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 

Medium-Duty Vehicles and Engines (OBD II) 

Date of Release: July 5, 2012 

Scheduled for Consideration: August 23, 2012 

Mobile Source Control Division 

9528 Telstar Avenue 

El Monte, California 91731 

www.arb.ca.gov 

This report 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 of the Air Resources Board, nor does mention of trade names or 

commercial products constitute endorsement or recommendation for use. 

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TABLE OF CONTENTS 

I. SUMMARY OF STAFF PROPOSAL AND RELATED POLICY ISSUES ........................ 5

II. TECHNICAL STATUS UPDATE AND PROPOSED AMENDMENTS .......................... 12

A. HEAVY-DUTY HYBRID VEHICLES ............................................................................ 12

B. ALTERNATE-FUELED ENGINES ............................................................................... 16

C. DEFINITIONS ............................................................................................................. 18

D. MIL ILLUMINATION AND FAULT CODE STORAGE PROTOCOL ............................ 20

E. STANDARDIZED METHOD TO MEASURE REAL WORLD MONITORING 

PERFORMANCE ............................................................................................................. 21

F. DIESEL MISFIRE MONITORING ................................................................................ 24

G. DIESEL EXHAUST GAS RECIRCULATION (EGR) SYSTEM MONITORING ............ 26

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

MONITORING .................................................................................................................. 27

I. DIESEL OXIDES OF NITROGEN (NOx) CONVERTING CATALYST 

MONITORING .................................................................................................................. 29

J. DIESEL PARTICULATE MATTER (PM) FILTER MONITORING ................................ 32

K. DIESEL NOx SENSOR MONITORING ....................................................................... 35

L. GASOLINE MISFIRE MONITORING .......................................................................... 37

M. GASOLINE SECONDARY AIR SYSTEM MONITORING ........................................... 37

N. ENGINE COOLING SYSTEM MONITORING ............................................................. 38

O. COMPREHENSIVE COMPONENT MONITORING .................................................... 38

P. STANDARDIZATION REQUIREMENTS ..................................................................... 40

Q. CERTIFICATION DEMONSTRATION TESTING REQUIREMENTS .......................... 44

R. DEFICIENCIES ........................................................................................................... 45

S. OTHER PROPOSED AMENDMENTS ........................................................................ 47

T. HD OBD AND OBD II ENFORCMENT REGULATIONS ............................................. 48

III. ENVIRONMENTAL IMPACT ANALYSIS ...................................................................... 51

IV. ENVIRONMENTAL JUSTICE ....................................................................................... 54

V. ECONOMIC IMPACT ................................................................................................... 54

A. LEGAL REQUIREMENTS ........................................................................................... 55

B. COST AND COST EFFECTIVENESS ........................................................................ 55

C. AFFECTED BUSINESSES AND POTENTIAL IMPACTS ........................................... 57

D. POTENTIAL IMPACTS ON VEHICLE OPERATORS ................................................. 58

E. POTENTIAL IMPACTS ON BUSINESS COMPETITIVENESS ................................... 58

F. POTENTIAL IMPACTS ON EMPLOYMENT ............................................................... 59

G. POTENTIAL IMPACT ON BUSINESS CREATION, ELIMINATION, OR 

EXPANSION .................................................................................................................... 59

VI. ANALYSIS OF ALTERNATIVES .................................................................................. 60

VII. SUMMARY AND RATIONALE FOR PROPOSED AMENDMENTS ............................. 60 

DOCUMENTS INCOPORATED BY REFERENCE ............................................................. 82

REFERENCES .................................................................................................................... 83
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APPENDICES 

Appendix A: Proposed Regulation Order: Title 13, California Code of Regulations, 

Section 1971.1, On-Board Diagnostic System Requirements – 2010 and Subsequent 

Model-Year Heavy-Duty Engines 

Appendix B: Proposed Regulation Order: Title 13, California Code of Regulations, 

Section 1968.2, Malfunction and Diagnostic System Requirements – 2004 and 

Subsequent Model-Year Passenger Cars, Light-Duty Trucks, and Medium-Duty 

Vehicles and Engines 

Appendix C: Proposed Regulation Order: Title 13, California Code of Regulations, 

Section 1971.5, Enforcement of Malfunction and Diagnostic System Requirements for 

2010 and Subsequent Model-Year Heavy-Duty Engines 

Appendix D: Proposed Regulation Order: Title 13, California Code of Regulations, 

Section 1968.5, Enforcement of Malfunction and Diagnostic System Requirements for 

2004 and Subsequent Model-Year Passenger Cars, Light-Duty Trucks, and MediumDuty Vehicles and Engines 
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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 increases 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 identifying the faulty component or 

system and the nature of the fault, which 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 use and operation of OBD systems 

ensure reductions of in-use motor vehicle and motor vehicle engine emissions through 

improvements in emission system durability and performance. 

The California Air Resources Board (ARB or Board) originally adopted comprehensive 

OBD regulations in 1989, requiring all 1996 and newer model year passenger cars, 

light-duty trucks, and medium-duty vehicles and engines to be equipped with 

OBD systems (referred to as OBD II). ARB subsequently updated the OBD II 

regulations with the adoption of California Code of Regulations (Cal. Code Regs.), title 

13, sections 1968.2 and 1968.5, which established OBD II requirements and OBD IIspecific enforcement requirements for 2004 and subsequent model year passenger 

cars, light-duty trucks, and medium-duty vehicles and engines. In 2004, ARB adopted 

the Engine Manufacturer Diagnostic system (EMD) regulation (Cal. Code Regs., title 13, 

section 1971), which requires manufacturers of heavy-duty engines and vehicles (i.e., 

vehicles with a gross vehicle weight rating greater than 14,000 pounds) to implement 

diagnostic systems on all 2007 and subsequent model year on-road heavy-duty Ottocycle (gasoline) and diesel engines. However, the EMD regulation is much less 

comprehensive than the OBD II regulation, requiring the monitoring of only a few major 

emission control technologies and containing no standardized requirements. 

Essentially, the EMD regulation was developed to require heavy-duty engine 

manufacturers to achieve a minimum level of diagnostic capability while focusing most 

of their resources on meeting the new 2007 exhaust emission standards. In 2005, ARB 

adopted Cal. Code Regs., title 13, section 1971.1, which established comprehensive 

OBD requirements (HD OBD) for 2010 and subsequent model year heavy-duty engines 

and vehicles, and an HD OBD-specific enforcement regulation, section 1971.5, was 

subsequently adopted in 2009. 

Since amendments were last adopted for the heavy-duty OBD regulations in 2009, ARB 

staff has met with manufacturers to review progress in meeting the regulatory 

requirements and identify the need for revisions. Staff believes that modifications to the 

regulations are warranted and is proposing amendments to the HD OBD regulation 
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section 1971.1, which can be found in Appendix A. Staff is also proposing similar 

amendments to the OBD II regulation section 1968.2 (included in Appendix B) for 

medium-duty diesel engines and vehicles to harmonize the requirements of the two 

regulations. The proposed regulation order for section 1968.2 also contains minor 

amendments that were recently approved by the Board at the January 23, 2012 Board 

hearing but have not been formally adopted to date. These amendments are 

designated by single underline to indicate additions and single strikeout to indicate 

deletions from the existing regulatory text, while the amendments proposed during this 

rulemaking are shown in double underline to indicate additions and double strikeout to 

indicate deletions. Lastly, staff is proposing to amend the associated enforcement 

regulations, sections 1971.5 and 1968.5 (included as Appendices C and D, 

respectively), to align these regulations with the new or modified OBD requirements. 

Within section 1971.1, which initially applied to 2010 model year engines, some 

requirements include specific implementation model year dates that dictate exactly 

when manufacturers are expected to meet a requirement; requirements that do not 

reference an implementation date were required to be initially be implemented for 2010 

and subsequent model year engines. 

Summary of Proposed Amendments 

A summary of the main issues and technical amendments are provided below while 

detailed explanations of each of these issues are provided in section II. Summaries and 

rationales of the proposed changes are provided in section VII of this report. Of the 

proposed amendments to the HD OBD regulation, many have been discussed with 

manufacturers and have raised little issue or have mostly been settled. They include: 

 Clarifying the purpose and objectives of the OBD regulations. 

 Adding a definition for “alternate-fueled engines.” 

 Adding a definition of “emission standard” as it applies to OBD systems. 

 Adding definitions of “exhaust emission standards” and “evaporative emission 

standards.” 

 Adding definitions and revising the permanent fault code storage and erasure 

protocol and in-use monitoring performance requirements applicable to hybrid 

vehicles. 

 Revising the freeze frame storage and erasure protocol. 

 Revising the in-use monitoring performance requirements for the PM filter and 

PM sensor monitors. 

 Revising the diesel misfire monitoring requirements to no longer require emission 

threshold-based malfunction criteria and to require expanded monitoring 

conditions. 

 Delaying some monitoring requirements for catalyzed PM filters and diesel 

NMHC converting catalysts to the 2015 model year and adding test-out criteria. 

 Revising the cooling system monitoring requirements to clarify when monitor 

enablement can occur. 

 Updating the Society of Automotive Engineers (SAE) and International Standards 

Organization (ISO) document references. 
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 Revising the readiness status requirements to clarify which monitors are 

specifically to be included in determining readiness. 

 Clarifying the calibration verification number (CVN) requirements. 

 Revising the certification demonstration testing requirements to clarify how to 

perform the testing for gasoline air-fuel ratio cylinder imbalance monitoring and 

exhaust gas sensor monitoring, to exempt manufacturers from testing the diesel 

misfire monitor, and to clarify the test requirements for catalyst faults and other 

faults where default actions are taken. 

 Adding items required to be submitted as part of the certification application. 

The purpose of the HD OBD and OBD II regulations is to reduce motor vehicle and 

motor vehicle engine emissions by establishing emission standards and other 

requirements for OBD systems that are installed on motor vehicles and motor vehicle 

engines certified for sale in California. The use and operation of OBD systems ensure 

reductions of in-use motor vehicle and motor vehicle engine emissions through 

improvements in emission system durability and performance. The regulations ensure 

that emission reductions forecasted under California’s various motor vehicle and engine 

exhaust and evaporative emission regulations are effectively achieved by monitoring the 

emission-control systems of individual vehicles during every day in-use operation. 

Without functional diagnostic systems, there would be no way to ensure that every 

individual component installed on a motor vehicle is working properly and that every 

malfunction is detected and corrected expeditiously. Such emission reduction 

objectives and benefits are distinct from those derived from ARB’s in-use vehicle 

enforcement test procedures (title 13, Cal. Code Regs., section 2136 et seq.), which are 

directed at ensuring that certified vehicles and engines, on average, do not exceed 

certification exhaust and evaporative emission standards. The proposed amendments 

to sections 1968.2(a) and 1971.1(a) are to reaffirm and make more explicit these 

longstanding and intended purposes of the OBD regulations. 

Regarding the proposed amendments to the diesel monitoring requirements, the HD 

OBD regulation establishes monitoring requirements for approximately 10 major 

emission control components/systems and another 20 or more minor comprehensive 

components on a typical diesel engine. For each major component/system, the 

regulation contains several different monitoring requirements that target specific aspects 

of each component/system that can have an emission impact when not functioning 

properly, which collectively represents about 40 to 50 different monitoring 

requirements. For each minor comprehensive component, the regulation also requires 

separate monitors for individual failures to enable pinpointing of the likely malfunction 

for repair technicians, which collectively represents another 80 or more monitoring 

requirements. In total, staff is proposing significant changes to seven requirements, 

with two of these changes (for diesel misfire monitoring and PM filter feedgas 

monitoring) making the current requirements more stringent and the other five relaxing 

the requirements for the 2013 through 2015 model years. 

Concurrently, the staff is proposing to update the medium-duty vehicle diesel-related 

requirements in the medium-duty OBD II regulation (section 1968.2) to be consistent 
8

with some of the proposed diesel-related amendments to the HD OBD regulation. 

These proposed changes for medium-duty vehicles include diesel monitoring 

requirements and diesel-related in-use monitor performance requirements. This would 

allow manufacturers of both heavy-duty and medium-duty diesel engines to design to 

and meet essentially the same requirements. Staff is also proposing changes that 

would establish specific monitoring requirements and thresholds for future medium-duty 

vehicles certified to a chassis dynamometer tailpipe emission standard in lieu of 

manufacturers requesting ARB approval of their proposed thresholds. 

Further, the staff is proposing amendments to the HD OBD and OBD II enforcement 

regulations (sections 1971.5 and 1968.5, respectively) to align with the proposed dieselrelated changes to the HD OBD and OBD II regulations, specifically the selection 

criteria of engines/vehicles for the test sample group and the mandatory recall 

provisions for diesel engines. 

Stakeholders have recently argued that OBD system requirements are not emission 

standards or test procedures and that ARB does not have authority to order 

manufacturers to recall motor vehicles or engines if ARB were to determine that an 

installed OBD system was found to be in noncompliance with the HD OBD regulation. 

Staff is proposing a new definition of “emission standard” to clarify any confusion and 

misunderstanding as to whether the OBD requirements include emission standards. 

The proposed definition conforms with the federal definition applied to Title II of the 

Clean Air Act by the U.S. Supreme Court in Engine Manufacturers Association v. South 

Coast Air Quality Management District (2004) 541 U.S. 246, 253, 124 S.Ct. 1756, 1762 

(EMA). There the Court clarified that an emission standard, with respect to motor 

vehicles and motor vehicle engines, is a standard that relates to the emission 

characteristics of a vehicle or engine and that, for compliance purposes, requires a 

motor vehicle or motor vehicle engine to emit no more than a certain amount of a given 

pollutant, be equipped with a certain type of pollution-control device, or have some other 

design feature related to the control of emissions. (Id. at 253.) The proposed 

amendments are intended to make clear that the definition of emission standard as 

used in the OBD regulations conforms to the federal definition as interpreted by the 

Supreme Court. 

In addition to the proposed amendments mentioned above, there are a few issues 

where ARB staff and industry differed significantly as to the necessity or the stringency 

of a requirement. In addition to proposed amendments that require more stringent 

requirements that manufacturers objected to, ARB staff also proposed many changes 

that would relax some requirements based on manufacturers’ concerns, though the 

proposal does not go as far as manufacturers have requested. The requirements of 

concern to the affected manufacturers include: 

 
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Heavy-Duty and Medium-Duty Diesel Monitors 

Manufacturers have expressed concerns about meeting some of the required diesel 

monitoring emission malfunction thresholds during the 2013 through 2015 model years, 

particularly for NOx catalyst/NOx sensor monitoring and PM filter monitoring. The HD 

OBD and OBD II regulations currently require manufacturers to detect conversion 

efficiency faults before NOx emissions exceed the applicable NOx standard plus 0.2 

grams per brake-horsepower hour (g/bhp-hr) for the 2013 and subsequent model years. 

For PM filter monitoring, manufacturers are required to detect faults before PM 

emissions exceed a threshold ranging from 0.03 to 0.05 g/bhp-hr for the 2013 through 

2015 model years with a final threshold of 0.03 g/bhp-hr for all 2016 and subsequent 

model year engines and vehicles. Manufacturers have argued that meeting these 

thresholds is difficult or not feasible in the required timeframe. Concerning the NOx 

catalyst and NOx sensor monitor thresholds, manufacturers have indicated that the 

dynamics of the selective catalytic reduction (SCR) system and its control, including the 

NOx sensors and the reductant delivery system, have made it difficult to meet the 

thresholds. Concerning the PM filter monitor thresholds, manufacturers have indicated 

that PM sensors, which many believe will be the only viable way to meet the thresholds, 

will not be available in time for the 2013 model year. Accordingly, they proposed that 

engines continue to use the higher malfunction thresholds required before the 2013 

model year. While staff believes these thresholds are technically feasible to meet, staff 

agrees some relaxation is necessary for the near-term model years, though it disagrees 

with manufacturers about the extent of the relaxation needed. For both the NOx 

catalyst/sensor monitors and the PM filter monitors, staff is proposing higher interim 

thresholds during the 2013 through 2015 model years, with the final stringent thresholds 

delayed until the 2016 model year. Additionally, for the PM filter and PM sensor 

monitors, staff is also proposing free deficiencies related to these monitors for the 2013 

through 2015 model years to acknowledge the risk manufacturers are taking when 

implementing new PM sensors and ensure that they are not penalized for doing so. 

Heavy-Duty SAE J1939 Protocol 

Part of the HD OBD requirements includes standardization of data to be output from the 

engine and vehicle to off-board tools used by technicians and inspectors. The 

regulation currently allows engines to use SAE J1939 as the standard for the 

communication protocol and the diagnostic connector specifications. When the 

requirement was first adopted, SAE J1939 only had a single (250 kilobits per second 

(kbps)) baud rate and a single connector, so there was no need to identify a specific 

baud rate or connector version in the regulation. However, since then, SAE J1939 has 

added an additional baud rate (500 kbps) and a second connector variant to handle the 

new baud rate. Thus, to ensure that all manufacturers were using the same baud rate 

and connector, staff originally proposed to clarify that only the original baud rate and 

connector versions (i.e., the 250 kbps baud rate version) were allowed for standardized 

OBD communication. However, manufacturers have indicated that most of industry was 

already moving towards using the 500 kbps baud rate version to handle an increased 

number of messages and data and requested that they be allowed to use either the 250 
10

kbps or the 500 kbps version indefinitely. While staff agrees that some changes are 

needed to account for the industry trend towards the 500 kbps version, staff does not 

believe both baud rate versions should be allowed as options indefinitely given the 

potential problems of allowing multiple communication variants in the field. Thus, staff 

is proposing to amend the HD OBD regulation to use either variant and their associated 

connector up through the 2015 model year and would allow only the 500 kbps variant 

for all 2016 and subsequent model year heavy-duty engines. 

Heavy-Duty Hybrid Vehicles 

The HD OBD regulation has required monitoring of hybrid components since the 

regulation was first adopted in 2005. While updating the regulation in 2009, staff added 

language that provided general guidelines for monitoring of the hybrid system and 

required manufacturers to submit a monitoring plan for ARB’s review and approval. 

Affected manufacturers, however, have complained about the burden of having to 

comply with the HD OBD requirements and have argued that because the heavy-duty 

industry is horizontally-integrated and heavy-duty engine manufacturers only 

manufacture the engine while hybrid system manufacturers are only responsible for the 

hybrid components, it is very difficult to design compliant diagnostics that would account 

for the wide range of engine-hybrid applications. Citing that hybrid vehicles only 

constituted a very small part of the heavy-duty market and are only economically viable 

because of sizable government funding subsidies and incentives to purchasers, hybrid 

system manufacturers have requested exemption from having to implement OBD 

systems on heavy-duty hybrid vehicles until a later model year (e.g., 2018 model year). 

Concurrently, engine manufacturers have requested that they be relieved from any 

liability for engine diagnostics that are adversely affected by the hybrid system. While 

ARB staff believes revisions are needed given these circumstances, it disagrees with 

the amount of lead time requested, given that these monitoring requirements have been 

in the regulation for many years. Staff believes that further delays in hybrids becoming 

compliant should be avoided and will better ensure that near term hybrid vehicles (that 

are largely subsidized by ARB through ARB’s hybrid and zero-emission truck and bus 

voucher incentive project) achieve and maintain emission benefits over the life of the 

vehicle. Thus, staff is proposing one extra year (the 2013 model year) in which 

manufacturers are allowed the option of complying with alternative, much less stringent 

requirements. In addition, staff is proposing changes to the deficiency provisions which 

allow for certification of HD OBD systems with minor implementation problems that don’t 

fully meet the HD OBD requirements. Specifically, staff is proposing two additional free 

deficiencies in the 2013 through 2015 model years (for a maximum of four free 

deficiencies) for hybrid-related issues to help manufacturers certify their HD OBD 

systems.

Heavy-Duty Alternate-Fueled Engines 

The regulation currently requires manufacturers to implement “full” HD OBD systems on 

alternate-fueled engines starting in the 2020 model year. When first adopting this 

requirement, ARB staff had anticipated alternate-fueled engines to constitute a very low 
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percentage of the heavy-duty market. This assumption, however, is no longer expected 

to hold true, with several manufacturers indicating plans to offer more alternate-fueled 

engines in the near future. Considering the importance of ensuring the durability and 

emission benefits of these engines, staff initially proposed to move up the start date 

from the 2020 to the 2016 model year. Alternate-fueled engine manufacturers, 

however, have argued about the difficulty in meeting this proposal, and some proposed 

a phase-in plan to come into compliance starting in the 2016 model year, with 100 

percent of 2018 model year engines meeting the HD OBD requirements. Based on 

further discussions with manufacturers, staff ultimately revised its proposal to require 

HD OBD system implementation on alternate-fueled engines starting in the 2018 model 

year. This would result in alternate-fueled engines complying two years earlier than 

currently required and minimize the chance for inequities in the phase-in years between 

manufacturers that offer many different alternate-fueled engines and those that have 

only one or two offerings. Staff, however, is anticipating some alternate-fueled engine 

manufacturers to oppose this revised proposal. 

Emission and Cost Impacts 

The proposed amendments are not expected to have an adverse impact on the 

environment. Overall, the proposed amendments to the HD OBD and OBD II 

regulations would result in cleaner vehicles than those currently produced, since the 

requirements for later model years will still be more stringent than those for current 

model year, and are not expected to significantly alter previously calculated emission 

benefits or findings. During the 2009 HD OBD regulatory process, the lifetime 

cumulative emission reductions for HD OBD, on a per engine basis calculated with the 

most recent version of the base emission inventory model (EMFAC), were calculated to 

be 165 pounds of reactive organic gases (ROG), 2000 pounds of NOx, and 14 pounds 

of PM. For OBD II, 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. These benefits calculations have not changed since. 

The additional costs to manufacturers to meet the proposed amendments are expected 

to be negligible. Staff calculated the cost effectiveness of this proposed rulemaking to 

be $13.13 per pound of PM and $0.08 per pound of ROG + NOx. Further details of the 

emission benefit, costs, and cost-effectiveness are included in sections III. and V. 

Recommendation 

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

OBD II regulations and associated enforcement regulations as proposed in the Initial 

Statement of Reasons. 
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II. TECHNICAL STATUS UPDATE AND PROPOSED AMENDMENTS 

A. HEAVY-DUTY HYBRID VEHICLES 

One issue of concern to heavy-duty engine, vehicle, and hybrid system manufacturers 

is OBD monitoring of heavy-duty hybrid components. The HD OBD regulation currently 

requires hybrid systems and components to be monitored for emission-related 

malfunctions and to ensure the addition of such systems to a certified engine does not 

adversely affect the ability of the engine to comply with OBD requirements. Because 

hybrid systems vary greatly in terms of system architecture and capability, 

manufacturers are required to submit a monitoring plan for ARB’s review and approval 

for hybrid vehicles. Affected manufacturers have argued that, unlike the light-duty and 

medium-duty industry, the heavy-duty industry is a horizontally-integrated industry in 

which the heavy-duty engine manufacturers only manufacture the engine and the hybrid 

system manufacturers are responsible for the hybrid components and neither have total 

integrated system responsibility or capability. Further, they argue the use of hybrid 

technology on heavy-duty vehicles is still emerging, that they constitute a very small 

market share, and that they are only economically viable because of sizable 

government funding subsidies and incentives to purchasers and would be even less 

viable given additional expenses to incorporate OBD systems. 

The hybrid system manufacturers have indicated that, despite the requirements being 

adopted in the HD OBD regulation well in advance of the 2013 model year, they have 

not yet developed compliant diagnostics for their own components let alone attempted 

to understand their impact on the engine diagnostics. This leads to the engine 

manufacturers representing that they cannot be responsible for designing their engine 

diagnostics to account for all of the various hybrid applications that might get mated to 

one of their engines in the future. Additionally, hybrid system manufacturers argue that 

because they have no knowledge of how the engine diagnostics work on the various 

engines they work with, they cannot be responsible for ensuring compliant systems. 

Accordingly, the hybrid system manufacturers have asked to be exempted from OBD 

requirements at least until the 2017 model year, which parallels the exemption recently 

granted by the U.S. EPA under the federal OBD regulation. Additionally, the engine 

manufacturers have requested relief for any of their engines that get mated to a hybrid, 

specifically proposing that they not be held liable for ensuring the engine diagnostics 

comply with the hybrid system components, and, where necessary, be allowed to 

desensitize or disable diagnostics that no longer work correctly when used in hybrid 

applications. 

Fundamentally, an integrated approach needs to be used for engine and hybrid system 

manufacturers to have a reasonable chance at meeting all of ARB’s requirements, 

including the OBD requirements and tailpipe standards. Modern engine and emission 

control systems are extremely complex and must balance many competing factors such 

as durability, performance, emissions, and fuel economy. Engine manufacturers 

expend significant resources to find a solution that simultaneously meets all of these 

requirements, so it should come as no surprise that major alterations to the system such 
13

as attaching a hybrid system that can turn the engine on and off and change the speeds 

and loads the engine is routinely operated at can substantially compromise the ability of 

the engine to continue to meet all of the requirements. Further, an integrated approach 

has the advantage of likely being able to maximize hybrid operation and efficiency, 

thereby making the system more economically viable for the long term. As such, staff is 

proposing an extra year of relaxation (the 2013 model year) before hybrid systems are 

required to be properly integrated and compliant with the OBD regulation. 

In general terms, there are three areas where hybrid systems need to comply with the 

OBD requirements. First, there are diagnostics of the added hybrid 

components/systems themselves. Such diagnostics are required to identify 

malfunctions that lead to emission increases or affect other diagnostics. These hybrid 

component/system diagnostics primarily fall under a section of the regulation that details 

monitoring requirements for comprehensive components, which ensures all electronic 

input and output components/systems that can affect emissions are fully monitored. 

Hybrid components that would typically be monitored under such requirements include 

electric motors, inverters, sensors used for the battery pack, and the battery pack itself. 

While hybrid manufacturers readily acknowledge that they already have a fair amount of 

diagnostics for their components to facilitate service, these diagnostics do not fully 

cover all of the components and failure modes required by the HD OBD regulation. 

Therefore, most hybrid systems will need added diagnostics (i.e., software routines and 

calibrations in the on-board computers) to cover the additional failure modes and 

components. It is expected that the hybrid system manufacturer and suppliers that 

already provide some diagnostics for service will also need to implement additional 

diagnostics to require such additional failure notification since they know how these 

components work. Achieving this is primarily a matter of dedicating sufficient 

engineering resources to develop, implement, and calibrate the additional diagnostics. 

Second, there are the engine diagnostics themselves. While these diagnostics have 

largely been developed and calibrated to meet the stand-alone engine requirements, 

the addition of a hybrid system can adversely impact some of these diagnostics. As a 

very simple example, an engine manufacturer may have designed a required diagnostic 

of an emission control component to run only at idle. However, when mated to a hybrid 

system that turns the engine off at every idle, that monitor would no longer be able to 

run and, consequently, would no longer be able to detect failures of that emission 

control component. A more complicated example involves engine diagnostics that are 

calibrated to a tailpipe emission threshold such as EGR diagnostics that must detect 

malfunctions before tailpipe emissions exceed two times the tailpipe standards. Engine 

manufacturers do iterative testing on an engine dynamometer to determine the level of 

malfunction that equates to that tailpipe emission level and design a diagnostic that 

uses EGR parameters to detect such a level. However, when mated with a hybrid, the 

engine could be utilized in different speeds and loads where it is more dependent on 

proper EGR operation and thus, have higher corresponding tailpipe emissions when a 

fault is detected. Engine manufacturers clearly cannot predict every possible hybrid 

system control strategy or feature and thus cannot by themselves design an OBD 

system that will remain compliant regardless of how it is modified. Similarly, hybrid 
14

system manufacturers cannot by themselves be expected to know how every engine 

diagnostic works and make sure they design their system accordingly. 

This leads to the only viable solution: having an integrated system whereby one entity 

takes responsibility to ensure the system as a whole works properly. Such an approach 

is not unlike what engine manufacturers already do when coordinating with their 

suppliers that source the emission control components on their engines to ensure that 

the end result actually works. Hybrid system manufacturers currently do the same with 

their systems that are comprised of components from various suppliers. Coordination 

between the hybrid system manufacturer and the engine manufacturer (and even other 

entities like the transmission or vehicle manufacturers) already happens to varying 

degrees to ensure some reasonable level of drivability and performance and to work out 

details such as warranty responsibility. Staff’s proposal would require further 

coordination between the hybrid system manufacturer and engine manufacturer and 

would ensure that some party takes ultimate responsibility to ensure that the OBD 

system, in total, works. In some cases, there are engine manufacturers that are more 

vertically integrated (e.g., that manufacture both the engine and the vehicle and perhaps 

even the hybrid system), with a few of those manufacturers already well on their way to 

an integrated design. In other cases, staff expects hybrid system, engine, and even 

vehicle manufacturers to partner together to achieve an integrated solution. For some, 

staff expects the existing relationships to change very little other than more involvement 

between the entities and one of them taking overall responsibility for OBD system 

compliance. In any case, ultimately one party will be the ‘manufacturer’ applying for and 

receiving OBD certification for the integrated hybrid system and engine and that party – 

be it the manufacturer of the hybrid system, the engine manufacturer, or, in some 

cases, the vehicle integrator – will be the party the ARB recognizes as the manufacturer 

of the system and liable for noncompliance. 

Third, a more minor but still important element of OBD is structure and standardization 

of the diagnostics. The OBD requirements lay out detailed rules for everything from 

types of statistical protocols that can be used for diagnostics to when and how fault 

information must be stored and communicated to the driver and repair technicians. 

While the engine diagnostics should already meet these requirements, the hybrid 

system diagnostics likely do not, so changes will need to be made to the software in the 

on-board computers to be able to conform to the OBD requirements. For some of the 

requirements, industry standards such as SAE recommended practices are referenced 

and used, but some hybrid system manufacturers have expressed concern that 

sufficient standardization has not yet been defined for all of the various hybrid 

components and systems. Staff, however, believes the hybrid manufacturers have 

overemphasized the need for some elements to be standardized. The SAE committees 

are accustomed to engine manufacturers and others adding new components and 

needing additional standardized designations and are usually able to accommodate 

such requests in a timely manner, and should be able to do that here as well. Where 

standardization is not likely to occur fast enough is in the area of messages for control 

of such systems (e.g., between the engine and hybrid system computers); however, 

such standardization is not required to comply with HD OBD or any other ARB 
15

requirements. Any integrated approach would, by definition, resolve such issues 

regardless of whether the solution used standardized or proprietary control messages. 

To address concerns raised by hybrid system and engine manufacturers, staff is 

proposing to modify the 2013 model year requirements to allow use of hybrid systems. 

Under the proposed modifications, a hybrid vehicle would be required to use a 

California-certified 2013 model year engine as the base engine and that any 

modifications made to the base engine’s certified OBD system be solely for the purpose 

of preventing false malfunction determinations that could otherwise occur as a result of 

the integration of the hybrid system hardware and software. If a hybrid vehicle is 

certified, the engine manufacturer would be exempt from enforcement or liability for any 

noncompliance caused by the addition of the hybrid system. Finally, hybrid system and 

engine manufacturers would be exempted from having to monitor any of the hybrid 

system components. Staff believes it is necessary to modify the 2013 model year 

requirements given the current capabilities of both hybrid and engine manufacturers. 

Further, without providing clear and direct relief to engine manufacturers for engines 

that are used in hybrid vehicles, engine manufacturers may be hesitant to allow their 

engines to be used in such applications at the risk of their engines becoming 

noncompliant. It should be noted, however, that this relaxation applies only to the HD 

OBD regulation and not any other applicable emission standard or regulation such as 

tailpipe standards. 

Staff’s proposal to amend the requirements for the 2013 model year does not 

necessarily mean that all the systems will go from zero to full compliance by 2014. The 

HD OBD regulation already provides for deficiencies – areas of the requirements where 

manufacturers make a good faith attempt to comply in full but fall short – and 

manufacturers can use the provisions to still get certified even though they do not meet 

every requirement. Approval of deficiencies is based on several factors identified in the 

regulation including the overall compliance of the system, good faith effort on the part of 

the manufacturer to comply, and the manufacturer’s plan to come into compliance as 

soon as possible. Staff expects that it is likely that some, if not many, hybrid systems in 

2014 may fall short of some of the requirements, despite the best efforts of 

manufacturers to comply, yet the systems will still be eligible to be certified by using the 

deficiency provisions. Staff also expects that some hybrid system manufacturers may 

make a business decision to not expend the resources for compliance in 2014, in which 

case they will not be able to offer hybrids for sale in California beyond 2013. For those 

that do remain in the California market and are thus eligible for incentive funds, the 

integrated design approach required by the HD OBD regulation will likely lead to more 

capable hybrid systems having increased efficiencies that meet all ARB requirements. 

Hybrid manufacturers have indicated that the proposed changes provided above are not 

enough, indicating that their lack of experience with designing OBD systems makes it 

difficult to meet the required HD OBD implementation dates. They further indicated that 

hybrid vehicles comprise less than 1 percent of the heavy-duty market, and that the 

requirements would impose a huge burden on the hybrid manufacturers. Thus, they 

proposed delaying HD OBD compliance for heavy-duty hybrid vehicles beyond the 2013 
16

model year. Staff, however, disagrees that more lead time is the appropriate solution. 

The requirements for hybrids to comply have been clearly identified in the regulation 

since 2009 and little progress has been made since then, so providing even more lead 

time is not likely to change the situation. In contrast, requiring manufacturers to begin 

compliance in the short-term to remain eligible for funding through ARB’s hybrid and 

zero-emission truck and bus voucher incentive project (HVIP) will likely provide 

sufficient motivation to manufacturers to make real progress. Avoiding further delays in 

compliance will also better ensure that near-term hybrid vehicles (that are largely 

subsidized by ARB through the HVIP) actually achieve and maintain benefits over the 

life of the vehicles. 

Hybrid manufacturers also suggested that there would be a learning curve for them and 

that while the deficiencies available in the HD OBD regulation provide an avenue for 

them to get certified with less-than-fully compliant systems, there are fines for engines 

certified with more than two deficiencies. Knowing that most hybrid engines certified in 

2014 may fall short of some HD OBD requirements, just like many engines certified in 

2010 fell short of the initial HD OBD requirements, hybrid manufacturers have 

requested that additional or unlimited free deficiencies be allowed for the first several 

years of implementation. While engine manufacturers were allowed unlimited free 

deficiencies in the 2010 through 2012 timeframe, engine manufacturers then were faced 

with a much more difficult task than hybrid system manufacturers will be facing. 

Accordingly, staff does not agree that similar deficiency allowances be given. However, 

staff does acknowledge that most hybrid systems will likely have some deficiencies in 

the early years and thus is proposing an additional two free deficiencies for hybrid 

systems in the 2013 through 2015 model years to help reduce the fines for 

manufacturers that fall short. As is done with engines and is described above for 

hybrids, the party applying for and receiving OBD certification will be the ‘manufacturer’ 

and deficiencies (including the additional two free deficiencies or any associated fines 

for deficiencies beyond that) will be assessed on this manufacturer. 

B. ALTERNATE-FUELED ENGINES 

The heavy-duty OBD regulation currently allows alternate-fueled engines to delay 

implementation of “full” OBD systems until the 2020 model year, with 2013 through 

2019 model year alternate-fueled engines required to comply with the less 

comprehensive EMD requirements and basic monitoring of all NOx aftertreatment 

components. This late start date of 2020 was adopted in 2006 as part of the initial HD 

OBD regulation with the expectation that alternate-fueled heavy-duty engines would 

make up a small portion of the market share and, based on light-duty experience with 

alternate fuel conversions of gasoline vehicles, that the engines would primarily be 

OBD-compliant gasoline or diesel engines that are converted to an alternate-fueled 

engine and continue to have functional full OBD systems. Recent information, however, 

has indicated that some of these assumptions by staff were incorrect. Several 

manufacturers have indicated that alternate-fueled engine sales are not insignificant, 

with at least one engine manufacturer announcing plans to offer significantly more 

alternate-fueled engines in the near future. Recent discussions with other regulating 
17

agencies indicate they are considering near or mid-term measures to greatly increase 

the market share of alternate-fueled engines. Additionally, in discussions with 

manufacturers currently offering alternate-fueled engines, staff has found more diverse 

solutions than previously expected. These include alternate fuel conversions that 

remain compression-ignited and retain the diesel emission control solution, conversions 

that change from compression-ignition to spark-ignition and change over to more 

gasoline-like emission control solutions, conversions to non-stoichiometric spark-ignition 

that retain diesel-like emission control solutions, etc. Such conversions can have a 

much larger impact on the OBD system than simpler conversions staff were familiar 

with, resulting in several unmonitored major emission control components in addition to 

the normal impacts of altering correlation to emission thresholds and monitoring 

frequency. Therefore, staff is proposing to move up the required start date for full OBD 

monitoring from the 2020 model year to the 2018 model year. 

Staff had originally proposed that the compliance date be moved up to the 2016 model 

year, but feedback from several manufacturers at the workshop indicated bringing their 

many alternate-fueled engine families into compliance in the 2016 model year would be 

difficult. As such, they requested a phase-in plan for the 2016 through 2018 model 

years in lieu of compliance for all engine families in 2016. In subsequent discussions 

with manufacturers that had multiple engine families, staff determined that, within the 

small market share of alternate-fueled engines, there could be a significant inequity 

during the phase-in years between manufacturers that offer many different product 

offerings and those that have only one or two offerings. To address the initial request 

for additional lead time and to avoid inequity during the phase-in years, staff revised the 

HD OBD regulation proposal to require that the HD OBD requirements apply to all 

alternate-fueled engines starting with the 2018 model year. 

While the HD OBD regulation currently does not have a specific definition for alternatefueled engines, the definition of “gasoline engines” includes alternate-fueled engines 

based on staff’s presumption from light-duty experience that all alternate-fueled engines 

would be spark-ignited and have emission controls most like gasoline engines. This 

presumption, however, was wrong. To date, there has also been some confusion about 

what exactly constitutes an alternate-fueled engine versus a gasoline or diesel engine. 

Specifically, issues have come up with engines that can use more than one type of fuel, 

such as engines that can operate on two different types of fuels at the same time and 

engines that can operate on two different types of fuel but only one at a time. In some 

instances, these engines are appropriately classified as alternate-fueled engines when 

both fuels are used for the engine to operate. In other cases, such engines can also 

operate exclusively on diesel or gasoline if the alternate fuel is not used or not available, 

and such engines should not be considered alternate-fueled during those conditions. 

Accordingly, staff is proposing a definition that would more explicitly identify what 

configurations are considered alternate-fueled (and thus exempt from OBD monitoring 

until the 2018 model year). This clarification would provide manufacturers with direction 

as to how possible future configurations would be classified and prevent gaming by 

manufacturers looking to inappropriately classify something as an alternate-fueled 

engine to avoid OBD requirements. 
18

Additionally, regarding heavy-duty alternate-fueled engines, staff is proposing another 

clarification with respect to evaporative system monitoring. As currently written, engines 

are exempt from evaporative system monitoring if they are not required to be equipped 

with evaporative emission systems. Technically, ARB regulations do not mandate 

vehicles be equipped with components specifically to control evaporative emissions, so 

the existing language is unclear about which vehicles and engines are subject to the 

evaporative system monitoring requirements. ARB regulations do however clearly 

delineate which vehicles and engines are subject to evaporative emission standards. 

Accordingly, the proposed change would exempt engines from evaporative monitoring if 

they are not subject to the evaporative emission standards. As examples, compressed 

natural gas (CNG) engines are not subject to evaporative emission standards but liquid 

propane gas (LPG) engines are subject to the standards. The change would make it 

clear that evaporative system monitoring is required for LPG engines, irrespective of 

whether the manufacturer claims it has or has not equipped the engine with an 

evaporative emission system. Alternate-fueled engines that are subject to evaporative 

emission standards and thus required to do evaporative system monitoring would be 

required to submit a plan for Executive Officer approval on what monitoring they would 

do and its equivalence to the type of evaporative system monitoring required for 

gasoline applications. 

C. DEFINITIONS 

Staff is proposing that a definition of “emission standard” be added to the OBD 

regulations to help clarify any confusion among stakeholders that the OBD requirements 

are not emission standards. The proposed definition specifically defines emission 

standard in the context of OBD regulations and conforms that definition with the EMA 

decision, which defined a “standard relating to the control of emissions” under Title 2 of 

the Clean Air Act as it applies to motor vehicles and motor vehicle engines. There, the 

Court found that an emission standard relates to the emission characteristics of a 

vehicle or engine and that for compliance purposes, requires a motor vehicle or motor 

vehicle engine to emit no more than a certain amount of a given pollutant, be equipped 

with a certain type of pollution-control device, or have some other design feature related 

to the control of emissions. (Id.) Staff is proposing that the OBD regulations add a 

definition of emission standard to be consistent with the definition set forth in EMA for 

purposes of clarity, consistency, and conformity. Under the federal definition, 

requirements establishing OBD design features related to the control of emissions, as 

well as exhaust and evaporative numerical emission limits, relate to the emission 

characteristics of the engine and are emission standards. The proposed amendments 

are intended to make clear that the definition of emission standard as used in the OBD 

regulations conforms to the federal definition. The proposed definition, which modifies 

the definition of “emission standard” as set forth in Health and Safety Code section 

39028, is authorized by Health and Safety Code sections 39010 and 39601 in that the 

proposed definition conforms with existing federal definitions. 

For purposes of consistency and clarity, ARB staff is also adding the terms “exhaust 
19

emission standard” and “evaporative emission standard” in the definitions section to 

clarify, where needed, previous references to emission standards. These proposed 

terms are two subcategories of emission standards and are used to specifically identify 

the specified subcategories as opposed to the broader term of emission standard that 

encompasses all standards, including among other requirements OBD design features 

relating to the control of emissions and tailpipe and evaporative numerical limits. 

HD OBD systems are required to support standardized reporting of the calibration 

identification number (CAL ID), which identifies the current software version installed in 

the engine, and the calibration verification number (CVN), which verifies the integrity of 

the software. These two parameters are intended to be used during heavy-duty vehicle 

inspections to help verify that valid software is installed in the on-board computer and 

that the software has not been corrupted or tampered with, which may occur for 

performance or fuel economy reasons or to defeat the OBD system. These parameters 

can also be used to verify that the proper software has been installed as the result of an 

in-use action (e.g., service campaign, recall). The HD OBD regulation currently requires 

a CAL ID/CVN combination for each “diagnostic or emission critical” electronic control 

unit. The current definition of “diagnostic or emission critical” includes the engine 

control unit and is intended to cover other control units that play a significant role in the 

emission control system or diagnostic systems. However, there is an ongoing trend 

with engine and vehicle designs to distribute diagnostic and control functions across 

multiple control units thereby subjecting more control units on an engine or vehicle to 

reporting these parameters. Under the current definition, there is a potential 

proliferation of CAL ID and CVN data and maintenance of those data without a 

commensurate OBD program benefit. Staff is therefore proposing to modify the 

definition of “diagnostic or emission critical” to limit the number of control units that are 

subject to the requirement while preserving the requirement for control units that serve a 

significant role in emissions or diagnostics or would likely be targeted for tampering. 

The HD OBD regulation currently includes a definition of “small volume manufacturer” in 

section 1971.1(d)(7.4), which states “a manufacturer with projected engine sales for 

California heavy-duty vehicles of less than 1200 engines per year for the 2010 model 

year.” This definition was adequate for the original use that was limited to initial 

implementation of the HD OBD system itself. With the proposed additions of required 

phase-in schedules for the diesel misfire, NOx catalyst/NOx sensor, and PM filter 

monitoring requirements (described below in their respective sections), staff is 

proposing to relax requirements for small volume manufacturers with limited resources 

to meet the phase-ins (described in section II.S. below). Accordingly, staff is proposing 

to add a definition for “small volume manufacturer” that would reference the definition in 

Cal. Code Regs., title 13, section 1900(b), with the exception that California sales of 

less than 1200 heavy-duty engines will be used in lieu of 4500 engines. 

The HD OBD regulation currently allows manufacturers to erase a confirmed fault code 

or 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. The regulation currently defines “warm-up cycle” as “sufficient 
20

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).” 

Some concerns have been raised that certain vehicles, such as vehicles with highly 

efficient engines, may not be able to meet these temperature criteria under normal 

driving and ambient conditions. Staff understands that some allowances should be 

made for these vehicles that are unable to warm-up the engine coolant temperature to 

the defined temperatures even if they have been sufficiently driven. Thus, staff is 

proposing to allow manufacturers the option to define a “warm-up cycle” as a driving 

cycle in which the criteria to erase a permanent fault code for continuous monitors are 

met. This would ensure that the vehicle has been operated for a sufficient period of 

time to reasonably detect a recurrence of the malfunction and would allow timely 

erasure of confirmed or previously-MIL on fault codes. 

Staff is proposing changes to the permanent fault code erasure requirements and the 

in-use monitor performance requirements that would apply to heavy-duty hybrid 

vehicles, the details of which are described below. Given the context of the proposed 

changes, new definitions are needed to complement the proposed requirements. Thus, 

staff is also proposing three new definitions for “hybrid vehicle,” “fueled engine 

operation,” and “propulsion system active” and making changes to the “ignition cycle” 

definition to supplement the proposed changes. More details about the proposed 

definitions can be found below. 

D. MIL ILLUMINATION AND FAULT CODE STORAGE PROTOCOL 

The HD OBD regulation currently requires vehicles using the ISO 15765-4 protocol to 

store and erase freeze frame conditions in conjunction with the storage and erasure of 

either the pending fault code or the confirmed fault code. This has unintentionally 

resulted in manufacturers erasing freeze frame conditions for pending fault codes that 

mature to confirmed fault codes and has left repair technicians without helpful 

information to diagnose detected faults. To prevent such erasures, staff is proposing 

that starting with the 2016 model year, manufacturers be required to store freeze frame 

conditions in conjunction with storage of a pending fault code. If the pending fault code 

is erased in the next driving cycle because no fault is detected, the manufacturers would 

also be required to erase the freeze frame conditions. If, however, the pending fault 

code matures to a confirmed fault code, the manufacturer would be required to either 

retain the current freeze frame conditions or update the freeze frame conditions with 

those related to storage of the confirmed fault code. For monitors that do not store 

pending fault codes (e.g., one-trip monitors or monitors that use alternate statistical MIL 

illumination strategies), staff is proposing that manufacturers store and erase freeze 

frame conditions in conjunction with storage and erasure of a confirmed fault code. 

Such changes will better ensure under all conditions that freeze frame information is 

available to aid a technician in diagnosing a detected fault. 

Staff is also proposing minor amendments to the erasure protocol for confirmed or 

previously MIL-on fault codes in the HD OBD regulation. The regulation currently states 

that the OBD system “may” erase the fault code if the fault isn’t again detected “in at 
21

least” 40 warm-up cycles” and the MIL is not presently illuminated for that fault. To 

ensure consistency among manufacturers, staff is proposing to modify the language to 

state that the OBD system “shall” erase the fault code if the fault isn’t again detected “in” 

40 warm-up cycles and the MIL is not presently illuminated for that fault – this 

amendment would apply starting with the 2016 model year. This change will better 

ensure that repair technicians focus on recently detected faults and are not led astray 

chasing down faults that have long since disappeared.

Additionally, staff is proposing changes to address issues concerning permanent fault 

code erasure on heavy-duty hybrid vehicles for monitors that are designed to run 

continuously, including monitors that must wait until similar conditions are satisfied (e.g., 

gasoline misfire and fuel system monitors). Currently, the regulation requires that the 

permanent fault code for these monitors be erased only after the vehicle has been 

operated such that, among other conditions, criteria similar to those for a general 

denominator (section 1971.1(d)(4.3.2)(B)) have been satisfied on a single driving cycle 

(with the exception that the general denominator conditions require ambient 

temperature above 20 degrees Fahrenheit or below 8000 feet in elevation). This 

ensures 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 the 

permanent fault code. Among these conditions is the criterion that the “cumulative time 

since engine start” be greater than or equal to 600 seconds. This language may not be 

clear for vehicles such as hybrid vehicles, where the engine may not start running at the 

beginning of a drive cycle like it would on a conventional vehicle. Thus, for hybrid 

vehicles, staff is proposing to clarify that manufacturers use 600 cumulative seconds of 

“propulsion system active” time in lieu of the 600 cumulative seconds after engine start, 

with “propulsion system active” defined as when the vehicle is operated, regardless of 

whether it is powered by the battery or the engine or both. Staff believes this new 

definition would ensure equivalent vehicle operation time between conventional vehicles 

and hybrid vehicles. 

E. STANDARDIZED METHOD TO MEASURE REAL WORLD MONITORING 

PERFORMANCE 

The OBD regulations require 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 operating 

relative to vehicle operation. The regulation also requires all vehicles to keep track of a 

“general denominator”, which is a measure of how often the vehicle is operated and is 

intended to represent a “typical” driving cycle the vehicle usually encounters. The 

regulations require the manufacturer to increment this denominator only if certain 

criteria are satisfied on a single driving cycle. This method allows very short trips or 

trips during extreme conditions such as very cold temperatures or very high altitude to 

be filtered out and excluded from the count. This is appropriate because these are also 

conditions where most OBD monitors are neither expected nor required to operate. In 
22

addition to the general denominator, manufacturers are required to track specific 

denominators for several major monitors. These denominators are tailored to the 

specific components being monitored and provide a more accurate and appropriate 

indication of the monitoring opportunities for each of those components relative to how 

often those components are used. 

The HD OBD regulation currently requires all vehicles to increment the general 

denominator if, among other conditions, the cumulative time since engine start is 

greater than or equal to 600 seconds. For the same reasons noted above, hybrid 

vehicles need an alternate definition to recognize trips where the engine does not start 

right away. Thus, similar to the changes proposed above for the permanent fault code 

erasure protocol, for hybrid vehicles, staff is proposing to clarify that manufacturers 

must use 600 cumulative seconds of “propulsion system active” time in lieu of the 600 

cumulative seconds after engine start when incrementing the general denominator. 

Additionally, staff is also proposing to require 10 seconds of “fueled engine operation” to 

be met in order to increment the general denominator to discern between trips with and 

without engine operation. This condition would ensure that only trips where the engine 

has at least turned on once during the driving cycle are counted when looking at how 

often engine-related emission control component monitors are running. These 

proposed changes would apply to all 2016 and subsequent model year heavy-duty 

hybrid vehicles. 

Staff is also proposing amendments to the in-use monitor performance requirements for 

PM filter monitors. The HD OBD regulation and OBD II regulation currently require the 

PM filter active/intrusive injection monitor (sections 1971.1(e)(8.2.6) and 

1968.2(f)(9.2.6)) to increment the denominator for that monitor when, in addition to the 

general denominator criteria, a regeneration event is commanded for a time greater 

than or equal to 10 seconds. Intrusive injection, while used during a regeneration event, 

is not necessarily tied to when regeneration begins. Staff believes the denominator 

incrementing criteria for such a monitor should instead be similar to monitors of other 

components/systems that are commanded to activate in-use where monitoring 

frequency is tracked relative to how often that particular component or system is used. 

Thus, staff is proposing to require manufacturers to increment the denominator for this 

monitor when, in addition to the general denominator criteria, the intrusive injection is 

commanded to function for a cumulative time greater than or equal to 10 seconds in 

both the HD OBD and OBD II regulations. 

Additionally, staff is proposing amendments to the denominator incrementing criteria for 

the PM filter filtering performance and missing substrate monitors in both the HD OBD 

and OBD II regulations. The HD OBD regulation currently requires these PM filter 

monitors to increment the denominator when, in addition to the general denominator 

criteria, the cumulative engine run time exceeds 800 minutes, while the OBD II 

regulation currently requires the denominator to increment when, in addition to the 

general denominator criteria, the cumulative miles of vehicle operation exceeds 500 

miles. Further, the HD OBD regulation requires these monitors to meet a minimum 

acceptable in-use performance ratio of 0.100, while the OBD II regulation requires these 
23

monitors to meet a ratio of 0.336 starting in the 2013 model year. ARB adopted the 

current denominator incrementing criteria based on the capability of PM filter monitoring 

technology. Most current monitoring strategies are limited to running during a narrow 

window relative to a PM filter regeneration event. Accordingly, the denominator criteria 

were tied roughly to a period of vehicle operation that would allow a regeneration event. 

However, there has been concern with this approach because PM filters are needed to 

control emissions throughout each and every driving cycle, not just for a narrow window 

of once per regeneration event. Additionally, regeneration event intervals have been 

significantly increasing leading to longer and longer intervals between monitoring events 

and significant consequent delays from the time of occurrence of a fault to detection of 

the fault. Fortunately, monitoring technology has continued to evolve and newly 

developed PM sensors are now estimated to be the primary method for detection of 

faults starting in the 2014 and 2015 model years. Such sensors are capable of 

evaluating the performance of the PM filter on virtually every driving cycle and have little 

or no connection to PM filter regeneration events. Given the importance of properlyoperating PM filters on every trip and the direction monitoring technology is headed, 

staff is proposing to require manufacturers to increment the denominators for these 

monitors when the general denominator criteria are met in lieu of only once per 800 

minutes of engine operation or 500 miles of vehicle operation starting in the 2016 model 

year for both heavy-duty engines and medium-duty vehicles. Further, for medium-duty 

vehicles, given the current higher ratio of 0.336 that these monitors are required to 

meet, staff is proposing to modify the OBD II regulation to lower the required ratio to 

0.100 for the first few years these monitors use this new denominator, 2016 through 

2018 model years, to give manufacturers more time to assess the monitoring frequency 

of the new monitoring technologies. 

Staff is also proposing amendments to the in-use monitor performance requirements for 

PM sensor and PM sensor heater monitors. The HD OBD regulation currently requires 

the PM sensor monitoring capability monitor (section 1971.1(e)(9.2.2)(D)) and the PM 

sensor heater monitor (section 1971.1(e)(9.2.4)(A)) to use the general denominator as 

the monitor denominators. PM sensors, like PM filters, may be regenerated infrequently 

in-use, which may make frequent monitoring difficult. Further, as opposed to oxygen 

sensor and NOx sensor heaters, PM sensor heaters may be used infrequently in-use. 

Manufacturers are concerned that using the general denominator may result in the 

denominator incrementing more often than is appropriate for the sensor technology and 

how it is used. Thus, staff is proposing to allow manufacturers to propose alternate 

criteria (for ARB review and approval) to increment the denominator for PM sensor 

monitoring capability monitors until further experience is gained and more appropriate 

criteria can be defined in the regulation. For PM sensor heater monitors, staff is 

proposing to amend the HD OBD regulation to require manufacturers to increment the 

denominator when, in addition to the general denominator criteria, the heater has been 

commanded to function for a cumulative time greater than or equal to ten seconds. 

Staff is also proposing changes to the ignition cycle counter requirements for heavyduty hybrid vehicles. Currently, manufacturers are required to track and report an 

ignition cycle counter, which is required to be incremented every time the vehicle is 
24

started (i.e., “engine start” is met). This is basically a counter of the number of driving 

cycles experienced by the vehicle. Staff is proposing to modify the incrementing criteria 

for hybrid vehicles under the HD OBD regulation to clarify that manufacturers increment 

the ignition cycle counter when the “propulsion system active” definition is met (e.g., 

each time the vehicle is operated, without respect to whether the engine is started or 

used). 

Lastly, staff is proposing changes to the tracking and reporting requirements in the HD 

OBD regulation and OBD II regulation. First, in the HD OBD regulation, staff is 

proposing to modify the diesel components/systems required to report in-use monitoring 

performance data (section 1971.1(d)(5.1.1)) to align with the requirements in SAE 

J1979 and J1939. Second, in both the HD OBD and medium-duty OBD II regulations, 

staff is proposing changes to the in-use performance tracking and reporting 

requirements for diesel NOx and PM sensor monitors. The regulation currently does 

not require manufacturers to track and report the diesel NOx/PM sensor “monitoring 

capability” monitors (sections 1971.1(e)(9.2.2)(D) and 1968.2(f)(5.2.2)(D)); it only 

requires manufacturers to track and report diesel NOx/PM sensor performance monitors 

that are emission threshold-based (sections 1971.1(e)(9.2.2)(A) and 

1968.2(f)(5.2.2)(A)). However, recent discussions between staff and manufacturers 

have indicated that many of these sensors do not have emission-threshold based 

monitors, and thus would only be subject to monitoring if the malfunction causes the 

sensor to no longer be sufficient for use as an OBD system monitoring device. 

Considering how important NOx and PM sensors are for monitoring of major 

aftertreatment emission control devices, they should be monitored to ensure that they 

are running frequently in-use. Thus, staff is proposing that the HD OBD and OBD II 

regulations be modified to require manufacturers to track and report the diesel NOx/PM 

sensor “monitoring capability” monitors for 2016 and subsequent model year heavy-duty 

engines and medium-duty vehicles. 

F. DIESEL MISFIRE MONITORING 

Diesel manufacturers are currently required to monitor for misfire only during engine idle 

conditions and only for faults that cause one or more cylinders to be continuously 

misfiring. This requirement was first proposed based on diesel manufacturers’ assertion 

that misfire only occurred due to poor compression and would result in a cylinder 

misfiring under all operating conditions. The OBD requirements also specify that, for 

2013 and subsequent model year heavy-duty diesel engines and 2010 and subsequent 

model year light- and medium-duty vehicles equipped with sensors that can detect 

combustion or combustion quality, diesel manufacturers are required to monitor for 

misfire continuously under all positive torque engine speeds and load conditions and to 

detect misfire before emissions exceed specific thresholds (e.g., 2.0 times the 

applicable standards). The premise for this was that engines so equipped would likely 

be more precisely controlling the combustion process based on information from these 

sensors such that misfires could likely exist only in limited operating regions. 
25

However, the complexity of today’s control strategies on all diesel engines and the 

addition of new technologies in recent years, like aggressive use of EGR or target airfuel ratios or fresh air concentrations in certain operating conditions, has resulted in 

additional factors that can cause misfire in very specific operating conditions instead of 

continuously under all conditions. Thus, even for diesel engines that do not have direct 

combustion quality sensors, staff is concerned that real world malfunctions will cause 

intermittent or off-idle misfires that increase emissions but go undetected with today’s 

monitors. As stated in the 2005 Staff Report when the HD OBD regulation was first 

adopted, staff intended to investigate the possibility of such misfires and had indicated 

that a more comprehensive requirement may be proposed at a future Board review 

based on their findings. Staff has found that in the field, misfire can occur during 

specific speed and load regions and would not likely be detected by an idle-only misfire 

monitor. Thus, staff worked on a proposal to require all 2016 and subsequent heavyduty and medium-duty diesel engines to continuously monitor for misfire in addition to 

the idle-only misfire monitor. 

Manufacturers have expressed several concerns about monitoring continuously for 

misfires and about establishing a level of misfire that would equate to a specific tailpipe 

emission level. They indicated that they would likely encounter difficulties in the highest 

engine speed and torque conditions and that there would be challenges in actually 

creating misfires in a repeatable manner without damaging the engine and representing 

a worst case emission scenario. As a result, they proposed that they be required to 

detect a fixed misfire rate of 5 percent in lieu of establishing the specific rate on an 

engine model basis that correlated to a specific tailpipe emission level. They also 

proposed that monitoring be limited to engine speeds and loads less than 75 percent of 

the maximum engine speed and load. 

Staff agrees that there are significant difficulties in creating a repeatable misfire on 

diesel engines that is representative of the worst case emissions and thus is proposing 

the manufacturers’ suggested solution of using a fixed percentage of 5 percent as the 

malfunction criterion for both heavy-duty engines and medium-duty vehicles. 

Concerning the continuous monitoring requirement, while staff agrees that some 

relaxation is necessary, there are still concerns and questions about the likelihood and 

possible effects of misfire during higher speed and load regions. Thus, for the interim 

model years of 2016 through 2018, staff modified the proposal to be consistent with the 

manufacturers’ proposal to limit monitoring to positive torque conditions with engine 

speed up to 75 percent of the maximum-rated engine speed and engine load up to 75 

percent maximum-rated load. Additionally, at the manufacturers’ suggestion, a small 

region of high engine speed and very low load was defined and is proposed as an area 

where monitoring would not be required. However, because staff is concerned that 

higher speed and load regions may very well be susceptible to misfire, the proposal also 

requires manufacturers to phase in monitoring all the way up to the maximum engine 

speed and load for the 2019 through 2021 model years. Further, manufacturers would 

be required to collect and report data demonstrating the compliance of the misfire 

monitor as part of the certification application, similar to what is currently required for 

gasoline vehicles and engines. Specifically, the manufacturers would be required to 
26

provide data demonstrating the probability of detection of misfire events of the misfire 

monitoring system over the required engine speed and load operating range and data 

identifying all disablement of misfire monitoring that occurs during a specified test cycle. 

These data would provide assurance that the misfire monitor is robust and enabled 

under the required conditions. In addition to the new proposed misfire monitor 

requirements, manufacturers would still be subject to the idle-only misfire monitor 

requirements. Staff expects that manufacturers will be able to meet both requirements 

with the revised monitor developed to cover the expanded speed and load ranges. 

However, in case unforeseen difficulties arise that prevent detection of the 5 percent 

misfire at idle, the manufacturers would have to retain the current idle monitor. This 

would help protect the credibility of the monitoring system capability in the eyes of repair 

technicians by avoiding the situation where a technician can identify that an engine has 

an obvious and severe misfire at idle but the OBD system is incapable of detecting it. 

Staff is proposing all these changes to both the HD OBD and medium-duty OBD II 

requirements. 

G. DIESEL EXHAUST GAS RECIRCULATION (EGR) SYSTEM MONITORING 

The HD OBD regulation currently requires manufacturers to monitor any EGR catalysts 

used in the EGR system on all 2013 and subsequent model year engines. Such 

catalysts, though not very common, are used to further clean up the exhaust gas before 

it is recirculated into the intake of the engine to reduce contamination or fouling that 

might otherwise affect durability of the EGR system. While failures of the EGR catalyst 

may not result in an immediate impact on emissions, such failures lead to more 

aggressive deterioration of other EGR system components such as fouling or plugging 

of the EGR cooler. 

Manufacturers have argued that OBD systems have always focused on the monitoring 

of components that directly influence emissions, not components that help to sustain the 

effectiveness or durability of the system. They have further argued that there are issues 

with detecting and pinpointing EGR catalyst failures as opposed to relying on other 

monitors such as the EGR cooler diagnostic to eventually detect the subsequent failure 

of the cooler itself. Thus, staff is proposing to modify the HD OBD regulation to exempt 

heavy-duty manufacturers from having to monitor the EGR catalyst if they can show that 

a fault of the catalyst will not cause a measurable emissions impact on the criteria 

pollutants (i.e., NMHC, CO, NOx, and PM) during any reasonable driving condition in 

which the catalyst is most likely to affect criteria pollutants. 
27

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

MONITORING 

The HD OBD regulation currently requires manufacturers to design the OBD system on 

2013 and subsequent model year engines to detect an NMHC catalyst malfunction 

when the catalyst conversion capability decreases to the point that NMHC emissions 

exceed 2.0 times the applicable standard. 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. 

Similar to what they argued during the 2009 HD OBD biennial review, manufacturers 

have again expressed concern 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. Accordingly, manufacturers have again 

asked ARB to raise the threshold to 4.0 times the NMHC standard so that 

manufacturers would very likely only have to implement functional monitors to detect 

completely failed catalysts. 

In the 2009 HD OBD staff report, staff detailed some possible monitoring approaches to 

meet the threshold monitoring requirements. To counter manufacturers argument 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, staff indicated in 

the 2009 report that after talking with suppliers and individual manufacturers, it had 

determined that catalysts do have intermediate levels of deterioration that cause 

increases in light-off temperature and lower conversion efficiencies. Staff found that 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). 

Manufacturers now argue that though there may be some validity to staff’s position, 

there are significant limitations including the narrow temperature and time window 

around catalyst light-off that the exotherm monitor must run. Staff also mentioned in the 

2009 staff report about a strategy to monitor the catalyst during a cold start, where 

during intrusive actions intended to bring the catalyst up to the desired temperature 

quickly after a cold start, the light-off and/or temperature rise characteristics are tracked 

to evaluate the catalyst. Manufacturers again argued there are limitations with this 

approach as well, with many factors including the condition of the catalyst that can 

affect catalyst warm-up, and note that most manufacturers have found that the cold start 

component monitor for the catalyst can only detect a completely failed catalyst. Lastly, 

staff mentioned in the 2009 staff report that manufacturers can also reduce the engineout NMHC emissions associated with a malfunctioning catalyst. Manufacturers have 

countered that lower engine-out NMHC emissions would mean higher engine-out NOx 
28

emissions, which would make it more difficult to meet the NOx-based monitoring 

requirements. 

In more recent discussions with manufacturers and suppliers, staff has found that some 

manufacturers have indeed been successful in incrementally aging the NMHC catalyst 

much like what has been done for over 15 years with gasoline catalysts. Additionally, 

virtually all manufacturers have indeed moved towards higher engine-out NOx emission 

levels (and generally, lower engine-out NMHC emission levels) to maximize efficiency 

and use of SCR systems as staff suggested was possible, thus requiring detection of a 

more degraded NMHC catalyst than before. Further, at least one manufacturer has 

already successfully demonstrated the ability to detect a degraded catalyst prior to 

emissions exceeding the current 2013 model year thresholds by monitoring the 

exotherm of the catalyst during regeneration events. Virtually all manufacturers have 

continued to make significant improvements to regeneration emissions both by 

increasing the time between regenerations and lowering the emissions during the actual 

regeneration events. This leads to reduced influences from the infrequent regeneration 

adjustment factors (IRAF), making it less of a factor in determining the threshold 

catalyst. Nonetheless, if a manufacturer were to choose a solution that still was very 

sensitive to NMHC catalyst degradation (due to high engine-out NMHC and/or high 

IRAFs), it is appropriate that such a solution be monitored at a reasonable emission 

level and not at something that is four times a standard that is already generous for 

diesel engines. Accordingly, staff is proposing no change in the current NMHC catalyst 

monitoring threshold. 

Staff is proposing amendments to the HD OBD requirement for manufacturers to 

monitor the ability of the catalyst to generate a desired feedgas (e.g., nitrogen dioxide 

(NO2)) to promote better performance in a downstream aftertreatment component (e.g., 

for higher NOx conversion efficiency in an SCR system). Currently, the regulation 

requires 2013 and subsequent heavy-duty model year engines to meet this 

requirement. During the most recent OBD II regulatory review for light- and mediumduty vehicles earlier this year, manufacturers asked ARB to delay the start date to meet 

this requirement to the 2016 model year in part because their original plans to comply 

were based on using monitors for the NMHC conversion efficiency of the NMHC 

catalyst and/or NOx conversion efficiency of the SCR system and such approaches 

were not uniformly successful. This resulted in manufacturers having to investigate 

alternative monitoring strategies, which indicated they needed more time to verify these 

strategies. While staff believes it is feasible to develop a monitor to meet this 

requirement and at least one manufacturer has already shown it will have this capability 

for the 2013 model year, staff acknowledges that more time is needed to develop a 

robust monitor to meet this requirement. Thus, to be consistent with what staff had 

recently proposed for the OBD II regulation, staff is proposing to modify the HD OBD 

regulation to delay monitoring of proper feedgas generation until the 2015 model year 

for heavy-duty engines. 

Further, manufacturers have indicated that ability of the catalyst to generate a desired 

feedgas (e.g., high levels of NO2) is a secondary function that often has very minor 
29

impacts. Manufacturers proposed that because the impacts are small, ARB should add 

test-out criteria that would allow an emissions increase of up to 15 percent of the 

standard due to a malfunction or loss of this feature before monitoring would be 

required. While the OBD programs at ARB have traditionally avoided this approach 

because of the concern that several ‘minor’ items could fail without fault detection and 

cumulatively lead to significantly higher emissions, or that two or more such failures 

could have an interaction that causes even higher emissions when both occur, staff has 

agreed to try such an approach here. Specifically, for this ‘secondary’ function of the 

NMHC catalyst (i.e., proper feedgas generation for downstream components), staff is 

proposing to modify the HD OBD and OBD II regulations to allow manufacturers to be 

exempt from monitoring if complete failure of the component or loss of the function 

results in less than a 15 percent of the standard increase for any pollutant over an 

applicable test cycle (e.g., Federal Test Procedure (FTP) or Supplemental Emission 

Test (SET)) during the engine’s useful life. However, in addition to being less than a 15 

percent of the standard increase, staff’s proposal would also require that tailpipe 

emissions be below the standard with the failure to better ensure that any emission 

impact is truly ‘minor.’ 

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

The HD OBD and medium-duty OBD II regulations require manufacturers to detect 

conversion efficiency faults of the NOx converting catalyst (typically an SCR catalyst) 

before NOx emissions exceed the following thresholds: for the 2010 through 2012 

model years, the applicable NOx standard plus 0.4 g/bhp-hr, and for the 2013 and 

subsequent model years, the applicable NOx standard plus 0.2 g/bhp-hr. 

Manufacturers have argued that the dynamics of the SCR system and its control, 

including the NOx sensors and the reductant delivery system, have made it difficult to 

meet the 2013 model year requirements. They contend that due to the high degree of 

conversion efficiency of the SCR catalyst, a system degraded to the level required to be 

detected by the OBD system is still a highly functioning SCR system and provides little 

separation from a properly performing one. They further contend that a good catalyst 

could resemble a bad catalyst since the instantaneous conversion efficiency can 

dramatically change given the operating conditions. Adding to the issue is the crosssensitivity of the NOx sensors to ammonia (NH3) and the less-than-desired accuracy of 

the sensors needed for robust monitoring. 

Staff has met with virtually every manufacturer and several suppliers to assess current 

capability and what improvements are available in the near term. While several 

medium-duty manufacturers are on track to meet the existing 2013 standards, most 

heavy-duty manufacturers are not. Given the importance of achieving and preserving 

the NOx benefits of the 0.2 g/bhp-hr tailpipe standard, staff is committed to continuing to 

drive to the limits of technical feasibility to achieve the lowest threshold possible. 

Further, given industry trends towards increasing engine-out NOx emissions even 

higher for engine efficiency improvements or greenhouse gas reductions, staff is 

concerned that some may try to push too far in that direction such that tailpipe or OBD 
30

capability is sacrificed. Thus, staff is cautious about providing even interim relaxation 

that could be misinterpreted as showing that some ARB requirements are more 

important than others instead of keeping manufacturers on track to find a reasonable 

middle ground that meets all of our requirements, including OBD, tailpipe standards, 

and greenhouse gas standards (where applicable). In discussions with the 

manufacturers, it seems there are many elements of base SCR control and dynamics 

that are not well refined or understood. The problem appears to be exacerbated on 

larger catalysts that are more common on the biggest engine displacements, and many 

point to unknowns related to ammonia storage and release that produce both 

inconsistent in-use conversion efficiency and, consequently, quite varied catalyst 

monitoring results. Last-minute changes to the underlying base emission control 

strategy has also placed the OBD engineers within manufacturers at a disadvantage by 

forcing them to either develop and calibrate on less-than-finalized software or wait until 

very late in the process to begin the calibration process. Those manufacturers with 

more stable emission control solutions that were finalized early in the process tend to be 

further ahead in OBD capability as well. 

When talking with manufacturers and suppliers, staff identified several items that 

continue to show promise for achieving the current 2013 model year threshold of the 

NOx tailpipe standard + 0.2 g/bhp-hr. NOx sensor accuracy is not expected to get 

appreciably better than the +/-10% and +/- 10 parts-per-million accuracy of current 

sensors, but that doesn’t appear to be the limiting factor to achieving the final 

thresholds. Some manufacturers have shifted some focus to looking more at ammonia 

storage—both for purposes of better controlling emissions in the first place and also for 

another metric to correlate with the performance of the catalyst itself. One supplier has 

indicated that ammonia storage capability is affected earlier and more dramatically on 

deteriorated catalysts than NOx sensor-based measurements can detect, implying that 

monitoring strategies based on or incorporating some measure of ammonia storage 

would likely be more sensitive and able to detect malfunctioning catalysts sooner. 

Some manufacturers have even incorporated (or plan to incorporate) ammonia sensors 

to better quantify and understand the storage and release phenomena. Some of these 

strategies may even include intrusive monitors that saturate and/or deplete ammonia 

storage to better assess the current catalyst performance. Others have indicated they 

plan to look at partial volume monitoring approaches to monitor the conversion 

efficiency over a smaller portion of the total catalyst volume in an attempt to be able to 

work in an environment with higher NOx outlet concentrations. To the extent that the 

smaller engines (and thus catalysts) are closer to achieving (if not already achieving) 

the 2013 model year thresholds, such an approach continues to have promise. 

Additionally, some manufacturers believe that they just need to get a better handle on 

what they are currently observing as high variability in the monitor results through better 

base control strategies, including adaptive algorithms, further refinement of enable 

conditions to eliminate driving conditions that cause big fluctuations in catalyst 

efficiency, and even improved statistical filtering of the results. 

Taking that all into consideration, staff is proposing a couple changes to the current HD 

OBD and OBD II requirement of a ‘+ 0.2’ threshold across the board in the 2013 model 
31

year. Specifically, staff is proposing that for medium-duty vehicles, which are already 

further along than some of their heavy-duty counterparts (primarily because of the 

smaller catalyst size, more constrained vehicle packages and usage patterns, and 

perhaps earlier timing for finalized base calibrations), manufacturers would be required 

to meet a threshold of ‘+0.3’ (i.e., the engine dynamometer standard + 0.3 g/bhp-hr) 

instead of the ‘+0.2’ current threshold for 2013 through 2015 model year medium-duty 

vehicles. For chassis dynamometer-certified applications, based on the current 

capability of several such products, a threshold of 2.0x the applicable standard would be 

used as a level that is consistent with section 1968.2(f)(17.1.5)(C), which requires the 

threshold be set as tight as technically feasible. 

For heavy-duty applications, staff is proposing to modify the 2013 model year threshold 

to remain at the ‘+0.4’ threshold that applied in 2012. However, starting with the 2014 

model year, manufacturers would be required to phase in a tighter threshold of ‘+0.3’. 

Specifically, manufacturers would have to meet the ‘+0.3’ threshold on 20 percent of 

their 2014 model year diesel engine volume and 50 percent of their 2015 model year 

diesel engine volume, with the percentages based on the manufacturer’s projected 

California sales volume of all heavy-duty diesel engines. For the 2016 model year, 

manufacturers would be required to meet the ‘+0.2’ threshold with the exception that 

any engines that were phased-in during 2014 or 2015 to the ‘+0.3’ threshold would be 

able to remain at that threshold in 2016 and would not have to meet the ‘+0.2’ threshold 

until the 2017 model year. This phase-in would force manufacturers to continue to push 

forward but allow them to focus their efforts on the engine models for which compliance 

is more straight forward in the early years as well as give them time to continue to 

evolve base calibration beyond what was done for the 2013 model year. Further, the 

carry-over provision for the 2016 model year would provide them relief from having to 

recalibrate their entire product line to meet the tighter threshold in that one year. The 

phase-in would also provide much needed time to improve ammonia storage 

estimations and explore alternative monitoring methods or metrics. 

Manufacturers raised questions about which heavy-duty engines could or could not be 

counted as part of the phase-in percentages for the heavy-duty OBD proposal. 

Specifically, whether only ‘parent’ ratings (those explicitly calibrated to emission 

thresholds and liable for them in-use) would count or if ‘child’ ratings (ratings with 

calibration that is extrapolated from the parent rating to be very similar but without 

explicit demonstration or in-use liability for the emission thresholds) could also be 

counted. Given the premise of parent and child ratings is that the parent is 

representative of the child and the extrapolated calibrations are intended to end up with 

compliant calibrations for the child ratings, the regulation would allow child ratings 

engines as well as parent ratings to count as part of the engine volume phase-in 

percentage. And while staff already scrutinizes the extrapolation method manufacturers 

use to establish an appropriate calibration on the child ratings, there is concern that 

manufacturers would take additional liberties when extrapolating the calibration for the 

tighter phase-in threshold. Specifically, staff is concerned that manufacturers would 

extrapolate towards a less stringent threshold in addition to making appropriate changes 

for the different rating. Accordingly, staff will likely be reviewing manufacturers’ 
32

extrapolation techniques and calibrations carefully to ensure that manufacturers are 

calibrating to an equivalent stringency for any ratings they are including in the phase-in 

percentages. 

J. DIESEL PARTICULATE MATTER (PM) FILTER MONITORING 

The HD 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 PM 

emissions exceed a specific threshold. For the 2010 through 2012 model year engines, 

the PM threshold was essentially 0.07 g/bhp-hr (for an engine certified to the nominal 

standard of 0.01 g/bhp-hr). For the one engine family in 2013 through 2015 where full 

OBD is phased-in, the threshold is 0.03 g/bhp-hr (for an engine certified to the nominal 

standard of 0.01 g/bhp-hr). For all other 2013 through 2015 model year engines, the 

PM threshold drops to 0.05 g/bhp-hr (again for an engine certified to the nominal 

standard of 0.01 g/bhp-hr). For all 2016 and subsequent model years, the threshold is 

0.03 g/bhp-hr (for an engine certified to the nominal standard of 0.01 g/bhp-hr). For 

medium-duty vehicles and engines covered under OBD II, the only difference from the 

above is that the 0.03 g/bhp-hr standard applies across the board in 2013 and 

subsequent model years in lieu of a phase-in on some products in 2013 and the rest in 

2016. 

The HD OBD regulation originally required manufacturers to meet the PM threshold of 

0.050 g/bhp-hr starting in the 2010 model year, but due to heavy-duty engine 

manufacturers’ concerns about meeting the threshold, staff amended the starting date 

to the 2013 model year based on projections that PM sensors, which many believe will 

be the only viable way to meet the thresholds, would be available in time for the 2013 

model year. Now manufacturers are still expressing concern that the threshold is too 

stringent and is not technically feasible for the 2013 model year time frame. They 

contend that PM sensors are not yet commercially ready across all of industry and thus, 

the emission threshold needs to be revised to what current monitoring technologies 

(primarily backpressure or delta pressure-based metrics) are capable of achieving. 

Accordingly, they proposed that heavy-duty engines continue to use the 2010 model 

year 0.07 g/bhp-hr PM threshold up to and including the 2015 model year, with 2016 

and subsequent model year engines using the PM threshold of 0.05 g/bhp-hr. 

As noted earlier, staff met with virtually every manufacturer and several suppliers to 

assess their monitoring capabilities for 2013 and the improvements they plan to 

implement in the near term. While at least one light-duty manufacturer is implementing 

a PM sensor in 2013 model year and a few heavy-duty manufacturers were on track to 

do that until very recently, staff generally agrees that PM sensors are not ready for full 

scale implementation in the 2013 model year. In some cases, manufacturers have 

indicated the 2014 model year is still viable for implementation on some of their 

products while others have indicated the 2015 model year is more likely. In most cases, 

the data from the sensors continue to indicate that they are certainly capable of 

detecting faults at the final PM threshold level of 0.03 g/bhp-hr. In meeting with sensor 
33

suppliers, staff has confirmed that wide-scale implementation of PM sensors in heavyduty engines is not feasible for the 2013 model year. 

In the absence of PM sensors, several manufacturers have continued to move forward 

on alternate monitoring techniques, including further refinement of delta pressure-based 

approaches and concepts such as a downstream secondary filter optimized for 

monitoring capability. In some cases, especially on medium-duty products, such 

techniques have already achieved the emission level of the 2016 threshold. However, 

some of these monitoring strategies still rely on relaxed provisions provided in the 

regulation (and recently extended through the 2013 model year for medium-duty) to 

allow ARB to exclude certain failure modes such as a partially melted and partially 

cracked filter that results in the identical delta pressure characteristics of a good filter. 

Such relaxation is set to expire in 2014 for medium-duty because it provides an 

unknown risk for failures that cause high PM emissions to go undetected, but was seen 

as a necessary interim step to accommodate the best available monitoring techniques. 

Lastly, as most in industry continue to move towards higher engine-out NOx emission 

levels, this necessarily results in lower engine-out PM levels. As engine-out levels 

decrease, the amount of degradation of the PM filter the engine can handle before the 

emission threshold is reached is substantially increased. In some cases, engine-out 

levels are reaching 0.05 g/bhp-hr or lower, which in turn means a PM filter would need 

to drop from a 95 percent or higher trapping efficiency down to something less than 60 

percent efficiency to reach the threshold of 0.03 g/bhp-hr. 

Taking all this into account, staff is proposing a variety of changes to the thresholds 

including a couple of phase–in options to provide some interim relaxation. With minor 

exceptions depending on the phase-in options selected, medium-duty and heavy-duty 

applications would all have the same end point for all 2016 and subsequent model year 

engines: PM threshold levels of 0.03 g/bhp-hr and no provision for exclusion of certain 

failure modes. PM sensors are certainly on track to be available across industry before 

that timeframe so that is a viable solution to meet the requirements. 

Staff is proposing the following changes to the OBD II regulation for medium-duty 

vehicles. For the 2013 model year, staff is proposing that the PM threshold for mediumduty vehicles remain at 0.03 g/bhp-hr; but with amendments previously approved in 

January 2012, manufacturers will be able to receive ARB approval to exclude specific 

failure modes. For 2014 and 2015 model year, medium-duty manufacturers would have 

two options. First, they could choose to implement monitoring to a PM threshold of 0.03 

g/bhp-hr without the failure mode exemptions on at least 20 percent of their 2014 and 

2015 annual model year medium-duty diesel vehicle volume, and certify the remaining 

vehicles to the 0.03 g/bhp-hr threshold with the failure mode exemption. Alternatively, a 

manufacturer could chose to continue to meet the 2013 threshold with failure mode 

exemption in the 2014 model year. However, for the 2015 model year, the 

manufacturer choosing this second path would need to certify at least 50 percent of its 

2015 model year medium-duty diesel volume to the threshold of 0.03 without the failure 

mode exemption. These two options provide manufacturers the flexibility to either 
34

implement earlier (2014 model year) on a smaller portion of their fleet or implement later 

(2015 model year) but on a larger fraction of their fleet. 

Staff is proposing the following changes to the HD OBD regulation. For 2013 model 

year heavy-duty engines, staff is proposing the PM threshold of 0.05 g/bhp-hr apply to 

all engines and to retain the provision for ARB to exempt certain failure modes. For 

2014 and 2015 model year heavy-duty engines, staff is proposing two options. First, 

manufacturers can choose to certify 20 percent of their 2014 through 2015 model 

annual year heavy-duty diesel engine volume to a PM threshold of 0.05 without the 

failure mode exemption. The remaining engines can again be certified to the 

0.05 g/bhp-hr threshold with the exemption of certain failure modes. Additionally, 

manufacturers using this alternative would be allowed to carry-over the 0.05 threshold 

without the failure mode exemption into the 2016 model year on engines first certified to 

this option in the 2014 model year. This would provide an extra year at the higher 

threshold on those engines brought in early and allow the manufacturer to avoid having 

to recalibrate all of its products in 2016 to the lower 0.03 threshold. As an alternative, 

manufacturers could choose to certify the 2014 model year engines to the same 

requirements as the 2013 model year -- a PM threshold of 0.05 g/bhp-hr with failure 

mode exemption. Those choosing this second option, however, would be required to 

certify 50 percent of their 2015 model year diesel engine volume to a PM threshold of 

0.03 g/bhp-hr without the failure mode exemption. Manufacturers choosing this second 

option would also be required to meet the 0.03 threshold without failure mode 

exemption on all 2016 model year engines. As mentioned in the diesel NOx catalyst 

monitoring discussion above, manufacturers would be allowed to include child ratings in 

the phase-in percentages to the extent they are extrapolated from a parent rating that 

meets the tighter threshold. 

The HD OBD regulation also currently requires manufacturers to monitor the NMHC 

conversion capability of catalyzed PM filters starting with the 2013 model year. The 

catalyzed coating of a PM filter has secondary functions that have an emission impact. 

These functions can include promotion of passive regeneration at lower exhaust 

temperatures, conversion of HC and carbon monoxide created during an active 

regeneration, and generation of NO2 feedgas for downstream SCR systems. 

Manufacturers have argued that many of these functions are just side effects that 

directionally help, but are not necessary to comply with the emission standards. They 

further indicated that there are currently no suitable robust monitoring strategies 

available to discern the proper operation of these secondary functions. Thus, 

manufacturers have asked ARB to delay the start date to meet this requirement to the 

2016 model year. 

Staff believes that such secondary functions are not trivial and warrant monitoring to 

ensure overall effectiveness of the emission control system. Staff recognizes that the 

success of the monitoring approaches 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) and thus require 

manufacturers to take OBD monitoring capability into consideration when designing and 
35

implementing the aftertreatment system and control strategy. It further recognizes that 

manufacturer OBD engineers have often been left out of the design process due to the 

rapid deployment of new technologies and increasingly stringent standards. Thus, 

consistent with the Board’s approval of amendments to the OBD II regulation in January 

2012, staff is proposing to delay the monitoring requirements of the catalyst function of 

catalyzed PM filters until the 2015 model year for heavy-duty engines to give 

manufacturers more time to refine their systems, optimize regeneration strategies, and 

better investigate the impacts of the catalyzed PM filter. 

Staff is also proposing that for 2016 and subsequent model year engines that use 

catalyzed PM filters to generate feedgas constituency (e.g., NO2) to assist SCR 

systems, manufacturers be required to monitor the capability of the system to generate 

desired feedgas. Currently, the HD OBD regulation specifically requires that 

manufacturers monitor the NMHC catalyst for proper feedgas generation for the SCR 

system, since this seems to be the primary component used to generate such feedgas. 

Through discussions with manufacturers, staff has learned that catalyzed PM filters are 

also used to generate such feedgas. Thus, staff’s proposal would require the 

monitoring of all components that generate the desirable feedgas. 

Lastly, similar to what is discussed above for proper feedgas monitoring of NMHC 

catalysts in section II.H., manufacturers have indicated that the abilities of the catalyzed 

PM filter to convert NMHC and to generate a desired feedgas (e.g., high levels of NO2) 

are secondary functions that often have very minor impacts. While not arguing that 

such functions do not have any emission impact and should not monitored, the 

manufacturers propose that because the impacts are small, ARB should add test-out 

criteria, specifically allowing an emissions increase of up to 15 percent of the standard 

due to a malfunction or loss of this feature before monitoring would be required. While 

the OBD programs at ARB have traditionally avoided this approach because of the 

concern that several ‘minor’ items could fail without fault detection and cumulatively lead 

to significantly higher emissions, or that two or more such failures could have an 

interaction that causes even higher emissions when both occur, staff has agreed to try 

such an approach here. Specifically, for both of these ‘secondary’ functions of a PM 

filter (i.e., NMHC conversion due to a catalyzed coating and proper feedgas generation 

for downstream components), staff is proposing to allow manufacturers to be exempt 

from monitoring if complete failure of the component or loss of the function results in 

less than a 15 percent of the standard increase for any pollutant over an applicable test 

cycle (e.g., FTP or SET) during the useful life. However, in addition to being less than a 

15 percent of the standard increase, staff’s proposal would also require that tailpipe 

emissions be below the standard with the failure to better ensure that any emission 

impact is truly ‘minor’. These proposed changes would apply to both the HD OBD and 

OBD II regulations. 

K. DIESEL NOx SENSOR MONITORING 

The HD OBD and medium-duty OBD II regulations currently require manufacturers to 

detect faults of the NOx sensor before emissions exceed the following thresholds: for 
36

the 2010 through 2012 model years, the applicable NOx standard plus 0.4 g/bhp-hr, and 

for the 2013 and subsequent model years, the applicable NOx standard plus 0.2 g/bhphr. Manufacturers have argued that they are unable to meet the 2013 model year 

thresholds given the current NOx sensor technology – specifically, considering the 

tolerances of the latest NOx sensors, they claimed there is too little separation between 

good sensors and bad sensors to ensure robust detection. Thus, they proposed that 

staff delay the 2013 model year thresholds until a later model year. 

For sensors upstream of the NOx converting catalyst, there are fewer items affecting 

the output of the sensor condition. Accordingly, most manufacturers have monitoring 

strategies based on comparing an expected/modeled engine-out emission level to the 

sensor output. And while the better sensor accuracy at the higher NOx concentrations 

read by the upstream sensor generally improves the situation, there are still several 

factors affecting the sensor output and accuracy of the estimated engine out emission 

levels that impact what emission level a fault can be detected. Further, manufacturers 

are still refining these diagnostics including improving accuracy of engine-out models 

and sensor adaptation strategies to compensate for any sensor drift. 

For NOx sensors located downstream of the NOx converting catalyst, the sensor output 

is affected by the condition of the catalyst itself. As such, it is difficult to discern sensor 

malfunctions from catalyst system malfunctions. For the most part, manufacturers have 

come up with separate diagnostics to discern the likely root cause and be able to direct 

a repair technician to a troubleshooting procedure that focuses on the likely cause. 

However, these sensor diagnostics are generally only able to detect malfunctions at the 

same emission level as the catalyst diagnostic itself. 

Accordingly, staff is proposing that the HD OBD and OBD II regulations be modified to 

require identical thresholds for NOx sensors as those being proposed for NOx 

converting catalyst monitoring (described in section I above). Specifically, staff is 

proposing that for 2013 model year medium-duty vehicles, manufacturers would be 

required to meet a threshold of ‘+0.3’ (i.e., the engine dynamometer standard + 0.3 

g/bhp-hr) instead of the ‘+0.2’ current threshold. For heavy-duty applications, staff is 

proposing to modify the 2013 model year threshold to remain at the ‘+0.4’ threshold that 

applied in 2012. However, starting with the 2014 model year, manufacturers would be 

required to phase in a tighter threshold of ‘+0.3’. Specifically, manufacturers would 

have to meet the ‘+0.3’ threshold on 20 percent of their 2014 model year heavy-duty 

engine volume and 50 percent of their 2015 model year heavy-duty engine volume. For 

the 2016 model year, manufacturers would be required to meet the ‘+0.2’ threshold with 

the exception that any products that were phased-in during 2014 or 2015 to the ‘+0.3’ 

threshold would be able to remain at that threshold in 2016 and would not have to meet 

the ‘+0.2’ threshold until the 2017 model year. As already stated in section I for NOx 

catalyst monitoring, this phase-in would force manufacturers to continue to push forward 

but allow them to focus their efforts on engines in which compliance is more straightforward in the early years as well as give them time to continue to evolve base 

calibration beyond what was done for the 2013 model year. Further, the carry-over 

provision for the 2016 model year would provide them relief from having to recalibrate 

their entire product line to meet the tighter threshold in that one year. 
37

Further, staff is also proposing NMHC malfunction thresholds for the NOx/PM sensor 

performance monitoring requirements in the HD OBD regulation. Specifically, in 

addition to the NOx and PM malfunction thresholds currently required (e.g., detect a 

NOx sensor fault before NOx emissions or PM emissions, whichever happens first, 

exceed a specified level), manufacturers would be required to detect a sensor 

performance fault before NMHC emissions exceed 2.0 times the standards starting in 

the 2016 model year. The proposed NMHC thresholds would be consistent with the 

thresholds currently required for diesel NOx catalyst monitoring. In virtually all cases, 

staff does not expect this change to alter the current calibration or sensitivity of NOx or 

PM sensor diagnostics because NOx and PM emissions will likely be the two most 

sensitive pollutants and have the biggest emission impact. However, to be thorough 

and to protect against unforeseen interactions or control strategies, the change would 

ensure that a fault is detected before any one of the pollutants exceeds a defined 

threshold. 

L. GASOLINE MISFIRE MONITORING 

The HD OBD regulation currently requires manufacturers to continuously monitor for 

misfire faults from no later than the end of the second crankshaft revolution after engine 

start and, for engines that employ shutoff strategies (e.g., hybrid vehicles that shut off 

the engine at idle), no later than the end of the second crankshaft revolution after each 

engine restart. The term “engine start” is currently being used in the regulation for many 

requirements with the intent that “engine start” signifies the start of vehicle operation, 

which may or may not involve the engine actually being started in a hybrid vehicle. To 

avoid confusion about when exactly misfire monitoring is required to resume after the 

engine is shutoff, staff is proposing to revise the language to require manufacturers to 

monitor for misfire faults from no later than the end of the second crankshaft revolution 

after “engine fueling begins for the initial start and after each time fueling resumes.” 

M. GASOLINE SECONDARY AIR SYSTEM MONITORING 

The HD OBD regulation currently requires manufacturers to monitor the secondary air 

system for malfunction prior to either a decrease or an increase from the manufacturer’s 

specified air flow that would cause emissions to exceed 1.5 times the standards. 

Further, if no fault that causes a decrease or an increase in air flow could cause 

emissions to exceed 1.5 times the standards, the manufacturer is required to detect a 

fault when “no detectable amount of air flow is delivered during normal operation of the 

secondary air system.” Manufacturers are presently not required to do a functional 

monitor for increases in air flow that do not cause emissions to exceed 1.5 times the 

standards. Consistent with what is required for other component/system monitors, staff 

believes that complete coverage of faults is needed for secondary air systems as well.

Thus, staff is proposing to modify the language to require manufacturers to detect a 

fault when no detectable amount of air flow is delivered only if no fault that causes a 

decrease in air flow could cause emissions to exceed the threshold. Further, staff is 

proposing that if no fault that causes an increase in air flow could cause emissions to 
38

exceed the threshold, the manufacturer would be required to detect a fault when the 

system has reached its control limits such that it cannot reduce air flow during normal 

operation of the secondary air system. 

N. ENGINE COOLING SYSTEM MONITORING 

The HD OBD regulation requires manufacturers to monitor cooling systems for 

malfunctions that affect emissions or other 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 thermostat malfunctions if either of the following occurs: (i) the 

engine coolant temperature (ECT) does not reach the highest temperature required by 

the OBD system to enable other diagnostics, or (ii) the ECT does not reach a warmedup temperature within 20 degrees Fahrenheit of the engine manufacturer’s nominal 

thermostat regulating temperature. Currently the regulation requires this thermostat 

monitor to be enabled “on every driving cycle in which the ECT sensor indicates, at 

engine start, a temperature lower than the” threshold temperature, but the regulation 

also indicates that ARB will not approve “disablement of the monitor on engine starts 

where the ECT at engine start is more than 35 degrees Fahrenheit lower than the” 

threshold temperature. The language has caused confusion about when the thermostat 

monitor is allowed to be enabled on a given driving cycle. Thus, staff is proposing 

clarifications to the HD OBD language to make clear when the thermostat monitor can 

be enabled. Essentially, the manufacturer would be required to disable the thermostat 

monitor on driving cycles where the ECT at start is within 35 degrees Fahrenheit of the 

thermostat monitor malfunction threshold temperature to avoid false passes when 

cooling system faults are present but still manage to warm the system up by a few 

degrees. However, manufacturers would be able to request Executive Officer approval 

to enable the monitor if the ECT at start is within a portion of this region (e.g., if the 

malfunction threshold temperature is 160 degrees Fahrenheit, the manufacturer may 

request approval to enable the monitor for a portion of the temperature region above 

125 degrees but still below 160 degrees Fahrenheit) provided they submit data 

demonstrating that the monitor can indeed robustly detect thermostat malfunctions and 

is not at risk for false passing when starting at engine temperatures in those regions. 

O. COMPREHENSIVE COMPONENT MONITORING 

The HD OBD regulation currently requires diesel manufacturers to detect faults of the 

idle control system if, among other things, the fuel injection quantity is “not within 

+/-50 percent of the fuel quantity necessary to achieve the target idle speed for a 

properly functioning engine and the given operating conditions.” Manufacturers have 

expressed concern that not all the “given operating conditions” are known to 

manufacturers, making it hard to determine what the appropriate fuel quantity to achieve 

the target idle speed should be and, consequently, whether or not there actually is a 

fault. Staff is proposing to modify the language to require detection of idle control 
39

system faults of the fuel quantity in relation to achieving the target idle speed for 

“known”, not “given,” operating conditions. 

The HD OBD regulation currently requires manufacturers 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 on 2013 

and subsequent model year engines. Examples of these include individually coded 

injector flow characteristics and fuel pumps that use in-line resistors to correct 

differences in fuel pump volume output. Monitoring of the components would ensure 

that misassembled systems, erroneous programming, or incomplete repair procedures 

that result in incorrect adjustment being applied (and consequently, increases in 

emission levels) will be detected. Manufacturers have questioned the need to monitor 

this feature and have expressed concern about meeting this requirement in the 2013 

timeframe. They additionally stated that the fuel system monitoring requirements 

already require detection of emission-related malfunctions for pressure control, timing, 

and quantity. Light- and medium-duty manufacturers, who are also required to monitor 

this feature, have indicated they have been working hard on improvements to their fuel 

system adaptive strategies to fully compensate or learn out any errors that may occur 

due to mismatches in the injector and the programmed tolerance/adjustment. This 

would allow manufacturers to avoid adding new hardware, such as a communication 

chip in the injector that would automatically communicate its characteristics to the 

engine computer, and avoid other alternatives such as tighter tolerances on the 

injectors to meet this requirement. Staff believes that heavy-duty manufacturers could 

also take the same approach. Thus, consistent with what was approved by the Board in 

January 2012 for light- and medium-duty diesel vehicles under the OBD II regulation, 

staff is proposing to modify the HD OBD regulation to delay the monitoring requirement 

of this feature until the 2015 model year for heavy-duty engines. Such a delay should 

give sufficient time for manufacturers to fully refine adaptive strategies so that they can 

compensate for any mismatches that occur or to determine that such strategies are 

ineffective and implement an alternative method such as those previously mentioned. 

Additionally, as discussed early in sections II.H. and II.J., manufacturers have requested 

that this monitor be subject to test-out criteria allowing manufacturers to be exempted 

from monitoring if the impact is less than 15 percent of the standard. While many 

manufacturers seem to be making great strides in adaptive strategies that nearly fully 

compensate for mismatches, achieving complete compensation may prove to be very 

difficult. Accordingly, staff is proposing to also apply test-out criteria to features that fall 

under this provision. Specifically, mismatches or faults that cause less than a 15 

percent of the standard increase in emissions and are below the emission standard 

would be exempt from monitoring. However, because this function is often on multiple 

components (e.g., all injectors) and the severity of the fault can vary by how far off the 

mismatch is, staff is proposing that manufacturers be required to submit a test plan for 

Executive Officer approval of the test procedures and combination of failed parts and 

the degree to which they are a mismatch that will be used for the test-out. While staff 

would normally take the position of the worst-case scenario (e.g.., all injectors with a 

mismatch and with the largest mismatch possible), such a scenario is statistically 
40

virtually impossible and not very representative of the type of mismatches that happen 

in the real world. Accordingly, staff is proposing to give some additional latitude to 

manufacturers to propose a more realistic scenario based on the distribution of parts 

and likely in-use scenarios. Staff’s intent is for the manufacturers to identify a 

reasonable bound within which most replacement parts would fall (e.g., perhaps within 

one sigma from the median part) and propose a test condition that would represent a 

reasonable worst case emissions scenario within those bounds. These proposed 

changes would apply to both the HD OBD and OBD II regulations. 

P. STANDARDIZATION REQUIREMENTS 

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. 

Diagnostic Connector and Communication Protocol: 

Staff is also proposing amendments to the diagnostic connector and protocol 

requirements in the HD OBD regulation. Staff is proposing specific language clarifying 

the use of SAE J1939 for diesel manufacturers. When the HD OBD regulation was first 

adopted, SAE J1939 only had a 250 kbps baud rate version of the protocol and a single 

connector. However, since originally adopted, SAE J1939 had been updated to include 

an additional 500 kbps baud rate version of the protocol and a second version of the 

connector itself (i.e., the “Type 2” version) to handle the new baud rate. While staff 

initially objected to the addition of a second baud rate and second connector on the 

grounds that it was undermining the intent of standardization by creating more 

permutations, industry has indicated that the 250 kbps baud rate is likely to have 

insufficient bandwidth to handle all of the required message traffic in the near future. 

Further, the “Type 2” connector has been designed to be backwards compatible with 

both baud rates such that any technician or inspection entities would be able to 

purchase a single connector that would cover both variants. With this standardization 

first applying in the 2013 model year, it is also expected that a minimal amount of 

entities have already ‘tooled up’ for the “Type 1” connector and could jump straight to 

the “Type 2” connector for their equipment purchases. While two baud rates will 

generate more work for the tool and equipment manufacturers because they will have to 

validate their equipment on a sufficient number of vehicles on each of the two baud 

rates, the baud rate change is a fairly minor permutation. Several J1939 committee 

members have also committed to ensuring that the J1939 specification contains enough 

direction to tool manufacturers on how to accurately determine the appropriate baud 

rate when first connected to a vehicle. Thus, staff is proposing to amend the HD OBD 

regulation to clarify the combinations of baud rate and connectors that are allowed in 

the near term (prior to 2016 model year) and that the 500 kbps variant (and associated 

“Type 2” connector) would be the only allowed variant for 2016 and subsequent model 

years to align with industry’s likely timeframe for switching to the higher baud rate. 
41

Based on light-duty experience, staff is also proposing that the HD OBD regulation be 

amended to prohibit manufacturers from putting an additional identical standardized 

connector (i.e., an SAE J1939 connector or “Type A” SAE J1962 connector) used for 

non-OBD purposes in the same area where the standardized OBD diagnostic connector 

is required to be located. This would help avoid confusion among technicians or 

inspectors attempting to identify the ‘correct’ diagnostic connector to retrieve OBD 

information from the vehicle. Manufacturers would still be allowed to equip their 

engines and vehicles with additional diagnostic connectors as needed but, if they 

choose additional connectors that are identical to the standardized one, they would not 

be allowed to install those connectors in the driver footwell area where the HD OBD 

connector is required to be.

Readiness Status: 

Staff is also proposing amendments to the readiness status requirements in the HD 

OBD regulation. Manufacturers are presently required to incorporate readiness status 

indications of several major emission control systems and components into their OBD 

systems, which helps determine if the OBD monitors have performed their system 

evaluations. When the OBD system is interrogated by an off-board tool, the system is 

to report a readiness status for each major emission-related component of either 

“complete” (if the monitor has run a sufficient number of times to detect a malfunction 

since the memory was last cleared), “incomplete” (if the monitor has not yet had the 

chance to run since the memory was last cleared), or “not applicable” (if the monitored 

component in question is not equipped or monitored on the vehicle). The main intent of 

the readiness status is to ensure an engine or vehicle is ready for an OBD-based 

inspection (i.e., that monitors have run prior to inspection). Technicians also can use 

the readiness status to verify OBD-related repairs. With the current language, however, 

there has been confusion about which monitors manufacturers are required to include 

when determining readiness status for each component/system. Further, 

manufacturers have expressed concern that certain diesel-related monitors may take 

too long to run and complete (e.g., monitors that require PM filter regenerations to 

occur), which would unnecessarily delay setting of the readiness status to “complete”. 

While staff understands manufacturers’ concerns regarding this last point, staff believes 

it is important to include most monitors of the primary emission controls on the engine, 

even though they make take time to complete. Staff, however, is proposing revisions 

that would clarify exactly which monitors are required to be included when determining 

readiness status to ensure consistency in implementation among all manufacturers. 

Staff is also proposing additional amendments to correct confusion related to 

implementing the readiness requirements, including specific language on how to deal 

with monitors that detect faults of more than one major emission-related component 

(e.g., an oxygen sensor monitor that is used to detect both oxygen sensor faults that are 

tied to the oxygen sensor readiness bit and air-fuel ratio cylinder imbalance faults that 

are tied to the fuel system readiness bit). Lastly, staff is proposing to delete the current 

requirement that allows manufacturers to request Executive Officer approval to set the 

readiness status to “complete” without monitoring actually having been completed if 

monitoring is disabled on multiple driving cycles due to extreme operating conditions 
42

(e.g., cold ambient temperatures, high altitudes). This requirement was originally 

carried over from the OBD II requirements, where staff allowed a showing of complete 

status to avoid light- and medium-duty vehicles from failing inspection and maintenance 

tests due to unset readiness bits solely because the vehicle was being operated in 

extreme conditions (e.g., high altitude, very cold temperatures, etc.) in which monitoring 

was routinely disabled. However, given that heavy-duty vehicles do not undergo 

periodic inspections, staff believes this condition is not needed. 

Data Stream Parameters: 

Staff is proposing some modifications to the data stream parameters that are required to 

be made available in the HD OBD regulation. First, staff is proposing the addition of 

three parameters for all 2016 and subsequent model year heavy-duty diesel engines. 

Specifically, manufacturers would be required to report fuel rate, actual engine torque 

including fan/accessory torque, and modeled exhaust flow (mass/time). These three 

parameters are intended to make it easier to conduct valid in-use emission tests with 

portable emission measurement systems (PEMS) and as such, also are referenced in 

section 1971.1(h)(4.2.2)(H) as needed to be reported as accurately as available in the 

applicable electronic control module to facilitate accurate testing. Regarding fuel rate, 

this parameter is already required on diesel engines ‘if equipped’ but this change will 

ensure all diesel engines support it and by including reference in section 

1971.1(h)(4.2.2)(H), the resolution of the fuel rate parameter will likely need to be 

improved beyond what is currently reported on some vehicles as suspect parameter 

number (SPN) 183 in the SAE J1939 standard. Regarding engine torque, several 

manufacturers have indicated that the engine torque value commonly available is torque 

after fan or other engine accessory torque has been subtracted. This effectively 

underreports the torque being produced by the engine and results in less accurate 

calculations of a g/bhp-hr emission rate during in-use testing. Accordingly, the 

amendments would ensure the most accurate total engine torque number is available 

for testing. Staff is also proposing additional data stream parameters to be made 

available on engines so equipped – specifically, starting with the 2016 model year, 

manufacturers of engines equipped with reductant quality sensors would be required to 

output such sensor data in a standardized format to a scan tool. Further, 2016 and 

subsequent engines with NOx sensors would be required to output a ‘corrected’ NOx 

sensor signal in addition to the raw NOx sensor signal currently available. In 

discussions with manufacturers, several have indicated that they have corrections or 

adaptions they apply to the raw signal within the engine or aftertreatment control 

modules to account for the ammonia cross-sensitivity of the sensor or auto-zero or other 

adaption strategies that are used to adjust the raw signal. Given the control systems 

would likely be acting on this corrected signal rather than the raw signal, it could prove 

to be valuable information for technicians when troubleshooting detected malfunctions. 

Lastly, staff is proposing to identify the specific SPNs that manufacturers must use for 

the required data stream parameters “normalized trigger for PM filter regeneration” and 

“PM filter regeneration status”. In these specific cases, SAE J1939 contains more than 

one SPN that is related or very similar to these parameters, which may result in an 

engine utilizing a different SPN than another engine for the same parameter or 
43

confusion among manufacturers as to which variant of the parameter they should be 

supporting. So while manufacturers are required to report both these data parameters 

starting with the 2013 model year and different manufacturers will likely meet this 

requirement by supporting different SPNs, staff is proposing to clarify which exact SPN 

manufacturers should be using to meet these requirements starting in the 2016 model 

year to ensure consistent implementation across all manufacturers. 

Erasure of Emission-Related Information: 

Staff is also proposing amendments related to the erasure of emission-related 

information. Currently, the HD OBD regulation allows permanent fault codes to be 

erased when the individual control module containing the permanent fault code is 

reprogrammed and the vehicle/engine readiness status for all monitors (in all emissionrelated modules) is set to “not complete”. The regulation similarly requires all emissionrelated information (from all emission-related modules) to be erased in conjunction with 

the reprogramming of the vehicle identification number (VIN) or engine serial number 

(ESN). Manufacturers have argued that actions that affect only certain control modules 

(e.g., erasing a permanent fault code stored in just the engine control module) should 

not require resetting of readiness bits or erasing of emission-related information from 

“all” control modules, and that such ‘coordinated clearing’ can be difficult to achieve. 

The rationale for clearing all information was to reduce the opportunity for selective 

reprogramming events to be used to evade detection during inspections or avoid 

necessary repairs. However, staff agrees that a change is appropriate while still 

meeting the original intent. Specifically, the primary objective was to ensure that 

readiness status for the major monitors was reset to “not complete” to provide an 

obvious indication that some or all relevant information to an inspection had recently 

been altered or erased. Given that many modules do not support readiness bits or only 

support the comprehensive components readiness bit (which, by design, immediately 

reports “complete” even after a code clear event), staff is proposing that such 

reprogramming events must ensure a readiness reset only in modules that support 

readiness for major components (i.e., any readiness bits other than comprehensive 

components). While this does still require some form of ‘coordinated’ code clearing, it 

limits the number of involved modules. For example, if a vehicle has an engine control 

unit (ECU) that supports readiness for major components and five auxiliary emissionrelated modules that don’t support readiness for any major components, and if one of 

the auxiliary modules has a permanent fault code stored and that module is 

reprogrammed and erases the permanent fault code, the OBD system would only need 

to ensure that the engine ECU resets all readiness bits and not that all five of the 

auxiliary modules also reset readiness. 

Calibration Verification Number (CVN): 

Staff is proposing amendments to the CVN requirements. The HD OBD regulation 

currently requires the CVN to be stored at all times, calculated, and re-stored at least 

once per ignition cycle, and to be made immediately available at all times through the 

data link connector to a generic scan tool in accordance with the requirements in SAE 

J1979 or J1939. The only exceptions allowed in the regulation are for extreme 

circumstances where the stored value has been erased and not had an opportunity to 
44

be calculated and re-stored yet. Specifically, relief is granted from having the CVN 

immediately available to a scan tool if it is requested within 60 seconds of the ECU 

being reprogrammed or having non-volatile memory cleared, or within 30 seconds of a 

volatile memory clear or battery disconnect. A few manufacturers have indicated that 

the timeframes of 60 and 30 seconds might be insufficient to recalculate a new CVN 

and have it available. To address this, staff is proposing to modify the HD OBD 

regulation to clarify these timeframes and the associated events that are allowed and to 

clarify that, at all other times, immediately available means the value is returned to the 

requesting scan tool within the normal message response timing and does not allow for 

any extended message response timings or negative response codes. Additionally, 

given the very limited and rare scenarios in which the 60 and 30 second timeframes 

apply, staff is proposing to extend the timeframe to 120 seconds for both situations. 

Q. CERTIFICATION DEMONSTRATION TESTING REQUIREMENTS 

The HD OBD and OBD II regulations require 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. The HD OBD and OBD II regulations 

currently require manufacturers to perform demonstration testing of the diesel full speed 

and load misfire monitor on heavy-duty engines and medium-duty vehicles, since the 

monitors are calibrated to a tailpipe emission threshold and demonstration testing is 

used to verify such calibrations are correct. However, as explained in section F. above, 

staff is proposing to require manufacturers to detect misfire when the percentage of 

misfire exceeds a certain level (i.e., 5 percent) in lieu of the emission threshold-based 

malfunction criteria. Due to this change, staff is proposing to modify both the HD OBD 

and OBD II regulations to exempt manufacturers from having to perform demonstration 

testing of diesel misfire monitors using this new malfunction criterion. 

The HD OBD regulation currently contains language detailing the testing required for 

gasoline fuel system monitoring. Staff, however, forgot to include specific language for 

the air-fuel ratio cylinder imbalance monitor, which is one part of the gasoline fuel 

system monitoring requirements, so staff is proposing language detailing the testing 

requirements for this monitor. Further, the regulation currently requires that “for 

purposes of fuel system testing, the fault(s) induced may result in uniform distribution of 

fuel and air among the cylinders” and that “non-uniform distribution of fuel and air used 

to induce a fault may not cause misfire.” While this language works for testing of the 

main fuel system feedback monitor, it doesn’t apply to testing of other fuel system 

monitors such as the air-fuel cylinder imbalance monitor, which, by definition is ‘nonuniform’ and in some cases produce misfire. Therefore, staff is proposing amendments 

to the HD OBD regulation to limit this language to testing of the main fuel system 

feedback monitor. 

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

oxygen sensor emission threshold-based monitors to limit the number of tests required 

to be performed. Specifically, for conventional oxygen sensors, the manufacturer would 

be required to perform a test for two malfunction cases: (1) the single worst case 
45

response rate malfunction among all symmetric and asymmetric patterns, and (2) the 

worst case asymmetric response rate malfunction that results in delays during 

transitions from rich-to-lean or lean-to-rich sensor output. For wide range or universal 

sensors, the manufacturer also would be required to perform a test for two malfunction 

cases: (1) the single worst case response rate malfunction among all symmetric and 

asymmetric patterns, and (2) the symmetric response rate malfunction that results in 

delays during transitions from rich-to-lean and lean-to-rich sensor output. For the worst 

case malfunctions, staff would require manufacturers to submit data and/or analysis 

demonstrating that the malfunction will result in the worst case emissions compared to 

all the other response rate malfunctions. 

Lastly, staff is proposing changes to the HD OBD regulatory language to clarify 

demonstration testing for catalyst faults and other faults where default actions are taken 

subsequent to fault detection. Staff’s proposed modifications provide more direction to 

manufacturers to handle various scenarios of default actions and incremental levels of 

fault detection to ensure diesel monitors are appropriately tested. 

R. DEFICIENCIES 

The HD OBD regulation contains provisions that allow certification of HD OBD systems 

with “deficiencies” in cases where a good faith effort to fully comply with the OBD 

requirements has been demonstrated. The deficiency provisions facilitate OBD 

implementation by mitigating the danger of manufacturers not being able to certify 

engines with relatively minor implementation problems. 

Staff is proposing a clarification to the deficiency language in the HD OBD regulation. 

Specifically, staff currently does not issue deficiencies (and consequently, certification of 

the vehicle) for issues that would be subject to an ordered recall under the HD OBD 

enforcement regulation section 1971.5. Staff is proposing language to make this clear 

in the regulation. Further, staff is proposing language clarifying that OBD systems that 

fail to meet the requirements of the HD OBD regulation and that were not granted 

deficiencies for the requirements they failed to meet would be considered non-compliant 

and subject to enforcement under section 1971.5. 

Staff is also proposing amendments to the required timelines for issuing retroactive 

deficiencies in the HD OBD regulation. The regulation currently allows manufacturers to 

request retroactive deficiencies within either the first six months after commencement of 

the start of engine production or the first three months after commencement of the start 

of vehicle production, whichever is later. The deadlines are aligned with the required 

deadlines for production engine/vehicle testing to verify the monitoring requirements 

(section 1971.1(l)(2)), since such testing may uncover problems with the OBD system 

that would be considered deficiencies. Manufacturers have expressed concern about 

meeting the required deadlines for the testing, indicating that they have been having 

trouble procuring vehicles with their engines soon enough after production begins to 

complete the testing in time. Staff, therefore, is proposing to extend the deadline for 

production engine/vehicle testing, and thus the request deadline for retroactive 
46

deficiencies, to six months after commencement of the start of engine production or 

vehicle production, whichever is later. 

Additionally, staff is proposing amendments to address the certification of heavy-duty 

hybrid vehicles. The regulation currently allows manufacturers to carry over a 

deficiency up to a maximum of three model years from the time it was first issued, 

provided the manufacturer is able to demonstrate a good faith effort in complying with 

the HD OBD requirements, among other criteria. As indicated above, engine 

manufacturers and hybrid system manufacturers have expressed issues about meeting 

the OBD requirements on hybrid vehicles, citing the lack of experience in developing 

such OBD systems and the complexities of designing systems considering the various 

possible hybrid-engine configurations. And as already explained above in section II.A., 

staff is proposing to provide relaxation for the 2013 model year and require OBD 

compliance starting from the 2014 model year. However, for those hybrid vehicles that 

are certified to the HD OBD requirements of section 1971.1 in lieu of this relaxation in 

the 2013 model year and carried over to the 2014 model year, staff is proposing 

language to allow the 2014 model year to be considered the first model year for the 

deficiency. This change should ensure that a manufacturer who elects to certify to the 

more stringent path (HD OBD) in 2013 will not be at a disadvantage to manufacturers 

who choose the easier path for items that would take long lead time to resolve. 

Additionally, as already explained above in section II.A., staff is proposing an additional 

two free deficiencies for hybrid systems in the 2013 through 2015 model years to help 

avoid fines for manufacturers that fall short. 

Lastly, while staff is not proposing specific language in the regulations, staff would like 

to clarify the policy for the carry-over of deficiencies for emission threshold-based 

monitors to address questions raised by manufacturers. Specifically, in cases where 

there is an interim threshold (e.g, three times the standard) for a few years and then a 

step down to a final threshold (e.g., two times the standard), manufacturers have asked 

if a deficiency for the interim threshold ‘starts the clock’ towards the maximum two or 

three years of carry-over or if the carry-over clock restarts when the threshold steps 

down to the final threshold. Initially, staff was concerned that the latter case (i.e., 

restarting the clock with the final threshold) would allow manufacturers to drag their feet 

when addressing deficiencies or attempt to carry them over longer than needed. 

However, given the existing criteria that a manufacturer must meet to qualify for a 

deficiency, namely a good faith effort to comply in full and to come into compliance as 

expeditiously as possible, staff believes there are valid cases where it would be 

appropriate. For example, a manufacturer could make an appropriate attempt to 

comply with the interim threshold and fall short and again make a valid attempt to 

comply with the final threshold with a completely different approach or monitor and still 

come up short. In cases where it is not appropriate and is caused by a manufacturer 

not putting forth sufficient effort or resources to try and comply, the existing deficiency 

qualifications would already allow staff to deny such deficiencies and prevent further 

carry-over. Accordingly, staff believes it is appropriate that, as a general policy, a 

change in the monitoring threshold would reset the clock for a deficiency. As stated 

though, this would not, however, obviate the need to make a good faith effort to comply 
47

or to come into compliance as expeditiously as possible---both would still be required to 

qualify both initially and in each subsequent year for a deficiency to be granted. 

S. OTHER PROPOSED AMENDMENTS 

Staff is proposing other minor amendments to the HD OBD regulation. These include 

proposed additional items required to be submitted by the manufacturer as part of the 

HD OBD certification application and minor amendments to the production 

engine/vehicle evaluation testing procedures, as well as clarification changes 

throughout the regulation. All the proposed amendments are detailed in the attached 

regulatory language. 

Staff is also proposing amendments related to small volume manufacturers. As 

described above, staff is proposing amendments to the diesel misfire, NOx catalyst/NOx 

sensor, and PM filter monitoring requirements that include required phase-in schedules 

that manufacturers must meet. Small volume manufacturers, however, would likely 

have trouble meeting the required phase-ins, considering the small volume of engines 

(and thus, small number of engine families, if more than one) produced every year and 

the limited resources available to make the necessary changes each year of the phasein. In some cases, these manufacturers do not have enough different engine families to 

be able to meet a phase-in on a portion of their families and would be forced to 

implement the new requirements across their entire product line in the first year of the 

phase-in. Therefore, staff is proposing to allow small volume manufacturers to meet 

different schedules than the required phase-in schedules for these monitors. 

Specifically, for the diesel misfire monitor, staff is proposing to allow these 

manufacturers to either use an alternate phase-in schedule as defined in section (c) or 

to meet the requirement on all vehicles in the final year of the required phase-in 

schedule. For NOx catalyst/NOx sensor and PM filter monitoring, staff is proposing to 

allow these manufacturers to continue using the 2013 model year malfunction criteria 

for the 2014 and 2015 model years (i.e., exempt them from the phase-in malfunction 

criteria required for the 2014 and 2015 model year phase-in engines) and wait until the 

2016 model year to comply with the final thresholds that apply to 2016 and subsequent 

model year engines. These revisions for small volume manufacturers are consistent 

with what has historically been provided for light-duty vehicle manufacturers in the 

OBD II program. Further, staff is also proposing similar revisions in the OBD II 

regulation concerning small volume manufacturers and the new proposed PM filter 

monitor requirements and phase-in schedule. 

Concerning the OBD II regulation, staff is proposing amendments for medium-duty 

diesel vehicles certified to a chassis dynamometer tailpipe emission standard. The 

OBD II regulation currently requires manufacturers of these vehicles to request approval 

of the emission-based malfunction criteria in lieu of the engine dynamometer-based 

malfunction criteria (e.g., 2.0 times the applicable standards) required for each 

applicable diesel monitor in section 1968.2(f). At the time of the last amendments in 

2006, the vast majority of medium-duty diesels were certified using the engine 

dynamometer standards and chassis dynamometer-based certifications were extremely 
48

rare. However, since then, chassis dynamometer certification has become quite 

common and staff has developed more experience as to the monitoring capability of 

these systems with respect to emission levels relative to the emission standards. 

Therefore, staff is proposing that for most monitors on 2016 and subsequent model year 

medium-duty diesel vehicles certified to a chassis dynamometer tailpipe emission 

standard, manufacturers would be required to use the same chassis dynamometerbased malfunction criteria currently required for passenger cars, light-duty trucks, and 

medium-duty passenger vehicles certified to a chassis dynamometer tailpipe emission 

standard. For NMHC catalyst conversion efficiency monitoring, since the light-duty 

malfunction criteria does not have a NOx malfunction threshold while the medium-duty 

engine dynamometer-based criteria does, staff would require manufacturers to detect a 

catalyst fault before emissions exceed 1.75 times the applicable FTP NMHC or NOx 

standards. For diesel misfire monitoring, since the OBD II regulation currently requires 

light-duty emission threshold-based malfunction criteria and continuous monitoring while 

the medium-duty engine dynamometer-based criteria does not, staff would require 

manufacturers to detect a malfunction based on the medium-duty engine dynamometerbased malfunction criteria and monitoring requirements. The proposed language would 

eliminate the requirement for manufacturers to individually propose chassis-based 

thresholds and seek Executive Officer approval and instead would provide clear 

thresholds that all manufacturers would be required to meet. 

Lastly, as already stated above in section II.R., staff is proposing amendments to the 

required timelines for conducting production engine/vehicle testing to verify the 

monitoring requirements in the HD OBD regulation. The regulation currently allows 

manufacturers to conduct this testing and submit the results within either the first six 

months after commencement of the start of engine production or the first three months 

after commencement of the start of vehicle production, whichever is later. 

Manufacturers have expressed concern about meeting the required deadlines, 

indicating that they have been having trouble procuring vehicles with their engines early 

enough to complete the testing in time. Staff therefore is proposing to extend the 

deadline for production engine/vehicle testing to six months after commencement of the 

start of engine production or vehicle production, whichever is later. Additionally, for 

clarification, staff is proposing amendments to indicate the six month timeline starts 

when vehicle production using the manufacturer’s engine begins to cover cases where 

vehicle production begins earlier but solely with other engine options. 

T. HD OBD AND OBD II ENFORCMENT REGULATIONS 

The HD OBD and OBD II enforcement provisions (sections 1971.5 and 1968.5, 

respectively) help ensure the effectiveness of the HD OBD and OBD II regulations and 

to address OBD noncompliances in the field. The enforcement regulations detail 

procedures for evaluating and remediating (where necessary) OBD-specific in-use 

issues. Specifically, the regulations contain detailed protocols that provide clear 

direction as to the procurement, testing, sampling, and evaluation criteria that ARB staff 

uses to determine compliance with the OBD requirements. They include performance 

testing of emission threshold-related monitors, downloading of data of in-use monitoring 
49

performance ratios, and evaluation of other OBD requirements (e.g., diagnostic 

connector location, communication protocol standards, MIL illumination protocol, etc.). 

The results of the tests would be compared to the minimum performance levels 

prescribed in the enforcement regulations, which would determine if the 

engines/vehicles in question may be subject to remedial action or fines including 

mandatory recall for the most egregious nonconforming OBD systems. 

Currently, the HD OBD and OBD II enforcement regulations dictate specific criteria for 

procuring engines/vehicles for the test sample group used to perform the evaluation. To 

determine if a monitor is in compliance with the in-use monitoring performance 

requirements, the regulations require the test sample group to include engines/vehicles 

with denominators for that monitor meeting a minimum required value. Currently, many 

PM filter-related monitors and PM sensor monitors are required to have denominator 

values of at least 150 or 300, depending on the denominator incrementing criteria being 

used. Many of these monitors, however, require a PM filter regeneration event to occur, 

which consequently means the engine/vehicle would have to accumulate very high 

mileage to have a sufficient number of denominators to be acceptable as part of the test 

sample group. Given the recent trend in industry to further lengthen the intervals 

between regeneration events, this criterion will become even more restrictive in the 

future. Thus, staff is proposing to require engines/vehicles to be part of the test sample 

group if such PM filter-related monitors or PM sensor monitors have denominators of at 

least 50. 

As stated above, staff is proposing changes to the denominator incrementing criteria for 

the PM filter filtering performance monitor and PM filter missing substrate monitor in 

both the HD OBD and OBD II regulations. Specifically, these monitors, which are 

currently required to increment the denominator when, among other conditions, 800 

minutes of engine runtime are met in the HD OBD regulation and 500 miles are met in 

the OBD II regulation, would be required to increment the denominators using only the 

general denominator criteria starting in the 2016 model year. Further, the OBD II 

regulation would allow manufacturers to certify these monitors to a lower interim in-use 

ratio of 0.100 on 2016 through 2018 model year medium-duty vehicles. Considering the 

new denominator would increment more often than the current denominator, the 

resulting ratios would be less than the current ratios, causing manufacturers’ concerns 

about the ability to meet the required minimum in-use performance ratio. To address 

manufacturers’ concerns, staff is proposing to relax enforcement provisions for the first 

few years the monitors start using this new denominator, specifically to the 

nonconformance criteria and mandatory recall requirements. The OBD II enforcement 

regulation already has nonconformance criteria for monitors certified to an in-use ratio 

of 0.100 and do not subject these monitors to mandatory recall, so minimal changes are 

needed to address this. For the HD OBD enforcement regulation, staff is proposing 

changes to allow these monitors on 2016 through 2018 model year engines to use the 

less stringent criteria to determine nonconformance. Specifically, while other monitors 

on 2016 and subsequent model year engines would be considered nonconforming if the 

average in-use monitor performance ratio of engines in the test sample group is less 

than 0.088 or if at least 66 percent of the engines have an in-use ratio of less than 
50

0.100, the PM filter filtering performance monitor and PM filter missing substrate monitor 

would be considered nonconforming if the average in-use ratio is less than 0.050 or if at 

least 66 percent of the engines have an in-use ratio of less than 0.050. Further, staff is 

proposing that these monitors not be subject to mandatory recall for the 2016 through 

2018 model years. 

Staff is also proposing changes to the HD OBD and OBD II enforcement regulations to 

address the proposed changes made to the diesel misfire monitoring requirements. As 

described above, staff is proposing to require all 2016 and subsequent model year 

heavy-duty engines and medium-duty vehicles to detect a diesel misfire fault when the 

percentage of misfire exceeds 5 percent. The enforcement regulations currently do not 

contain mandatory recall criteria applicable to this new requirement. Thus, staff is 

proposing to require mandatory recall if the percentage of misfire exceeds 10 

percentage points greater than the malfunction criteria (i.e., 15 percent misfire) without 

the MIL being illuminated for both the HD OBD and OBD II enforcement regulations, 

starting with the 2019 model year. 

Lastly, staff is proposing changes to the HD OBD and OBD II enforcement regulations 

related to the PM filter. As described above in section II.J., staff is proposing higher 

interim emission malfunction thresholds for PM filter monitoring, with proposed 

thresholds around the range of 0.04 or 0.05 g/bhp-hr in the HD OBD regulation. 

Further, as previously stated, engine manufacturers have been moving towards higher 

engine-out NOx emission levels, resulting in lower engine-out PM levels that are near 

0.05 g/bhp-hr or lower. The HD OBD and OBD II enforcement regulations currently 

mandate a mandatory recall if a malfunction is not detected before emissions exceed 

two or three times the malfunction criteria. In the case of the PM filter monitor, that 

recall level could reach 0.120 to 0.150 g/bhp-hr. Considering that engine-out PM levels 

are projected to be around the 0.05 g/bhp-hr level for several manufacturers, an engine 

with no PM filter would have PM emission levels that would be far below the mandatory 

recall emission level and never be subject to mandatory recall despite a completely nonfunctional PM filter monitor. Considering how critical of an emission control component 

that the PM filter is, it would be inappropriate for the monitor to be unable to detect a 

completely missing PM filter and still not be subject to enforcement action. Thus, staff is 

proposing to add additional criteria for mandatory recall related to the PM filter monitor. 

Specifically, starting with the 2013 model year, a mandatory recall shall be ordered if the 

PM filter monitor is unable to detect any of the following: (1) a missing substrate PM 

filter fault or (2) a malfunction of the PM filter that causes PM emissions to be equal to 

or greater than the engine-out PM levels with the PM filter substrate completely 

removed. 

Staff is also proposing additional changes to the mandatory recall criteria for PM filter 

filtering performance monitoring in the OBD II enforcement regulation. The OBD II 

enforcement regulation currently mandates a mandatory recall if a malfunction is not 

detected before emissions exceed two times the malfunction criteria. The OBD II 

regulation currently requires manufacturers to detect a PM filter fault before emissions 

exceed 0.03 g/bhp-hr for all 2013 and subsequent model year vehicles. Some 
51

manufacturers, however, have indicated that their current monitors would not be able to 

detect a fault until emissions are quite near 0.06 g/bhp-hr, which would put them very 

close to the mandatory recall criterion, and have requested accommodations for their 

near-term model year vehicles. While staff does not think increasing the emission 

threshold malfunction criteria during these interim years would be appropriate as most 

manufacturers are on track to meet them, it acknowledges that some accommodation is 

needed with regards to enforcement to ensure that manufacturers are able to certify 

their OBD II systems. Thus, staff is proposing to exempt the PM filter filtering 

performance monitor from the mandatory recall provisions in the OBD II enforcement 

regulation that are specifically based on meeting the emission threshold malfunction 

criteria for the 2013 model year. 

III. ENVIRONMENTAL IMPACT ANALYSIS 

A. INTRODUCTION 

This chapter provides an environmental analysis for the proposed regulation. Based on 

ARB’s review, staff has determined that implementation of the proposed amendments to 

the HD OBD and OBD II regulations would not result in any potentially significant 

adverse impacts on the environment. This analysis provides the basis for reaching this 

conclusion. This section of the Staff Report also discusses the environmental benefits 

resulting from implementation of the proposed regulation. 

B. ENVIRONMENTAL REVIEW PROCESS 

ARB is the lead agency for the proposed regulation and has prepared this environmental 

analysis pursuant to its certified regulatory program that was certified by the Secretary of 

the Natural Resources Agency in 1978.1

 Public Resources Code §21080.5 of the 

California Environmental Quality Act (CEQA) allows public agencies with regulatory 

programs to prepare a plan or other written document in lieu of an environmental impact 

report or negative declaration once the Secretary of the Natural Resources Agency has 

certified the regulatory program. As required by ARB’s certified regulatory program, and 

the policy and substantive requirements of CEQA, ARB prepares an environmental 

analysis to assess the potential for significant long or short-term adverse environmental 

impacts associated with a proposed regulation.2

 In accordance with ARB’s regulations, 

the analysis also describes any beneficial environmental impacts.3

 The CEQA 

Guidelines environmental checklist was used to consider the potential for significant 

impacts.4 In accordance with ARB’s certified regulatory program, this environmental 

analysis is included in the Staff Report: Initial Statement of Reasons (ISOR) for the 

rulemaking.5

 

1

 CEQA Guidelines §15251(d); Cal. Code Regs., title 17, 60005-60008 

2

 Cal. Code Regs., title 17, section 60005(b) 

3

 Cal. Code Regs., title 17, 60005(d) 

4

 CEQA Guidelines, Appendix G 

5

 Cal. Code Regs., title 17, 60005 
52

If comments received during the public review period raise significant environmental 

issues, staff will summarize and respond to the comments in writing. The written 

responses will be included in the Final Statement of Reasons for the regulation. In 

accordance with ARB’s certified regulatory program, the decision maker will approve the 

written responses prior to taking final action on any proposal.6 If the regulation is 

adopted, a Notice of Decision will be posted on ARB’s website and filed with the 

Secretary of the Natural Resources Agency for public inspection.7

C. ENVIRONMENTAL IMPACTS 

Based on ARB’s review of the proposed regulation, staff concludes that the proposed 

regulatory amendments would not have a significant adverse effect on the environment. 

Compliance with the proposed regulation does not require or result in any physical 

change to the existing environment. It does not involve new development or require 

modifications to buildings or other structures, or affect operations at existing facilities, or 

cause any new land use designation because the action consists of changes to the 

engine/vehicle software that include changes to the OBD system algorithms using the 

existing hardware already on the engines/vehicles. These changes do not result in any 

physical changes to the environment such as adverse impacts to aesthetics, air quality, 

agricultural and forestry resources, biological resources, cultural resources, geology and 

soils, greenhouse gases, land use planning, mineral resources, population and housing, 

public services, recreation, or traffic and transportation. Further, compliance with the 

proposed regulation does not involve any activity that would involve or affect hazardous 

material, hydrology and water quality, noise, or population and housing because it does 

not require any action that could affect these resources. No discussion of alternatives 

or mitigation measures is necessary because no significant adverse environmental 

impacts were identified.

This determination was made because the proposed amendments would only affect HD 

OBD and OBD II requirements that have not yet been implemented. The proposed 

amendments affect requirements that start in the 2013 or later model year and do 

include some relaxations in the 2013 through 2015 model years that would allow higher 

interim malfunction emission thresholds for some monitors. 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. As described in section II of this staff report, these 

requirements are considered technically feasible for manufacturers to meet, but 

circumstances such as delays in technology development have prevented 

manufacturers from implementing the requirements within the required deadlines. For 

example, in the case of the PM filter monitoring requirement, the delay in the 

development of the PM sensor, which is expected to be used to meet the future 

stringent emission threshold requirement, has necessitated some delays in the start 

 

6

 Cal. Code Regs., title 17, 60007(a) 

7

 Cal. Code Regs., title 17, 60007(b) 
53

dates. Manufacturers are expected to take advantage of these delays to improve their 

system strategies and develop robust monitors to meet the requirements. 

Additionally, the proposed amendments would also establish more stringent 

requirements that will encourage manufacturers to design and build more robust 

engines to comply with the requirements. The proposed HD OBD and OBD II 

amendments will help ensure that forecasted emission reduction benefits from adopted 

light-, 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 proposed 

amendments are necessary to accomplish this goal by 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. 

Overall, the proposed amendments to the HD OBD and OBD II regulations would result 

in cleaner vehicles than those currently produced and are not expected to impact 

previously calculated emission benefits or findings. During the 2009 HD OBD 

regulatory process, the lifetime cumulative emission reductions for HD OBD, on a per 

engine basis calculated with the most recent version of EMFAC, were calculated to be 

165 pounds of ROG, 2000 pounds of NOx, and 14 pounds of PM. For OBD II, 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. These 

benefit calculations have not changed. 

 
54

IV. ENVIRONMENTAL JUSTICE 

State law defines environmental justice as the fair treatment of people of all races, 

cultures, and incomes with respect to the development, adoption, implementation, and 

enforcement of environmental laws, regulations, and policies (Senate Bill 115, Solis; 

Stats 1999, Ch. 690; Government Code § 65040.12(c)). The Board has established a 

framework for incorporating environmental justice into the ARB's programs consistent 

with the directives of State law. The policies developed apply to all communities in 

California, but recognize that environmental justice issues have been raised more in the 

context of low income and minority communities, which sometimes experience higher 

exposures to some pollutants as a result of the cumulative impacts of air pollution from 

multiple mobile, commercial, industrial, area-wide, and other sources. 

Over the past twenty years, ARB, local air districts, and federal air pollution control 

programs have made substantial progress towards improving the air quality in 

California. However, some communities continue to experience higher exposures than 

others as a result of the cumulative impacts of air pollution from multiple mobile and 

stationary sources and thus may suffer a disproportionate level of adverse health 

effects. 

Adoption and implementation of the OBD regulations will not result in any adverse 

environmental impacts on environmental justice communities. The proposed 

amendments would help ensure that measurable emission benefits are achieved both 

statewide and in the South Coast and San Joaquin Valley air basins 

V. ECONOMIC IMPACT 

The proposed amendments to the HD OBD and OBD II requirements and enforcement 

regulations would apply to manufacturers of California-certified medium-duty and heavyduty engines and manufacturers of medium and heavy-duty vehicles using the 

aforementioned engines. There are approximately 11 companies worldwide that 

manufacture diesel or gasoline California-certified heavy-duty engines, an estimated 10 

heavy-duty hybrid system manufacturers, and 9 heavy-duty alternate-fuel conversion 

manufacturers. Of these, only one manufacturer, an alternate fuel conversion 

manufacturer, is located in California. 

The proposed amendments to the HD OBD and OBD II regulations are not anticipated 

to have a significant impact on businesses or individuals related to the diesel and 

gasoline engine manufacturing industry. The proposed amendments primarily affect 

computer software, and additional lead time would be provided to manufacturers to 

allow them to implement such changes at the time they normally schedule system 

updates. The new reporting requirements will result in some additional costs to 

manufacturers, and the proposed amendments to require manufacturers to implement 

full OBD on alternate-fueled engines two years earlier than previously required will 

impose staffing and equipment costs two years earlier than previously anticipated, but 

will concomitantly provide emission benefits earlier than anticipated. These additional 
55

and earlier imposed costs will be passed on nationwide to consumers of heavy-duty 

vehicles since manufacturers normally certify one version of an engine for the entire 

nation. Additionally, staff believes that the proposed requirements would cause no 

noticeable adverse impact in California employment, business status, and 

competitiveness since all companies that manufacturer medium- and heavy-duty 

engines are required to meet the same requirements whether they are located in 

California or elsewhere. 

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 

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. COST AND COST EFFECTIVENESS 

The revisions to the OBD II and HD OBD regulations consist primarily of interim 

relaxation and clarification of existing requirements. The only changes that are 

expected to affect costs involve the increased reporting requirements for the misfire 

monitor and the two year earlier implementation schedule of full OBD for alternatefueled engines. To assess the impact these proposed changes will have on costs, ARB 

staff has performed a comprehensive cost analysis of the proposed amendments. 

Since the modifications to the two regulations are similar, and primarily affect diesel and 

alternate-fueled vehicles, staff concentrated its cost analysis on the HD OBD 

amendments since this provides the worst-case cost to manufacturers and consumers. 

This is because over 90 percent of all new vehicles in the heavy-duty sector consist of 

diesel and alternate-fueled engines while the light-duty and medium-duty sector 

consists primarily of gasoline-powered vehicles. The analysis was done to estimate the 

long-term “learned-out” costs of the program to a heavy-duty engine purchaser for a 

“typical” engine. The analysis estimated the incremental costs of implementing the 

proposed amendments. 

First, staff estimated the costs to manufacturers of heavy-duty diesel engines. These 

engines make up over 90 percent of all new heavy-duty engines and are manufactured 

only by large manufacturers. The amendments mainly provide short-term interim 

relaxed compliance for these manufacturers, with no associated compliance costs. 

However, there are additional costs associated with the reporting requirements that 

ensure compliance with the amendments for more comprehensive diesel misfire 

monitoring that begins with the 2016 model year. This will result in costs of up to 

$30,000 per manufacturer (for a large manufacturer) annually when the reporting 

requirements are fully phased in. These costs are expected to be passed on to 

consumers (new heavy-duty engine/vehicle purchasers) at an incremental retail cost of 

less than $0.56 per vehicle. For reference, this represents a less than 0.01 percent 
56

increase in the retail price of a typical heavy-duty engine. To perform the analysis, staff 

took the national sales numbers for the top nine engine manufacturers and determined 

a composite average value of 72,440 engines. This number was rounded to 72,000 in 

the analysis. Staff then estimated the incremental costs for an engine manufacturer 

with sales of 72,000 engines. Staff further assumed the engine manufacturer would 

have three engine families that would require separate misfire monitoring data to be 

generated and calculated the total costs for such a manufacturer. 

Second, staff estimated the costs to manufacturers of alternate-fueled engines. These 

engines currently make up approximately 2 percent of all new medium and heavy-duty 

engines but the percentage could increase in the future due to various monetary 

incentives that could be offered by state and federal organizations, greenhouse gas 

regulations, and by increased market demand. These engines are usually converted 

from diesel or gasoline to run on alternate-fuels such as CNG or LPG. As a result, 

these engines will already have an existing OBD system before being converted. It is 

projected that manufacturers will only need to recalibrate some of the existing monitors 

on these engines, and may, in some cases, need to develop a few new monitors for 

alternate fuel specific components that are added. Manufacturers of these vehicles 

range from small businesses (less than 250 employees) to large manufacturers. For 

the analysis, it was assumed that a typical alternate-fueled engine manufacturer will 

have one engine family with a large manufacturer producing about 5000 alternatefueled engines per year nationwide and a small manufacturer producing approximately 

500 engines per year nationwide. Additionally, it was assumed that a large alternatefueled manufacturer also produces diesel engines as its primary product. 

Since the amendments will require these manufacturers to comply with the alternatefuel requirements two years earlier than previously required, the majority of costs were 

already accounted for in the initial 2005 HD OBD rulemaking. The only additional costs 

would be those costs incurred during these first two years that would not otherwise have 

been incurred under the original requirements. Specifically, this would cover the hiring 

of additional staff or equipment needed for earlier compliance and possible two years of 

annual monitor recalibration. Also, since the alternate-fueled engines will have OBD 

systems on them two years earlier, buyers of such engines in these two years will see 

an incremental price increase that otherwise would not have occurred until later. From 

staff’s analysis, the incremental retail cost to buyers of these engines/vehicles for these 

two years has been estimated to range from $21 per vehicle to $207 per vehicle, 

depending on the size of the manufacturer (larger manufacturers can spread out the 

cost across more engines than smaller manufacturers). These costs represent less 

than a 1.0 percent increase in the retail cost of the smallest vehicles and far less than a 

0.1 percent increase for larger vehicles. Generally, large manufacturers and small 

businesses that convert alternate-fueled engines have not been direct competitors. 

Large manufacturers have mainly offered alternate-fueled engines for larger work 

vehicles such as line-haul trucks and buses while small businesses have typically 

offered alternate fuel conversions for smaller vehicles that perform lighter-duty work 

such as passenger and cargo vans. The incremental costs for these vehicles are also 

expected to be offset by financial incentives offered by state and federal governments 
57

that have recently ranged from about $7,500 up to $32,000. Future incentives are 

currently being proposed and may be different from these amounts. 

Based on the emission benefit analysis and the additional cost numbers identified 

above, the cost effectiveness of the OBD regulation was re-calculated to reflect the 

proposed amendments. 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. Since the 

amendments applicable to diesel engines only added an incremental cost of $0.56 per 

engine for diesel engines, newly calculated numbers for cost effectiveness, when 

rounded to the nearest cent, are identical to the results calculated in the 2009 biennial 

review. As stated in 2009, the per-engine cost to implement OBD is estimated at $630 

per engine. Splitting that in half, $315 was attributed to PM benefit for a costeffectiveness of $13.13 per pound of PM. The other half of the cost was attributed to 

ROG+NOx benefit for a cost-effectiveness of $0.08 per pound of ROG+NOx. Both 

values compare favorably with the cost-effectiveness of other recently adopted 

regulations. 

The amendments applicable to alternate-fueled engines requiring full HD OBD 

compliance in model year 2018, two years earlier than previously required, would also 

have a limited impact on cost-effectiveness. While there would be some incremental 

costs as calculated above that occur from implementing HD OBD two years earlier, 

there would also be an incremental emission benefit from the OBD system being 

required earlier. As such, the cost-effectiveness numbers calculated in 2009 for all 

engines including 2020 and subsequent model year alternate-fueled engines are also 

appropriate for 2018 and subsequent model year alternate-fueled engines under the 

proposed amendments. These numbers take into account both the costs to implement 

and the long-term emission benefits of the program (after the vehicles have been on the 

road for 20 years). Further, alternate-fueled engines make up a very small fraction of 

the vehicle fleet so the cost-effectiveness of the program, as a whole, is primarily driven 

by the cost-effectiveness of diesel engines. 

C. AFFECTED BUSINESSES AND POTENTIAL IMPACTS 

Any business involved in manufacturing, purchasing, or servicing 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. 

With respect to businesses that manufacture engines, there are approximately 11 

companies worldwide that manufacture diesel or gasoline California-certified heavy-duty 

engines. There are also an estimated 10 hybrid system manufacturers and 9 alternatefuel conversion manufacturers. Only one of these companies, an alternate-fuel 

conversion manufacturer, is located in California. Staff believes that some of the 

alternate-fuel conversion manufacturers are “small businesses” but cannot determine 

the exact number. However, the cost related to these manufacturers is determined to 

be negligible because these manufacturers are expected to pass the added costs on to 

consumers (engine and vehicle purchasers) in the form of increased retail prices. 
58

With respect to businesses that purchase medium- or heavy-duty diesel engines, the 

amendments are not expected to have any material impact as the incremental per 

engine price increase of $0.56 is insignificant on engines/vehicles that range in price 

from $20,000 to over $100,000. For businesses that purchase 2018 or 2019 model 

year heavy-duty alternate-fueled engines, the effect has also been determined to be 

negligible because the incremental per engine increase in price is less than 0.1 to 1.0 

percent and is expected to be more than offset by various financial incentives that exist 

for purchasing alternate-fueled vehicles. 

California accounts for only a small share of total nationwide medium-duty and heavyduty motor vehicle and parts manufacturing. As stated, only one alternate-fuel 

conversion company is located in California. 

D. 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. OBD systems are 

designed to detect malfunctions that may otherwise go undetected (and 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 detection, at an 

average cost of $741 per repair. This is a conservative cost estimate, since OBD 

systems 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 diesel engine or vehicle 

prices, since the calculated increase in retail price of an engine is estimated to be $0.56 

per engine. The two-year earlier implementation of full OBD on alternate-fueled 

engines is expected to increase the retail cost of the engine and vehicle for the two year 

time period by $21 to $207 but these costs are expected to be offset by various financial 

incentives offered by state and federal agencies that have ranged from $7,500 to 

$32,000 per vehicle in past years. 

For 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 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. 

E. POTENTIAL IMPACTS ON BUSINESS COMPETITIVENESS 
59

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 no material impact on retail prices of new engines and vehicles. 

Additionally, U.S. EPA has adopted federal OBD II and HD OBD requirements that are 

generally harmonized with those of ARB. To date, virtually all engine and vehicle 

manufacturers have chosen to design a single OBD system that meets both ARB and 

U.S. EPA regulations and equipped all vehicles nationwide with the same system. 

Therefore, any costs incurred by the engine or vehicle manufacturers will be applicable 

to all engines/vehicles nationwide and these costs will be passed on to purchasers 

nationwide in the form of higher retail prices as explained above. Thus, any price 

increases of 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. 

It should be noted that one area of difference between the Federal and California 

requirements involves heavy-duty hybrids. Specifically, the U.S. EPA has exempted 

hybrids from OBD compliance for the 2014 through 2016 model years while ARB will 

require compliance. In theory, this could lead to some heavy-duty hybrid vehicles being 

more expensive in California than in other states during these three years. However, 

staff’s assessment is that this is not likely to happen for two reasons. First, the heavyduty hybrid vehicle sales volume is extremely low, which would make it virtually 

impractical for manufacturers to have sufficient resources to offer two different OBD 

systems (one that complies for the California market and one that does not comply with 

California hybrid monitoring requirements that would be available for sale in other 

states). Past history would suggest that these manufacturers will design and build one 

system nationwide and as such, the cost to purchasers would be the same nationwide. 

Second, the ARB’s HVIP program already incentivizes (and largely subsidizes) the 

purchase of a heavy-duty hybrid vehicle for businesses in California and those 

incentives (typically $20,000 to $40,000 per vehicle) dwarf any increase in cost due to 

OBD compliance. Thus, even if there were to be an increase specific to hybrids offered 

for sale in California, the incentives would more than offset them for any purchaser in 

California. 

F. 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. 

G. POTENTIAL IMPACT ON BUSINESS CREATION, ELIMINATION, OR 

EXPANSION 

The proposed amendments are not expected to affect business creation, elimination or 

expansion. 
60

VI. ANALYSIS OF ALTERNATIVES 

As described in the individual sections above detailing the proposed changes, 

manufacturers suggested alternatives to the proposed amendments, and staff explained 

why these alternatives were not considered. No alternative considered by the agency 

would be more effective in carrying out the purpose for which the regulation is proposed 

or would be as effective or less burdensome to affected private persons than the 

proposed regulation. 

VII. SUMMARY AND RATIONALE FOR PROPOSED AMENDMENTS 

In response to manufacturers’ concerns about difficulties meeting the requirements 

within the required timeframes, the proposed amendments mostly include relaxations 

that would provide manufacturers with more lead time. Manufacturers are expected to 

take advantage of these delays to improve their system strategies and develop robust 

monitors to meet the requirements and ensure more robust systems. The proposed 

amendments also include more stringent requirements that will encourage 

manufacturers to design and build more robust engines to comply with the 

requirements. In general, the proposed amendments to the HD OBD and OBD II 

regulations would help ensure that forecasted emission reduction benefits from adopted 

medium-duty and heavy-duty engine emission standards programs are achieved. 

Proposed amendments to Cal. Code Regs., title 13, section 1971.1: 

Subsection (a) The “Purpose” clause of the regulation has been amended to 

reaffirm and clarify the objectives of the regulation consistent with the longstanding 

expressed intent when the regulation was first adopted and subsequently amended. 

Subsection (c) “Alternate-fueled engine” This new proposed definition is needed 

to clear up confusion about what constitutes an alternate-fueled engine and thus is 

exempt from meeting the HD OBD monitoring requirements until the 2018 model year, 

with the clarification mostly involving engines that utilize more than one type of fuel. 

Subsection (c) “Alternate phase-in” This new proposed definition is needed to 

allow manufacturers some flexibility and allow more time in meeting some requirements 

with phase-in schedules. 

Subsection (c) “Auxiliary Emission Control Device (AECD)” The proposed 

change to move this definition before the definition of “base fuel schedule” is needed 

since the definitions in subsection (c) are typically listed in alphabetical order. 

Subsection (c) “Calculated load value” The proposed changes to the definition 

of “calculated load value” is necessary to update the versions of the SAE J1979 and 

SAE J1939 documents referenced to the most recent versions referenced in section 

1971.1(h)(1) of the regulation. 
61

Subsection (c) “Diagnostic or emission critical” The proposed changes to the 

definition of a “diagnostic or emission critical” electronic control unit is necessary to limit 

the number of control units that would be subject to report the CAL ID/CVN parameters 

to the most important control units. 

Subsection (c) “Driving cycle” The proposed change to this definition is needed 

for formatting reasons. 

Subsection (c) “Emission standard” The addition of this definition is needed to 

clarify that the OBD regulations include emission standards. The definition revises the 

definition set forth at Health and Safety Code section 39028 consistent with the express 

authorization of the Board to make such a revision in Health and Safety Code sections 

39010 and 39601. 

Subsection (c) “Evaporative emission standards” The new proposed definition is 

needed to identify a subcategory of the new definition of emission standard that had 

previously been identified merely as an emission standard. 

Subsection (c) “Exhaust emission standards” or “tailpipe emission standards” 

The new proposed definition is needed to identify a subcategory of the new definition of 

emission standard that had previously been identified merely as an emission standard. 

 . 

Subsection (c) “Fueled engine operation” This new proposed definition is needed 

to complement the amendments to the in-use monitor performance requirements, where 

this definition is used. 

Subsection (c) “Gasoline engine” This proposed change to delete “or an 

alternate-fueled engine” from this definition is needed because a separate new 

definition for “alternate-fueled engine” is being proposed. 

Subsection (c) “Hybrid vehicle” This new proposed definition is needed to 

complement the amendments to the permanent fault code erasure requirements and 

the in-use monitor performance requirements, where this definition is used. 

Subsection (c) “Ignition cycle” The proposed changes to the definition are 

necessary to account for the proposed changes to the ignition cycle counter 

requirements for hybrid vehicles in section 1971.1(d)(5.5). 

Subsection (c) “Malfunction” The proposed addition of “system” to the 

definition of “malfunction” is needed since the regulation requires detection of a 

malfunction that can affect either a component or a system. 

Subsection (c) “Permanent fault code” The proposed deletion of the phrase 

“currently commanding the MIL on” is needed to avoid confusion, since a permanent 
62

fault code may not be commanding the MIL on in cases where the fault information in 

the on-board computer has been cleared by a scan tool or a battery disconnect. 

Subsection (c) “Propulsion system active” This new proposed definition is needed 

to complement the amendments to the permanent fault code erasure requirements and 

the in-use monitor performance requirements, where this definition is used. 

Subsection (c) “Small volume manufacturer” This new proposed definition is 

needed to complement the proposed changes to the exceptions to monitoring 

requirements provisions in subsection (g)(5.8.2). 

Subsection (c) “Warm-up cycle” The proposed addition of the phrase “a driving 

cycle with” to this definition is necessary to clarify that a warm-up cycle is referring to a 

driving cycle with specific conditions met. Additionally, the proposed change to allow 

manufacturers to use an alternate definition for warm-up cycle is needed to account for 

vehicles that are unable to warm up the engine coolant temperature to the defined 

temperatures in the current definition even if it has been sufficiently driven. 

Subsection (d)(2.1.2) The purpose of this subsection is to indicate how the 

functional check of the MIL should work. The proposed change to delete “20” is 

necessary since the original phrase “minimum of 15-20 seconds” already indicates 15 

seconds as the minimum required time. 

Subsection (d)(2.1.3) The purpose of this section is to allow manufacturers the 

option to use the MIL for readiness status indication. The proposed change is needed 

for formatting reasons, with the old text in subsection (h)(4.1.3) now in subsection 

(h)(4.1.6). 

Subsections (d)(2.2.1)(D) The purpose of this subsection is to indicate the 

criteria under which freeze frame conditions can be stored and erased for engines using 

ISO 15765-4. The proposed changes are needed to address concerns about 

manufacturers inappropriately erasing freeze frame data when a pending fault code 

matures to a confirmed fault code. Also, the proposed changes to require monitors 

using alternate strategies to store and erase the freeze frame conditions concurrent with 

storing and erasing a confirmed fault code are needed since the current language is 

vague about how to handle one-trip monitors which don’t store pending fault codes. 

Subsection (d)(2.2.2)(D) The purpose of this subsection is to indicate the 

criteria under which freeze frame conditions can be stored and erased for engines using 

SAE J1939. The proposed changes to require monitors using alternate strategies to 

store and erase the freeze frame conditions with the MIL-on fault code are needed since 

the current language is vague about how to handle one-trip monitors, which don’t store 

pending fault codes. 

Subsection (d)(2.3.1)(A) The purpose of this subsection is to indicate the 

protocol for extinguishing the MIL for engines using ISO 15765-4. The proposed 
63

changes are needed to include reference to diesel monitors that have their own protocol 

for extinguishing the MIL in lieu of the requirements in this subsection, since the current 

language only referenced gasoline monitors. The proposed changes are also needed 

to clarify that the MIL is not allowed to be extinguished after less than three sequential 

driving cycles, since the original language may be misinterpreted. 

Subsections (d)(2.3.1)(B) and (d)(2.3.2)(C) The purpose of these subsections is to 

indicate the protocol for erasing confirmed fault codes or previously MIL-on fault codes. 

The proposed changes to require rather than allow manufacturers to erase these fault 

codes after 40 warm-up cycles are necessary to ensure consistency among 

manufacturers and require all of them to erase the fault codes in the same timing. The 

proposed change to delete “engine” from “engine warm-up cycle” is also necessary to 

be consistent with the terminology used in the definitions in section (c), which states 

“warm-up cycle.” 

Subsections (d)(2.3.1)(C)(ii)b.3. and (d)(2.3.2)(D)(ii)b.3 The purpose of these 

subsections is to indicate the criteria under which a permanent fault code can be erased 

when the fault information in the on-board computer has been cleared and the OBD 

system is not commanding the malfunction indicator light on. The proposed changes to 

subsections (d)(2.3.1)(C)(ii)b.3.i. and (d)(2.3.2)(D)(ii)b.3.i. and the proposed additions of 

subsections (d)(2.3.1)(C)(ii)b.3.v. and (d)(2.3.2)(D)(ii)b.3.v. are needed to account for 

hybrid vehicles, which may not start the engine right after the vehicle is turned on and 

may affect the “cumulative time since engine start” criterion. 

Subsection (d)(2.3.2)(A) The purpose of this subsection is to indicate the 

protocol for extinguishing the MIL for engines using SAE J1939. The proposed changes 

are needed to clarify that the MIL is not allowed to be extinguished after less than three 

sequential driving cycles, since the original language may be misinterpreted. 

Subsection (d)(2.4.1) The purpose of this subsection is to describe default 

strategies that manufacturers are allowed to have and not be required to illuminate the 

MIL when they are invoked. The proposed changes are needed for readability to make 

the language and criteria easier to understand. 

Subsection (d)(4.3.2)(B) The purpose of this subsection is to describe the 

specifications for incrementing the denominator. The proposed clarification that the 

requirements in subsections (d)(4.3.2)(F), (I), and (J) may supersede the requirements 

in subsection (d)(4.3.2)(B) for specific monitors/vehicles is needed since they have 

certain characteristics that make the current requirements in subsection (d)(4.3.2)(B) 

inappropriate to use. The proposed change to add “engine” to “start” to subsection 

(d)(4.3.2)(B)(i) is also necessary to be consistent with the terminology used in the 

definitions in section (c), which states “engine start”. 

Subsection (d)(4.3.2)(C) The purpose of this subsection is to describe the 

specifications for incrementing the denominator for evaporative system monitors. The 

proposed change is needed to allow other monitors (i.e., engine cooling system input 
64

component monitors, comprehensive component input component temperature sensor 

rationality monitors) that also require a cold start to enable monitoring to use the same 

denominator. Further, the proposed change to add “engine” to “start” in subsection 

(d)(4.3.2)(C)(i) is necessary to be consistent with the terminology used in the definitions 

in section (c), which states “engine start”. 

Subsection (d)(4.3.2)(E) The purpose of this subsection is to describe the 

specifications for incrementing the denominator for components that are “commanded” 

to function. The proposed change to delete “output” from “output components” is 

needed since some of the component monitors listed under this section are not output 

components. The proposed additions of the PM filter active/intrusive injection monitor 

and the PM sensor heater monitor to this section are needed since the previously 

required denominator incrementing criteria applied to these monitors were not 

appropriate. Additionally, the proposed change to allow 2010 through 2015 model year 

engines to use the previously required denominator criteria is needed to allow lead time 

for manufacturers to meet the new requirement. 

Subsection (d)(4.3.2)(F) The purpose of this subsection is to describe the 

specifications for incrementing the denominator for monitors that require “alternate” 

criteria. The proposed change to modify the phrase “monitors of the following 

components” to “the following component monitors” is needed since the items listed in 

this section refer to monitors, not components. The proposed deletions of “engine 

cooling system input component” and “comprehensive component input component 

temperature sensor rationality monitors” and renumbering of the section are needed 

since these monitors were moved to subsection (d)(4.3.2)(C). The proposed change to 

add “PM sensor monitoring capability monitor” to this subsection is needed to reflect the 

current capability of the PM sensor technology, which may regenerate infrequently inuse and thus may result in low ratios for this monitor with the currently required 

denominator. 

Subsection (d)(4.3.2)(G) The purpose of this subsection is to describe the 

specifications for incrementing the denominator for components or emission controls 

that experience infrequent regeneration events. The proposed change to modify the 

phrase “monitors of the following components” to “the following component monitors” is 

needed since the items listed in this section refer to monitors, not components. The 

proposed change to limit application of this requirement to the 2010 through 2015 model 

year for the PM filter filtering performance monitors and the PM filter missing substrate 

monitors to is needed considering the importance of the PM filter, which controls 

emissions throughout the driving cycle, not just once every 800 minutes. 

Subsection (d)(4.3.2)(H) The purpose of this subsection is to describe the 

specifications for incrementing the denominator for some monitors based on whether or 

not a regeneration event occurs. The proposed deletion of “PM filter active/intrusive 

injection” is needed since this monitor was moved to subsection (d)(4.3.2)(E). 
65

Subsection (d)(4.3.2)(I) The purpose of this subsection is to allow certain 

vehicles to increment the general denominator based on alternate criteria in lieu of 

those in subsection (d)(4.3.2)(B). The proposed deletion of the phrase “hybrid vehicles” 

is necessary since a new proposed requirement for hybrid vehicles has been added 

(subsection (d)(4.3.2)(J)) that will supersede this requirement. The proposed 

replacement of the phrase “integrated starter and generators” with the phrase “a vehicle 

with a start-stop system that does not meet the definition of a hybrid vehicle as defined 

in section (c)” is needed since the requirement in subsection (d)(4.3.2)(I) no longer 

applies to hybrid vehicles (a separate section was created specifically for hybrids) and 

vehicles with integrated starters and generators most commonly will meet the definition 

of a hybrid vehicle while vehicles with other simpler start-stop systems will not and will 

still be subject to the requirements of this section. The proposed change of “alternate 

fuel vehicles” to “alternate-fueled engines” is needed to be consistent with the phrase 

used in the definitions in subsection (c). The proposed deletion of “(e.g., dedicated, bifuel, or dual-fuel applications)” is needed since the phrase “alternate-fueled engine” is 

now defined in section (c), so the examples here are not needed anymore. 

Subsection (d)(4.3.2)(J) The purpose of this new proposed subsection is to 

indicate the criteria under which the general denominator shall increment for hybrid 

vehicles. This new requirement is needed to account for the fact that hybrid vehicles 

need a new definition to recognize trips where the engine starts later in the trip. 

Additionally, the proposed language to allow 2010 through 2015 model year engines to 

use the previously required denominator criteria in subsection (d)(4.3.2)(I) is needed to 

allow lead time for manufacturers to meet the new requirement. 

Subsection (d)(4.5.3) The purpose of this subsection is to describe the conditions 

under which incrementing of all numerators and denominators are allowed to be 

disabled. The proposed deletions of reference to subsection (d)(4.3.2)(C) and the 

phrase “engine cold start” are needed since subsection (d)(4.3.2)(C) refers to the 

denominator incrementing criteria for monitors that require cold start (e.g., evaporative 

system monitors), so all other monitors that do not require a cold start can and should 

still accurately increment their numerators and denominators even if an “engine cold 

start” can no longer be determined. 

Subsection (d)(5.1.1) The purpose of this subsection is to indicate the specific 

diesel components/monitors the HD OBD system is required to report in-use monitor 

performance data for. The proposed changes to this subsection are needed to be 

consistent with what is required to be reported in SAE 1979 and SAE J1939. 

Subsection (d)(5.5.2)(B) The purpose of this subsection is to indicate the 

criteria under which the ignition cycle counter shall increment. The proposed changes 

are needed to ensure that the counters for conventional vehicles and hybrid vehicles 

are incremented in an equivalent manner. 

Subsection (d)(7.5) The purpose of this subsection is to indicate the HD OBD 

implementation schedule for alternate-fueled engines. The proposed change of the 
66

start date to implement HD OBD systems from 2020 to 2018 is needed to address the 

issue that alternate-fueled engines will comprise a higher percentage of the heavy-duty 

market than previously thought, thus increasing the importance of making sure the 

emission controls on these engines are properly working in-use. The proposed 

additional language in subsection (d)(7.5.3) requiring manufacturers to propose a 

monitoring plan for alternate-fueled engines is needed to ensure that all emission 

control components (which may include both diesel-related and gasoline-related 

components) on the engine are properly monitored. 

Subsection (d)(7.6) This new proposed subsection allowing 2013 model year 

heavy-duty hybrid vehicles to meet less stringent requirements in lieu of the 

requirements in section 1971.1 is needed to address manufacturers’ concerns about 

implementing compliant HD OBD systems and to allow some interim relaxation from 

meeting the HD OBD requirements. 

Subsection (e)(1.1) The purpose of this subsection is to indicate the general 

requirement for diesel fuel system monitoring. The proposed change of “emission 

standard” to “applicable standard” is needed since “applicable standard” is the more 

appropriate term to use. 

Subsection (e)(1.4.2) The purpose of this subsection is to describe the MIL 

illumination and fault code storage protocol for diesel fuel system monitoring. The 

proposed change of “vehicle” to “engine” is needed since the reference to “engine” is 

more appropriate. 

Subsection (e)(2.1.1) The purpose of this subsection is to indicate the general 

requirement for diesel misfire monitoring. The proposed deletion of “causing excess 

emissions” from “misfire causing excess emissions” is needed since the proposed 

changes to the diesel misfire monitoring now involve requiring detection of faults when 

the percentage of misfire exceeds a certain level, not when a specific emission 

threshold is exceeded. 

Subsection (e)(2.2) The purpose of this subsection is to require manufacturers to 

monitor for misfire on diesel engines. The proposed change to require all diesel 

engines to meet subsection (e)(2.2.2) with a phase-in starting in the 2016 model year is 

needed since the current requirement to monitor for misfire only at idle will not detect 

misfire faults that occur only during other engine speed and load conditions. The 

proposed change to require misfire detection when the percentage of misfire exceeds 5 

percent instead of when specific emission thresholds are exceeded in subsection 

(e)(2.2.2) is needed to address manufacturers’ concerns about difficulties in establishing 

a level of misfire that equates to a specific tailpipe emission threshold. The proposed 

change to subsection (e)(2.2.3) is needed for formatting reasons, since the malfunction 

criteria originally in subsection (e)(2.2.2)(A) is now in subsection (e)(2.2.2). The 

proposed new subsection (e)(2.2.5) to allow manufacturers to detect misfire at a higher 

percentage than the required 5 percent if specific emission levels are not exceeded is 
67

needed to provide relaxation to manufacturers should their system be abnormally robust 

to an emission increase due to misfire. 

Subsection (e)(2.3.1) The purpose of this subsection is to describe the conditions 

under which diesel misfire monitoring shall occur. The proposed changes are needed 

to avoid confusion by indicating that the monitoring conditions under this subsection 

apply to misfires identified in section (e)(2.2.1). 

Subsection (e)(2.3.3) The purpose of this subsection is to describe the conditions 

under which diesel misfire monitoring shall occur. The proposed change to require 

monitors for misfires identified in section (e)(2.2.2) to meet subsection (e)(2.3.3) is 

needed for clarity. The proposed changes to the required monitoring conditions in 

subsection (e)(2.3.3)(A)(i) are needed to address manufacturers’ concerns about the 

extent to which they can monitor for misfire on diesel engines given the wide range of 

heavy-duty applications that exist up to the 2018 model year, while the proposed 

requirement to continuously monitor for misfire under all positive torque engine speed 

and load conditions with a phase-in starting in the 2019 model year in subsection 

(e)(2.3.3)(A)(ii) are needed to ensure misfires that occur during the higher operating 

ranges are robustly detected. Lastly, the proposed change in subsection (e)(2.3.3)(B) is 

needed to allow manufacturers to disable misfire monitoring under conditions in which 

robust detection of misfires is at issue. 

Subsection (e)(2.4.2) The purpose of this subsection is to describe the MIL 

illumination and fault code storage protocol for the diesel misfire monitor. The proposed 

change to require monitors for misfires identified in section (e)(2.2.2) to meet subsection 

(e)(2.4.2) is for clarity. The proposed change to delete “(A)” from “section (e)(2.2.2)(A)” 

in subsection (e)(2.4.2)(A) is needed for formatting reasons, since the malfunction 

criteria originally in subsection (e)(2.2.2)(A) is now in subsection (e)(2.2.2). 

Subsection (e)(3.2.6) The purpose of this subsection is to require manufacturers to 

monitor the EGR catalyst. The proposed addition of subsection (e)(3.2.6)(B), which 

allows manufacturers to be exempt from monitoring the EGR catalyst if a failure of the 

catalyst does not cause a measurable emission impact, is needed to provide relaxation 

to manufacturers due to their concerns that a failure of this catalyst does not directly 

cause an emissions increase. 

Subsection (e)(5.2.3)(B) The purpose of this subsection is to require 

manufacturers to monitor the NMHC converting catalyst for proper feedgas generation. 

The proposed delay of the required start date to the 2015 model year is needed to allow 

manufacturers more time to meet the requirement. The proposed language allowing 

manufacturers to be exempt from this monitoring requirement if certain conditions are 

met is needed to allow manufacturers relaxation in meeting this requirement based on 

their concerns. 

Subsections (e)(5.2.2)(B), (e)(6.2.1)(A)(i), (e)(6.2.1)(D)(i), (e)(6.2.2)(A)(i) and (iv), 

(e)(7.2.1)(A) and(B), (e)(8.2.1)(A) and (B), (e)(8.2.1)(D), (e)(8.2.2)(B), (e)(9.2.1)(B)(i), 
68

(e)(9.2.2)(A)(i) and (iv), (g)(3.4.3), and (j)(1.1) The proposed change of “emission 

standard” to “exhaust emission standard” is needed since “exhaust emission standard” 

is the more appropriate term to use. 

Subsection (e)(5.2.3)(D) The proposed changes to this subsection are needed 

for readability. 

Subsection (e)(6.2.1) The purpose of this subsection is to require manufacturers to 

monitor the NOx converting catalyst conversion efficiency. The proposed changes to 

allow higher interim emission thresholds for 2013 through 2015 model year engines in 

new proposed subsections (e)(6.2.1)(B) and (C) and to delay the final, stringent 

emission thresholds to 2016 in subsection (e)(6.2.1)(D) are needed to address 

manufacturers’ concerns about meeting the requirements and to allow manufacturers 

more time to meet the final thresholds. The new proposed subsection (e)(6.2.1)(E), 

which allows engines first certified in the 2014 or 2015 model year and carried over to 

the 2016 model year to meet the previous interim thresholds in 2016, is needed so that 

manufacturers would not have to spend resources to have all engines meet the final 

thresholds in 2016. 

Subsection (e)(6.2.2) The purpose of this subsection is to require manufacturers to 

monitor the SCR catalyst reductant delivery performance. The proposed changes to 

allow higher interim emission thresholds for 2013 through 2015 model year engines in 

new proposed subsections (e)(6.2.2)(A)(ii) through (iii) and to delay the final, stringent 

emission thresholds to 2016 in subsection (e)(6.2.2)(A)(iv) are needed to address 

manufacturers’ concerns about meeting the requirements and to allow manufacturers 

more time to meet the final thresholds. The new proposed subsection (e)(6.2.2)(A)(v), 

which allows engines first certified in the 2014 or 2015 model year and carried over to 

the 2016 model year to meet the previous interim thresholds in 2016, is needed so that 

manufacturers would not have to spend resources to have all engines meet the final 

thresholds in 2016. 

Subsection (e)(6.2.2)(D) The purpose of this subsection is to require 

manufacturers to monitor the SCR catalyst feedback control. The proposed addition of 

“(e.g., pressure control)” is needed to give an example of a feedback control strategy 

that is required to be monitored. 

Subsection (e)(6.3) The purpose of this subsection is to describe the conditions 

under which NOx converting catalyst monitoring shall occur. The proposed addition of 

section (e)(6.2.2)(A) (for reductant delivery performance monitoring) to subsection 

(e)(6.3.1), which requires monitoring to occur once per trip, is needed since the original 

requirement for monitoring to occur continuously was found to be inappropriate and too 

stringent. The proposed deletion of section (e)(6.2.2)(A) (for SCR performance 

monitoring) from subsection (e)(6.3.2) is needed since this subsection was moved to 

subsection (e)(6.3.1) as previously described. 
69

Subsection (e)(8.2.1) The purpose of this subsection is to require manufacturers to 

monitor the PM filter filtering performance. The proposed changes to allow higher 

interim emission thresholds for 2013 through 2015 model year engines in subsections 

(e)(8.2.1)(B) and (C) are needed to address manufacturers’ concerns about meeting the 

requirements, given the delay of the availability of PM sensors, and to allow 

manufacturers more time to meet the final thresholds. The new proposed subsection 

(e)(8.2.1)(E), which allows engines first certified in the 2014 or 2015 model year and 

carried over to the 2016 model year to meet the previous interim thresholds in 2016, is 

needed so that manufacturers would not have to spend resources to have all engines 

meet the final thresholds in 2016. The new proposed subsection (e)(8.2.1)(F) is needed 

to prohibit manufacturers from using an alternate phase-in schedule instead of the 

required phase-in schedule proposed in subsection (e)(8.2.1)(C). 

Subsection (e)(8.2.4) The purpose of this subsection is to require manufacturers to 

monitor the catalyzed PM filter. The proposed delay of the required start date to the 

2015 model year in subsection (e)(8.2.4)(A) for monitoring NMHC conversion capability 

is needed to allow manufacturers more time to meet the requirement. The proposed 

language in subsection (e)(8.4.2)(A)(iii) allowing manufacturers to be exempt from this 

monitoring requirement if certain conditions are met is needed to allow manufacturers 

relaxation in meeting this requirement based on their concerns. The proposed addition 

of subsection (e)(8.2.4)(B), which requires monitoring of catalyzed PM filter for proper 

feedgas generation, is needed to ensure monitoring of all components that generate 

feedgas for the SCR system. 

Subsection (e)(8.3.2) The proposed deletion of “II” from “OBD II system” is needed 

to correct an error, since this regulation does not apply to OBD II systems. 

Subsection (e)(9.2.2)(A) The purpose of this subsection is to require 

manufacturers to monitor the NOx sensor for sensor performance faults. The proposed 

changes to allow higher interim emission thresholds for 2013 through 2015 model year 

engines in new proposed subsections (e)(9.2.2)(A)(ii) through (iii) and to delay the final, 

stringent emission thresholds to 2016 in subsection (e)(9.2.2)(A)(iv) are needed to 

address manufacturers’ concerns about meeting the requirements and to allow 

manufacturers more time to meet the final thresholds. The new proposed subsection 

(e)(9.2.2)(A)(v), which allows engines first certified in the 2014 or 2015 model year and 

carried over to the 2016 model year to meet the previous interim thresholds in 2016, is 

needed so that manufacturers would not have to spend resources to have all engines 

meet the final thresholds in 2016. Lastly, the proposed addition of an NMHC threshold 

in subsection (e)(9.2.2)(A)(iv) is necessary to maintain consistency with the thresholds 

for the heavy-duty NOx converting catalyst monitors as well as the medium-duty NOx 

sensor monitoring requirements in the OBD II regulation. 

Subsection (e)(9.3.1) The purpose of this subsection is to indicate the conditions 

under which NOx sensor monitoring shall occur. The proposed addition of section 

(e)(9.2.2)(D), for sensor monitoring capability monitors, to subsection (e)(9.3.1)(A) is 

needed since this monitor has been determined to be important based on reviews of 
70

manufacturers’ OBD systems, so there should be assurance that the in-use monitoring 

performance data of this monitor is tracked and reported starting in the 2016 model 

year. The proposed deletion of section (e)(9.2.2)(D) from subsection (e)(9.3.1)(B) is 

needed since this subsection was moved to subsection (e)(9.3.1)(A) as previously 

described. The proposed change to delete the requirement for monitoring to occur 

“every time the monitoring conditions are met during the driving cycle in lieu of once per 

driving cycle” in subsection (e)(9.3.1)(B) is needed since staff does not see a need for 

this, and because some monitors currently required to meet this requirement would not 

be able to meet this if they were intrusive monitors. 

Subsection (e)(9.4) The purpose of this subsection is to describe the MIL 

illumination and fault code storage requirements for exhaust gas sensors. The 

proposed addition of language to separately detect and store different fault codes for 

circuit and out-of-range faults is needed for emphasis since some manufacturers have 

been inappropriately storing the same fault code for different circuit and out-of-range 

faults, even though section (h)(4.4) currently requires manufacturers to pinpoint the 

likely cause of a malfunction. 

Subsection (e)(11.1) The purpose of this subsection is to require manufacturers to 

monitor the cold start emission reduction strategy on diesel engines. The proposed 

changes to subsection (e)(11.1.1) are needed for readability. The new proposed 

subsection (11.1.2), which would require manufacturers to use different diagnostics to 

distinguish component/element faults that occur while the cold start strategy is active 

from faults that occur while the strategy is not active (e.g., warmed-up conditions), is 

needed to avoid confusion and prevent manufacturers from using only one fault 

code/monitor to detect both types of faults – this new subsection would prevent 

premature erase of pending fault codes. 

Subsection (f)(1.1) The purpose of this subsection is to indicate the general 

requirement for gasoline fuel system monitoring. The proposed change of “emission 

standard” to “applicable standard” is needed since “applicable standard” is the more 

appropriate term to use. 

Subsection (f)(1.2.1) The purpose of this subsection is to describe the malfunction 

criteria for gasoline fuel system monitoring. The proposed changes of “vehicle” to 

“engine” in subsections (f)(1.2.1)(B) and (C) are needed since the reference to “engine” 

is more appropriate. 

Subsection (f)(2.3.1) The purpose of this subsection is to describe the conditions 

under which gasoline misfire monitoring shall occur. The proposed clarification that the 

requirements in subsection (f)(2.3.6) may supersede the requirements in subsection 

(f)(2.3.1)(A) is needed since subsection (f)(2.3.6) contains criteria for vehicles that utilize 

engine shutoff strategies like hybrids, which have certain characteristics that make the 

current requirements in subsection (f)(2.3.1)(A) inappropriate to use. 
71

Subsection (f)(2.3.6) The purpose of this subsection is to indicate the conditions 

under which misfire monitoring shall occur for vehicles that employ engine shut-off 

strategies that do not require the vehicle operator to restart the engine to continue 

driving. The proposed changes to this subsection are needed since the current usage 

of “engine start” is not applicable for such vehicles, since the definition of “engine start” 

in subsection (c) does not comprehend engine restarts. 

Subsection (f)(4.1) The purpose of this subsection is to require manufacturers to 

monitor the cold start emission reduction strategy on gasoline engines. The new 

proposed subsection (f)(4.1.2), which would require manufacturers to use different 

diagnostics to distinguish component/element faults that occur while the cold start 

strategy is active from faults that occur while the strategy is not active (e.g., warmed-up 

conditions), is needed to avoid confusion and prevent manufacturers from using only 

one fault code/monitor to detect both types of faults – this new subsection would 

prevent premature erase of pending fault code. 

Subsection (f)(5.2.2) The proposed change is needed for formatting reasons, 

since the original text in subsection (f)(5.2.3) is now in subsection (f)(5.2.4). 

Subsection (f)(5.2.3) The purpose of this subsection is to require manufacturers to 

detect a functional fault of the secondary air system if a fault does not cause emissions 

to exceed a specific threshold. The proposed changes are needed to clarify that this 

subsection is related to faults that cause a decrease in air flow. 

Subsection (f)(5.2.4) This new proposed subsection, which requires 

manufacturers to detect a functional fault of the secondary air system if a fault that 

causes an increase in air flow does not cause emissions to exceed a specific threshold, 

is needed to completely cover all faults of the secondary air system and be consistent 

with what is required for other component/system monitors. 

Subsection (f)(7.1) The purpose of this subsection is to require manufacturers to 

monitor the evaporative system. The proposed changes to change “vehicles not 

required to be equipped with evaporative emission systems” to “vehicles not subject to 

evaporative emission standards” is needed since ARB regulations technically do not 

mandate engines to be equipped with evaporative systems but, instead, establish 

evaporative emission standards and identify which vehicles are subject to the 

standards. The proposed additional language requiring manufacturers to propose a 

monitoring plan for alternate-fueled engines is needed since some alternate-fueled 

engines are subject to the evaporative emission standards, and thus to evaporative 

system monitoring, but have evaporative systems that are different from gasoline 

engines, so the current monitoring requirements are not applicable. 

Subsection (f)(7.2.5) The purpose of this subsection is to require manufacturers to 

monitor multiple purge flow paths on a vehicle. The proposed change of “vehicles” to 

“engines” is needed since the reference to “engines” is more appropriate. The 

proposed change of “both purge flow paths” to “all purge flow paths” is needed to 
72

correct an error, since vehicles can have more than two purge flow paths and should 

monitor all these purge flow paths. 

Subsection (f)(8.4) The purpose of this subsection is to describe the MIL 

illumination and fault code storage requirements for exhaust gas sensors. The 

proposed addition of language to separately detect and store different fault codes for 

circuit and out-of-range faults is needed for emphasis since some manufacturers have 

been inappropriately storing the same fault code for different circuit and out-of-range 

faults, even though section (h)(4.4) currently requires manufacturers to pinpoint the 

likely cause of a malfunction. 

Subsection (g)(1.3.1) The purpose of this subsection is to describe the conditions 

under which thermostat monitoring shall occur. The proposed changes to subsection 

(g)(1.3.1)(A) is needed for formatting reasons due to the changes mentioned here. The 

proposed changes to subsection (g)(1.3.1)(D) and proposed additional subsection 

(g)(1.3.1)(E) are needed to make the requirement easier to understand and clearly 

indicate under what conditions the thermostat monitor can be disabled. The proposed 

change of subsection (g)(1.3.1)(E) to (g)(1.3.1)(F) is needed for formatting reasons. 

Subsection (g)(3.1.1) The purpose of this subsection is to require manufacturers to 

monitor comprehensive components. The proposed change to delete “engine” from 

“electronic engine powertrain component/system” is needed since the monitoring 

requirements under this subsection are not limited to component/systems on the 

engine. 

Subsection (g)(3.1.3) The purpose of this subsection is to require manufacturers to 

require manufacturers to monitor electronic powertrain input or output 

components/systems associated with systems/components that are driven by the 

engine and not related to control of fueling or emissions only if the component/system is 

used as part of the diagnostic strategy of a monitored component/system. The 

proposed addition of “transmission” is needed to make clear that transmission 

components/systems are required to meet this subsection. 

Subsections (g)(3.1.4) and (g)(3.1.5) The proposed change of “hybrids” to “hybrid 

vehicles” is needed to be consistent with the terminology used in the definitions in 

section (c). The proposed change to allow the requirements of subsection (g)(3.1.5) to 

be superseded by section (d)(7.6) is needed to account for the new proposed 

subsection (d)(7.6), which allows manufacturers to be exempt from meeting the 

requirements of section 1971.1 in the 2013 model year. 

Subsection (g)(3.2.2)(B)(ii)d. The purpose of this subsection is to require 

manufacturers to monitor the diesel idle control system. The proposed change to 

require detection of faults if the fuel injection quantity is not within a certain range 

necessary to achieve the target idle speed for the “known”, not “given”, operating 

conditions is needed to address manufacturers concerns about the inability to know all 

the “given” operating conditions to determine the appropriate fuel quantity. 
73

Subsection (g)(3.2.2)(F) The purpose of this subsection is to require 

manufacturers to monitor the fuel control system components for proper compensation. 

The proposed delay of the required start date to the 2015 model year is needed to allow 

manufacturers more time to meet the requirement. The new proposed subsection 

(g)(3.2.2)(F)(ii) allowing manufacturers to be exempt from this monitoring requirement if 

certain conditions are met is needed to allow manufacturers relaxation in meeting this 

requirement based on their concerns. 

Subsection (g)(5.1) The purpose of this subsection is to allow manufacturers to 

revise the required malfunction criteria if certain conditions are met. The proposed 

change of the phrase “prevent significant errors of commission in detecting a 

malfunction” to “prevent false indications of a malfunction” is needed for clarify and to 

avoid confusion. The proposed amendments to limit the allowance for manufacturers to 

exclude detection of specific failure modes for PM filter monitoring up to the 2015 model 

year is needed since this allowance provides an unknown risk for failures that cause 

high PM emissions to go undetected, which should not be allowed on all future engines 

nor needed based on new monitoring techniques being developed for future engines. 

Subsection (g)(5.7) The purpose of this new proposed subsection is to allow 

manufacturers to be exempt from monitoring a component if a failure only affects 

emissions or other diagnostics when the ambient temperature is below 20 degrees 

Fahrenheit. This proposed allowance is needed to address manufacturers’ concerns 

about expending resources to monitor such components that only affect emissions 

during extreme conditions. 

Subsection (g)(5.8) The purpose of this new proposed subsection is to allow 

manufacturers to use an alternate phase-in schedule, in accordance with the definition 

in subsection (c), and allow small volume manufacturers to use a different 

implementation schedule (as described in new subsection (g)(5.8.2)) in lieu of the 

required phase-in schedule. This proposal is needed to allow manufacturers more lead 

time to meet the requirements. 

Subsection (g)(5.9) This proposed change of this subsection from (g)(5.7) to 

(g)(5.9) is needed for formatting reasons. 

Subsection (h)(1) The purpose of this subsection is to indicate the SAE and 

ISO documents incorporated by reference in the regulation. The proposed updates to 

the SAE and ISO documents are needed to reference the most recent versions of these 

documents, which include some clarifications and modifications to the standardized 

requirements for the HD OBD systems. 

Subsection (h)(2) The purpose of this subsection is to specify the requirements 

for the diagnostic connector. The proposed changes are needed to account for the new 

500 kbps baud rate variant of SAE J1939 and its associated connector being allowed 

for communication protocol. The proposed language in subsections (h)(2.6.1) and 
74

(h)(2.6.2) prohibiting additional identical connectors from being located in the same area 

as the standardized OBD connector is needed to avoid confusion among technicians 

and inspectors attempting to identify the correct connector to retrieve OBD information 

from. 

Subsection (h)(3.2) The purpose of this subsection is to indicate the 

communication protocol allowed to be used on the engines. The proposed addition of 

“including diesel engines converted to alternate-fueled engines” is needed so that the 

requirement in subsection (h)(7), where the language was originally located, can be 

deleted. The proposed changes indicating the 250 kbps and 500 kbps baud rates are 

needed to account for the recent addition of the 500 kbps baud rate variant to SAE 

J1939. The proposed change to prohibit usage of the 250 kbps baud rate variant 

starting in the 2016 model year is needed to account for the industry trend towards 

using the 500 kbps baud rate variant and to mitigate potential problems in the field that 

may result with allowing multiple variants for communication protocol. 

Subsection (h)(4.1) The purpose of this subsection is to describe the 

requirements for the readiness status. The proposed changes to the language are 

needed for clarity, to make the requirements easier to understand, and avoid confusion 

among manufacturers by identifying the specific monitors that are required to be 

included in the readiness status for a specific monitored component/system. 

Subsection (h)(4.2.2) The purpose of this subsection is to describe the data 

stream parameters required to be made available. The proposed change to subsection 

(h)(4.2.2)(E) is needed to better ensure standardization by clarifying the specific SPNs 

to be used. The new proposed subsection (h)(4.2.2)(G) is needed to make it easier to 

conduct valid in-use emission tests with PEMS. The proposed change in subsection 

(h)(4.2.2)(H) is needed to account for new subsection (h)(4.2.2)(G). 

Subsection (h)(4.2.3)(E) This new proposed subsection, which requires 

engines equipped with reductant quality sensors and NOx sensors to make the 

reductant quality sensor output and the corrected NOx sensor output available to a scan 

tool, is needed since more and more manufacturers are using the reductant quality 

sensor and technicians will need access to both these signals to help diagnose 

malfunctions. 

Subsections (h)(4.4.1)(F) and (h)(4.4.2)(F) The purpose of these subsections is to 

describe the standardized requirements for permanent fault codes. The proposed 

changes to subsections (h)(4.4.1)(F)(iv) and (h)(4.4.2)(F)(iv), which limit the resetting of 

readiness bits to those modules that report any supported readiness bits except the bit 

for the comprehensive components when the control module containing the permanent 

fault code is reprogrammed, are needed to address manufacturers’ concerns about the 

difficulty in resetting the readiness bits in ‘all’ control modules. 

Subsection (h)(4.7) The purpose of this subsection is to describe the 

standardized requirements for CVN. The proposed deletion of language from 
75

subsection (h)(4.7.4) is needed since this language was moved to new proposed 

subsection (h)(4.7.5). The new proposed subsection (h)(4.7.5) is needed to clarify the 

requirements for making CVN immediately available through the data link connector and 

to prevent manufacturers from inappropriately using extended message timing for 

replies or negative response codes. 

Subsection (h)(4.8.3) The purpose of this subsection is to describe the 

standardized requirements for VIN and ESN. The proposed change to this subsection, 

which limits the resetting of readiness bits to those modules that report any supported 

readiness bits except the bit for the comprehensive components when the VIN or ESN 

is reprogrammed, are needed to address manufacturers’ concerns about the difficulty in 

resetting the readiness bits in ‘all’ control modules. 

Subsection (h)(4.10.2) The purpose of this subsection is to describe the conditions 

under which all emission-related diagnostic information is required to be erased. The 

proposed change to this subsection is needed to indicate that the requirements in 

section (h)(4.4.1)(F)(iv), (h)(4.4.2)(F)(iv), and (h)(4.8.3) supersede the requirements of 

this subsection. 

Subsection (h)(5.2.2) The proposed deletion of this subsection is needed since the 

specific requirements are already specified in SAE J1979 and J1939. 

Subsection (h)(7) The proposed deletion of this subsection is needed since the 

requirements have been moved to subsection (h)(3.2). 

Subsection (i) The purpose of this subsection is to describe the 

requirements for demonstration testing. The proposed changes throughout the 

subsection with relation to the term “emission threshold malfunction criteria” and 

“malfunction limit” are needed to maintain consistency within the section. The proposed 

deletions of “FTP” from “FTP standard” throughout the subsection are needed to be 

consistent with the term used throughout subsections (e) and (f). 

Subsection (i)(3.1.2) The purpose of this subsection is to describe the 

demonstration testing requirements for diesel misfire monitoring. The proposed change 

to exempt manufacturers from testing the diesel misfire monitor is needed since the 

malfunction criteria for diesel misfire monitoring in subsection (e)(2) is no longer tied to 

an emission threshold. 

Subsection (i)(3.2.1) The purpose of this subsection is to describe the testing 

requirements for gasoline fuel system monitors. The proposed addition in subsection 

(i)(3.2.1)(A) and the proposed deletion in subsection (i)(3.2.1)(E) are needed since the 

language at issue does not apply to all fuel system monitors, such as the air-fuel 

cylinder imbalance monitor. The new proposed subsection (i)(3.2.1)(C) describing the 

testing requirements for the air-fuel cylinder imbalance monitor is needed since such 

language was mistakenly left out. 
76

Subsection (i)(3.2.7) The purpose of this subsection is to describe the testing 

requirements for gasoline exhaust gas sensor monitors. The proposed changes are 

needed to allow manufacturers to test only certain response rate malfunctions (e.g., 

worst case malfunctions) to limit the number of tests performed. 

Subsection (i)(3.3.1) The proposed change of “applicable emission standards” to 

“applicable standards” is needed since “applicable standards” is the more appropriate 

term to use. 

Subsection (i)(3.6) This new proposed subsection is needed to avoid 

manufacturer confusion by clearly stating that demonstration testing is not required for 

functional monitors, since they are not tied to an emission threshold. 

Subsection (i)(5.1.3) The purpose of this subsection is to describe the procedure 

that must be taken when the MIL does not illuminate when the malfunction is set at the 

limits during demonstrating testing. The proposed changes are needed to clarify the 

testing procedures for catalyst faults and other faults where default actions are taken 

subsequent to fault detection, since the original language is not clear on this. 

Subsection (j)(2.2) The proposed deletion of “July 7, 2009, incorporated by 

reference” is needed since this phrase was already stated previously in the regulation. 

The proposed change in subsection (j)(2.2.2)(H) to require diesel engines to use units of 

“mg/stroke” for all fuel quantity based criteria is needed since “mg/stroke” is already 

more commonly used and appropriate for diesel engines than the “per crankshaft 

revolution” units currently required. 

Subsection (j)(2.5) The purpose of this subsection is to describe the gasoline 

misfire monitor information required to be included in the certification application. The 

proposed changes are needed to indicate that the required data are to be submitted in 

the standardized formats detailed in ARB Mail-Out #MSC 09-22, which will assist staff 

during certification review. 

Subsection (j)(2.6) The proposed deletion of the requirement to include 

information related to the heated catalyst system is needed since the original inclusion 

of this requirement was a mistake, given that the HD OBD regulation does not have 

monitoring requirements for heated catalyst systems. The new proposed requirement 

for manufacturers to provide diesel misfire monitor data is needed to support the new 

diesel misfire monitoring requirements being proposed in subsection (e)(2) and to 

ensure that the diesel misfire monitor is robust in detecting misfires. 

Subsection (j)(2.16) The proposed additional requirement to include information 

about all other issues that apply to the engine is needed to assist staff in reviewing the 

application. 

Subsection (j)(2.18) Staff is proposing to move the original language in 

subsection (j)(2.18) to subsection (j)(2.21). The new proposed requirement in 
77

subsection (j)(2.18) to include information related to the in-use performance data is 

needed to assist staff in reviewing the application. 

Subsections (j)(2.19) and (j)(2.20) The new proposed requirements to include 

information related to test results and the required timelines for submitting results for the 

production engine/vehicle testing are needed to assist staff in reviewing the application. 

Subsection (k)(1) The purpose of this subsection is to describe the 

requirements for certifying with a deficiency. The proposed additional language is 

needed to make clear that deficiencies will not be granted for issues that would subject 

to an ordered recall under section 1971.5. 

Subsection (k)(6.1) The purpose of this subsection is to describe the criteria and 

timelines under which a retroactive deficiency can be applied. The proposed change to 

extend the deadline of “three months after commencement of the start of vehicle 

production” to “six months after commencement of the start of vehicle production” is 

needed to align with the proposed deadline in subsection (l)(2.1). 

Subsection (k)(7) The purpose of this new proposed subsection is to describe 

the exceptions to the fine requirements for PM filter and PM sensor-related monitor 

deficiencies. The proposed change to allow for “free deficiencies” for specific PM filter 

and PM sensor monitors is needed to account for the fact that PM sensors are a new 

technology and manufacturers that use them in the early years may have difficulty 

developing robust monitors to meet the requirements in the current regulation. 

Subsection (k)(8) The purpose of this new proposed subsection is to describe 

the carry-over allowances and the exceptions to the fine requirements for hybrid vehicle 

deficiencies. The proposed allowances and exceptions are needed to provide 

relaxation to manufacturers and allow them to certify their hybrid vehicles to the HD 

OBD requirements in the initial years. 

Subsection (k)(9) The purpose of this new proposed subsection is to indicate 

that OBD systems that fail to meet the requirements of section 1971.1 and have not 

been granted deficiencies pursuant to subsection (k) are considered non-compliant and 

subject to enforcement. This language is already implied but its inclusion is necessary 

to make it clear to manufacturers. 

Subsection (l)(1) The purpose of this subsection is to require manufacturers to 

perform verification testing of the standardized requirements. The proposed change in 

subsection (l)(1.1) is needed to make clear that the testing is to be done on production 

engines. The proposed change in (l)(1.4.3)(B) is needed for formatting reasons, since 

the original requirement in subsection (h)(4.1.3) is now in (h)(4.1.6). The proposed 

change in subsection (h)(4.1.3)(E) to include MIL command status is needed to ensure 

the correct information is being made available, and the proposed change to require 

this information from each diagnostic and emission critical electronic powertrain control 

unit is needed for better assurance that the OBD system as a whole is working as 
78

certified. Finally, the proposed changes to subsection (l)(1.5.1), which would require 

manufacturers to submit the test results (i.e., the test log file), is needed since this is 

important data for staff in determining if the system is working correctly. 

Subsection (l)(2.1) The purpose of this subsection is to require manufacturers to 

perform testing to verify the monitoring requirements within a certain timeline. The 

proposed change to extend the deadline of “three months after the start of vehicle 

production” to “six months after the start of vehicle production” is needed to allow 

manufacturers more time to conduct this testing, since they indicated it was difficult to 

procure the vehicles within the current required timeline. 

Subsection (l)(2.3.4) The proposed change of “emission standard” to “emission 

threshold malfunction criteria (e.g., 2.0 times the standard)” is needed to correct an 

error. 

Subsection (l)(2.3.6) The purpose of this subsection is to allow manufacturers to 

be exempt from testing specific diagnostics if certain conditions are met. The proposed 

allowance to exempt testing on monitors where demonstration may jeopardize the 

safety of the tester is needed to ensure the safety of the individuals conducting the 

testing. 

Subsection (l)(3.4) The purpose of this subsection is to require manufacturers to 

submit specific information related to their in-use monitor performance testing. The 

proposed changes are needed to make the required information consistent with what is 

required in ARB Mail-Out #MSC 09-22. 

Proposed amendments to Cal. Code Regs., title 13, section 1968.2: 

Subsection (a) The “Purpose” clause of the regulation has been amended to 

reaffirm and clarify the objectives of the regulation consistent with the longstanding 

expressed intent when the regulation was first adopted and subsequently amended. 

 

Subsection (c) “Alternate phase-in” The proposed change to the definition is 

needed since the definition states the percentages described in the phase-in schedules 

are to be based on the manufacturer’s projected sales volume of “all vehicles”, while 

some phase-in schedules described in section (e) and (f) specifically indicate that the 

percentages are not based on all vehicles (e.g., based on only diesel vehicles). 

Subsection (c) “Emission standard” The addition of this definition is needed to 

clarify that the OBD regulations include emission standards. The definition revises the 

definition set forth at Health and Safety Code section 39028 consistent with the express 

authorization of the Board to make such a revision in Health and Safety Code sections 

39010 and 39601. 
79

Subsection (c) “Evaporative emission standards” The new proposed definition is 

needed to identify a subcategory of the new definition of emission standard that had 

previously been identified merely as an emission standard. 

Subsection (c) “Exhaust emission standards” or “tailpipe emission standards” 

The new proposed definition is needed to identify a subcategory of the new definition of 

emission standard that had previously been identified merely as an emission standard. 

Subsection (d)(3.2.1) The purpose of this subsection is to indicate which monitors 

are required to meet a minimum in-use performance ratio of 0.100. The proposed 

change to subsection (d)(3.2.1)(D) of “introductory years” to “interim years” since the 

new proposed subsection (d)(3.2.1)(D)(vi) does not apply to “introductory years.” The 

new proposed subsection (d)(3.2.1)(D)(vi) requiring a minimum ratio of 0.100 for PM 

filter monitors on 2015 through 2018 model year medium-duty vehicles is needed to 

allow interim relaxation for these monitors, which would be required to start using the 

more frequently incremented general denominator starting in the 2015 model year (as 

required in subsection (d)(4.3.2)(G)) and thus may result in lower ratios and require the 

manufacturer to gain some experience before being held to a higher ratio. 

Subsection (d)(4.3.2)(F) The purpose of this subsection is to describe the 

specifications for incrementing the denominator for components that are “commanded” 

to function. The proposed change to delete “output” from “output components” is 

needed since some of the component monitors listed under this section are not output 

components. The proposed addition of the PM filter active/intrusive injection monitor to 

this section is needed since the previously required denominator incrementing criteria 

applied to this monitor were not appropriate. Additionally, the proposed changes to 

allow 2013 through 2015 model year vehicles to use the previously required 

denominator criteria for the PM filter active/intrusive injection monitor and the PM 

sensor heater monitor are needed to allow lead time for manufacturers to meet the new 

requirement. 

Subsection (d)(4.3.2)(G) The purpose of this subsection is to describe the 

specifications for incrementing the denominator for components or emission controls 

that experience infrequent regeneration events. The proposed change to limit 

application of this requirement to the 2004 through 2015 model year for the PM filter 

filtering performance monitors and the PM filter missing substrate monitors to is needed 

considering the importance of the PM filter, which controls emissions throughout the 

driving cycle, not just every 500 miles. 

Subsection (d)(4.3.2)(I) The purpose of this subsection is to describe the 

specifications for incrementing the denominator for some monitors based on whether or 

not a regeneration event occurs. The proposed deletion of “PM filter active/intrusive 

injection” is needed since this monitor was moved to subsection (d)(4.3.2)(F). 

Subsection (e)(6.1.1) The purpose of this subsection is to indicate the general 

requirement for diesel fuel system monitoring. The proposed change of “emission 
80

standard” to “applicable standard” is needed since “applicable standard” is the more 

appropriate term to use. 

Subsection (f)(1.2.3)(B) The purpose of this subsection is to require 

manufacturers to monitor the NMHC converting catalyst for proper feedgas generation. 

The proposed language allowing manufacturers to be exempt from this monitoring 

requirement if certain conditions are met is needed to allow manufacturers relaxation in 

meeting this requirement based on their concerns. 

Subsection (f)(2.2.2)(A)(i) The purpose of this subsection is to require 

manufacturers to monitor the NOx converting catalyst conversion efficiency. The 

proposed changes to allow higher interim emission thresholds for 2013 through 2015 

model year vehicles in new proposed subsection (f)(2.2.2)(A)(ii)c. and to delay the final, 

stringent emission thresholds to 2016 in subsection (f)(2.2.2)(A)(ii)d. are needed to 

address manufacturers’ concerns about meeting the requirements and to allow 

manufacturers more time to meet the final thresholds. 

Subsection (f)(3.1.1) The purpose of this subsection is to indicate the general 

requirement for diesel misfire monitoring. The proposed deletion of “causing excess 

emissions” from “misfire causing excess emissions” is needed since the proposed 

changes to the diesel misfire monitoring for medium-duty vehicles now involve detection 

of faults when the percentage of misfire exceeds a certain level, not when a specific 

emission threshold is exceeded. 

Subsection (f)(3.2.2) The purpose of this subsection is to require manufacturers to 

monitor for misfire on diesel engines. The proposed change to require all diesel 

engines to meet subsection (f)(3.2.2) with a phase-in starting in the 2016 model year is 

needed since the current requirement to monitor for misfire only at idle will not detect 

misfire faults that occur only during other engine speed and load conditions. The 

proposed change to require misfire detection when the percentage of misfire exceeds 5 

percent instead of when specific emission thresholds are exceeded in subsection 

(f)(3.2.2)(A)(ii) is needed to address manufacturers’ concerns about difficulties in 

establishing a correlation between a specific misfire level and a tailpipe emission 

threshold. The proposed change to subsection (f)(3.2.3) is needed for formatting 

reasons, since the malfunction criteria originally in subsection (f)(3.2.2)(B) is now in 

subsection (f)(3.2.2). The proposed new subsection (f)(3.2.5) to allow manufacturers to 

detect misfire at a higher percentage than the required 5 percent if specific emission 

levels are not exceeded is needed to provide relaxation to manufacturers should their 

system be abnormally robust to an emission increase due to misfire. 

Subsection (f)(3.3.1) The purpose of this subsection is to describe the conditions 

under which diesel misfire monitoring shall occur. The proposed changes are needed 

to avoid confusion by indicating that the monitoring conditions under this subsection 

apply to misfires identified in section (f)(3.2.1). 
81

Subsection (f)(3.3.3) The purpose of this subsection is to describe the conditions 

under which diesel misfire monitoring shall occur. The proposed change to require 

monitors for misfires identified in section (f)(3.2.2) to meet subsection (f)(3.3.3) is 

needed for clarity. The proposed changes to the required monitoring conditions in 

subsection (f)(3.3.3)(B) are needed to address manufacturers’ concerns about the 

extent to which they can monitor for misfire on diesel engines given the wide range of 

medium-duty applications that exist up to the 2018 model year, while the proposed 

requirement to continuously monitor for misfire under all positive torque engine speed 

and load conditions with a phase-in starting in the 2019 model year in subsection 

(f)(3.3.3)(B)(ii) is needed to ensure misfires that occur during the higher operating 

ranges are detected. Lastly, the proposed change in subsection (f)(3.3.3)(C) is needed 

to allow manufacturers to disable misfire monitoring under conditions in which robust 

detection of misfires is at issue to prevent misdetections. 

Subsection (f)(3.4.2) The proposed change of subsection (f)(3.2.2)(B) to (f)(3.2.2) 

is needed for formatting reasons. 

Subsection (f)(4.1) The purpose of this subsection is to indicate the general 

requirement for gasoline fuel system monitoring. The proposed change of “emission 

standard” to “applicable standard” is needed since “applicable standard” is the more 

appropriate term to use. 

Subsection (f)(5.2.2)(A)(ii) The purpose of this subsection is to require 

manufacturers to monitor the NOx sensor performance. The proposed changes to allow 

higher interim emission thresholds for 2013 through 2015 model year vehicles in new 

proposed subsection (f)(5.2.2)(A)(ii)c. and to delay the final, stringent emission 

thresholds to 2016 in subsection (f)(2.2.2)(A)(ii)d. are needed to address manufacturers’ 

concerns about meeting the requirements and to allow manufacturers more time to 

meet the final thresholds. 

Subsection (f)(5.3.1) The purpose of this subsection is to indicate the conditions 

under which NOx sensor monitoring shall occur. The proposed addition of section 

(f)(5.2.2)(D), for sensor monitoring capability monitors, to subsection (f)(5.3.1)(A) is 

needed since this monitor has been determined to be important based on reviews of 

manufacturers’ OBD systems, so there should be assurance that the in-use monitoring 

performance data of this monitor is tracked and reported starting in the 2016 model year 

for medium-duty vehicles. The proposed deletion of section (f)(5.2.2)(D) from 

subsection (f)(5.3.1)(B) is needed since this subsection was moved to subsection 

(f)(5.3.1)(A) as previously described. 

Subsection (f)(9.2.1) The purpose of this subsection is to require manufacturers to 

monitor the PM filter filtering performance. The proposed changes to allow exclusion of 

specific failure modes for 2014 through 2015 model year engines in subsection 

(f)(9.2.1)(A)(ii)c. and subsection (f)(9.2.1)(A)(iii) are needed to address manufacturers’ 

concerns about meeting the requirements, given the delay of the availability of PM 

sensors. The new proposed subsection (f)(9.2.1)(A)(iv) is needed to prohibit 
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manufacturers from using an alternate phase-in schedule instead of the required phasein schedule proposed in subsection (f)(9.2.1)(A)(iii). 

Subsection (f)(9.2.4) The purpose of this subsection is to require manufacturers to 

monitor the catalyzed PM filter. The proposed language allowing manufacturers to be 

exempt from monitoring the NMHC conversion capability if certain conditions are met is 

needed to allow manufacturers relaxation in meeting this requirement based on their 

concerns. 

Subsection (f)(15.2.2)(F) The purpose of this subsection is to require 

manufacturers to monitor the fuel control system components for proper compensation. 

The new proposed subsection (f)(15.2.2)(F)(ii) allowing manufacturers to be exempt 

from this monitoring requirement if certain conditions are met is needed to allow 

manufacturers relaxation in meeting this requirement based on their concerns. 

Subsection (f)(17.1) The purpose of this subsection is to allow manufacturers to 

revise the required malfunction criteria if certain conditions are met. The proposed 

change of the phrase “prevent significant errors of commission in detecting a 

malfunction” to “prevent false indications of a malfunction” is needed for clarify and to 

avoid confusion. The proposed extension of the allowance for manufacturers to exclude 

detection of specific failure modes for PM filter monitoring is needed to recognize one of 

the issues with monitoring strategies that do not use a PM sensor and to allow 

manufacturers to certify the OBD II systems on their medium-duty vehicles up to the 

2015 model year. 

Subsection (f)(17.1.5) The purpose of this subsection is to describe the monitoring 

requirements and malfunction criteria for medium-duty diesel vehicles certified to a 

chassis-dynamometer tailpipe emission standard. The proposed change to limit this 

subsection to the 2004 through 2015 model years is needed since new requirements for 

2016 and subsequent model year vehicles are being proposed in new subsection 

(f)(17.1.6). 

Subsection (f)(17.1.6) The purpose of this new proposed subsection is to describe 

the monitoring requirements and malfunction criteria for 2016 and subsequent model 

year medium-duty diesel vehicles certified to a chassis-dynamometer tailpipe emission 

standard. This subsection is needed to give clear direction to medium-duty 

manufacturers about what they are required to meet for these vehicles and to eliminate 

the requirement for manufacturers to individually propose chassis-based thresholds and 

seek Executive Officer approval. 

Subsection (f)(17.2.2) The purpose of this subsection is to allow manufacturers to 

use an alternate phase-in schedule, in accordance with the definition in subsection (c), 

in lieu of the required phase-in schedule. The proposed language to meet this language 

except for what is described for the PM filter monitor in section (f)(9.2.1)(A) is needed 

since this section specifically prohibits manufacturers from using an alternate phase-in 

plan for the PM filter monitor. 
83

Subsection (f)(17.2.3) The purpose of this subsection is to allow small volume 

manufacturers to use a different implementation schedule in lieu of the required phasein schedule. The proposed additional language is needed to clarify the acceptable 

phase-in schedule small volume manufacturers can use in lieu of the required phase-in 

schedule for the diesel PM filter monitor. 

Subsection (h)(4.3) The purpose of this subsection is to describe the 

demonstration testing requirements for diesel misfire monitoring. The proposed change 

to this subsection is needed to specifically require demonstration testing only for those 

vehicles with misfire monitors calibrated to an emission malfunction threshold (i.e., 

those meeting section (f)(3.2.2)(A)(i)). 

Subsection (i)(1.1) The purpose of this subsection is to describe the certification 

documentation requirements. The proposed addition of “exhaust” to “emission 

standard” is needed since “exhaust emission standard” is the more appropriate term to 

use. 

Subsection (i)(2.5) The purpose of this subsection is to describe the misfire 

monitor information required to be submitted as part of the certification application. The 

proposed change to separate the original language into different parts in subsection 

(i)(2.5.1)(A) through (D) is needed for better readability. The proposed change to 

subsection (i)(2.5.1)(D) is needed for formatting reasons to account for the change 

described above. The new proposed subsection (i)(2.5.2) for manufacturers to provide 

diesel misfire monitor data is needed to support the new diesel misfire monitoring 

requirements being proposed in subsection (f)(3) and to ensure that the diesel misfire 

monitor is robust in detecting misfires. 

Subsection (j)(2.3.4) The purpose of this subsection is to describe the 

requirements for verification testing of monitoring requirements. The proposed change 

of “emission standard” to “malfunction threshold (e.g., 1.5 times the applicable 

standards)” is needed to correct an error. 

Proposed amendments to Cal. Code Regs., title 13, section 1971.5: 

Subsection (a)(3) “OBD Emission Testing” The proposed change to add a “d” to 

“measure” in this definition is needed to correct a grammatical error. 

Subsection (b)(3)(C)(i) The purpose of this subsection is to describe the protocol for 

procuring engines for a test group sample. The proposed deletion in this subsection is 

needed to correct an error, since the deleted language was mistakenly taken from the 

OBD II enforcement regulation and not appropriate for the HD OBD enforcement 

regulation. 
84

Subsection (b)(3)(D)(ii)b. The purpose of this subsection is to describe the 

criteria for which engines are to be included in a test sample group for OBD ratio 

testing. The proposed changes to subsection (b)(3)(D)(ii)b.3. are needed to ensure less 

difficulty in procuring applicable engines, since the engine would have needed to 

accumulate a very high mileage before the denominators for the diesel PM filter, PM 

sensor, and NMHC converting catalyst monitors specified were acceptable for inclusion 

in the test sample group with the original language. The proposed change to 

subsection (b)(3)(D)(ii)b.4. is needed to make clear what monitors are required to have 

denominators meeting the value in this subsection versus the value in subsection 

(b)(3)(D)(ii)b.3. 

Subsection (b)(6)(A) The purpose of this subsection is to describe the criteria for 

determining nonconformance for OBD emission testing. The proposed deletions of “on 

the applicable standard (i.e., FTP or SET)” is needed to correct wording errors. The 

proposed changes in subsection (b)(6)(A)(iii) of reference to section 1971.1(e)(8.2.1)(C) 

to section 1971.1(e)(8.2.1)(D) and (E) are needed for formatting reasons based on the 

proposed changes to section 1971.1. The proposed changes in subsections 

(b)(6)(A)(iii) and (b)(6)(A)(iv) of “either” to “any” are needed for clarity. 

Subsection (b)(6)(B) The purpose of this subsection is to describe the criteria for 

determining nonconformance for OBD ratio testing. The proposed changes related to 

PM filter filtering performance and missing substrate monitors for the 2016 through 2018 

model years are needed to allow some relaxation during these model years based on 

the proposed changes made to subsection 1971.1(d)(4.3.2)(G). 

Subsection (b)(6)(C)(ii)b. The proposed change to this subsection is needed for 

formatting reasons based on the proposed changes to section 1971.1. 

Subsection (d)(3)(A)(i) The purpose of this subsection is to describe the mandatory 

recall criteria for OBD ratio testing. The proposed addition of “and subject to the 

nonconformance criteria on section (b)(6(B)(ii)” is needed to allow 2016 through 2018 

model year PM filter filtering performance and missing substrate monitors to be exempt 

from mandatory recall and to allow some relaxation during these model years based on 

the proposed changes made to subsection 1971.1(d)(4.3.2)(G). 

Subsection (d)(3)(A)(ii)b.2. The proposed change to this subsection is needed for 

formatting reasons based on the proposed changes to section 1971.1. 

Subsection (d)(3)(A)(iii) The purpose of this subsection is to describe the 

mandatory recall criteria for misfire monitors. The new proposed subsection 

(d)(3)(A)(iii)b. is needed to account for the proposed changes made to the diesel misfire 

monitor requirements in section 1971.1(e)(2). 

Subsection (d)(3)(A)(vi) The purpose of this new proposed subsection is to 

describe additional mandatory recall criteria for the PM filter monitor. This subsection is 

needed to ensure that monitors unable to detect PM filter missing substrate faults that 
85

do not fall under the mandatory recall criteria in subsection (d)(3)(A)(ii) would still be 

subject to mandatory recalls. 

Subsection (d)(3)(A)(vii) The proposed change from (d)(3)(A)(vi) to 

(d)(3)(A)(vii) is needed for formatting reasons. 

Proposed amendments to Cal. Code Regs., title 13, section 1968.5: 

Subsection (b)(3)(D)(ii)b. The purpose of this subsection is to describe the 

criteria for which engines are to be included in a test sample group for OBD II ratio 

testing. The proposed changes to subsection (b)(3)(D)(ii)b.2. is needed to ensure less 

difficulty in procuring applicable engines, since the engine would have needed to 

accumulate a very high mileage before the denominators for the diesel PM filter, PM 

sensor, and NMHC converting catalyst monitors specified were acceptable for inclusion 

in the test sample group with the original language. The proposed changes to 

subsection (b)(3)(D)(ii)b.1. and 3. are needed make clear what monitors are required to 

have denominators meeting the value in these subsections versus the value in 

subsection (b)(3)(D)(ii)b.2. 

Subsection (b)(6)(A)(ii) The purpose of this subsection is to describe the 

criteria for determining nonconformance for OBD II emission testing of the intermediate 

diesel thresholds. The new proposed subsections (b)(6)(A)(ii)d. and e. are needed to 

account for the new interim thresholds being proposed for the NOx converting catalyst 

monitor and PM filter monitor in sections 1968.2(f)(2) and (f)(9). 

Subsection (b)(6)(A)(iii) The purpose of this subsection is to describe the 

criteria for determining nonconformance for OBD II emission testing of the final diesel 

thresholds. The proposed change to this subsection is needed to account for the 

changes being proposed for subsection (b)(6)(A)(ii) above. 

Subsection (b)(6)(B)(i)a. The purpose of this subsection is to describe the 

criteria for determining nonconformance for OBD II ratio testing of monitors certified to a 

ratio of 0.100. The proposed change of 2016 to 2018 is needed to account for the 

proposed addition of section 1968.2(d)(3.2.1)(D)(vi), which allows a minimum ratio of 

0.100 for PM filter filtering performance and missing substrate monitors on 2016 through 

2018 model year medium-duty vehicles. 

Subsection (c)(3)(A)(i) The purpose of this subsection is to describe the 

mandatory recall criteria for OBD II ratio testing. The proposed change of 2016 through 

2018 is needed to account for the proposed addition of section 1968.2(d)(3.2.1)(D)(vi), 

which allows a minimum ratio of 0.100 for PM filter filtering performance and missing 

substrate monitors on 2016 through 2018 model year medium-duty vehicles. 

Subsection (c)(3)(A)(ii) The purpose of this subsection is to describe the 

mandatory recall criteria for OBD II emission testing. The proposed change to allow the 

PM filter filtering performance monitor (section 1968.2(f)(9.2.1)) to be exempt from 
86

mandatory recall for 2013 model year medium-duty vehicles is needed to provide some 

relaxation to manufacturers and to ensure manufacturers are able to certify their OBD II 

system for the 2013 model year. 

Subsection (c)(3)(A)(iii) The purpose of this subsection is to describe the 

mandatory recall criteria for misfire monitors. The new proposed subsection 

(c)(3)(A)(iii)b. is needed to account for the proposed changes made to the diesel misfire 

monitor requirements in section 1968.2(f)(3). 

Subsection (c)(3)(A)(vi) The purpose of this new proposed subsection is to 

describe additional mandatory recall criteria for the PM filter monitor. This subsection is 

needed to ensure that monitors unable to detect PM filter missing substrate faults that 

do not fall under the mandatory recall criteria in subsection (c)(3)(A)(ii) would still be 

subject to mandatory recalls. 

Subsection (c)(3)(A)(vii) The proposed change from (c)(3)(A)(vi) to 

(c)(3)(A)(vii) is needed for formatting reasons. 
87

DOCUMENTS INCORPORATED BY REFERENCE 

Below is a list of documents newly incorporated by reference in the HD OBD regulation. 

1) ARB Mail-Out #MSC 09-22, “Guidelines for Heavy-Duty On-Board Diagnostic (HD 

OBD) Certification Data,” July 7, 2009. 

2) International Standards Organization (ISO) 15765-4:“Road Vehicles – Diagnostics 

Communications over Controller Area Network (CAN) – Part 4: Requirements for 

emission-related systems,” February 2011. 

3) Society of Automotive Engineers (SAE) J1699-3 – “Vehicle OBD II Compliance Test 

Cases”, December 2009. 

4) SAE J1930-DA “Electrical/Electronic Systems Diagnostic Terms, Definitions, 

Abbreviations, and Acronyms Web Tool Spreadsheet”, March 2012. 

5) SAE J1979 "E/E Diagnostic Test Modes," February 2012. 

6) SAE J1979-DA “Digital Annex of E/E Diagnostic Test Modes”, October 2011. 

7) SAE J2012-DA “Digital Annex of Diagnostic Trouble Code Definitions and Failure 

Type Byte Definitions”, July 2010. 

8) SAE J2403 “Medium/Heavy-Duty E/E Systems Diagnosis Nomenclature,” February 

2011. 

9) SAE J1939 Recommended Practice for a Serial Control and Communications 

Vehicle Network, April 2011. 

10) SAE J1939/01 On-Highway Equipment Control and Communication Network, May 

2011. 

11) SAE J1939/13 Off-Board Diagnostic Connector, October 2011. 

12) SAE J1939/21 Data Link Layer, December 2010. 

13) SAE J1939/31 Network Layer, May 2010. 

14) SAE J1939/71 Vehicle Application Layer (Through May 2010), March 2011. 

15) SAE J1939/73 Application Layer—Diagnostics, February 2010. 

16) SAE J1939/81 Network Management, June 2011. 

17) SAE J1939/84 OBD Communications Compliance Test Cases For Heavy Duty 

Components and Vehicles, December 2010. 
88

REFERENCES 

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 

Staff Report: Initial Statement of Reasons (ISOR): “Technical Status and Revisions to 

Malfunction and Diagnostic System Requirements for Heavy-Duty Engines (HD OBD) 

and Passenger Cars, Light-Duty Trucks, and Medium-Duty Vehicles and Engines 

(OBD II),” April 10, 2009