State of California 

AIR RESOURCES BOARD 

Notice of Public Availability of Modified Text and Availability of Additional 

Documents and/or Information

PUBLIC HEARING TO CONSIDER TECHNICAL STATUS AND PROPOSED 

REVISIONS TO ON-BOARD DIAGNOSTIC SYSTEM REQUIREMENTS FOR 

PASSENGER CARS, LIGHT-DUTY TRUCKS, AND MEDIUM-DUTY VEHICLES AND 

ENGINES, HEAVY-DUTY ENGINE ON-BOARD DIAGNOSTIC SYSTEM 

REQUIREMENTS, AND TO CONSIDER ENFORCEMENT PROVISIONS FOR 

HEAVY-DUTY ENGINE ON-BOARD DIAGNOSTIC SYSTEM REQUIREMENTS 

Public Hearing Date: May 28, 2009 

Public Availability Date: October 20, 2009 

Deadline for Public Comment: November 13, 2009 

At its May 28, 2009, public hearing, the Air Resources Board (ARB or Board) approved 

adoption of amendments to the California Code of Regulations, title 13, sections 1968.2 

and 1971.1, and adoption of California Code of Regulations, title 13, section 1971.5. 

Upon becoming operative, the amendments to sections 1968.2 and 1971.1 would 

respectively update the on-board diagnostic (OBD II) requirements for light-duty and 

medium-duty vehicles and engines and the heavy-duty on-board diagnostic (HD OBD) 

requirements for heavy-duty vehicles and engines. Section 1971.5 would establish 

enforcement procedures and requirements for HD OBD systems. 

At the hearing, the Board adopted Resolution 09-37, approving the proposed 

amendments to sections 1968.2 and 1971.1 and approving section 1971.5 as proposed 

but with such modifications that staff deemed necessary to address the comments 

received in response to the text attached to the Initial Statement of Reasons: Staff 

Report that was released on April 10, 2009. In the Resolution, the Board directed the 

Executive Officer to incorporate the modifications into the regulatory text, and to make 

such modifications available for a supplemental comment period of at least 15 days. 

Attachment I to this notice contains relevant portions of those sections of the 

regulations affected by the modifications being proposed with this notice. Proposed 

amendments that were initially published in the Staff Report released on April 10, 2009 

are denoted by single underline for additions to the text and single strikeout for 

deletions to the text. Additions to the text proposed with this notice are denoted by 

double underline and the deletions by double strikeout. The rationale for the 

modifications is set forth below. 

The resolution and all other regulatory documents for this rulemaking are available 

online at the following ARB website: 

http://www.arb.ca.gov/regact/2009/hdobd09/hdobd09.htm
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Summary of Proposed Modifications

Modifications to OBD II Regulation (section 1968.2)

1. Section 1968.2(d)(2.5.2)(B)(iii)d.: As part of the 45-day notice, staff proposed this 

new criterion that must be met before erasing a permanent fault code to maintain 

consistency with the HD OBD regulation. Specifically, if a permanent fault code has 

been stored for a monitor not subject to the minimum in-use ratio requirements and 

the fault information in the on-board computer has subsequently been cleared, staff 

proposed that the permanent fault code may be cleared if, in addition to the other 

conditions set forth in section 1968.2(d)(2.5.2)(B)(iii), the affected monitor has not 

re-detected the previously identified malfunction. However, when inserting the 

language in the OBD II regulation, staff mistakenly omitted the model year that this 

requirement would first be implemented. Staff has corrected the omission by 

specifying that manufacturers would be required to meet this requirement starting 

with the 2013 model year. 

2. Section 1968.2(d)(4.3.2)(G): To address confusion by manufacturers as to which 

specific monitors were required to meet the criteria set forth in the section and the 

conditions that must be met when incrementing the in-use monitor performance 

denominator, staff has added language that more precisely identifies the monitors 

covered by the section and has clarified the criteria for incrementing the 

denominator. Specifically, the language has been modified to clarify that a monitor’s 

denominator cannot be incremented if the vehicle has cumulatively travelled less 

than 500 miles since the denominator was last incremented. 

3. Sections 1968.2(d)(4.3.2)(I): As part of the 45-day notice, staff proposed new criteria 

that must be met for incrementing in-use monitor performance denominators for 

monitors that rely on regeneration events to maintain consistency with the HD OBD 

regulation. However, when inserting the language in the OBD II regulation, staff 

mistakenly omitted the model year in which the requirement would first be 

implemented. Staff has corrected the omission by specifying that manufacturers 

would be required to meet this requirement starting with the 2013 model year. 

Additionally, the initially proposed language did not include monitors of catalysts that 

are used to assist other aftertreatment systems during regeneration. The section 

has been amended to include these monitors because they are tied to regeneration 

events and it is appropriate that they be required to meet the denominator 

incrementing criteria in this section. 

4. Section 1968.2(f)(3.2.4): As part of the 45-day notice, staff proposed language that 

eliminated certain misfire conditions from the types of misfire that the OBD II system 

is required to detect. Specifically, misfire conditions where the misfire rate was 

more than 50 percent were excluded except in the case where a single component 

failure could cause a 50 percent or higher rate. To address confusion expressed by 
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manufacturers as to what the 50 percent or higher rate referred to, staff has added 

language to clarify that it is 50 percent “of all engine firings.” 

5. Section 1968.2(f)(7.2.3): For boost pressure control systems with variable geometry 

turbochargers, the current language requires functional monitors to indicate a fault 

when “proper functional response of the system to computer commands does not 

occur.” Staff recently proposed modifications to similar language in the heavy-duty 

OBD regulation (section 1971.1(e)(4.2.3)), requiring malfunction detection when “no 

detectable response to a change in commanded turbocharger geometry occurs,” as 

part of the 45-day notice. However, staff mistakenly forgot to propose the same 

changes to section 1968.2. Thus, to maintain consistency between the mediumduty OBD II and HD OBD diesel requirements, staff is proposing to change the 

language in section 1968.2(f)(7.2.3) to parallel that of section 1971.1(e)(4.2.3). 

6. Section 1968.2(f)(17.6): As previously adopted, this section allows manufacturers to 

disable monitors affected by power take-off (PTO) operation, provided readiness 

status is cleared (set to “not complete”) while the PTO unit is activated. This was 

done to allow valid disablement due to the unknown outside influences of the PTO 

device while still providing an indication to inspectors or technicians during PTO 

operation that the system is not fully functioning. Manufacturers have expressed 

concern that the provision as presently written does not cover applications that 

involve extensive mobile PTO operation (e.g., hydraulic pump operation for 

applications such as a salt spreader) and have requested a change to delay 

immediate clearing of the OBD readiness status until 750 minutes of cumulative 

PTO operation has occurred with the affected monitor disabled. With some further 

discussion, staff developed the proposed language to allow such an alternative 

strategy in the near term. Specifically, the change would allow manufacturers to 

continue to use the existing strategy or to use this new strategy that would not 

immediately clear all readiness status whenever the PTO is active. The new 

strategy would keep track of the cumulative time that the PTO device has been 

activated and the time since the affected monitor(s) had last run. Only if cumulative 

PTO operation reached 750 minutes and the affected monitor(s) had not run (e.g., 

neither during PTO operation where it was disabled nor during periods of engine 

operation between PTO operation, if they occurred) would the readiness status be 

cleared. This would allow vehicles with frequent PTO activation (including perhaps, 

PTO devices that cannot be easily disabled during an emission inspection) to output 

a valid readiness status that would allow for vehicle inspection of emissions and 

proper OBD II operation in all situations except where a sufficiently long period of 

time has passed since the monitor(s) last ran. 

7. Section 1968.2(g)(6.1): As part of the 45-day notice, staff proposed a change to the 

criteria that must be used to keep track of cumulative engine idle time to address 

manufacturers’ concerns that not all engines had access to vehicle speed, yet 

vehicle speed was a required element of the engine idle definition. This change was 

made for the HD OBD regulation and, for consistency, also included in the OBD II 
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regulation. However, when inserting the language in the OBD II regulation, staff 

mistakenly omitted the model year for which this change in the criteria would 

mandatorily apply. Staff has corrected the omission by specifying that 

manufacturers would have the option of using this new criteria immediately or to 

continue to use the old criteria through 2012 model year. The new criteria would 

become mandatory starting with the 2013 model year. 

Modifications to HD OBD Regulation (section 1971.1)

8. Sections 1971.1(c), (k)(6.1), (l)(1.2.1), and (l)(2.1): In response to questions from 

industry regarding various possible interpretations, a few changes have been made 

regarding use of the term “start of production”. In section (c), staff is now proposing 

modifications to the definition of “start of production” to include references to 

sections (k) and (l), which use the term in reference to engine and vehicle 

production. 

Staff is proposing modifications to section (k) to refer to “start of engine production” 

instead of “normal production.” Staff is also proposing to modify the timeline in 

section (k) for when the Executive Officer may issue retroactive deficiencies to be 

consistent with the timeline for manufacturers to perform verification of monitoring 

requirements under section (l)(2) -- specifically, the Executive Officer may issue a 

retroactive deficiency during either the first 6 months after commencement of the 

start of engine production or the first 3 months after commencement of the start of 

vehicle production, whichever ends later. This change is consistent with other parts 

of section (k), which already provides that retroactive deficiencies may be granted 

for problems found during this verification testing. Further, section (k) currently 

states that the deficiency would be “retroactive to the start of production.” However, 

since the definition of “start of production” in section (c) designates the start as when 

two percent of the projected engine or vehicle volume have been built, the current 

language in section (k) would technically exclude engines built before the two 

percent cut-point has been reached from receiving retroactive deficiencies, which 

was not staff’s intent. Thus, staff is proposing to modify the language in section (k) 

to have the deficiency retroactive to “all affected engines within the engine family.” 

Lastly, staff is proposing clarifications to sections (l)(1.2.1) and (l)(2.1) because of a 

manufacturer’s confusion about the requirements. Specifically, the current language 

states that production engine/vehicle testing of standardized requirements and 

monitoring requirements is required to be done “within” a number of months after 

the start of engine or vehicle production. However, the manufacturer interpreted this 

to mean that testing could not be done on engines/vehicles built “before” the defined 

start of production (i.e., before the two percent mark), which was not staff’s 

intention. Thus, staff is proposing modifications to clarify that testing may be done 

at any point before the specified number of months since start of production has 

expired. 
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9. Section 1971.1(d)(2.3.2)(D)(ii)b.3.: As part of the 45-day notice, for purposes of 

maintaining consistency with the OBD II regulation, staff proposed language more 

explicitly defining the conditions that must be met for HD OBD systems to clear a 

permanent fault code. This proposed language also included the one additional 

new criterion added for OBD II systems (described in item 1. under modifications to 

section 1968.2 above). However, when inserting this criterion in the HD OBD 

regulation, staff included this criterion only under the requirements for engines using 

the ISO 15765-4 protocol, mistakenly omitting this criterion for engines using the 

SAE J1939 protocol. Thus, staff has corrected the omission by including this 

criterion for engines using the SAE J1939 protocol. 

10. Section 1971.1(d)(4.3.2)(E): As part of the 45-day notice, staff proposed that for 

monitors such as variable valve timing systems, the denominator be incremented 

when, among other conditions, the component is commanded to function “on two or 

more occasions for greater than two seconds ... or for a cumulative time greater 

than or equal to 10 seconds, whichever occurs first.” Some of the manufacturers 

have requested that the condition regarding commanding the component to function 

“on two or more occasions” be deleted as it results in very few opportunities for this 

criterion to be satisfied without the other criterion also being satisfied and eliminating 

the former requirement would reduce the software complexity. Other 

manufacturers, however, requested they be given the option to use the criteria in the 

OBD II regulation (section 1968.2(d)(4.3.2)(F)) for engines that are utilized in 

medium-duty and heavy-duty vehicles. The OBD II criteria includes both of the 

aforementioned criteria originally proposed in the HD OBD language mentioned 

above. Staff agreed to these requests and is proposing changes to section 

1971.1(d)(4.3.2)(E) to reflect this. 

11. Section 1971.1(d)(4.3.2)(G): As part of the 45-day notice, staff proposed new criteria 

that must be met for incrementing in-use monitor performance denominators for 

components that experience infrequent regeneration events. Specifically, the 

monitor for these components would be required to increment the denominator 

when, among other conditions, 750 cumulative minutes of engine runtime had 

passed since the last time the denominator had incremented. Staff calculated this 

750-minute time based on discussions with industry about the expected 

regeneration frequency of particulate matter (PM) filters. Industry, however, has 

since requested that this 750-minute time not include engine runtime while the 

engine is idling, indicating that heavy-duty engines meeting California’s idling rule 

will have very little filter loading during idle, so including this idle time would not be 

critical and may result in more frequent incrementing of the denominator with less 

PM filter regeneration events. Staff, however, disagrees with this request which 

seems overly conservative but believes increasing the 750-minute time requirement 

to 800 minutes would address the idling concern. Additionally, staff did not specify 

when manufacturers were required to mandatorily use this 800 minute criterion and 

is proposing changes to correct this omission. Specifically, manufacturers would be 

allowed the option of using either the newly proposed 800 minute criterion or the old 
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criterion through the 2012 model year. Starting with the 2013 model year, 

manufacturers would be required to use the new criterion. Lastly, manufacturers 

expressed confusion as to when the denominator could be incremented relative to 

this engine run timer because the proposed language used a phrase of ‘at least 800 

minutes’ which led some to believe they could choose different values that were 

higher or lower than that specified in the regulation. Accordingly, staff rewrote the 

language to ensure that the denominator would be incremented as soon as all of the 

criteria have been met, including the 800 minute run time requirement. 

12. Section 1971.1(d)(4.3.2)(H): Staff is proposing modifications to this section similar to 

those being proposed in section 1968.2(d)(4.3.2)(I) of the OBD II regulation 

(described as item 3. under the modifications to section 1968.2 above). 

13. Section 1971.1(e)(2.2.4): Staff has added language in this section for the same 

reasons given in item 4. under the modifications to section 1968.2 above. 

14. Section 1971.1(f)(1.2.1): As part of the 45-day notice, staff proposed that, except as 

provided in section 1971.1(f)(1.2.6), manufacturers monitor for air-fuel ratio cylinder 

imbalance faults starting in the 2014 model year. A similar requirement already 

existed in the OBD II regulation. However, in section 1971.1(f)(1.2.6), staff 

mistakenly carried over language from the OBD II regulation related to a phase-in 

that explicitly requires vehicles equipped with separate exhaust gas recirculation 

(EGR) flow delivery passageways (that deliver EGR to individual cylinders) to 

monitor for these faults starting in a specific model year (proposed section). 

Because all 2014 and subsequent model year heavy-duty engines are required to 

monitor for cylinder imbalance faults, there is no analogous phase-in that would 

necessitate special handling for vehicles or engines with such EGR systems and the 

language in section 1971.1(f)(1.2.6) is not necessary. Thus, staff is now proposing 

to delete section 1971.1(f)(1.2.6) and to modify section 1971.1(f)(1.2.1) accordingly. 

 

15. Section 1971.1(f)(1.3.1): This section indicates which fuel system monitors are 

required to run continuously. Staff mistakenly omitted fuel system monitoring of 

adaptive feedback control and thus is proposing to correct this error. 

16. Section 1971.1(g)(3): Staff is proposing language (section 1971.1(g)(3.1.6)) to clarify 

the monitoring requirements for vehicle speed information if the information is used 

for another OBD monitor. Engine manufacturers have expressed concern about 

having to comprehensively monitor vehicle speed sensors that are located in the 

transmission since they have no control over components located outside the 

engine or of the diagnostics performed by other component suppliers on such 

sensors. Despite this lack of control, manufacturers have indicated that, historically, 

they have relied on such outside information and taken appropriate default action 

when the other components have been identified as faulty. Under the current 

requirements, such diagnostics would become part of the OBD system and subject 

to all of the OBD system requirements. Based on discussions between staff and 
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industry, a compromise was reached solely for vehicle speed information where 

engine manufacturers would monitor the vehicle speed information to the extent 

they can and the OBD system would additionally indicate a fault if the vehicle speed 

information was identified as faulty by diagnostics outside of the engine 

manufacturer’s OBD system (e.g., by the transmission supplier’s diagnostics). This 

proposed change would allow engine manufacturers to continue to follow their 

historical practice of using outside speed information to ensure engine and 

emission-related performance and have components that derive such information 

remain largely outside the scope of the OBD requirements. At the same time, the 

proposed modification would provide some level of protection that a fault of the 

vehicle speed information will be remedied in a timely manner to prevent continued 

disablement of other OBD system monitors. 

17. Section 1971.1(g)(5.6): Staff is proposing changes to this section regarding 

readiness handling during PTO device activation similar to those being proposed in 

section 1968.2(f)(17.6) of the OBD II regulation (described in item 6. under the 

modifications to section 1968.2 above). However, unlike the OBD II regulation 

where manufacturers can elect to use the existing or new readiness handling 

strategy, the proposed HD OBD language requires use of this alternate readiness 

handling strategy for 2013 and subsequent model years. Given the much more 

common expected usage of PTO devices in the heavy-duty market, the new 

strategy will be required in that it should provide inspectors and technicians with 

more accurate and useful information about the current state (and recent history) of 

the diagnostic system. 

18. Section 1971.1(h)(4.1): Given recent questions from several manufacturers, staff is 

proposing modifications to further clarify how readiness status is required to be 

implemented. In the past, monitors that are required to run continuously were 

typically excluded from readiness because they, by definition, run continuously and 

would be completed so quickly that waiting to set readiness status to complete 

would be negligible. However, several recently adopted monitoring requirements 

that were originally envisioned to run continuously have been revised to allow 

justified disablement in fairly common operating conditions. As such, the previous 

assumptions are not valid as these monitors can indeed be disabled for substantial 

periods of engine operation and waiting for them to run before setting readiness 

would not be a negligible period of time. Thus, staff is proposing additional 

language that more precisely specifies which monitors (e.g., circuit/out-of-range 

monitors, feedback control monitors) can be excluded from the determination of 

readiness status. Additionally, the original language indicated that the readiness 

status for the gasoline fuel system monitor should always indicate “complete,” since 

prior to the 45-day notice, all monitors under the fuel system monitoring 

requirements were required to run continuously. However, with the recently 

proposed inclusion of the gasoline fuel system monitoring requirement for air-fuel 

ratio cylinder imbalance faults, which are not required to run continuously, staff is 

proposing to have the readiness status for the fuel system set to “complete” only 
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when the cylinder imbalance monitor has run and completed and have changed the 

language accordingly. As this cylinder imbalance monitoring requirement is not 

required until the 2014 model year, sufficient lead time is already being provided to 

ensure compliance with the proposed changes to the readiness handling 

requirement. 

 

19. Section 1971.1(h)(4.5.7): This section indicates which specific monitors are not 

required to meet the standardized test results requirements. Staff mistakenly 

omitted feedback monitors for diesel exhaust gas sensors and is proposing 

language to address this. 

Modifications to HD OBD Enforcement Regulation (section 1971.5) 

20. Section 1971.5(d)(2): Upon receiving word from the Executive Officer that an engine 

class has a non-conforming OBD system, the manufacturer may “within 45 days 

from the date of service of such notification, elect to conduct an influenced OBDrelated recall” and “shall submit an influenced OBD-related recall plan for approval.” 

 Manufacturers have interpreted this language to mean that they would have 45 

days to both elect to conduct an influenced recall and to submit a plan for approval, 

which was not staff’s intention. Thus, staff is proposing revisions to the regulation to 

indicate that, upon election by the manufacturer to conduct a recall within 45 days of 

receiving the notice, manufacturers would have an additional 45 days to submit the 

recall plan for approval. 

Other Minor Modifications 

21. In addition to the modifications described above, staff is proposing various 

nonsubstantive modifications to the regulatory text in sections 1968.2, 1971.1, and 

1971.5 to improve clarity and to correct errors that have found by staff and industry. 

Additional Document Added to the Record

In the interest of completeness, staff has also added to the rulemaking record and 

invites comments on ARB Mail-Out MSC#09-22, “Guidelines for Heavy-Duty On-Board 

Diagnostic (HD OBD) Certification Data,” July 7, 2009. ARB staff proposed 

modifications to a few sections in section 1971.1 to reference this document. This 

document is available at the following ARB websites: 

http://www.arb.ca.gov/msprog/obdprog/obdupdates.htm

and 

http://www.arb.ca.gov/msprog/mailouts/msc0922/msc0922.pdf

Written comments will only be accepted on the modifications to the originally proposed 

regulatory text approved by the Board and set forth in Attachment I, and the additional 
9

document that was added to the record. The written comments may be submitted by 

postal mail or electronic mail submittal as follows: 

Postal mail: Clerk of the Board, Air Resources Board 

1001 I Street, Sacramento, California 95814 

Electronic submittal: http://www.arb.ca.gov/lispub/comm/bclist.php 

Please note that under the California Public Records Act (Gov. Code § 6250 et seq.), 

your written and oral comments, attachments, and associated contact information (e.g., 

your address, phone, email, etc.) become part of the public record and can be released 

to the public upon request. Additionally, this information may become available via 

Google, Yahoo, and any other search engines. 

In order to be considered by the Executive Officer, comments must be directed to ARB 

in one of the two forms described above and received by the ARB by 5:00 p.m., on the 

deadline date for public comment listed at the beginning of this notice. Only comments 

relating to the above-described modifications to the text of the regulations shall be 

considered by the Executive Officer. 

For individuals with sensory disabilities, this document and other related material can be 

made available in Braille, large print, audiocassette, or computer disk. For assistance, 

please contact the Clerk of the Board at (916) 322-5594 as soon as possible. 

Attachments 

The energy challenge facing California is real. Every Californian needs to take immediate action to reduce energy 

consumption. For a list of simple ways you can reduce demand and cut your energy costs, see our website at 

www.arb.ca.gov.