase-in schedule specified in title 13, 

CCR section 1968.1(b)(10.1). Vehicles not required to be equipped with 

PCV systems shall be exempt from monitoring of the PCV system. 

(9.2) Malfunction Criteria: 

(9.2.1) For the purposes of section (e)(9), “PCV system” is defined as any form of 

crankcase ventilation system, regardless of whether it utilizes positive 

pressure. “PCV valve” is defined as any form of valve or orifice used to 

restrict or control crankcase vapor flow. Further, any additional external 

PCV system tubing or hoses used to equalize crankcase pressure or to 

provide a ventilation path between various areas of the engine (e.g., 

crankcase and valve cover) are considered part of the PCV system 

“between the crankcase and the PCV valve” and subject to the 

malfunction criteria in section (e)(9.2.2) below. 
46

(9.2.2) Except as provided below, the OBD II system shall detect a malfunction of 

the PCV system when a disconnection of the system occurs between 

either the crankcase and the PCV valve, or between the PCV valve and 

the intake manifold. 

(9.2.3) If the PCV system is designed such that the PCV valve is fastened directly 

to the crankcase in a manner which makes it significantly more difficult to 

remove the valve from the crankcase rather than disconnect the line 

between the valve and the intake manifold (taking aging effects into 

consideration), the Executive Officer shall exempt the manufacturer from 

detection of disconnection between the crankcase and the PCV valve. 

(9.2.4) Subject to Executive Officer approval, system designs that utilize tubing 

between the valve and the crankcase shall also be exempted from the 

portion of the monitoring requirement for detection of disconnection 

between the crankcase and the PCV valve. The manufacturer shall file a 

request and submit data and/or engineering evaluation in support of the 

request. The Executive Officer shall approve the request upon 

determining that the connections between the valve and the crankcase 

are: (i) resistant to deterioration or accidental disconnection, (ii) 

significantly more difficult to disconnect than the line between the valve 

and the intake manifold, and (iii) not subject to disconnection per 

manufacturer’s repair procedures for non-PCV system repair work. 

(9.2.5) Manufacturers are not required to detect disconnections between the PCV 

valve and the intake manifold if said disconnection (1) causes the vehicle 

to stall immediately during idle operation; or (2) is unlikely to occur due to 

a PCV system design that is integral to the induction system (e.g., 

machined passages rather than tubing or hoses). 

(9.3) Monitoring Conditions: Manufacturers shall define the monitoring conditions 

for malfunctions identified in section (e)(9.2) in accordance with sections 

(d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). 

(9.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). The stored 

fault code need not specifically identify the PCV system (e.g., a fault code for 

idle speed control or fuel system monitoring can be stored) if the 

manufacturer demonstrates that additional monitoring hardware would be 

necessary to make this identification, and provided the manufacturer’s 

diagnostic and repair procedures for the detected malfunction include 

directions to check the integrity of the PCV system. 

(10) ENGINE COOLING SYSTEM MONITORING

(10.1) Requirement: 

(10.1.1) The OBD II system shall monitor the thermostat on vehicles so-equipped 

for proper operation. 

(10.1.2) The OBD II system shall monitor the engine coolant temperature (ECT) 

sensor for circuit continuity, out-of-range values, and rationality faults. 

(10.2) Malfunction Criteria: 

(10.2.1) Thermostat 
47

(A) The OBD II system shall detect a thermostat malfunction if, within an 

Executive Officer approved time interval after starting the engine, either of 

the following two conditions occur: 

(i) The coolant temperature does not reach the highest temperature 

required by the OBD II system to enable other diagnostics; 

(ii) The coolant temperature does not reach a warmed-up temperature 

within 20 degrees Fahrenheit of the manufacturer’s nominal thermostat 

regulating temperature. Subject to Executive Officer approval, a 

manufacturer may utilize lower temperatures for this criterion upon the 

Executive Officer determining that the manufacturer has demonstrated 

that the fuel, spark timing, and/or other coolant temperature-based 

modifications to the engine control strategies would not cause an 

emission increase of 50 or more percent of any of the applicable 

standards (e.g., 50 degree Fahrenheit emission test, etc.). 

(B) Executive Officer approval of the time interval after engine start shall be 

granted upon determining that the data and/or engineering evaluation 

submitted by the manufacturer supports the specified times. 

(C) With Executive Officer approval, a manufacturer may use alternate 

malfunction criteria and/or monitoring conditions (see section (e)(10.3)) 

that are a function of temperature at engine start on vehicles that do not 

reach the temperatures specified in the malfunction criteria when the 

thermostat is functioning properly. Executive Officer approval shall be 

granted upon determining that the manufacturer has submitted data that 

demonstrate that a properly operating system does not reach the 

specified temperatures, that the monitor is capable of meeting the 

specified malfunction criteria at engine start temperatures greater than 

50°F, and that the overall effectiveness of the monitor is comparable to a 

monitor meeting these thermostat monitoring requirements at lower 

temperatures. 

(D) With Executive Officer approval, manufacturers may omit this monitor. 

Executive Officer approval shall be granted upon determining that the 

manufacturer has demonstrated that a malfunctioning thermostat cannot 

cause a measurable increase in emissions during any reasonable driving 

condition nor cause any disablement of other monitors. 

(10.2.2) ECT Sensor 

(A) Circuit Continuity. The OBD II system shall detect a malfunction when a 

lack of circuit continuity or out-of-range value occurs. 

(B) Time to Reach Closed-Loop Enable Temperature. 

(i) The OBD II system shall detect a malfunction if the ECT sensor does 

not achieve the stabilized minimum temperature which is needed for 

the fuel control system to begin closed-loop operation (closed-loop 

enable temperature) within an Executive Officer approved time interval 

after starting the engine. 

(ii) The time interval shall be a function of starting ECT and/or a function 

of intake air temperature and, except as provided below in section 

(e)(10.2.2)(B)(iii), may not exceed: 

a. two minutes for engine start temperatures at or above 50 degrees 

Fahrenheit and five minutes for engine start temperatures at or 
48

above 20 degrees Fahrenheit and below 50 degrees Fahrenheit for 

Low Emission Vehicle I applications and 2004 and 2005 model 

year Low Emission Vehicle II applications; 

b. two minutes for engine start temperatures up to 15 degrees 

Fahrenheit below the closed-loop enable temperature and five 

minutes for engine start temperatures between 15 and 35 degrees 

Fahrenheit below the closed-loop enable temperature for all 2006 

through 2008 model year Low Emission Vehicle II applications and 

all 2009 and subsequent model year vehicles. 

(iii) Executive Officer approval of the time interval shall be granted upon 

determining that the data and/or engineering evaluation submitted by 

the manufacturer supports the specified times. The Executive Officer 

shall allow longer time intervals upon determining that the 

manufacturer has submitted data and/or an engineering evaluation 

that demonstrate that the vehicle requires a longer time to warm up 

under normal conditions. 

(iv) The Executive Officer shall exempt manufacturers from the 

requirement of section (e)(10.2.2)(B) if the manufacturer does not 

utilize ECT to enable closed loop fuel control. 

(C) Stuck in Range Below the Highest Minimum Enable Temperature. To the 

extent feasible when using all available information, the OBD II system 

shall detect a malfunction if the ECT sensor inappropriately indicates a 

temperature below the highest minimum enable temperature required by 

the OBD II system to enable other diagnostics (e.g., an OBD II system 

that requires ECT to be greater than 140 degrees Fahrenheit to enable a 

diagnostic must detect malfunctions that cause the ECT sensor to 

inappropriately indicate a temperature below 140 degrees Fahrenheit). 

Manufacturers are exempted from this requirement for temperature 

regions in which the monitors required under sections (e)(10.2.1) or 

(e)(10.2.2)(B) will detect ECT sensor malfunctions as defined in section 

(e)(10.2.2)(C). 

(D) Stuck in Range Above the Lowest Maximum Enable Temperature. 

(i) To the extent feasible when using all available information, the OBD II 

system shall detect a malfunction if the ECT sensor inappropriately 

indicates a temperature above the lowest maximum enable 

temperature required by the OBD II system to enable other diagnostics 

(e.g., an OBD II system that requires ECT to be less than 90 degrees 

Fahrenheit at engine start to enable a diagnostic must detect 

malfunctions that cause the ECT sensor to inappropriately indicate a 

temperature above 90 degrees Fahrenheit). 

(ii) Manufacturers are exempted from this requirement for temperature 

regions in which the monitors required under sections (e)(10.2.1), 

(e)(10.2.2)(B), or (e)(10.2.2)(C) (i.e., ECT sensor or thermostat 

malfunctions) will detect ECT sensor malfunctions as defined in 

section (e)(10.2.2)(D) or in which the MIL will be illuminated under the 

requirements of section (d)(2.2.3) for default mode operation (e.g., 

overtemperature protection strategies). 
49

(iii) For Low Emission Vehicle I applications and 2004 and 2005 model 

year Low Emission Vehicle II applications only, manufacturers are also 

exempted from the requirements of section (e)(10.2.2)(D) for vehicles 

that have a temperature gauge (not a warning light) on the instrument 

panel and utilize the same ECT sensor for input to the OBD II system 

and the temperature gauge. 

(iv) For 2006 through 2008 model year Low Emission Vehicle II 

applications and all 2009 and subsequent model year vehicles, 

manufacturers are also exempted from the requirements of section 

(e)(10.2.2)(D) for temperature regions where the temperature gauge 

indicates a temperature in the red zone (engine overheating zone) for 

vehicles that have a temperature gauge (not a warning light) on the 

instrument panel and utilize the same ECT sensor for input to the 

OBD II system and the temperature gauge. 

(10.3) Monitoring Conditions: 

(10.3.1) Thermostat 

(A) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (e)(10.2.1)(A) in accordance with section (d)(3.1) 

except as provided for in section (e)(10.3.1)(D). Additionally, except as 

provided for in sections (e)(10.3.1)(B) and (C), monitoring for malfunctions 

identified in section (e)(10.2.1)(A) shall be conducted once per driving 

cycle on every driving cycle in which the ECT sensor indicates, at engine 

start, a temperature lower than the temperature established as the 

malfunction criteria in section (e)(10.2.1)(A). 

(B) Manufacturers may disable thermostat monitoring at ambient 

temperatures below 20 degrees Fahrenheit. 

(C) Manufacturers may request Executive Officer approval to suspend or 

disable thermostat monitoring if the vehicle is subjected to conditions 

which could lead to false diagnosis (e.g., vehicle operation at idle for more 

than 50 percent of the warm-up time, hot restart conditions, etc.). In 

general, the Executive Officer shall not approve disablement of the 

monitor on engine starts where the ECT at engine start is more than 35 

degrees Fahrenheit lower than the thermostat malfunction threshold 

temperature determined under section (e)(10.2.1)(A). The Executive 

Officer shall approve the request upon determining that the manufacturer 

has provided data and/or engineering analysis that demonstrate the need 

for the request. 

(D) With respect to defining enable conditions that are encountered during 

the FTP or Unified cycle as required in (d)(3.1.1) for malfunctions 

identified in section (e)(10.2.1)(A), the FTP cycle or Unified cycle shall 

refer to on-road driving following the FTP or Unified cycle in lieu of testing 

on a chassis dynamometer. 

(10.3.2) ECT Sensor 

(A) Except as provided below in section (e)(10.3.2)(E), monitoring for 

malfunctions identified in section (e)(10.2.2)(A) (i.e., circuit continuity and 

out-of-range) shall be conducted continuously. 

(B) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (e)(10.2.2)(B) in accordance with section (d)(3.1). 
50

Additionally, except as provided for in section (e)(10.3.2)(D), monitoring 

for malfunctions identified in section (e)(10.2.2)(B) shall be conducted 

once per driving cycle on every driving cycle in which the ECT sensor 

indicates a temperature lower than the closed loop enable temperature at 

engine start (i.e., all engine start temperatures greater than the ECT 

sensor out of range low temperature and less than the closed loop enable 

temperature). 

(C) Manufacturers shall define the monitoring conditions for malfunctions 

identified in sections (e)(10.2.2)(C) and (D) in accordance with sections 

(d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). 

(D) Manufacturers may suspend or delay the time to reach closed loop 

enable temperature diagnostic if the vehicle is subjected to conditions 

which could lead to false diagnosis (e.g., vehicle operation at idle for more 

than 50 to 75 percent of the warm-up time). 

(E) A manufacturer may request Executive Officer approval to disable 

continuous ECT sensor monitoring when an ECT sensor malfunction 

cannot be distinguished from other effects. The Executive Officer shall 

approve the disablement upon determining that the manufacturer has 

submitted test data and/or engineering evaluation that demonstrate a 

properly functioning sensor cannot be distinguished from a malfunctioning 

sensor and that the disablement interval is limited only to that necessary 

for avoiding false detection. 

(10.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(11) COLD START EMISSION REDUCTION STRATEGY MONITORING

(11.1) Requirement: 

(11.1.1) For all 2006 through 2008 model year Low Emission Vehicle II 

applications and all 2009 and subsequent model year applications, if a 

vehicle incorporates a specific engine control strategy to reduce cold start 

emissions, the OBD II system shall monitor the commanded elements for 

proper function (e.g., increased engine idle speed, commanded ignition 

timing retard, etc.), other than secondary air, while the control strategy is 

active to ensure proper operation of the control strategy. Secondary air 

systems shall be monitored under the provisions of section (e)(5). 

(11.1.2) In lieu of meeting the requirements of section (e)(11) on all 2006 through 

2008 model year Low Emission Vehicle II applications, a manufacturer 

may phase in the requirements on a portion of its Low Emission Vehicle II 

applications as long as that portion of Low Emission Vehicle II 

applications comprises at least 30 percent of all 2006 model year 

vehicles, 60 percent of all 2007 model year vehicles, and 100 percent of 

all 2008 and subsequent model year vehicles. 

(11.2) Malfunction Criteria: 

(11.2.1) For vehicles not included in the phase-in specified in section (e)(11.2.2): 

(A) The OBD II system shall detect a malfunction prior to any failure or 

deterioration of the individual components associated with the cold start 

emission reduction control strategy that would cause a vehicle’s emissions 

to exceed 1.5 times the applicable FTP standards. Manufacturers shall: 
51

(i) Establish the malfunction criteria based on data from one or more 

representative vehicle(s). 

(ii) Provide an engineering evaluation for establishing the malfunction 

criteria for the remainder of the manufacturer’s product line. The 

Executive Officer shall waive the evaluation requirement each year if, 

in the judgment of the Executive Officer, technological changes do not 

affect the previously determined malfunction criteria. 

(B) For components where no failure or deterioration of the component used 

for the cold start emission reduction strategy could result in a vehicle’s 

emissions exceeding 1.5 times the applicable standards, the individual 

component shall be monitored for proper functional response in 

accordance with the malfunction criteria in section (e)(15.2) while the 

control strategy is active. 

(11.2.2) For 25 percent of 2010, 50 percent of 2011, and 100 percent of 2012 

and subsequent model year vehicles, the OBD II system shall, to the 

extent feasible, detect a malfunction if either of the following occurs: 

(A) Any single commanded element does not properly respond to the 

commanded action while the cold start strategy is active. For elements 

involving spark timing (e.g., retarded spark timing), the monitor may verify 

final commanded spark timing in lieu of verifying actual delivered spark 

timing. For purposes of this section, “properly respond” is defined as 

when the element responds: 

(i) by a robustly detectable amount; and 

(ii) in the direction of the desired command; and 

(iii) above and beyond what the element would achieve on start-up without 

the cold start strategy active (e.g., if the cold start strategy commands 

a higher idle engine speed, a fault must be detected if there is no 

detectable amount of engine speed increase above what the system 

would achieve without the cold start strategy active); 

(B) Any failure or deterioration of the cold start emission reduction control 

strategy that would cause a vehicle’s emissions to be equal to or above 

1.5 times the applicable FTP standards. For this requirement, the OBD II 

system shall either monitor elements of the system as a whole (e.g., 

measuring air flow and modeling overall heat into the exhaust) or the 

individual elements (e.g., increased engine speed, commanded final spark 

timing) for failures that cause vehicle emissions to exceed 1.5 times the 

applicable FTP standards. 

(11.3) Monitoring Conditions: Manufacturers shall define the monitoring conditions 

for malfunctions identified in section (e)(11.2) in accordance with sections 

(d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). 

(11.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(12) AIR CONDITIONING (A/C) SYSTEM COMPONENT MONITORING

(12.1) Requirement: If a vehicle incorporates an engine control strategy that alters 

off-idle fuel and/or spark control when the A/C system is on, the OBD II 

system shall monitor all electronic air conditioning system components for 

malfunctions that cause the system to fail to invoke the alternate control while 
52

the A/C system is on or cause the system to invoke the alternate control while 

the A/C system is off. Additionally, the OBD II system shall monitor for 

malfunction all electronic air conditioning system components that are used 

as part of the diagnostic strategy for any other monitored system or 

component. The requirements of section (e)(12) shall be phased in as 

follows: 30 percent of all 2006 model year vehicles, 60 percent of all 2007 

model year vehicles, and 100 percent of all 2008 and subsequent model year 

vehicles. 

(12.2) Malfunction Criteria: 

(12.2.1) The OBD II system shall detect a malfunction prior to any failure or 

deterioration of an electronic component of the air conditioning system 

that would cause a vehicle's emissions to exceed 1.5 times any of the 

appropriate applicable emission standards or would, through software, 

effectively disable any other monitored system or component covered by 

this regulation. For malfunctions that result in the alternate control being 

erroneously invoked while the A/C system is off, the appropriate emission 

standards shall be the FTP standards. For malfunctions that result in the 

alternate control failing to be invoked while the A/C system is on, the 

appropriate emission standards shall be the SC03 emission standards. 

(12.2.2) If no single electronic component failure or deterioration causes 

emissions to exceed 1.5 times any of the appropriate applicable emission 

standards as defined above in section (e)(12.2.1) nor is used as part of 

the diagnostic strategy for any other monitored system or component, 

manufacturers are not required to monitor any air conditioning system 

component for purposes of section (e)(12). 

(12.3) Monitoring Conditions: Manufacturers shall define the monitoring conditions 

for malfunctions identified in section (e)(12.2) in accordance with sections 

(d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). 

(12.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(13) VARIABLE VALVE TIMING AND/OR CONTROL (VVT) SYSTEM MONITORING

(13.1) Requirement: On all 2006 through 2008 model year Low Emission Vehicle II 

applications and all 2009 and subsequent model year vehicles, the OBD II 

system shall monitor the VVT system on vehicles so-equipped for target error 

and slow response malfunctions. The individual electronic components (e.g., 

actuators, valves, sensors, etc.) that are used in the VVT system shall be 

monitored in accordance with the comprehensive components requirements 

in section (e)(15). VVT systems on Low Emission Vehicle I applications and 

2004 and 2005 model year Low Emission Vehicle II applications shall be 

monitored in accordance with the comprehensive components requirements 

in section (e)(15). 

(13.2) Malfunction Criteria: 

(13.2.1) Target Error. The OBD II system shall detect a malfunction prior to any 

failure or deterioration in the capability of the VVT system to achieve the 

commanded valve timing and/or control within a crank angle and/or lift 

tolerance that would cause a vehicle's emissions to exceed 1.5 times any 

of the applicable FTP standards. 
53

(13.2.2) Slow Response. The OBD II system shall detect a malfunction prior to 

any failure or deterioration in the capability of the VVT system to achieve 

the commanded valve timing and/or control within a time that would cause 

a vehicle's emissions to exceed 1.5 times any of the applicable FTP 

standards. 

(13.2.3) For vehicles in which no failure or deterioration of the VVT system could 

result in a vehicle’s emissions exceeding 1.5 times any of the applicable 

standards, the VVT system shall be monitored for proper functional 

response in accordance with the malfunction criteria in section (e)(15.2). 

(13.3) Monitoring Conditions: Manufacturers shall define the monitoring conditions 

for VVT system malfunctions identified in section (e)(13.2) in accordance with 

sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements), with the 

exception that monitoring shall occur every time the monitoring conditions are 

met during the driving cycle in lieu of once per driving cycle as required in 

section (d)(3.1.2). Additionally, manufacturers shall track and report VVT 

system monitor performance under section (d)(3.2.2). For purposes of 

tracking and reporting as required in section (d)(3.2.2), all monitors used to 

detect malfunctions identified in section (e)(13.2) shall be tracked separately 

but reported as a single set of values as specified in section (d)(5.2.2). 

(13.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(14) DIRECT OZONE REDUCTION (DOR) SYSTEM MONITORING

(14.1) Requirement: 

(14.1.1) The OBD II system shall monitor the DOR system on vehicles 

so-equipped for malfunctions that reduce the ozone reduction 

performance of the system. 

(14.1.2) For 2003, 2004, and 2005 model year vehicles subject to the malfunction 

criteria of section (e)(14.2.1) below, manufacturers may request to be 

exempted from DOR system monitoring. The Executive Officer shall 

approve the exemption upon the manufacturer: 

(A) Agreeing that the DOR system receive only 50 percent of the NMOG 

credit assigned to the DOR system as calculated under Air Resources 

Board (ARB) Manufacturers Advisory Correspondence (MAC) No. 99-06, 

December 20, 1999, which is hereby incorporated by reference herein. 

(B) Identifying the DOR system component(s) as an emission control device 

on both the underhood emission control label and a separate label as 

specified below. The DOR system shall be included in the list of emission 

control devices on the underhood emission control label and be identified 

as a “DOR system” or other equivalent term from SAE J1930 

"Electrical/Electronic Systems Diagnostic Terms, Definitions, 

Abbreviations, and Acronyms – Equivalent to ISO/TR 15031-2:April 30, 

2002 (SAE 1930)", incorporated by reference. A separate label shall be 

located on or near the DOR system component(s) in a location that is 

visible to repair technicians prior to the removal of any parts necessary to 

replace the DOR system component(s) and shall identify the components 

as a “DOR system” or other equivalent SAE J1930 term. 

(14.2) Malfunction Criteria: 
54

(14.2.1) For vehicles in which the NMOG credit assigned to the DOR system, as 

calculated in accordance with ARB MAC No. 99-06, is less than or equal 

to 50 percent of the applicable FTP NMOG standard, the OBD II system 

shall detect a malfunction when the DOR system has no detectable 

amount of ozone reduction. 

(14.2.2) For vehicles in which the NMOG credit assigned to the DOR system, as 

calculated in accordance with ARB MAC No. 99-06, is greater than 50 

percent of the applicable FTP NMOG standard, the OBD II system shall 

detect a malfunction when the ozone reduction performance of the DOR 

system deteriorates to a point where the difference between the NMOG 

credit assigned to the properly operating DOR system and the NMOG 

credit calculated for a DOR system performing at the level of the 

malfunctioning system exceeds 50 percent of the applicable FTP NMOG 

standard. 

(14.2.3) For vehicles equipped with a DOR system, the manufacturer may modify 

any of the applicable NMOG malfunction criteria in sections (e)(1)-(3), 

(e)(5)-(8), (e)(11)-(e)(13), and (e)(16) by adding the NMOG credit received 

by the DOR system to the required NMOG malfunction criteria (e.g., a 

malfunction criteria of 1.5 x NMOG standard would be modified to (1.5 x 

NMOG standard) + DOR system NMOG credit). 

(14.3) Monitoring Conditions: Manufacturers shall define the monitoring conditions 

for malfunctions identified in section (e)(14.2) in accordance with sections 

(d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). 

(14.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(15) COMPREHENSIVE COMPONENT MONITORING

(15.1) Requirement: 

(15.1.1) Except as provided in sections (e)(15.1.3), (e)(15.1.4), and (e)(16), the 

OBD II system shall monitor for malfunction any electronic powertrain 

component/system not otherwise described in sections (e)(1) through 

(e)(14) that either provides input to (directly or indirectly) or receives 

commands from the on-board computer(s), and: (1) can affect emissions 

during any reasonable in-use driving condition, or (2) is used as part of 

the diagnostic strategy for any other monitored system or component. 

(A) Input Components: Input components required to be monitored may 

include the vehicle speed sensor, crank angle sensor, knock sensor, 

throttle position sensor, cam position sensor, fuel composition sensor (e.g. 

flexible fuel vehicles), and transmission electronic components such as 

sensors, modules, and solenoids which provide signals to the powertrain 

control system. 

(B) Output Components/Systems: Output components/systems required to be 

monitored may include the idle speed control system, automatic 

transmission solenoids or controls, variable length intake manifold runner 

systems, supercharger or turbocharger electronic components, heated 

fuel preparation systems, and a warm-up catalyst bypass valve. 

(15.1.2) For purposes of criteria (1) in section (e)(15.1.1) above, the manufacturer 

shall determine whether a powertrain input or output component/system 
55

can affect emissions. If the Executive Officer reasonably believes that a 

manufacturer has incorrectly determined that a component/system cannot 

affect emissions, the Executive Officer shall require the manufacturer to 

provide emission data showing that the component/system, when 

malfunctioning and installed in a suitable test vehicle, does not have an 

emission effect. The Executive Officer may request emission data for any 

reasonable driving condition. 

(15.1.3) Manufacturers shall monitor for malfunction electronic powertrain input or 

output components/systems associated with an electronic transfer case, 

electronic power steering system, or other components that are driven by 

the engine and not related to the control of fueling, air handling, or 

emissions only if the component or system is used as part of the 

diagnostic strategy for any other monitored system or component. 

(15.1.4) Except as specified for hybrids in section (e)(15.1.5), manufacturers shall 

monitor for malfunction electronic powertrain input or output 

components/systems associated with components that only affect 

emissions by causing additional electrical load to the engine and are not 

related to the control of fueling, air handling, or emissions only if the 

component or system is used as part of the diagnostic strategy for any 

other monitored system or component. 

(15.1.5) For hybrids, manufacturers shall submit a plan to the Executive Officer 

for approval of the hybrid components determined by the manufacturer to 

be subject to monitoring in section (e)(15.1.1). In general, the Executive 

Officer shall approve the plan if it includes monitoring of all 

components/systems used as part of the diagnostic strategy for any other 

monitored system or component, monitoring of all energy input devices to 

the electrical propulsion system, monitoring of battery and charging 

system performance, monitoring of electric motor performance, and 

monitoring of regenerative braking performance. 

(15.2) Malfunction Criteria: 

(15.2.1) Input Components: 

(A) The OBD II system shall detect malfunctions of input components caused 

by a lack of circuit continuity, out of range values, and, where feasible, 

rationality faults. To the extent feasible, the rationality fault diagnostics 

shall verify that a sensor output is neither inappropriately high nor 

inappropriately low (e.g., “two-sided” diagnostics). 

(B) To the extent feasible on all 2005 and subsequent model year vehicles, 

rationality faults shall be separately detected and store different fault 

codes than the respective lack of circuit continuity and out of range 

diagnostics. Additionally, input component lack of circuit continuity and 

out of range faults shall be separately detected and store different fault 

codes for each distinct malfunction (e.g., out-of-range low, out-of-range 

high, open circuit, etc.). Manufacturers are not required to store separate 

fault codes for lack of circuit continuity faults that cannot be distinguished 

from other out-of-range circuit faults. 

(C) For vehicles that require precise alignment between the camshaft and the 

crankshaft, the OBD II system shall monitor the crankshaft position 

sensor(s) and camshaft position sensor(s) to verify proper alignment 
56

between the camshaft and crankshaft in addition to monitoring the 

sensors for circuit continuity and rationality malfunctions. Proper 

alignment monitoring between a camshaft and a crankshaft shall only be 

required in cases where both are equipped with position sensors. For 

2006 through 2008 model year Low Emission Vehicle II applications and 

all 2009 and subsequent model year vehicles equipped with VVT systems 

and a timing belt or chain, the OBD II system shall detect a malfunction if 

the alignment between the camshaft and crankshaft is off by one or more 

cam/crank sprocket cogs (e.g., the timing belt/chain has slipped by one or 

more teeth/cogs). If a manufacturer demonstrates that a single tooth/cog 

misalignment cannot cause a measurable increase in emissions during 

any reasonable driving condition, the manufacturer shall detect a 

malfunction when the minimum number of teeth/cogs misalignment 

needed to cause a measurable emission increase has occurred. For the 

2006 through 2009 model years only, a manufacturer may also request 

Executive Officer approval to use a larger threshold than one tooth/cog. 

The Executive Officer shall approve the request upon determining that the 

manufacturer has demonstrated that hardware modifications are 

necessary to meet the one tooth/cog threshold and that further software 

modifications are not able to reduce the larger threshold. 

(15.2.2) Output Components/Systems: 

(A) The OBD II system shall detect a malfunction of an output 

component/system when proper functional response of the component 

and system to computer commands does not occur. If a functional check 

is not feasible, the OBD II system shall detect malfunctions of output 

components/systems caused by a lack of circuit continuity or circuit fault 

(e.g., short to ground or high voltage). For output component lack of 

circuit continuity faults and circuit faults, manufacturers are not required to 

store different fault codes for each distinct malfunction (e.g., open circuit, 

shorted low, etc.). Manufacturers are not required to activate an output 

component/system when it would not normally be active for the purposes 

of performing functional monitoring of output components/systems as 

required in section (e)(15). 

(B) The idle speed control system shall be monitored for proper functional 

response to computer commands. For strategies based on deviation from 

target idle speed, a malfunction shall be detected when either of the 

following conditions occur: 

(i) The idle speed control system cannot achieve the target idle speed 

within 200 revolutions per minute (rpm) above the target speed or 100 

rpm below the target speed. The Executive Officer shall allow larger 

engine speed tolerances upon determining that a manufacturer has 

submitted data and/or an engineering evaluation which demonstrate 

that the tolerances can be exceeded without a malfunction being 

present. 

(ii) The idle speed control system cannot achieve the target idle speed 

within the smallest engine speed tolerance range required by the 

OBD II system to enable any other monitor. 

(15.3) Monitoring Conditions: 
57

(15.3.1) Input Components: 

(A) Except as provided in section (e)(15.3.1)(C), input components shall be 

monitored continuously for proper range of values and circuit continuity. 

(B) For rationality monitoring (where applicable): 

(i) For 2004 model year vehicles, manufacturers shall define the 

monitoring conditions for detecting malfunctions in accordance with 

section (d)(3.1). 

(ii) For 2005 and subsequent model year vehicles, manufacturers shall 

define the monitoring conditions for detecting malfunctions in 

accordance with sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio 

requirements), with the exception that rationality monitoring shall occur 

every time the monitoring conditions are met during the driving cycle in 

lieu of once per driving cycle as required in section (d)(3.1.2). 

(C) A manufacturer may request Executive Officer approval to disable 

continuous input component proper range of values or circuit continuity 

monitoring when a malfunction cannot be distinguished from other effects. 

 The Executive Officer shall approve the disablement upon determining 

that the manufacturer has submitted test data and/or documentation that 

demonstrate a properly functioning input component cannot be 

distinguished from a malfunctioning input component and that the 

disablement interval is limited only to that necessary for avoiding false 

detection. 

(15.3.2) Output Components/Systems: 

(A) Except as provided in section (e)(15.3.2)(D), monitoring for circuit 

continuity and circuit faults shall be conducted continuously. 

(B) Except as provided in section (e)(15.3.2)(C), for functional monitoring, 

manufacturers shall define the monitoring conditions for detecting 

malfunctions in accordance with sections (d)(3.1) and (d)(3.2) (i.e., 

minimum ratio requirements). 

(C) For the idle speed control system on all 2005 and subsequent model year 

vehicles, manufacturers shall define the monitoring conditions for 

functional monitoring in accordance with sections (d)(3.1) and (d)(3.2) 

(i.e., minimum ratio requirements), with the exception that functional 

monitoring shall occur every time the monitoring conditions are met during 

the driving cycle in lieu of once per driving cycle as required in section 

(d)(3.1.2). 

(D) A manufacturer may request Executive Officer approval to disable 

continuous output component circuit continuity or circuit fault monitoring 

when a malfunction cannot be distinguished from other effects. The 

Executive Officer shall approve the disablement upon determining that the 

manufacturer has submitted test data and/or documentation that 

demonstrate a properly functioning output component cannot be 

distinguished from a malfunctioning output component and that the 

disablement interval is limited only to that necessary for avoiding false 

detection. 

(15.4) MIL Illumination and Fault Code Storage: 

(15.4.1) Except as provided in section (e)(15.4.2) below, general requirements for 

MIL illumination and fault code storage are set forth in section (d)(2). 
58

(15.4.2) Exceptions to general requirements for MIL illumination. MIL illumination 

is not required in conjunction with storing a confirmed fault code for any 

comprehensive component if: 

(A) the component or system, when malfunctioning, could not cause vehicle 

emissions to increase by: 

(i) 25 percent or more for PC/LDT SULEV II vehicles, or 

(ii) 15 percent or more for all other vehicles, and

(B) the component or system is not used as part of the diagnostic strategy for 

any other monitored system or component. 

(15.4.3) For purposes of determining the emission increase in section 

(e)(15.4.2)(A), the manufacturer shall request Executive Officer approval 

of the test cycle/vehicle operating conditions for which the emission 

increase will be determined. Executive Officer approval shall be granted 

upon determining that the manufacturer has submitted data and/or 

engineering evaluation that demonstrate that the testing conditions 

represent in-use driving conditions where emissions are likely to be most 

affected by the malfunctioning component. For purposes of determining 

whether the specified percentages in section (e)(15.4.2)(A) are exceeded, 

if the approved testing conditions are comprised of an emission test cycle 

with an emission standard, the measured increase shall be compared to a 

percentage of the emission standard (e.g., if the increase is equal to or 

more than 15 percent of the emission standard for that test cycle). If the 

approved testing conditions are comprised of a test cycle or vehicle 

operating condition that does not have an emission standard, the 

measured increase shall be calculated as a percentage of the baseline 

test (e.g., if the increase from a back-to-back test sequence between 

normal and malfunctioning condition is equal to or more than 15 percent 

of the baseline test results from the normal condition). 

(16) OTHER EMISSION CONTROL OR SOURCE SYSTEM MONITORING

(16.1) Requirement: For other emission control or source systems that are: (1) not 

identified or addressed in sections (e)(1) through (e)(15) (e.g., hydrocarbon 

traps, homogeneous charge compression ignition (HCCI) controls, NOx 

storage devices, fuel-fired passenger compartment heaters, etc.), or (2) 

identified or addressed in section (e)(15) but not corrected or compensated 

for by the adaptive fuel control system (e.g., swirl control valves), 

manufacturers shall submit a plan for Executive Officer approval of the 

monitoring strategy, malfunction criteria, and monitoring conditions prior to 

introduction on a production vehicle intended for sale in California. 

Executive Officer approval shall be based on the effectiveness of the 

monitoring strategy, the malfunction criteria utilized, the monitoring conditions 

required by the diagnostic, and, if applicable, the determination that the 

requirements of section (e)(16.3) below are satisfied. 

(16.2) For purposes of section (e)(16), emission source systems are components or 

devices that emit pollutants subject to vehicle evaporative and exhaust 

emission standards (e.g., NMOG, CO, NOx, PM, etc.) and include nonelectronic components and non-powertrain components (e.g., fuel-fired 

passenger compartment heaters, on-board reformers, etc.). 
59

(16.3) Except as provided below in this paragraph, for 2005 and subsequent model 

year vehicles that utilize emission control systems that alter intake air flow or 

cylinder charge characteristics by actuating valve(s), flap(s), etc. in the intake 

air delivery system (e.g., swirl control valve systems), the manufacturers, in 

addition to meeting the requirements of section (e)(16.1) above, may elect to 

have the OBD II system monitor the shaft to which all valves in one intake 

bank are physically attached in lieu of monitoring the intake air flow, cylinder 

charge, or individual valve(s)/flap(s) for proper functional response. For nonmetal shafts or segmented shafts, the monitor shall verify all shaft segments 

for proper functional response (e.g., by verifying the segment or portion of the 

shaft furthest from the actuator properly functions). For systems that have 

more than one shaft to operate valves in multiple intake banks, 

manufacturers are not required to add more than one set of detection 

hardware (e.g., sensor, switch, etc.) per intake bank to meet this requirement. 

 Vehicles utilizing these emission control systems designed and certified for 

2004 or earlier model year vehicles and carried over to the 2005 through 

2009 model year shall not be required to meet the provisions of section 

(e)(16.3) until the engine or intake air delivery system is redesigned. 

(17) EXCEPTIONS TO MONITORING REQUIREMENTS

(17.1) Except as provided in sections (e)(17.1.1) through (17.1.3) below, upon 

request of a manufacturer or upon the best engineering judgment of the ARB, 

the Executive Officer may revise the emission threshold for a malfunction on 

any diagnostic required in section (e) if the most reliable monitoring method 

developed requires a higher threshold to prevent significant errors of 

commission in detecting a malfunction. 

(17.1.1) For PC/LDT SULEV II vehicles, the Executive Officer shall approve a 

malfunction criteria of 2.5 times the applicable FTP standards in lieu of 1.5 

wherever required in section (e). 

(17.1.2) For 2004 model year PC/LDT SULEV II vehicles only, the Executive 

Officer shall approve monitors with thresholds that exceed 2.5 times the 

applicable FTP standard if the manufacturer demonstrates that a higher 

threshold is needed given the state of development of the vehicle and that 

the malfunction criteria and monitoring approach and technology (e.g., 

fuel system limits, percent misfire, monitored catalyst volume, etc.) are at 

least as stringent as comparable ULEV (not ULEV II) vehicles. 

(17.1.3) For vehicles certified to Federal Bin 3 or Bin 4 emission standards, 

manufacturers shall utilize the ULEV II vehicle NMOG and CO malfunction 

criteria (e.g., 1.5 times the Bin 3 or Bin 4 NMOG and CO standards) and 

the PC/LDT SULEV II vehicle NOx malfunction criteria (e.g., 2.5 times the 

Bin 3 or Bin 4 NOx standards). 

(17.1.4) For medium-duty vehicles certified to an engine dynamometer tailpipe 

emission standard, the manufacturer shall request Executive Officer 

approval of a malfunction criterion that is equivalent to that proposed for 

each monitor in section (e). The Executive Officer shall approve the 

request upon finding that the manufacturer has used good engineering 

judgment in determining the equivalent malfunction criterion and that the 
60

criterion will provide for similar timeliness in detection of malfunctioning 

components. 

(17.2) Whenever the requirements in section (e) of this regulation require a 

manufacturer to meet a specific phase-in schedule (e.g., (e)(11) cold start 

emission reduction strategy monitoring requires 30 percent in 2006 model 

year, 60 percent in 2007 model year, and 100 percent in 2008 model year): 

(17.2.1) The phase-in percentages shall be based on the manufacturer’s 

projected sales volume for all vehicles subject to the requirements of title 

13, CCR section 1968.2 unless specifically stated otherwise in section (e). 

(17.2.2) Manufacturers may use an alternate phase-in schedule in lieu of the 

required phase-in schedule if the alternate phase-in schedule provides for 

equivalent compliance volume as defined in section (c) except as 

specifically noted for the phase in of in-use monitor performance ratio 

monitoring conditions in section (d)(3.2). 

(17.2.3) Small volume manufacturers may use an alternate phase-in schedule in 

accordance with section (e)(17.2.2) in lieu of the required phase-in 

schedule or may meet the requirement on all vehicles by the final year of 

the phase-in in lieu of meeting the specific phase-in requirements for each 

model year (e.g., in the example in section (e)(17.2), small volume 

manufacturers are required to meet 100 percent in the 2008 model year 

for cold start emission reduction strategy monitoring, but not 30 percent in 

the 2006 model year or 60 percent in the 2007 model year). 

(17.3) Manufacturers may request Executive Officer approval to disable an OBD II 

system monitor at ambient temperatures below twenty degrees Fahrenheit 

(20°F) (low ambient temperature conditions may be determined based on 

intake air or engine coolant temperature) or at elevations above 8000 feet 

above sea level. The Executive Officer shall approve the request upon 

determining that the manufacturer has provided data and/or an engineering 

evaluation that demonstrate that monitoring during the conditions would be 

unreliable. A manufacturer may further request, and the Executive Officer 

shall approve, that an OBD II system monitor be disabled at other ambient 

temperatures upon determining that the manufacturer has demonstrated with 

data and/or an engineering evaluation that misdiagnosis would occur at the 

ambient temperatures because of its effect on the component itself (e.g., 

component freezing). 

(17.4) Manufacturers may request Executive Officer approval to disable monitoring 

systems that can be affected by low fuel level or running out of fuel (e.g., 

misfire detection) when the fuel level is 15 percent or less of the nominal 

capacity of the fuel tank. The Executive Officer shall approve the request 

upon determining that the manufacturer has submitted data and/or an 

engineering evaluation that demonstrate that monitoring at the fuel levels 

would be unreliable. 

(17.5) Manufacturers may disable monitoring systems that can be affected by 

vehicle battery or system voltage levels. 

(17.5.1) For monitoring systems affected by low vehicle battery or system 

voltages, manufacturers may disable monitoring systems when the battery 

or system voltage is below 11.0 Volts. Manufacturers may request 
61

Executive Officer approval to utilize a voltage threshold higher than 11.0 

Volts to disable system monitoring. The Executive Officer shall approve 

the request upon determining that the manufacturer has submitted data 

and/or an engineering evaluation that demonstrate that monitoring at the 

voltages would be unreliable and that either operation of a vehicle below 

the disablement criteria for extended periods of time is unlikely or the 

OBD II system monitors the battery or system voltage and will detect a 

malfunction at the voltage used to disable other monitors. 

(17.5.2) For monitoring systems affected by high vehicle battery or system 

voltages, manufacturers may request Executive Officer approval to 

disable monitoring systems when the battery or system voltage exceeds a 

manufacturer-defined voltage. The Executive Officer shall approve the 

request upon determining that the manufacturer has submitted data 

and/or an engineering evaluation that demonstrate that monitoring above 

the manufacturer-defined voltage would be unreliable and that either the 

electrical charging system/alternator warning light is illuminated (or voltage 

gauge is in the “red zone”) or that the OBD II system monitors the battery 

or system voltage and will detect a malfunction at the voltage used to 

disable other monitors. 

(17.6) A manufacturer may disable affected monitoring systems in vehicles 

designed to accommodate the installation of Power Take-Off (PTO) units (as 

defined in section (c)), provided disablement occurs only while the PTO unit 

is active, and the OBD II readiness status is cleared by the on-board 

computer (i.e., all monitors set to indicate “not complete”) while the PTO unit 

is activated (see section (g)(4.1)). If the disablement occurs, the readiness 

status may be restored to its state prior to PTO activation when the 

disablement ends. 

(17.7) A manufacturer may request Executive Officer approval to disable affected 

monitoring systems in vehicles equipped with tire pressure monitoring 

systems that cause a vehicle to enter a default mode of operation (e.g., 

reduced top speed) when a tire pressure problem is detected. The Executive 

Officer shall approve the request upon determining that the manufacturer has 

submitted data and/or an engineering evaluation that demonstrate that the 

default mode can affect monitoring system performance, that the tire 

pressure monitoring system will likely result in action by the consumer to 

correct the problem, and that the disablement will not prevent or hinder 

effective testing in an Inspection and Maintenance program. 

(17.8) Whenever the requirements in section (e) of this regulation require monitoring 

“to the extent feasible”, the manufacturer shall submit its proposed monitor(s) 

for Executive Officer approval. The Executive Officer shall approve the 

proposal upon determining that the proposed monitor(s) meets the criteria of 

“to the extent feasible” by considering the best available monitoring 

technology to the extent that it is known or should have been known to the 

manufacturer and given the limitations of the manufacturer’s existing 

hardware, the extent and degree to which the monitoring requirements are 

met in full, the limitations of monitoring necessary to prevent significant errors 

of commission and omission, and the extent to which the manufacturer has 

considered and pursued alternative monitoring concepts to meet the 
62

requirements in full. The manufacturer’s consideration and pursuit of 

alternative monitoring concepts shall include evaluation of other modifications 

to the proposed monitor(s), the monitored components themselves, and other 

monitors that use the monitored components (e.g., altering other monitors to 

lessen the sensitivity and reliance on the component or characteristic of the 

component subject to the proposed monitor(s)). 

(17.9) For 2004 model year vehicles certified to run on alternate fuels, 

manufacturers may request the Executive Officer to waive specific monitoring 

requirements in section (e) for which monitoring may not be reliable with 

respect to the use of alternate fuels. The Executive Officer shall grant the 

request upon determining that the manufacturer has demonstrated that the 

use of the alternate fuel could cause false illumination of the MIL even when 

using the best available monitoring technologies. 

(17.10) For 2004 model year vehicles only, wherever the requirements of section (e) 

reflect a substantive change from the requirements of title 13, CCR section 

1968.1(b) for 2003 model year vehicles, the manufacturer may request 

Executive Officer approval to continue to use the requirements of section 

1968.1 in lieu of the requirements of section (e). The Executive Officer shall 

approve the request upon determining that the manufacturer has submitted 

data and/or engineering evaluation that demonstrate that software or 

hardware changes would be required to comply with the requirements of 

section (e) and that the system complies with the requirements of section 

1968.1(b). 

(f) MONITORING REQUIREMENTS FOR DIESEL/COMPRESSION-IGNITION 

ENGINES. 

(1) NON-METHANE HYDROCARBON (NMHC) CONVERTING CATALYST 

MONITORING 

(1.1) Requirement: The OBD II system shall monitor the NMHC converting 

catalyst(s) for proper NMHC conversion capability. For vehicles equipped 

with catalyzed PM filters that convert NMHC emissions, the catalyst function 

of the PM filter shall be monitored in accordance with the PM filter 

requirements in section (f)(9). 

(1.2) Malfunction Criteria: 

(1.2.1) For purposes of section (f)(1), each catalyst in a series configuration that 

converts NMHC shall be monitored either individually or in combination 

with others. 

(1.2.2) Conversion Efficiency: 

(A) The OBD II system shall detect an NMHC catalyst malfunction when the 

catalyst conversion capability decreases to the point that NMHC 

emissions exceed: 

(i) For passenger cars, light-duty trucks, and MDPVs certified to a chassis 

dynamometer tailpipe emission standard: 

a. 5.0 times the applicable FTP NMHC standards for 2004 through 

2009 model year vehicles; 

b. 3.0 times the applicable FTP NMHC standards for 2010 through 

2012 model year vehicles; and 
63

c. 1.75 times the applicable FTP NMHC standards for 2013 and 

subsequent model year vehicles. 

(ii) For medium-duty vehicles (including MDPVs) certified to an engine 

dynamometer tailpipe emission standard: 

a. 2.5 times the applicable NMHC standards for 2007 through 2012 

model year vehicles; and 

b. 2.0 times the applicable NMHC standards or the applicable NOx 

standard by more than 0.2 g/bhp-hr (e.g., cause emissions to 

exceed 0.4 g/bhp-hr if the emission standard is 0.2 g/bhp-hr) for 

2013 and subsequent model year vehicles. 

(B) Except as provided below in section (f)(1.2.2)(C), if no failure or 

deterioration of the catalyst NMHC conversion capability could result in 

NMHC or NOx emissions exceeding the applicable malfunction criteria of 

section (f)(1.2.2)(A), the OBD II system shall detect a malfunction when 

the catalyst has no detectable amount of NMHC or NOx conversion 

capability. 

(C) For 2004 through 2009 model year vehicles, a manufacturer may request 

to be exempted from the requirements for NMHC catalyst conversion 

efficiency monitoring. The Executive Officer shall approve the request 

upon determining that the manufacturer has demonstrated, through data 

and/or engineering evaluation, that the average FTP test NMHC 

conversion efficiency of the system is less than 30 percent (i.e., the 

cumulative NMHC emissions measured at the outlet of the catalyst are 

more than 70 percent of the cumulative engine-out NMHC emissions 

measured at the inlet of the catalyst(s)). 

(1.2.3) Other Aftertreatment Assistance Functions. Additionally, for 2010 and 

subsequent model year vehicles, the catalyst(s) shall be monitored for 

other aftertreatment assistance functions: 

(A) For catalysts used to generate an exotherm to assist PM filter 

regeneration, the OBD II system shall detect a malfunction when the 

catalyst is unable to generate a sufficient exotherm to achieve 

regeneration of the PM filter. 

(B) For 2010 and subsequent model year passenger cars, light-duty trucks, 

and MDPVs certified to a chassis dynamometer tailpipe emission 

standard and 2013 and subsequent model year medium-duty vehicles 

(including MDPVs) certified to an engine dynamometer tailpipe emission 

standard, Ffor catalysts used to generate a feedgas constituency to assist 

SCR systems (e.g., to increase NO2 concentration upstream of an SCR 

system), the OBD II system shall detect a malfunction when the catalyst is 

unable to generate the necessary feedgas constituents for proper SCR 

system operation. 

(C) For catalysts located downstream of a PM filter and used to convert 

NMHC emissions during PM filter regeneration, the OBD II system shall 

detect a malfunction when the catalyst has no detectable amount of 

NMHC conversion capability. 

(D) For catalysts located downstream of an SCR system (e.g., and used to 

prevent ammonia slip), the OBD II system shall detect a malfunction when

the catalyst has no detectable amount of NMHC, CO, NOx, or PM 
64

conversion capability. Monitoring of the catalyst shall not be required if 

there is no measurable emission impact on the criteria pollutants (i.e., 

NMHC, CO, NOx, and PM) during any reasonable driving condition where 

the catalyst is most likely to affect criteria pollutants (e.g., during 

conditions most likely to result in ammonia generation or excessive 

reductant delivery). 

(1.2.4) Catalyst System Aging and Monitoring 

(A) For purposes of determining the catalyst malfunction criteria in sections 

(f)(1.2.2) and (1.2.3) for individually monitored catalysts, the manufacturer 

shall use a catalyst(s) deteriorated to the malfunction criteria using 

methods established by the manufacturer to represent real world catalyst 

deterioration under normal and malfunctioning engine operating 

conditions. If the catalyst system contains catalysts in parallel (e.g., a two 

bank exhaust system where each bank has its own catalyst), the 

malfunction criteria shall be determined with the “parallel” catalysts equally 

deteriorated. 

(B) For purposes of determining the catalyst malfunction criteria in sections 

(f)(1.2.2) and (1.2.3) for catalysts monitored in combination with others, 

the manufacturer shall submit a catalyst system aging and monitoring plan 

to the Executive Officer for review and approval. The plan shall include 

the description, emission control purpose, and location of each 

component, the monitoring strategy for each component and/or 

combination of components, and the method for determining the 

malfunction criteria of sections (f)(1.2.2) and (1.2.3) including the 

deterioration/aging process. If the catalyst system contains catalysts in 

parallel (e.g., a two bank exhaust system where each bank has its own 

catalyst), the malfunction criteria shall be determined with the “parallel” 

catalysts equally deteriorated. Executive Officer approval of the plan shall 

be based on the representativeness of the aging to real world catalyst 

system component deterioration under normal and malfunctioning engine 

operating conditions, the effectiveness of the method used to determine 

the malfunction criteria of section (f)(1.2), the ability of the component 

monitor(s) to pinpoint the likely area of malfunction and ensure the correct 

components are repaired/replaced in-use, and the ability of the 

component monitor(s) to accurately verify that each catalyst component is 

functioning as designed and as required in sections (f)(1.2.2) and (1.2.3). 

(1.3) Monitoring Conditions: 

(1.3.1) Manufacturers shall define the monitoring conditions for malfunctions 

identified in sections (f)(1.2.2) and (1.2.3) in accordance with sections 

(d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). For purposes of 

tracking and reporting as required in section (d)(3.2.2), all monitors used 

to detect malfunctions identified in sections (f)(1.2.2) and (1.2.3) shall be 

tracked separately but reported as a single set of values as specified in 

section (d)(5.2.2). 
65

(1.4) MIL Illumination and Fault Code Storage: 

(1.4.1) General requirements for MIL illumination and fault code storage are set 

forth in section (d)(2). 

(1.4.2) The monitoring method for the catalyst(s) shall be capable of detecting all 

instances, except diagnostic self-clearing, when a catalyst fault code has 

been cleared but the catalyst has not been replaced (e.g., catalyst 

overtemperature histogram approaches are not acceptable). 

(2) OXIDES OF NITROGREN (NOx) CONVERTING CATALYST MONITORING 

(2.1) Requirement: The OBD II system shall monitor the NOx converting catalyst(s) 

for proper conversion capability. For vehicles equipped with selective 

catalytic reduction (SCR) systems or other catalyst systems that utilize an 

active/intrusive reductant injection (e.g., active lean NOx catalysts utilizing 

diesel fuel injection), the OBD II system shall monitor the SCR or 

active/intrusive reductant injection system for proper performance. The 

individual electronic components (e.g., actuators, valves, sensors, heaters, 

pumps) in the SCR or active/intrusive reductant injection system shall be 

monitored in accordance with the comprehensive component requirements in 

section (f)(15). 

(2.2) Malfunction Criteria: 

(2.2.1) For purposes of section (f)(2), each catalyst in a series configuration that 

converts NOx shall be monitored either individually or in combination with 

others. 

(2.2.2) Conversion Efficiency: 

(A) The OBD II system shall detect a NOx catalyst malfunction when the 

catalyst conversion capability decreases to the point that NOx or NMHC 

emissions exceed: 

(i) For passenger cars, light-duty trucks, and MDPVs certified to a chassis 

dynamometer tailpipe emission standard: 

a. 3.0 times the applicable FTP standards for 2004 through 2009 

model year vehicles; 

b. 2.5 times the applicable FTP standards for 2010 through 2012 

model year vehicles; and 

c. 1.75 times the applicable FTP standards for 2013 and subsequent 

model year vehicles. 

(ii) For medium-duty vehicles (including MDPVs) certified to an engine 

dynamometer tailpipe emission standard: 

a. the applicable NOx standard by more than 0.5 g/bhp-hr (e.g., cause 

NOx emissions to exceed 0.7 g/bhp-hr if the emission standard is 

0.2 g/bhp-hr) as measured from an applicable cycle emission test 

or 3.5 times the applicable NMHC standard for 2007 through 2009 

model year vehicles; 

b. the applicable NOx standard by more than 0.34 g/bhp-hr (e.g., 

cause NOx emissions to exceed 0.56 g/bhp-hr if the emission 

standard is 0.2 g/bhp-hr) as measured from an applicable cycle 

emission test or 2.5 times the applicable NMHC standard for 2010 

through 2012 model year vehicles; and 
66

c. the applicable NOx standard by more than 0.2 g/bhp-hr (e.g., cause 

NOx emissions to exceed 0.4 g/bhp-hr if the emission standard is 

0.2 g/bhp-hr) as measured from an applicable cycle emission test 

or 2.0 times the applicable NMHC standard for 2013 and 

subsequent model year vehicles. 

(B) Except as provided below in section (f)(2.2.2)(C), if no failure or 

deterioration of the catalyst NOx or NMHC conversion capability could 

result in NOx or NMHC emissions exceeding the applicable malfunction 

criteria of section (f)(2.2.2), the OBD II system shall detect a malfunction 

when the catalyst has no detectable amount of NOx or NMHC conversion 

capability. 

(C) For 2004 through 2009 model year vehicles, a manufacturer may request 

to be exempted from the requirements for NOx catalyst conversion 

efficiency monitoring. The Executive Officer shall approve the request 

upon determining that the manufacturer has demonstrated, through data 

and/or engineering evaluation, that the average FTP test NOx conversion 

efficiency of the system is less than 30 percent (i.e., the cumulative NOx 

emissions measured at the outlet of the catalyst are more than 70 percent 

of the cumulative engine-out NOx emissions measured at the inlet of the 

catalyst(s)). 

(2.2.3) Selective Catalytic Reduction (SCR) or Other Active/Intrusive Reductant 

Injection System Performance: 

(A) Reductant Delivery Performance: 

(i) For 2007 and subsequent model year vehicles, the OBD II system 

shall detect a system malfunction prior to any failure or deterioration of 

the system to properly regulate reductant delivery (e.g., urea injection, 

separate injector fuel injection, post injection of fuel, air assisted 

injection/mixing) that would cause a vehicle’s NOx or NMHC emissions 

to exceed the applicable emission levels specified in sections 

(f)(2.2.2)(A). 

(ii) If no failure or deterioration of the reductant delivery system could 

result in a vehicle’s NOx or NMHC emissions exceeding the applicable 

malfunction criteria specified in section (f)(2.2.3)(A)(i), the OBD II 

system shall detect a malfunction when the system has reached its 

control limits such that it is no longer able to deliver the desired 

quantity of reductant. 

(B) If the catalyst system uses a reductant other than the fuel used for the 

engine or uses a reservoir/tank for the reductant that is separate from the 

fuel tank used for the engine, the OBD II system shall detect a 

malfunction when there is no longer sufficient reductant available to 

properly operate the reductant system (e.g., the reductant tank is empty). 

(C) If the catalyst system uses a reservoir/tank for the reductant that is 

separate from the fuel tank used for the vehicle, the OBD II system shall 

detect a malfunction when an improper reductant is used in the reductant 

reservoir/tank (e.g., the reductant tank is filled with something other than 

the reductant). 
67

(D) Feedback control: Except as provided for in section (f)(2.2.3)(E), if the 

vehicle is equipped with feedback or feed-forward control of the reductant 

injection, the OBD II system shall detect a malfunction: 

(i) If the system fails to begin feedback control within a manufacturer 

specified time interval; 

(ii) If a failure or deterioration causes open loop or default operation; or 

(iii) If feedback the control system has used up all of the adjustment 

allowed by the manufacturer or reached its maximum authority and 

cannot achieve the feedback target. 

(E) A manufacturer may request Executive Officer approval to temporarily 

disable monitoring for the malfunction criteria specified in section 

(f)(2.2.3)(D)(iii) during conditions that a manufacturer cannot robustly 

distinguish between a malfunctioning system and a properly operating 

system. The Executive Officer shall approve the disablement upon the 

manufacturer submitting data and/or analysis demonstrating that the 

control system, when operating as designed on a vehicle with all emission 

controls working properly, routinely operates during these conditions with 

all of the adjustment allowed by the manufacturer used up. 

(F) In lieu of detecting the malfunctions specified in sections (f)(2.2.3)(D)(i) 

and (ii) with a reductant injection system-specific monitor, the OBD II 

system may monitor the individual parameters or components that are 

used as inputs for reductant injection feedback control provided that the 

monitors detect all malfunctions that meet the criteria in sections 

(f)(2.2.3)(D)(i) and (ii). 

(2.2.4) Catalyst System Aging and Monitoring 

(A) For purposes of determining the catalyst malfunction criteria in section 

(f)(2.2.2) for individually monitored catalysts, the manufacturer shall use a 

catalyst deteriorated to the malfunction criteria using methods established 

by the manufacturer to represent real world catalyst deterioration under 

normal and malfunctioning engine operating conditions. If the catalyst 

system contains catalysts in parallel (e.g., a two bank exhaust system 

where each bank has its own catalyst), the malfunction criteria shall be 

determined with the “parallel” catalysts equally deteriorated. 

(B) For purposes of determining the catalyst malfunction criteria in section 

(f)(2.2.2) for catalysts monitored in combination with others, the 

manufacturer shall submit a catalyst system aging and monitoring plan to 

the Executive Officer for review and approval. The plan shall include the 

description, emission control purpose, and location of each component, 

the monitoring strategy for each component and/or combination of 

components, and the method for determining the malfunction criteria of 

section (f)(2.2.2) including the deterioration/aging process. If the catalyst 

system contains catalysts in parallel (e.g., a two bank exhaust system 

where each bank has its own catalyst), the malfunction criteria shall be 

determined with the “parallel” catalysts equally deteriorated. Executive 

Officer approval of the plan shall be based on the representativeness of 

the aging to real world catalyst system component deterioration under 

normal and malfunctioning engine operating conditions, the effectiveness 

of the method used to determine the malfunction criteria of section 
68

(f)(2.2.2), the ability of the component monitor(s) to pinpoint the likely area 

of malfunction and ensure the correct components are repaired/replaced 

in-use, and the ability of the component monitor(s) to accurately verify that 

each catalyst component is functioning as designed and as required in 

section (f)(2.2.2). 

(2.3) Monitoring Conditions: 

(2.3.1) Manufacturers shall define the monitoring conditions for malfunctions 

identified in sections (f)(2.2.2) and (f)(2.2.3)(C) (i.e., catalyst efficiency, 

improper reductant) in accordance with sections (d)(3.1) and (d)(3.2) (i.e., 

minimum ratio requirements). For purposes of tracking and reporting as 

required in section (d)(3.2.2), all monitors used to detect malfunctions 

identified in section (f)(2.2.2) shall be tracked separately but reported as a 

single set of values as specified in section (d)(5.2.2). 

(2.3.2) Except as provided for in section (f)(2.3.3), Tthe OBD II system shall 

monitor continuously for malfunctions identified in section (f)(2.2.3)(A), 

(B), and (D) (e.g., SCR performance, insufficient reductant, feedback 

control). 

(2.3.3) Manufacturers may request Executive Officer approval to temporarily 

disable continuous monitoring under conditions technically necessary to 

ensure robust detection of malfunctions and to avoid false passes and 

false indications of malfunctions. The Executive Officer shall approve the 

request upon determining that the manufacturer has submitted data 

and/or an engineering evaluation which demonstrate that a properly 

operating system cannot be distinguished from a malfunctioning system 

and that the disablement interval is limited only to that which is technically 

necessary.

(2.4) MIL Illumination and Fault Code Storage: 

(2.4.1) Except as provided below for reductant faults, general requirements for 

MIL illumination and fault code storage are set forth in section (d)(2). 

(2.4.2) If the OBD II system is capable of discerning that a system fault is being 

caused by a empty reductant tank: 

(A) The manufacturer may request Executive Officer approval to delay 

illumination of the MIL if the vehicle is equipped with an alternative 

indicator for notifying the vehicle operator of the malfunction. The 

Executive Officer shall approve the request upon determining the 

alternative indicator is of sufficient illumination and location to be readily 

visible under all lighting conditions and provides equivalent assurance that 

a vehicle operator will be promptly notified and that corrective action will 

be undertaken. 

(B) If the vehicle is not equipped with an alternative indicator and the MIL 

illuminates, the MIL may be immediately extinguished and the 

corresponding fault codes erased once the OBD II system has verified 

that the reductant tank has been properly refilled and the MIL has not 

been illuminated for any other type of malfunction.
69

(C) The Executive Officer may approve other strategies that provide 

equivalent assurance that a vehicle operator will be promptly notified and 

that corrective action will be undertaken. 

(2.4.3) The monitoring method for the catalyst(s) shall be capable of detecting all 

instances, except diagnostic self-clearing, when a catalyst fault code has 

been cleared but the catalyst has not been replaced (e.g., catalyst 

overtemperature histogram approaches are not acceptable). 

(3) MISFIRE MONITORING 

(3.1) Requirement: 

(3.1.1) The OBD II system shall monitor the engine for misfire causing excess 

emissions. The OBD II system shall be capable of detecting misfire 

occurring in one or more cylinders. To the extent possible without adding 

hardware for this specific purpose, the OBD II system shall also identify 

the specific misfiring cylinder. 

(3.1.2) If more than one cylinder is misfiring, a separate fault code shall be stored 

indicating that multiple cylinders are misfiring. When identifying multiple 

cylinder misfire, the OBD II system is not required to also identify each of 

the misfiring cylinders individually through separate fault codes. 

(3.2) Malfunction Criteria: 

(3.2.1) The OBD II system shall detect a misfire malfunction when one or more 

cylinders are continuously misfiring. 

(3.2.2) Additionally, for 2010 and subsequent model year vehicles equipped with 

sensors that can detect combustion or combustion quality (e.g., for use in 

homogeneous charge compression ignition (HCCI) control systems): 

(A) The OBD II system shall detect a misfire malfunction that would cause a 

vehicle’s NMHC, CO, NOx, or PM emissions to exceed:

(i) For passenger cars, light-duty trucks, and MDPVs certified to a chassis 

dynamometer tailpipe emission standard, 1.5 times any of the 

applicable FTP standards. 

(ii) For medium-duty vehicles (including MDPVs) certified to an engine 

dynamometer tailpipe emission standard, 2.0 times any of the 

applicable NMHC, CO, and NOx standards or 0.03 g/bhp-hr PM as 

measured from an applicable cycle emission test. 

(B) Manufacturers shall determine the percentage of misfire evaluated in 

1000 revolution increments that would cause NMHC, CO, NOx, or PM 

emissions from an emission durability demonstration vehicle to exceed 

the levels specified in section (f)(3.2.2)(A) if the percentage of misfire 

were present from the beginning of the test. To establish this percentage 

of misfire, the manufacturer shall utilize misfire events occurring at equally 

spaced, complete engine cycle intervals, across randomly selected 

cylinders throughout each 1000-revolution increment. If this percentage 

of misfire is determined to be lower than one percent, the manufacturer 

may set the malfunction criteria at one percent. 

(C) Subject to Executive Officer approval, a manufacturer may employ other 

revolution increments. The Executive Officer shall grant approval upon 

determining that the manufacturer has demonstrated that the strategy 

would be equally effective and timely in detecting misfire. 
70

(3.2.3) A malfunction shall be detected if the percentage of misfire established in 

section (f)(3.2.2)(B) is exceeded regardless of the pattern of misfire 

events (e.g., random, equally spaced, continuous). 

(3.2.4) For multiple cylinder misfire situations that result in a misfire rate greater 

than or equal to 50 percent, the OBD II system shall only be required to 

detect a misfire malfunction for situations that are caused by a single 

component failure.

(3.3) Monitoring Conditions: 

(3.3.1) The OBD II system shall monitor for misfire during engine idle conditions 

at least once per driving cycle in which the monitoring conditions for 

misfire are met. A manufacturer shall submit monitoring conditions to the 

Executive Officer for approval. The Executive Officer shall approve 

manufacturer-defined monitoring conditions that are determined (based 

on manufacturer-submitted data and/or other engineering documentation) 

to: (i) be technically necessary to ensure robust detection of malfunctions 

(e.g., avoid false passes and false detection of malfunctions), (ii) require 

no more than 1000 cumulative engine revolutions, and (iii) do not require 

any single continuous idle operation of more than 15 seconds to make a 

determination that a malfunction is present (e.g., a decision can be made 

with data gathered during several idle operations of 15 seconds or less); 

or satisfy the requirements of (d)(3.1) with alternative engine operating 

conditions. 

(3.3.2) Manufacturers may request Executive Officer approval to use alternate 

monitoring conditions (e.g., off-idle). The Executive Officer shall approve 

alternate monitoring conditions that are determined (based on 

manufacturer-submitted data and/or other engineering documentation) to 

ensure equivalent robust detection of malfunctions and equivalent 

timeliness in detection of malfunctions. 

(3.3.3) Additionally, for 2010 and subsequent model year vehicles subject to 

(f)(3.2.2): 

(A) The OBD II system shall continuously monitor for misfire under all positive 

torque engine speeds and load conditions. 

(B) If a monitoring system cannot detect all misfire patterns under all required 

engine speed and load conditions as required in section (f)(3.3.3)(A), the 

manufacturer may request Executive Officer approval to accept the 

monitoring system. In evaluating the manufacturer’s request, the 

Executive Officer shall consider the following factors: the magnitude of the 

region(s) in which misfire detection is limited, the degree to which misfire 

detection is limited in the region(s) (i.e., the probability of detection of 

misfire events), the frequency with which said region(s) are expected to be 

encountered in-use, the type of misfire patterns for which misfire detection 

is troublesome, and demonstration that the monitoring technology 

employed is not inherently incapable of detecting misfire under required 

conditions (i.e., compliance can be achieved on other engines). The 

evaluation shall be based on the following misfire patterns: equally spaced 

misfire occurring on randomly selected cylinders, single cylinder 

continuous misfire, and paired cylinder (cylinders firing at the same crank 

angle) continuous misfire. 
71

(3.4) MIL Illumination and Fault Code Storage: 

(3.4.1) General requirements for MIL illumination and fault code storage are set 

forth in section (d)(2). 

(3.4.2) Additionally, for 2010 and subsequent model year vehicles subject to 

(f)(3.2.2): 

(A) Upon detection of the percentage of misfire specified in section 

(f)(3.2.2)(B), the following criteria shall apply for MIL illumination and fault 

code storage: 

(i) A pending fault code shall be stored no later than after the fourth 

exceedance of the percentage of misfire specified in section 

(f)(3.2.2)(B) during a single driving cycle. 

(ii) If a pending fault code is stored, the OBD II system shall illuminate the 

MIL and store a confirmed fault code within 10 seconds if the 

percentage of misfire specified in section (f)(3.2.2)(B) is again 

exceeded four times during: (a) the driving cycle immediately following 

the storage of the pending fault code, regardless of the conditions 

encountered during the driving cycle; or (b) on the next driving cycle in 

which similar conditions (see section (c)) to the engine conditions that 

occurred when the pending fault code was stored are encountered. 

(iii) The pending fault code may be erased at the end of the next driving 

cycle in which similar conditions to the engine conditions that occurred 

when the pending fault code was stored have been encountered 

without an exceedance of the specified percentage of misfire. The 

pending code may also be erased if similar conditions are not 

encountered during the next 80 driving cycles immediately following 

initial detection of the malfunction. 

(B) Storage of freeze frame conditions. 

(i) The OBD II system shall store and erase freeze frame conditions either 

in conjunction with storing and erasing a pending fault code or in 

conjunction with storing a confirmed fault code and erasing a 

confirmed fault code. 

(ii) If freeze frame conditions are stored for a malfunction other than a 

misfire malfunction when a fault code is stored as specified in section 

(f)(3.4.2), the stored freeze frame information shall be replaced with 

freeze frame information regarding the misfire malfunction. 

(C) Storage of misfire conditions for similar conditions determination. Upon 

detection of misfire under section (f)(3.4.2), the OBD II system shall store 

the following engine conditions: engine speed, load, and warm-up status 

of the first misfire event that resulted in the storage of the pending fault 

code. 

(D) Extinguishing the MIL. The MIL may be extinguished after three 

sequential driving cycles in which similar conditions have been 

encountered without an exceedance of the specified percentage of 

misfire. 

(4) FUEL SYSTEM MONITORING 

(4.1) Requirement: 
72

The OBD II system shall monitor the fuel delivery system to determine its 

ability to comply with emission standards. The individual electronic 

components (e.g., actuators, valves, sensors, pumps) that are used in the 

fuel system and not specifically addressed in this section shall be monitored 

in accordance with the comprehensive component requirements in section 

(f)(15). 

(4.2) Malfunction Criteria: 

(4.2.1) Fuel system pressure control: 

(A) The OBD II system shall detect a malfunction of the fuel system pressure 

control system (e.g., fuel, hydraulic fluid) prior to any failure or 

deterioration that would cause a vehicle’s NMHC, CO, NOx, or PM 

emissions to exceed: 

(i) For passenger cars, light-duty trucks, and MDPVs certified to a chassis 

dynamometer tailpipe emission standard: 

a. 3.0 times the applicable FTP standards for 2004 through 2009 

model year vehicles; 

b. 2.0 times the applicable FTP standards for 2010 through 2012 

model year vehicles; and 

c. 1.5 times the applicable FTP NMHC, CO, or NOx standards or 2.0 

times the applicable FTP PM standard for 2013 and subsequent 

model year vehicles. 

(ii) For medium-duty vehicles (including MDPVs) certified to an engine 

dynamometer tailpipe emission standard: 

a. 1.5 times any of the applicable NMHC, CO, and NOx standards or 

0.03 g/bhp-hr PM as measured from an applicable cycle emission 

test for 2007 and subsequent model year vehicles certified to an 

engine dynamometer tailpipe NOx emission standard of greater 

than 0.50 g/bhp-hr NOx; 

b. 2.5 times any of the applicable NMHC or CO standards, the 

applicable NOx standard by more than 0.3 g/bhp-hr (e.g., cause 

NOx emissions to exceed 0.5 g/bhp-hr if the emission standard is 

0.2 g/bhp-hr) as measured from an applicable cycle emission test, 

or 0.03 g/bhp-hr PM as measured from an applicable cycle 

emission test for 2007 through 2012 model year vehicles certified 

to an engine dynamometer tailpipe NOx emission standard of less 

than or equal to 0.50 g/bhp-hr NOx; and 

c. 2.0 times any of the applicable NMHC or CO standards, the 

applicable NOx standard by more than 0.2 g/bhp-hr (e.g., cause 

NOx emissions to exceed 0.4 g/bhp-hr if the emission standard is 

0.2 g/bhp-hr) as measured from an applicable cycle emission test, 

or 0.03 g/bhp-hr PM as measured from an applicable cycle 

emission test for 2013 and subsequent model year vehicles 

certified to an engine dynamometer tailpipe NOx emission standard 

of less than or equal to 0.50 g/bhp-hr NOx; 

(B) For vehicles in which no failure or deterioration of the fuel system 

pressure control could result in a vehicle’s emissions exceeding the 

applicable malfunction criteria specified in section (f)(4.2.1)(A), the OBD II 
73

system shall detect a malfunction when the system has reached its control 

limits such that the commanded fuel system pressure cannot be delivered. 

(4.2.2) Injection quantity. Additionally, for all 2010 and subsequent model year 

vehicles, the fuel system shall be monitored for injection quantity: 

(A) The OBD II system shall detect a malfunction of the fuel injection system 

when the system is unable to deliver the commanded quantity of fuel 

necessary to maintain a vehicle’s NMHC, CO, NOx and PM emissions at 

or below: 

(i) For passenger cars, light-duty trucks, and MDPVs certified to a chassis 

dynamometer tailpipe emission standard: 

a. 3.0 times the applicable FTP standards for 2010 through 2012 

model year vehicles; and 

b. 1.5 times the applicable FTP NMHC, CO, or NOx standards or 2.0 

times the applicable FTP PM standard for 2013 and subsequent 

model year vehicles. 

(ii) For medium-duty vehicles (including MDPVs) certified to an engine 

dynamometer tailpipe emission standard, the applicable emission 

levels specified in sections (f)(4.2.1)(A)(ii). 

(B) For vehicles in which no failure or deterioration of the fuel injection 

quantity could result in a vehicle’s emissions exceeding the applicable 

malfunction criteria specified in section (f)(4.2.2)(A), the OBD II system 

shall detect a malfunction when the system has reached its control limits 

such that the commanded fuel quantity cannot be delivered. 

(4.2.3) Injection Timing. Additionally, for all 2010 and subsequent model year 

vehicles, the fuel system shall be monitored for injection timing: 

(A) The OBD II system shall detect a malfunction of the fuel injection system 

when the system is unable to deliver fuel at the proper crank angle/timing 

(e.g., injection timing too advanced or too retarded) necessary to maintain 

a vehicle’s NMHC, CO, NOx, and PM emissions at or below the applicable 

emission levels specified in sections (f)(4.2.2)(A). 

(B) For vehicles in which no failure or deterioration of the fuel injection timing 

could result in a vehicle’s emissions exceeding the applicable malfunction 

criteria specified in section (f)(4.2.3)(A), the OBD II system shall detect a 

malfunction when the system has reached its control limits such that the 

commanded fuel injection timing cannot be achieved.

(4.2.4) Feedback control: 

(A) Except as provided for in section (f)(4.2.4)(B), if the vehicle is equipped 

with feedback or feed-forward control of the fuel system (e.g., feedback 

control of pressure or pilot injection quantity), the OBD II system shall 

detect a malfunction: 

(i) If the system fails to begin feedback control within a manufacturer 

specified time interval; 

(ii) If a failure or deterioration causes open loop or default operation; or 

(iii) If feedback control system has used up all of the adjustment allowed 

by the manufacturer or reached its maximum authority and cannot 

achieve the feedback target. 

(B) A manufacturer may request Executive Officer approval to temporarily 

disable monitoring for the malfunction criteria specified in section 
74

(f)(4.2.4)(A)(iii) during conditions that a manufacturer cannot robustly 

distinguish between a malfunctioning system and a properly operating 

system. The Executive Officer shall approve the disablement upon the 

manufacturer submitting data and/or analysis demonstrating that the 

control system, when operating as designed on a vehicle with all emission 

controls working properly, routinely operates during these conditions with 

all of the adjustment allowed by the manufacturer used up. 

(C) In lieu of detecting the malfunctions specified in sections (f)(4.2.4)(A)(i) 

and (ii) with a fuel system-specific monitor, the OBD II system may 

monitor the individual parameters or components that are used as inputs 

for fuel system feedback control provided that the monitors detect all 

malfunctions that meet the criteria in sections (f)(4.2.4)(A)(i) and (ii). 

(4.2.5) For purposes of determining the fuel system malfunction criteria in 

sections (e)(4.2.1) through (4.2.3) for medium-duty vehicles (including 

MDPVs) certified to an engine dynamometer tailpipe emission standard, 

the manufacturer shall do the following:

(A) For 2004 through 2012 model year vehicles, the malfunction criteria shall 

be established by using a fault that affects either a single injector or all 

injectors equally.

(B) For 2013 and subsequent model year vehicles, for section (e)(4.2.1), the 

malfunction criteria shall be established by using a fault that affects all 

injectors equally. Additionally, for systems that have single component 

failures which could affect a single injector (e.g., systems that build 

injection pressure within the injector that could have a single component 

pressure fault caused by the injector itself), the malfunction criteria shall 

also be established by using a fault that affects a single injector.

(C) For 2013 and subsequent model year vehicles, for sections (e)(4.2.2) 

through (4.2.3), the malfunction criteria shall be established by both (1) a 

fault that affects all the injectors equally and (2) a fault that affects only 

one injector.

(4.3) Monitoring Conditions: 

(4.3.1) Except as provided in sections (e)(4.3.2) and (e)(4.3.4), Tthe OBD II 

system shall monitor continuously for malfunctions identified in sections 

(f)(4.2.1) and (f)(4.2.4) (i.e., fuel pressure control and feedback operation). 

(4.3.2) For fuel systems that achieve injection fuel pressure within the injector or 

increase pressure within the injector (e.g. in the injector of an amplified 

common rail system), manufacturers may request Executive Officer

approval to define the monitoring conditions for malfunctions identified in 

sections (e)(4.2.1) in accordance with sections (d)(3.1) and (d)(3.2) (i.e., 

minimum ratio requirements). The Executive Officer shall approve the 

monitoring conditions upon the manufacturer submitting data and/or 

analysis identifying all possible failure modes and the effect each has 

(e.g., failure modes and effects analysis) on fuel pressure across the 

entire range of engine operating conditions, and upon the Executive 

Officer determining based on the data and/or analysis that the monitoring 

conditions allow for robust detection of all causes of fuel pressure 

malfunctions.
75

(4.3.2)(4.3.3) Manufacturers shall define the monitoring conditions for 

malfunctions identified in sections (f)(4.2.2) and (f)(4.2.3) (i.e., injection 

quantity and timing) in accordance with sections (d)(3.1) and (d)(3.2) (i.e., 

minimum ratio requirements). For all 2013 and subsequent model year 

vehicles, for purposes of tracking and reporting as required in section 

(d)(3.2.2), all monitors used to detect malfunctions identified in sections 

(f)(4.2.2) and (f)(4.2.3) shall be tracked separately but reported as a single 

set of values as specified in section (d)(5.2.2).

(4.3.4) Manufacturers may request Executive Officer approval to temporarily 

disable continuous monitoring under conditions technically necessary to 

ensure robust detection of malfunctions and to avoid false passes and 

false indications of malfunctions. The Executive Officer shall approve the 

request upon determining that the manufacturer has submitted data 

and/or an engineering evaluation which demonstrate that a properly 

operating system cannot be distinguished from a malfunctioning system 

and that the disablement interval is limited only to that which is technically 

necessary.

(4.4) MIL Illumination and Fault Code Storage: 

(4.4.1) General requirements for MIL illumination and fault code storage are set 

forth in section (d)(2). 

(4.4.2) Additionally, for malfunctions identified in section (f)(4.2.1) (i.e., fuel 

pressure control) on all 2010 and subsequent model year vehicles: 

(A) A pending fault code shall be stored immediately upon the fuel system 

exceeding the malfunction criteria established pursuant to section 

(f)(4.2.1). 

(B) Except as provided below, if a pending fault code is stored, the OBD II 

system shall immediately illuminate the MIL and store a confirmed fault 

code if a malfunction is again detected during either of the following two 

events: (a) the driving cycle immediately following the storage of the 

pending fault code, regardless of the conditions encountered during the 

driving cycle; or (b) on the next driving cycle in which similar conditions 

(see section (c)) to those that occurred when the pending fault code was 

stored are encountered. 

(C) The pending fault code may be erased at the end of the next driving cycle 

in which similar conditions have been encountered without an exceedance 

of the specified fuel system malfunction criteria. The pending code may 

also be erased if similar conditions are not encountered during the 80 

driving cycles immediately after the initial detection of a malfunction for 

which the pending code was set. 

(D) Storage of freeze frame conditions. 

(i) A manufacturer shall store and erase freeze frame conditions either in 

conjunction with storing and erasing a pending fault code or in 

conjunction with storing and erasing a confirmed fault code. 

(ii) If freeze frame conditions are stored for a malfunction other than 

misfire (see section (f)(3)) or fuel system malfunction when a fault 

code is stored as specified in section (f)(4.4.2) above, the stored 

freeze frame information shall be replaced with freeze frame 

information regarding the fuel system malfunction. 
76

(E) Storage of fuel system conditions for determining similar conditions of 

operation. 

(i) Upon detection of a fuel system malfunction under section (f)(4.4.2), 

the OBD II system shall store the engine speed, load, and warm-up 

status of the first fuel system malfunction that resulted in the storage of 

the pending fault code.

(ii) The manufacturer may request Executive Officer approval to use an 

alternate definition of similar conditions in lieu of the definition 

specified in section (c). The Executive Officer shall approve the 

alternate definition upon the manufacturer providing data or analysis 

demonstrating that the alternate definition provides for equivalent 

robustness in detection of fuel system faults that vary in severity 

depending on engine speed, load, and/or warm-up status.

(F) Extinguishing the MIL. The MIL may be extinguished after three 

sequential driving cycles in which similar conditions have been 

encountered without a malfunction of the fuel system. 

(5) EXHAUST GAS SENSOR MONITORING 

(5.1) Requirement: 

(5.1.1) The OBD II system shall monitor all exhaust gas sensors (e.g., oxygen, 

air-fuel ratio, NOx) used for emission control system feedback (e.g., EGR 

control/feedback, SCR control/feedback, NOx adsorber control/feedback)

or as a monitoring device for proper output signal, activity, response rate, 

and any other parameter that can affect emissions. 

(5.1.2) For vehicles equipped with heated exhaust gas sensors, the OBD II 

system shall monitor the heater for proper performance. 

(5.2) Malfunction Criteria: 

(5.2.1) Air-Fuel Ratio Sensors: 

(A) For sensors located upstream of the exhaust aftertreatment: 

(i) Sensor performance faults: The OBD II system shall detect a 

malfunction prior to any failure or deterioration of the sensor voltage, 

resistance, impedance, current, response rate, amplitude, offset, or 

other characteristic(s) that would cause a vehicle’s NMHC, CO, NOx, 

or PM emissions to exceed: 

a. For passenger cars, light-duty trucks, and MDPVs certified to a 

chassis dynamometer tailpipe emission standard: 

1. 2.5 times the applicable FTP standards for 2004 through 2009 

model year vehicles; 

2. 2.0 times the applicable FTP standards for 2010 through 2012 

model year vehicles; and 

3. 1.5 times the applicable FTP NMHC, CO, or NOx standards or 

2.0 times the applicable FTP PM standard for 2013 and 

subsequent model year vehicles. 

b. For medium-duty vehicles (including MDPVs) certified to an engine 

dynamometer tailpipe emission standard: 

1. 1.5 times the applicable NMHC, CO, and NOx standards or 0.03 

g/bhp-hr PM as measured from an applicable cycle emission 

test for 2007 and subsequent model year vehicles certified to an 
77

engine dynamometer tailpipe NOx emission standard of greater 

than 0.50 g/bhp-hr NOx; 

2. 2.5 times the applicable NMHC or CO standards, the applicable 

NOx standard by more than 0.3 g/bhp-hr (e.g., cause NOx 

emissions to exceed 0.5 g/bhp-hr if the emission standard is 0.2 

g/bhp-hr) as measured from an applicable cycle emission test, 

or 0.03 g/bhp-hr PM as measured from an applicable cycle 

emission test for 2007 through 2012 model year vehicles 

certified to an engine dynamometer tailpipe NOx emission 

standard of less than or equal to 0.50 g/bhp-hr NOx; and 

3. 2.0 times the applicable NMHC or CO standards, the applicable 

NOx standard by more than 0.2 g/bhp-hr (e.g., cause NOx 

emissions to exceed 0.4 g/bhp-hr if the emission standard is 0.2 

g/bhp-hr) as measured from an applicable cycle emission test, 

or 0.03 g/bhp-hr PM as measured from an applicable cycle 

emission test for 2013 and subsequent model year vehicles 

certified to an engine dynamometer tailpipe NOx emission 

standard of less than or equal to 0.50 g/bhp-hr NOx. 

(ii) Circuit faults: The OBD II system shall detect malfunctions of the 

sensor caused by either a lack of circuit continuity or out-of-range 

values. 

(iii) Feedback faults: The OBD II system shall detect a malfunction of the 

sensor when a sensor failure or deterioration causes an emission 

control system (e.g., EGR, SCR, or NOx adsorber) to stop using that 

sensor as a feedback or feed-forward input (e.g., causes default or 

open-loop operation). 

(iv) Monitoring capability: To the extent feasible, the OBD II system shall 

detect a malfunction of the sensor when the sensor output voltage, 

resistance, impedance, current, amplitude, activity, offset, or other 

characteristics are no longer sufficient for use as an OBD II system 

monitoring device (e.g., for catalyst, EGR, SCR, or NOx adsorber 

monitoring). 

(B) For sensors located downstream of the exhaust aftertreatment: 

(i) Sensor performance faults: The OBD II system shall detect a 

malfunction prior to any failure or deterioration of the sensor voltage, 

resistance, impedance, current, response rate, amplitude, offset, or 

other characteristic(s) that would cause a vehicle’s NMHC, CO, NOx, 

or PM emissions to exceed: 

a. For passenger cars, light-duty trucks, and MDPVs certified to a 

chassis dynamometer tailpipe emission standard: 

1. 3.5 times the applicable FTP NMHC, CO, or NOx standards or 

5.0 times the applicable FTP PM standard for 2004 through 

2009 model year vehicles; 

2. 2.5 times the applicable FTP NMHC, CO, or NOx standards or 

4.0 times the applicable FTP PM standard for 2010 through 

2012 model year vehicles; 

3. 1.5 times the applicable FTP NMHC or CO standards, 1.75 times 

the applicable FTP NOx standard, or 2.0 times the applicable 
78

FTP PM standard for 2013 and subsequent model year 

vehicles. 

b. For medium-duty vehicles (including MDPVs) certified to an engine 

dynamometer tailpipe emission standard: 

1. 2.5 times the applicable NMHC or CO standards, the applicable 

NOx standard by more than 0.5 g/bhp-hr (e.g., cause NOx 

emissions to exceed 0.7 g/bhp-hr if the emission standard is 0.2 

g/bhp-hr) as measured from an applicable cycle emission test, 

or 0.05 g/bhp-hr PM as measured from an applicable cycle 

emission test for 2007 through 2009 model year vehicles 

certified to an engine dynamometer tailpipe NOx emission 

standard of greater than 0.50 g/bhp-hr NOx; 

2. 2.5 times the applicable NMHC or CO standards, the applicable 

NOx standard by more than 0.3 g/bhp-hr (e.g., cause NOx 

emissions to exceed 0.5 g/bhp-hr if the emission standard is 0.2 

g/bhp-hr) as measured from an applicable cycle emission test, 

or 0.05 g/bhp-hr PM as measured from an applicable cycle 

emission test for 2007 through 2012 model year vehicles 

certified to an engine dynamometer tailpipe NOx emission 

standard of less than or equal to 0.50 g/bhp-hr NOx; and 

3. 2.0 times the applicable NMHC or CO standards, the applicable 

NOx standard by more than 0.2 g/bhp-hr (e.g., cause NOx 

emissions to exceed 0.4 g/bhp-hr if the emission standard is 0.2 

g/bhp-hr) as measured from an applicable cycle emission test, 

or 0.03 g/bhp-hr PM as measured from an applicable cycle 

emission test for 2013 and subsequent model year vehicles 

certified to an engine dynamometer tailpipe NOx emission 

standard of less than or equal to 0.50 g/bhp-hr NOx. 

(ii) Circuit faults: The OBD II system shall detect malfunctions of the 

sensor caused by either a lack of circuit continuity or out-of-range 

values. 

(iii) Feedback faults: The OBD II system shall detect a malfunction of the 

sensor when a sensor failure or deterioration causes an emission 

control system (e.g., EGR, SCR, or NOx adsorber) to stop using that 

sensor as a feedback or feed-forward input (e.g., causes default or 

open-loop operation). 

(iv) Monitoring capability: To the extent feasible, the OBD II system shall 

detect a malfunction of the sensor when the sensor output voltage, 

resistance, impedance, current, amplitude, activity, offset, or other 

characteristics are no longer sufficient for use as an OBD II system 

monitoring device (e.g., for catalyst, EGR, SCR, or NOx adsorber 

monitoring). 

(5.2.2) NOx and PM sensors: 

(A) Sensor performance faults: The OBD II system shall detect a malfunction 

prior to any failure or deterioration of the sensor voltage, resistance, 

impedance, current, response rate, amplitude, offset, or other 

characteristic(s) that would cause a vehicle’s emissions to exceed: 
79

(i) For passenger cars, light-duty trucks, and MDPVs certified to a chassis 

dynamometer tailpipe emission standard: 

1. 3.5 times the applicable FTP NMHC, CO, or NOx standards or 

5.0 times the applicable FTP PM standard for 2004 through 

2009 model year vehicles; 

2. 2.5 times the applicable FTP NMHC, CO, or NOx standards, or 

4.0 times the applicable FTP PM standard for 2010 through 

2012 model year vehicles; 

3. 1.5 times the applicable FTP NMHC or CO standards, 1.75 times 

the applicable FTP NOx standard, or 2.0 times the applicable 

FTP PM standard for 2013 and subsequent model year 

vehicles. 

(ii) For medium-duty vehicles (including MDPVs) certified to an engine 

dynamometer tailpipe emission standard: 

a. 2.5 times the applicable NMHC standards, the applicable NOx 

standard by more than 0.5 g/bhp-hr (e.g., cause NOx emissions to 

exceed 0.7 g/bhp-hr if the emission standard is 0.2 g/bhp-hr) as 

measured from an applicable cycle emission test or 0.05 g/bhp-hr 

PM as measured from an applicable cycle emission test for 2007 

through 2009 model year vehicles; 

b. 2.5 times the applicable NMHC standards, the applicable NOx 

standard by more than 0.34 g/bhp-hr (e.g., cause NOx emissions to 

exceed 0.56 g/bhp-hr if the emission standard is 0.2 g/bhp-hr) as 

measured from an applicable cycle emission test or 0.05 g/bhp-hr 

PM as measured from an applicable cycle emission test for 2010 

through 2012 model year vehicles; and 

c. 2.0 times the applicable NMHC standards, the applicable NOx 

standard by more than 0.2 g/bhp-hr (e.g., cause NOx emissions to 

exceed 0.4 g/bhp-hr if the emission standard is 0.2 g/bhp-hr) as 

measured from an applicable cycle emission test or 0.03 g/bhp-hr 

PM as measured from an applicable cycle emission test for 2013 

and subsequent model year vehicles. 

(B) Circuit faults: The OBD II system shall detect malfunctions of the sensor 

caused by either a lack of circuit continuity or out-of-range values. 

(C) Feedback faults: The OBD II system shall detect a malfunction of the 

sensor when a sensor failure or deterioration causes an emission control 

system (e.g., EGR, SCR, or NOx adsorber) to stop using that sensor as a 

feedback or feed-forward input (e.g., causes default or open-loop 

operation). 

(D) Monitoring capability: To the extent feasible, the OBD II system shall 

detect a malfunction of the sensor when the sensor output voltage, 

resistance, impedance, current, amplitude, activity, offset, or other 

characteristics are no longer sufficient for use as an OBD II system 

monitoring device (e.g., for catalyst, EGR, PM filter, SCR, or NOx 

adsorber monitoring). 

(5.2.3) Other exhaust gas sensors: 

(A) For other exhaust gas sensors, the manufacturer shall submit a 

monitoring plan to the Executive Officer for approval. The Executive 
80

Officer shall approve the request upon determining that the manufacturer 

has submitted data and an engineering evaluation that demonstrate that 

the monitoring plan is as reliable and effective as the monitoring plan 

required for air-fuel ratio sensors, and NOx sensors, and PM sensors

under sections (f)(5.2.1) and (f)(5.2.2). 

(5.2.4) Sensor Heaters: 

(A) The OBD II system shall detect a malfunction of the heater performance 

when the current or voltage drop in the heater circuit is no longer within 

the manufacturer's specified limits for normal operation (i.e., within the 

criteria required to be met by the component vendor for heater circuit 

performance at high mileage). Subject to Executive Officer approval, 

other malfunction criteria for heater performance malfunctions may be 

used upon the Executive Officer determining that the manufacturer has 

submitted data and/or an engineering evaluation that demonstrate the 

monitoring reliability and timeliness to be equivalent to the stated criteria 

in section (f)(5.2.4)(A). 

(B) The OBD II system shall detect malfunctions of the heater circuit including 

open or short circuits that conflict with the commanded state of the heater 

(e.g., shorted to 12 Volts when commanded to 0 Volts (ground)). 

(5.3) Monitoring Conditions: 

(5.3.1) Exhaust Gas Sensors 

(A) Manufacturers shall define the monitoring conditions for malfunctions 

identified in sections (f)(5.2.1)(A)(i), (5.2.1)(B)(i), and (5.2.2)(A) (e.g., 

sensor performance faults) in accordance with sections (d)(3.1) and 

(d)(3.2) (i.e., minimum ratio requirements). For all 2010 and subsequent 

model year vehicles, for purposes of tracking and reporting as required in 

section (d)(3.2.2), all monitors used to detect malfunctions identified in 

sections (f)(5.2.1)(A)(i), (5.2.1)(B)(i), and (5.2.2)(A) shall be tracked 

separately but reported as a single set of values as specified in section 

(d)(5.2.2). 

(B) Manufacturers shall define the monitoring conditions for malfunctions 

identified in sections (f)(5.2.1)(A)(iv), (5.2.1)(B)(iv), and (5.2.2)(D) (e.g., 

monitoring capability) in accordance with sections (d)(3.1) and (d)(3.2) 

(i.e., minimum ratio requirements) with the exception that monitoring shall 

occur every time the monitoring conditions are met during the driving cycle 

in lieu of once per driving cycle as required in section (d)(3.1.2). 

(C) Except as provided in section (f)(5.3.1)(D), monitoring for malfunctions 

identified in sections (f)(5.2.1)(A)(ii), (5.2.1)(A)(iii), (5.2.1)(B)(ii), 

(5.2.1)(B)(iii), (5.2.2)(B), and (5.2.2)(C) (i.e., circuit continuity, out-ofrange, and open-loop malfunctions) shall be conducted continuously. 

(D) A manufacturer may request Executive Officer approval to disable 

continuous exhaust gas sensor monitoring when an exhaust gas sensor 

malfunction cannot be distinguished from other effects (e.g., disable outof-range low monitoring during fuel cut conditions). The Executive Officer 

shall approve the disablement upon determining that the manufacturer 

has submitted test data and/or documentation that demonstrate a properly 

functioning sensor cannot be distinguished from a malfunctioning sensor 
81

and that the disablement interval is limited only to that necessary for 

avoiding false detection. 

(5.3.2) Sensor Heaters 

(A) Manufacturers shall define monitoring conditions for malfunctions 

identified in section (f)(5.2.4)(A) (i.e., sensor heater performance) in 

accordance with sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio 

requirements). 

(B) Monitoring for malfunctions identified in section (f)(5.2.4)(B) (i.e., circuit 

malfunctions) shall be conducted continuously. 

(5.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(6) EXHAUST GAS RECIRCULATION (EGR) SYSTEM MONITORING 

(6.1) Requirement: 

(6.1.1) The OBD II system shall monitor the EGR system on vehicles 

so-equipped for low flow rate, high flow rate, and slow response 

malfunctions. For vehicles equipped with EGR coolers (e.g., heat 

exchangers), the OBD II system shall monitor the cooler system for 

insufficient cooling malfunctions. The individual electronic components 

(e.g., actuators, valves, sensors) that are used in the EGR system shall be 

monitored in accordance with the comprehensive component 

requirements in section (f)(15).

(6.1.2) For vehicles with other charge control strategies that affect EGR flow (e.g., 

systems that modify EGR flow to achieve a desired fresh air flow rate 

instead of a desired EGR flow rate), the manufacturer shall submit a 

monitoring plan to the Executive Officer for approval. The Executive 

Officer shall approve the request upon determining that the manufacturer 

has submitted data and an engineering evaluation that demonstrate that 

the monitoring plan is as reliable and effective as the monitoring plan 

required for EGR systems under section (f)(6).

(6.2) Malfunction Criteria: 

(6.2.1) Low Flow: 

(A) The OBD II system shall detect a malfunction of the EGR system at or 

prior to a decrease from the manufacturer's specified EGR flow rate that 

would cause a vehicle’s NMHC, CO, NOx, or PM emissions to exceed: 

(i) For passenger cars, light-duty trucks, and MDPVs certified to a chassis 

dynamometer tailpipe emission standard: 

a. 3.0 times the applicable FTP standards for 2004 through 2009 

model year vehicles; 

b. 2.5 times the applicable FTP standards for 2010 through 2012 

model year vehicles; and 

c. 1.5 times the applicable FTP NMHC, CO, or NOx standards or 2.0 

times the applicable FTP PM standard for 2013 and subsequent 

model year vehicles. 

(ii) For medium-duty vehicles (including MDPVs) certified to an engine 

dynamometer tailpipe emission standard: 
82

a. 1.5 times the applicable FTP standards for 2004 through 2006 

model year vehicles; 

b. 1.5 times the applicable NMHC, CO, and NOx standards or 0.03 

g/bhp-hr PM as measured from an applicable cycle emission test 

for 2007 and subsequent model year vehicles certified to an engine 

dynamometer tailpipe NOx emission standard of greater than 0.50 

g/bhp-hr NOx; 

c. 2.5 times the applicable NMHC or CO standards, the applicable 

NOx standard by more than 0.3 g/bhp-hr (e.g., cause NOx 

emissions to exceed 0.5 g/bhp-hr if the emission standard is 0.2 

g/bhp-hr) as measured from an applicable cycle emission test, or 

0.03 g/bhp-hr PM as measured from an applicable cycle emission 

test for 2007 through 2012 model year vehicles certified to an 

engine dynamometer tailpipe NOx emission standard of less than 

or equal to 0.50 g/bhp-hr NOx; and 

d. 2.0 times the applicable NMHC or CO standards, the applicable 

NOx standard by more than 0.2 g/bhp-hr (e.g., cause NOx 

emissions to exceed 0.4 g/bhp-hr if the emission standard is 0.2 

g/bhp-hr) as measured from an applicable cycle emission test, or 

0.03 g/bhp-hr PM as measured from an applicable cycle emission 

test for 2013 and subsequent model year vehicles certified to an 

engine dynamometer tailpipe NOx emission standard of less than 

or equal to 0.50 g/bhp-hr NOx. 

(B) For vehicles in which no failure or deterioration of the EGR system that 

causes a decrease in flow could result in a vehicle’s emissions exceeding 

the malfunction criteria specified in section (f)(6.2.1)(A), the OBD II 

system shall detect a malfunction when either the EGR system has 

reached its control limits such that it cannot increase EGR flow to achieve 

the commanded flow rate or, for non-feedback controlled EGR systems, 

the EGR system has no detectable amount of EGR flow when EGR flow is 

expected. 

(6.2.2) High Flow: 

(A) The OBD II system shall detect a malfunction of the EGR system, 

including a leaking EGR valve (i.e., exhaust gas flowing through the valve 

when the valve is commanded closed), at or prior to an increase from the 

manufacturer's specified EGR flow rate that would cause a vehicle’s 

NMHC, CO, NOx, or PM emissions to exceed the applicable emission 

levels specified in sections (f)(6.2.1)(A): 

(B) For vehicles in which no failure or deterioration of the EGR system that 

causes an increase in flow could result in a vehicle’s emissions exceeding 

the malfunction criteria specified in section (f)(6.2.2)(A), the OBD II 

system shall detect a malfunction when either the EGR system has 

reached its control limits such that it cannot reduce EGR flow to achieve 

the commanded flow rate or, for non-feedback controlled EGR systems, 

the EGR system has maximum detectable EGR flow when little or no 

EGR flow is expected. 

(6.2.3) Slow Response. Additionally, for 2010 and subsequent model year 

vehicles, the EGR system shall be monitored for slow response: 
83

(A) The OBD II system shall detect a malfunction of the EGR system at or 

prior to any failure or deterioration in the capability of the EGR system 

response (e.g., capability to achieve the commanded specified flow rate 

within a manufacturer-specified time) that would cause a vehicle’s NMHC, 

CO, NOx, or PM emissions to exceed the applicable emission levels 

specified in sections (f)(6.2.1)(A). 

(B) The OBD II system shall monitor the capability of the EGR system 

response under both increasing and decreasing EGR flow ratesto respond 

to both a commanded increase in flow and a commanded decrease in 

flow. For vehicles in which no failure or deterioration of the EGR system 

response could result in an engine’s emissions exceeding the levels

specified in section (f)(6.2.1)(A), the OBD II system shall detect a 

malfunction of the EGR system when no detectable response to a change 

in commanded or expected flow rate occurs

(6.2.4) Feedback control: 

(A) Except as provided for in section (f)(6.2.4)(B), if the vehicle is equipped 

with feedback or feed-forward control of the EGR system (e.g., feedback 

control of flow, valve position, pressure differential across the valve via 

intake throttle or exhaust backpressure), the OBD II system shall detect a 

malfunction: 

(i) If the system fails to begin feedback control within a manufacturer 

specified time interval; 

(ii) If a failure or deterioration causes open loop or default operation; or 

(iii) If feedback the control system has used up all of the adjustment 

allowed by the manufacturer or reached its maximum authority and 

cannot achieve the feedback target. 

(B) A manufacturer may request Executive Officer approval to temporarily 

disable monitoring for the malfunction criteria specified in section 

(f)(6.2.4)(A)(iii) during conditions that a manufacturer cannot robustly 

distinguish between a malfunctioning system and a properly operating 

system. The Executive Officer shall approve the disablement upon the 

manufacturer submitting data and/or analysis demonstrating that the 

control system, when operating as designed on a vehicle with all emission 

controls working properly, routinely operates during these conditions with 

all of the adjustment allowed by the manufacturer used up. 

(C) In lieu of detecting the malfunctions specified in sections (f)(6.2.4)(A)(i) 

and (ii) with an EGR system-specific monitor, the OBD II system may 

monitor the individual parameters or components that are used as inputs 

for EGR system feedback control provided that the monitors detect all 

malfunctions that meet the criteria in sections (f)(6.2.4)(A)(i) and (ii). 

(6.2.5) EGR Cooler Performance: 

(A) The OBD II system shall detect a malfunction of the EGR cooler system 

cooler at or prior to a reduction from the manufacturer's specified cooling 

performance that would cause a vehicle’s NMHC, CO, NOx, or PM 

emissions to exceed the applicable emission levels specified in sections 

(f)(6.2.1)(A): 

(B) For vehicles in which no failure or deterioration of the EGR cooler system 

cooler could result in a vehicle’s emissions exceeding the malfunction 
84

criteria specified in section (f)(6.2.5)(A), the OBD II system shall detect a 

malfunction when the system has no detectable amount of EGR cooling. 

(C) For purposes of determining the EGR cooler performance malfunction 

criteria in section (f)(6.2.5)(A) for EGR cooler systems that consist of more 

than one cooler (e.g., a pre-cooler and a main cooler, two or more coolers 

in series), the manufacturer shall submit an EGR cooler system aging and 

monitoring plan to the Executive Officer for review and approval. The plan 

shall include the description and location of each component, the 

monitoring strategy for each component and combination of components, 

and the method for determining the malfunction criteria of section 

(e)(3.2.5)(A) including the deterioration/aging process. Executive Officer 

approval of the plan shall be based on the representativeness of the aging 

to real world EGR cooler system component deterioration under normal 

and malfunctioning engine operating conditions and the effectiveness of 

the method used to determine the malfunction criteria of section 

(e)(3.2.5)(A).

(6.2.6) EGR Catalyst Performance: For catalysts located in the EGR system on 

2013 and subsequent model year vehicles and used to convert 

constituents to reduce emissions or protect or extend the durability of 

other emission-related components (e.g., to reduce fouling of an EGR 

cooler or valve), the OBD II system shall detect a malfunction when the 

catalyst has no detectable amount of constituent (e.g., hydrocarbons, 

soluble organic fractions) oxidation. For 2004 through 2012 model year 

vehicles, the catalyst shall be monitored in accordance with the other 

emission control or source system monitoring requirements under section 

(f)(16).

(6.3) Monitoring Conditions: 

(6.3.1) For malfunctions identified in sections (f)(6.2.1) and (f)(6.2.2) (i.e., EGR 

low and high flow) manufacturers shall, manufacturers shall define 

monitoring conditions: 

(A) For 2004 through 2009 model year vehicles, Define monitoring conditions 

in accordance with sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio 

requirements) for 2004 through 2009 model year vehicles. For purposes 

of tracking and reporting as required in section (d)(3.2.2), all monitors 

used to detect malfunctions identified in sections (f)(6.2.1) and (f)(6.2.2) 

shall be tracked separately but reported as a single set of values as 

specified in section (d)(5.2.2); 

(B) Except as provided in section (e)(6.3.5), ensure that monitoring is 

Cconducted continuously for all 2010 and subsequent model year 

vehicles. 

(6.3.2) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (f)(6.2.3) (i.e., slow response) in accordance with 

sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements), with the 

exception that monitoring shall occur every time the monitoring conditions 

are met during the driving cycle in lieu of once per driving cycle as 

required in section (d)(3.1.2). For purposes of tracking and reporting as 

required in section (d)(3.2.2), all monitors used to detect malfunctions 
85

identified in section (f)(6.2.3) shall be tracked separately but reported as a 

single set of values as specified in section (d)(5.2.2). 

(6.3.3) The OBD II system shall monitor continuously for malfunctions identified in 

section (f)(6.2.4) (i.e., EGR feedback control). 

(6.3.4) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (f)(6.2.5) and (f)(6.2.6) (i.e., cooler performance and 

EGR catalyst performance) in accordance with sections (d)(3.1) and 

(d)(3.2) (i.e., minimum ratio requirements). For purposes of tracking and 

reporting as required in section (d)(3.2.2), all monitors used to detect 

malfunctions identified in section (f)(6.2.5) shall be tracked separately but 

reported as a single set of values as specified in section (d)(5.2.2). 

(6.3.5) Manufacturers may request Executive Officer approval to temporarily 

disable the EGR system checkcontinuous monitoring under specific 

conditions technically necessary to ensure robust detection of

malfunctions and to avoid false passes and false indications of 

malfunctions (e.g., disable EGR low flow monitoring when no or very little 

flow is commanded, disable EGR high and low flow monitoring when 

freezing may affect performance of the system). The Executive Officer 

shall approve the request upon determining that the manufacturer has 

submitted data and/or an engineering evaluation which demonstrate that a 

properly operating EGR system cannot be distinguished from a 

malfunctioning EGR system and that the disablement interval is limited 

only to that which is technically necessaryreliable check cannot be made 

when these conditions exist. 

(6.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(7) BOOST PRESSURE CONTROL SYSTEM MONITORING 

(7.1) Requirement: 

(7.1.1) For 2010 and subsequent model year vehicles, the OBD II system shall 

monitor the boost pressure control system (e.g., turbocharger) on vehicles 

so-equipped for under and over boost malfunctions and slow response 

malfunctions. For vehicles equipped with variable geometry 

turbochargers (VGT), the OBD II system shall monitor the VGT system for 

slow response malfunctions. For vehicles equipped with charge air cooler 

systems, the OBD II system shall monitor the charge air cooler system for 

cooling system performance malfunctions. For 2004 and subsequent 

model year vehicles, the individual electronic components (e.g., actuators, 

valves, sensors) that are used in the boost pressure control system shall 

be monitored in accordance with the comprehensive component 

requirements in section (f)(15).

(7.1.2) For vehicles with other charge control strategies that affect boost pressure 

(e.g., systems that modify boost pressure to achieve a desired air-fuel 

ratio instead of a desired boost pressure), the manufacturer shall submit a 

monitoring plan to the Executive Officer for approval. The Executive 

Officer shall approve the request upon determining that the manufacturer 

has submitted data and an engineering evaluation that demonstrate that 
86

the monitoring plan is as reliable and effective as the monitoring plan 

required for boost pressure control systems under section (f)(7).

(7.2) Malfunction Criteria: 

(7.2.1) Underboost: 

(A) The OBD II system shall detect a malfunction of the boost pressure 

control system at or prior to a decrease from the manufacturer's 

commanded or expected boost pressure that would cause a vehicle’s 

NMHC, CO, NOx, or PM emissions to exceed: 

(i) For passenger cars, light-duty trucks, and MDPVs certified to a chassis 

dynamometer tailpipe emission standard: 

a. 2.0 times the applicable FTP standards for 2010 through 2012 

model year vehicles; and 

b. 1.5 times the applicable FTP NMHC, CO, or NOx standards or 2.0 

times the applicable FTP PM standard for 2013 and subsequent 

model year vehicles. 

(ii) For medium-duty vehicles (including MDPVs) certified to an engine 

dynamometer tailpipe emission standard: 

a. 2.5 times the applicable NMHC or CO standards, the applicable 

NOx standard by more than 0.3 g/bhp-hr (e.g., cause NOx 

emissions to exceed 0.5 g/bhp-hr if the emission standard is 0.2 

g/bhp-hr) as measured from an applicable cycle emission test, or 

0.03 g/bhp-hr PM as measured from an applicable cycle emission 

test for 2010 through 2012 model year vehicles; and

b. 2.0 times the applicable NMHC or CO standards, the applicable 

NOx standard by more than 0.2 g/bhp-hr (e.g., cause NOx 

emissions to exceed 0.4 g/bhp-hr if the emission standard is 0.2 

g/bhp-hr) as measured from an applicable cycle emission test, or 

0.03 g/bhp-hr PM as measured from an applicable cycle emission 

test for 2013 and subsequent model year vehicles. 

(B) For vehicles in which no failure or deterioration of the boost pressure 

control system that causes a decrease in boost could result in a vehicle’s 

emissions exceeding the malfunction criteria specified in section 

(f)(7.2.1)(A), the OBD II system shall detect a malfunction when either the 

boost system has reached its control limits such that it cannot increase 

boost to achieve the commanded boost pressure or, for non-feedback 

controlled boost systems, the boost system has no detectable amount of 

boost when boost is expected. 

(7.2.2) Overboost: 

(A) The OBD II system shall detect a malfunction of the boost pressure 

control system at or prior to an increase from the manufacturer's 

commanded or expected boost pressure that would cause a vehicle's 

NMHC, CO, NOx, or PM emissions to exceed the applicable emission 

levels specified in sections (f)(7.2.1)(A). 

(B) For vehicles in which no failure or deterioration of the boost pressure 

control system that causes an increase in boost could result in a vehicle’s 

emissions exceeding the malfunction criteria specified in section 

(f)(7.2.2)(A), the OBD II system shall detect a malfunction when either the 

boost system has reached its control limits such that it cannot decrease 
87

boost to achieve the commanded boost pressure or, for non-feedback 

controlled boost systems, the boost system has maximum detectable 

boost when little or no boost is expected. 

(7.2.3) VGT sSlow response: 

(A) For 2010 through 2012 model year vehicles equipped with variable 

geometry turbochargers (VGT), Tthe OBD II system shall detect a 

malfunction at or prior to any failure or deterioration in the capability of the 

VGT system to achieve the commanded turbocharger geometry within a 

manufacturer-specified time that would cause a vehicle's NMHC, CO, 

NOx, or PM emissions to exceed the applicable emission levels specified 

in sections (f)(7.2.1)(A). For vehicles in which no failure or deterioration of 

the VGT system response could result in a vehicle’s emissions exceeding 

these levels, the OBD II system shall detect a malfunction of the VGT 

system when proper functional response of the system to computer 

commands does not occur.

(B) For 2013 and subsequent model year vehicles, the OBD II system shall 

detect a malfunction prior to any failure or deterioration in the boost 

pressure control system response (e.g., capability to achieve the 

commanded or expected boost pressure within a manufacturer-specified 

time) that would cause vehicle's NMHC, CO, NOx, or PM emissions to 

exceed the applicable emission levels specified in section (f)(7.2.1)(A). 

For vehicles in which no failure or deterioration of the boost system 

response could result in an engine’s emissions exceeding these levels, 

the OBD II system shall detect a malfunction of the boost system when no 

detectable response to a commanded or expected change in boost 

pressure occurs.For vehicles in which no failure or deterioration of the 

VGT system response could result in a vehicle’s emissions exceeding the 

malfunction criteria specified in section (f)(7.2.3)(A), the OBD II system 

shall detect a malfunction of the VGT system when proper functional 

response of the system to computer commands does not occur. 

(7.2.4) Charge Air Undercooling: 

(A) The OBD II system shall detect a malfunction of the charge air cooling 

system at or prior to a decrease from the manufacturer's specified cooling 

rate that would cause a vehicle’s NMHC, CO, NOx, or PM emissions to 

exceed the applicable emission levels specified in sections (f)(7.2.1)(A). 

(B) For vehicles in which no failure or deterioration of the charge air cooling 

system that causes a decrease in cooling performance could result in a 

vehicle’s emissions exceeding the malfunction criteria specified in section 

(f)(7.2.4)(A), the OBD II system shall detect a malfunction when the 

system has no detectable amount of charge air cooling. 

(C) For purposes of determining the charge air cooling performance 

malfunction criteria in section (f)(7.2.4)(A) for charge air cooling systems 

that consist of more than one cooler (e.g., a pre-cooler and a main cooler, 

two or more coolers in series), the manufacturer shall submit a charge air 

cooling system aging and monitoring plan to the Executive Officer for 

review and approval. The plan shall include the description and location 

of each component, the monitoring strategy for each component and 

combination of components, and the method for determining the 
88

malfunction criteria of section (f)(7.2.4)(A) including the deterioration/aging 

process. Executive Officer approval of the plan shall be based on the 

representativeness of the aging to real world charge air cooling system 

component deterioration under normal and malfunctioning engine 

operating conditions and the effectiveness of the method used to 

determine the malfunction criteria of section (f)(7.2.4)(A).

(7.2.5) Feedback control: 

(A) Except as provided for in section (f)(7.2.5)(B), if the vehicle is equipped 

with feedback or feed-forward control of the boost pressure system (e.g., 

control of VGT position, turbine speed, manifold pressure) the OBD II 

system shall detect a malfunction: 

(i) If the system fails to begin feedback control within a manufacturer 

specified time interval; 

(ii) If a failure or deterioration causes open loop or default operation; or 

(iii) If feedback the control system has used up all of the adjustment 

allowed by the manufacturer or reached its maximum authority and 

cannot achieve the feedback target. 

(B) A manufacturer may request Executive Officer approval to temporarily 

disable monitoring for the malfunction criteria specified in section 

(f)(7.2.5)(A)(iii) during conditions that a manufacturer cannot robustly 

distinguish between a malfunctioning system and a properly operating 

system. The Executive Officer shall approve the disablement upon the 

manufacturer submitting data and/or analysis demonstrating that the 

control system, when operating as designed on a vehicle with all emission 

controls working properly, routinely operates during these conditions with 

all of the adjustment allowed by the manufacturer used up. 

(C) In lieu of detecting the malfunctions specified in sections (f)(7.2.5)(A)(i) 

and (ii) with a boost pressure system-specific monitor, the OBD II system 

may monitor the individual parameters or components that are used as 

inputs for boost pressure system feedback control provided that the 

monitors detect all malfunctions that meet the criteria in sections 

(f)(7.2.5)(A)(i) and (ii). 

(7.3) Monitoring Conditions: 

(7.3.1) Except as provided in section (e)(7.3.4), Tthe OBD II system shall monitor 

continuously for malfunctions identified in sections (f)(7.2.1), (7.2.2), and 

(7.2.5) (i.e., over and under boost, feedback control). 

(7.3.2) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (f)(7.2.3) (i.e., VGT slow response) in accordance with 

sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements), with the 

exception that monitoring shall occur every time the monitoring conditions 

are met during the driving cycle in lieu of once per driving cycle as 

required in section (d)(3.1.2). For all 2010 and subsequent model year 

vehicles, for purposes of tracking and reporting as required in section 

(d)(3.2.2), all monitors used to detect malfunctions identified in section 

(f)(7.2.3) shall be tracked separately but reported as a single set of values 

as specified in section (d)(5.2.2). 

(7.3.3) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (f)(7.2.4) (i.e., charge air cooler performance) in 
89

accordance with sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio 

requirements). For purposes of tracking and reporting as required in 

section (d)(3.2.2), all monitors used to detect malfunctions identified in 

section (f)(7.2.4) shall be tracked separately but reported as a single set 

of values as specified in section (d)(5.2.2). 

(7.3.4) Manufacturers may request Executive Officer approval to temporarily 

disable continuous monitoring under conditions technically necessary to 

ensure robust detection of malfunctions and to avoid false passes and 

false indications of malfunctions (e.g., disable monitoring of underboost 

when commanded or expected boost pressure is very low). The 

Executive Officer shall approve the request upon determining that the 

manufacturer has submitted data and/or an engineering evaluation which 

demonstrate that a properly operating system cannot be distinguished 

from a malfunctioning system and that the disablement interval is limited 

only to that technically necessary.

(7.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(8) NOx ADSORBER MONITORING 

(8.1) Requirement: The OBD II system shall monitor the NOx adsorber(s) on 

vehicles so-equipped for proper performance. For vehicles equipped with 

active/intrusive injection (e.g., in-exhaust fuel and/or air injection) to achieve 

desorption of the NOx adsorber(s), the OBD II system shall monitor the 

active/intrusive injection system for proper performance. The individual 

electronic components (e.g., injectors, valves, sensors) that are used in the 

active/intrusive injection system shall be monitored in accordance with the 

comprehensive component requirements in section (f)(15). 

(8.2) Malfunction Criteria: 

(8.2.1) NOx adsorber capability: 

(A) The OBD II system shall detect a NOx adsorber system malfunction when 

the NOx adsorber system capability decreases to the point that would 

cause a vehicle's NOx or NMHC emissions to exceed: 

(i) For passenger cars, light-duty trucks, and MDPVs certified to a chassis 

dynamometer tailpipe emission standard: 

a. 3.0 times the applicable FTP standards for 2004 through 2009 

model year vehicles; 

b. 2.5 times the applicable FTP standards for 2010 through 2012 

model year vehicles; and 

c. 1.75 times the applicable FTP standards for 2013 and subsequent 

model year vehicles. 

(ii) For medium-duty vehicles (including MDPVs) certified to an engine 

dynamometer tailpipe emission standard: 

a. the applicable NOx standard by more than 0.5 g/bhp-hr (e.g., cause 

NOx emissions to exceed 0.7 g/bhp-hr if the emission standard is 

0.2 g/bhp-hr) as measured from an applicable cycle emission test 

or 3.5 times the applicable NMHC standard for 2007 through 2009 

model year vehicles; 
90

b. the applicable NOx standard by more than 0.3 g/bhp-hr (e.g., cause 

NOx emissions to exceed 0.5 g/bhp-hr if the emission standard is 

0.2 g/bhp-hr) as measured from an applicable cycle emission test 

or 2.5 times the applicable NMHC standard for 2010 through 2012 

model year vehicles; and 

c. the applicable NOx standard by more than 0.2 g/bhp-hr (e.g., cause 

NOx emissions to exceed 0.4 g/bhp-hr if the emission standard is 

0.2 g/bhp-hr) as measured from an applicable cycle emission test 

or 2.0 times the applicable NMHC standard for 2013 and 

subsequent model year vehicles. 

(B) If no failure or deterioration of the NOx adsorber system capability could 

result in a vehicle’s NOx or NMHC emissions exceeding the applicable 

malfunction criteria specified in section (f)(8.2.1)(A), the OBD II system 

shall detect a malfunction when the system has no detectable amount of 

NOx adsorber capability. 

(8.2.2) For systems that utilize active/intrusive injection (e.g., in-cylinder post fuel 

injection, in-exhaust air-assisted fuel injection) to achieve desorption of 

the NOx adsorber, the OBD II system shall detect a malfunction if any 

failure or deterioration of the injection system’s ability to properly regulate 

injection causes the system to be unable to achieve desorption of the NOx 

adsorber. 

(8.2.3) Feedback control: 

(A) Except as provided for in section (f)(8.2.3)(B), if the vehicle is equipped 

with feedback or feed-forward control of the NOx adsorber or 

active/intrusive injection system (e.g., feedback control of injection 

quantity, time), the OBD II system shall detect a malfunction: 

(i) If the system fails to begin feedback control within a manufacturer 

specified time interval; 

(ii) If a failure or deterioration causes open loop or default operation; or 

(iii) If feedback the control system has used up all of the adjustment 

allowed by the manufacturer or reached its maximum authority and 

cannot achieve the feedback target. 

(B) A manufacturer may request Executive Officer approval to temporarily 

disable monitoring for the malfunction criteria specified in section 

(f)(8.2.3)(A)(iii) during conditions that a manufacturer cannot robustly 

distinguish between a malfunctioning system and a properly operating 

system. The Executive Officer shall approve the disablement upon the 

manufacturer submitting data and/or analysis demonstrating that the 

control system, when operating as designed on a vehicle with all emission 

controls working properly, routinely operates during these conditions with 

all of the adjustment allowed by the manufacturer used up. 

(C) In lieu of detecting the malfunctions specified in sections (f)(8.2.3)(A)(i) 

and (ii) with a NOx adsorber-specific monitor, the OBD II system may 

monitor the individual parameters or components that are used as inputs 

for NOx adsorber or active/intrusive injection system feedback control 

provided that the monitors detect all malfunctions that meet the criteria in 

sections (f)(8.2.3)(A)(i) and (ii). 
91

(8.2.4) For purposes of determining the NOx adsorber system malfunction criteria 

in section (f)(8.2.1) for NOx adsorber systems that consist of more than 

one NOx adsorber (e.g., two or more adsorbers in series), the 

manufacturer shall submit a system aging and monitoring plan to the 

Executive Officer for review and approval. The plan shall include the 

description and location of each component, the monitoring strategy for 

each component and/or combination of components, and the method for 

determining the malfunction criteria of section (f)(8.2.1) including the 

deterioration/aging process. Executive Officer approval of the plan shall 

be based on the representativeness of the aging to real world NOx 

adsorber system component deterioration under normal and 

malfunctioning engine operating conditions, the effectiveness of the 

method used to determine the malfunction criteria of section (f)(8.2.1), the 

ability of the component monitor(s) to pinpoint the likely area of 

malfunction and ensure the correct components are repaired/replaced inuse, and the ability of the component monitor(s) to accurately verify that 

each NOx adsorber system component is functioning as designed and as

required in section (f)(8.2.1).

(8.3) Monitoring Conditions: 

(8.3.1) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (f)(8.2.1) (i.e., adsorber capability) in accordance with 

sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). For 

purposes of tracking and reporting as required in section (d)(3.2.2), all 

monitors used to detect malfunctions identified in sections (f)(8.2.1) shall 

be tracked separately but reported as a single set of values as specified in 

section (d)(5.2.2). 

(8.3.2) Except as provided in section (e)(8.3.3), Tthe OBD II system shall monitor 

continuously for malfunctions identified in sections (f)(8.2.2) and (8.2.3) 

(e.g., injection function, feedback control). 

(8.3.3) Manufacturers may request Executive Officer approval to temporarily 

disable continuous monitoring under conditions technically necessary to 

ensure robust detection of malfunctions and to avoid false passes and 

false indications of malfunctions. The Executive Officer shall approve the 

request upon determining that the manufacturer has submitted data 

and/or an engineering evaluation which demonstrate that a properly 

operating system cannot be distinguished from a malfunctioning system 

and that the disablement interval is limited only to that which is technically 

necessary.

(8.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(9) PARTICULATE MATTER (PM) FILTER MONITORING 

(9.1) Requirement: The OBD II system shall monitor the PM filter on vehicles soequipped for proper performance. For vehicles equipped with active 

regeneration systems that utilize an active/intrusive injection (e.g., in-exhaust 

fuel injection, in-exhaust fuel/air burner), the OBD II system shall monitor the 

active/intrusive injection system for proper performance. The individual 

electronic components (e.g., injectors, valves, sensors) that are used in the 
92

active/intrusive injection system shall be monitored in accordance with the 

comprehensive component requirements in section (f)(15). 

(9.2) Malfunction Criteria: 

(9.2.1) Filtering Performance: 

(A) The OBD II system shall detect a malfunction prior to a decrease in the 

filtering capability of the PM filter that would cause a vehicle's PM 

emissions to exceed: 

(i) For passenger cars, light-duty trucks, and MDPVs certified to a chassis 

dynamometer tailpipe emission standard: 

a. 5.0 times the applicable FTP standard for 2004 through 2009 model 

year vehicles; 

b. 4.0 times the applicable FTP standard for 2010 through 2012 model 

year vehicles; and 

c. 1.75 times the applicable FTP standard for 2013 and subsequent 

model year vehicles. 

(ii) For medium-duty vehicles (including MDPVs) certified to an engine 

dynamometer tailpipe emission standard: 

a. 0.09 g/bhp-hr PM as measured from an applicable cycle emission 

test for 2004 through 2009 model year vehicles; 

b. 0.057 g/bhp-hr PM as measured from an applicable cycle emission 

test for 2010 through 2012 model year vehicles; and

c. 0.03 g/bhp-hr PM as measured from an applicable cycle emission 

test for 2013 and subsequent model year vehicles. 

(B) If no failure or deterioration of the PM filtering performance could result in 

a vehicle’s PM emissions exceeding the applicable malfunction criteria 

specified in section (f)(9.2.1)(A), the OBD II system shall detect a 

malfunction when no detectable amount of PM filtering occurs. 

(9.2.2) Frequent Regeneration: 

(A) For 2010 and subsequent model year vehicles, the OBD II system shall 

detect a malfunction when PM filter regeneration occurs more frequently 

than (i.e., occurs more often than) the manufacturer’s specified 

regeneration frequency such that it would cause a vehicle's emissions to 

exceed: 

(i) For passenger cars, light-duty trucks, and MDPVs certified to a chassis 

dynamometer tailpipe emission standard: 

a. 3.0 times the applicable FTP NMHC, CO, or NOx standards for 

2010 through 2012 model year vehicles; and 

b. 1.5 times the applicable FTP NMHC, CO, or NOx standards for 

2013 and subsequent model year vehicles. 

(ii) For medium-duty vehicles (including MDPVs) certified to an engine 

dynamometer tailpipe emission standard: 

a. 2.5 times the applicable NMHC standards or the applicable NOx 

standard by more than 0.3 g/bhp-hr (e.g., cause NOx emissions to 

exceed 0.5 g/bhp-hr if the emission standard is 0.2 g/bhp-hr) as 

measured from an applicable cycle emission test for 2010 through 

2012 model year vehicles; and 

b. 2.0 times the applicable NMHC standards or the applicable NOx 

standard by more than 0.2 g/bhp-hr (e.g., cause NOx emissions to 
93

exceed 0.4 g/bhp-hr if the emission standard is 0.2 g/bhp-hr) as 

measured from an applicable cycle emission test for 2013 and 

subsequent model year vehicles. 

(B) If no failure or deterioration causes an increase in the PM filter 

regeneration frequency that could result in a vehicle’s NMHC, CO, or NOx 

emissions exceeding the applicable malfunction criteria specified in 

section (f)(9.2.2)(A), the OBD II system shall detect a malfunction when 

the PM filter regeneration frequency exceeds the manufacturer’s specified 

design limits for allowable regeneration frequency.

(9.2.3) Incomplete regeneration: For 2010 and subsequent model year vehicles, 

the OBD II system shall detect a regeneration malfunction when the PM 

filter does not properly regenerate under manufacturer-defined conditions 

where regeneration is designed to occur. 

(9.2.4) NMHC conversion: For 2010 and subsequent model year vehicles 

passenger cars, light-duty trucks, and MDPVs certified to a chassis 

dynamometer tailpipe emission standard and 2013 and subsequent model 

year medium-duty vehicles (including MDPVs) certified to an engine 

dynamometer tailpipe emission standard with catalyzed PM filters that 

convert NMHC emissions, the OBD II system shall monitor the catalyst 

function of the PM filter and detect a malfunction when the NMHC 

conversion capability decreases to the point that NMHC emissions exceed 

the applicable emission levels specified in section (f)(9.2.2)(A). If no 

failure or deterioration of the NMHC conversion capability could result in a 

vehicle’s NMHC emissions exceeding these emission levels, the OBD II 

system shall detect a malfunction when the system has no detectable 

amount of NMHC conversion capability. 

(9.2.5) Missing substrate: The OBD II system shall detect a malfunction if either 

the PM filter substrate is completely destroyed, removed, or missing, or if 

the PM filter assembly is replaced with a muffler or straight pipe. 

(9.2.6) Active/Intrusive Injection: For systems that utilize active/intrusive injection 

(e.g., in-cylinder post fuel injection, in-exhaust air-assisted fuel injection) 

to achieve regeneration of the PM filter, the OBD II system shall detect a 

malfunction if any failure or deterioration of the injection system’s ability to 

properly regulate injection causes the system to be unable to achieve 

regeneration of the PM filter. 

(9.2.7) Feedback Control: 

(A) Except as provided for in section (f)(9.2.7)(B), if the vehicle is equipped 

with feedback or feed-forward control of the PM filter regeneration (e.g., 

feedback control of oxidation catalyst inlet temperature, PM filter inlet or 

outlet temperature, in-cylinder or in-exhaust fuel injection), the OBD II 

system shall detect a malfunction: 

(i) If the system fails to begin feedback control within a manufacturer 

specified time interval; 

(ii) If a failure or deterioration causes open loop or default operation; or 

(iii) If feedback the control system has used up all of the adjustment 

allowed by the manufacturer or reached its maximum authority and 

cannot achieve the feedback target. 
94

(B) A manufacturer may request Executive Officer approval to temporarily 

disable monitoring for the malfunction criteria specified in section 

(f)(9.2.7)(A)(iii) during conditions that a manufacturer cannot robustly 

distinguish between a malfunctioning system and a properly operating 

system. The Executive Officer shall approve the disablement upon the 

manufacturer submitting data and/or analysis demonstrating that the 

control system, when operating as designed on a vehicle with all emission 

controls working properly, routinely operates during these conditions with 

all of the adjustment allowed by the manufacturer used up. 

(C) In lieu of detecting the malfunctions specified in sections (f)(9.2.7)(A)(i) 

and (ii) with a PM filter-specific monitor, the OBD II system may monitor 

the individual parameters or components that are used as inputs for PM 

filter regeneration feedback control provided that the monitors detect all 

malfunctions that meet the criteria in sections (f)(9.2.7)(A)(i) and (ii). 

(9.3) Monitoring Conditions: 

(9.3.1) Manufacturers shall define the monitoring conditions for malfunctions 

identified in sections (f)(9.2.1) through (9.2.76) in accordance with 

sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements), with the 

exception that monitoring shall occur every time the monitoring conditions 

are met during the driving cycle in lieu of once per driving cycle as 

required in section (d)(3.1.2). For all 2010 and subsequent model year 

vehicles, for purposes of tracking and reporting as required in section 

(d)(3.2.2), all monitors used to detect malfunctions identified in section 

(f)(9.2.1) shall be tracked separately but reported as a single set of values 

as specified in section (d)(5.2.2).

(9.3.2) Except as provided in section (f)(9.3.3), the OBD II system shall monitor 

continuously for malfunctions identified in section (f)(9.2.7) (i.e., PM filter 

feedback control).

(9.3.3) Manufacturers may request Executive Officer approval to temporarily 

disable continuous monitoring under conditions technically necessary to 

ensure robust detection of malfunctions and to avoid false passes and 

false indications of malfunctions. The Executive Officer shall approve the 

request upon determining that the manufacturer has submitted data 

and/or an engineering evaluation which demonstrate that a properly 

operating system cannot be distinguished from a malfunctioning system 

and that the disablement interval is limited only to that which is technically 

necessary.

(9.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(10) CRANKCASE VENTILATION (CV) SYSTEM MONITORING 

(10.1) Requirement: Manufacturers shall monitor the CV system on vehicles 

so-equipped for system integrity. Vehicles not subject to crankcase emission 

control requirements shall be exempt from monitoring of the CV system. 

(10.2) Malfunction Criteria: 

(10.2.1) For the purposes of section (f)(10), “CV system” is defined as any form of 

crankcase ventilation system, regardless of whether it utilizes positive 

pressure or whether it vents to the atmosphere, the intake, or the exhaust. 
95

 “CV valve” is defined as any form of valve, orifice, or filter/separator used 

to restrict, control, or alter the composition (e.g., remove oil vapor or 

particulate matter) of the crankcase vapor flow. Further, any additional 

external CV system tubing or hoses used to equalize crankcase pressure 

or to provide a ventilation path between various areas of the engine (e.g., 

crankcase and valve cover) are considered part of the CV system 

“between the crankcase and the CV valve” and subject to the malfunction 

criteria in section (f)(10.2.2) below. 

(10.2.2) Except as provided below, the OBD II system shall detect a malfunction 

of the CV system when a disconnection of the system occurs between 

either the crankcase and the CV valve, or between the CV valve and the 

intake ducting. 

(10.2.3) If disconnection in the system results in a rapid loss of oil or other overt 

indication of a CV system malfunction such that the vehicle operator is 

certain to respond and have the vehicle repaired, the Executive Officer 

shall exempt the manufacturer from detection of that disconnection. 

(10.2.4) Detection of a disconnection is not required if the disconnection cannot 

be made without first disconnecting a monitored portion of the system 

(e.g., the CV system is designed such that the CV valve is fastened 

directly to the crankcase in a manner which makes it significantly more 

difficult to remove the valve from the crankcase before disconnecting the 

line between the valve and the intake ducting (taking aging effects into 

consideration) and the line between the valve and the intake ducting is 

monitored for disconnection). 

(10.2.5) Subject to Executive Officer approval, system designs that utilize tubing 

between the valve and the crankcase shall also be exempted from the 

monitoring requirement for detection of disconnection between the 

crankcase and the CV valve. The manufacturer shall file a request and 

submit data and/or engineering evaluation in support of the request. The 

Executive Officer shall approve the request upon determining that the 

connections between the valve and the crankcase are: (i) resistant to 

deterioration or accidental disconnection, (ii) significantly more difficult to 

disconnect than the line between the valve and the intake ducting, and (iii) 

not subject to disconnection per manufacturer’s maintenance, service, 

and/or repair procedures for non-CV system repair work. 

(10.2.6) Manufacturers are not required to detect disconnections that are unlikely 

to occur due to a CV system design that is integral to the induction system 

(e.g., internal machined passages rather than tubing or hoses). 

(10.2.7) For medium-duty vehicles with engines certified on an engine 

dynamometer having an open CV system (i.e., a system that releases 

crankcase emissions to the atmosphere without routing them to the intake 

ducting or to the exhaust upstream of the aftertreatment), the 

manufacturer shall submit a plan for Executive Officer approval of the 

monitoring strategy, malfunction criteria, and monitoring conditions prior to 

OBD certification. Executive Officer approval shall be based on the 

effectiveness of the monitoring strategy to (i) monitor the performance of 

the CV system to the extent feasible with respect to the malfunction 

criteria in section (f)(10.2.1) through (f)(10.2.4) and the monitoring 
96

conditions required by the diagnostic, and (ii) monitor the ability of the CV 

system to control crankcase vapor emitted to the atmosphere relative to 

the manufacturer’s design and performance specifications for a properly 

functioning system (e.g., if the system is equipped with a filter and/or 

separator to reduce crankcase emissions to the atmosphere, the OBD II 

system shall monitor the integrity of the filter and/or function of the 

separator). 

(10.3) Monitoring Conditions: Manufacturers shall define the monitoring conditions 

for malfunctions identified in section (f)(10.2) in accordance with sections 

(d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). 

(10.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). The stored 

fault code need not specifically identify the CV system (e.g., a fault code for 

EGR or intake air mass flow rationality monitoring can be stored) if the 

manufacturer demonstrates that additional monitoring hardware would be 

necessary to make this identification and provided that the manufacturer’s 

diagnostic and repair procedures for the detected malfunction include 

directions to check the integrity of the CV system.

(11) ENGINE COOLING SYSTEM MONITORING 

(11.1) Requirement: 

(11.1.1) The OBD II system shall monitor the thermostat on vehicles so-equipped 

for proper operation. 

(11.1.2) The OBD II system shall monitor the engine coolant temperature (ECT) 

sensor for circuit continuity, out-of-range values, and rationality faults. 

(11.2) Malfunction Criteria: 

(11.2.1) Thermostat 

(A) The OBD II system shall detect a thermostat malfunction (e.g., leaking or 

early-to-open thermostat) if, within an Executive Officer approved time 

interval after starting the engine, either of the following two conditions 

occur: 

(i) The coolant temperature does not reach the highest temperature 

required by the OBD II system to enable other diagnostics; 

(ii) The coolant temperature does not reach a warmed-up temperature 

within 20 degrees Fahrenheit of the manufacturer’s nominal thermostat 

regulating temperature. Subject to Executive Officer approval, a 

manufacturer may utilize lower temperatures for this criterion upon the 

Executive Officer determining that the manufacturer has demonstrated 

that the fuel, injection timing, and/or other coolant temperature-based 

modifications to the engine control strategies would not cause an 

emission increase of 50 or more percent of any of the applicable 

standards. 

(B) For 2013 and subsequent model year vehicles, the OBD II system shall 

detect a thermostat fault if, after the coolant temperature has reached the 

temperatures indicated in sections (f)(11.2.1)(A)(i) and (ii), the coolant 

temperature drops below the temperature indicated in section 

(f)(11.2.1)(A)(i).
97

(B)(C) Executive Officer approval of the time interval after engine start under 

section (f)(11.2.1)(A) above shall be granted upon determining that the 

data and/or engineering evaluation submitted by the manufacturer 

supports the specified times. 

(C)(D) For monitoring of malfunctions under section (f)(11.2.1)(A), Wwith 

Executive Officer approval, a manufacturer may use alternate malfunction 

criteria and/or monitoring conditions (see section (f)(11.3)) that are a 

function of temperature at engine start on vehicles that do not reach the 

temperatures specified in the malfunction criteria when the thermostat is 

functioning properly. Executive Officer approval shall be granted upon 

determining that the manufacturer has submitted data that demonstrate 

that a properly operating system does not reach the specified 

temperatures, that the monitor is capable of meeting the specified 

malfunction criteria at engine start temperatures greater than 50 degrees 

Fahrenheit, and that the overall effectiveness of the monitor is 

comparable to a monitor meeting these thermostat monitoring 

requirements at lower temperatures. 

(D)(E) With Executive Officer approval, manufacturers may omit this monitor. 

 Executive Officer approval shall be granted upon determining that the 

manufacturer has demonstrated that a malfunctioning thermostat cannot 

cause a measurable increase in emissions during any reasonable driving 

condition nor cause any disablement of other monitors. 

(11.2.2) ECT Sensor 

(A) Circuit Continuity. The OBD II system shall detect a malfunction when a 

lack of circuit continuity or out-of-range value occurs. 

(B) Time to Reach Closed-Loop Enable Temperature. 

(i) The OBD II system shall detect a malfunction if the ECT sensor does 

not achieve the stabilized minimum temperature which is needed to 

begin closed-loop or feedback operation of emission-related engine 

controls (e.g., feedback control of fuel pressure, EGR flow, boost 

pressure) within an Executive Officer approved time interval after 

starting the engine. The time interval shall be a function of starting 

ECT and/or a function of intake or ambient temperature. 

(ii) Executive Officer approval of the time interval shall be granted upon 

determining that the data and/or engineering evaluation submitted by 

the manufacturer supports the specified times. 

(iii) The Executive Officer shall exempt manufacturers from the 

requirement of section (f)(11.2.2)(B) if the manufacturer does not 

utilize ECT to enable closed loop or feedback operation of emissionrelated engine controls. 

(C) Stuck in Range Below the Highest Minimum Enable Temperature. To the 

extent feasible when using all available information, the OBD II system 

shall detect a malfunction if the ECT sensor inappropriately indicates a 

temperature below the highest minimum enable temperature required by 

the OBD II system to enable other diagnostics (e.g., an OBD II system 

that requires ECT to be greater than 140 degrees Fahrenheit to enable a 

diagnostic must detect malfunctions that cause the ECT sensor to 

inappropriately indicate a temperature below 140 degrees Fahrenheit). 
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Manufacturers are exempted from this requirement for temperature 

regions in which the monitors required under sections (f)(11.2.1) or 

(f)(11.2.2)(B) will detect ECT sensor malfunctions as defined in section 

(f)(11.2.2)(C). 

(D) Stuck in Range Above the Lowest Maximum Enable Temperature. 

(i) To the extent feasible when using all available information, the OBD II 

system shall detect a malfunction if the ECT sensor inappropriately 

indicates a temperature above the lowest maximum enable 

temperature required by the OBD II system to enable other diagnostics 

(e.g., an OBD II system that requires ECT to be less than 90 degrees 

Fahrenheit at engine start to enable a diagnostic must detect 

malfunctions that cause the ECT sensor to inappropriately indicate a 

temperature above 90 degrees Fahrenheit). 

(ii) Manufacturers are exempted from this requirement for temperature 

regions in which the monitors required under sections (f)(11.2.1), 

(f)(11.2.2)(B), or (f)(11.2.2)(C) (i.e., ECT sensor or thermostat 

malfunctions) will detect ECT sensor malfunctions as defined in 

section (f)(11.2.2)(D) or in which the MIL will be illuminated under the 

requirements of section (d)(2.2.3) for default mode operation (e.g., 

overtemperature protection strategies). 

(iii) For 2006 and subsequent model year applications, manufacturers are 

also exempted from the requirements of section (f)(11.2.2)(D) for 

temperature regions where the temperature gauge indicates a 

temperature in the red zone (engine overheating zone) or an 

overtemperature warning light is illuminated for vehicles that have a 

temperature gauge or warning light on the instrument panel and utilize 

the same ECT sensor for input to the OBD II system and the 

temperature gauge/warning light. 

(11.3) Monitoring Conditions: 

(11.3.1) Thermostat 

(A) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (f)(11.2.1)(A) in accordance with section (d)(3.1) 

except as provided for in section (f)(11.3.1)(DE). Additionally, except as 

provided for in sections (f)(11.3.1)(B) and (C), monitoring for malfunctions 

identified in section (f)(11.2.1)(A) shall be conducted once per driving 

cycle on every driving cycle in which the ECT sensor indicates, at engine 

start, a temperature lower than the temperature established as the 

malfunction criteria in section (f)(11.2.1)(A). 

(B) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (f)(11.2.1)(B) in accordance with section (d)(3.1) with 

the exception that monitoring shall occur every time the monitoring 

conditions are met during the driving cycle in lieu of once per driving cycle.

(B)(C) Manufacturers may disable thermostat monitoring at ambient 

temperatures below 20 degrees Fahrenheit. 

(C)(D) Manufacturers may request Executive Officer approval to suspend or 

disable thermostat monitoring if the vehicle is subjected to conditions 

which could lead to false diagnosis (e.g., vehicle operation at idle for more 

than 50 percent of the warm-up time, hot restart conditions, etc.). In 
99

general, the Executive Officer shall not approve disablement of the 

monitor on engine starts where the ECT at engine start is more than 35 

degrees Fahrenheit lower than the thermostat malfunction threshold 

temperature determined under section (f)(11.2.1)(A). The Executive 

Officer shall approve the request upon determining that the manufacturer 

has provided data and/or engineering analysis that demonstrate the need 

for the request. 

(D)(E) With respect to defining enable conditions that are encountered during 

the FTP or Unified cycle as required in (d)(3.1.1) for malfunctions 

identified in section (f)(11.2.1)(A), the FTP cycle shall refer to on-road 

driving following the FTP cycle in lieu of testing on a chassis or engine 

dynamometer. 

(11.3.2) ECT Sensor 

(A) Except as provided below in section (f)(11.3.2)(E), monitoring for 

malfunctions identified in section (f)(11.2.2)(A) (i.e., circuit continuity and 

out-of-range) shall be conducted continuously. 

(B) Manufacturers shall define the monitoring conditions for malfunctions 

identified in section (f)(11.2.2)(B) in accordance with section (d)(3.1). 

Additionally, except as provided for in section (f)(11.3.2)(D), monitoring for 

malfunctions identified in section (f)(11.2.2)(B) shall be conducted once 

per driving cycle on every driving cycle in which the ECT sensor indicates 

a temperature lower than the closed-loop enable temperature at engine 

start (i.e., all engine start temperatures greater than the ECT sensor outof-range low temperature and less than the closed-loop enable 

temperature). 

(C) Manufacturers shall define the monitoring conditions for malfunctions 

identified in sections (f)(11.2.2)(C) and (D) in accordance with sections 

(d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). 

(D) Manufacturers may suspend or delay the time to reach closed-loop 

enable temperature diagnostic if the vehicle is subjected to conditions 

which could lead to false diagnosis (e.g., vehicle operation at idle for more 

than 50 to 75 percent of the warm-up time). 

(E) A manufacturer may request Executive Officer approval to disable 

continuous ECT sensor monitoring when an ECT sensor malfunction 

cannot be distinguished from other effects. The Executive Officer shall 

approve the disablement upon determining that the manufacturer has 

submitted test data and/or engineering evaluation that demonstrate a 

properly functioning sensor cannot be distinguished from a malfunctioning 

sensor and that the disablement interval is limited only to that necessary 

for avoiding false detection. 

(11.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(12) COLD START EMISSION REDUCTION STRATEGY MONITORING 

(12.1) Requirement: 

(12.1.1) For all 2010 and subsequent model year vehicles, if a vehicle 

incorporates a specific engine control strategy to reduce cold start 

emissions, the OBD II system shall monitor the system to verify the 
100

strategy achieves the desired effect (e.g., to achieve accelerated catalyst 

light-off temperature) and monitor the commanded elements/components

for proper function (e.g., injection timing, increased engine idle speed, 

increased engine load via intake or exhaust throttle activation) while the 

control strategy is active to ensure proper operation of the control 

strategy. 

(12.2) Malfunction Criteria: The OBD II system shall, to the extent feasible, detect a 

malfunction if either of the following occurs: 

(12.2.1) Any single commanded element/component does not properly respond 

to the commanded action while the cold start strategy is active. For 

purposes of this section, “properly respond” is defined as when the 

element responds: 

(A) by a robustly detectable amount by the monitor; and 

(B) in the direction of the desired command; and 

(C) above and beyond what the element/component would achieve on startup without the cold start strategy active (e.g., if the cold start strategy 

commands a higher idle engine speed, a fault must be detected if there is 

no detectable amount of engine speed increase above what the system 

would achieve without the cold start strategy active); 

(12.2.2) Any failure or deterioration of the cold start emission reduction control 

strategy that would cause a vehicle’s NMHC, CO, NOx, or PM emissions 

to exceed: 

(A) For passenger cars, light-duty trucks, and MDPVs certified to a chassis 

dynamometer tailpipe emission standard: 

(i) 2.5 times the applicable FTP standards for 2010 through 2012 model 

year vehicles; and 

(ii) 1.5 times the applicable FTP NMHC, CO, or NOx standards or 2.0 

times the applicable FTP PM standard for 2013 and subsequent model 

year vehicles. 

(B) For medium-duty vehicles (including MDPVs) certified to an engine 

dynamometer tailpipe emission standard: 

(i) 2.0 times the applicable NMHC or CO standards, the applicable NOx 

standard by more than 0.2 g/bhp-hr (e.g., cause NOx emissions to 

exceed 0.4 g/bhp-hr if the emission standard is 0.2 g/bhp-hr) as 

measured from an applicable cycle emission test, or 0.03 g/bhp-hr PM 

as measured from an applicable cycle emission test for 2013 and 

subsequent model year vehicles. 

(12.2.3) For section (f)(12.2.2),:

(A) For 2010 through 2012 model year vehicles, the OBD II system shall 

either monitor the combined effect of the elements of the system as a 

whole or the individual elements (e.g., increased engine speed, increased 

engine load from restricting an exhaust throttle) for failures that cause 

emissions to exceed the applicable emission levels specified in section 

(f)(12.2.2). 

(B) For 2013 and subsequent model year vehicles, to the extent feasible 

(without adding hardware for this purpose), the OBD II system shall 

monitor the ability of the system to achieve the desired effect (e.g., 

strategies used to accelerate catalyst light-off by increasing catalyst inlet 
101

temperature shall verify the catalyst inlet temperature actually achieves 

the desired temperatures within an Executive Officer approved time 

interval after starting the engine) for failures that cause emissions to 

exceed the applicable emission levels specified in section (f)(12.2.2). For 

strategies where it is not feasible to be monitored as a system, the OBD II 

system shall monitor the individual elements/components (e.g., increased 

engine speed, increased engine load from restricting an exhaust throttle) 

for failures that cause emissions to exceed the applicable emission levels 

specified in section (f)(12.2.2).

(12.3) Monitoring Conditions: Manufacturers shall define the monitoring conditions 

for malfunctions identified in section (f)(12.2) in accordance with sections 

(d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements). 

(12.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(13) VARIABLE VALVE TIMING AND/OR CONTROL (VVT) SYSTEM MONITORING 

(13.1) Requirement: On all 2006 and subsequent model year applications, the 

OBD II system shall monitor the VVT system on vehicles so-equipped for 

target error and slow response malfunctions. The individual electronic 

components (e.g., actuators, valves, sensors, etc.) that are used in the VVT 

system shall be monitored in accordance with the comprehensive 

components requirements in section (f)(15). 

(13.2) Malfunction Criteria: 

(13.2.1) Target Error: The OBD II system shall detect a malfunction prior to any 

failure or deterioration in the capability of the VVT system to achieve the 

commanded valve timing and/or control within a crank angle or lift 

tolerance that would cause a vehicle's NMHC, CO, NOx, or PM emissions 

to exceed: 

(A) For passenger cars, light-duty trucks, and MDPVs certified to a chassis 

dynamometer tailpipe emission standard: 

(i) 3.0 times the applicable FTP standards for 2006 through 2009 model 

year vehicles; 

(ii) 2.5 times the applicable FTP standards for 2010 through 2012 model 

year vehicles; and 

(iii) 1.5 times the applicable FTP NMHC, CO, or NOx standards or 2.0 

times the applicable FTP PM standard for 2013 and subsequent model 

year vehicles. 

(B) For medium-duty vehicles (including MDPVs) certified to an engine 

dynamometer tailpipe emission standard: 

(i) 1.5 times the applicable NMHC, CO, and NOx standards or 0.03 g/bhphr PM as measured from an applicable cycle emission test for 2006 

and subsequent model year vehicles certified to an engine 

dynamometer tailpipe NOx emission standard of greater than 0.50 

g/bhp-hr NOx; 

(ii) 2.5 times the applicable NMHC or CO standards, the applicable NOx 

standard by more than 0.3 g/bhp-hr (e.g., cause NOx emissions to 

exceed 0.5 g/bhp-hr if the emission standard is 0.2 g/bhp-hr) as 

measured from an applicable cycle emission test, or 0.03 g/bhp-hr PM 
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as measured from an applicable cycle emission test for 2006 through 

2012 model year vehicles certified to an engine dynamometer tailpipe 

NOx emission standard of less than or equal to 0.50 g/bhp-hr NOx; 

and 

(iii) 2.0 times the applicable NMHC or CO standards, the applicable NOx 

standard by more than 0.2 g/bhp-hr (e.g., cause NOx emissions to 

exceed 0.4 g/bhp-hr if the emission standard is 0.2 g/bhp-hr) as 

measured from an applicable cycle emission test, or 0.03 g/bhp-hr PM 

as measured from an applicable cycle emission test for 2013 and 

subsequent model year vehicles certified to an engine dynamometer 

tailpipe NOx emission standard of less than or equal to 0.50 g/bhp-hr 

NOx. 

(13.2.2) Slow Response: The OBD II system shall detect a malfunction prior to 

any failure or deterioration in the capability of the VVT system to achieve 

the commanded valve timing and/or control within a time that would cause 

a vehicle's emissions to exceed the applicable emission levels specified in 

sections (f)(13.2.1). 

(13.2.3) For vehicles in which no failure or deterioration of the VVT system could 

result in a vehicle’s emissions exceeding the levels specified in sections 

(f)(13.2.1), the VVT system shall be monitored for proper functional 

response in accordance with the malfunction criteria in section (f)(15.2). 

(13.3) Monitoring Conditions: Manufacturers shall define the monitoring conditions 

for VVT system malfunctions identified in section (f)(13.2) in accordance with 

sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements), with the 

exception that monitoring shall occur every time the monitoring conditions are 

met during the driving cycle in lieu of once per driving cycle as required in 

section (d)(3.1.2). Additionally, manufacturers shall track and report VVT 

system monitor performance under section (d)(3.2.2). For purposes of 

tracking and reporting as required in section (d)(3.2.2), all monitors used to 

detect malfunctions identified in section (f)(13.2) shall be tracked separately 

but reported as a single set of values as specified in section (d)(5.2.2). 

(13.4) MIL Illumination and Fault Code Storage: General requirements for MIL 

illumination and fault code storage are set forth in section (d)(2). 

(14) [RESERVED] 

(15) COMPREHENSIVE COMPONENT MONITORING 

(15.1) Requirement: 

(15.1.1) Except as provided in sections (f)(15.1.3), (f)(15.1.4), and (f)(16), the 

OBD II system shall monitor for malfunction any electronic powertrain 

component/system not otherwise described in sections (f)(1) through 

(f)(14) that either provides input to (directly or indirectly) or receives 

commands from the on-board computer(s), and: (1) can affect emissions 

during any reasonable in-use driving condition, or (2) is used as part of 

the diagnostic strategy for any other monitored system or component. 

(A) Input Components: Input components required to be monitored may 

include the vehicle speed sensor, crank angle sensor, pedal position 

sensor, mass air flow sensor, cam position sensor, fuel pressure sensor, 
103

intake air temperature sensor, exhaust temperature sensor, and 

transmission electronic components such as sensors, modules, and 

solenoids which provide signals to the powertrain control system. 

(B) Output Components/Systems: Output components/systems required to be 

monitored may include the idle governor, fuel injectors, automatic 

transmission solenoids or controls, turbocharger electronic components, 

the wait-to-start lamp, and cold start aids (e.g., glow plugs, intake air 

heaters). 

(15.1.2) For purposes of criteria (1) in section (f)(15.1.1) above, the manufacturer 

shall determine whether a powertrain input or output component/system 

can affect emissions. If the Executive Officer reasonably believes that a 

manufacturer has incorrectly determined that a component/system cannot 

affect emissions, the Executive Officer shall require the manufacturer to 

provide emission data showing that the component/system, when 

malfunctioning and installed in a suitable test vehicle, does not have an 

emission effect. The Executive Officer may request emission data for any 

reasonable driving condition. 

(15.1.3) Manufacturers shall monitor for malfunction electronic powertrain input or 

output components/systems associated with an electronic transfer case, 

electronic power steering system, two speed axle, or other components 

that are driven by the engine and not related to the control of fueling, air 

handling, or emissions only if the component or system is used as part of 

the diagnostic strategy for any other monitored system or component. 

(15.1.4) Except as specified for hybrids in section (f)(15.1.5), manufacturers shall 

monitor for malfunction electronic powertrain input or output 

components/systems associated with components that only affect 

emissions by causing additional electrical load to the engine and are not 

related to the control of fueling, air handling, or emissions only if the 

component or system is used as part of the diagnostic strategy for any 

other monitored system or component. 

(15.1.5) For hybrids, manufacturers shall submit a plan to the Executive Officer 

for approval of the hybrid components determined by the manufacturer to 

be subject to monitoring in section (f)(15.1.1). In general, the Executive 

Officer shall approve the plan if it includes monitoring of all 

components/systems used as part of the diagnostic strategy for any other 

monitored system or component, monitoring of all energy input devices to 

the electrical propulsion system, monitoring of battery and charging 

system performance, monitoring of electric motor performance, and 

monitoring of regenerative braking performance. 

(15.2) Malfunction Criteria: 

(15.2.1) Input Components: 

(A) The OBD II system shall detect malfunctions of input components caused 

by a lack of circuit continuity, out-of-range values, and, where feasible, 

rationality faults. To the extent feasible, the rationality fault diagnostics 

shall verify that a sensor output is neither inappropriately high nor 

inappropriately low (e.g., “two-sided” diagnostics). 

(B) To the extent feasible, rationality faults shall be separately detected and 

store different fault codes than the respective lack of circuit continuity and 
104

out of range diagnostics. Additionally, input component lack of circuit 

continuity and out of range faults shall be separately detected and store 

different fault codes for each distinct malfunction (e.g., out-of-range low, 

out-of-range high, open circuit, etc.). Manufacturers are not required to 

store separate fault codes for lack of circuit continuity faults that cannot be 

distinguished from other out-of-range circuit faults. 

(C) For input components that are directly or indirectly used for any emission 

control strategies that are not covered under sections (f)(1) through (f)(13)

(e.g., exhaust temperature sensors used for a control strategy that 

regulates SCR catalyst inlet temperature within a target window), the 

OBD II system shall detect rationality malfunctions that prevent the 

component from correctly sensing any condition necessary for the 

strategy to operate in its intended manner. These malfunctions include 

faults that inappropriately prevent or delay the activation of the emission 

control strategy, cause the system to erroneously exit the emission control 

strategy, or where the control strategy has used up all of the adjustments 

or authority allowed by the manufacturer and is still unable to achieve the 

desired condition. The Executive Officer may waive detection of specific 

malfunctions upon determining that the manufacturer has submitted data 

and/or an engineering evaluation that demonstrate that reliable detection 

of the malfunction is technically infeasible or would require additional 

hardware.

(15.2.2) Output Components/Systems: 

(A) The OBD II system shall detect a malfunction of an output 

component/system when proper functional response of the component 

and system to computer commands does not occur. If a functional check 

is not feasible, the OBD II system shall detect malfunctions of output 

components/systems caused by a lack of circuit continuity or circuit fault 

(e.g., short to ground or high voltage). For output component lack of 

circuit continuity faults and circuit faults, manufacturers are not required to 

store different fault codes for each distinct malfunction (e.g., open circuit, 

shorted low, etc.). Manufacturers are not required to activate an output 

component/system when it would not normally be active for the purposes 

of performing functional monitoring of output components/systems as 

required in section (f)(15). 

(B) The idle fuel control system shall be monitored for proper functional 

response to computer commands. A malfunction shall be detected when 

either any of the following conditions occur: 

(i) The idle fuel control system cannot achieve or maintain the target idle 

speed or fuel injection quantity within +/- 30 percent of the 

manufacturer-specified fuel quantity and target or desired engine 

speed tolerances. 

(ii) The idle fuel control system cannot achieve the target idle speed or 

fuel injection quantity within the smallest engine speed or fueling 

quantity tolerance range required by the OBD II system to enable any 

other monitor. 

(iii) For 2013 and subsequent model year vehicles, the idle control system 

cannot achieve the fuel injection quantity within the smallest fueling 
105

quantity tolerance range required by the OBD II system to enable any 

other monitor.

(iv) For 2013 and subsequent model year vehicles, the idle control system 

cannot achieve the target idle speed with a fuel injection quantity within 

+/-50 percent of the fuel quantity necessary to achieve the target idle 

speed for a properly functioning vehicle and the given operating 

conditions.

(C) Glow plugs/intake air heaters shall be monitored for proper functional 

response to computer commands. The glow plug/intake air heater 

circuit(s) shall be monitored for proper current and voltage drop. The 

Executive Officer shall approve other monitoring strategies based on 

manufacturer’s data and/or engineering analysis demonstrating equally 

reliable and timely detection of malfunctions. If a manufacturer 

demonstrates that a single glow plug failure cannot cause a measurable 

increase in emissions during any reasonable driving condition, the 

manufacturer shall detect a malfunction for the minimum number of glow 

plugs needed to cause an emission increase. Further, to the extent 

feasible on existing engine designs (without adding additional hardware 

for this purpose) and on all new design engines, the stored fault code 

shall identify the specific malfunctioning glow plug(s). For 2010 and 

subsequent model year vehicles, manufacturers shall detect a malfunction 

when a single glow plug/intake air heater no longer operates within the 

manufacturer’s specified limits for normal operation (e.g., within 

specifications established by the manufacturer with the part supplier for 

acceptable part performance at high mileage). 

(D) The wait-to-start lamp circuit shall be monitored for malfunctions that 

cause the lamp to fail to illuminate when commanded on (e.g., burned out 

bulb). 

(E) For output components/systems that are directly or indirectly used for any 

emission control strategies that are not covered under sections (f)(1) 

through (f)(13) (e.g., an intake throttle used for a control strategy that 

adjusts intake throttle position to regulate SCR catalyst inlet temperature 

within a target window), the OBD II system shall detect functional 

malfunctions that prevent the component/system from achieving the 

desired functional response necessary for the strategy to operate in its 

intended manner. These malfunctions include faults that inappropriately 

prevent or delay the activation of the emission control strategy, cause the 

system to erroneously exit the emission control strategy, or where the 

control strategy has used up all of the adjustments or authority allowed by 

the manufacturer and is still unable to achieve the desired condition. The 

Executive Officer may waive detection of specific malfunctions upon 

determining that the manufacturer has submitted data and/or an 

engineering evaluation that demonstrate that reliable detection of the 

malfunction is technically infeasible or would require additional hardware.

(E)(F) For 2013 and subsequent model year vehicles that utilize fuel control 

system components (e.g., injectors, fuel pump) that have tolerance 

compensation features implemented in hardware or software during 

production or repair procedures (e.g., individually coded injectors for flow 
106

characteristics that are programmed into an electronic control unit to 

compensate for injector to injector tolerances, fuel pumps that use in-line 

resistors to correct for differences in fuel pump volume output), the 

components shall be monitored to ensure the proper compensation is 

being used. The system shall detect a fault if the compensation being 

used by the control system does not match the compensation designated 

for the installed component (e.g., the flow characteristic coding designated 

on a specific injector does not match the compensation being used by the 

fuel control system for that injector). If a manufacturer demonstrates that 

a single component (e.g., injector) using the wrong compensation cannot 

cause a measurable increase in emissions during any reasonable driving 

condition, the manufacturer shall detect a malfunction for the minimum 

number of components using the wrong compensation needed to cause 

an emission increase. Further, the stored fault code shall identify the 

specific component that does not match the compensation. 

(15.3) Monitoring Conditions: 

(15.3.1) Input Components: 

(A) Except as provided in section (f)(15.3.1)(C), input components shall be 

monitored continuously for proper range of values and circuit continuity. 

(B) For rationality monitoring (where applicable), manufacturers shall define 

the monitoring conditions for detecting malfunctions in accordance with 

sections (d)(3.1) and (d)(3.2) (i.e., minimum ratio requirements), with the 

exception that rationality monitoring shall occur every time the monitoring 

conditions are met during the driving cycle in lieu of once per driving cycle 

as required in section (d)(3.1.2).: 

(C) A manufacturer may request Executive Officer approval to disable 

continuous input component proper range of values or circuit continuity 

monitoring when a malfunction cannot be distinguished from other effects. 

 The Executive Officer shall approve the disablement upon determining 

that the manufacturer has submitted test data and/or documentation that 

demonstrate a properly functioning input component cannot be 

distinguished from a malfunctioning input component and that the 

disablement interval is limited only to that necessary for avoiding false 

detection. 

(15.3.2) Output Components/Systems: 

(A) Except as provided in section (f)(15.3.2)(D), monitoring for circuit 

continuity and circuit faults shall be conducted continuously. 

(B) Except as provided in section (f)(15.3.2)(C), for functional monitoring, 

manufacturers shall define the monitoring conditions for detecting 

malfunctions in accordance with sections (d)(3.1) and (d)(3.2) (i.e., 

minimum ratio requirements). 

(C) For the idle fuel control system, manufacturers shall define the monitoring 

conditions for functional monitoring in accordance with sections (d)(3.1) 

and (d)(3.2) (i.e., minimum ratio requirements), with the exception that 

functional monitoring shall occur every time the monitoring conditions are 

met during the driving cycle in lieu of once per driving cycle as required in 

section (d)(3.1.2). 
107

(D) A manufacturer may request Executive Officer approval to disable 

continuous output component circuit continuity or circuit fault monitoring 

when a malfunction cannot be distinguished from other effects. The 

Executive Officer shall approve the disablement upon determining that the 

manufacturer has submitted test data and/or documentation that 

demonstrate a properly functioning output component cannot be 

distinguished from a malfunctioning output component and that the 

disablement interval is limited only to that necessary for avoiding false 

detection. 

(15.4) MIL Illumination and Fault Code Storage: 

(15.4.1) Except as provided in sections (f)(15.4.2) and (f)(15.4.4) below, general 

requirements for MIL illumination and fault code storage are set forth in 

section (d)(2). 

(15.4.2) Exceptions to general requirements for MIL illumination. MIL illumination 

is not required in conjunction with storing a confirmed fault code for any 

comprehensive component if: 

(A) the component or system, when malfunctioning, could not cause vehicle 

emissions to increase by: 

(i) 25 percent or more for PC/LDT SULEV II vehicles, or 

(ii) 15 percent or more for all other vehicles, and

(B) the component or system is not used as part of the diagnostic strategy for 

any other monitored system or component. 

(15.4.3) For purposes of determining the emission increase in section 

(f)(15.4.2)(A), the manufacturer shall request Executive Officer approval of 

the test cycle/vehicle operating conditions for which the emission increase 

will be determined. Executive Officer approval shall be granted upon 

determining that the manufacturer has submitted data and/or engineering 

evaluation that demonstrate that the testing conditions represent in-use 

driving conditions where emissions are likely to be most affected by the 

malfunctioning component. For purposes of determining whether the 

specified percentages in section (f)(15.4.2)(A) are exceeded, if the 

approved testing conditions are comprised of an emission test cycle with 

an emission standard, the measured increase shall be compared to a 

percentage of the emission standard (e.g., if the increase is equal to or 

more than 15 percent of the emission standard for that test cycle). If the 

approved testing conditions are comprised of a test cycle or vehicle 

operating condition that does not have an emission standard, the 

measured increase shall be calculated as a percentage of the baseline 

test (e.g., if the increase from a back-to-back test sequence between 

normal and malfunctioning condition is equal to or more than 15 percent 

of the baseline test results from the normal condition).

(15.4.4) For malfunctions required to be detected by section (f)(15.2.2)(B)(iii) (idle 

control fuel injection quantity faults), the stored fault code is not required 

to specifically identify the idle control system (e.g., a fault code for cylinder 

fuel injection quantity imbalance or combustion quality monitoring can be 

stored). 

(16) OTHER EMISSION CONTROL OR SOURCE SYSTEM MONITORING 
108

(16.1) Requirement: For other emission control or source systems that are not 

identified or addressed in sections (f)(1) through (f)(15) (e.g., homogeneous 

charge compression ignition (HCCI) controls, hydrocarbon traps, fuel-fired 

passenger compartment heaters), manufacturers shall submit a plan for 

Executive Officer approval of the monitoring strategy, malfunction criteria, 

and monitoring conditions prior to introduction on a production vehicle 

intended for sale in California. Executive Officer approval shall be based on 

the effectiveness of the monitoring strategy, the malfunction criteria utilized, 

and the monitoring conditions required by the diagnostic and, if applicable, 

the determination that the requirements of section (f)(16.3) and (f)(16.4) 

below are satisfied. 

(16.2) For purposes of section (f)(16), emission source systems are components or 

devices that emit pollutants subject to vehicle evaporative and exhaust 

emission standards (e.g., NMOG, CO, NOx, PM) and include non-electronic 

components and non-powertrain components (e.g., fuel-fired passenger 

compartment heaters, on-board reformers). 

(16.3) Except as provided below in this paragraph, for 2005 and subsequent model 

year vehicles that utilize emission control systems that alter intake air flow or 

cylinder charge characteristics by actuating valve(s), flap(s), etc. in the intake 

air delivery system (e.g., swirl control valve systems), the manufacturers, in 

addition to meeting the requirements of section (f)(16.1) above, may elect to 

have the OBD II system monitor the shaft to which all valves in one intake 

bank are physically attached in lieu of monitoring the intake air flow, cylinder 

charge, or individual valve(s)/flap(s) for proper functional response. For nonmetal shafts or segmented shafts, the monitor shall verify all shaft segments 

for proper functional response (e.g., by verifying the segment or portion of the 

shaft furthest from the actuator properly functions). For systems that have 

more than one shaft to operate valves in multiple intake banks, 

manufacturers are not required to add more than one set of detection 

hardware (e.g., sensor, switch, etc.) per intake bank to meet this requirement. 

 Vehicles utilizing these emission control systems designed and certified for 

2004 or earlier model year vehicles and carried over to the 2005 through 

2009 model year shall not be required to meet the provisions of section 

(f)(16.3) until the engine or intake air delivery system is redesigned. 

(16.4) For emission control strategies that are not covered under sections (f)(1) 

through (f)(13) (e.g., a control strategy that regulates SCR catalyst inlet 

temperatures within a target window), Executive Officer approval shall be 

based on the effectiveness of the plan in detecting malfunctions that prevent 

the strategy from operating in its intended manner. These malfunctions 

include faults that inappropriately prevent or delay the activation of the 

emission control strategy, faults that cause the system to erroneously exit the 

emission control strategy, and faults where the control strategy has used up 

all of the adjustments or authority allowed by the manufacturer and is still 

unable to achieve the desired condition. The Executive Officer may waive 

detection of specific malfunctions upon determining that the manufacturer 

has submitted data and/or an engineering evaluation that demonstrate that 

reliable detection of the malfunction is technically infeasible or would require 

additional hardware.
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(17) EXCEPTIONS TO MONITORING REQUIREMENTS 

(17.1) Except as provided in sections (f)(17.1.1) through (17.1.4) below, upon 

request of a manufacturer or upon the best engineering judgment of the ARB, 

the Executive Officer may revise the emission threshold for a malfunction on 

any diagnostic required in section (f) for medium-duty vehicles if the most 

reliable monitoring method developed requires a higher threshold to prevent 

significant errors of commission in detecting a malfunction. Additionally, for 

2007 through 2009 model year light-duty vehicles and 2007 through 2012 

model year medium-duty vehicles, the Executive Officer may revise the PM 

filter malfunction criteria of section (f)(9.2.1) to exclude detection of specific 

failure modes (e.g., combined failure of partially melted and partially cracked 

substrates) if the most reliable monitoring method developed requires the 

exclusion of specific failure modes to prevent significant errors of commission 

in detecting a malfunction. 

(17.1.1) For PC/LDT SULEV II vehicles, the Executive Officer shall approve a 

malfunction criterion of 2.5 times the applicable FTP standards in lieu of 

1.5 or 1.75 wherever required in section (f). 

(17.1.2) For vehicles certified to Federal Bin 3 or Bin 4 emission standards, 

manufacturers shall utilize the ULEV II vehicle NMOG and CO malfunction 

criteria (e.g., 1.5 times the Bin 3 or Bin 4 NMOG and CO standards) and 

the PC/LDT SULEV II vehicle NOx malfunction criteria (e.g., 2.5 times the 

Bin 3 or Bin 4 NOx standards). 

(17.1.3) For medium-duty diesel vehicles (including MDPVs) certified to an engine 

dynamometer tailpipe emission standard, the Executive Officer shall 

approve a malfunction criteria of “the applicable PM standard plus 0.02 

g/bhp-hr PM (e.g., unable to maintain PM emissions at or below 0.03 

g/bhp-hr if the emission standard is 0.01 g/bhp-hr) as measured from an 

applicable cycle emission test” in lieu of “0.03 g/bhp-hr PM as measured 

from an applicable cycle emission test” wherever required in section (f). 

The Executive Officer shall also approve a malfunction criteria of “the 

applicable PM standard plus 0.04 g/bhp-hr PM (e.g., unable to maintain 

PM emissions at or below 0.05 g/bhp-hr if the emission standard is 0.01 

g/bhp-hr) as measured from an applicable cycle emission test” in lieu of 

“0.05 g/bhp-hr PM as measured from an applicable cycle emission test” 

wherever required in section (f). 

(17.1.4) For 2007 through 2009 medium-duty diesel vehicles (including MDPVs) 

certified to an engine dynamometer FTP tailpipe PM emission standard of 

greater than or equal 0.08 g/bhp-hr, the Executive Officer shall approve a 

malfunction of criteria of 1.5 times the applicable PM standard in lieu of 

the applicable PM malfunction criteria required for any monitor in section 

(f). 

(17.1.5) For medium-duty diesel vehicles (except MDPVs) certified to a chassis 

dynamometer tailpipe emission standard, the monitoring requirements 

and malfunction criteria in section (f) applicable to medium-duty diesel 

vehicles certified to an engine dynamometer tailpipe emission standard 

shall apply. However, the manufacturer shall request Executive Officer 

approval of manufacturer-proposed medium-duty chassis dynamometer-
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based malfunction criteria in lieu of the engine dynamometer-based 

malfunction criteria required for each monitor in section (f). The Executive 

Officer shall approve the request upon finding that: 

(A) the manufacturer has used good engineering judgment in determining the 

malfunction criteria, 

(B) the malfunction criteria will provide for similar timeliness in detection of 

malfunctioning components with respect to detection of malfunctions on 

medium-duty diesel vehicles certified to an engine dynamometer tailpipe 

emission standard, 

(C) the malfunction criteria are set as stringently as technologically feasible 

with respect to indicating a malfunction at the lowest possible tailpipe 

emission levels (but not lower than 1.5 times the chassis dynamometer 

tailpipe emission standard the vehicle is certified to), considering the best 

available monitoring technology to the extent that it is known or should 

have been known to the manufacturer, 

(D) the malfunction criteria will prevent detection of a malfunction when the 

monitored component is within the performance specifications for 

components aged to the end of the full useful life, and 

(E) the manufacturer has provided emission data showing the emission levels 

at which the malfunctions are detected. 

(17.2) Whenever the requirements in section (f) of this regulation require a 

manufacturer to meet a specific phase-in schedule: 

(17.2.1) The phase-in percentages shall be based on the manufacturer’s 

projected sales volume for all vehicles subject to the requirements of title 

13, CCR section 1968.2 unless specifically stated otherwise in section (f). 

(17.2.2) Manufacturers may use an alternate phase-in schedule in lieu of the 

required phase-in schedule if the alternate phase-in schedule provides for 

equivalent compliance volume as defined in section (c) except as 

specifically noted for the phase in of in-use monitor performance ratio 

monitoring conditions in section (d)(3.2). 

(17.2.3) Small volume manufacturers may use an alternate phase-in schedule in 

accordance with section (f)(17.2.2) in lieu of the required phase-in 

schedule or may meet the requirement on all vehicles by the final year of 

the phase-in in lieu of meeting the specific phase-in requirements for each 

model year. 

(17.3) Manufacturers may request Executive Officer approval to disable an OBD II 

system monitor at ambient temperatures below twenty degrees Fahrenheit 

(20°F) (low ambient temperature conditions may be determined based on 

intake air or engine coolant temperature) or at elevations above 8000 feet 

above sea level. The Executive Officer shall approve the request upon 

determining that the manufacturer has provided data and/or an engineering 

evaluation that demonstrate that monitoring during the conditions would be 

unreliable. A manufacturer may further request, and the Executive Officer 

shall approve, that an OBD II system monitor be disabled at other ambient 

temperatures upon determining that the manufacturer has demonstrated with 

data and/or an engineering evaluation that misdiagnosis would occur at the 
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ambient temperatures because of its effect on the component itself (e.g., 

component freezing). 

(17.4) Manufacturers may request Executive Officer approval to disable monitoring 

systems that can be affected by low fuel level or running out of fuel (e.g., 

misfire detection) when the fuel level is 15 percent or less of the nominal 

capacity of the fuel tank. The Executive Officer shall approve the request 

upon determining that the manufacturer has submitted data and/or an 

engineering evaluation that demonstrate that monitoring at the fuel levels 

would be unreliable. 

(17.5) Manufacturers may disable monitoring systems that can be affected by 

vehicle battery or system voltage levels. 

(17.5.1) For monitoring systems affected by low vehicle battery or system 

voltages, manufacturers may disable monitoring systems when the battery 

or system voltage is below 11.0 Volts. Manufacturers may request 

Executive Officer approval to utilize a voltage threshold higher than 11.0 

Volts to disable system monitoring. The Executive Officer shall approve 

the request upon determining that the manufacturer has submitted data 

and/or an engineering evaluation that demonstrate that monitoring at the 

voltages would be unreliable and that either operation of a vehicle below 

the disablement criteria for extended periods of time is unlikely or the 

OBD II system monitors the battery or system voltage and will detect a 

malfunction at the voltage used to disable other monitors. 

(17.5.2) For monitoring systems affected by high vehicle battery or system 

voltages, manufacturers may request Executive Officer approval to 

disable monitoring systems when the battery or system voltage exceeds a 

manufacturer-defined voltage. The Executive Officer shall approve the 

request upon determining that the manufacturer has submitted data 

and/or an engineering evaluation that demonstrate that monitoring above 

the manufacturer-defined voltage would be unreliable and that either the 

electrical charging system/alternator warning light is illuminated (or voltage 

gauge is in the “red zone”) or that the OBD II system monitors the battery 

or system voltage and will detect a malfunction at the voltage used to 

disable other monitors. 

(17.6) A manufacturer may disable affected monitoring systems in vehicles 

designed to accommodate the installation of Power Take-Off (PTO) units (as 

defined in section (c)), provided disablement occurs only while the PTO unit 

is active, and the OBD II readiness status is cleared by the on-board 

computer (i.e., all monitors set to indicate “not complete”) while the PTO unit 

is activated (see section (g)(4.1) below). If the disablement occurs, the 

readiness status may be restored to its state prior to PTO activation when the 

disablement ends. 

(17.7) Whenever the requirements in section (f) of this regulation require monitoring 

“to the extent feasible”, the manufacturer shall submit its proposed monitor(s) 

for Executive Officer approval. The Executive Officer shall approve the 

proposal upon determining that the proposed monitor(s) meets the criteria of 

“to the extent feasible” by considering the best available monitoring 

technology to the extent that it is known or should have been known to the 

manufacturer and given the limitations of the manufacturer’s existing 
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hardware, the extent and degree to which the monitoring requirements are 

met in full, the limitations of the monitoring necessary to prevent significant 

errors of commission and omission, and the extent to which the manufacturer 

has considered and pursued alternative monitoring concepts to meet the 

requirements in full. The manufacturer’s consideration and pursuit of 

alternative monitoring concepts shall include evaluation of other modifications 

to the proposed monitor(s), the monitored components themselves, and other 

monitors that use the monitored components (e.g., altering other monitors to 

lessen the sensitivity and reliance on the component or characteristic of the 

component subject to the proposed monitor(s)). 

(g) STANDARDIZATION REQUIREMENTS. 

(1) Reference Documents: 

The following Society of Automotive Engineers (SAE) and International 

Organization for Standardization (ISO) documents are incorporated by reference 

into this regulation: 

(1.1) SAE J1930 "Electrical/Electronic Systems Diagnostic Terms, Definitions, 

Abbreviations, and Acronyms – Equivalent to ISO/TR 15031-2:April 30, 

2002", April 2002October 2008 (SAE J1930). 

(1.2) SAE J1962 "Diagnostic Connector – Equivalent to ISO/DIS 15031-

3:December 14, 2001", April 2002 (SAE J1962). 

(1.3) SAE J1978 "OBD II Scan Tool – Equivalent to ISO/DIS 15031-4:December 

14, 2001", April 2002 (SAE J1978). 

(1.4) SAE J1979 "E/E Diagnostic Test Modes", May 2007 (SAE J1979). 

(1.5) SAE J1850 "Class B Data Communications Network Interface", May 2001 

(SAE 1850). 

(1.6) SAE J2012 "Diagnostic Trouble Code Definitions – Equivalent to ISO/DIS 

15031-6:April 30, 2002", April 2002December 2007 (SAE J2012). 

(1.7) ISO 9141-2:1994 "Road Vehicles-Diagnostic Systems-CARB Requirements 

for Interchange of Digital Information", February 1994 (ISO 9141-2). 

(1.8) ISO 14230-4:2000 "Road Vehicles-Diagnostic Systems-KWP 2000 

Requirements for Emission-related Systems", June 2000 (ISO 14230-4). 

(1.9) ISO 15765-4:2005 "Road vehicles-Diagnostics on Controller Area Network 

(CAN) - Part 4: Requirements for emissions-related systems", January 2005 

(ISO 15765-4). 

(1.10) SAE J1939 consisting of:

(1.10.1) January 2005 -J1939 “Recommended Practice for a Serial Control and 

Communications Vehicle Network” and the associated subparts included 

in SAE HS-1939, “Truck and Bus Control and Communications Network 

Standards Manual”, 2005 Edition (SAE J1939)March 2009.;

(1.10.2) J1939/1 “Recommended Practice for Control and Communications 

Network for On-Highway Equipment”, September 01, 2000;

(1.10.3) J1939/11 “Physical Layer, 250K bits/s, Twisted Shielded Pair”,

September 18, 2006;

(1.10.4) J1939/13 “Off-Board Diagnostic Connector”, March 11, 2004;

(1.10.5) J1939/15 “Reduced Physical Layer, 250K bits/sec, UN-Shielded Twisted 

Pair (UTP)”, August 21, 2008;
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(1.10.6) J1939/21 “Data Link Layer”, December 22, 2006;

(1.10.7) J1939/31 “Network Layer”, April 02, 2004;

(1.10.8) J1939/71 “Vehicle Application Layer (Through February 2008)”, January

20, 2009;

(1.10.1)(1.10.9) SAE J1939-/73 “Application Layer - Diagnostics”, September 08, 

2006.;

(1.10.10) J1939/81 “Network Management”, May 08, 2003; and

(1.10.11) J1939/84 “OBD Communications Compliance Test Cases For Heavy 

Duty Components and Vehicles”, December 2008.

(1.11) SAE J1699-3 – “OBD II Compliance Test Cases”, May 2006 (SAE J1699-3). 

(1.12) SAE J2534-1 – “Recommended Practice for Pass-Thru Vehicle 

Programming”, December 2004 (SAE J2534-1). 

(2) Diagnostic Connector: 

A standard data link connector conforming to SAE J1962 specifications (except 

as specified in section (g)(2.3)) shall be incorporated in each vehicle. 

(2.1) The connector shall be located in the driver’s side foot-well region of the 

vehicle interior in the area bound by the driver’s side of the vehicle and the 

driver's side edge of the center console (or the vehicle centerline if the vehicle 

does not have a center console) and at a location no higher than the bottom 

of the steering wheel when in the lowest adjustable position. The connector 

may not be located on or in the center console (i.e., neither on the horizontal 

faces near the floor-mounted gear selector, parking brake lever, or cupholders nor on the vertical faces near the car stereo, climate system, or 

navigation system controls). The location of the connector shall be capable 

of being easily identified by a “crouched” technician entering the vehicle from 

the driver’s side. 

(2.2) If the connector is covered, the cover must be removable by hand without the 

use of any tools and be labeled to aid technicians in identifying the location of 

the connector. Access to the diagnostic connector may not require opening 

or the removal of any storage accessory (e.g., ashtray, coinbox, etc.). The 

label shall be submitted to the Executive Officer for review and approval, at or 

before the time the manufacturer submits its certification application. The 

Executive Officer shall approve the label upon determining that it clearly 

identifies that the connector is located behind the cover and is consistent with 

language and/or symbols commonly used in the automotive industry. 

(2.3) Any pins in the connector that provide electrical power shall be properly fused 

to protect the integrity and usefulness of the connector for diagnostic 

purposes and may not exceed 20.0 Volts DC regardless of the nominal 

vehicle system or battery voltage (e.g., 12V, 24V, 42V, etc.). 

(3) Communications to a Scan Tool: 

Manufacturers shall use one of the following standardized protocols for 

communication of all required emission related messages from on-board to offboard network communications to a scan tool meeting SAE J1978 specifications: 

(3.1) SAE J1850. All required emission related messages using this protocol shall 

use the Cyclic Redundancy Check and the three byte header, may not use 
114

inter-byte separation or checksums, and may not require a minimum delay of 

100 ms between SAE J1978 scan tool requests. This protocol may not be 

used on any 2008 or subsequent model year vehicle. 

(3.2) ISO 9141-2. This protocol may not be used on any 2008 or subsequent 

model year vehicle. 

(3.3) ISO 14230-4. This protocol may not be used on any 2008 or subsequent 

model year vehicle. 

(3.4) ISO 15765-4. This protocol shall be allowed on any 2003 and subsequent 

model year vehicle and required on all 2008 and subsequent model year 

vehicles. All required emission-related messages using this protocol shall 

use a 500 kbps baud rate. 

(4) Required Emission Related Functions: 

The following standardized functions shall be implemented in accordance with 

the specifications in SAE J1979 to allow for access to the required information by 

a scan tool meeting SAE J1978 specifications: 

(4.1) Readiness Status: In accordance with SAE J1979 specifications, the OBD II 

system shall indicate “complete” or “not complete” since the fault memory 

was last cleared for each of the installed monitored components and systems 

identified in sections (e)(1) through (e)(8), (e)(15), (f)(1) through (f)(4), (f)(6), 

(f)(8), and (f)(15). All 2010 and subsequent model year diesel vehicles shall 

additionally indicate the appropriate readiness status for monitors identified in 

sections (f)(5), (f)(7), and (f)(9). All 2010 subsequent model year vehicles 

equipped with VVT system monitoring and subject to the test results 

requirements specified in section (g)(4.5.4)(C) shall additionally indicate the 

appropriate readiness status for VVT system monitors identified in sections 

(e)(13) and (f)(13). All components or systems that are monitored 

continuously shall always indicate “complete”. Those components or 

systems that are not subject to continuous monitoring shall immediately 

indicate “complete” upon the respective diagnostic(s) being fully executed 

and determining that the component or system is not malfunctioning. A 

component or system shall also indicate “complete” if after the requisite 

number of decisions necessary for determining MIL status have been fully 

executed, the monitor indicates a malfunction for the component or system. 

The status for each of the monitored components or systems shall indicate 

“not complete” whenever fault memory has been cleared or erased by a 

means other than that allowed in section (d)(2). Normal vehicle shut down 

(i.e., key off, engine off) may not cause the status to indicate “not complete”. 

(4.1.1) Subject to Executive Officer approval, if monitoring is disabled for a 

multiple number of driving cycles due to the continued presence of 

extreme operating conditions (e.g., cold ambient temperatures, high 

altitudes, etc), readiness status for the subject monitoring system may be 

set to indicate “complete” without monitoring having been completed. 

Executive Officer approval shall be based on the conditions for monitoring 

system disablement and the number of driving cycles specified without 

completion of monitoring before readiness is indicated as “complete”. 

(4.1.2) For the evaporative system monitor: 
115

(A) Except as provided below in section (g)(4.1.2)(B), the readiness status 

shall be set in accordance with section (g)(4.1) when both the functional 

check of the purge valve and the leak detection monitor of the orifice size 

specified in either section (e)(4.2.2)(B) or (C) (e.g., 0.040 inch or 0.020 

inch) indicate that they are complete. 

(B) For vehicles that utilize a 0.090 inch (in lieu of 0.040 inch) leak detection 

monitor in accordance with section (e)(4.2.5), the readiness status shall 

be set in accordance with section (g)(4.1) when both the functional check 

of the purge valve and the leak detection monitor of the orifice size 

specified in section (e)(4.2.2)(C) (e.g., 0.020 inch) indicate that they are 

complete. 

(4.1.3) If the manufacturer elects to additionally indicate readiness status through 

the MIL in the key on, engine off position as provided for in section 

(d)(2.1.3), the readiness status shall be indicated in the following manner: 

If the readiness status for all monitored components or systems is 

“complete”, the MIL shall remain continuously illuminated in the key on, 

engine off position for at least 15-20 seconds. If the readiness status for 

one or more of the monitored components or systems is “not complete”, 

after 15-20 seconds of operation in the key on, engine off position with the 

MIL illuminated continuously, the MIL shall blink once per second for 5-10 

seconds. The data stream value for MIL status (section (g)(4.2)) shall 

indicate “commanded off” during this sequence unless the MIL has also 

been “commanded on” for a detected fault. 

(4.2) Data Stream: The following signals shall be made available on demand 

through the standardized data link connector in accordance with SAE J1979 

specifications. The actual signal value shall always be used instead of a 

default or limp home value. 

(4.2.1) For all vehicles: calculated load value, number of stored confirmed fault 

codes, engine coolant temperature, engine speed, absolute throttle 

position (if equipped with a throttle), vehicle speed, OBD requirements to 

which the engine is certified (e.g., California OBD II, EPA OBD, European 

OBD, non-OBD) and MIL status (i.e., commanded-on or commanded-off). 

(4.2.2) For all vehicles so equipped: fuel control system status (e.g., open loop, 

closed loop, etc.), fuel trim, fuel pressure, ignition timing advance, intake 

air temperature, manifold absolute pressure, air flow rate from mass air 

flow sensor, secondary air status (upstream, downstream, or 

atmosphere), oxygen sensor output, air/fuel ratio sensor output. 

(4.2.3) For all 2005 and subsequent model year vehicles using the ISO 15765-4 

protocol for the standardized functions required in section (g), the 

following signals shall also be made available: absolute load, fuel level (if 

used to enable or disable any other diagnostics), relative throttle position 

(if equipped with a throttle), barometric pressure (directly measured or 

estimated), engine control module system voltage, commanded 

equivalence ratio, catalyst temperature (if directly measured or estimated 

for purposes of enabling the catalyst monitor(s)), monitor status (i.e., 

disabled for the rest of this driving cycle, complete this driving cycle, or not 

complete this driving cycle) since last engine shut-off for each monitor 

used for readiness status, time elapsed since engine start, distance 
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traveled while MIL activated, distance traveled since fault memory last 

cleared, and number of warm-up cycles since fault memory last cleared. 

(4.2.4) For all 2005 and subsequent model year vehicles so equipped and using 

the ISO 15765-4 protocol for the standardized functions required in 

section (g): ambient air temperature, evaporative system vapor pressure, 

commanded purge valve duty cycle/position, commanded EGR valve duty 

cycle/position, EGR error between actual and commanded, PTO status 

(active or not active), redundant absolute throttle position (for electronic 

throttle or other systems that utilize two or more sensors), absolute pedal 

position, redundant absolute pedal position, and commanded throttle 

motor position. 

(4.2.5) Additionally, for all 2010 and subsequent model year vehicles with a diesel 

engine: 

(A) Calculated load (engine torque as a percentage of maximum torque 

available at the current engine speed), driver’s demand engine torque (as 

a percentage of maximum engine torque), actual engine torque (as a 

percentage of maximum engine torque), engine oil temperature (if used 

for emission control or any OBD diagnostics), time elapsed since engine 

start; and

(B) Fuel level (if used to enable or disable any other diagnostics), barometric 

pressure (directly measured or estimated), engine control module system 

voltage; and 

(C) Monitor status (i.e., disabled for the rest of this driving cycle, complete 

this driving cycle, or not complete this driving cycle) since last engine shutoff for each monitor used for readiness status, distance traveled (or 

engine run time for engines not utilizing vehicle speed information) while 

MIL activated, distance traveled (or engine run time for engines not 

utilizing vehicle speed information) since fault memory last cleared, and 

number of warm-up cycles since fault memory last cleared; and 

(D) For all engines so equipped: absolute throttle position, relative throttle 

position, fuel injection timing, intake manifold temperature, intercooler 

temperature, ambient air temperature, commanded EGR valve duty 

cycle/position, actual EGR valve duty cycle/position, EGR error between 

actual and commanded, PTO status (active or not active), absolute pedal 

position, redundant absolute pedal position, commanded throttle motor 

position, fuel rate, boost pressure, commanded/target boost pressure, 

turbo inlet air temperature, fuel rail pressure, commanded fuel rail 

pressure, PM filter inlet pressure, PM filter inlet temperature, PM filter 

outlet pressure, PM filter outlet temperature, PM filter delta pressure, 

exhaust pressure sensor output, exhaust gas temperature sensor output, 

injection control pressure, commanded injection control pressure, 

turbocharger/turbine speed, variable geometry turbo position, commanded 

variable geometry turbo position, turbocharger compressor inlet 

temperature, turbocharger compressor inlet pressure, turbocharger 

turbine inlet temperature, turbocharger turbine outlet temperature, 

wastegate valve position, glow plug lamp status, PM sensor output, and 

NOx sensor output; 
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(E) Additionally, for all 2010 and subsequent model year medium-duty 

vehicles with a diesel engine certified on an engine dynamometer: NOx 

NTE control area status (i.e., inside control area, outside control area, 

inside manufacturer-specific NOx NTE carve-out area, or NTE deficiency 

for NOx active area) and PM NTE control area status (i.e., inside control 

area, outside control area, inside manufacturer-specific PM NTE carve-out 

area, or NTE deficiency for PM active area).;

(F) For all 2013 and subsequent model year vehicles, normalized trigger for 

PM filter regeneration, PM filter regeneration status; and

(G) For all 2013 and subsequent model year vehicles, average distance (or 

engine run time for engines not utilizing vehicle speed information) 

between PM filter regenerations.

(4.2.6) Additionally, for all 2013 and subsequent model year vehicles so 

equipped:

(A) EGR temperature, variable geometry turbo control status (e.g., open loop, 

closed loop), reductant level (e.g., urea tank fill level), alcohol fuel 

percentage, type of fuel currently being used, NOx adsorber regeneration 

status, NOx adsorber deSOx status, hybrid battery pack remaining 

charge; and

(B) PM sensor output and distance traveled while low/empty SCR reductant 

driver warning/inducement active.

(4.3) Freeze Frame. 

(4.3.1) “Freeze frame” information required to be stored pursuant to sections 

(d)(2.2.7), (e)(3.4.3), (e)(6.4.4), (f)(3.4.2)(B), and (f)(4.4.2)(D) shall be 

made available on demand through the standardized data link connector 

in accordance with SAE J1979 specifications. 

(4.3.2) “Freeze frame” conditions must include the fault code which caused the 

data to be stored and all of the signals required in section (g)(4.2.1) 

except number of stored confirmed fault codes, OBD requirements to 

which the engine is certified, MIL status, and absolute throttle position in 

accordance with (g)(4.3.3). Freeze frame conditions shall also include all 

of the signals required on the vehicle in sections (g)(4.2.2) through 

(g)(4.2.5)(D), (g)(4.2.5)(F), and (g)(4.2.6)(A) that are used for diagnostic or 

control purposes in the specific diagnostic or emission-critical powertrain 

control unit that stored the fault code except: oxygen sensor output, 

air/fuel ratio sensor output, catalyst temperature, evaporative system 

vapor pressure, glow plug lamp status, PM sensor output, NOx sensor 

output, monitor status since last engine shut off, distance traveled while 

MIL activated, distance traveled since fault memory last cleared, and 

number of warm-up cycles since fault memory last cleared. 

(4.3.3) In lieu of including the absolute throttle position data specified in (g)(4.2.1) 

in the freeze frame data, diagnostic or emission-critical powertrain control 

units that do not use the absolute throttle position data may include the 

relative throttle position data specified in (g)(4.2.3) or pedal position data 

specified in (g)(4.2.4). 

(4.3.4) Only one frame of data is required to be recorded. Manufacturers may 

choose to store additional frames provided that at least the required frame 

can be read by a scan tool meeting SAE J1978 specifications. 
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(4.4) Fault Codes 

(4.4.1) For all monitored components and systems, stored pending, confirmed, 

and permanent fault codes shall be made available through the diagnostic 

connector in accordance with SAE J1979 specifications. Standardized 

fault codes conforming to SAE J2012 shall be employed. 

(4.4.2) The stored fault code shall, to the fullest extent possible, pinpoint the likely 

cause of the malfunction. To the extent feasible on all 2005 and 

subsequent model year vehicles, manufacturers shall use separate fault 

codes for every diagnostic where the diagnostic and repair procedure or 

likely cause of the failure is different. In general, rationality and functional 

diagnostics shall use different fault codes than the respective circuit 

continuity diagnostics. Additionally, input component circuit continuity 

diagnostics shall use different fault codes for distinct malfunctions (e.g., 

out-of-range low, out-of-range high, open circuit, etc.). 

(4.4.3) Manufacturers shall use appropriate SAE-defined fault codes of SAE 

J2012 (e.g., P0xxx, P2xxx) whenever possible. With Executive Officer 

approval, manufacturers may use manufacturer-defined fault codes in 

accordance with SAE J2012 specifications (e.g., P1xxx). Factors to be 

considered by the Executive Officer for approval shall include the lack of 

available SAE-defined fault codes, uniqueness of the diagnostic or 

monitored component, expected future usage of the diagnostic or 

component, and estimated usefulness in providing additional diagnostic 

and repair information to service technicians. Manufacturer-defined fault 

codes shall be used consistently (i.e., the same fault code may not be 

used to represent two different failure modes) across a manufacturer’s 

entire product line. 

(4.4.4) A fault code (pending and/or confirmed, as required in sections (d) (e), 

and (f)) shall be stored and available to an SAE J1978 scan tool within 10 

seconds after a diagnostic has determined that a malfunction has 

occurred. A permanent fault code shall be stored and available to an SAE 

J1978 scan tool no later than the end of an ignition cycle (including 

electronic control unit shutdown) in which the corresponding confirmed 

fault code causing the MIL to be illuminated has been stored. 

(4.4.5) Pending fault codes: 

(A) On all 2005 and subsequent model year vehicles, pending fault codes for 

all components and systems (including continuously and non-continuously 

monitored components) shall be made available through the diagnostic 

connector in accordance with SAE J1979 specifications (e.g., 

Mode/Service $07). 

(B) On all 2005 and subsequent model year vehicles, a pending fault code(s) 

shall be stored and available through the diagnostic connector for all 

currently malfunctioning monitored component(s) or system(s), regardless 

of the MIL illumination status or confirmed fault code status (e.g., even 

after a pending fault has matured to a confirmed fault code and the MIL is 

illuminated, a pending fault code shall be stored and available if the most 

recent monitoring event indicates the component is malfunctioning). 

(C) Manufacturers using alternate statistical protocols for MIL illumination as 

allowed in section (d)(2.2.6) shall submit to the Executive Officer a 
119

protocol for setting pending fault codes. The Executive Officer shall 

approve the proposed protocol upon determining that, overall, it is 

equivalent to the requirements in sections (g)(4.4.5)(A) and (B) and that it 

effectively provides service technicians with a quick and accurate 

indication of a pending failure. 

(4.4.6) Permanent fault codes: 

(A) Permanent fault codes for all components and systems shall be made 

available through the diagnostic connector in a standardized format that 

distinguishes permanent fault codes from both pending fault codes and 

confirmed fault codes. 

(B) A confirmed fault code shall be stored as a permanent fault code no later 

than the end of the ignition cycle and subsequently at all times that the 

confirmed fault code is commanding the MIL on (e.g., for currently failing 

systems but not during the 40 warm-up cycle self-healing process 

described in section (d)(2.4)). 

(C) Permanent fault codes shall be stored in NVRAM and may not be 

erasable by any scan tool command (generic or enhanced) or by 

disconnecting power to the on-board computer. 

(D) Permanent fault codes may not be erased when the control module 

containing the permanent fault codes is reprogrammed unless the 

readiness status (refer to section (g)(4.1)) for all monitored components 

and systems is set to “not complete” in conjunction with the 

reprogramming event. 

(E) The OBD system shall have the ability to store a minimum of four current 

confirmed fault codes as permanent fault codes in NVRAM. If the number 

of confirmed fault codes currently commanding the MIL on exceeds the 

maximum number of permanent fault codes that can be stored, the OBD 

system shall store the earliest detected confirmed fault codes as 

permanent fault codes. If additional confirmed fault codes are stored 

when the maximum number of permanent fault codes is already stored in 

NVRAM, the OBD system may not replace any existing permanent fault 

code with the additional confirmed fault codes. 

(4.5) Test Results 

(4.5.1) For all monitored components and systems for gasoline engine vehicles 

identified in sections (e)(1) through (e)(8) except misfire detection, fuel 

system monitoring, and oxygen sensor circuit and out-of-range monitoring, 

and for all monitored components and systems for diesel engine vehicles 

identified in sections (f)(1) through (f)(9) except those required to be 

monitored continuously, results of the most recent monitoring of the 

components and systems and the test limits established for monitoring the 

respective components and systems shall be stored and available through 

the data link in accordance with SAE J1979 specifications. 

(4.5.2) The test results shall be reported such that properly functioning 

components and systems (e.g., “passing” systems) do not store test 

values outside of the established test limits. 

(4.5.3) The test results shall be stored until updated by a more recent valid test 

result or the fault memory of the OBD II system computer is cleared. 

Upon fault memory being cleared, test results reported for monitors that 
120

have not yet completed since the last time the fault memory was cleared 

shall report values that do not indicate a failure (i.e., a test value which is 

outside of the test limits). 

(4.5.4) Additionally, for vehicles using ISO 15765-4 (see section (g)(3.4)) as the 

communication protocol: 

(A) The test results and limits shall be made available in the standardized 

format specified in SAE J1979 for the ISO 15765-4 protocol. Test results 

using vehicle manufacturer-defined monitor identifications (i.e., SAE 

J1979 OBDMIDs in the range of $E1-$FF) may not be used. 

(B) Test limits shall include both minimum and maximum acceptable values 

and shall be reported for all test results required in section (g)(4.5.1). The 

test limits shall be defined so that a test result equal to either test limit is a 

“passing” value, not a “failing” value. 

(C) For 2005 and subsequent model year vehicles, misfire monitoring test 

results shall be calculated and reported in the standardized format 

specified in SAE J1979. For 25 percent of 2009, 50 percent of 2010, and 

100 percent of 2011 and subsequent model year vehicles equipped with 

VVT systems, VVT monitoring test results and limits shall be stored and 

available in the standardized format specified in SAE J1979. 

(D) Monitors that have not yet completed since the last time the fault memory 

was cleared shall report values of zero for the test result and test limits. 

(E) All test results and test limits shall always be reported and the test results 

shall be stored until updated by a more recent valid test result or the fault 

memory of the OBD II system computer is cleared. For monitors with 

multiple pass/fail criteria (e.g., a purge flow diagnostic that can pass upon 

seeing a rich shift, lean shift, or engine speed change), on 25 percent of 

2009, 50 percent of 2010, and 100 percent of 2011 and subsequent 

model year vehicles, only the test results used in the most recent decision 

shall be reported with valid results and limits while test results not used in 

the most recent decision shall report values of zero for the test results and 

limits (e.g., a purge flow monitoring event that passed based on seeing a 

rich shift shall report the results and the limits of the rich shift test and 

shall report values of zero for the results and limits of the lean shift and 

engine speed change tests). 

(F) The OBD II system shall store and report unique test results for each 

separate diagnostic (e.g., an OBD II system with individual evaporative 

system diagnostics for 0.040 inch and 0.020 inch leaks shall separately 

report 0.040 inch and 0.020 inch test results). 

(4.6) Software Calibration Identification 

(4.6.1) On all vehicles, a software calibration identification number (CAL ID) for 

the diagnostic or emission critical powertrain control unit(s) shall be made 

available through the standardized data link connector in accordance with 

the SAE J1979 specifications. Except as provided for in section 

(g)(4.6.3), for 2009 and subsequent model year vehicles, the OBD II 

system shall use a single software calibration identification number (CAL 

ID) for each diagnostic or emission critical powertrain control unit(s) that 

replies to a generic scan tool with a unique module address. 
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(4.6.2) A unique CAL ID shall be used for every emission-related calibration 

and/or software set having at least one bit of different data from any other 

emission-related calibration and/or software set. Control units coded with 

multiple emission or diagnostic calibrations and/or software sets shall 

indicate a unique CAL ID for each variant in a manner that enables an offboard device to determine which variant is being used by the vehicle. 

Control units that utilize a strategy that will result in MIL illumination if the 

incorrect variant is used (e.g., control units that contain variants for 

manual and automatic transmissions but will illuminate the MIL if the 

variant selected does not match the type of transmission on the vehicle) 

are not required to use unique CAL IDs. 

(4.6.3) For 2009 and subsequent model year vehicles, manufacturers may 

request Executive Officer approval to respond with more than one CAL ID 

per diagnostic or emission critical powertrain control unit. Executive 

Officer approval of the request shall be based on the method used by the 

manufacturer to ensure each control unit will respond to a SAE J1978 

scan tool with the CAL IDs in order of highest to lowest priority with 

regards to areas of the software most critical to emission and OBD II 

system performance. 

(4.7) Software Calibration Verification Number 

(4.7.1) All 20052

 and subsequent model year vehicles shall use an algorithm to 

calculate a calibration verification number (CVN) that verifies the on-board 

computer software integrity in diagnostic or emission critical electronically 

reprogrammable powertrain control units. The CVN shall be made 

available through the standardized data link connector in accordance with 

the SAE J1979 specifications. The CVN shall be capable of being used to 

determine if the emission-related software and/or calibration data are valid 

and applicable for that vehicle and CAL ID. For 50 percent of 2010 and 

100 percent of 2011 and subsequent model year vehicles, one CVN shall 

be made available for each CAL ID made available and each CVN shall 

be output to a generic scan tool in the same order as the CAL IDs are 

output to the scan tool to allow the scan tool to match each CVN to the 

corresponding CAL ID. 

(4.7.2) Manufacturers shall request Executive Officer approval of the algorithm 

used to calculate the CVN. Executive Officer approval of the algorithm 

shall be based on the complexity of the algorithm and the difficulty in 

achieving the same CVN with modified calibration values. 

(4.7.3) The CVN shall be calculated at least once per driving cycle and stored 

until the CVN is subsequently updated. Except for immediately after a 

reprogramming event or a non-volatile memory clear or for the first 30 

seconds of engine operation after a volatile memory clear or battery 

disconnect, the stored value shall be made available through the data link 

connector to a generic scan tool in accordance with SAE J1979 

specifications. The stored CVN value may not be erased when fault 

 

2 The requirements of section (g)(4.7) shall supercede the requirements set forth in title 13, CCR section 

1968.1(l)(4.0). 
122

memory is erased by a generic scan tool in accordance with SAE J1979 

specifications or during normal vehicle shut down (i.e., key off, engine off). 

(4.7.4) For purposes of Inspection and Maintenance (I/M) testing, manufacturers 

shall make the CVN and CAL ID combination information available for all 

2008 and subsequent model year vehicles in a standardized electronic 

format that allows for off-board verification that the CVN is valid and 

appropriate for a specific vehicle and CAL ID. The standardized 

electronic format is detailed in Attachment E: CAL ID and CVN Data of 

ARB Mail-Out #MSC 06-23, December 21, 2006, incorporated by 

reference. Manufacturers shall submit the CVN and CAL ID information 

to the Executive Officer not more than 25 days after the close of a 

calendar quarter. 

(4.8) Vehicle Identification Number: 

(4.8.1) All 2005 and subsequent model year vehicles shall have the vehicle 

identification number (VIN) available in a standardized format through the 

standardized data link connector in accordance with SAE J1979 

specifications. Only one electronic control unit per vehicle shall report the 

VIN to an SAE J1978 scan tool. 

(4.8.2) For 2012 and subsequent model year vehicles, if the VIN is 

reprogrammable, all emission-related diagnostic information (i.e., all 

information required to be erased in accordance with SAE J1979 

specifications when a Mode/Service $04 clear/reset emission-related 

diagnostic information command is received) shall be erased in 

conjunction with the reprogramming of the VIN. 

(4.9) ECU Name: The name of each electronic control unit that responds to an 

SAE J1978 scan tool with a unique address or identifier shall be 

communicated in a standardized format in accordance with SAE J1979 (i.e., 

ECUNAME in Service/Mode $09, InfoType $0A). Except as specified for 

vehicles with more than one engine control unit, communication of the ECU 

name in a standardized format is required on 50 percent of 2010, 75 percent 

of 2011, and 100 percent of 2012 and subsequent model year vehicles. For 

vehicles with more than one engine control unit (e.g., a 12 cylinder engine 

with two engine control units, each of which controls six cylinders), 

communication of the ECU name is required on all 2010 and subsequent 

model year vehicles. 

(5) In-use Performance Ratio Tracking Requirements: 

(5.1) For each monitor required in section (e) to separately report an in-use 

performance ratio, manufacturers shall implement software algorithms to 

report a numerator and denominator in the standardized format specified 

below and in accordance with the SAE J1979 specifications. 

(5.2) Numerical Value Specifications: 

(5.2.1) For the numerator, denominator, general denominator, and ignition cycle 

counter: 

(A) Each number shall have a minimum value of zero and a maximum value 

of 65,535 with a resolution of one. 

(B) Each number shall be reset to zero only when a non-volatile memory 

reset occurs (e.g., reprogramming event, etc.) or, if the numbers are 
123

stored in keep-alive memory (KAM), when KAM is lost due to an 

interruption in electrical power to the control module (e.g., battery 

disconnect, etc.). Numbers may not be reset to zero under any other 

circumstances including when a scan tool command to clear fault codes 

or reset KAM is received. 

(C) If either the numerator or denominator for a specific component reaches 

the maximum value of 65,535 ±2, both numbers shall be divided by two 

before either is incremented again to avoid overflow problems. 

(D) If the ignition cycle counter reaches the maximum value of 65,535 ±2, the 

ignition cycle counter shall rollover and increment to zero on the next 

ignition cycle to avoid overflow problems. 

(E) If the general denominator reaches the maximum value of 65,535 ±2, the 

general denominator shall rollover and increment to zero on the next 

driving cycle that meets the general denominator definition to avoid 

overflow problems. 

(F) If a vehicle is not equipped with a component (e.g., oxygen sensor bank 

2, secondary air system), the corresponding numerator and denominator 

for that specific component shall always be reported as zero. 

(5.2.2) For the ratio: 

(A) The ratio shall have a minimum value of zero and a maximum value of 

7.99527 with a resolution of 0.000122. 

(B) A ratio for a specific component shall be considered to be zero whenever 

the corresponding numerator is equal to zero and the corresponding 

denominator is not zero. 

(C) A ratio for a specific component shall be considered to be the maximum 

value of 7.99527 if the corresponding denominator is zero or if the actual 

value of the numerator divided by the denominator exceeds the maximum 

value of 7.99527. 

(6) Engine Run Time Tracking Requirements: 

(6.1) For all 2010 and subsequent model year medium-duty vehicles equipped with 

diesel engines, manufacturers shall implement software algorithms to 

individually track and report in a standardized format the engine run time 

while being operated in the following conditions: 

(6.1.1) Total engine run time; 

(6.1.2) Total idle run time (with “idle” defined as accelerator pedal released by 

driver, vehicle speed less than or equal to one mile per hour, engine 

speed greater than or equal to 50 to 150 rpm below the normal warmedup idle speed (as determined in the drive position for vehicles equipped 

with an automatic transmission), and PTO not active), and either vehicle 

speed less than or equal to one mile per hour or engine speed less than 

or equal to 200 rpm above normal warmed-up idle; 

(6.1.3) Total run time with PTO active. 

(6.1.4) Total run time with EI-AECD #1active; 

(6.1.5) Total run time with EI-AECD #2 active; and so on up to 

(6.1.6) Total run time with EI-AECD #n active. 

(6.2) For all 2010 and subsequent model year light-duty vehicles equipped with 

diesel engines, manufacturers shall implement software algorithms to 
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individually track and report in a standardized format the engine run time 

while being operated in the following conditions: 

(6.2.1) Total engine run time; 

(6.2.2) Total run time with EI-AECD #1active; 

(6.2.3) Total run time with EI-AECD #2 active; and so on up to 

(6.2.4) Total run time with EI-AECD #n active. 

(6.3) Numerical Value Specifications: 

(6.3.1) For each counter specified in section (g)(6): 

(A) Each number shall conform to the standardized format specified in SAE 

J1979. 

(B) Each number shall be reset to zero only when a non-volatile memory 

reset occurs (e.g., reprogramming event). Numbers may not be reset to 

zero under any other circumstances including when a scan tool (generic 

or enhanced) command to clear fault codes or reset KAM is received. 

(C) If any of the individual counters reach the maximum value, all counters 

shall be divided by two before any are incremented again to avoid 

overflow problems. 

(6.4) Separation Specifications of EI-AECDs 

(6.4.1) For purposes of section (g)(6.4), the following terms shall be defined as 

follows:

(A) “Purpose” is defined as the objective of the EI-AECD when it is activated 

(e.g., EGR valve protection);

(B) “Action” is defined as a specific component/element act that is 

commanded when the EI-AECD is activated (e.g., EGR system is 

derated);

(C) “Parameter” is defined as a component/element (e.g., ECT, oil 

temperature) used to determine when to activate the EI-AECD; and

(D) “Condition” is defined as the specific characteristic/state exhibited by the 

parameter (e.g., ECT above 100 degrees Celsius) that triggers activation 

of the EI-AECD.

(6.4.1)Each EI-AECD shall be tracked individually and increment the counters at 

all times the conditions necessary to activate the EI-AECD are present.

(6.4.2) Each unique combination of action, parameter, and condition within a 

purpose shall be tracked as a separate EI-AECD and increment the 

timer(s) at all times the condition necessary to activate the EI-AECD is 

present.

(6.4.2)(A) For EI-AECDs that implement an action of variable degree based 

on the varying characteristics of a parameter (e.g., derate EGR more 

aggressively as engine oil temperature continues to increase), the EIAECD shall be tracked by incrementing two separate timers within a 

single EI-AECD (e.g., EI-AECD #1 timer 1 and EI-AECD #1 timer 2) as 

followshave variable actions or degrees of action (e.g., derate EGR more 

aggressively as engine oil temperature continues to increase), the EIAECD shall be tracked as two separate EI-AECDs and increment two 

counters.:

(A)(i) The first of the two counters timers shall be incremented whenever 

the EI-AECD is commanding some amount of reduced emission 

control effectiveness up to but not including 75 percent of the 
125

maximum reduced emission control effectiveness that the EI-AECD is 

capable of commanding during in-use vehicle or engine operation. For 

example, an overheat protection strategy that progressively derates 

EGR and eventually shuts off EGR as oil temperature increases would 

accumulate time for the first counter timer from the time derating of 

EGR begins up to the time that EGR is derated 75 percent. As a 

second example, an overheat protection strategy that advances fuel 

injection timing progressively up to a maximum advance of 15 degrees 

crank angle as the engine coolant temperature increases would 

accumulate time for the first counter timer from the time advance is 

applied up to the time that advance reaches 11.25 degrees (75 

percent of the maximum 15 degrees). 

(B)(ii) The second of the two counters timers shall be incremented 

whenever the EI-AECD is commanding 75 percent or more of the 

maximum reduced emission control effectiveness that the EI-AECD is 

capable of commanding during in-use vehicle or engine operation. For 

example, the second counter timer for the first example EI-AECD 

identified in section (g)(6.4.2.)(A)(i) would accumulate time from the 

time that EGR is derated 75 percent up to and including when EGR is 

completely shut off. For the second example EI-AECD identified in 

section (g)(6.4.2)(A)(i), the second counter timer would accumulate 

time from the time fuel injection timing advance is at 11.25 degrees up 

to and including the maximum advance of 15 degrees.

(6.4.3) A manufacturer may request Executive Officer approval to combine 

multiple unique actions, parameters, and/or conditions to be tracked within 

a single EI-AECD. The manufacturer shall submit a plan for combining, 

tracking, and incrementing the EI-AECD to the Executive Officer for 

approval. Executive Officer approval of the plan shall be based on the 

effectiveness and the equivalence of the incrementing plan to determine 

the amount of EI-AECD activity per condition relative to the measure of 

EI-AECD activity under section (g)(6.4.2).

(6.4.4) For EI-AECDs that are activated solely due to elevation, the timer shall be 

incremented only for the portion of EI-AECD activation when the elevation 

is below 8000 feet (e.g., the timer for an EI-AECD that is activated when 

the elevation is above 5000 feet shall be incremented only when the EIAECD is active and the elevation is below 8000 feet).

(6.4.5) For EI-AECDs that are initially activated due to engine warm-up and are 

subsequently reactivated after the engine has warmed up, the timer shall 

be incremented only when the EI-AECD is active after the initial engine 

warm-up (e.g., an EI-AECD that turns off an emission control at low 

engine coolant temperature would not increment the timer during initial 

warm-up but would increment the timer if coolant temperature 

subsequently dropped below the low temperature and reactivated the EIAECD later in the drive cycle).

(6.4.3)(6.4.6) If more than one EI-AECD is currently active, the counters timers for 

both EI-AECDs shall accumulate time, regardless if there is overlap or 

redundancy in the commanded action (e.g., two different EI-AECDs 

independently but simultaneously commanding EGR off shall both 
126

accumulate time in their respective counterstimers). 

(7) Exceptions to Standardization Requirements. 

(7.1) For medium-duty vehicles equipped with a diesel engine certified on an 

engine dynamometer, a manufacturer may request Executive Officer 

approval to use both: (1) an alternate diagnostic connector, and emissionrelated message structure and format in lieu of the standardization 

requirements in sections (g)(2) and (4) that refer to SAE J1962, SAE J1978, 

and SAE J1979, and (2) an alternate communication protocol in lieu of the 

identified protocols in section (g)(3). The Executive Officer shall approve the 

request if the alternate diagnostic connector, communication protocol, and 

emission-related message format and structure requested by the 

manufacturer meet the standardization requirements in title 13, CCR section 

1971.1 applicable for 2013 and subsequent model year heavy-duty diesel 

engines and the information required to be made available in section (g)( 4.1) 

through (g)(6) (e.g., readiness status, data stream parameters, permanent 

fault codes, engine run time tracking data) is available in a standardized 

format through the alternate emission-related message format. 

(7.2) For 2004 model year vehicles only, wherever the requirements of sections 

(g)(2) and (g)(4) reflect a substantive change from the requirements of title 

13, CCR sections 1968.1(e), (f), (k), or (l) for the 2003 model year vehicles, 

the manufacturer may request Executive Officer approval to continue to use 

the requirements of section 1968.1 in lieu of the requirements of sections 

(g)(2) and (g)(4). The Executive Officer shall approve the request upon 

determining that the manufacturer has submitted data and/or engineering 

evaluation that demonstrate that software or hardware changes would be 

required to comply with the requirements of sections (g)(2) and (g)(4) and that 

the system complies with the requirements of sections 1968.1(e), (f), (k), and 

(l). 

(h) MONITORING SYSTEM DEMONSTRATION REQUIREMENTS FOR 

CERTIFICATION. 

(1) General. 

(1.1) Certification requires that manufacturers submit emission test data from one 

or more durability demonstration test vehicles (test vehicles). For 

applications certified on engine dynamometers, engines may be used instead 

of vehicles. 

(1.2) The Executive Officer may approve other demonstration protocols if the 

manufacturer can provide comparable assurance that the malfunction criteria 

are chosen based on meeting emission requirements and that the timeliness 

of malfunction detection is within the constraints of the applicable monitoring 

requirements. 

(1.3) For flexible fuel vehicles capable of operating on more than one fuel or fuel 

combinations, the manufacturer shall submit a plan for providing emission 

test data to the Executive Officer for approval. The Executive Officer shall 

approve the plan if it is determined to be representative of expected in-use 

fuel or fuel combinations and provides accurate and timely evaluation of the 

monitored systems. 
127

(2) Selection of Test Vehicles: 

(2.1) Prior to submitting any applications for certification for a model year, a 

manufacturer shall notify the Executive Officer of the test groups planned for 

that model year. The Executive Officer will then select the test group(s) that 

the manufacturer shall use as demonstration test vehicles to provide 

emission test data. The selection of test vehicles for production vehicle 

evaluation, as specified in section (j), may take place during this selection 

process. 

(2.2) A manufacturer certifying one to five test groups in a model year shall provide 

emission test data from a test vehicle from one test group. A manufacturer 

certifying six to fifteen test groups in a model year shall provide emission test 

data from test vehicles from two test groups. A manufacturer certifying 

sixteen or more test groups in a model year shall provide emission test data 

from test vehicles from three test groups. The Executive Officer may waive 

the requirement for submittal of data from one or more of the test groups if 

data have been previously submitted for all of the test groups. 

(2.3) For the test vehicle(s), a manufacturer shall use a certification emission 

durability test vehicle(s), a representative high mileage vehicle(s), or a 

vehicle(s) aged to the end of the full useful life using an ARB-approved 

alternative durability procedure (ADP). 

(3) Required Testing for Gasoline/Spark-ignited vehicles: 

Except as provided below, the manufacturer shall perform single-fault testing 

based on the applicable FTP test with the following components/systems set at 

their malfunction criteria limits as determined by the manufacturer for meeting 

the requirements of section (e): 

(3.1) Exhaust Gas Sensors: 

(3.1.1) The manufacturer shall perform a test with all primary oxygen sensors 

(conventional switching sensors and wide range or universal sensors) 

used for fuel control simultaneously possessing a response rate 

deteriorated to the malfunction criteria limit. Manufacturers shall also 

perform a test for any other oxygen sensor parameter that can cause 

vehicle emissions to exceed the malfunction threshold (e.g., 1.5 times the 

applicable standards due to a shift in air/fuel ratio at which oxygen sensor 

switches, decreased amplitude, etc.). When performing additional test(s), 

all primary and secondary (if applicable) oxygen sensors used for fuel 

control shall be operating at the malfunction criteria limit for the applicable 

parameter only. All other primary and secondary oxygen sensor 

parameters shall be with normal characteristics. 

(3.1.2) For vehicles utilizing sensors other than oxygen sensors for primary fuel 

control (e.g., hydrocarbon sensors, etc.), the manufacturer shall submit, 

for Executive Officer approval, a demonstration test plan for performing 

testing of all of the sensor parameters that can cause vehicle emissions to 

exceed the malfunction threshold (e.g., 1.5 times the applicable 

standards). The Executive Officer shall approve the plan if it is 

determined that it will provide data that will assure proper performance of 

the diagnostics of the sensors, consistent with the intent of section (h). 

(3.2) EGR System: The manufacturer shall perform a test at the low flow limit. 
128

(3.3) VVT System: For 2006 through 2008 model year Low Emission II applications 

and all 2009 and subsequent model year vehicles, the manufacturer shall 

perform a test at each target error limit and slow response limit calibrated to 

the malfunction criteria (e.g., 1.5 times the FTP standard) in sections 

(e)(13.2.1) and (13.2.2). In conducting the VVT system demonstration tests, 

the manufacturer may use computer modifications to cause the VVT system 

to operate at the malfunction limit if the manufacturer can demonstrate that 

the computer modifications produce test results equivalent to an induced 

hardware malfunction. 

(3.4) Fuel System: 

(3.4.1) For vehicles with adaptive feedback based on the primary fuel control 

sensor(s), the manufacturer shall perform a test with the adaptive 

feedback based on the primary fuel control sensor(s) at the rich limit(s) 

and a test at the lean limit(s) established by the manufacturer in section 

(e)(6.2.1) to detect a malfunction before emissions exceed the 

malfunction threshold (e.g., 1.5 times the applicable standards). 

(3.4.2) For vehicles with feedback based on a secondary fuel control sensor(s) 

and subject to the malfunction criteria in section (e)(6.2.1), the 

manufacturer shall perform a test with the feedback based on the 

secondary fuel control sensor(s) at the rich limit(s) and a test at the lean 

limit(s) established by the manufacturer in section (e)(6.2.1) to detect a 

malfunction before emissions exceed the malfunction threshold (e.g., 1.5 

times the applicable standards). 

(3.4.3) For other fuel metering or control systems, the manufacturer shall perform 

a test at the criteria limit(s). 

(3.4.4) For purposes of fuel system testing, the fault(s) induced may result in a 

uniform distribution of fuel and air among the cylinders. Non-uniform 

distribution of fuel and air used to induce a fault may not cause misfire. In 

conducting the fuel system demonstration tests, the manufacturer may 

use computer modifications to cause the fuel system to operate at the 

malfunction limit if the manufacturer can demonstrate that the computer 

modifications produce test results equivalent to an induced hardware 

malfunction. 

(3.5) Misfire: The manufacturer shall perform a test at the malfunction criteria limit 

specified in section (e)(3.2.2). The testing is not required for diesel 

applications. 

(3.6) Secondary Air System: The manufacturer shall perform a test at the low flow 

limit. Manufacturers performing only a functional check in accordance with 

the provisions of section (e)(5.2.2)(B) or (e)(5.2.4) shall perform a test at the 

functional check flow malfunction criteria. 

(3.7) Catalyst System: The manufacturer shall perform a test using a catalyst 

system deteriorated to the malfunction criteria using methods established by 

the manufacturer in accordance with sections (e)(1.2.6) and (1.2.7). 

(3.8) Heated Catalyst Systems: The manufacturer shall perform a test at the 

malfunction criteria limit established by the manufacturer in section (e)(2.2). 

(3.9) Other systems: The manufacturer shall conduct demonstration tests for all 

other emission control components designed and calibrated to an emission 

threshold malfunction criteria (e.g., 1.5 times any of the applicable emission 
129

standards) (e.g., hydrocarbon traps, adsorbers, etc.) under the provisions of 

section (e)(16). 

(3.10) The manufacturer may electronically simulate deteriorated components if the 

manufacturer can demonstrate to the Executive Officer that the computer 

modifications produce test results equivalent to an induced hardware 

malfunction but may not make any vehicle control unit modifications (unless 

otherwise excepted above or exempted pursuant to this section) when 

performing demonstration tests. All equipment necessary to duplicate the 

demonstration test must be made available to the ARB upon request. A 

manufacturer may request Executive Officer approval to electronically 

simulate a deteriorated component with engine control unit modifications. 

 The Executive Officer shall approve the request upon determining the 

manufacturer has submitted data and/or engineering analysis demonstrating 

that is technically infeasible, very difficult, and/or resource intensive to implant 

the fault with modifications external to the engine control unit.

(4) Required Testing for Diesel/Compression-ignition vehicles: 

Except as provided below, the manufacturer shall perform single-fault testing 

based on the applicable test with the following components/systems set at their 

malfunction criteria limits as determined by the manufacturer for meeting the 

requirements of section (f). 

(4.1) NMHC Catalyst: The manufacturer shall perform a separate test for each 

monitored NMHC catalyst(s) that is used for a different purpose (e.g., 

oxidation catalyst upstream of a PM filter, NMHC catalyst used downstream 

of an SCR catalyst). The catalyst(s) being evaluated shall be deteriorated to 

the applicable malfunction criteria established by the manufacturer in section 

(f)(1.2.2) using methods established by the manufacturer in accordance with 

section (f)(1.2.4). For each monitored NMHC catalyst(s), the manufacturer 

shall also demonstrate that the OBD II system will detect a catalyst 

malfunction with the catalyst at its maximum level of deterioration (i.e., the 

substrate(s) completely removed from the catalyst container or “empty” can). 

 Emission data are not required for the empty can demonstration. 

(4.2) NOx Catalyst: The manufacturer shall perform a separate test for each 

monitored NOx catalyst(s) that is used for a different purpose (e.g., passive 

lean NOx catalyst, SCR catalyst). The catalyst(s) being evaluated shall be 

deteriorated to the applicable malfunction criteria established by the 

manufacturer in sections (f)(2.2.2)(A) and (f)(2.2.3)(A) using methods 

established by the manufacturer in accordance with section (f)(2.2.4). For 

each monitored NOx catalyst(s), the manufacturer shall also demonstrate that 

the OBD II system will detect a catalyst malfunction with the catalyst at its 

maximum level of deterioration (i.e., the substrate(s) completely removed 

from the catalyst container or “empty” can). Emission data are not required 

for the empty can demonstration. 

(4.3) Misfire Monitoring: For 2010 and subsequent model year vehicles subject to 

section (f)(3.2.2), the manufacturer shall perform a test at the malfunction 

criteria limit specified in section (f)(3.2.2). A misfire monitor demonstration 

test is not required for vehicles not subject to section (f)(3.2.2). 

(4.4) Fuel System: The manufacturer shall perform a separate test for each 

applicable malfunction limit established by the manufacturer for the fuel 
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system parameters (e.g., fuel pressure, injection timing, injection quantity) 

specified in sections (f)(4.2.1) through (f)(4.2.3). When performing a test for 

a specific parameter, the fuel system shall be operating at the malfunction 

criteria limit for the applicable parameter only. All other parameters shall be 

with normal characteristics. In conducting the fuel system demonstration 

tests, the manufacturer may use computer modifications to cause the fuel 

system to operate at the malfunction limit if the manufacturer can 

demonstrate to the Executive Officer that the computer modifications produce 

test results equivalent to an induced hardware malfunction.

(4.5) Exhaust Gas Sensor: The manufacturer shall perform a test for each exhaust 

gas sensor parameter calibrated to the malfunction criteria in sections 

(f)(5.2.1)(A)(i), (f)(5.2.1)(B)(i), and (f)(5.2.2)(A). When performing a test, all 

exhaust gas sensors used for the same purpose (e.g., for the same feedback 

control loop, for the same control feature on parallel exhaust banks) shall be 

operating at the malfunction criteria limit for the applicable parameter only. 

All other exhaust gas sensor parameters shall be with normal characteristics. 

(4.6) EGR System: The manufacturer shall perform a test at each flow, slow 

response, and cooling limit calibrated to the malfunction criteria in sections 

(f)(6.2.1) through (f)(6.2.3) and (f)(6.2.5). In conducting the EGR cooler 

performance demonstration test, the EGR cooler(s) being evaluated shall be 

deteriorated to the applicable malfunction criteria using methods established 

by the manufacturer in accordance with section (f)(6.2.5)(C). In conducting 

the EGR system slow response demonstration tests, the manufacturer may 

use computer modifications to cause the EGR system to operate at the 

malfunction limit if the manufacturer can demonstrate to the Executive Officer 

that the computer modifications produce test results equivalent to an induced 

hardware malfunction or that there is no reasonably feasible method to 

induce a hardware malfunction. 

(4.7) Boost Pressure Control System: The manufacturer shall perform a test at 

each boost, response, and cooling limit calibrated to the malfunction criteria 

in sections (f)(7.2.1) through (f)(7.2.4). In conducting the charge air 

undercooling demonstration test, the charge air cooler(s) being evaluated 

shall be deteriorated to the applicable malfunction criteria established by the 

manufacturer in section (f)(7.2.4)(A) using methods established by the 

manufacturer in accordance with section (f)(7.2.4)(C).

(4.8) NOx Adsorber: The manufacturer shall perform a test using a NOx 

adsorber(s) deteriorated to the malfunction criteria in section (f)(8.2.1). The 

manufacturer shall also demonstrate that the OBD II system will detect a NOx 

adsorber malfunction with the NOx adsorber at its maximum level of 

deterioration (i.e., the substrate(s) completely removed from the container or 

“empty” can). Emission data are not required for the empty can 

demonstration. 

(4.9) PM Filter: The manufacturer shall perform a test using a PM filter(s) 

deteriorated to each applicable malfunction criteria in sections (f)(9.2.1), 

(f)(9.2.2), and (f)(9.2.4). The manufacturer shall also demonstrate that the 

OBD II system will detect a PM filter malfunction with the filter at its maximum 

level of deterioration (i.e., the filter(s) completely removed from the filter 

container or “empty” can). Emission data are not required for the empty can 
131

demonstration. 

(4.10) Cold Start Emission Reduction Strategy: The manufacturer shall perform a 

test at the malfunction criteria for the system or for each component 

monitored according to section (f)(12.2.2).

(4.10)(4.11) VVT System: The manufacturer shall perform a test at each target 

error limit and slow response limit calibrated to the malfunction criteria in 

sections (f)(13.2.1) and (f)(13.2.2). In conducting the VVT system 

demonstration tests, the manufacturer may use computer modifications to 

cause the VVT system to operate at the malfunction limit if the manufacturer 

can demonstrate to the Executive Officer that the computer modifications 

produce test results equivalent to an induced hardware malfunction. 

(4.11)(4.12) For each of the testing requirements of section (h)(4), if the 

manufacturer has established that only a functional check is required 

because no failure or deterioration of the specific tested system could result 

in an engine’s emissions exceeding the emission malfunction criteria, the 

manufacturer is not required to perform a demonstration test; however the 

manufacturer is required to provide the data and/or engineering analysis used 

to determine that only a functional test of the system(s) is required. 

(4.13) For each of the testing requirements of (h)(4), when performing a test, all 

components or systems used in parallel for the same purpose (e.g., separate 

VVT actuators on the intake valves for Bank 1 and Bank 2, separate NOx 

converting catalysts on parallel exhaust banks) shall be simultaneously 

deteriorated to the malfunction criteria limit. Components or systems in 

series or used for different purposes (e.g., upstream and downstream 

exhaust gas sensors in a single exhaust bank, separate high pressure and 

low pressure EGR systems) may not be simultaneously deteriorated to the 

malfunction criteria limit.

(4.14) The manufacturer may electronically simulate deteriorated components if the 

manufacturer can demonstrate to the Executive Officer that the computer 

modifications produce test results equivalent to an induced hardware 

malfunction but may not make any engine control unit modifications (unless 

otherwise provided above or exempted pursuant to this section) when 

performing demonstration tests. All equipment necessary to duplicate the 

demonstration test must be made available to ARB upon request. A 

manufacturer may request Executive Officer approval to electronically 

simulate a deteriorated component with engine control unit modifications. 

The Executive Officer shall approve the request upon determining the 

manufacturer has submitted data and/or engineering analysis demonstrating 

that it is technically infeasible, very difficult, and/or resource intensive to 

implant the fault with modifications external to the engine control unit.

(5) Testing Protocol: 

(5.1) Preconditioning: The manufacturer shall use an applicable cycle (FTP, SET, 

or Unified Cycle) for preconditioning test vehicles prior to conducting each of 

the above emission tests. Upon determining that a manufacturer has 

provided data and/or an engineering evaluation that demonstrate that 

additional preconditioning is necessary to stabilize the emission control 

system, the Executive Officer shall allow the manufacturer to perform a single 

additional preconditioning cycle, identical to the initial preconditioning cycle, 
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or a Federal Highway Fuel Economy Driving Cycle, following a ten minute (20 

minutes for medium duty engines certified on an engine dynamometer) hot 

soak after the initial preconditioning cycle. The manufacturer may not require 

the test vehicle to be cold soaked prior to conducting preconditioning cycles 

in order for the monitoring system testing to be successful. 

(5.2) Test Sequence: 

(5.2.1) The manufacturer shall set the system or component on the test vehicle 

for which detection is to be tested at the criteria limit(s) prior to conducting 

the applicable preconditioning cycle(s). If a second preconditioning cycle 

is permitted in accordance with section (h)(5.1) above, the manufacturer 

may adjust the system or component to be tested before conducting the 

second preconditioning cycle. The manufacturer may not replace, modify, 

or adjust the system or component after the last preconditioning cycle has 

taken place. 

(5.2.2) After preconditioning, the test vehicle shall be operated over the 

applicable cycle to allow for the initial detection of the tested system or 

component malfunction. This test cycle may be omitted from the testing 

protocol if it is unnecessary. If required by the designated monitoring 

strategy, a cold soak may be performed prior to conducting this driving 

cycle. 

(5.2.3) The test vehicle shall then be operated over the applicable exhaust 

emission test. If monitoring is designed to run during the Unified Cycle, a 

second Unified Cycle may be conducted prior to the exhaust emission 

test. 

(5.3) A manufacturer required to test more than one test vehicle (section (h)(2.2)) 

may utilize internal calibration sign-off test procedures (e.g., forced cool 

downs, less frequently calibrated emission analyzers, etc.) instead of official 

exhaust emission test procedures to obtain the emission test data required in 

section (h) for all but one of the required test vehicles. The manufacturer 

may elect this option if the data from the alternative test procedure are 

representative of official exhaust emission test results. Manufacturers using 

this option are still responsible for meeting the malfunction criteria specified in 

sections (e) and (f) when emission tests are performed in accordance with 

official exhaust emission test procedures. 

(5.4) For medium-duty vehicles certified to an engine dynamometer exhaust 

emission standard, a manufacturer may request Executive Officer approval to 

utilize an alternate testing protocol for demonstration of MIL illumination if the 

engine dynamometer emission test cycle does not allow all of a monitor’s 

enable conditions to be satisfied. A manufacturer may request the use of an 

alternate engine dynamometer test cycle or the use of chassis testing to 

demonstrate proper MIL illumination. In evaluating the manufacturer's 

request, the Executive Officer shall consider the technical necessity for using 

an alternate test cycle and the degree to which the alternate test cycle 

demonstrates that in-use operation with the malfunctioning component will 

properly result in MIL illumination. 

(6) Evaluation Protocol: 

(6.1) For all tests conducted under section (h), the MIL shall be illuminated upon 

detection of the tested system or component malfunction before the end of 
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the first engine start portion of the exhaust emission test (or before the hot 

start portion of the last Unified Cycle, if applicable) in accordance with 

requirements of sections (e) and (f). 

(6.2) For all tests conducted under section (h), manufacturers may use NonMethane Hydrocarbon (NMHC) emission results in lieu of Non-Methane 

Organic Gas (NMOG) emission results for comparison to the applicable 

standards or malfunction criteria (e.g., 1.5 times the FTP standards). If 

NMHC emission results are used in lieu of NMOG, the emission result shall 

be multiplied by 1.04 to generate an equivalent NMOG result before 

comparison to the applicable standards. 

(6.3) If the MIL illuminates prior to emissions exceeding the applicable malfunction 

criteria specified in sections (e) and (f), no further demonstration is required. 

With respect to the misfire monitor demonstration test, if a manufacturer has 

elected to use the minimum misfire malfunction criteria of one percent as 

allowed in sections (e)(3.2.2)(A) and (f)(3.2.2)(B), no further demonstration is 

required if the MIL illuminates with misfire implanted at the malfunction 

criteria limit. 

(6.4) If the MIL does not illuminate when the systems or components are set at 

their limit(s), the criteria limit or the OBD II system is not acceptable. 

(6.4.1) Except for testing of the catalyst (i.e., components monitored under (e)(1), 

(f)(2) or (f)(8)) or PM filter system, if the MIL first illuminates after 

emissions exceed the applicable malfunction criteria specified in sections 

(e) and (f), the test vehicle shall be retested with the tested system or 

component adjusted so that the MIL will illuminate before emissions 

exceed the applicable malfunction criteria specified in sections (e) and (f). 

 If the component cannot be adjusted to meet this criterion because a 

default fuel or emission control strategy is used when a malfunction is 

detected (e.g., open loop fuel control used after an O2 sensor malfunction 

is determined, etc.), the test vehicle shall be retested with the component 

adjusted to the worst acceptable limit (i.e., the applicable monitor 

indicates the component is performing at or slightly better than the 

malfunction criteria). For the OBD II system to be approved, the MIL must 

not illuminate during this test and the vehicle emissions must be below the 

applicable malfunction criteria specified in sections (e) and (f). 

(6.4.2) In testing the catalyst (i.e., components monitored under (e)(1), (f)(2) or 

(f)(8)) or PM filter system, if the MIL first illuminates after emissions 

exceed the applicable emission threshold(s) specified in sections (e) and 

(f), the tested vehicle shall be retested with a less deteriorated catalyst or 

PM filter system (i.e., more of the applicable engine out pollutants are 

converted or trapped). For the OBD II system to be approved, testing 

shall be continued until either of the following conditions are satisfied: 

(A) The MIL is illuminated and emissions do not exceed the thresholds 

specified in sections (e) and (f); or 

(B) The manufacturer demonstrates that the MIL illuminates within 

acceptable upper and lower limits of the threshold specified in sections (e) 

and (f) for MIL illumination. The manufacturer shall demonstrate 

acceptable limits by continuing testing until the test results show: 

(i) The MIL is illuminated and emissions exceed the thresholds specified 
134

in sections (e) and (f) by 25 percent or less of the applicable standard 

(e.g., emissions are less than 2.0 times the applicable standard for a 

malfunction criterion of 1.75 times the standard); and 

(ii) The MIL is not illuminated and emissions are below the thresholds 

specified in sections (e) and (f) by no more than 25 percent of the 

standard (e.g., emissions are between 1.5 and 1.75 times the 

applicable standard for a malfunction criterion of 1.75 times the 

standard). 

(6.5) If an OBD II system is determined unacceptable by the above criteria, the 

manufacturer may recalibrate and retest the system on the same test vehicle. 

 In such a case, the manufacturer must confirm, by retesting, that all systems 

and components that were tested prior to recalibration and are affected by 

the recalibration function properly under the OBD II system as recalibrated. 

(6.6) Where applicable for diesel vehicles, the emission test results shall be 

adjusted as required under section (d)(6.2). 

(7) Confirmatory Testing: 

(7.1) The ARB may perform confirmatory testing to verify the emission test data 

submitted by the manufacturer under the requirements of section (h) comply 

with the requirements of section (h) and the malfunction criteria identified in 

sections (e) and (f). This confirmatory testing is limited to the vehicle 

configuration represented by the demonstration vehicle(s). For purposes of 

section (h)(7), vehicle configuration shall have the same meaning as the term 

used in 40 CFR 86.082-2. 

(7.2) The ARB or its designee may install appropriately deteriorated or 

malfunctioning components in an otherwise properly functioning test vehicle 

of a test group represented by the demonstration test vehicle(s) (or simulate 

a deteriorated or malfunctioning component) in order to test any of the 

components or systems required to be tested in section (h). Upon request by 

the Executive Officer, the manufacturer shall make available a vehicle and all 

test equipment (e.g., malfunction simulators, deteriorated components, etc.) 

necessary to duplicate the manufacturer’s testing. The Executive Officer 

shall make the request within six months of reviewing and approving the 

demonstration test vehicle data submitted by the manufacturer for the 

specific test group. 

(7.3) Vehicles with OBD II systems represented by the demonstration vehicle(s) 

may be recalled for corrective action if a representative sample of vehicles 

uniformly fails to meet the requirements of section (h). 

(i) CERTIFICATION DOCUMENTATION. 

(1) When submitting an application for certification of a test group, the manufacturer 

shall submit the following documentation. If any of the items listed below are 

standardized for all of a manufacturer’s test groups, the manufacturer may, for 

each model year, submit one set of documents covering the standardized items 

for all of its test groups. 

(1.1) For the required documentation not standardized across all test groups, the 

manufacturer may propose to the Executive Officer that documentation 

covering a specified combination of test groups be used. These 

combinations shall be known as “OBD II groups”. Executive Officer approval 
135

shall be granted for those groupings that include test groups using the same 

OBD II strategies and similar calibrations. If approved by the Executive 

Officer, the manufacturer may submit one set of documentation from one or 

more representative test group(s) that are a part of the OBD II group. The 

Executive Officer shall determine whether a selected test group(s) is 

representative of the OBD II group as a whole. To be approved as 

representative, the test group(s) must possess the most stringent emission 

standards and OBD II monitoring requirements and cover all of the emission 

control devices within the OBD II group. 

(1.2) With Executive Officer approval, one or more of the documentation 

requirements of section (i) may be waived or modified if the information 

required would be redundant or unnecessarily burdensome to generate. 

(1.3) To the extent possible, the certification documentation shall use SAE J1930 

terms, abbreviations, and acronyms. 

(2) The following information shall be submitted as “Part 1” of the certification 

application. Except as provided below for demonstration data, the Executive 

Officer will not issue an Executive Order certifying the covered vehicles without 

the information having been provided. The information must include: 

(2.1) A description of the functional operation of the OBD II system including a 

complete written description for each monitoring strategy that outlines every 

step in the decision making process of the monitor. Algorithms, diagrams, 

samples of data, and/or other graphical representations of the monitoring 

strategy shall be included where necessary to adequately describe the 

information. 

(2.2) A table, in the standardized format detailed in Attachment A of ARB Mail-Out 

#95-20, May 22, 1995, incorporated by reference. 

(2.2.1) The table must include the following information for each monitored 

component or system (either computer-sensed or -controlled) of the 

emission control system: 

(A) corresponding fault code 

(B) monitoring method or procedure for malfunction detection 

(C) primary malfunction detection parameter and its type of output signal 

(D) fault criteria limits used to evaluate output signal of primary parameter 

(E) other monitored secondary parameters and conditions (in engineering 

units) necessary for malfunction detection 

(F) monitoring time length and frequency of checks 

(G) criteria for storing fault code 

(H) criteria for illuminating malfunction indicator light 

(I) criteria used for determining out of range values and input component 

rationality checks 

(2.2.2) Wherever possible, the table shall use the following engineering units: 

(A) Degrees Celsius (°C) for all temperature criteria 

(B) KiloPascals (KPa) for all pressure criteria related to manifold or 

atmospheric pressure 

(C) Grams (g) for all intake air mass criteria 

(D) Pascals (Pa) for all pressure criteria related to evaporative system vapor 

pressure 
136

(E) Miles per hour (mph) for all vehicle speed criteria 

(F) Relative percent (%) for all relative throttle position criteria (as defined in 

SAE J1979) 

(G) Voltage (V) for all absolute throttle position criteria (as defined in SAE 

J1979) 

(H) Per crankshaft revolution (/rev) for all changes per ignition event based 

criteria (e.g., g/rev instead of g/stroke or g/firing) 

(I) Per second (/sec) for all changes per time based criteria (e.g., g/sec) 

(J) Percent of nominal tank volume (%) for all fuel tank level criteria 

(2.3) A logic flowchart describing the step by step evaluation of the enable criteria 

and malfunction criteria for each monitored emission-related component or 

system. 

(2.4) Emission test data, a description of the testing sequence (e.g., the number 

and types of preconditioning cycles), approximate time (in seconds) of MIL 

illumination during the test, fault code(s) and freeze frame information stored 

at the time of detection, corresponding SAE J1979 test results (e.g. 

Mode/Service $06) stored during the test, and a description of the modified or 

deteriorated components used for fault simulation with respect to the 

demonstration tests specified in section (h). The Executive Officer may 

approve conditional certification of a test group prior to the submittal of this 

data for ARB review and approval. Factors to be considered by the Executive 

Officer in approving the late submission of information identified in section 

(i)(2.4) shall include the reason for the delay in the data collection, the length 

of time until data will be available, and the demonstrated previous success of 

the manufacturer in submitting the data prior to certification. 

(2.5) For gasoline vehicles, data supporting the misfire monitor, including: 

(2.5.1) The established percentage of misfire that can be tolerated without 

damaging the catalyst over the full range of engine speed and load 

conditions. 

(2.5.2) Data demonstrating the probability of detection of misfire events of the 

misfire monitoring system over the full engine speed and load operating 

range for the following misfire patterns: random cylinders misfiring at the 

malfunction criteria established in section (e)(3.2.2), one cylinder 

continuously misfiring, and paired cylinders continuously misfiring. 

(2.5.3) Data identifying all disablement of misfire monitoring that occurs during 

the FTP and US06 cycles. For every disablement that occurs during the 

cycles, the data should identify: when the disablement occurred relative to 

the driver’s trace, the number of engine revolutions that each disablement 

was present for, and which disable condition documented in the 

certification application caused the disablement. The data shall be 

submitted in the standardized format detailed in Attachment A: Misfire 

Disablement and Detection Chart of ARB Mail-Out #06-23, December 21, 

2006, incorporated by reference. 

(2.5.4) Manufacturers are not required to use the durability demonstration vehicle 

to collect the misfire data for sections (i)(2.5.1) though (2.5.3). 

(2.6) Data supporting the limit for the time between engine starting and attaining 

the designated heating temperature for after-start heated catalyst systems. 
137

(2.7) For diesel vehicle monitors in section (f) that are required to indicate a 

malfunction before emissions exceed an emission threshold based on any 

applicable standard (e.g., 1.5 times any of the applicable standards), the test 

cycle and standard determined by the manufacturer to be the most stringent 

for each applicable monitor in accordance with section (d)(6.1) and the 

adjustment factors determined by the manufacturer for each applicable 

monitor in accordance with section (d)(6.2).

(2.8) A listing of all electronic powertrain input and output signals (including those 

not monitored by the OBD II system) that identifies which signals are 

monitored by the OBD II system. 

(2.9) A written description of all parameters and conditions necessary to begin 

closed loop operation. 

(2.10) A summary table identifying every test group and each of the OBD II phase-in 

requirements that apply to each test group. 

(2.11) A written identification of the communication protocol utilized by each test 

group for communication with an SAE J1978 scan tool. 

(2.12) A pictorial representation or written description of the diagnostic connector 

location including any covers or labels. 

(2.13) A written description of the method used by the manufacturer to meet the 

requirements of sections (e)(9) and (f)(10) for PCV and CV system monitoring 

including diagrams or pictures of valve and/or hose connections. 

(2.14) A cover letter identifying all concerns and deficiencies applicable to the 

equivalent previous model year test group and the changes and/or resolution 

of each concern or deficiency for the current model year test group. 

(2.15) For diesel engine vehicles, a written description of each AECD utilized by the 

manufacturer including the identification of each EI-AECD relative to the data 

required to be tracked and reported in the standardized format specified in 

section (g)(6) (e.g., EI-AECD #1 is “engine overheat protection as determined 

by coolant temperature greater than...”), the sensor signals and/or calculated 

values used to invoke each AECD, the engineering data and/or analysis 

demonstrating the need for such an AECD, the actions taken when each 

AECD is activated, the expected in-use frequency of operation of each 

AECD, and the expected emission impact from each AECD activation. 

(2.16) A checklist of all the malfunction criteria in sections (e) or (f) and the 

corresponding diagnostic noted by fault code for each malfunction criterion. 

The formats of the checklists are detailed in Attachments F and G of ARB 

Mail-Out #MSC 06-23, December 21, 2006, incorporated by reference. 

(2.17) Any other information determined by the Executive Officer to be necessary to 

demonstrate compliance with the requirements of this regulation. 

(3) “Part 2”. The following information shall be submitted by January 1st of the 

applicable model year: 

(3.1) A listing and block diagram of the input parameters used to calculate or 

determine calculated load values and the input parameters used to calculate 

or determine fuel trim values. 

(3.2) A scale drawing of the MIL and the fuel cap indicator light, if present, which 

specifies location in the instrument panel, wording, color, and intensity. 
138

(4) “Part 3”. The following information shall be submitted upon request of the 

Executive Officer: 

(4.1) Data supporting the criteria used to detect a malfunction when catalyst 

deterioration causes emissions to exceed the applicable malfunction criteria 

specified in sections (e) and (f). 

(4.2) Data supporting the criteria used to detect evaporative system leaks. 

(4.3) Any other information determined by the Executive Officer to be necessary to 

demonstrate compliance with the requirements of this regulation. 

(j) PRODUCTION VEHICLE EVALUATION. TESTING. 

(1) Verification of Standardized Requirements. 

(1.1) Requirement: For 2005 and subsequent model year vehicles, manufacturers 

shall perform testing to verify that all vehicles meet the requirements of 

section (g)(3) and (g)(4) relevant to proper communication of required 

emission-related messages to an SAE J1978 scan tool. 

(1.2) Selection of Test Vehicles: Manufacturers shall perform this testing every 

model year on one production vehicle from every unique calibration within two 

months of the start of normal production for that calibration. Manufacturers 

may request Executive Officer approval to group multiple calibrations together 

and test one representative calibration per group. The Executive Officer shall 

approve the request upon finding that the software designed to comply with 

the standardization requirements of section (g) in the representative 

calibration vehicle is identical (e.g., communication protocol message timing, 

number of supported data stream parameters, etc.) to all others in the group 

and that any differences in the calibrations are not relevant with respect to 

meeting the criteria in section (j)(1.4). 

(1.3) Test Equipment: For the testing required in section (j)(1), manufacturers shall 

utilize an off-board device to conduct the testing. Prior to conducting testing, 

manufacturers are required to request and receive Executive Officer approval 

of the off-board device that the manufacturer will use to perform the testing. 

The Executive Officer shall approve the request upon determining that the 

manufacturer has submitted data, specifications, and/or engineering analysis 

that demonstrate that the off-board device meets the minimum requirements 

to conduct testing according to SAE J1699-3 using the software developed 

and maintained for the SAE J1699-3 committee and available through 

www.sourceforge.net and SAE J2534 compliant hardware configured 

specifically for SAE J1699-3 testing. 

(1.4) Required Testing (i.e., “static” testing portion of SAE J1699-3): 

(1.4.1) The testing shall verify that the vehicle can properly establish 

communications between all emission-related on-board computers and 

any SAE J1978 scan tool designed to adhere strictly to the 

communication protocols allowed in section (g)(3); 

(1.4.2) The testing shall further verify that the vehicle can properly communicate 

to any SAE J1978 scan tool: 

(A) The current readiness status from all on-board computers required to 

support readiness status in accordance with SAE J1979 and section 

(g)(4.1) while the engine is running; 
139

(B) The MIL command status while the MIL is commanded off and while the 

MIL is commanded on in accordance with SAE J1979 and section (g)(4.2) 

while the engine is running, and in accordance with SAE J1979 and 

sections (d)(2.1.2) during the MIL functional check and, if applicable, 

(g)(4.1.3) during the MIL readiness status check while the engine is off; 

(C) All data stream parameters required in section (g)(4.2) in accordance with 

SAE J1979 including the identification of each data stream parameter as 

supported in SAE J1979 (e.g., Mode/Service $01, PID $00); 

(D) The CAL ID, CVN, and VIN (if applicable) in accordance with SAE J1979 

and sections (g)(4.6) through (4.8); 

(E) An emission-related fault code (permanent, confirmed, and pending) in 

accordance with SAE J1979 (including correctly indicating the number of 

stored fault codes (e.g., Mode/Service $01, PID $01, Data A)) and section 

(g)(4.4); 

(1.4.3) The testing shall also verify that the vehicle can properly respond to any 

SAE J1978 scan tool request to clear emission-related fault codes and 

reset readiness status. 

(1.5) Reporting of Results: 

(1.5.1) The manufacturer shall notify the Executive Officer within one month of 

identifying any vehicle that does not meet the requirements of section 

(j)(1.4). The manufacturer shall submit a written report of the problem(s) 

identified and propose corrective action (if any) to remedy the problem(s) 

to the Executive Officer for approval. Factors to be considered by the 

Executive Officer in approving the proposed corrective action shall include 

the severity of the problem(s), the ability of the vehicle to be tested in an 

I/M program, the ability of service technicians to access the required 

diagnostic information, the impact on equipment and tool manufacturers, 

and the amount of time prior to implementation of the proposed corrective 

action. 

(1.5.2) Within three months of any passing testing conducted pursuant to section 

(j)(1), a manufacturer shall submit a report of the results to the Executive 

Officer for review. 

(1.5.3) In accordance with section (k)(6), manufacturers may request Executive 

Officer approval for a retroactive deficiency to be granted for items 

identified during this testing. 

(2) Verification of Monitoring Requirements. 

(2.1) For 2004 and subsequent model year vehicles, within the first six months 

after normal production begins, manufacturers shall conduct a complete 

evaluation of the OBD II system of one or more production vehicles (test 

vehicles) and submit the results of the evaluation to the Executive Officer. 

(2.2) Selection of test vehicles: 

(2.2.1) Prior to submitting any applications for certification for a model year, a 

manufacturer shall notify the Executive Officer of the test groups planned 

for that model year. The Executive Officer will then select the test 

group(s), in accordance with sections (j)(2.2.2) and (j)(2.2.3) below, that 

the manufacturer shall use as test vehicles to provide evaluation test 
140

results. This selection process may take place during durability 

demonstration test vehicle selection specified in section (h). 

(2.2.2) A manufacturer shall evaluate one production vehicle per test group 

selected for monitoring system demonstration in section (h). 

(2.2.3) In addition to the vehicles selected in section (j)(2.2.2) above, a 

manufacturer shall evaluate vehicles chosen from test groups that are not 

selected for monitoring system demonstration testing under section (h). 

The number of additional vehicles to be tested shall be equal to the 

number of vehicles selected for monitoring system demonstration in 

section (h). 

(2.2.4) The Executive Officer may waive the requirements for submittal of 

evaluation results from one or more of the test groups if data has been 

previously submitted for all of the test groups. 

(2.3) Evaluation requirements: 

(2.3.1) The evaluation shall demonstrate the ability of the OBD II system on the 

selected production vehicle to detect a malfunction, illuminate the MIL, 

and store a confirmed fault code when a malfunction is present and the 

monitoring conditions have been satisfied for each individual diagnostic 

required by title 13, CCR section 1968.2. 

(2.3.2) The evaluation shall verify that malfunctions detected by non-MIL 

illuminating diagnostics of components used to enable any other OBD II 

system diagnostic (e.g., fuel level sensor) will not inhibit the ability of other 

OBD II system diagnostics to properly detect malfunctions. 

(2.3.3) On vehicles so equipped, the evaluation shall verify that the software used 

to track the numerator and denominator for purposes of determining inuse monitoring frequency correctly increments as required in section 

(d)(4)(i.e., the “dynamic” testing portion of SAE J1699-3). 

(2.3.4) Malfunctions may be mechanically implanted or electronically simulated 

but internal on-board computer hardware or software changes may not be 

used to simulate malfunctions. Emission testing to confirm that the 

malfunction is detected before the appropriate emission standards are 

exceeded is not required. 

(2.3.5) Manufacturers shall submit a proposed test plan for Executive Officer 

approval prior to evaluation testing being performed. The test plan shall 

identify the method used to induce a malfunction in each diagnostic. If the 

Executive Officer determines that the requirements of section (j)(2) are 

satisfied, the proposed test plan shall be approved. 

(2.3.6) Subject to Executive Officer approval, manufacturers may omit 

demonstration of specific diagnostics. The Executive Officer shall 

approve a manufacturer's request if the demonstration cannot be 

reasonably performed without causing physical damage to the vehicle 

(e.g., on-board computer internal circuit faults). 

(2.3.7) For evaluation of test vehicles selected in accordance with section 

(j)(2.2.2), manufacturers are not required to demonstrate diagnostics that 

were previously demonstrated prior to certification as required in section 

(h). 
141

(2.4) Manufacturers shall submit a report of the results of all testing conducted 

pursuant to section (j)(2) to the Executive Officer for review. This report shall 

identify the method used to induce a malfunction in each diagnostic, the MIL 

illumination status, and the confirmed fault code(s) stored. 

(2.5) In accordance with section (k)(6), manufacturers may request Executive 

Officer approval for a retroactive deficiency to be granted for items identified 

during this testing. 

(3) Verification and Reporting of In-use Monitoring Performance. 

(3.1) Manufacturers are required to collect and report in-use monitoring 

performance data representative of every test group certified by the 

manufacturer and equipped with in-use monitoring performance tracking 

software in accordance with section (d)(4) to the ARB within twelve months 

from either the time vehicles in the test group were first introduced into 

commerce or the start of normal production for such vehicles, whichever is 

later. The manufacturer may propose to the Executive Officer that multiple 

test groups be combined to collect representative data. Executive Officer 

approval shall be granted upon determining that the proposed groupings 

include test groups using the same OBD II strategies and similar calibrations 

and that are expected to have similar in-use monitoring performance. If 

approved by the Executive Officer, the manufacturer may submit one set of 

data for each of the approved groupings. 

(3.2) For each test group or combination of test groups, the data must include all of 

the in-use performance tracking data reported through SAE J1979 (i.e., all 

numerators, denominators, and the ignition cycle counter), the date the data 

was collected, the odometer reading, the vehicle VIN, and the ECM software 

calibration identification number and be in the standardized format detailed in 

Attachment D: Rate Based Data of ARB Mail-Out #06-23, December 21, 

2006, incorporated by reference. 

(3.3) Manufacturers shall submit a plan to the Executive Officer for review and 

approval of the sampling method, number of vehicles to be sampled, time line 

to collect the data, and reporting format. The Executive Officer shall approve 

the plan upon determining that it provides for effective collection of data from 

a representative sample of vehicles that, at a minimum, is fifteen vehicles, will 

likely result in the collection and submittal of data within the required twelve 

month time frame, will generate data that are representative of California 

drivers and temperatures, and does not, by design, exclude or include 

specific vehicles in an attempt to collect data only from vehicles with the 

highest in-use performance ratios. 

(3.4) Upon request of the manufacturer, the Executive Officer may reduce the 

minimum sample size of fifteen vehicles set forth in section (j)(3.3) for test 

groups with low sales volume. In granting approval of a sampling plan with a 

reduced minimum sample size, the Executive Officer shall consider, among 

other things, information submitted by the manufacturer to justify the smaller 

sample size, sales volume of the test group(s), and the sampling mechanism 

utilized by the manufacturer to procure vehicles. In lieu of defining a fixed 

minimum sample size for low sales volume test groups, sampling plans 

approved for collection of data on higher sales volume test groups under 
142

section (j)(3.3) shall also be approved by the Executive Officer for low sales 

test groups if they use the identical sampling mechanism to procure vehicles 

from the low sales volume test groups. 

(k) DEFICIENCIES. 

(1) For 2004 and subsequent model year vehicles, the Executive Officer, upon 

receipt of an application from the manufacturer, may certify vehicles even though 

said vehicles may not comply with one or more of the requirements of title 13, 

CCR section 1968.2. In granting the certification, the Executive Officer shall 

consider the following factors: the extent to which the requirements of section 

1968.2 are satisfied overall based on a review of the vehicle applications in 

question, the relative performance of the resultant OBD II system compared to 

systems fully compliant with the requirements of title 13, CCR section 1968.2, 

and a demonstrated good-faith effort on the part of the manufacturer to: (1) meet 

the requirements in full by evaluating and considering the best available 

monitoring technology; and (2) come into compliance as expeditiously as 

possible. The Executive Officer may not grant certification to a vehicle in which 

the reported noncompliance for which a deficiency is sought would be subject to 

ordered recall pursuant to section 1968.5 (c)(3)(A). 

(2) Manufacturers of non-complying systems are subject to fines pursuant to section 

43016 of the California Health and Safety Code. Except as allowed in section 

(k)(7) for light-duty diesel vehicles, the specified fines apply to the third and 

subsequently identified deficiencies, with the exception that fines shall apply to 

all monitoring system deficiencies wherein a required monitoring strategy is 

completely absent from the OBD system. 

(3) The fines are in the amount of $50 per deficiency per vehicle for non-compliance 

with any of the monitoring requirements specified in sections (e)(1) through 

(e)(8), (e)(11), (e)(13)(e)(14), (e)(16), (f)(1) through (f)(9), (f)(13), and (f)(16) and 

$25 per deficiency per vehicle for non-compliance with any other requirement of 

section 1968.2. In determining the identified order of deficiencies, deficiencies 

subject to a $50 fine are identified first. Total fines per vehicle under section (k) 

may not exceed $500 per vehicle and are payable to the State Treasurer for 

deposit in the Air Pollution Control Fund. 

(4) Manufacturers must re-apply for Executive Officer approval of a deficiency each 

model year. In considering the request to carry-over a deficiency, the Executive 

Officer shall consider the factors identified in section (k)(1) including the 

manufacturer’s progress towards correcting the deficiency. The Executive 

Officer may not allow manufacturers to carry over monitoring system deficiencies 

for more than two model years unless it can be demonstrated that substantial 

vehicle hardware modifications and additional lead time beyond two years would 

be necessary to correct the deficiency, in which case the Executive Officer shall 

allow the deficiency to be carried over for three model years. 

(5) Except as allowed in section (k)(6), deficiencies may not be retroactively granted 

after certification. 
143

(6) Request for retroactive deficiencies 

(6.1) Manufacturers may request that the Executive Officer grant a deficiency and 

amend a vehicle’s certification to conform to the granting of the deficiencies 

during the first 6 months after commencement of normal production for each 

aspect of the monitoring system: (a) identified by the manufacturer (during 

testing required by section (j)(2) or any other testing) to be functioning 

different than the certified system or otherwise not meeting the requirements 

of any aspect of section 1968.2; and (b) reported to the Executive Officer. If 

the Executive Officer grants the deficiencies and amended certification, their 

approval would be retroactive to the start of production. 

(6.2) Executive Officer approval of the request for a retroactive deficiency shall be 

granted provided that the conditions necessary for a pre-certification 

deficiency determination are satisfied (see section (k)(1)) and the 

manufacturer could not have reasonably anticipated the identified problem 

before commencement of production. 

(6.3) In granting the amended certification, the Executive Officer shall include any 

approved post-production deficiencies together with all previously approved 

deficiencies in computing fines in accordance with section (k)(2). 

(7) For 2007 through 2009 model year light-duty and 2007 through 2012 model year 

medium-duty diesel vehicles, in cases where one or more of the deficiencies is 

for the aftertreatment monitoring requirements of sections (f)(1), (2), (8), or (9) 

and the deficient monitor is properly able to detect all malfunctions prior to 

emissions exceeding twice the required monitor threshold (e.g., before emissions 

exceed 10 times the standard for NMHC if the threshold is 5.0 times the 

standard for NMHC), the specified fines shall apply to the fourth and 

subsequently identified deficiencies in lieu of the third and subsequently 

identified deficiencies. If none of the deficiencies are for the requirements of 

sections (f)(1), (2), (8), or (9) or if the deficient aftertreatment monitor exceeds 

twice the required monitor threshold, the specified fines shall apply to the third 

and subsequently identified deficiencies. In all cases, the exception that fines 

shall apply to all monitoring system deficiencies wherein a required monitoring 

strategy is completely absent from the OBD system still applies. 

(8) Any OBD II system installed on a production vehicle that fails to conform with the 

certified OBD II system for that vehicle or otherwise fails to meet the 

requirements of section 1968.2 and has not been granted a deficiency pursuant 

to the provisions of section (k)(1) through (k)(7) are considered non-compliant. 

The vehicles are subject to enforcement pursuant to applicable provisions of the 

Health and Safety Code and title 13, CCR section 1968.5. 

NOTE: Authority cited: Sections 39600, 39601, 43000.5, 43013, 43018, 43100, 

43101, 43104, 43105, 43105.5, and 43106, Health and Safety Code. Reference: 

Sections 39002, 39003, 39010, 39018, 39021.5, 39024, 39024.5, 39027, 39027.3, 

39028, 39029, 39031, 39032, 39032.5, 39033, 39035, 39037.05, 39037.5, 39038, 

39039, 39040, 39042, 39042.5, 39046, 39047, 39053, 39054, 39058, 39059, 

39060,, 39515, 39600, 39601, 43000, 43000.5, 43004, 43006, 43013, 43016, 

43018, 43100, 43101, 43102, 43104, 43105, 43105.5, 43106, 43150, 43151, 
144

43152, 43153, 43154, 43155, 43156, 43204, 43211, and 43212, Health and Safety 

Code. 
1

ATTACHMENT C 

California Code of Regulations, Title 13, section 1971.5, Enforcement of 

Malfunction and Diagnostic System Requirements for 2010 and Subsequent 

Model-Year Heavy-Duty Vehicles and Engines (HD OBD) 

Set forth below is proposed new California Code of Regulations, Title 13, section 

1971.5. The proposed language is shown in plain text with major section 

headings and definition terms shown in italics.
2

§ 1971.5. Enforcement of Malfunction and Diagnostic System Requirements 

for 2010 and Subsequent Model-Year Heavy-Duty Engines. 

(a) General. 

(1) Applicability. 

(A) These procedures shall be used to assure compliance with the 

requirements of California Code of Regulations (Cal. Code Regs.), title 

13, section 1971.1 for all 2010 and subsequent model year heavy-duty 

engines equipped with OBD systems that have been certified for sale 

in California. 

(B) Engines manufactured prior to the 2010 model year are covered by the 

general enforcement and penalty provisions of the Health and Safety 

Code, and the specific provisions of Cal. Code Regs., title 13, section 

1971 and section 2111 through section 2149. 

(2) Purpose. 

The purpose of this section is to establish the enforcement protocol that 

shall be used by the Air Resources Board (ARB) to assure that engines 

certified for sale in California are equipped with OBD systems that 

properly function and meet the purposes and requirements of Cal. Code 

Regs., title 13, section 1971.1. 

(3) Definitions. 

The definitions applicable to these rules include those set forth in Health 

and Safety Code section 39010 et seq. and in Cal. Code Regs., title 13, 

section 1900(b) and section 1971.1(c), which are incorporated by 

reference herein. The following definitions are specifically applicable to 

section 1971.5 and take precedence over any contrary definitions. 

“Days”, when computing any period of time, unless otherwise noted, 

means normal working days that a manufacturer is open for business. 

“Engine Class” means a group or set of engines subject to 

enforcement testing that have been determined by the Executive Officer to 

share common or similar hardware, software, OBD monitoring strategy, or 

emission control strategy. 

“Engine Manufacturer” means the manufacturer granted certification to 

sell engines in the State of California. 

“Executive Officer” means the Executive Officer of ARB or his or her 

authorized representative. 

“Influenced OBD-Related Recall” means an inspection, repair, 

adjustment, or modification program initiated and conducted by a 

manufacturer as a result of enforcement testing conducted by the ARB or 

any other information for the purpose of correcting any nonconforming 

OBD system for which direct notification of vehicle or engine owners is 

necessary. 

“Major Monitor” means those monitors covered by the requirements set 

forth in Cal. Code Regs., title 13, section 1971.1(e), (f), and (g)(4). 

 “Nonconforming OBD System” means an OBD system on a 

production engine that has been determined not to comply with the 
3

requirements of Cal. Code Regs., title 13, section 1971.1. For purposes of 

section 1971.5, an engine class shall be considered nonconforming 

irrespective of whether engines in the engine class, on average, meet 

applicable tailpipe or evaporative emission standards. 

“OBD Emission Testing” refers to testing conducted to determine 

compliance with the malfunction criteria in Cal. Code Regs., title 13, 

section 1971.1(e) through (g) that are based on a multiple of, or an 

additive to, a tailpipe emission standard or an absolute measurement from 

an applicable emission test cycle (e.g., 1.5 times the applicable federal 

test procedure (FTP) emission standards, PM standard plus 0.02 g/bhp-hr, 

PM level of 0.03 g/bhp-hr as measure from an applicable emission test 

cycle). 

“OBD Ratio Testing” refers to testing conducted to determine 

compliance with the required in-use monitor performance ratio in Cal. 

Code Regs., title 13, section 1971.1(d)(3.2.2). 

“Ordered OBD-Related Recall” means an inspection, repair, 

adjustment, or modification program required by ARB to be conducted by 

the manufacturer to correct any nonconforming OBD system for which 

direct notification of vehicle or engine owners is necessary. 

“Quarterly Reports” refer to the following calendar periods: January 1 – 

March 31; April 1 – June 30; July 1 – September 30; October 1 – 

December 31. 

“Test Sample Group” means a group of production engines in a 

designated engine class that are equipped with OBD systems and are 

selected and tested as part of the enforcement testing program set forth in 

sections (b) and (c). 

“Voluntary OBD-Related Recall” means an inspection, repair, 

adjustment, or modification program voluntarily initiated and conducted by 

a manufacturer to correct any nonconforming OBD system for which direct 

notification of vehicle or engine owners is necessary. 

(b) Testing Procedures for ARB-Conducted Testing. 

(1) Purpose. 

To assure that OBD systems on production engines comply with the 

requirements of Cal. Code Regs., title 13, section 1971.1, ARB may 

periodically evaluate engines from an engine class.

(2) Preliminary Testing and Evaluation. 

(A) As part of his or her evaluation of engines to determine compliance 

with the requirements of Cal. Code Regs., title 13, section 1971.1, the 

Executive Officer may routinely conduct testing on any production 

engines that have been certified for sale in California. 

(B) Based upon such testing or any other information, including data from 

California or other state heavy duty inspection programs, warranty 

information reports, and field information reports, the Executive Officer 

may conduct enforcement testing pursuant to sections (b)(3) through 

(5) below. 
4

(3) Engine Selection for ARB-Conducted Enforcement Testing. 

(A) Determining the Engine Class. 

(i) Upon deciding to conduct enforcement testing, the Executive Officer 

shall determine the engine class to be tested. In determining the 

scope of the engine class to be tested, the Executive Officer shall 

consider the similarities and differences in the OBD systems of 

potentially affected engines. Among other things, the Executive 

Officer shall consider whether engines share similar computer 

hardware and software, calibrations, or OBD monitoring and 

emission control strategies. 

(ii) The default engine class is the engine family or OBD group used by 

the manufacturer to certify the engines to be tested. However, 

upon concluding that a subgroup of engines differs from other 

engines in the identified engine family or OBD group and that a 

reasonable basis exists to believe that the differences may directly 

impact the type of testing that will be performed, the Executive 

Officer may determine that a subgroup of the engine family or OBD 

group is the appropriate engine class for testing. 

(iii) Similarly, upon concluding that engines from several engine 

families or OBD groups (which may include engine families or OBD 

groups from different model years) share such common 

characteristics that a reasonable basis exists to believe that results 

of enforcement testing may be applicable to an engine class larger 

than a specific engine family or OBD group, the Executive Officer 

may determine that the appropriate engine class includes more 

than one engine family or OBD group. 

(iv) Except for testing to determine if an OBD system has been 

designed to deactivate based on age and/or mileage (Cal. Code 

Regs., title 13, section 1971.1(d)(1.3)), the Executive Officer may 

not conduct testing of an engine class whose engines, on average, 

exceed the defined full useful life of the engine class. For purposes 

of the determination of this average, the Executive Officer shall use 

the accrual rates appropriate for engines in the engine class 

considering the vehicle weight class, usage type, and other 

subcategories as defined and used by EMFAC2007, which is 

incorporated by reference herein.

(B) Size of Test Sample Group. 

After determining the engine class to be tested, the Executive Officer 

shall determine the appropriate number of engines to include in the 

test sample group for enforcement testing in accordance with the 

following guidelines: 

(i) For OBD emission testing, the Executive Officer shall follow the 

provisions of Cal. Code Regs., title 13, section 2137 regarding test 

sample size. In accordance with section 2137, the Executive 

Officer shall test 10 engines that have been procured following the 

protocol of section (b)(3)(C) below and meet the selection criteria of 
5

section (b)(3)(D)(i) below to determine the emissions characteristics 

of the engine class being tested.

(ii) For OBD ratio testing, the Executive Officer shall collect data from a 

test sample group of 30 engines that have been procured following 

the protocol of section (b)(3)(C) below and meet the selection 

criteria of section (b)(3)(D)(ii) below to determine the in-use OBD 

monitoring performance of the engine class being tested. 

(iii) In determining compliance with any other requirements of Cal. 

Code Regs., title 13, section 1971.1 (e.g., diagnostic connector 

location, communication protocol standards, MIL illumination 

protocol, evaporative system diagnostics, etc.), the Executive 

Officer shall determine, on a case by case basis, the number of 

engines meeting the selection criteria of section (b)(3)(D)(iii) 

needed to assure that the results of such testing may be 

reasonably inferred to the engine class. The Executive Officer’s 

determination shall be based upon the nature of the

nonconformance and the scope of the engine class. The test 

sample group could be as few as two test engines. 

(C) Protocol for Procuring Engines for Test Sample Group. 

(i) For OBD emission and ratio testing, the Executive Officer shall 

determine the appropriate manner for procuring engines. In making 

his or her determination, the Executive Officer shall consider the 

nature of the nonconformance and the scope of the engine class. 

The method used shall ensure that engines are recruited from more 

than one source. Methods used may include obtaining lists of 

engine owners from specific sources (e.g., engine manufacturers, 

motor vehicle registration records) and soliciting participation from 

owners, discussing with fleet or rental operations to locate engines 

in the engine class, or using methods used by the manufacturer to 

procure engines for the manufacturer-run heavy duty diesel in-use 

testing program established pursuant to 70 Federal Register 34594 

procure engines consistent with the procurement process followed 

by the Executive Officer under Cal. Code Regs., title 13, section 

2137 (e.g., obtaining lists of all vehicles in the motor vehicle class 

within a specified geographical area, mailing postcards soliciting 

participation of vehicles within the specified area, selecting vehicles 

from those that responded to the solicitation, inspecting selected 

vehicles to determine whether appropriate to include in sample 

group, etc.). In selecting engines for OBD emission testing, the 

Executive Officer shall include only engines meeting the criteria set 

forth in section (b)(3)(D)(i) below. For OBD ratio testing, the 

Executive Officer shall include only engines meeting the criteria set 

forth in section (b)(3)(D)(ii) below. 

(ii) For all other testing, the Executive Officer shall, on a case by case 

basis, determine the appropriate manner for procuring engines. In 

making his or her determination, the Executive Officer shall 
6

consider the nature of the nonconformance and the scope of the 

engine class. The Executive Officer may procure engine(s) by any 

means that assures effective collection and testing of engines (e.g., 

rental car agencies, fleet vehicles, etc.), but shall not include any 

vehicle for which a reasonable basis exists that a vehicle operator’s 

driving or maintenance habits would substantially impact test 

results to determine nonconformance. In all cases, however, the 

selection process must ensure proper selection of engines in 

accord with section (b)(3)(D)(iii) below. 

(D) Engines to be included in a Test Sample Group. 

(i) In selecting engines to be included in a test sample group for 

enforcement OBD emission testing, the Executive Officer shall 

include only engines that: 

a. Are certified to the requirements of Cal. Code Regs., title 13, 

section 1971.1 and California exhaust emission standards. 

b. Are registered for operation in the United States. 

c. Have mileage that is less than 75 percent of the certified full 

useful life mileage and have an age of less than the certified full 

useful life age for the subject vehicles. 

d. Have not been tampered with or equipped with add-on or 

modified parts that would cause the OBD system not to comply 

with the requirements of Cal. Code Regs., title 13, section 

1971.1 or would have a permanent effect on exhaust emission 

performance 

e. Have not been subjected to abuse (e.g., racing, overloading, 

misfueling), neglect, improper maintenance, or other factors that 

would cause the OBD system not to comply with the 

requirements of Cal. Code Regs., title 13, section 1971.1 or 

would have a permanent effect on exhaust emission 

performance.

f. Have no detected or known malfunction(s) unrelated to the 

monitor or system being evaluated that would affect the 

performance of the OBD system. At its discretion, ARB may 

elect to repair an engine with a detected or known malfunction 

and then include the engine in the test sample group. 

g. Have had no major repair to the engine resulting from a 

collision. 

h. Have no problem that might jeopardize the safety of laboratory 

personnel. 

(ii) In selecting engines to be included in a test sample group for 

enforcement OBD ratio testing, the Executive Officer shall include 

only engines that: 

a. Are certified to the requirements of Cal. Code Regs., title 13, 

section 1971.1. 

b. Have collected sufficient engine operation data for the monitor 

to be tested. For monitors required to meet the in-use monitor 
7

performance ratio and to track and report ratio data pursuant to 

Cal. Code Regs., title 13, section 1971.1(d)(3.2), sufficient 

engine operation data shall mean the denominator meets the 

criteria set forth in sections (b)(3)(D)(ii)1. through 5. below. For 

monitors required to meet the in-use monitor performance ratio 

but not required to track and report ratio data pursuant to Cal. 

Code Regs., title 13, section 1971.1(d)(3.2), sufficient engine 

operation data shall mean that engines that have a denominator 

that meets the criteria set forth in sections (b)(3)(D)(ii)1. through 

5. below after undergoing testing as set forth in section 

(b)(4)(C)(ii) below. Specifically, the denominator, as defined in 

Cal. Code Regs., title 13, section 1971.1(d)(4.3), for the monitor 

to be tested must have a value equal to or greater than: 

1. 150 for gasoline evaporative system and secondary air 

system monitors, and gasoline monitors utilizing a 

denominator incremented in accordance with Cal. Code 

Regs., title 13, section 1971.1(d)(4.3.2)(D), (E), and (F) (e.g., 

cold start monitors, variable valve timing and/or control 

system monitors, etc.), or 

2. 300 for gasoline catalyst, oxygen sensor, EGR, and all other 

component monitors. 

3. 50 for diesel PM filter and NMHC converting catalyst 

monitors, and other diesel monitors using a denominator 

incremented in accordance with Cal. Code Regs., title 13, 

section 1971.1(d)(4.3.2)(G) or (H), or 

4. 150 for diesel monitors utilizing a denominator incremented 

in accordance with Cal. Code Regs., title 13, section 

1971.1(d)(4.3.2)(D), (E), or (F) (e.g., cold start monitors, 

comprehensive component output component monitors, 

etc.), or 

5. 300 for all other diesel monitors not covered under sections 

(b)(3)(D)(ii)3. and 4. above. 

c. Have not been tampered with or equipped with add-on or 

modified parts that would cause the OBD system not to comply 

with the requirements of Cal. Code Regs., title 13, section 

1971.1. 

d. Have mileage and age that are less than or equal to the certified 

full useful life mileage and age for the subject engines. 

(iii) In selecting engines to be included in a test sample group for 

enforcement testing of any other requirement of Cal. Code Regs., 

title 13, section 1971.1 (not covered by sections (b)(3)(D)(i) or (ii) 

above), the Executive Officer shall include only engines that: 

a. Are certified to the requirements of Cal. Code Regs., title 13, 

section 1971.1. 

b. Have not been tampered with or equipped with add-on or 

modified parts that would cause the OBD system not to comply 
8

with the requirements of Cal. Code Regs., title 13, section 

1971.1. 

c. Have no detected or known malfunction(s) unrelated to the 

monitor or system being evaluated that would affect the 

performance of the OBD system. At its discretion, ARB may 

elect to repair an engine with a detected or known malfunction 

and then include the engine in the test sample group. 

d. Have mileage and age that are less than or equal to the certified 

full useful life mileage and age for the subject engines. 

(iv) If the Executive Officer discovers, by either evidence presented by 

the manufacturer as provided in section (b)(7) or on his or her own, 

that an engine fails to meet one or more of the applicable criteria of 

section (b)(3)(D)(i) through (iii), the Executive Officer shall remove 

the engine from the test sample group. The Executive Officer may 

replace any engine removed with an additional engine selected in 

accordance with sections (b)(3)(C) and (D) above. Test results 

relying on data from the removed engine shall be recalculated 

without using the data from the removed engine. 

(4) Enforcement Testing Procedures. 

(A) Prior to conducting any testing under section (b)(4), the Executive 

Officer may replace components monitored by the OBD system with 

components that are sufficiently deteriorated or simulated to cause 

malfunctions that exceed the malfunction criteria established pursuant 

to Cal. Code Regs., title 13, section 1971.1(e) through (g) in a properly 

operating system. The Executive Officer may not use components 

deteriorated or simulated to represent failure modes that could not 

have been foreseen to occur by the manufacturer (e.g., the use of 

leaded gasoline in an unleaded gasoline engine, etc.). Upon request 

by the Executive Officer, the manufacturer shall make available all test 

equipment used by the manufacturer in development, calibration, or 

demonstration testing (e.g., malfunction simulators, deteriorated 

“threshold” components, etc.) necessary to duplicate testing done by 

the manufacturer to determine the malfunction criteria used for major 

monitors subject to OBD emission testing. 

(B) OBD Emission Testing. After the test sample group has been selected 

and procured, the Executive Officer may perform one or more of the 

following tests: 

(i) Emission testing with the test procedures used by the Executive 

Officer for in-use testing of compliance with exhaust emission 

standards in accordance with Cal. Code Regs., title 13, section 

1956.8(b) and (d). 

(ii) On-road or engine or chassis dynamometer testing with the engine 

being operated in a manner that reasonably ensures that all of the 

monitoring conditions disclosed in the manufacturer's certification 

application for the tested monitor are encountered.

(C) OBD Ratio Testing. 
9

(i) For OBD ratio testing of monitors required to meet the in-use 

monitor performance ratio and track and report ratio data pursuant 

to Cal. Code Regs., title 13, section 1971.1(d)(3.2), after the test 

sample group has been selected and procured, the Executive 

Officer shall download the data from monitors required to track and 

report such data. 

(ii) For OBD ratio testing of monitors required to meet the in-use 

monitor performance ratio but not required to track and report ratio 

data pursuant to Cal. Code Regs., title 13, section 1971.1(d)(3.2), 

after the test sample group has been selected and procured, the 

Executive Officer shall collect data by installing instrumentation or 

data-logging equipment on the engines/vehicles. After installation 

of the equipment, the engines/vehicles shall be returned to the 

engine/vehicle owner/operator to continue to operate the 

engine/vehicle until the minimum denominator criteria (see section 

(b)(3)(D)(ii)b.) are satisfied. The Executive Officer shall then 

calculate the ratio from the data collected in accordance with the 

requirements of Cal. Code Regs., title 13, section 1971.1(d)(3.2) to 

allow the Executive Officer to effectively determine the in-use 

monitor performance ratio. 

(D) Testing for compliance with any other requirement of Cal. Code Regs., 

title 13, section 1971.1. After the test sample group has been selected 

and procured, the Executive Officer may perform one or more of the 

following tests: 

(i) Emission testing on the applicable FTP or supplemental emission 

test (SET) cycle or other applicable emission test cycle used for 

measuring exhaust or evaporative emissions; 

(ii) On-road or engine or chassis dynamometer testing with the engine 

being operated in a manner that reasonably ensures that all of the 

monitoring conditions disclosed in the manufacturer's certification 

application for the tested monitor are encountered; or 

(iii) Any other testing determined to be necessary by the Executive 

Officer. This may include, but is not limited to, the use of special 

test equipment to verify compliance with standardization 

requirements. 

(5) Additional Testing. 

(A) Based upon testing of the engine class in section (b)(4) above and 

after review of all evidence available at the conclusion of such testing, 

the Executive Officer may elect to conduct further testing of a subgroup 

of engines from the engine class if the Executive Officer has 

determined that: 

(i) A subgroup of tested engines differs sufficiently enough from other 

engines in the tested engine class, and 

(ii) A reasonable basis exists to believe that the identified differences 

may indicate that the subgroup may be nonconforming whereas the 

tested engine class as a whole is not. 
10

(B) Hereinafter all references to engine class shall be applicable to the 

subgroup meeting the conditions of section (b)(5)(A) above. 

(C) In any testing of a subgroup of engines under section (b)(5), the 

Executive Officer shall follow the engine selection and testing 

procedures set forth in sections (b)(3) and (4) above. 

(6) Finding of Nonconformance after Enforcement Testing. 

After conducting enforcement testing pursuant to section (b)(4) above, the 

Executive Officer shall make a finding of nonconformance of the OBD 

system in the identified engine class under the respective tests for the 

applicable model year(s) as follows: 

(A) OBD Emission Testing. 

(i) For 2010 through 2012 model year engines: 

a. Engines certified as an OBD parent rating (i.e., the engine 

rating subject to the “full OBD” requirement under Cal. Code 

Regs., title 13, section 1971.1(d)(7.1.1)), shall be considered 

nonconforming if the emission test results indicate that 50 

percent or more of the engines in the test sample group do not 

properly illuminate the MIL when emissions exceed 2.0 times 

the malfunction criteria (e.g., 5.0 times the standard if the 

malfunction criterion is 2.5 times the standard) on the applicable 

standard (i.e., FTP or SET). 

b. In determining an engine to be nonconforming, the Executive 

Officer shall use: 

1. The test cycle and standard determined and identified by the 

manufacturer at the time of certification in accordance with 

Cal. Code Regs., title 13, section 1971.1(d)(6.1) as the most 

stringent for purposes of determining OBD system 

nonconformance with the applicable standard in section 

(b)(6)(A)(i)a. and 

2.The adjustment factors determined by the manufacturer at the 

time of certification in accordance with Cal. Code Regs., title 

13, section 1971.1(d)(6.2) for purposes of determining OBD 

system nonconformance in section (b)(6)(A)(i)a. 

c. Engines certified as an OBD child rating (i.e., the engine ratings 

subject to the “extrapolated OBD” requirement under Cal. Code 

Regs., title 13, section 1971.1(d)(7.1.2)), may not be considered 

nonconforming based on testing emission levels. 

(ii) For 2013 through 2015 model year engines: 

a. All engines classified as OBD parent and child ratings subject to 

Cal. Code Regs., title 13, section 1971.1(d)(7.2.2) shall be 

considered to be nonconforming if the emission test results 

indicate that 50 percent or more of the engines in the test 

sample group do not properly illuminate the MIL when 

emissions exceed 2.0 times the malfunction criteria (e.g., 4.0 

times the standard if the malfunction criterion is 2.0 times the 

standard) on the applicable standard (i.e., FTP or SET). 
11

b. In determining compliance, the Executive Officer shall use only 

the test cycle and standard determined and identified by the 

manufacturer at the time of certification in accordance with Cal. 

Code Regs., title 13, section 1971.1(d)(6.1) as the most 

stringent for purposes of determining OBD system 

nonconformance with the applicable standard in section 

(b)(6)(A)(ii)a. 

c. All other engines and engine ratings may not be considered 

nonconforming based on the emission levels of the tests. 

(iii) For 2016 through 2018 model year engines: 

a. PM filter monitors on engines subject to the malfunction criteria 

of Cal. Code Regs., title 13, section 1971.1(e)(8.2.1)(C) shall be 

considered to be nonconforming if the emission test results 

indicate that 50 percent or more of the engines in the test 

sample group do not properly illuminate the MIL when 

emissions exceed 2.0 times the malfunction criteria (e.g., PM 

emission level of 0.06 g/bhp-hr if the malfunction criterion is 

0.03 g/bhp-hr) on either of the applicable standards (i.e., FTP or 

SET). 

b. Monitors on engines and engine ratings previously certified to 

Cal. Code Regs., title 13, section 1971.1(d)(7.2.3) for 

extrapolated OBD in the 2013 through 2015 model years shall 

be considered nonconforming if the emission test results 

indicate that 50 percent or more of the engines in the test 

sample group do not properly illuminate the MIL when 

emissions exceed 2.0 times the malfunction criteria (e.g., 4.0 

times the standard if the malfunction criterion is 2.0 times the 

standard) on either of the applicable standards (i.e., FTP or 

SET). 

c. Monitors on engines not covered under sections (b)(6)(A)(iii)a. 

and b. above shall be considered nonconforming if the emission 

test results indicate that 50 percent or more of the engines in 

the test sample group do not properly illuminate the MIL when 

emissions exceed the malfunction criteria on either of the 

applicable standards (i.e., FTP or SET). 

(iv) For 2019 and subsequent model year engines, any engine shall be 

considered nonconforming if the results of the tests indicate that 50 

percent or more of the engines in the test sample do not properly 

illuminate the MIL when emissions exceed the malfunction criteria 

on either of the applicable standards (i.e., FTP or SET). 

(v) The Executive Officer may not consider an OBD system 

nonconforming solely due to a failure or deterioration mode of a 

monitored component or system that could not have been 

reasonably foreseen to occur by the manufacturer. 

(B) OBD Ratio Testing. 
12

(i) 2013 through 2015 model year engines certified to a ratio of 0.100 in 

accordance with Cal. Code Regs., title 13, section 1971.1(d)(3.2.2) 

shall be considered nonconforming if the data collected from the 

engines in the test sample group indicate either that the average inuse monitor performance ratio for one or more of the monitors in 

the test sample group is less than 0.050 or that 66.0 percent or 

more of the engines in the test sample group have an in-use 

monitor performance ratio of less than 0.050 for the same monitor. 

(ii) 2016 and subsequent model year engines certified to a ratio of 

0.100 in accordance with Cal. Code Regs., title 13, section 

1971.1(d)(3.2.2) shall be considered nonconforming if the data 

collected from the engines in the test sample group indicate either 

that the average in-use monitor performance ratio for one or more 

of the monitors in the test sample group is less than 0.088 or that 

66.0 percent or more of the engines in the test sample group have 

an in-use monitor performance ratio of less than 0.100 for the same 

monitor. 

(C) All Other OBD Testing. 

(i) Engines shall be considered nonconforming if the results of the 

testing indicate that at least 30 percent of the engines in the test 

sample group do not comply with the same requirement of Cal. 

Code Regs., title 13, section 1971.1. 

(ii) Engines shall be considered nonconforming if the results of the 

testing indicate that at least 30 percent of the engines in the test 

sample group do not comply with one or more of the requirements 

of Cal. Code Regs., title 13, section 1971.1 while the engine is 

running and while in the key on, engine off position such that offboard equipment designed to access the following parameters via 

the standards referenced in Cal. Code Regs., title 13, section 

1971.1 for 2013 and subsequent model year engines cannot obtain 

valid and correct data for the following parameters: 

a. The current readiness status from all on-board computers 

required to support readiness status in accordance with Society 

of Automotive Engineers J1979 (SAE J1979) or J1939 (SAE 

J1939) as incorporated by reference in Cal. Code Regs., title 

13, section 1971.1(h)(1) and section 1971.1(h)(4.1); 

b. The current MIL command status while the MIL is commanded 

off and while the MIL is commanded on in accordance with SAE 

J1979/J1939 and Cal. Code Regs., title 13, section 

1971.1(h)(4.2), and in accordance with SAE J1979/J1939 and 

Cal. Code Regs., title 13, section 1971.1(d)(2.1.2) during the 

MIL functional check and, if applicable Cal. Code Regs., title 13, 

section 1971.1(h)(4.1.3) during the MIL readiness status check; 

c. The current permanent fault code(s) in accordance with SAE 

J1979/J1939 and Cal. Code Regs., title 13, section 

1971.1(h)(4.4); 
13

d. The data stream parameters for: engine speed and OBD 

requirements to which the engine is certified as required in Cal. 

Code Regs., title 13, section 1971.1(h)(4.2) and in accordance 

with SAE J1979/J1939; 

e. The CAL ID, CVN, ESN, and VIN as required in Cal. Code 

Regs., title 13, sections 1971.1(h)(4.6), (h)(4.7), and (h)(4.8) 

and in accordance with SAE J1979/J1939; or 

f. The proper identification of all data identified in (b)(6)(C)(ii)a. 

through (b)(6)(C)(ii)e. as supported or unsupported as required 

in Cal. Code Regs., title 13, section 1971.1(h)(4) and in 

accordance with SAE J1979/J1939. 

(iii) If the finding of nonconformance under section (b)(6)(C)(i) above 

concerns engines that do not comply with the requirements of Cal. 

Code Regs., title 13, section 1971.1(d)(4) or (5) (e.g., numerators 

or denominators are not properly being incremented), it shall be 

presumed that the nonconformance would result in an OBD ratio 

enforcement test result that would be subject to an ordered OBDrelated recall in accord with the criterion in section (d)(3)(A)(i). The 

manufacturer may rebut such a presumption by presenting 

evidence in accord with section (b)(7)(C)(iii) below that 

demonstrates to the satisfaction of the Executive Officer that the 

identified nonconformance would not result in an ordered OBDrelated recall under section (d)(3)(A)(i). 

(7) Executive Officer Notification to the Manufacturer Regarding 

Determination of Nonconformance. 

(A) Upon making the determination of nonconformance in section (b)(6) 

above, the Executive Officer shall notify the manufacturer in writing. 

(B) The Executive Officer shall include in the notice: 

(i) a description of each group or set of engines in the engine class 

covered by the determination; 

(ii) the factual basis for the determination, including a summary of the 

test results relied upon for the determination; 

(iii) a statement that the Executive Officer shall provide to the 

manufacturer, upon request and consistent with the California 

Public Records Act, Government Code section 6250 et seq., all 

records material to the Executive Officer’s determination; 

(iv) a provision allowing the manufacturer no less than 90 days from 

the date of issuance of the notice to provide the Executive Officer 

with any information contesting the findings set forth in the notice; 

and 

(v) a statement that if a final determination is made that the engine 

class is equipped with a nonconforming OBD system, the 

manufacturer may be subject to appropriate remedial action, 

including recall and monetary penalties. 

(C) Within the time period set by the Executive Officer in section 

(b)(7)(B)(iv) and any extensions of time granted under section 
14

(b)(7)(H), the manufacturer shall provide the Executive Officer, 

consistent with paragraphs (i) through (iii) below, with any test results, 

data, or other information derived from engine testing that may rebut or 

mitigate the results of ARB testing, including any evidence that an 

engine class, if determined to be nonconforming, should be exempted 

from mandatory recall. (See section (d)(3)(B) below.). 

(i) For OBD emission testing and OBD ratio testing:

a. The manufacturer may submit evidence to demonstrate that 

engines in the test sample group used by the Executive Officer 

were inappropriately selected, procured, or tested in support of 

a request to have engines excluded from the test sample group 

in accordance with section (b)(3)(D)(iv). 

b. If the manufacturer elects to conduct additional testing of 

engines in the engine class and submit the results of such 

testing to the Executive Officer, the manufacturer shall: 

1. Present evidence that it has followed the procurement and 

test procedures set forth in sections (b)(3) and (4) above, or 

2. If the manufacturer elects to use different procurement and 

testing procedures, submit a detailed description of the 

procedures used and evidence that such procedures provide 

an equivalent level of assurance that the results are 

representative of the engine class. 

(ii) If the manufacturer objects to the size of the test sample group or 

the method used to procure engines in the test sample group used 

by the Executive Officer pursuant to section (b)(3)(B)(iii) or 

(b)(3)(C)(ii), the manufacturer shall set forth what it considers to be 

the appropriate size and procurement method, the reasons 

therefore, and test data from engines that confirm the 

manufacturer’s position. 

(iii) If the manufacturer elects to present evidence to overcome the 

presumption of nonconformance in section (b)(6)(C)(iii) above, the 

manufacturer shall demonstrate that the engines in the engine 

class comply with in-use monitor performance ratio requirements of 

Cal. Code Regs., title 13, section 1971.1(d)(3.2) by presenting: 

a. Evidence in accord with the procurement and testing 

requirements of sections (b)(3) and (4). 

b. Any other evidence that provides an equivalent level of proof 

that engines operated in California comply with the in-use 

monitor performance ratio requirements. 

(D) The Executive Officer may accept any information submitted by a 

manufacturer pursuant to section (b)(7)(C) above after the time 

established for submission of such information has passed if the 

manufacturer could not have reasonably foreseen the need for 

providing the information within the time period provided. Otherwise, 

the Executive Officer is not required to accept late information. In 

determining whether to accept late information, the Executive Officer 
15

will consider the lateness of the submission, the manufacturer’s 

reasons for why such information was not timely presented, the 

materiality of the information to the Executive Officer’s final 

determination, and what effect any delay may have on effective 

enforcement and the health and welfare of the State. 

(E) The requirements of section (b)(7) shall not be construed to abridge 

the manufacturer’s right to assert any privilege or right provided under 

California law. 

(F) After receipt of any information submitted by the manufacturer 

pursuant to section (b)(7)(C) above, the Executive Officer shall 

consider all information submitted by the manufacturer and may 

conduct any additional testing that he or she believes is necessary. 

(G) Final Determination. 

(i) Within 60 days after completing any additional testing that the 

Executive Officer deemed necessary under section (b)(7)(F) above, 

the Executive Officer shall notify the manufacturer of his or her final 

determination regarding the finding of nonconformity of the OBD 

system in the engine class. The determination shall be made after 

considering all of the information collected and received, including 

all information that has been received from the manufacturer. 

(ii) The notice must include a description of each engine family(ies), 

OBD group(s), or subgroups thereof, that has been determined to 

have a nonconforming OBD system and set forth the factual bases 

for the determination. 

(H) Extensions. The Executive Officer may for good cause extend the time 

requirements set forth in section (b)(7). In granting additional time to a 

manufacturer, the Executive Officer shall consider, among other things, 

any documentation submitted by the manufacturer regarding the time 

that it reasonably believes is necessary to conduct its own testing, why 

such information could not have been more expeditiously presented, 

and what effect any delay caused by granting the extension may have 

on effective enforcement and the health and welfare of the State. The 

Executive Officer shall grant a manufacturer a reasonable extension of 

time upon the manufacturer demonstrating that despite the exercise of 

reasonable diligence, the manufacturer has been unable to produce 

relevant evidence in the time initially provided. 

(c) Manufacturer Self-Testing. 

(1) Purpose. 

To assure that OBD systems on production engines certified on an engine 

dynamometer are able to detect a fault before emissions exceed the 

malfunction criteria established in Cal. Code Regs., title 13, sections 

1971.1(e) through (g), engine manufacturers shall evaluate engines for 

each model year, starting with the 2010 model year.
16

(2) Engine Selection for Manufacturer Self-Testing. 

(A) After OBD certification of all engines in the model year, a manufacturer 

shall submit a listing to the Executive Officer of all of the engine 

families and engine ratings within each family certified for that model 

year. The Executive Officer will then select the engine family(ies) and 

the specific engine rating within the engine family(ies) that the 

manufacturer shall use as a test engine for the test sample group to 

provide emission test data. 

(i) For 2013 through 2015 model year engines, the Executive Officer 

may not select engines from OBD child ratings subject to 

“extrapolated OBD” under Cal. Code Regs., title 13, section 

1971.1(d)(7.2.3). 

(B) Number of test engines. 

(i) For the 2010 model year, a manufacturer shall provide emission test 

data of a test engine from the OBD parent rating. 

(ii) For the 2013 and subsequent model years, a manufacturer 

certifying one to five engine families in a model year shall provide 

emission test data of a test engine from one engine rating. A 

manufacturer certifying six to ten engine families in a model year 

shall provide emission test data from test engines from two engine 

ratings. A manufacturer certifying eleven or more engine families in 

a model year shall provide emission test data of test engines from 

three engine ratings. The Executive Officer may waive the 

requirement for submittal of data of one or more of the test engines 

if data have been previously submitted for all of the engine ratings. 

(C) Engines to be included in test sample group. 

(i) In selecting engines to be included in a test sample group for 

manufacturer self-testing, the manufacturer shall include only 

engines that: 

a. Are certified to the requirements of Cal. Code Regs., title 13, 

section 1971.1 and California exhaust emission standards. 

b. Are used in vehicles registered for operation in the United 

States. 

c. Have mileage that is between 70 to 80 percent of the certified 

full useful life mileage and an age of less than the certified full 

useful life age for the subject engines. 

d. Have not been tampered with or equipped with add-on or 

modified parts that would cause the OBD system not to comply 

with the requirements of Cal. Code Regs., title 13, section 

1971.1 or would have a permanent effect on exhaust emission 

performance. 

e. Have not been subjected to abuse (e.g., overloading, 

misfueling) neglect, improper maintenance, or other factors that 

would cause the OBD system not to comply with the 

requirements of Cal. Code Regs., title 13, section 1971.1 or 
17

would have a permanent effect on exhaust emission 

performance.

f. Have no detected or known malfunction(s) unrelated to the 

monitor or system being evaluated that would affect the 

performance of the OBD system. With request to and approval 

from the Executive Officer, the manufacturer may elect to repair 

an engine with a detected or known malfunction and then 

include the engine in the test sample group. 

g. Have had no major repair to the engine resulting from a 

collision. 

h. Have no problem that might jeopardize the safety of laboratory 

personnel. 

(ii) If the manufacturer discovers, by either evidence presented by the 

Executive Officer or on its own, that an engine fails to meet one or 

more of the applicable criteria of section (c)(2)(C)(i), the 

manufacturer shall notify the Executive Officer of its findings and 

request approval to remove the engine from the test sample group. 

If approved by the Executive Officer, the manufacturer shall replace 

any engine removed with an additional engine selected in 

accordance with section (c)(2)(C)(i). Test results relying on data 

from the removed engine shall be recalculated without using the 

data from the removed engine. 

(3) Compliance/Enforcement Testing Procedures. 

(A) Within three calendar years after the model year of the engine (e.g., by 

the end of calendar year 2013 for a 2010 model year engine), the 

engine manufacturer shall complete the testing required under section 

(c)(3). 

(B) Prior to conducting any testing under section (c)(3), the engine 

manufacturer shall replace components monitored by the OBD system 

with components that are sufficiently deteriorated or simulated to 

cause malfunctions that exceed the malfunction criteria established 

pursuant to Cal. Code Regs., title 13, sections 1971.1(e) through (g) in 

a properly operating system. The engine manufacturer may not use 

components deteriorated or simulated to represent failure modes that 

could not have been foreseen to occur by the manufacturer (e.g., the 

use of leaded gasoline in an unleaded engine, etc.). 

(C) After the test engine(s) has been selected and procured under section 

(c)(2) above, the engine manufacturer shall perform emission testing 

for all applicable components/systems according to the certification 

demonstration testing requirements of Cal. Code Regs., title 13, 

sections 1971.1(i)(3) and (i)(4). 

(D) No modifications or replacement of components to make the engine 

compatible with engine dynamometer testing (e.g., replacement of an 

air-to-air charge cooler with a water-to-air charge cooler) shall be done 

without approval by the Executive Officer. The Executive Officer shall 

approve such requests upon the manufacturer documenting the 
18

technical need for such a modification or replacement and providing 

engineering data or analysis demonstrating that any such modified part 

will be configured to simulate the current performance of the actual 

part removed from the engine (e.g., the water-to-air cooler must be 

configured to perform similarly to the air-to-air cooler in its current state 

of aging/deterioration, not to the performance specifications of the airto-air cooler when new or to the manufacturer’s specifications or 

performance characteristics used on the water-to-air cooler when the 

engine was originally certified). 

(E) Upon request of the manufacturer, the Executive Officer may extend 

the deadline set forth in section (c)(3)(A) or reduce the minimum 

mileage required in section (c)(2)(C)(i)c. upon finding that the 

manufacturer has demonstrated good cause for the requested 

extension or mileage reduction. 

(F) Upon request of the manufacturer, the Executive Officer may approve 

other compliance/enforcement testing protocols for (c)(3). The 

Executive Officer shall approve the request upon the manufacturer 

demonstrating that other testing protocol will provide comparable 

assurance that the in-use engines comply with the malfunction criteria 

established pursuant to Cal. Code Regs., title 13, sections 1971.1(e) 

through (g). 

(4) Additional Testing. 

(A) If the results of the OBD emission tests conducted under section (c)(3) 

indicate that the OBD system properly illuminates the MIL for all 

component/system monitors before emissions exceed the malfunction 

criteria defined in Cal. Code Regs., title 13, sections 1971.1(e) through 

(g), no further testing is required. 

(B) If the results of the OBD emission tests conducted under section (c)(3) 

indicate that OBD system does not properly illuminate the MIL for one 

or more of the component/system monitor(s) before emissions exceed 

the malfunction criteria defined in Cal. Code Regs., title 13, sections 

1971.1(e) through (g), the engine manufacturer shall conduct further 

testing on additional engines. 

(i) Within six months after the completion of testing required in section 

(c)(3), the engine manufacturer shall emission test an additional 

four engines from the same engine rating and engine family as the 

test engine. 

(ii) The engine manufacturer shall only be required to test the 

component/system monitor(s) for which the OBD emission test 

results in (b)(3) exceeded the malfunction criteria defined in Cal. 

Code Regs., title 13, sections 1971.1(e) through (g). 

(C) For manufacturers subject to section (c)(4)(B) above, no further testing 

is required if the results of the OBD emission tests conducted under 

section (c)(4)(B) indicate that OBD system properly illuminates the MIL 

for the tested component/system monitor(s) before emissions exceed 
19

the malfunction criteria defined in Cal. Code Regs., title 13, sections 

1971.1(e) through (g) on three or more of the additional test engines. 

(D) For manufacturers subject to section (c)(4)(B) above, if the results of 

the OBD emission tests conducted under section (c)(4)(B) indicate that 

the OBD system does not properly illuminate the MIL for one or more 

of the tested component/system monitor(s) before emissions exceed 

the malfunction criteria defined in Cal. Code Regs., title 13, sections 

1971.1(e) through (g) on two or more of the additional test engines, the 

engine manufacturer shall conduct further testing. 

(i) Within six months after the completion of testing required in section 

(c)(4)(B), the engine manufacturer shall test an additional five 

engines from the same engine rating and engine family as the 

previously tested engines. 

(ii) The engine manufacturer shall test only the component/system 

monitor(s) for which the OBD emission test results exceeded the 

malfunction criteria defined in Cal. Code Regs., title 13, sections 

1971.1(e) through (g). 

(E) In any testing of the additional engines under section (c)(4), the engine 

manufacturer shall follow the engine selection and testing procedures 

set forth in sections (c)(2) and (c)(3) above. 

(5) ARB Authority to Observe Testing. The Executive Officer may elect to 

have ARB personnel observe the testing under sections (c)(3) and (c)(4) 

above. 

(A) During conducting of the test procedures described in sections (c)(3) 

and (c)(4) above, an engine manufacturer, upon receipt of prior notice, 

must admit or cause to be admitted during operating hours any ARB 

personnel that has presented proper credentials to any of the following: 

(i) Any facility where tests or procedures or activities connected with 

such tests or procedures are performed; 

(ii) Any facility where a manufacturer procures, inspects, screens, 

removes from vehicles, works on, configures, or modifies engines 

for testing; and 

(iii) Any facility where any record or other document relating to any of 

the above is located. 

(B) Upon admission to any facility referred to in section (c)(5)(A) above, 

any ARB personnel must be allowed to: 

(i) Inspect and monitor any part or aspect of such procedures, 

activities, and testing facilities, including monitoring engine 

preconditioning, emissions tests, and break-in, maintenance, and 

engine storage procedures; 

(ii) Verify correlation or calibration of test equipment; 

(iii) Inspect and make copies of any such records, designs, or other 

documents; and 

(iv) Inspect and/or photograph any part or aspect of any such tested 

engine and any components or equipment used in the testing 

thereof. 
20

(C) Any ARB personnel must be furnished by those in charge of a facility 

being inspected with such reasonable assistance as may be necessary 

to discharge any function listed in section (c)(5)(B) above. The engine 

manufacturer is required to cause those in charge of a facility operated 

for its benefit to furnish such reasonable assistance without charge to 

ARB irrespective of whether or not the engine manufacturer controls 

the facility. 

(D) The duty to admit or cause to be admitted any ARB personnel applies 

whether or not the engine manufacturer owns or controls the facility in 

question and applies both to the domestic and foreign engine 

manufacturers and facilities. If ARB personnel are prohibited from 

admission, the Executive Officer may reject any data produced by the 

manufacturer and may presume that the tested engines do not 

conform to certification standards. In such circumstances, the 

Executive Officer may suspend or revoke the engine’s certification or 

take other necessary corrective action. 

(E) For purposes of section (c)(5): 

(i) “Presentation of credentials” means a display of a document 

designating a person as an ARB employee. 

(ii) Where engine, component, or engine storage areas or facilities are 

concerned, “operating hours” means all times during which 

employees are at work in the vicinity of the area or facility and have 

access to it. 

(iii) Where facilities or areas other than those covered by paragraph 

(c)(5)(E)(ii) above are concerned, “operating hours” means all times 

during which an assembly line is in operation or during which 

testing, maintenance, break-in procedure, production or compilation 

of records, or any other procedure or activity is being conducted 

related to certification testing, translation of designs from the test 

stage to the production stage, or engine manufacture or assembly. 

(iv) “Reasonable assistance” includes providing clerical, copying, 

interpretation and translation services, making personnel available 

upon request to inform ARB personnel of how the facility operates 

and to answer questions, and performing requested emissions test 

on any engine that is being, has been, or will be used for 

certification testing. Such tests must be nondestructive, but may 

require appropriate break-in. Upon service of a written request 

from the Executive Officer for the appearance of any employee at a 

facility qualified for reasonable assistance, the engine manufacturer 

shall cause the personal appearance of such qualified employee to 

appear before and assist ARB personnel. 

(6) Manufacturer Reporting of Self-Testing Results to the Executive Officer. 

(A) Within 30 days after completing the testing under section (c)(3), the 

manufacturer shall submit a report of the results of all the testing to the 

Executive Officer for review. If further testing is required under section 

(c)(4), an additional report shall be submitted within 30 days of 
21

completing the additional testing. The report(s) must include the 

following: 

(i) A description of each test engine and the engine family and engine 

rating to which the test engine belongs to; 

(ii) A description of the test sequence (e.g., the number and types of 

preconditioning cycles) used for each testing; 

(iii) A description of the modified or deteriorated components used for 

fault simulation with respect to each testing; and 

(iv) The test results of all testing done under sections (c)(3) and (c)(4) 

for each test engine, consisting of: 

a. the weighted emission test results for all measured pollutants for 

each test; and 

b. the OBD data specified by Cal. Code Regs., title 13, section 

1971.1(i)(4.3.2) collected prior to (or immediately after) each 

engine shut-down during the testing of sections (c)(3) and (c)(4) 

including the preconditioning cycles. 

(7) Finding of Nonconformance after Manufacturer Self-Testing. 

After the engine manufacturer has conducted testing pursuant to sections 

(c)(3) and (c)(4) and the Executive Officer has received the test results 

pursuant to section (c)(6) above, the Executive Officer shall make a 

finding of nonconformance of the OBD system in the engine class 

according to the criteria of section (b)(6)(A). 

(8) Executive Officer Notification to the Manufacturer Regarding 

Determination of Nonconformance. 

Upon making the determination of nonconformance in section (c)(7) 

above, the Executive Officer shall follow the procedures and requirements 

of section (b)(7). 

(d) Remedial Action. 

(1) Voluntary OBD-Related Recalls. 

If a manufacturer initiates a voluntary OBD-related recall campaign, the 

manufacturer shall notify the Executive Officer of the recall at least 45 

days before owner notification is to begin. The manufacturer shall also 

submit a voluntary OBD-related recall plan for approval, as prescribed 

under section (e)(1) below. A voluntary recall plan shall be deemed 

approved unless disapproved by the Executive Officer within 30 days after 

receipt of the recall plan. 

(2) Influenced OBD-Related Recalls. 

(A) Upon being notified by the Executive Officer, pursuant to section 

(b)(7)(G), that an engine class is equipped with a nonconforming OBD 

system, the manufacturer may, within 45 days from the date of service 

of such notification, elect to conduct an influenced OBD-related recall 

of all engines within the engine class for the purpose of correcting the 

nonconforming OBD systems. Upon such an election, the 

manufacturer shall submit an influenced OBD-related recall plan for 

approval, as prescribed under section (e)(1) below.
22

(B) If a manufacturer does not elect to conduct an influenced OBD-related 

recall under section (d)(2)(A) above, the Executive Officer may order 

the manufacturer to undertake appropriate remedial action, up to and 

including the recall and repair of the nonconforming OBD systems. 

(3) Ordered Remedial Action-Mandatory Recall. 

(A) Except as provided in sections (d)(3)(B) below, the Executive Officer 

shall order the recall and repair of all engines in an engine class that 

have been determined to be equipped with a nonconforming OBD 

system if enforcement testing conducted pursuant to sections (b) or (c) 

above or information received from the manufacturer indicates that: 

(i) For major monitors required to meet the in-use performance ratio 

pursuant to Cal. Code Regs., title 13, section 1971.1(d)(3.2) on 

2016 and subsequent model year engines, the average in-use 

monitor performance ratio for one or more of the major monitors in 

the test sample group is less than or equal to 33.0 percent of the 

applicable required minimum ratio established in Cal. Code Regs., 

title 13, section 1968.2(d)(3.2.2) (e.g., if the required ratio is 0.100, 

less than or equal to a ratio of 0.033) or 66.0 percent or more of the 

vehicles in the test sample group have an in-use monitor 

performance ratio of less than or equal to 33.0 percent of the 

applicable required minimum ratio established in Cal. Code Regs., 

title 13, section 1968.2(d)(3.2.2) for the same major monitor. 

(ii) For major monitors required to indicate a malfunction before 

emissions exceed a certain emission threshold, when the engine is 

tested in a vehicle and operated so as to reasonably encounter all 

monitoring conditions disclosed in the manufacturer’s certification 

application, the OBD system is unable to detect and illuminate the 

MIL for a malfunction of a component/system monitored by the 

major monitor prior to emissions exceeding: 

a. For 2013 through 2015 model year OBD parent and child 

ratings subject to the “full OBD” requirement under Cal. Code 

Regs., title 13, section 1971.1(d)(7.2.2), three times the 

applicable major monitor malfunction criteria (e.g., if the 

malfunction criteria is 2.5 times the applicable standard, recall 

would be required when emissions exceed 7.5 times the 

applicable standard, or if the malfunction criteria is the PM 

standard plus 0.02 g/bhp-hr and the PM standard is 0.01 g/bhphr, recall would be required when emissions exceeded 0.09 gbhp-hr). 

b. For 2016 through 2018 model year engines: 

1. For engine ratings previously certified to Cal. Code Regs., 

title 13, section 1971.1(d)(7.2.3) for “extrapolated OBD” in 

the 2013 through 2015 model years, three times the 

applicable major monitor malfunction criteria (e.g., if the 

malfunction criteria is 2.5 times the applicable standard, 

recall would be required when emissions exceed 7.5 times 
23

the applicable standard, or if the malfunction criteria is the 

PM standard plus 0.02 g/bhp-hr and the PM standard is 0.01 

g/bhp-hr, recall would be required when emissions exceeded 

0.09 g-bhp-hr), and 

2. For all other engine ratings, three times the malfunction 

criteria for PM filter monitors subject to Cal. Code Regs., title 

13, section 1971.1(e)(8.2.1)(C) (e.g., if the malfunction 

criteria is the PM standard plus 0.02 g/bhp-hr and the PM 

standard is 0.01 g/bhp-hr, recall would be required when 

emissions exceeded 0.09 g-bhp-hr) and two times the

malfunction criteria for all other applicable major monitors. 

c. For 2019 and subsequent model year engines, two times the 

applicable major monitor malfunction criteria (e.g., if the 

malfunction criteria is 2.5 times the applicable standards, recall 

would be required when emissions exceed 5.0 times the 

applicable standards). 

(iii) For 2016 and subsequent model year gasoline engines, the 

monitor for misfire causing catalyst damage is unable to properly 

detect and illuminate the MIL for misfire rates that are more than 20 

percentage points greater than the misfire rates disclosed by the 

manufacturer in its certification application as causing catalyst 

damage (e.g., if the disclosed misfire rate is 12 percent, recall 

would be required if the misfire rate is greater than 32 percent 

without proper detection). 

(iv) For 2016 and subsequent model year gasoline engines, when the 

engine is tested in a vehicle and operated so as to reasonably 

encounter all monitoring conditions disclosed in the manufacturer’s 

certification application, the evaporative system monitor is unable to 

detect and illuminate the MIL for a cumulative leak or leaks in the 

evaporative system equivalent to that caused by an orifice with a 

diameter of at least 1.5 times the diameter of the required orifice in 

Cal. Code Regs., title 13, section 1971.1(f)(7.2.2)(B). 

(v) When the engine is tested in a vehicle and operated so as to 

reasonably encounter all monitoring conditions disclosed in the 

manufacturer’s certification application, the OBD system cannot 

detect and illuminate the MIL for a malfunction of a component that 

effectively disables a major monitor and the major monitor, by being 

disabled, meets the criteria for recall identified in sections 

(d)(3)(A)(ii) or (iv) above (e.g. is unable to detect and illuminate the 

MIL for malfunctions that cause FTP emissions to exceed two times 

the malfunction criteria). 

(vi) The engine class cannot be tested so as to obtain valid test results 

in accordance with the criteria identified in section (b)(6)(C)(ii) due 

to the nonconforming OBD II system. 
24

(B) An engine class shall not be subject to mandatory recall if the 

Executive Officer determines that, even though a monitor meets a 

criterion set forth in section (d)(3)(A)(i)-(vi) for mandatory recall: 

(i) The OBD system can still detect and illuminate the MIL for all 

malfunctions monitored by the nonconforming monitor (e.g., 

monitor “A” is non-functional but monitor “B” is able to detect all 

malfunctions of the component(s) monitored by monitor “A”). 

(ii) The monitor meets the criterion solely due to a failure or 

deterioration mode of a monitored component or system that could 

not have been reasonably foreseen to occur by the manufacturer. 

(iii) The failure or deterioration of the monitored component or system 

that cannot be properly detected causes the engine to be 

unoperable (e.g., engine stalls continuously or the transmission will 

not shift out of first gear, etc.) or causes an overt indication such 

that the operator is certain to respond and have the problem 

corrected (e.g., illumination of an over-temperature warning light or 

charging system light that uncorrected will result in an undriveable 

vehicle, etc.). 

(C) A motor vehicle class that is not subject to mandatory recall pursuant 

to paragraph (d)(3)(B) may still be subject to remedial action pursuant 

to section (d)(4) below. 

(4) Other Ordered Remedial Action. 

(A) If the Executive Officer has determined based upon enforcement 

testing conducted pursuant to sections (b) or (c) above or information 

received from the manufacturer that an engine class is equipped with a 

nonconforming OBD system and the nonconformance does not fall 

within the provisions of section (d)(3), he or she may require the 

manufacturer to undertake remedial action up to and including recall of 

the affected engine class. 

(B) In making his or her findings regarding remedial action, the Executive 

Officer shall consider the capability of the OBD system to properly 

function. This determination shall be based upon consideration of all 

relevant circumstances including, but not limited to, those set forth 

below. 

(i) Whether the manufacturer identified and informed ARB about the 

nonconformance(s) or whether ARB identified the 

nonconformance(s) prior to being informed by the manufacturer. 

(ii) The number of nonconformances. 

(iii) If the identified nonconformance(s) is with a major monitor(s), the 

nature and extent of the nonconformance(s), including: 

a. the degree to which the in-use monitor performance ratio(s) is 

below the required ratio(s) specified in Cal. Code Regs., title 13, 

section 1971.1(d)(3.2.2), and 

b. the amount of the emission exceedance(s) over the established 

malfunction criteria set forth in Cal. Code Regs., title 13, 
25

sections 1971.1(e) through (g) before a malfunction is detected 

and the MIL is illuminated. 

(iv) If the identified nonconformance(s) is with a non-major monitor, the 

nature and extent of the nonconformance(s), including: 

a. the degree to which the in-use monitor performance ratio(s) 

(where applicable) is below the required ratio(s) specified in Cal. 

Code Regs., title 13, section 1971.1(d)(3.2.2), 

b. the degree to which the monitored component must be 

malfunctioning or exceed the established malfunction criteria set 

forth in Cal. Code Regs., title 13, sections 1971.1(e) through (g) 

before a malfunction is detected and the MIL is illuminated, and 

c. the effect that the nonconformance(s) has on the operation of a 

major monitor(s). 

(v) The impact of the nonconformance on vehicle or engine owners 

(e.g., cost of future repairs, driveability, etc.) and the ability of the 

service and repair industry to make effective repairs (e.g., difficulty 

in accessing fault information, diagnosing the root cause of a 

failure, etc.). 

(vi) The degree to which the identified nonconformance(s) complicates, 

interferes with, disrupts, or hampers a service technician’s or 

inspector’s ability to perform a California heavy-duty vehicle or 

engine inspection. 

(vii) The failure of the data link connector of the engine class to meet 

the requirements of Cal. Code Regs., title 13, section 1971.1(h)(2). 

(viii) The failure of the crankcase ventilation system in the engine class 

to comply with the requirements of Cal. Code Regs., title 13, 

section 1971.1(g)(2). 

(ix) The failure of the cooling system monitor in the engine class to 

properly verify that the cooling system reaches the highest enable 

temperature used for any other monitor when the engine is 

operated in a vehicle in the monitoring conditions disclosed in the 

manufacturer's certification application, or failure to comply with any 

requirement in Cal. Code Regs., title 13, section 1971.1(g)(1). 

(x) The estimated frequency that a monitor detects a malfunction and 

illuminates the MIL when no component malfunction is present (i.e., 

false MILs). 

(xi) The estimated frequency that a monitor fails to detect a malfunction 

and illuminate the MIL when the monitoring conditions, as set forth 

in the manufacturer’s approved certification application, have been 

satisfied and a faulty or deteriorated monitored component is 

present (i.e., false passes). 

(xii) Whether the manufacturer submitted false, inaccurate, or 

incomplete documentation regarding the identified nonconformance 

at the time of certification pursuant to Cal. Code Regs., title 13, 

section 1971.1(j) and the extent to which the false, inaccurate, or 
26

incomplete documentation was material to the granting of 

certification. 

(C) In making the determination, the average tailpipe and evaporative 

emissions of engines within the affected engine class shall not be 

considered. 

(5) Assessment of Monetary Penalties. 

The Executive Officer may seek penalties pursuant to the applicable 

provisions of the Health and Safety Code for violations of the requirements 

of Cal. Code Regs., title 13, section 1971.1 or for production engines 

otherwise failing to be equipped with OBD systems that have been 

certified by ARB. In determining the penalty amounts that ARB may seek, 

the Executive Officer shall consider all relevant circumstances including 

the factors set forth below: 

(A) Whether the manufacturer self-reported the nonconformity or ARB 

discovered the nonconformity independent of the manufacturer. 

(B) The nature and degree of the nonconformity and whether the 

manufacturer should reasonably have discovered the nonconformity 

and taken corrective action by voluntary OBD-related recall or running 

changes during the production year. 

(C) The economic benefits, if any, gained by the manufacturer from not 

complying with the provisions of Cal. Code Regs., title 13, section 

1971.1. 

(D) The manufacturer’s history of compliance with the OBD requirements. 

(E) The preventative efforts taken by the manufacturer to avoid 

nonconformance, including any programs followed by the manufacturer 

to ensure compliance. 

(F) The manufacturer’s efforts to correct the nonconformity once it was 

identified. 

(G) The innovative nature and magnitude of effort, including the cost of any 

other proposed remedial action, necessary to correct the 

nonconformity. 

(H) The deterrent effect of the penalty. 

(I) Whether the manufacturer has failed to provide complete and accurate 

information required to be submitted at the time of certification 

pursuant to Cal. Code Regs., title 13, section 1971.1(j). 

(J) The nature and degree that OBD systems on production engines differ 

from the systems that have been certified by ARB. 

(6) Notice to Manufacturer for an Ordered Remedial Action. 

(A) The Executive Officer shall immediately notify the manufacturer upon 

the Executive Officer determining the type of remedial action to be 

taken. 

(B) For remedial actions other than the assessment of monetary penalties, 

the notice must: 

(i) specifically set forth the remedial action that is being ordered, 
27

(ii) include a description of the engine family(ies), OBD group(s), or 

subgroup(s) thereof, that has been determined to have a 

nonconforming OBD system, 

(iii) set forth the factual bases for the determination, and 

(iv) designate a date at least 45 days from the date of receipt of such 

notice by which the manufacturer shall submit a plan, pursuant to 

section (e)(1) below, outlining the remedial action to be undertaken 

consistent with the Executive Officer’s order. Except as provided in 

section (d)(7)(C) below, all plans shall be submitted to the Chief, 

Mobile Source Operations Division, 9528 Telstar Avenue, Suite 4, 

El Monte, California 91731, within the time limit specified in the 

notice. The Executive Officer may grant the manufacturer an 

extension of time for good cause. 

(C) For cases in which ARB elects to seek monetary penalties pursuant to 

authority granted under the Health and Safety Code, the Executive 

Officer shall issue a notice to the manufacturer that he or she will be 

filing a complaint in the appropriate administrative or civil court forum 

seeking penalties against the manufacturer for violations of Cal. Code 

Regs., title 13, section 1971.1. The notice must include a description 

of the engine family(ies), OBD group(s), or subgroup(s) thereof, that 

have been determined to have a nonconforming OBD system and set 

forth the factual bases for the determination. 

(7) Availability of Public Hearing to Contest Remedial Actions Other than 

Determination to Seek Monetary Penalties. 

(A) Within 45 days from the date of receipt of the notice that is required 

under section (d)(6) above, the manufacturer may request a public 

hearing pursuant to the procedures set forth in Cal. Code Regs., title 

17, section 60055.1, et seq., to contest the findings of nonconformity, 

the necessity for, or the scope of any ordered remedial action. 

Pursuant to those procedures, the Executive Officer has the initial 

burden of presenting evidence that those parts of the Executive 

Officer’s determination specifically challenged are supported by the 

facts and applicable law. (Cal. Code Regs., title 17, §60055.32(d)(1).) 

Each issue of controversy shall be decided based upon the 

preponderance of the evidence presented at the hearing. (Cal. Code 

Regs., title 17, §60055.32(h).) 

(B) Notwithstanding the provisions of Cal. Code Regs., title 17, section 

60055.17(a)(1), administrative hearings conducted pursuant to a 

request filed under section (c)(7)(A) above shall be referred to the 

Office of Administrative Hearings, which shall otherwise follow the 

procedures established in Cal. Code Regs., title 17, section 60055.1 et 

seq. 

(C) If a manufacturer requests a public hearing pursuant to section 

(d)(7)(A) above and if the Executive Officer’s determination of 

nonconformity is confirmed at the hearing, the manufacturer shall 
28

submit the required remedial action plan in accordance with section 

(e)(1) below within 30 days after receipt of the Board’s decision. 

(e) Requirements for Implementing Remedial Actions. 

(1) Remedial Action Plans. 

(A) A manufacturer initiating a remedial action (voluntary, influenced, or 

ordered), other than payment of monetary penalties, shall develop a 

remedial action plan that contains the following information, unless 

otherwise specified: 

(i) A description of each engine family, OBD group, or subgroup 

thereof covered by the remedial action, including the number of 

engines, the engine families, or subgroups within the identified 

class(es), the make(s), model(s), and model years of the covered 

engines, and such other information as may be required to identify 

the covered engines. 

(ii) A description of the nonconforming OBD system and, in the case of 

a recall (whether voluntary, influenced, or ordered), the specific 

modifications, alterations, repairs, adjustments, or other changes to 

correct the nonconforming OBD system, including data and/or 

engineering evaluation supporting the specific corrections. 

(iii) A description of the method that the manufacturer will use to 

determine the names and addresses of vehicle or engine owners 

and the manufacturer’s method and schedule for notifying the 

service facilities and vehicle or engine owners of the remedial 

action. 

(iv) A copy of all instructions that the manufacturer will use to notify 

service facilities about the required remedial action and the specific 

corrections, if any, that will be required to be made to the 

nonconforming OBD systems. 

(v) A description of the procedure to be followed by vehicle/engine 

owners to obtain remedial action for the nonconforming OBD 

system. This must include the date on or after which the owner can 

have required remedial action performed, the time reasonably 

necessary to perform the labor to remedy the nonconformity, and 

the designation of facilities at which the nonconformity can be 

remedied. 

(vi) If some or all of the nonconforming OBD systems are to be 

remedied by persons other than dealers or authorized warranty 

agents of the manufacturer, a description of such class of service 

agents and what steps, including a copy of all instructions mailed to 

such service agents, the manufacturer will take to assure that such 

agents are prepared and equipped to perform the proposed 

remedial action. 

(vii) A copy of the letter of notification to be sent to vehicle or engine 

owners. 
29

(viii) A proposed schedule for implementing the remedial action, 

including identified increments of progress towards full 

implementation. 

(ix) A description of the method that the manufacturer will use to 

assure that an adequate supply of parts will be available to initiate 

the remedial action campaign on the date set by the manufacturer 

and that an adequate supply of parts will continue to be available 

throughout the campaign. 

(x) A description and test data of the emission impact, if any, that the 

proposed remedial action may cause to a representative engine 

from the engine class to be remedied. 

(xi) A description of the impact, if any, and supporting data and/or 

engineering evaluation that the proposed remedial action will have 

on fuel economy, driveability, performance, and safety of the 

engine class covered by the remedial action. 

(xii) Any other information, reports, or data which the Executive Officer 

may reasonably determine to be necessary to evaluate the 

remedial action plan. 

(B) Approval and Implementation of Remedial Action Plans. 

(i) If the Executive Officer finds that the remedial action plan is 

designed effectively to address the required remedial action and 

complies with the provisions in section (e)(1)(A) above, he or she 

shall notify the manufacturer in writing within 30 days of receipt of 

the plan that the plan has been approved. 

(ii) The Executive Officer shall approve a voluntary, influenced, or 

ordered remedial action plan if the plan contains the information 

specified in section (e)(1)(A) above and is designed to notify the 

vehicle or engine owner and implement the remedial action in an 

expeditious manner. 

(iii) In disapproving an ordered remedial action plan, the Executive 

Officer shall notify the manufacturer in writing of the disapproval 

and the reasons for the determination. The manufacturer shall 

resubmit a revised remedial action plan that fully addresses the 

reasons for the Executive Officer’s disapproval within 10 days of 

receipt of the disapproval notice. 

(iv) Upon receipt of the approval notice of the ordered remedial action 

plan from the Executive Officer, the manufacturer shall, within 45 

days of receipt of the notice, begin to notify vehicle or engine 

owners and implement the remedial action campaign. 

(v) If the Executive Officer disapproves a voluntary or influenced 

remedial action plan, the manufacturer shall either accept the 

proposed modifications to the plan as suggested by the Executive 

Officer, resubmit a revised remedial action plan that fully addresses 

the reasons for the Executive Officer’s disapproval within 30 days 

or be subject to an Executive Officer order that the manufacturer 
30

undertake appropriate remedial action pursuant to section (d)(2)(B) 

above. 

(vi) Upon receipt of the voluntary or influenced remedial action 

approval notice from the Executive Officer, the manufacturer shall 

begin to notify vehicle or engine owners and implement the 

remedial action campaign according to the schedule indicated in 

the remedial action plan. 

(2) Eligibility for Remedial Action. 

(A) The manufacturer may not condition a vehicle or engine owner’s 

eligibility for remedial action required under section 1971.5 on the 

proper maintenance or use of the engine. 

(B) The manufacturer shall not be obligated to repair a component which 

has been modified or altered such that the remedial action cannot be 

performed without additional cost. 

(3) Notice to Owners. 

(A) The manufacturer shall notify owners of vehicles or engines in the 

engine class covered by the remedial order. The notice must be made 

by first-class mail or by such other means as approved by the 

Executive Officer. When necessary, the Executive Officer may require 

the use of certified mail for ordered remedial actions to assure effective 

notification. 

(B) The manufacturer shall use all reasonable means necessary to locate 

vehicle or engine owners, including motor vehicle registration lists 

available from the California Department of Motor Vehicles and 

commercial sources such as R.L. Polk & Co. 

(C) The notice must contain the following: 

(i) For ordered remedial actions, a statement: “The California Air 

Resources Board has determined that your (vehicle or engine) (is 

or may be) equipped with an improperly functioning on-board 

emission-related diagnostic system that violates established 

standards and regulations that were adopted to protect your health 

and welfare from the dangers of air pollution.” 

(ii) For voluntary and influenced remedial actions, a statement: “Your 

(vehicle or engine) (is or may be) equipped with an improperly 

functioning on-board emission-related diagnostic system that 

violates (California or California and Federal) standards and 

regulations” if applicable as determined by the Executive Officer. 

(iii) A statement that the nonconformity of any such engines will be 

remedied at the expense of the manufacturer. 

(iv) A statement that eligibility for remedial action may not be denied 

solely on the basis that the vehicle or engine owner used parts not 

manufactured by the original equipment engine manufacturer, or 

had repairs performed by outlets other than the engine 

manufacturer’s franchised dealers. 

(v) Instructions to the vehicle or engine owners on how to obtain 

remedial action, including instructions on whom to contact (i.e., a 
31

description of the facilities where the vehicles or engines should be 

taken for the remedial action), the first date that a vehicle or engine 

may be brought in for remedial action, and the time that it will 

reasonably take to correct the nonconformity. 

(vi) The statement: “In order to assure your full protection under the 

emission warranty provisions, it is recommended that you have 

your (vehicle or engine) serviced as soon as possible. Failure to do 

so could be determined as lack of proper maintenance of your 

(vehicle or engine).” 

(vii) A telephone number for vehicle or engine owners to call to report 

difficulty in obtaining remedial action. 

(viii) A card to be used by a vehicle or engine owner in the event the 

vehicle or engine to be recalled has been sold. Such card should 

be addressed to the manufacturer, have postage paid, and shall 

provide a space in which the owner may indicate the name and 

address of the person to whom the vehicle or engine was sold or 

transferred. 

(ix) If the remedial action involves recall, the notice must also provide: 

a. A clear description of the components that will be affected by 

the remedial action and a general statement of the measures to 

be taken to correct the nonconformity. 

b. A statement that such nonconformity, if not corrected, may 

cause the vehicle or engine to fail an emission inspection. 

c. A statement describing the adverse effects, if any, of an 

uncorrected nonconforming OBD system on the performance, 

fuel economy, or durability of the engine. 

d. A statement that after remedial action has been taken, the 

manufacturer will have the service facility issue a certificate 

showing that the engine has been corrected under the recall 

program, and that such a certificate will be required to be 

provided to the Department of Motor Vehicles as a condition for 

vehicle registration. 

(D) A notice sent pursuant to this section or any other communication sent 

to vehicle or engine owners or dealers may not contain any statement, 

expressed or implied, that the OBD system is compliant or that the 

OBD system will not degrade air quality. 

(E) The Executive Officer shall inform the manufacturer of any other 

requirements pertaining to the notification under section (e)(3) which 

the Executive Officer has determined as reasonable and necessary to 

assure the effectiveness of the recall campaign. 

(4) Label Indicating that Recall Repairs Have Been Performed. 

(A) If the required remedial action involves recall of engine family(ies), 

OBD group(s), or subgroup(s) thereof, the manufacturer shall require 

those who perform inspections and/or recall repairs to affix a label to 

each vehicle that has been inspected and/or repaired. 
32

(B) The label must be placed in a location approved by the Executive 

Officer and must be fabricated of a material suitable for such location 

in which it is installed and which is not readily removable. 

(C) The label must contain the remedial action campaign number and a 

code designating the facility at which the remedial action or inspection 

to determine the need for remedial action was performed. 

(5) Proof of Performance of Remedial Action Certificate. 

If the required remedial action involves a recall, the manufacturer shall 

provide, through its service agents, to owners of vehicles or engines that 

have had the remedial action performed a certificate that confirms that the 

engine has been recalled and that required inspection and/or repairs have 

been performed. The Executive Officer shall prescribe a format for the 

certificate, which shall be consistent with the format required in Cal. Code 

Regs., title 13, section 2117 and section 2129. 

(6) Record Keeping and Reporting Requirements. 

(A) The manufacturer shall maintain sufficient records to enable the 

Executive Officer to conduct an analysis of the adequacy of the 

remedial action. 

(B) Unless otherwise specified by the Executive Officer, the manufacturer 

shall report on the progress of the remedial action campaign by 

submitting reports for eight consecutive quarters commencing with the 

quarter immediately after the recall campaign begins. The reports 

shall be submitted no later than 25 days after the close of each 

calendar quarter to: Chief, Mobile Source Operations Division, 9528 

Telstar Avenue, Suite 4, El Monte, California 91731. For each recall 

campaign, the quarterly report must contain the following: 

(i) The engine family and the remedial action campaign number 

designated by the manufacturer and a brief description of the 

nature of the campaign. 

(ii) The date owner notifications began and date completed. 

(iii) The number of engines involved in the remedial action campaign. 

(iv) The number of engines known or estimated to be equipped with 

the nonconforming OBD system and an explanation of the means 

by which this number was determined. 

(v) The number of engines inspected during the campaign since its 

inception. 

(vi) The number of engines found to be affected by the nonconformity 

during the campaign since its inception. 

(vii) The number of engines receiving remedial action during the 

campaign since its inception. 

(viii) The number of engines determined to be unavailable for 

inspection or remedial action, during the campaign since its 

inception, due to exportation, theft, scrapping, or other reasons 

(specify). 
33

(ix) The number of engines, during the campaign since its inception, 

determined to be ineligible for remedial action under section 

(e)(2)(B). 

(x) An initial list, using the following data elements and designated 

positions, indicating all vehicles or engines subject to recall that the 

manufacturer has not been invoiced for, or a subsequent list 

indicating all engines subject to the recall that the manufacturer has 

been invoiced for since the previous report. The list must be 

supplied in a standardized computer format to be specified by the 

Executive Officer. The data elements must be written in “ASCII” 

code without a comma separating each element. For example: 

XTY32A71234E-9456123408-25-91A. The add flag (see below) 

should reflect the vehicles or engines for which the manufacturer 

has not been invoiced and the delete flag should reflect changes 

since the previous report. The Executive Officer may change the 

frequency or format of this submittal depending on the needs of 

enforcement. The Executive Officer may not, however, require a 

frequency or format for this submittal that is different in any way 

from the frequency or format determined by the Executive Officer 

as required for reporting of data in Cal. Code Regs., title 13, section 

2119(a)(10) and section 2133(a)(10). 

 Data Elements Positions 

• File Code (designated by DMV) 1 

• License Plate Number 2-8 

• Last three VIN positions 9-11 

• Recall ID Number 12-17 

• Mfg. ID Number 18-22 

 (Mfg. Occupational License Number) 

• Recall Start Date (mmddyyyy) 23-30 

• Add or Delete Flag (A/D) 31 

• Complete VIN if personalized license plate 32-48 

 (File Code “L” or “S”) 

(xi) A copy of any service bulletins issued during the reporting period 

by the manufacturer to franchised dealerships or other service 

agents that relate to the nonconforming OBD system and the 

remedial action and have not previously been reported to the 

Executive Officer. 

(xii) A copy of all communications transmitted to vehicle or engine 

owners that relate to the nonconforming OBD systems and the 

required remedial action and have not been previously reported to 

the Executive Officer. 

(C) If the manufacturer determines that any of the information submitted to 

the Executive Officer pursuant to section (e) has changed or is 
34

incorrect, the manufacturer shall submit the revised information, with 

an explanation. 

(D) The manufacturer shall maintain in a form suitable for inspection, such 

as computer information, storage devices, or card files, and shall make 

available to the Executive Officer or his or her authorized 

representative upon request, the names and addresses of vehicle or 

engine owners: 

(i) To whom notification was sent; 

(ii) Whose engines were repaired or inspected under the recall 

campaign; 

(iii) Whose engines were determined not to be eligible for remedial 

action because the engines were modified, altered, or unavailable 

due to exportation, theft, scrapping, or other reason specified in the 

answer to sections (e)(6)(B)(viii) and (ix). 

(E) The information gathered by the manufacturer to compile the reports 

required by these procedures must be retained for no less than one 

year beyond the useful life of the engines and must be made available 

to authorized personnel of ARB upon request. 

(F) The filing of any report under the provisions of these procedures must 

not affect the manufacturer’s responsibility to file reports or 

applications, obtain approval, or give notice under any other provisions 

of law. 

(7) Extension of Time. 

Upon request of the manufacturer, the Executive Officer may extend any 

deadline set forth in section 1971.5(e) upon finding that the manufacturer 

has demonstrated good cause for the requested extension. 

(f) Penalties for Failing to Comply with the Requirements of Section (e).

(1) In addition to the penalties that may be assessed by the Executive Officer 

pursuant to section (d) because of a manufacturer’s failure to comply with 

the requirements of Cal. Code Regs., title 13, section 1971.1, a 

manufacturer may be subject to penalties pursuant to section 43016, 

Health and Safety Code for failing to comply with the requirements of 

section (e). 

(2) If a manufacturer fails to comply with a voluntary or influenced remedial 

action plan, the Executive Officer may order remedial action pursuant to 

section (d) above. 

NOTE: Authority cited: Sections 39600, 39601, 43000.5, 43013, 43016, 43018, 

43100, 43101, 43104, 43105, 43105.5, 43106, 43154, 43211, and 43212, Health 

and Safety Code. Reference: Sections 39002, 39003, 39010, 39018, 39021.5, 

39024, 39024.5, 39027, 39027.3, 39028, 39029, 39031, 39032, 39032.5, 39033, 

39035, 39037.05, 39037.5, 39038, 39039, 39040, 39042, 39042.5, 39046, 

39047, 39053, 39054, 39058, 39059, 39060, 39515, 39600,-39601, 43000, 

43000.5, 43004, 43006, 43013, 43016, 43018, 43100, 43101, 43102, 43104, 
35

43105, 43105.5, 43106, 43150, 43151, 43152, 43153, 43154, 43155, 43156, 

43204, 43211, and 43212, Health and Safety Code.