1

State of California

AIR RESOURCES BOARD

Final Statement of Reasons for Rulemaking,

Including Summary of Comments and Agency Response

PUBLIC HEARING TO CONSIDER TECHNICAL STATUS AND PROPOSED 

REVISIONS TO ON-BOARD DIAGNOSTIC SYSTEM REQUIREMENTS FOR 

HEAVY-DUTY ENGINES, PASSENGER CARS, LIGHT-DUTY TRUCKS, MEDIUMDUTY VEHICLES AND ENGINES

Public Hearing Date: August 23, 2012

Agenda Item No.: 12-5-2

 I. GENERAL

The Staff Report: Initial Statement of Reasons for Rulemaking (Staff Report), 

entitled “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)”,

released July 5, 2012, is incorporated by reference herein. 

In this rulemaking, the Air Resources Board (ARB or Board) approved the 

adoption of amendments that primarily modify the monitoring and 

performance requirements of OBD II systems in diesel fueled medium-duty 

vehicles, the monitoring and performance requirements of HD OBD systems, 

and the enforcement provisions applicable to OBD II systems and HD OBD 

systems. 

On July 5, 2012, ARB published a notice for an August 23, 2012 public 

hearing to consider the proposed regulatory action. The Staff Report was 

also made available for public review and comment beginning July 5, 2012. 

The Staff Report provides the rationale for the proposed amendments. The 

text of the proposed amendment to title 13, California Code of Regulations 

(CCR), sections 1968.2, 1968.5, 1971.1, and 1971.5 was included in 

Appendices to the Staff Report. These documents were also posted on 

ARB’s website for the rulemaking 

at http://www.arb.ca.gov/regact/2012/hdobd12/hdobd12.htm.

On August 23, 2012, the Board conducted a public hearing and received oral 

and written comments. At the conclusion of the hearing, the Board adopted 

Resolution 12-29 that covered the proposed amendments to title 13, CCR 

sections 1968.2, 1968.5, 1971.1, and 1971.5 that were initially proposed by 

staff and described in the Notice of Public Hearing (45-Day Public Notice) and 

Staff Report, along with modifications suggested by staff in a document 

entitled “Staff’s Suggested Modifications to the Original Proposal” 

Amendments” that was distributed at the hearing and that was Attachment E

to the Resolution. 
2

The modifications were made in response to comments received after the 

Staff Report was published on July 5, 2012, as part of the 45-day notice. 

These modifications include changes to the required monitoring conditions for 

the diesel misfire monitor requirements in the HD OBD and OBD II 

regulations, clarifications to the readiness status and test results requirements 

in the HD OBD regulation, deletion of the service information requirements in 

the HD OBD regulation, clarifications to the definition of “emission standard” 

in the HD OBD and OBD II regulations, and various changes to correct errors 

and improve clarity. 

In accordance with Government Code section 11346.8, Resolution 12-29

directed the Executive Officer to adopt the proposed amendments to title 13, 

CCR sections 1968.2, 1968.5, 1971.1, and 1971.5 as proposed by staff and 

as modified in accordance with Attachment E to Resolution 12-29, to 

determine if additional modifications to the originally proposed amendments 

were appropriate, and if the Executive Officer so determined, to make the 

modified regulatory language available for public comment for a period of at 

least 15 days before taking final action to adopt the amendments. The 

Executive Officer was also directed to consider such written comments that 

were submitted during the public comment period, to make such modifications 

as may be appropriate in light of the comments received, or to present the 

amendments to the Board for further consideration if warranted in light of the 

comments.

Subsequent to the August 23, 2012 public hearing, staff proposed

modifications to the originally proposed amendments to title 13, CCR sections 

1968.2, 1968.5, 1971.1, and 1971.5. The text of the proposed modifications 

to the originally proposed amendments, and additional supporting documents 

were made available for a supplemental 15-day comment period by issuance 

of a “Notice of Public Availability of Modified Text.” This Notice and the 

attachments thereto were mailed on January 4, 2013 to all stakeholders, 

interested parties, and to other persons generally interested in ARB’s 

rulemaking requirements applicable to OBD II and HD OBD systems. The 

“Notice of Public Availability of Modified Text” listed the ARB website from 

which interested parties could obtain the complete text of the regulations that 

would be affected by the modifications to the original proposal, with all of the 

modifications clearly indicated, and the additional supporting documents. 

These documents were also published on ARB’s website for this rulemaking

http://www.arb.ca.gov/regact/2012/hdobd12/hdobd12.htm. Descriptions of 

and rationales for the modifications were provided in the attachment to the 

15-Day Notice. The 15-Day Notice is incorporated by reference herein. Six 

written comments were received during this 15-day comment period.
3

Staff additionally made a few minor modifications in the regulatory text after 

the close of the 15-day comment period to correct typographical errors.

After considering the comments received during the 15-day comment period, 

the Executive Officer issued Executive Order R-13-005, adopting 

amendments to title 13, CCR sections 1968.2, 1968.5, 1971.1, and 1971.5. 

This Final Statement of Reasons (FSOR) updates the Staff Report by 

identifying and providing the rationale for the modifications made to the 

originally proposed regulatory text, including non-substantial modifications

and clarifications made after the close of the 15-day comment period. This 

FSOR also contains a summary of the comments received by the Board on 

the proposed amendments and the modifications and ARB’s responses to 

those comments.

In the 45-Day Notice for this rulemaking, the ARB referenced a few new 

Society of Automotive Engineers (SAE) documents and updated several SAE 

and International Organization of Standards (ISO) documents that would be 

incorporated by reference in sections 1968.2 and 1971.1. The new and 

updated SAE and ISO documents that are incorporated by reference in the 

regulations are: 

ISO 15765-4:“Road Vehicles – Diagnostics Communications over 

Controller Area Network (CAN) – Part 4: Requirements for emissionrelated systems,” February 2011.

SAE J1699-3 – “Vehicle OBD II Compliance Test Cases”, December 

2009.

SAE J1930-DA “Electrical/Electronic Systems Diagnostic Terms, 

Definitions, Abbreviations, and Acronyms Web Tool Spreadsheet”, March 

2012.

SAE J1979 "E/E Diagnostic Test Modes," February 2012.

SAE J1979-DA “Digital Annex of E/E Diagnostic Test Modes”, October 

2011.

SAE J2012-DA “Digital Annex of Diagnostic Trouble Code Definitions and 

Failure Type Byte Definitions”, July 2010.

SAE J2403 “Medium/Heavy-Duty E/E Systems Diagnosis Nomenclature,” 

February 2011.

SAE J1939 consisting of:

J1939 Recommended Practice for a Serial Control and Communications 

Vehicle Network, April 2011;

J1939/01 On-Highway Equipment Control and Communications Network, 

May 2011;
4

J1939/13 Off-Board Diagnostic Connector, October 2011;

J1939/21 Data Link Layer, December 2010;

J1939/31 Network Layer, May 2010;

J1939/71 Vehicle Application Layer (Through May 2010), March 2011;

J1939/73 Application Layer—Diagnostics, February 2010;

J1939/81 Network Management, June 2011; and

J1939/84 OBD Communications Compliance Test Cases For Heavy Duty 

Components and Vehicles, December 2010.

Additionally, the following document has been incorporated by reference in 

section 1971.1:

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

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

Existing administrative practice of ARB has been to have technical 

recommended practices, such as the documents listed above, incorporated 

by reference rather than printed in the CCR. These documents are referenced 

and incorporated into the California Code of Regulations because it would be 

cumbersome, unduly expensive, and otherwise impractical to publish them in 

the Code. Existing ARB administrative practice has been to have 

specifications, test procedures, and similar documents incorporated by

reference rather than printed in the CCR because these procedures are 

highly complex technical documents. Because ARB has never printed these 

types of documents in the CCR, the affected public is accustomed to the 

incorporation format utilized in sections 1968.2 and 1971.1. Moreover, 

printing portions of the documents in the CCR when the bulk of the 

procedures are incorporated by reference would be unnecessarily confusing 

to the affected public. Additionally, the documents from SAE and ISO are 

copyrighted and are available only for purchase on the organizations’ 

websites. The full documents are instead available for public inspection from 

the Clerk of the Board at 1001 I Street, 23rd floor, Sacramento, California 

95814. 

Fiscal Impacts of Proposed Changes 

Pursuant to Government Code sections 11346.5(a)(5) and 11346.5(a)(6), the

Executive Officer has prepared an estimate in accordance with instructions 

adopted by the Department of Finance, and determined that the regulatory 

action would not create overall costs or savings to any state agency or in 

federal funding to the state, costs or mandate to any local agency or school 

district whether or not reimbursable by the state pursuant to part 7 

(commencing with section 17500), division 4, title 2 of the Government Code, 

or other nondiscretionary cost or savings to state or local agencies.
5

The Board has also determined, pursuant to CCR, title 1, section 4, that the 

proposed regulatory action may affect small businesses. The Board 

estimates that there nine alternate-fueled conversion manufacturers, some of 

which may be considered “small businesses”, although the exact number 

cannot be determined. One of these manufacturers is located in California. A 

typical small business alternate-fueled engine conversion manufacturer 

converts up to 500 diesel or gasoline engines per year to run on alternate 

fuels. An analysis was conducted that estimates the total incremental cost of 

the proposed amendments on such a small business at $228 per vehicle. 

Such small businesses are expected to pass these costs onto the purchaser 

of the engine in the form of increased retail price for the converted engine.

Consideration of Alternatives 

For the reasons stated in the Staff Report and the Board’s response to 

comments in this FSOR, the Board has further determined that no alternative 

considered by the agency or brought to the attention of the agency would be 

more effective in carrying out the purpose for which the regulatory action was 

proposed or would be as effective and less burdensome to affected private 

persons than the action taken by the Board.

 II. SUMMARY OF COMMENTS AND AGENCY RESPONSES

At the August 23, 2012 hearing, ARB received written comments and/or oral 

testimony from:

Ms. Lisa Stegink, Truck and Engine Manufacturer’s Association (EMA)

Mr. Mark Stepper, Cummins Inc. (Cummins)

Dr. Rasto Brezny, Manufacturers of Emission Controls Association (MECA)

Mr. Christopher C. Jones, BAE Systems (BAE) 

Mr. Yisheng Zhang, Parker Hannifin Corporation (PH)

Written comments in response to the 45-Day Notice were received during the 

45-day comment period prior to the hearing from: 

Mr. Joseph Kubsh, MECA

Mr. Jed R. Mandel and Ms. Lisa A. Stegink, EMA

Mr. Stephen J. Trichka, BAE

Mr. Markus Richter, Mercedes Benz (Mercedes)

Ms. Laurie B. Tuttle, Allison Transmission Inc. (Allison)

Ms. Julie Becker, Alliance of Automobile Manufacturers (Alliance)

Written comments in response to the 15-Day Changes were received during 

the 15-day comment period from:

Mr. Joseph Policarpio, GILLIG LLC (GILLIG)

Mr. James Wilhelm, Santa Clara Valley Transportation Authority (VTA)

Ms. Lisa A. Stegink and Mr. Timothy A. French, EMA
6

Daimler Trucks North America LLC (DTNA)

A written comment was received from Mr. Ashim Manchanda of Mercedes, 

but it was identical to a comment submitted by Mercedes during the 45-day 

comment period and did not pertain to any of the 15-day changes.

Another written comment was received from an individual, but that comment 

consisted of a sales pitch and did not pertain to any of the 15-day changes.

Set forth below is a summary of each comment regarding the regulatory 

action and the agency response to that comment, including an explanation of 

how the regulation was changed to accommodate the comment or the 

reason(s) for not making a change to the regulation. Comments not involving 

objections or recommendations specifically directed toward this rulemaking or 

to the procedures followed by ARB in this rulemaking are not included. The 

comments have been grouped by topic wherever possible. 

45-DAY COMMENTS

COMMENTS IN SUPPORT

1. Comment: We support the proposal, specifically the in-use monitoring 

performance requirements for the catalysts, PM filter and PM sensor and 

the revisions to the PM filter, NOx sensor, and NOx catalyst monitor 

thresholds for the 2013 through 2015 model years, since it will better align 

the OBD requirements with the state of development of sensors (NOx and 

PM) integral to OBD systems. We support the proposed delay and higher 

NOx thresholds for the NOx catalyst on medium-duty and heavy-duty 

engines during the 2013 to 2015 timeframe. Though NOx sensor 

technology has advanced significantly over the years to the level of 

accuracy today (+/-10% or +/-10ppm), the additional time will allow engine 

manufacturers to better integrate and optimize their NOx catalyst 

monitors. We agree with the proposed +0.2 g/bhp-hr NOx threshold in 

2017. We agree with requiring identical thresholds for the NOx sensor 

and NOx catalyst monitors. (MECA)

2. Comment: MECA is also working with customers to be fully integrated with 

PM sensors, which are not yet commercially available across all 

manufacturers, by the 2015 time frame. We therefore support the 

threshold revisions and PM sensor failure mode flexibilities to better match 

the capabilities of current monitoring technologies while providing more 

time for full implementation of PM sensors and sensor monitoring out to 

2016 for medium- and heavy-duty engines. It is reasonable to provide 

flexibilities to vehicles that implement tighter PM monitoring limits in 2014 

and 2015 to fully implement the final thresholds in 2017. (MECA)
7

3. Comment: We support the proposed delay of nitrogen oxide feedgas 

monitoring for oxidation catalysts and catalyzed PM filters and NMHC 

conversion monitoring for catalyzed PM filters, which will align the heavyduty requirements with the medium-duty requirements that were recently 

implemented. (MECA)

4. Comment: We support requiring evaporative system monitors on heavyduty LPG engines in the 2018 timeframe, since evaporative system 

monitoring is an established technology on light-duty gasoline vehicles 

and can easily be integrated on these heavy-duty alternate fueled 

engines. (MECA)

5. Comment: We believe that this proposal achieves the right balance 

between technically achievable monitoring thresholds and timelines that 

stimulate sensor technology development to achieve the objectives of the 

regulation and insure that catalysts and filters are delivering the necessary 

emission performance over their full useful life and beyond. (MECA)

6. Comment: EMA supports allowing a three-year phase-in for continuous 

misfire monitoring in the OBD II and HD OBD regulations, since it is 

essential to addressing manufacturers’ concerns about their abilities to 

achieve repeatable and representative misfire detection. (EMA)

7. Comment: EMA supports the proposed test-out provisions for the PM filter 

NMHC conversion efficiency monitoring requirement, the diesel oxidation 

catalyst (DOC) feedgas monitoring requirement, and the fuel injector 

tolerance compensation factor monitoring requirement. (EMA)

8. Comment: EMA supports ARB staff’s policy stated in the Staff Report that 

the deficiency “clock” would be reset if the required monitor emission 

threshold is changed. (EMA)

Agency Response to Comments 1-8: We appreciate the comments. 

DEFINITION OF “EMISSION STANDARD”

9. Comment: In light of the Superior Court’s ruling in Engine Mfrs Ass’n v. 

California Air Resources Board, No. 2010-00082774-CU-MU (EMA v. 

ARB) finding the HD OBD provisions requiring manufacturers to conduct 

in-use self-testing of engines and to order recall to be invalid, ARB must 

recognize the invalidation of those provisions before attempting any 

further amendments to the program. Indeed, as detailed below, ARB is 

seeking to amend recall provisions that have been expressly ruled to be 

invalid and of no effect. Any such attempted amendment is necessarily 

invalid and of no effect as well. Accordingly, before proceeding further 

with any of the proposed amendments at issue in this iteration of 

rulemaking, ARB needs to take specific account of all of the prior 

amendments that have been determined to be unlawful and invalid. Not 

doing so will only spawn additional litigation, judicial mandates and 
8

sanctions that should otherwise be unnecessary if ARB simply abides by 

the pending order of the Superior Court. (EMA)

Agency Response: Please see Agency Response to Comment 56 below. 

ARB has appealed the decision of the lower court, and the appellate court 

will review that decision de novo. EMA has never sought to enjoin nor has 

any court granted an injunction or stay requiring ARB to immediately 

amend its regulations as EMA requests while ARB’s appeal is pending 

review. 

10.Comment: One of the series of revisions that ARB staff have proposed to 

the HD OBD rule and to the OBD II rule is the addition of a newly-minted 

definition of the term “emission standard.” ARB staff have proposed to 

add this definition to the regulations presumably so that ARB can try to 

bolster its claim (i) that the OBD malfunction criteria are emission 

standards, and (ii) that failures to satisfy the OBD malfunction criteria 

amount to violations of emission standards, which in turn can lawfully 

allow ARB to insist on an engine recall under Health and Safety Code 

(HSC) §43105. 

As an initial matter, it seems apparent that ARB staff formulated and 

inserted their proposed definition prior to the issuance of the final 

judgment by the California Superior Court on July 18, 2012, in EMA v. 

ARB. In that case, as noted above, the Superior Court ruled that the 

manufacturer-run in-use testing provisions of the HD OBD regulations, as 

well as the mandatory recall provisions (see CCR, title 13, sections 

1971.1(l)(4), 1971.5(c), 1971.5(d)(l)-(4) and (6)-(7), 1971.5(e) and 

1971.5(f)), are not within the scope of ARB’s authority and so are invalid. 

Thus, the proposed regulatory revisions at issue have, in effect, been 

superseded and mooted by the recent decision of the California Superior 

Court. The OBD-related in-use testing and recall provisions that ARB 

seeks to amend have been judicially determined to be in excess of ARB’s 

statutory authority and, therefore, invalid. Simply stated, ARB is seeking to 

amend an in-use testing and recall program that is invalid and of no effect. 

As a consequence, the amendments at issue are inherently invalid as 

well. ARB cannot revise or amend regulations that have been struck 

down. (EMA)

Agency Response: Please see Agency Response to Comments 9 and 56. 

While continuing to reserve all arguments raised in the lower court that 

ARB has authority to adopt HD OBD enforcement procedures, ARB 

determined that the most prudent action would be for it to amend the 

regulation expeditiously to cure the perceived defects identified by the 

lower court regarding ARB’s authority and to make it clear to all regulated 

stakeholders as expeditiously as possible that OBD systems are emission 

standards and fully enforceable under California law. To wait in the
9

expectation of the appellate court overturning the lower court’s decision, 

ARB would unnecessarily risk that manufacturers would slip in their 

compliance believing that ARB had no enforcement authority. This would 

potentially undermine the purposes and intent of the OBD regulations and 

would result in potential lost emission reductions, with consequential 

adverse effects to the public’s health and welfare.

To avoid this potential outcome, ARB took such action to clarify its 

authority by revising the definition of emission standard to conform to the 

decisional law interpretation of that term as used in Title II of the federal 

Clean Air Act (CAA) pursuant to HSC sections 39010 and 39601(b). ARB 

was not precluded from taking such action as EMA has not pursued, and 

no court has granted, any injunction prohibiting ARB from attempting to 

cure any perceived defects. Regarding EMA’s claims of definitional 

gymnastics, the definition adopted by the Board, as stated, fully conforms 

to the Supreme Court’s interpretation of the meaning of emission standard 

as used by Congress in Title II of the CAA. EMA v. SCAQMD (2004) 541 

U.S. 246, 253 [“This interpretation is consistent with the use of ‘standard’ 

throughout Title II of the CAA (which governs emissions from moving 

sources)....” ]. Finally, ARB timely filed its notice of the proposed 

amendment to the definition of emission standard and does not 

understand the relevance of the comment that ARB staff formulated and 

inserted their proposed definition prior to the issuance of the final 

judgment.

11.Comment: Even if the proposed revisions were not mooted by the 

Superior Court’s recent decision, it is clear that OBD malfunction criteria 

are not emission standards, under either federal law or California law. 

Thus, as explained below, the recent determination of the California 

Superior Court -- that “a malfunction criterion is not an emission standard” 

-- remains the binding and correct conclusion. ARB asserts that it is 

entitled to change the operative definition of “emission standard” pursuant 

to HSC section 39601(b). (See ISOR, p.61.) That section, in relevant part, 

authorizes ARB to revise certain definitions of terms “in order to conform 

those definitions to federal laws and rules and regulations.” But ARB’s 

new definition of “emission standard” does not conform to the federal 

definition of “emission standard.” Rather, it amounts to a transparent and 

invalid effort to end-run the Superior Court’s recent decision. (EMA)

12.Comment: ARB’s goal to conform to the federal definition “applied to 

Title II by the U.S. Supreme Court in EMA vs. SCAQMD is misplaced, 

since the Supreme Court was not interpreting the term “emission 

standard” in Title II but was interpreting the meaning of section 209(a), 

which preempts states from adopting or attempting to enforce “any 

standard relating to the control of emissions from new motor vehicles or 

new motor vehicle engines.” SCAQMD, 541 U.S. at 251. The phrase the 

Court interpreted – “any standard relating to the control of emissions” – is 

more expansive than “emission standard.” 
10

The question before the SCAQMD Court was whether rules imposing 

emission-related purchase requirements on owners of vehicle fleets in the 

South Coast were “standards related to the control of emissions” and thus 

preempted. Starting with the dictionary definition of “standard”, the Court 

concluded that the requirements were preempted under Section 209(a) 

but did not say they were “emission standards” (which would be 

counterintuitive) since the term “emission standard” was not before the 

Court. The Section 209(a) preemption provision is broad to preclude 

states from adopting their own emission-related requirements to avoid 

balkanizing the regulation of the design of new motor vehicles across the 

country, and presumably precludes states from adopting their own OBD 

requirements as a preempted “standard relating to the control of 

emissions.” An acknowledgment that OBD requirements might “relate” to 

emissions does not mean they are “emission standards” under federal law 

or that ARB can legally redefine “emission standard” to include any 

“design feature related to emissions.” (Alliance)

Agency Response to Comments 11 and 12: Please see Agency 

Responses to Comments 9, 10, and 56. ARB’s authority to revise the 

statutory definition of “emission standard” (codified at HSC section 39027) 

is set forth at HSC sections 39010 and 39601(b), which provides that ARB 

may revise certain definitions of terms set forth in Chapter 2 of the HSC 

(commencing with section 39010 in order “to conform those definitions to 

federal laws and rules and regulations.”) Consistent with the discretion 

delegated to ARB by the Legislature, ARB has determined that a revised 

definition of “emission standard,” which conforms to the definition 

expounded by the Supreme Court in EMA v. SCAQMD, supra., 541 U.S. 

at 253, is both prudent and within ARB’s legal authority. ARB must have 

authority to fully enforce its HD OBD regulation – a regulation that EMA 

does not challenge as outside of ARB’s authority – to ensure that 

significant emission reductions will be achieved from the newest, most 

stringent heavy-duty engine emission standards and that emission control 

systems on those engines are durable and reliable. While ARB’s authority 

to enforce its OBD regulation fully has recently been called into question 

by the California Superior Court decision in EMA v. ARB, that decision is 

now on appeal. As stated, EMA has not requested that ARB be enjoined 

from attempting to cure the defects found by the lower court, and no court 

has issued an injunction or stay. Without conceding any arguments 

before the Court of Appeal that ARB has authority to enforce its 

regulations, ARB has every right to act preemptively and prudently to 

make certain that its regulations are enforceable and that it can fully meet 

the tasked mission and goals of the agency as prescribed by the 

Legislature. 

The amended definition of emission standard conforms to the decisional 

law of the Supreme Court in EMA v. SCAQMD. There the Court was 

specifically confronted with the question of what is a standard related to 

the control of emissions and concluded that it relates to the amount of a 

given pollutant that a vehicle may emit, or a requirement that a vehicle 
11

must be equipped with a certain type of pollution-control device or some 

other design feature related to the control of emissions. EMA v. 

SCAQMD, supra, 541 U.S. at 253. The Court found that its interpretive 

definition was consistent with the use of the term used throughout Title II

of the CAA and specifically its use in section 202, the section of the CAA 

that specifically addresses EPA’s authority to adopt motor vehicle 

emission standards. OBD system requirements require that the emission 

system not emit more than a certain amount of a given pollutant and 

includes design features related to the control of emissions. It is not 

insignificant that EPA’s authority to adopt OBD standards is set forth at 

section 202(m) and that EPA has specifically found OBD requirements to 

be emission standards. See 61 Fed.Reg. 53371 (Oct. 11, 1996). 

EMA itself has long recognized that OBD requirements are emission 

standards under both California and federal law. In the 2009 HD OBD 

rulemaking, EMA commented:

Many of the proposed HD OBD amendments constitute new 

emission standards that engine manufacturers must meet before 

selling their products. Thus, the standards are subject to clear 

mandates by the U.S. Congress in the federal CAA and by 

California legislature in state law. As required by CAA Section 

209(b), any mobile source emission standards adopted by ARB for 

on-highway engines and vehicles from over 8,500 lbs. require a 

waiver of federal preemption from U.S. EPA, must be 

technologically feasible and cost-effective, and may be 

implemented only if the requisite lead time and period of stability 

are provided to manufacturers (according to CAA Section 202(a)). 

If ARB’s standards don’t meet these requirements, California 

cannot obtain the necessary preemption waiver from EPA. 

(Emphasis added.)

(See 2009 FSOR, Comment 16, page 9, as well as FSORs for 2004 

Engine Manufacturer Diagnostic rulemaking in 2004, 2005 HD OBD 

rulemaking, and 2006 OBD II rulemaking.) In so concluding that OBD 

requirements are emission standards, EMA specifically relied upon not 

only the use of the term “standard related to the control of emissions” as 

used in CAA section 209(b), but also the term standard as used in section 

202(a)(3)(C). For discussion of why the lead time and stability 

requirements of section 202(a)(3)(C) do not apply to OBD emission 

standards, see Agency Response to Comment 22.

The ARB did not propose that the redefined definition of “emission 

standard” apply solely to the HD OBD regulation. Concurrent with the HD 

OBD amendments, ARB amended the definition of emission standard as 

used in OBD II. The definition was in the first instance added to these 

regulations because (1) it had long been planned that ARB would be 

amending these regulations in 2012, and (2) because stakeholders had 

raised specific questions about whether ARB had authority to fully enforce 
12

and remedy noncompliant OBD systems, which they believed could not be 

considered emission standards. It is ARB’s staff’s intent, in the very near 

future, to propose that the Board apply the broader EMA v. SCAQMD

definition to other motor vehicle regulations. 

13.Comment: The federal definition of “emission standard” is found at 

section 302(k) of the CAA. That provision of federal law states in relevant 

part that the terms “emission limitations” and “emission standard” mean a 

requirement established by the State [of California] or the Administrator [of 

EPA] which limits the quantity, rate, or concentration of emissions of air 

pollutants on a continuous basis... (42 U.S.C. §7602(k).) Plainly, ARB’s 

proposed amended definition of “emission standard” does not at all 

conform to CAA section 302(k) and so is not authorized under HSC 

section 39601(b). As a result, the Board is not authorized to approve the 

proposed amended definition of “emission standard.” 

In an implicit concession that its definitional gamesmanship does not 

conform with CAA section 302(k), ARB does not even mention the 

controlling federal definition of “emission standard,” but instead asserts 

that its proposed redefinition of the term is consistent with the Supreme 

Court’s ruling in EMA v. SCAQMD, 541 U.S. 246 (2004). In that case, 

however, the Court was called upon to interpret the scope of federal 

preemption under CAA section 209(a), not the definition of “emission 

standard” under CAA section 302(k). The scope of federal preemption 

encompasses “any standard relating to the control of emissions.” See 42 

U.S.C. §7543(a). It is, therefore, broader in scope than the specific 

statutory definition of the term “emission standard.” More fundamentally, 

the Supreme Court’s elucidation of the scope of federal preemption cannot 

form the basis for ARB’s attempt to redefine the term “emission standard.” 

That redefinition, if it is to be valid under HSC section 39601(b), must be 

premised on CAA section 302(k), not case law interpreting other 

provisions of the CAA. Thus, ARB’s purported reliance on the Supreme 

Court’s 2004 preemption decision is entirely misplaced and unavailing. 

With reference to the actually relevant terms of CAA Section 302(k), an 

OBD malfunction criterion or threshold is not a numerical tailpipe limit on 

the “quantity, rate or concentration of emissions of air pollutants” with 

which an engine or vehicle must comply. Rather, it is a durability or 

reliability standard that an OBD system component must meet so that it 

consistently activates a malfunction indicator light (MIL) when warranted. 

Consequently, it is clear that the federal definition of the term “emission 

standard” does not encompass an OBD malfunction criterion. As a result, 

ARB’s latest attempt to disguise OBD malfunction criteria as “emission 

standards” (as opposed to performance specifications for OBD 

components) remains in violation of state and federal law. (EMA)

Agency Response: Please see Agency Responses to Comments 9-12

and 56. As stated, the Supreme Court fully considered and addressed the 

meaning of “any standard relating to the control of emissions of motor 
13

vehicles” (i.e., emission standard), and found the term as interpreted to be 

consistent with Congress’ use of the term throughout Title II of the CAA in 

EMA v. SCAQMD. The definition of the term was central at the Court’s 

decision. In so interpreting the term, the Court found that it was either not 

appropriate or not necessary to address the applicability of CAA section 

302(k) in the context of Title II. 

14.Comment: The Board must direct Staff to publish modified regulatory 

language deleting the proposed definitions of “emission standard,” 

“evaporative emission standards,” and “exhaust emission standards or 

tailpipe emission standards” from the HD OBD rule and from the OBD II 

rule. The Board must direct staff to delete the other sections of the HD 

OBD rule that have been invalidated by the Superior Court of California. 

(EMA) 

Agency Response: For the reasons set forth in Response to Comment 9,

ARB is under no legal obligation to delete the proposed definitions of 

“emission standard,” “evaporative emission standards,” and “exhaust 

emission standards or tailpipe emission standards” from the HD OBD and 

OBD II rules.

15.Comment: OBD requirements are not emission standards and ARB may 

not legally define OBD as such to justify recall under Health and Safety 

Code section 43105. We are concerned about the new definitions of 

“emission standard,” “evaporative emission standards,” and “exhaust 

emission standards or tailpipe emission standards” in the light-duty OBD II 

regulation. ARB acknowledges the new definition is in response to 

stakeholders’ arguments that OBD system requirements do not constitute 

emission standards and that ARB thus may not order a recall based on 

only on exceedance of the applicable emission limits. EMA recently 

prevailed in challenging the mandatory recall requirements under the 

heavy-duty OBD rule on the grounds that OBD malfunction criteria do not 

constitute emission standards (EMA v. ARB). The court ruled that a 

“nonconforming OBD system” defined in the ARB regulations “irrespective 

of whether engines in the engine class, on average, meet applicable 

tailpipe or evaporative emission standards,” does not qualify as an 

“emission standard” as defined in HSC Section 39027 (i.e., “the specified 

limitation on discharge of air contaminants into the atmosphere”). The 

court reasoned that the determination that a vehicle or engine contains a 

nonconforming OBD system may have no relation to the existence of 

excess emissions affecting the environment or attainment of air quality 

standards. 

ARB’s new definition of “emission standard” is meant to displace the 

existing definition in the HSC, but the Alliance believes this is both 

unauthorized and inadequate. ARB has no authority to displace the 

section 39027 “emission standard” definition. While ARB says they are 

allowed under HSC Section 39601(b) to conform the definition with that of 

the federal EPA, neither the CAA nor U.S. EPA’s regulations define 
14

“’emission standard’ as it applies to OBD compliance. Moreover, neither 

the U.S. Code nor the Code of Federal Regulations contains a federal 

definition that includes “some other design feature related to the control of 

emissions.” (Alliance)

Agency Response: Please see Agency Responses to Comments 9-12

and 56. The commenter misstates ARB’s position. It is conforming the 

definition of emission standard to the decisional law of the U.S. Supreme 

Court interpreting use of the term in the Clean Air Act, not to any specific 

definition adopted by EPA. Indeed, the Supreme Court’s decision 

interpreting the meaning of emission standard is fully consistent with the 

position taken by the American Automobile Manufacturers Association 

(AAMA) – which at the time represented American automobile 

manufacturers and preceded the Alliance as the association representing 

those manufacturers – in the initial OBD II waiver proceedings before 

EPA. In a letter dated December 1, 1995, the automobile manufacturers 

stated:

“Requirements for OBD systems are emission control standards 

under §202 of the Clean Air Act. Congress’ decision to include 

such requirements in the emission standards section of the Act 

(Section 202) is a clear indication of its intent that OBD 

requirements are to be considered emission control standards. This 

intent is confirmed by the relationship between §§ 202(a) and 

202(m). Section 202(m) of the Act specifically requires the Agency 

to promulgate OBD regulations under § 202(a).” 

AAMA letter to EPA, Attachment I, page 2. 

16.Comment: In the EMA v. ARB case, ARB sought to rely on a 1996 EPA 

decision waiving federal preemption under Section 209(a), where EPA 

considered whether certain California OBD requirements were “standards 

relating to emissions” subject to preemption under Section 209(a) and 

thus requiring a preemption waiver under Section 209(b). ARB took the 

position that OBD requirements were enforcement procedures rather than 

standards relating to emissions (1996 waiver decision at 19-20). EPA 

emphasized that the classification of the OBD requirements was “as a 

standard for purposes of section 209” (1996 decision at 20). So like the 

SCAQMD case, the EPA waiver decision interpreted the scope of Section 

209(a) preemption, not that OBD requirements are “emission standards.” 

OBD requirements are not “emission standards,” under the existing 

California statutory definition, any CAA definition that ARB is authorized to 

adopt, or any common sense definition. The existing emission standard 

definition in HSC section 39027 does not conflict with the CAA or its 

underlying regulations. The Superior Court in EMA v. ARB ruled that OBD 

requirements are not limitations on the discharge of air contaminants into 

the atmosphere. The CAA imposes other emission monitoring 

requirements such as those on stationary sources (e.g., continuous 
15

emissions monitoring system in a smokestack), but it’s common sense 

that such a device is used to monitor compliance with emissions 

standards and the monitoring requirements is not an emissions standard 

itself. EPA’s mobile source regulations do not define “emission standard” 

to include OBD. (Alliance)

Agency Response: Please see Agency Responses to Comments 9-12,

15, and 56. As stated in the response to Comment 15, the relevant inquiry 

here is whether the Supreme Court interpreted the meaning of emission 

standard as applicable to mobile sources under Title II, and not EPA’s 

waiver determination, although one could say that EPA’s analysis 

regarding OBD systems being emission standards is fully consistent with 

the Supreme Court’s interpretation that under Title II, an emission 

standard includes design features related to the control of emissions. 

As stated in earlier responses, ARB continues to believe that it has the 

authority under existing California law to adopt OBD compliance and 

enforcement provisions, including taking corrective actions through recall. 

As stated, ARB revised the definition to help ensure that the regulations 

continue to be fully enforceable, will achieve needed emission reductions 

for the purpose of protecting the public’s health and safety, and provide 

necessary notice to affected stakeholders that OBD requirements are 

unquestionably emission standards. Finally, the commenter’s assertion 

that “EPA’s mobile source regulations do not define ‘emission standard’ to 

include OBD,” is misplaced. In agreement with comments of AAMA, EPA 

has stated that its general authority to set standards for new vehicles is 

found at CAA section 202 and that subsection 202(m) specifically states 

that federal OBD requirements shall be promulgated under subsection 

202(a). In other words, federal OBD requirements are emission 

standards. 

LEAD TIME, FEASIBILITY, AND COST-EFFECTIVENESS

17.Comment: We have frustrations with the process that has followed for 

these complicated and demanding regulations. These amendments were 

heard at the August 2012 hearing to deal with products that will be built a 

few months later. Many manufacturers already submitted their OBD 

certification documents to ARB for approval. These rules get finalized 

years ahead of certification dates, not months. (Cummins)

18.Comment: ARB’s review of technology and changes to requirements 

during a biennial review cannot wait – as it is happening right now – until 

after the model year for new requirements have already started, and when 

manufacturers have invested their limited resources in meeting regulatory 

requirements and under time constraints to certify their products. 

Manufacturers need certainty in the standards and timeframe to meet 

them so they may use their limited resources most effectively. There are 

a number of ways ARB’s rulemaking process, and this rule in particular, 

disregards the real notice and timing issues that manufacturers face. The 
16

most obvious of these is the proposal for new continuous misfire 

monitoring with less than sufficient lead time. In other words, ARB is 

making changes to the rule and adding new requirements when it is 

already far too late in the design, engineering and production processes 

that manufacturers must utilize. (EMA)

Agency Response to Comments 17-18: Proposed amendments that apply 

to model years currently being built are generally relaxations of current 

requirements that were specifically requested by industry so that they can 

certify their products without issues. While the manufacturers have made 

a good faith effort and have advanced OBD capability beyond the 2010 

requirements, their progress has fallen short of meeting the previous 

more stringent 2013 requirements, which is the basis for the relaxations. 

However, manufacturers would not have put in the effort to meet these 

requirements had the thresholds been higher and less stringent in the 

previous years. Additionally, the manufacturers would eventually be 

required to meet the stringent requirements in the near future, and would 

more likely be able to meet them within the required deadlines if they 

started the work early. Thus ARB staff does not believe manufacturers’ 

efforts trying to meet the previous stringent requirements were a waste of 

resources like manufacturers believe. Other proposed amendments (e.g., 

in-use monitor performance requirements) that apply to current model 

years are related to previous requirements that required manufacturers to 

propose a plan (for Executive Offer approval) to meet the requirement, 

with the amendments now specifying criteria that Executive Officer has 

been approving for manufacturers. These amendments will not require 

any more resources and time for manufacturers to meet. Proposed 

amendments that are more stringent or designate new requirements have 

been given enough lead time and start with the 2016 model year at the 

earliest, including the continuous misfire monitoring requirement 

mentioned above. 

19.Comment: Many of the proposed HD OBD amendments constitute new or 

changed requirements that engine manufacturers must meet before 

selling their products. Thus, the requirements are subject to clear 

mandates by the U.S. Congress in the federal CAA and by California 

legislature in state law. Any mobile source emission standards adopted 

by ARB for on-highway engines and vehicles from over 8,500 lbs. require 

a waiver of federal preemption from U.S. EPA, must be technologically 

feasible and cost-effective, and may be implemented only if the requisite 

lead time and period of stability are provided to manufacturers. Section 

209(b) of the CAA requires ARB’s emission standards to be consistent 

with Section 202(a) for EPA to waive federal preemption and allow 

California to enforce its own emission standards. Unless ARB 

demonstrates that the standards are technologically feasible and costeffective and provided sufficient lead time and stability to engine 

manufacturers, California cannot obtain the necessary preemption waiver 

from EPA. (EMA)
17

Agency Response: In Resolution 12-29, the Board directed staff to request 

a new waiver from U.S. EPA if needed, and made all the necessary 

findings necessary to obtain a waiver. Contrary to the unsupported 

assertions of the commenter, the staff report fully supports the findings of 

the Board that the requirements of this regulation are technologically 

feasible and cost-effective. Although technological feasibility and costeffectiveness, along with a finding that the regulations are necessary, are 

requirements under California law (Health and Safety Code section 

43013), cost-effectiveness is not a required element for granting a waiver 

under section 209(b) of the CAA. Additionally, the OBD requirements are 

not subject to the lead time and stability requirements specified in the 

CAA. See agency response to comments 20-22 for more details. 

20.Comment: ARB must adopt OBD requirements that are technologically 

feasible. However, staff has failed to justify the technological feasibility of 

many of the proposed requirements. According to CAA Section 209(b), 

which authorizes California to adopt emission standards for mobile 

sources only if certain conditions are met, the standards must meet CAA 

Section 202(a), which requires that, among other things, “standards must 

reflect the greatest degree of emission reduction achievable through the 

application of technology...determine[d to] be available for the model year 

to which such standards apply, giving appropriate consideration to cost, 

energy, and safety factors associated with the application of such 

technology.” California law also requires that emission standards be 

justified and technologically feasible (Health and Safety Code §43013). 

Manufacturers have spent and continue to spend significant resources in 

meeting the OBD requirements, and are forced to expend resources each 

time changes to the OBD rule are adopted to meet the new technological 

challenges. Yet many times, those challenges were proven to be 

infeasible requiring last minute changes and wasting manufacturers’ 

limited resources. As ARB staff explained in the staff report, some of the 

thresholds and requirements that ARB adopted in 2005 for HD OBD and 

amended in 2009 were not feasible and must now be revised. While ARB 

can set technology-forcing standards, it has an obligation to set standards 

that reasonably can be projected to be technologically feasible. 

Manufacturers should not be required to expend time and effort (i.e., their 

limited resources and precious test cell time) in trying to develop costly 

monitoring strategies that are not feasible. (EMA)

Agency Response: Contrary to the unsupported assertions of the 

commenter, the staff report fully supports the findings of the Board that the 

requirements of this regulation are technologically feasible. Further, the 

proposed amendments have set forth technically feasible monitoring 

requirements, and it is not expected to make significant changes to the 

regulation in the future. As required, staff has identified methods that are 

already in-use or could be used to meet each proposed monitoring 

requirement, determined that such methods will likely succeed in getting 

there, and addressed all technical issues regarding the monitoring 

requirements raised by industry. Additionally, several of the amendments 
18

relax previously adopted monitoring thresholds to a higher emission level. 

The 2009 amendments were not made because the initially adopted 

requirements were technically infeasible. Staff recommended interim 

relief due to the complexity of the 2010 emission control solutions being 

pursued by several manufacturers—including some configurations that 

appear to be negatively impacting OBD monitoring capability. As stated 

during the original rulemaking for HD OBD, manufacturers must take OBD 

monitoring capability into account when designing and calibrating 

emission control solutions to achieve a solution that meets all ARB 

requirements, not just some of them. Nonetheless, staff felt some interim 

relief was needed because of the last minute struggles some 

manufacturers were having in meeting the 2010 heavy-duty vehicle 

emission standards with the emission control solutions that they had 

chosen to pursue. This, in turn, left their OBD engineers with very little 

time to address the OBD monitoring requirements (i.e., to discover the key 

design factors they needed to influence and modify to allow for OBD 

compliance). Staff expected that the interim relief would provide additional 

stability and time for the OBD engineers to improve their capability and/or 

better influence the design to ensure an integrated and fully compliant 

solution, especially for those that have a less then optimal configuration in 

2010. As historically has happened, manufacturers will likely gravitate 

toward solutions that provide for full compliance especially as they gain 

experience in-use as well as evaluate competitor’s solutions. The 

resources that manufacturers have spent working towards complying with 

the OBD requirements, including those that staff eventually relaxed with 

this rulemaking, were not wasted. The vast majority of the resources were 

still essential for manufacturers in developing and implementing the 

monitor even at the relaxed, less stringent threshold. Further, for 

monitoring requirements where staff relaxed the thresholds, some 

manufacturers were on track to meet the previous, tighter thresholds, 

which demonstrates that the thresholds were technically feasible to 

achieve, but several manufacturers had not been as successful. Thus, in 

reviewing the industry status as a whole and taking into account that 

manufacturers were substantially expanding from OBD systems on one 

engine family to OBD systems on all engine families in the 2013 model 

year, staff felt that relief for a few specific monitors was warranted. 

Considering these modifications and relaxations only affected a small 

number of the total individual monitoring requirements, staff’s original 

assessment of what was technically feasible in the scheduled 

implementation time frame was predominantly on target. 

21.Comment: The proposed amendments must be cost-effective according to 

both federal and state law. Section 202(a) of the CAA requires the Board 

to consider cost and other related factors in setting new heavy-duty engine 

and vehicle emission standards. The California HSC establishes a similar 

mandate for ARB, requiring the Board to adopt emission standards which 

will result in the most cost-effective combination of control measures on 

motor vehicles and fuel. And California Government Code sections 

11346.3 and 11346.5 require the Board to assess the proposal’s 
19

economic impact. The ARB staff has not met the burden of showing its 

proposal is cost-effective. Staff has both underestimated the costs to 

engine manufacturers and vehicle owners and has not fully analyzed the 

cost-effectiveness (the costs vs. the emission benefits). ARB’s cost 

effectiveness and emissions benefit discussion in the staff report is faulty 

in two ways. First, it based its cost estimates on manufacturers’ 

nationwide sales of engines and vehicles, which is misleading and 

improper since this is a California rule. Second, it points to ARB’s 

previous analysis of cost-effectiveness from the 2009 amendments to the 

OBD rule, which were based on the 2005 adoption of the HD OBD 

regulation. ARB relies on past analysis nearly a decade old for its current 

rulemaking, which is inherently unreasonable. It is not realistic to assume 

that heavy-duty manufacturers will meet the extremely complex, evermore-stringent OBD requirements and increase engine durability while 

holding down the cost of new products as ARB estimates. Further, ARB 

failed to assess the cost impact and anticipated benefits of 2012 

requirements. EMA questions whether ARB could justify any of those 

requirements if it were to properly analyze and assess the OBD rule and 

its costs against the anticipated emissions benefits. ARB must conduct a 

thorough, updated and focused analysis on the amendments to determine 

their true costs for manufacturers and consumers as well as their true 

benefits to air quality. (EMA)

Agency Response: The staff disagrees. The staff’s calculations, 

developed with input from engine manufacturers, did include all costs to 

the engine manufacturers for development, calibration, testing, personnel, 

and hardware costs to sufficiently cover all of the proposed requirements. 

Further, for heavy-duty diesel engines, all but one of the proposed

changes with this rulemaking do not materially impact the costs to develop 

or implement a compliant OBD system, which incorporates the most 

recent amendments, making the cost estimates from the original 

rulemaking in 2005 appropriate. As discussed in the staff report and the 

15-day notice, the additional costs associated with the reporting 

requirement for the more comprehensive diesel misfire monitoring 

requirements (that begin in 2016) are expected to result in an incremental 

retail price increase of $0.59 per vehicle. Also as discussed in the staff 

report and 15-day notice, for alternate-fueled heavy-duty engines, the 

associated costs to implement full OBD systems two years earlier than 

previously required are expected to result in an incremental retail price 

increase ranging from $23 to $228 per vehicle for these two years. 

Regarding cost-effectiveness being a criterion for receiving a waiver under 

the CAA, see agency response to comment 16 above. 

22.Comment: The HD OBD regulation must provide sufficient lead-time and a 

period of stability. Engine manufacturers need sufficient time to develop 

OBD technology that is feasible and practical. California law requires that 

the standards must be adopted within reasonable time frames (HSC

section 43013). Section 202(a) of the CAA requires that any new 

emission standards may go into effect only four or more full model years 
20

after the year in which they were promulgated, and those new standards 

must stay in effect for at least three full model years before ARB may 

establish another standard. Providing reasonable notice of the 

requirements that manufacturers must meet and giving them enough time 

in which to attempt to comply with the requirements is not just a legal or 

academic exercise - it is essential to the way manufacturers do business. 

Unless California meets these requirements, it has no authority to adopt 

emissions standards for on-highway heavy-duty engines. (EMA) 

Agency Response: The commenter submitted the same comments 

regarding lead time and stability during the engine manufacturer 

diagnostic (EMD) rulemaking in 2004, the HD OBD rulemaking in 2005, 

the OBD II rulemaking update in 2006, and the HD OBD rulemaking 

update in 2009. In each of these rulemakings, ARB had provided a 

detailed response indicating why the federal lead time and stability 

provisions do not apply to the OBD regulations (see the Final Statement of 

Reasons for Rulemaking for the EMD, heavy-duty OBD, and OBD II 

regulations). Yet, the commenter has given the same comments again for 

this rulemaking. Thus, the following response is essentially the same as 

those given in the previous rulemakings.

Regarding the commenter’s lead time and stability arguments, since 1970, 

U.S. EPA has typically applied a “two-pronged” test of whether California 

standards are consistent with CAA section 202(a) as required by section 

209(b)(1)(C). The standards first must be technologically feasible in the 

lead-time provided considering the cost of compliance, and second must 

be compatible with the federal test procedures so that a single vehicle 

could be subjected to both tests. No more should be required.

This is in accord with the legislative history of section 209. When the 

California waiver provisions and the “consistent with section 202(a)” 

language were first placed in the CAA in 1965, section 202(a) consisted of 

just one sentence requiring adequate lead time in consideration of 

technological feasibility and economic costs. In the 1977 CAA 

amendments, Congress amended section 209 “to afford California the 

broadest possible discretion in selecting the best means to protect the 

health of its citizens and the public welfare.” (H. R. Rep. No. 294, 95th 

Cong., 1st Sess. 301 (1977), reprinted in 4 Leg.Hist., at 2768.) At the 

same time, Congress expanded section 202(a) to add several directives to 

U.S. EPA regarding its adoption of emission standards, including the fouryear lead time requirement for heavy-duty vehicles. (Emphasis added.) 

Given Congress’s expressed intent to strengthen the waiver provisions, it 

is unlikely Congress intended to apply the specific four-year requirement 

to California, which would effectively narrow the deference provided to the 

state.

This is especially true in the case of OBD requirements. Congress clearly 

did not intend the OBD requirements to be subject to the lead-time and 

stability provisions of CAA section 202(a)(3)(C). First, as indicated above, 
21

those requirements were first enacted in 1977 and specifically applied to 

heavy-duty vehicle emission reductions, which at that time solely 

consisted of tailpipe and evaporative emission standards that Congress 

directed U.S. EPA to implement for new heavy-duty vehicles. (1977 CAA, 

section 202(3)(B).)

It was not until the 1990 CAA amendments that Congress enacted an 

entirely new provision, section 202(m), which directed the Administrator to 

adopt regulations to implement OBD requirements. Under the new 

provision, Congress directed the Administrator to promulgate regulations 

for new light-duty vehicles and light-duty trucks within 18 months of 

enactment. (CAA section 202(m)(1).) Additionally, at the Administrator’s 

discretion, Congress provided U.S. EPA with equivalent authority to adopt 

OBD requirements for new heavy-duty vehicles. (Id.) The federal CAA 

further provided that the effective date for those regulations initially 

adopted under section 202(m) shall be the model year 1994, unless the 

Administrator postpones application for certain classes and categories of 

vehicles until the 1996 model year. The Administrator could decide to 

delay implementation for reasons that the OBD requirements were 

infeasible or to be consistent with the policies adopted by the ARB. (CAA 

section 202(m)(2).) Thus, theoretically, under the provisions of CAA 

section 202(m), the Administrator had effective authority to promulgate 

and implement OBD requirements for heavy-duty vehicles as early as the 

1994 model year. Assuming that such requirements were adopted in June 

1992 (18 months after the enactment of the CAA), Congress would have 

provided less than the requisite time allowed for implementation under 

CAA section 202(a)(3)(C). Accordingly, it would be appropriate to infer 

that Congress never intended that the OBD requirements be subject to the 

lead-time provisions of section 202(a)(3)(C).

This is confirmed by the administrative actions of U.S. EPA. Although the 

Administrator initially chose not to adopt OBD requirements for heavy-duty 

vehicles (58 Fed.Reg.9485 (February 19,1993)), OBD requirements were 

subsequently adopted and applied to medium-duty passenger vehicles (a 

subclass of heavy-duty vehicles). (64 Fed.Reg.23925 (May 4, 1999).). 

Adopted federal regulations provide, “Except as otherwise indicated, the 

provisions of this subpart apply to new 2001 and later model year Ottocycle and diesel cycle light-duty vehicles, light-duty trucks, medium-duty 

passenger vehicles [“MDPVs”] . . ..” (40 Code of Federal Regulations 

(“CFR”), subpart, S §86.1801-01. Emphasis added.) Under the 

Administrator’s adopted definition, a heavy-duty vehicle is defined as “any 

motor vehicle rated at more than 8,500 pounds GVWR [gross vehicle 

weight rating] or that has a vehicle curb weight of more than 6,000 pounds 

or that has a basic vehicle frontal area in excess of 45 square feet. (40 

CFR 1803-01.) MDPV is defined as “any heavy-duty vehicle . . . with a 

[GVWR] of less than 10,000 pounds that is designed primarily for the 

transportation of persons.” (Id). The specific OBD requirements were set 

forth in section 86.1806-01 of the same regulation and provide that certain 

MDPVs, as well as light-duty vehicles and trucks, are required to meet the 
22

OBD standards set forth therein. An exception applied to diesel-fueled, 

chassis-certified MDPVs and engine-certified diesel engines used in 

MDPVs, but no exception exists for Otto-cycle MDPVs, which are subject 

to the requirements of section 1806-01. (40 CFR 1806-01(a)(2). These 

vehicles were only subject to the requirements if the exhaust emission 

certification of the applicable test group is being carried across from a 

California configuration to which California OBD II requirements are 

applicable.) The OBD provision does not provide for a separate and 

distinct implementation date for MDPVs to meet the OBD requirement. 

Accordingly, under the terms of section 1806-01, the 2001 and later model 

year implementation requirements would deem to be applicable to the 

OBD requirement. In such a case, the lead-time provided under the 

regulations would be less than two years from the May 4, 1999 initial 

promulgation date of the regulation.

Section 1806-05, which establishes OBD requirements for heavy-duty 

vehicles weighing 14,000 pounds GVWR or less, including diesel-powered 

MDPVs, provides a similarly abbreviated lead-time period. (68 Fed.Reg. 

35800, June 17, 2003, 40 CFR section 1806.05.) The regulations were 

adopted in June 2003 and apply to 2005 and later model year vehicles. 

The lead-time again is well below the minimum four years of lead-time 

required under section 202(a)(3)(C). For the foregoing reasons, the only 

reasonable inference is that Congress did not intend that the provisions of 

CAA section 202(a)(3)(C) apply to OBD requirements and specifically not 

to California adopted OBD requirements. 

In granting California a waiver for the HD OBD regulation in 2008, EPA did 

not consider the lead time and stability provisions of CAA section 

202(a)(3)(C). 

MONITORING REQUIREMENTS

23.Comment: Regarding the proposed phase-in schedule for the NOx 

converting catalyst and NOx sensor monitors in the HD OBD regulation, 

while the phase-in is directionally helpful for manufacturers, ARB did not 

go far enough in accounting for the realities of the technologies required to 

meet such stringent requirements. 

There are only small differences between the “generation 2.0” NOx sensor 

available for the 2010 model year (tolerances of +/-15ppm in the 0-

100ppm range and +/-15 percent above 100ppm) and the marginally 

better “generation 2.5” sensor available for the 2013 model year (tolerance 

+/-10ppm in the 0-100ppm range and +/-10% above 100ppm). If the 

generation 2.5 sensor is used to meet the proposed 2016 model year 

threshold of 0.2 g/bhp-hr above the NOx standard, there will be too little 

separation between a failure and passing conditions to assure a robust 

monitoring strategy. To make a proper evaluation of the NOx sensor, 

many important inputs are considered. The NOx sensor values are 

compared to a modeled NOx level, and with a perfectly tuned model 
23

considering humidity, ammonia slip, etc., the sensor tolerance will be the 

only noise factor to account for. The NOx sensor signal can be used to 

both control the target selective catalytic reduction (SCR) efficiency and 

monitor the catalyst efficiency. Since two NOx sensors are the common 

setup, SCR efficiency is important for the evaluation and stable conditions 

are required to get good evaluation conditions. The NOx sensor monitor 

is performed in the 150-190ppm NOx range during stable conditions, and 

tests show that for an average NOx level of 180ppm for a good performing 

system (SCR efficiency at 90 percent), the sensor tolerances will impact 

the monitors and especially the minimum level of the sensor. A NOx 

sensor with a tolerance of 10 percent below nominal will present an actual 

conversion efficiency of 80 percent when targeting 90 percent. The OBD 

threshold of two times the emission standard will be reached when the 

conversion efficiency decreases to ~84 percent and the NOx sensor 

monitor will not be able to separate a fault from a good system. Too low 

thresholds, which results in non-robust monitors, will have a negative 

impact on the engine manufacturers’ product and customers.

Regarding the SCR monitor, the dynamics of the SCR system and its 

control present significant challenges (the same challenges across 

manufacturers regardless of catalyst substrate, precious metal coating, 

and control system design) when attempting to detect a malfunction at a 

threshold of 0.2 g/bhp-hr above the applicable NOx standard. SCR 

conversion efficiency and NH3 storage dynamics impact the diagnostic 

design. Modern SCR systems are capable of optimal conversion 

efficiency in excess of 90 percent, with outlet NOx less than 10 percent of 

intake NOx. Thus, a system degraded to the level required to be detect by 

OBD is still a highly functioning system. Compounding this problem, the 

instantaneous conversion efficiency of a good catalyst can change 

dramatically given its operating conditions (temperature, volumetric flow 

rate, etc.) to the point where it can resemble a bad catalyst, and vice 

versa. These two systems are often difficult to separate on the FTP cycle 

for some engine power ratings and can be nearly impossible under worst 

case vehicle duty cycles like those of a delivery truck which makes 

frequent load changes and has several ignition cycles in a short period. 

NH3 storage exhibits highly dynamic properties based on operating 

conditions like exhaust gas temperature and volumetric flow rate and is a 

significant contributor to the change in SCR conversion efficiency on good 

and bad systems. While NH3 storage is a known property of SCR, it has

proven very difficult if not impossible to model accurately due to NH3 often 

being distributed non-uniformly along the catalyst and its distribution 

related to prior operating conditions. NH3 slip (resulting from desorption 

of excess stored NH3) is prevalent in vehicles with highly transient duty 

cycles due to the rapid and constant change of NH3 storage capacity and 

can be difficult to predict in advance, and modeling the magnitude and 

rate of the desorption is equally challenging. Tests have shown NH3 slips 

to take over 60 seconds to fully propagate through the SCR catalyst to 

where they can be detected by instrumentation. ARB staff’s comment in 

the May 29, 2009 HD OBD staff report that active/intrusive methods may 
24

be possible for evaluating SCR efficiency with little emissions impact has 

shown to be currently not possible based on recent experiments in an 

independent laboratory. These tests show that the time to adsorb and 

desorb sufficient NH3 to generate a reliable diagnostic signature can take 

multiple minutes, which is not feasible in a vehicle without constant 

operating conditions. Most manufacturers position NOx sensors before 

and after the SCR catalyst to provide real-time feedback. 

The most significant factors facing the SCR sensing system are sensor 

accuracy and sensor cross-sensitivity to NH3. Regarding sensor 

accuracy, experiments used to measure the probabilities that NOx 

sensors with varying degrees of accuracies would correctly determine a 

failing system and a healthy system with a threshold of +0.2 g/bhp-hr 

show that generation 2.5 sensors still yield errors of 0.12% for improperly 

failing healthy systems and errors of 0.16% for improperly passing failing 

systems. Only a NOx sensor with accuracy levels of +/-5ppm from 0-

100ppm and +/-5 percent from 100-1500ppm can achieve a separation 

with 0.00 percent errors for improper detections. Tests also showed that 

with higher OBD thresholds, sensor error is not significant enough to 

cause misdetections based on a conversion efficiency calculation. 

Regarding sensor cross-sensitivity to NH3, the range of NOx sensor 

sensitivity to NH3 varies from 70 to 250 percent when it is new up to 60 to 

200 percent when it is aged. For example, 100ppm of NH3 at the 

downstream exhaust will be reported by a sensor with 95 percent NH3 

cross-sensitivity as an additional 95ppm to the reported downstream NOx 

measurement. NH3 at the exhaust outlet can be due to released 

ammonia from the SCR catalyst due to temperature rises, a very 

aggressive urea injection to SCR catalyst strategy, and reduced SCR 

catalyst NH3 capability. For example, if the NOx sensor is cross-sensitive 

to NH3 at the 90% level, an increase of 10ppm NH3 at the tailpipe will 

increase the width of distribution by +/-5 percent, with such increase in 

variance width degrading the capability of NOx sensor-based NOx 

conversion efficiency evaluation as the error rates grow to 2.33 percent 

(from 1.99 percent) mis-detection and 2.54 percent (from 2.16 percent) 

false-detection for generation 2.0 sensors.

While the NOx sensor technology has developed much, the sensor 

accuracy, reliability, and durability have not kept up to a sufficient degree 

with the extremely stringent NOx thresholds that have been implemented 

over time. EMA had requested in 2009 that ARB change the NOx 

aftertreatment 2010 emission thresholds due to the then-accuracy of the 

NOx sensor technology. Even now, NOx sensor suppliers have indicated 

it is unlikely additional improvements in sensor measurement accuracy will 

be achievable. Thus, EMA proposes that the phase-in schedule be 

changed to require 10 percent of the 2014 volume and 20 percent of the 

2015 volume meet +0.3, with an extension to +0.2 in 2017 for those 

engines meeting the +0.3 threshold in 2014 and 2015. (EMA)
25

Agency Response: ARB disagrees and did not make these changes. ARB 

staff has already addressed these comments in the Staff Report, but will 

summarize them here. 

Staff has met with virtually every manufacturer and several suppliers to 

assess current capability and what improvements are available in the near 

term. 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 capability is sacrificed. 

Thus, staff was 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). 

When talking with manufacturers and suppliers, staff identified several 

items that continue to show promise for achieving the previous 2013 

model year threshold of the NOx tailpipe standard + 0.2 g/bhp-hr. As 

noted by the commenter, NOx sensor accuracy is not expected to get 

appreciably better, 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 of the 

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 +0.2 g/bhp-hr 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.
26

Lastly, staff believes that a 10/20 percent phase-in schedule in the 

2014/2015 model years would not provide manufacturers enough 

exposure to different engines and applications during calibration and 

development and in-use to be able to identify and correct issues that may 

come up before full-scale implementation in the 2016 model year.

24.Comment: Regarding the proposed phase-in schedule for the PM filter 

monitoring requirements and the proposed phase-out of the failure mode 

exemption in the HD OBD regulation, while the phase-in is directionally 

helpful for manufacturers, ARB did not go far enough to address the 

significant challenges with using PM sensors to meet the extremely 

stringent thresholds and without the failure mode exemption. EMA 

predicted in the written comments for the 2009 biennial review that the 

requirements ARB set for 2013 will cause manufacturers to expend 

significant resources without sufficient technological success. ARB noted 

in the Staff Report that only one light-duty manufacturer is able to 

implement PM sensors in 2013 and a few heavy-duty manufacturers were 

going to meet this goal but abandoned those efforts. As ARB and PM 

sensor suppliers state, PM sensors are not ready for full scale 

implementation in the 2013 model year. 

The common PM filter monitoring method today involves using a delta 

pressure sensor, but at some point it will be hard to distinguish failures 

from fault free filters due to part tolerances, sensor tolerances, aging, 

driving conditions and different application installations. PM sensors today 

are being developed for heavy-duty vehicles but the technology is new 

and sensors are at the prototype stage. It is important that engine 

manufacturers continue evaluating available technology. The current 

technology has sensor-to-sensor variability as well as run-to-run variability 

that is too high for a robust monitor. Introducing new sensors require 

robust technology to use in different driving conditions and different 

vehicle applications. One PM sensor supplier has said they can meet a 

1.75 times threshold for a 2013 light-duty application only if the 

manufacturer defines a “good” filter to be well below the tailpipe PM 

standard (3 mg/mi versus the 10 mg/mi standard). This means good 

filters delivering 4 mg/mi would be at risk of illuminating the MIL. So the 

minimum PM sensor detection capability would be to distinguish a 3 mg/mi 

filter from an 18 mg/mi (1.75 times) filter, with the resultant threshold 

multiplier capability closer to 6 times the standard (18/3). A manufacturer 

conducted PM filter monitor testing using a PM sensor on a European 

light-duty application intended to meet a 4.5 mg/km PM standard – PM 

sensor data on filters with 2.6 mg/km (“good”) and 7.3 mg/km (“threshold”, 

at 3 times separation in tailpipe PM from the “good” filter) showed 

significant overlap during real world driving. In order to detect a 

“threshold” filter, the threshold would have to be set at level such that a 

“good” filter would be detected as bad on a number of driving events. 

Since the data was collected from only one vehicle, vehicle-to-vehicle and 

sensor-to-sensor variability have not been accounted for and would further 

increase the occurrence of false MILs for this sensor capability. With 
27

current PM sensor technology, the threshold would have to be at least 6 

times the PM standard to distinguish a good filter from a bad filter. 

Recent data show that PM sensors will not be capable of meeting the 

0.03 g/bhp-hr threshold without significant risk of false failures. EMA 

proposed that the percentages in the phase-in schedule be halved to 

require 10 percent of the 2014 and 2015 volume to meet 0.05 without the 

failure mode exemption or 25 percent of the 2015 volume to meet 0.03 

without the failure mode exemption. Further, EMA proposes that the 

phased-in engines not be required to illuminate the MIL or store fault 

codes during the 2014-2015 phase-in – instead, manufacturers would 

gather data in “silent mode” to be used for further development of robust 

monitoring technologies capable of meeting the requirements in 2016. 

This provides a logical allocation of the phase-in to the product mix in the 

early years (a reduced number of original equipment manufacturers 

(OEMs) with a reduced number of models) and will limit liability (due to 

false failures) for sensor suppliers in the phase-in years, for end users, 

ARB as a regulatory agency interested in acceptable of the diagnostic 

technology, and engine and vehicle manufacturers. Even with these 

modifications, manufacturers’ rationality diagnostic approach and proveout will be difficult and problematic, and manufacturers will face big 

challenges when trying to integrate PM sensors with delta-pressure 

sensing technology across all products including their use to improve inuse monitor ratios, which needs development time. The PM sensor may 

be an integrated assembly of an exhaust gas probe and interface module 

that come from separate suppliers and both have development challenges 

(e.g., probe-clogging concerns, module may require voltage control 

enhancements to more reliably clean sensor element and detect failed 

filter in a timely manner). (EMA)

25.Comment: Reducing the phase-in levels will drive the use of the same 

mature technology but limit the overall risk and problems related to 

emerging technology for customers. Government, manufacturers, and 

customers need reliable and dependable engines in vehicles. 

(EMA)(Cummins)

26.Comment: Reducing the phase-in levels while maintaining inadequate 

technology introduction strategy will provide responsible customer 

exposure related to such emerging technology. One comment that was 

made was we would move away from delta pressure sensors to PM 

sensors – the way we see things involves using both together. So we will 

be able to deliver reliable solutions in the 2016 time frame. A ten percent 

level in 2014 would give experience with the sensor and modifications to 

the aftertreatment systems and to sampling of vehicles and making sure 

the technology is developed. Going from 10 percent to 100 percent (or 

zero percent to 100 percent for low volume manufacturers) is a step 

change. We could better manage the introduction better if it’s kept to 

fewer engine/vehicle models. (Cummins)
28

Agency Response: ARB disagrees with reducing the phase-in levels and 

did not make these changes. Staff believes that halving the phase-in 

schedule in the 2014/2015 model years would not provide manufacturers 

enough exposure to different engines and applications during 

development, calibration, and in-use to be able to identify and correct 

issues that may come up before full-scale implementation in the 2016 

model year. Staff also believes that proposing a “silent mode” in the 

2014/2015 model years would not help the situation, since engineers 

would not attack the problem with the same mindset or resolve to address 

issues if they know ahead of time that there is no risk of having incorrect 

monitor decisions in the field. Further, staff’s discussions with PM sensor 

suppliers and engine manufacturers have confirmed that there is sufficient 

availability of sensors and engine/vehicle configurations that are more 

readily adaptable to a sensor in the 2014 and 2015 model year time frame

to meet the phase-in requirements.

Regarding the comment that insufficient separation exists between a 

‘good’ filter and a ‘bad’ filter, ARB disagrees that the cited data supports 

such a conclusion. First, it is inappropriate to characterize a multiplicative 

threshold based on the actual emission level below the standard, as the 

commenter does, by using the actual emission level of 3 mg/mi as the 

‘standard’ in the light-duty example. To illustrate the point, using a similar 

methodology to characterize the PM filter thresholds for heavy-duty 

engines would find that the vast majority of 2013 model year engines were 

certified at the end of full useful life as emitting at less than 3 mg/bhp-hr 

even though the standard was 10 mg/bhp-hr. Comparing that to the OBD 

thresholds of 50 and 30 mg/bhp-hr for 2014 and 2015 model years, 

respectively, the calculation would conclude that the proposed OBD 

thresholds are 16 and 10 times the ‘standard’, well above the 6 times the 

‘standard’ that the commenter claims is necessary. 

Additionally, with respect to the first example cited of a light-duty vehicle 

and the monitoring capability as determined by a PM sensor supplier, staff 

took a quick look at certification data for 2013 model year light-duty 

diesels and found the vast majority of them were certified at full useful life 

as emitting at or below 3 mg/mi. As such, characterizing a filter with such 

emission levels as a ‘good’, or ‘worst performing acceptable’ (WPA) in 

OBD monitoring terms, is actually appropriate and common practice in 

industry for emission components that have a continuum of degradation 

such as gasoline catalytic converters or diesel PM filters. Further, the 

definition of a filter at 3 mg/mi as the WPA does not mean that filters 

emitting at a level of 4 mg/mi would be at risk of illuminating the MIL. The 

‘best performing unacceptable’ (BPU) component would be defined as the 

filter emitting at or just below the OBD threshold (of 1.75 times the 

standard or 17.5 mg/mi in this example). As such, a filter at 3 mg/mi 

would be certain to not be detected as a failing part and a filter at 17.5 

mg/mi would be certain to be detected as a failing part. The reaction of 

the system to components emitting at interim levels between the two 

would depend on the separation between the two in terms of the 
29

monitored parameter (e.g., the PM sensor signal and corresponding 

algorithm used to translate the PM sensor signal into a measure of the 

filter performance). In an ideal scenario, a separation of at least four 

sigma exists from the mean of the WPA population to the threshold and a 

separation of at least two sigma exists from the mean of BPU population 

to the threshold. From the example cited, there is no way of estimating 

what level of separation exists and therefore, there is no way of 

concluding a 4 mg/mi filter would be at risk of illuminating the MIL. 

Further, based on discussions with light-duty manufacturers including the 

one certified in 2013 model year with a PM sensor, the sensor and 

associated algorithms seem quite capable of robustly discerning between 

filters as defined in the example above as WPA and BPU. 

Regarding the example of a European light-duty application designed for a 

non-US market, staff’s experience is that monitoring capability on such 

applications significantly lags behind the capability of systems designed to 

meet ARB’s OBD requirements. Further, the numbers cited of a 4.5 

mg/km standard suggest a lower PM standard than ARB currently has and 

the 7.3 mg/km threshold would suggest an OBD threshold of 1.6 times the 

standard, which is a tighter threshold than ARB has. For reference, the 

proposed HD OBD thresholds are effectively 5 times and 3 times the 

standard, respectively, for the 2014 and 2015 model years. There does 

not seem to be a reasonable inference to conclude that the presence of 

overlap (between two much lower and closer together emission levels and 

based on a monitoring algorithm developed for the European market) 

logically means that insufficient separation will exist between higher and 

further apart emission levels and with a likely more sophisticated and 

capable algorithm developed for future model years to meet ARB’s HD 

OBD requirements. 

 

27.Comment: The proposed amendment to require continuous misfire 

monitoring starting in the 2016 model year does not provide the four 

model year lead time required by law. The 2013 model year is already 

underway (beginning January 2, 2012). The proposed amendment should 

begin January 2, 2017 if the proposal is approved by December 31, 2012. 

If not, then the earliest the new requirement can be implemented is 

January 2, 2018. 

ARB also should add a minimum load range at which misfire would be 

required to be continuously detected. The proposed detection at engine 

load 5 percent above the positive torque line is too light a load for robust 

misfire detection, and may result in false failures, which ARB and EMA are 

both sensitive to and should minimize. Crankcase sensor-based misfire 

detection is more difficult in heavy-duty diesel engines than light-duty due 

to the increased crank-twist and wide variety of torque noise factors from 

multiple OEM driveline designs and intermittent high accessory loads. 

Light-duty OEMs usually only need to calibrate one misfire algorithm for 

automatics and one for manual to be used across most of their fleet, while 

heavy-duty engine manufacturers have a wide variety of transmission/final 
30

drive/chassis combinations with widely varying vehicle applications, which 

increases the chance of false misfire detections. ARB should modify the 

language in both the HD OBD and OBD II regulations to require detection 

above 20 percent peak torque up to 75 percent peak torque and between 

low idle and 75 percent max-rated engine speed. Misfire detection is still 

required elsewhere in the regulation. This slight extra carveout will not 

impede misfire detection as heavy-duty diesels operate mostly within the 

proposed monitoring torque range and generally only pass the light load 

region during short load transitions. ARB should also change the 

conditions of engine load to peak torque to simplify the detection regions, 

since load can vary widely at a given operating point and peak torque is 

less ambiguous. 

Additionally, changes should be made to address special operating 

conditions where misfire detection can be difficult, such as active PM filter 

regeneration, which may involve a unique modulation of injection events 

that alter dynamic characteristics causing variability which inhibit the 

misfire monitor’s ability to detect faults. The frequency of filter 

regeneration continues to decrease as manufacturers continue to develop 

technology that result in reduced fuel consumption and greenhouse gas 

emissions. So misfire detection during this small period of filter 

regeneration should be exempted. Additional conditions already 

recognized for medium-duty vehicles in the OBD II misfire requirements 

should also be recognized in HD OBD requirements, including fuel cut-off, 

heavy-transient conditions, rough road, and intrusive tests. (EMA)

Agency Response: Regarding the lead time issue, ARB disagrees with 

delaying the requirement and did not make this change. Please see 

agency response to comment 22 for more details. Regarding the 

comment to change the engine load condition to peak torque condition 

and to add a minimum torque range for continuous misfire monitoring, 

ARB agreed to change the load condition to peak torque in both the HD 

OBD and OBD II regulations and to add a minimum 20 percent peak 

torque condition for the initial years of continuous misfire monitoring for 

heavy-duty engines in the HD OBD regulation, and included these 

changes as part of the 15-day notice. However, ARB staff did not add a 

minimum peak torque condition in the OBD II regulation, since staff does 

not believe medium-duty engines merit the same relief as heavy-duty 

engines. Specifically, the heavy-duty engine manufacturers indicated that 

they were concerned that engine accessory loads cycling on and off might 

be a significant factor in proper misfire detection especially at idle and light 

loads where the accessory load is significant relative to the total engine 

load. Further, given the non-vertically integrated heavy-duty industry, the 

engine manufacturers have less knowledge about and control over the 

variety of accessories that are mated to their engines. Medium-duty 

vehicles, however, are dominated by full size pick-up and van models that 

are essentially vertically integrated and have a very limited scope of 

differences in accessory loads and have more knowledge during 

development and calibration about the likely loads. As such, the medium-
31

duty vehicles should be able to be designed and calibrated appropriately 

to ensure robust detection even at idle and low loads while the heavy-duty 

engine manufacturers would likely benefit from a few years of experience 

before expanding monitoring to cover those low load situations. Further, 

the OBD II regulation language already allows disablement of continuous 

misfire monitoring during a small region of high engine speed and very low 

torque for medium-duty vehicles where gasoline misfire detection has 

traditionally been hard to do given the low signal-to-noise ratio in that 

region. Lastly, ARB also agreed that misfire monitoring should be 

disabled during specific conditions that can affect robust detection of 

misfire, and added language in both the HD OBD and OBD II regulations 

indicating allowable disablement conditions as part of the 15-day notice. 

The language provides for disablement in conditions such as those 

suggested by the commenter including infrequent regeneration events. 

However, the disablement is required to be limited only to those periods 

that may “significantly affect engine stability” rather than broad conditions 

such as ‘during an infrequent regeneration event,’ which could include 

many discrete operating conditions that do not have an adverse impact on 

misfire detection.

28.Comment: Our interpretation of the OBD II requirements is that continuous 

misfire monitoring is currently required for all vehicles (passenger cars, 

light-duty trucks, chassis dynamometer-certified medium-duty passenger 

vehicles, and engine dynamometer-certified medium-duty vehicles) 

equipped with combustion sensors, and will be required for all 2016 and 

subsequent model year engine dynamometer-certified medium-duty 

vehicles (even without combustion sensors). Clarifications should be 

made to the language, specifically adding “certified to an engine 

dynamometer tailpipe emission standard” to all references of “mediumduty vehicles. (Mercedes)

Agency Response: The commenter is mistaken. The OBD II regulation 

requires 2016 and subsequent model year chassis dynamometer-certified 

medium-duty vehicles (except medium-duty passenger vehicles) to use 

the same diesel misfire monitoring requirements and malfunction criteria 

as engine dynamometer-certified medium-duty vehicles (section 

1968.2(f)(17.1.6)(C)). Thus, 2016 and subsequent model year chassis 

dynamometer-certified medium-duty vehicles that are part of the phase-in 

would also be required to meet the continuous misfire monitoring 

requirements. 

29.Comment: While we support ARB delaying the NMHC conversion 

efficiency monitoring requirements for catalyzed PM filters (due to lack of 

cost-effective monitoring strategies capable of robustly detecting this 

fault), we believe it should be delayed until 2016, not the proposed 2015, 

to provide engine manufacturers time to develop such a monitor. 

Considering the minimal NMHC emissions impact of the PM filter, ARB 

should review the manufacturers’ progress in meeting this requirement in 

2016 and eliminate this monitoring requirement if manufacturers 
32

determine there is no cost-effective monitoring strategy. A catalyzed 

coating is used on PM filters to prevent damage to the filter due to nonhomogeneous soot-burning under certain conditions. The NMHC 

conversion part is a beneficial side effect but not needed to meet the 

emission standards. Monitoring approaches such as those using 

hydrocarbon sensors are being looked at, but there is currently no suitable 

cost-effective monitoring strategy. Even if the NMHC coating deteriorates, 

this will result in damage to the filter, which will be detected by the PM 

filter monitor if emissions exceed the threshold. (EMA)

Agency Response: ARB disagrees with delaying the requirement to 2016 

and did not make this change. Staff believes such secondary functions 

are not trivial and warrant monitoring to ensure overall effectiveness of the 

emission control system. Staff delayed the requirement to 2015 to give 

manufacturers more time to refine their systems, optimize regeneration 

strategies, and better investigate the impacts of the catalyzed PM filter, 

which will all help manufacturers to develop a robust monitor for this 

NMHC conversion function. Additionally, as part of the 45-day notice, 

ARB staff added test-out provisions for the PM filter NMHC conversion 

efficiency monitor, allowing manufacturers to be exempt from monitoring if 

no fault could cause emissions to exceed the applicable standard and if no 

fault could cause emissions to increase by 15 percent or more of the 

applicable standard. Thus, if the catalyzed part of the PM filter indeed has 

only a minor impact on emissions, the manufacturer would not be required 

to monitor this function.

30.Comment: Regarding the proposed test-out provisions for the PM filter 

NMHC conversion efficiency monitor, the DOC feedgas monitor, and the 

fuel injector tolerance compensation factor monitor, ARB should delete the 

phrase “full useful life” in the HD OBD regulation for consistency in 

language and since this is not applicable for heavy-duty. (EMA)

Agency Response: ARB staff agrees and deleted the phrase “full useful 

life” from these sections in the HD OBD regulation as part of the 15-day 

notice. 

31.Comment: ARB proposed test-out provisions for the EGR catalyst system 

monitor in the HD OBD regulation. ARB should also propose the same 

provisions for medium-duty engines/vehicles in the OBD II regulation. 

(EMA)

Agency Response: ARB staff agrees and included the same provisions in 

the OBD II regulation as part of the 15-day notice. 

32.Comment: While we support ARB delaying the DOC feedgas monitoring 

requirements (due to lack of monitoring strategies capable of robustly 

detecting this fault), we believe it should be delayed until 2016, not the 

proposed 2015, due to technological concerns and given that there are no 

directly measuring sensors or monitoring strategies to meet this 
33

requirement. The development environment that led to ARB delaying the 

requirement in the last rulemaking update is largely unchanged. The 

development of next iteration SCR aftertreatment designs, PM filter 

regeneration strategies and engine NOx control strategies has been 

intense as necessitated by customer fuel economy demands due to high 

fuel prices. Rather than a period of technology stability anticipated by 

ARB, a period of rapid design change has ensued. Since engine out NOx 

strategies, PM filter regeneration strategies, and SCR NOx reduction 

strategies are so intertwined and changing, and since they directly affect 

feedgas monitoring strategies, there is insufficient time to implement 

monitors. (EMA)

Agency Response: ARB does not agree with delaying the requirement to 

2016 and did not make this change. This requirement was originally 

required starting in 2010, was subsequently delayed to 2013, and now is 

delayed to 2015, so manufacturers were aware of this requirement for 

many years. As stated in the Staff Report, the staff delayed the 

requirement to 2015 based on manufacturers’ input that their original 

plans to comply with the requirement based on using monitors for the 

NMHC catalyst NMHC conversion efficiency and/or the SCR NOx 

conversion efficiency were not successful, and thus alternate strategies 

were being sought. Staff believes this monitoring requirement is feasible, 

and at least one manufacturer has already shown it will meet this 

requirement in 2013. Data from some manufacturers suggest that there 

can be a significant impact on tailpipe NOx emissions if the DOC feedgas 

(e.g., nitrogen dioxide (NO2)) generation property is not performing as it 

should, specifically in consuming/destroying as little inlet NO2 as possible 

so that the amount of NO2 relative to NO is good, which makes the SCR 

conversion efficiency higher. Further, based on discussions with emission 

control manufacturers, the catalyst properties that result in good 

downstream NO concentrations are more susceptible to aging and high 

temperature, so the property tends to degrade earlier than other properties

of the catalyst (e.g., NMHC conversion efficiency). Based on this

information, ARB believed monitoring of the feedgas generation property 

should be required earlier rather than later. Discussions with 

manufacturers about monitoring approaches they were investigating and 

other changes that would make the system more tolerant to aging and/or 

make SCR systems less dependent/sensitive to the NO2 levels led staff to 

the 2015 model year timeframe as when these improvements and 

advancements could be incorporated.

Additionally, as part of the 45-day notice, ARB staff added test-out 

provisions for the DOC feedgas monitor, allowing manufacturers to be 

exempt from monitoring if no fault could cause emissions to exceed the 

applicable standard and if no fault could cause emissions to increase by 

15 percent or more of the applicable standard. Thus, if the feedgas 

generation function has only a minor impact on emissions, the 

manufacturer would not be required to monitor this function. Lastly, to the 

extent it is happening, the rapid design changes noted by the commenter 
34

should provide additional opportunity to the OBD engineers to influence 

the design of any redesigned aftertreatment controls to better 

accommodate monitoring based on what they learned through 

development and calibration attempts on the initial designs that fell short. 

33.Comment: While we support ARB delaying the fuel injector tolerance 

compensation factor monitoring requirements (due to technological 

challenges in meeting the requirement), we believe it should be delayed 

until 2016, not the proposed 2015. There are already fuel pressure, 

timing, and quantity monitors that cover all emission-related malfunctions 

associated with the fuel injection system. The magnitude of the 

malfunction criteria for the fuel pressure monitor compared to the 

tolerance compensation is very different. The fuel injector tolerance 

compensation is made in the engine production assembly process and 

parameter values updated for each injector. The major purpose of the 

adjustment is to achieve a smooth engine speed at idle and to get the 

correct performance at high engine load. The tolerance compensation 

can cover one or more compensation parameters for quantity and/or 

timing and the compensation can cover both electrical and hydraulic 

adjustments to get the correct fuel flow characteristics. The parameter 

values used for compensation of the individual injectors adjusts the time 

for the valves and quantity (compensation often in microseconds). The 

compensation for the system can either be fixed values or be based on 

adaptive calculation during engine operation. For the fixed value 

compensation, the parameters will only be able to update with an off board 

workshop tool when replacing one or more injectors. The fixed value 

compensation is based on the fuel injector flow characteristics delivered 

from the injector. The adaptive algorithm calculates the compensation 

needed for keeping the nominal injector characteristics and when 

replacing injectors, the new compensation parameters will be updated 

using an off board workshop tool. For a six-cylinder diesel engine, each 

cylinder is 120 degrees of the flywheel during two revolutions. 

Compensations made in the microseconds will then result in an increase 

or decrease of the fuel injector-related parameters such as timing. A 

normal distribution of the injectors used in production in 99 percent of the 

cases is less than 60 percent of the total possible amount of the 

compensation. Taking that as well as the normal operation window into 

account will result in compensation being close to or less one degree for 

one injector, which is a significantly low adjustment compared to the 

monitoring levels for detecting pressure, timing, and quantity-related 

faults. (EMA)

Agency Response: ARB disagrees with delaying the requirement to 2016 

and did not make this change. As stated in the Staff Report, 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 
35

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. The delay would 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 part of the 45-day notice, 

ARB staff added test-out provisions for this monitor, allowing 

manufacturers to be exempt from monitoring if no fault could cause 

emissions to exceed the applicable standard and if no fault could cause 

emissions to increase by 15 percent or more of the applicable standard. 

Thus, if the fuel injector tolerance compensation factor has only a minor 

impact on emissions, the manufacturer would not be required to monitor 

this function.

34.Comment: Regarding the proposed test-out option for the OBD II NMHC 

catalyst feedgas generation monitoring requirements, the regulation 

language should be changed to consider only NOx emissions, not other 

emissions constituents, when determining if the vehicle is exempt from the 

monitoring requirements. (Mercedes)

Agency Response: ARB disagrees and did not make this change. 

Tailpipe emission standards exist for all criteria pollutants, including NOx, 

NMHC, CO, and PM, and OBD systems in general are designed to detect 

failures that increase any of those pollutants. To meet ambient air quality 

standards, further reductions especially in NOx, NMHC, and PM are 

needed. Accordingly, it would be inappropriate to provide exemptions 

from monitoring to components that have no appreciable increase in NOx 

emissions but do have an appreciable increase in one or more of the other 

criteria pollutants. 

35.Comment: Regarding the proposed test-out option for the OBD II PM filter 

NMHC conversion monitoring requirements, the regulation language 

should be changed to consider only NMHC emissions, not other emissions 

constituents, when determining if the vehicle is exempt from the 

monitoring requirements. (Mercedes)

Agency Response: ARB disagrees and did not make this change. See 

response to comment 34 above for the rationale as to why such a change 

would be inappropriate.

36.Comment: ARB did not change the current malfunction threshold of 2.0 

times the standards for the 2013 model year NMHC catalyst conversion 

efficiency monitor in the HD OBD regulation. Though ARB stated in the 

Staff Report that one manufacturer apparently has been able to meet this 

requirement, the purported success of one manufacturer does not 
36

demonstrate a technological feasible standard, and all manufacturers 

cannot meet this in the 2013 model year. 

Current monitoring technology cannot robustly monitor NMHC converting 

capability at 2.0 times the NMHC standard with IRAF correction factor 

applied without a significant risk of setting false MILs. There is a 

significant risk if manufacturers are required to meet this infeasible 

emissions threshold-based monitoring requirement for reasons as follows:

a.) There is a tradeoff between engine-out NMHC and NOx emissions, 

resulting in higher NMHC levels in order to meet the 0.2 g/bhp-hr NOx 

standard; and

b.) As a result of higher engine-out NMHC levels, oxidation catalysts 

operate at a higher efficiency in order to meet the 0.14 g/bhp-hr NMHC 

standard.

There is no monitoring technology available to meet ARB's emission 

threshold monitoring requirement. SAE Technical Paper 2005-01-3602, 

"Diagnostics for Diesel Oxidation Catalysts," evaluated the feasibility of 

monitoring DOC/DPFs to specific emissions threshold levels and the 

feasibility of both the exhaust oxygen sensor and catalyst temperature 

monitoring approaches. Some of the major findings and conclusions are 

as follows:

a.) DOCs age by shifting light-off to a higher temperature. Exotherm from 

higher temperature-aged and fresh catalysts were indistinguishable at 

higher catalyst temperatures. As a result, the exotherm monitor must 

be operated in a narrow window around the catalyst light-off 

temperature (200 to 400 degrees C).

b.) HC levels in diesel exhaust are too low to generate any appreciable 

exotherm to monitor at the required threshold levels. The DPF 

regeneration event does not provide optimal monitoring conditions 

since temperatures are above the catalyst light-off temperature.

c.) The error stack-up of RTD temperature sensors create significant 

uncertainty for monitoring the DOC/DPF. The uncertainties evaluated 

were due to sensor variability, sensor aging, measuring circuit, sensor 

length and mounting orientation, and analog-to-digital processing. The 

cumulative error for these uncertainties was related to a 3 sigma error 

band that manufacturers must account for in determining threshold 

monitoring capability.

d.) A monitoring approach using oxygen sensors to infer HC conversion 

efficiency by determining the difference in oxygen concentration before 

and after the catalyst was evaluated and found to be less accurate 

than the exotherm monitoring approach for diesels. This was because 

lambda sensor accuracy deteriorated rapidly for lean air/fuel ratios. 

Data was presented to show this effect. An analysis was provided to 

show the uncertainty of HC conversion measurements to be between 

2000 to 3000 ppm during typical diesel lambda values of 1.5 to 2, as 

compared to an exotherm measurement uncertainty of 1000 to 1500 

ppm HC found in the catalyst light-off temperature range.
37

e.) Adding all the noise factors together for a normalized exotherm metric, 

separation between a marginal and threshold catalyst was very poor, 

resulting in false MILs and undetectable failures.

The paper concluded that emissions threshold-based monitoring of the HC 

conversion capability of the DOC was not feasible. On the other hand, 

manufacturers have found an exotherm monitoring approach to be 

feasible for functional monitoring of the DOC.

ARB conveyed some monitoring approaches in the September 11, 2008 

workshop report to justify the current threshold monitor requirement. ARB 

indicated that intermediate levels of catalyst deterioration that cause 

increases in light-off temperature and lower conversion efficiencies can be 

detected. Looking 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), ARB staff believes 

manufacturers will 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. 

Although there is some validity to monitoring catalyst light-off, there are 

also significant limitations. For example, manufacturers must warm-up the 

catalyst as quickly as possible after a cold start in order to minimize HC 

slip. As a result, as stated in the SAE paper referenced above, the 

exotherm monitor must run in a fairly narrow temperature and time window 

around catalyst light-off, making it very difficult to complete the monitor 

and detect a partially deteriorated catalyst, especially when you take into 

account other noise factors that affect catalyst light-off. 

ARB also offered an alternate approach involving monitoring the catalyst 

during cold start by tracking the light-off and/or temperature rise 

characteristics during intrusive actions intended to quickly bring the 

catalyst up to the desired temperature after a cold start. This approach 

has limitations as well, as there are many factors other than the condition 

of the DOC that can affect catalyst warm-up. It should be noted that the 

intrusive actions involved in diesel lightoff strategies encompass a 

multitude of actuators, so the DOC is only one component that generated 

increased heat to the exhaust. Most manufacturers find that the cold start 

component monitor for the DOC can only detect a completely failed DOC 

and hence constitute a functional, not a threshold, monitor. 

ARB also indicated that manufacturers simply work on reducing engineout NMHC levels such that degraded catalysts will have less of an 

emissions effect. However, as previously stated, measures taken to lower 

engine-out NMHC will result in higher engine-out NOx levels. This 

jeopardizes both the ability to comply with the NOx emission standard and 

the ability to meet NOx catalyst monitoring requirements due to the 

resulting higher NOx conversion efficiency that would be needed. 

Manufacturers must strike a fine balance for engine-out NMHC and NOx 
38

levels to ensure that both requirements are met and cannot simply 

jeopardize one to meet the other. 

Even if ARB believes virtually all manufacturers have continued to make 

improvements to regeneration emissions allowing them to meet the 

threshold, EMA still is concerned that the requirements are not technically 

feasible and reasonable. ARB should increase the 2013 model year

threshold to a level (EMA believes 4.0 times the NMHC standard is 

sufficient) such that the monitor would only meet the functional monitoring 

requirements. (EMA)

Agency Response: ARB staff disagrees and did not make any changes to 

the NMHC malfunction thresholds. These comments were already 

addressed in the Staff Report and in the 2009 HD OBD Final Statement of 

Reasons, which ARB will restate here. 

The purpose of interim higher thresholds for monitors such as the NMHC 

catalyst are not to make such monitors gross functional checks in early 

years and stringent threshold checks in later years. Higher interim 

thresholds are intended to start the manufacturer down the path of a 

threshold-type monitor albeit with reduced stringency to provide time to 

refine the monitor over time. Raising the thresholds to ensure solely 

functional checks for every manufacturer would likely lead to 

implementation of cruder diagnostics that would not lend themselves to 

refinement to final thresholds and would not give manufacturers as much 

insight and experience as to what will be necessary to get to the final

threshold. Further, the higher interim thresholds still set a ceiling for the 

emission impact a component can have before it must be monitored, and 

the existing threshold of 2.0 times the standard ensures that 

manufacturers that more heavily rely on the NMHC catalyst will indeed 

need to have a monitor capable of identifying such a level of deterioration. 

While staff understands there are tradeoffs between NOx and NMHC 

emissions, manufacturers have always had to deal with such tradeoffs and 

strike a balance that is best suited to meet all ARB requirements (including 

OBD) and not just to meet tailpipe standards. Those that have chosen 

emission configurations that are less dependent or sensitive to the NMHC 

catalyst will be able to let the catalyst deteriorate further before the need 

for detection of a fault. This is consistent with all OBD monitors in that 

designs that are less sensitive to faulty components are easier to make 

compliant because they can tolerate additional deterioration before the 

OBD thresholds are exceeded. As stated in the Staff Report, contrary to 

the commenter’s position, virtually all manufacturers have moved towards 

higher engine-out NOx emission levels (and consequently, lower engineout 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, 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 
39

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. 

Further, in the Staff Report, staff identified possible monitoring techniques 

for the catalyst including some that, despite the commenter’s position on 

the difficulty of doing so and the cited SAE paper’s conclusion that it is 

infeasible, are currently being used by manufacturers to achieve 

compliance. As stated in the Staff Report, at least one manufacturer has 

already successfully demonstrated the ability to detect a degraded catalyst 

prior to emissions exceeding the 2013 model year thresholds by 

monitoring the exotherm of the catalyst during regeneration events. 

Additionally, as the commenter noted, with this and every other diagnostic, 

there are always other influences that must be filtered out and 

distinguished by use of enable conditions and the control and diagnostic 

algorithms themselves to differentiate properly-functioning components 

from malfunctioning components, including accounting for sensor 

tolerances and errors. 

Lastly, staff also indicated that some manufacturers have indeed taken 

monitoring capability into account when selecting their emission control 

configuration and have chosen solutions which represent the best 

compromise for that manufacturer to comply with all of ARB’s 

requirements. Such choices do involve trade-offs in one area versus 

another but are no different from the types of choices manufacturers 

routinely consider when balancing emissions, OBD, fuel economy, 

durability, drivability, and performance.

HEAVY-DUTY HYBRIDS

37.Comment: ARB should delay the OBD requirements for heavy-duty 

hybrids and align the timing of OBD implementation with that of U.S. EPA

(i.e., require full OBD compliance starting in the 2016 or 2017 model year). 

(EMA)(BAE)(Allison)(PH)(Cummins)

38.Comment: EMA recommends additional time be offered to hybrids to allow 

development of hybrid system and engine technology and the associated 

diagnostic strategies that can comply with the monitoring requirements. 

Specifically, through the 2015 model year (though 2016 for hybrids being 

produced prior to 2013 model year), diesel engine systems used in hybrid 

applications should maintain existing OBD capability and calibrations for 

diesel engine systems with no liability for failure to meet the OBD 

requirements (e.g., detection thresholds, in-use performance ratios). 

Manufacturers would accept responsibility to meet EMD/EMD+ system 

monitoring requirements for NOx aftertreatment, PM filter, fuel system, 
40

and EGR system. There should also be no requirement to demonstrate 

that monitors complete on the applicable FTP/SET for engine/hybrid 

system operation. Engine manufacturers should be allowed to seek 

Agency approval to re-calibrate monitoring strategies if evidence shows 

false failure occurs with existing OBD systems and to implement (different) 

diagnostics for unique engine calibrations that may be developed for 

hybrid use. During the same timeframe, hybrid component/system 

diagnostics should be based on (i) what hybrid manufacturers believe 

necessary for service and (ii) monitoring of other gross systems that 

manufacturers already are monitoring and that are necessary to meet 

performance and other needs. Engine manufacturers should not be 

required to certify diagnostics on the emissions created by a hybrid 

system until the nature of such emissions are better understood and there 

is data to direct appropriate policy on the diagnostics desired.

EMA is concerned that ARB’s proposal will result in little or no use of 

hybrid applications in California, depriving the state of the fuel efficiency 

and other benefits that hybrid technology has to offer. Creating 

requirements in an HD OBD regulation for hybrid drive systems, without 

address certification and other issues, is premature. (EMA)

39.Comment: The current timing will negatively impact the U.S. economy and 

make the U.S. lose the leading edge in heavy-duty hybrids. Many heavyduty hybrid manufacturers are relatively new. There are a lot of OBD 

requirements, but it is challenging for hybrid manufacturers since they 

have no prior experience with OBD. We have to collaborate with engine 

OEMs, but given the challenges for engine OEMs to meet the 2013 

requirements, they will not have time and resources to work with hybrid 

manufacturers. With the 2014 start date, some hybrid manufacturers will 

be forced to leave the market, resulting in thousands of lost U.S. jobs. 

This will have a ripple effect because these OEMs spend lot of money to 

work with the suppliers for this technology. This could lead to a significant 

delay on emissions reduction in the U.S. The U.S. could have been more 

energy independent and a cleaner country. Hybrids account for only one 

percent of the U.S. heavy-duty market. (PH)

40.Comment: Keep in mind that ARB delayed OBD on alternate-fueled 

engines until 2018 and delayed some critical HD OBD requirements for 

small volume diesel manufacturers until 2016 or later. (Cummins)

41.Comment: While we understand the need for and support OBD 

requirements on heavy-duty hybrids, ARB’s proposed 2014 model year 

compliance requirement does not provide adequate lead time to achieve 

that goal and will likely result in a substantial reduction in the numbers and 

types of heavy-duty hybrids in California in the coming years. Alignment 

of the ARB regulations with U.S. EPA will provide time needed to 

adequately address heavy-duty hybrid system effects on OBD system 

performance and perform certification efforts, time needed for the heavyduty hybrid market to respond and comply rather than excluding them 
41

from the California market, and time needed for collaboration between the 

heavy-duty hybrid industry, engine manufacturers, ARB, U.S. EPA, and 

SAE to develop standards and protocols for the hybrids. 

The proposal to not align with U.S. EPA is not supported by adequate 

industry data. ARB’s proposal is fundamentally inconsistent with staff’s 

proposal for alternate-fueled engines (e.g., compressed natural gas), 

which are given until 2018 to comply. There is no rationale for ARB to 

provide four fewer years of lead time for heavy-duty hybrids compared to 

alternate-fueled engines. It should be noted alignment with U.S. EPA will 

still result in an earlier compliance date for hybrids compared to alternatefueled engines. The reasons ARB gives for providing more lead time for 

alternate-fueled engines also apply to heavy-duty hybrids, specifically 

those regarding the role of technology in the heavy-duty industry and that 

HD OBD compliance could lead to discontinued production. The 

distinction made by ARB between heavy-duty hybrids and alternate-fueled 

engines is arbitrary since ARB doesn’t provide any meaningful explanation 

of why alternate-fueled engine compliance is more difficult and requires 

more lead time than hybrids.

Lead time is needed for many reasons. Engine manufacturers are still 

developing HD OBD systems, with the first requirements taking effect in 

the 2010 model year, imposition of some HD OBD requirements for all 

engines starting in 2013, and full HD OBD compliance in 2016. 

Final production HD OBD compliance engines and associated data are 

not yet available to heavy-duty hybrid system manufacturers. The volume 

of heavy-duty hybrids produced annually is small, which limits the ability of 

heavy-duty engine and hybrid system manufacturers to recover the costs 

associated with HD OBD compliance. For example, the total U.S. sales of 

heavy-duty hybrids from 1999 to 2010 were about 11,000 units.

The heavy-duty industry is not vertically integrated like the passenger 

vehicle industry, with multiple manufacturers like chassis manufacturer 

and component manufacturers involved in putting the final configuration 

together. The engine and hybrid system are produced by different and 

independent companies. The engines are designed to comply with the 

OBD requirements in conventional non-hybrid vehicles. Hybrid systems 

are designed to modify the engine duty cycle to achieve reduced fuel 

consumption and lower greenhouse gas emissions, but currently do not 

have the data to demonstrate the certified engines still meet the OBD 

requirements when used with the hybrid systems. It’s even more complex 

with the different heavy-duty system calibrations due to the many different 

types of buses and vocational vehicles where hybrid systems may be 

used, which may affect engine compliance with the OBD requirements. 

ARB’s points appear to be: (1) one-year of lead time is enough to 

transform a non-vertically integrated industry into a vertically integrated 

industry while solutions of the designing challenges of HD OBD-compliant 
42

heavy-duty hybrids are simultaneously achieved; and (2) availability of 

HVIP funding is sufficient to offset costs associated with developing HD 

OBD compliance hybrids within one year lead time. These are all not 

supported by data and by the realities of the current heavy-duty hybrid 

marketplace. ARB’s claim regarding the lack of progress by heavy-duty 

hybrid system manufacturers since 2009 are groundless. The heavy-duty 

hybrid industry, U.S. EPA, and ARB have been working toward solutions 

for HD OBD compliance, including attending an SAE-sponsored workshop 

on August 10, 2012. Data were provided to ARB staff by BAE, Allison, 

and other hybrid propulsion manufacturers. 

ARB did not conduct a proper analysis of the economic impact in the Staff 

Report or analysis of alternatives by not analyzing the impact of 

harmonization with the U.S. EPA requirements on air quality, costs, and 

cost effectiveness of the HD OBD regulation and not analyzing the impact 

of diminished heavy-duty hybrid available in California on California 

entities that operate heavy-duty vehicles (e.g., transit districts, other public 

agencies, private businesses). ARB contradicted itself in the Staff Report 

with regards to heavy-duty hybrid availability in California by stating that 

some hybrid system manufacturers are expected to not expend resources 

for compliance in 2014 and thus not offer hybrids for sale in California 

beyond 2013, but then stating later that they assume all manufacturers will 

comply with ARB requirements when discussing the economic impact.

We would support limiting Hybrid and Zero-Emission Truck and Bus 

Voucher Incentive Project (HVIP) funding to vehicles that comply with 

ARB”s HD OBD requirements if ARB aligns with the U.S. EPA timeline to 

ensure hybrid availability in California. (Allison)(BAE)

42.Comment: Time is needed to establish the relationships between the 

multiple businesses and establish standards that help us do this in single

part certification.

There is currently only one engine manufacturer that makes engines 

certified for use on transit buses in North America and are focused on 

ensuring a successful launch of HD OBD across their non-hybrid products. 

(Source: Frost and Sullivan, Mary 2010 Report) – so small (compared to 2 

million light-duty hybrids over the same period) that engine manufacturers 

have not prioritized hybrid approved engine calibrations. Data from the 

American Public Transit Association 2011 Public Transit Vehicle Database 

dated October 2011 shows the volumes of CNG and hybrid purchases in 

California from 2006 to 2011, with 225 hybrid purchases (zero hybrids in 

2011) versus 1544 CNG purchases, which does not support ARB’s focus 

on hybrids versus alternate-fueled engines. So there is need for a similar 

delay for hybrids. 

The transit bus industry is not capable of vertical integration in the future, 

since all North American transit bus OEMs are integrators with no direct 

ties to engine OEMs. Thus, if ARB’s goal is for vertical integration, the 
43

transit bus companies should be exempt from HD OBD requirements until 

vertical integration is feasible and imminent.

One of ARB’s points is that engine manufacturers, who have spent last 4 

years trying to respond to the newly imposed HD OBD requirements for 

their conventional engines, would have also allowed time and resources to 

support and evaluate interactions with all hybrid systems and make 

necessary changes in their control systems to secure an additional 1% 

hybrid market share. These are all not supported by data and by the 

realities of the current heavy-duty hybrid marketplace. ARB’s claim 

regarding the lack of progress by heavy-duty hybrid system manufacturers 

since 2009 are groundless, as evidenced by the numerous changes 

proposed this year to section 1971.1, which includes for the first time a 

definition for hybrid vehicle. BAE Systems provided detailed information 

to ARB in May and December of 2011 about their current system 

diagnostics and service manual but have yet to receive any feedback from 

ARB regarding their acceptability other than the proposed HD OBD 

regulation modifications. Since it’s been over 8 months since the last 

submission, it is unlikely ARB will be able to devote the resources 

necessary to work with manufacturers to certify 2014 model year hybrid 

OBD systems, even if it were feasible for manufacturers to attempt 

certification. 

Regarding ARB’s belief that funds from the HVIP are sufficient financial 

incentives to accelerate OBD compliance, we disagree – the HVIP 

program will not incentivize heavy-duty hybrid OBD compliance and will 

not drive vertical integration of heavy-duty hybrid solutions. BAE agrees 

with ARB’s statements on the ARB webpage for the HVIP program that 

heavy-duty hybrids are important and supports the goal of HD OBDcompliant hybrids, but we need more lead time. (BAE)

43.Comment: A heavy-duty vehicle typically has external sources for the 

chassis, transmission, brake system, body, specialized auxiliary 

equipment, and hybrid system components. The heavy-duty vehicle may 

just be a “cab chassis” as it leaves the first OE assembler (powertrain, 

chassis, cab) before further assembly at a body builder (upfitter) to add 

more equipment and the specialized body for a particular work truck, then 

may go through a second upfitter before sale. The degree and nature of 

the highly-proliferated, highly-customized heavy-duty vehicle industry has 

no parallel in passenger vehicles. 

The proposed rule will likely result in negative economic impacts in 

California for the coming years. (Allison)

Agency Response to Comments 37-43: ARB disagrees with further 

delaying of the requirements as the U.S. EPA has done, and did not make 

the changes. Regarding the comment requesting three more years of 

lead time without having to meet OBD system requirements, ARB 

disagrees that further lead time is warranted and would not lead to more 
44

effective systems. The requested relief includes no requirement to 

monitor any of the hybrid system components that can affect emissions or 

other diagnostics, no requirement for the certified engine OBD system to 

remain compliant and continue to comprehensively monitor all of the 

engine emission controls after it has been mated with a hybrid system, 

and no requirement for any of the engine OBD system monitors to even 

be able to run and make a pass/fail decision anymore. Absent such 

fundamental requirements, the system could not be relied upon to identify 

engines/vehicles in need of emission-related repair even in cases where 

gross emission faults exist. Further, given many of these vehicles also 

use ARB incentive monies designed to accelerate the introduction of clean 

technologies to help offset the purchase of a heavy-duty hybrid, changes 

that would allow otherwise compliant engines to become less capable in 

detecting emission-related faults would be inconsistent with ARB’s clean 

air goals.

Regarding the comment that the one year delay will not provide enough 

time given hybrid manufacturers have little experience with OBD and 

engine manufacturers will still be devoting most of their resources to 2013 

engine OBD systems and have little time to support hybrid system 

manufacturers, ARB disagrees that further delays will resolve the issues. 

As noted previously, the requirements for the 2013 model year have been 

known to industry for many years and even with that, little improvement 

has been made in understanding the OBD implications of interactions 

between the engine and hybrid. Further, the hybrid systems will likely 

continue to be a very small portion of total engine/vehicle sales and as 

such, will continue to struggle to get large levels of resource support from 

the engine manufacturers regardless of the start date. Because of this, 

ARB expects that the hybrid system manufacturer will need to do a 

significant share of the work to not only implement OBD on its own 

components but also to investigate which engine diagnostics are 

adversely affected by the addition of the hybrid system. This task would 

include things like identifying key areas of engine operation that are 

significantly altered or eliminated by the addition of the hybrid system, 

collecting data on whether engine system diagnostics are still running and 

completing as expected, and even implanting faults in the major engine 

emission controls and verifying they are still detected properly. While 

these tasks will likely require interaction with the engine manufacturer, 

each could be largely accomplished by the hybrid system manufacturer to 

understand the nuances of each hybrid system and bring to light issues 

which then need to be resolved by the hybrid system manufacturer, the 

engine manufacturer, or even jointly. With the current regulatory structure, 

should it be necessary, these issues could qualify for deficiencies and 

further work to better quantify and resolve them could spill over into 

subsequent model years.

Regarding comments that the rule will have negative impacts to the 

economy and leading role the U.S plays in heavy duty hybrid vehicles, 

ARB disagrees. In order to secure and maintain a leading role in the 
45

hybrid arena and have products that meet or exceed the needs of all 

hybrid stakeholders, (e.g., manufacturers, vehicle operators/operators, 

those subject to unhealthful air quality, government), hybrid vehicles need 

to be as clean and efficient and have the most capable OBD systems as 

possible. The commenters’ proposals to further delay the requirements 

put off inevitable and necessary development to maintain the existing 

leading position the U.S. heavy duty hybrid sector may have. The 

regulatory requirements as adopted put the affected stakeholders on a 

reliable path to have more capable hybrids introduced into the field as 

soon as possible. While this may cause some near-term tradeoffs and 

changes in product offerings, ARB expects they will be offset by the longterm gains and success. 

ARB also disagrees with the commenters who state that the rationale for 

delaying OBD on heavy-duty alternate-fueled vehicles should also apply to 

heavy-duty hybrid vehicles. Staff originally delayed the implementation of 

OBD systems on heavy-duty alternate-fueled vehicles based on past lightduty experience where it was common practice that an alternate-fueled 

vehicle was produced by converting an OBD compliant stoichiometric 

spark-ignited gasoline vehicle to a similarly operated alternate-fueled 

vehicle that relied on the same emission controls and operating strategies. 

Although such a conversion could adversely impact the emission level that 

certain major monitors were designed to detect faults at (e.g., no longer 

detect EGR low flow faults before 1.5 times the tailpipe standards but 

rather at the same level of low flow but with a corresponding higher 

tailpipe emission level), the system was still otherwise predominantly fully 

functional in detecting all required faults. However, staff subsequently 

made changes to accelerate implementation of full OBD systems on 

alternate-fueled engines as early as lead time would allow upon staff 

gaining further experience with typical heavy-duty alternate-fueled 

conversions which can include dramatic changes to the emission controls 

and operating strategies (e.g., changing compression-ignition engines to 

spark-ignition engines, changing lean diesel operation and associated 

emission controls to stoichiometric alternate-fueled operation with different 

emission controls). Such significant changes mean the staff’s previous 

assumptions that the original gasoline or diesel engine OBD system would 

mostly be fully functional were no longer valid and, accordingly, staff took 

action to move to full OBD system implementation as early as possible. 

Likewise, hybrid conversions generally result in dramatic changes to the 

in-use engine operating conditions that can severely disrupt the standard 

emission controls and strategies as well as cause substantial issues with 

the OBD system that is already present on the engine. Given the potential 

for much larger detrimental impacts to existing certified systems, 

combined with ARB financial support for purchase of the vehicles, it would 

have been inappropriate to exempt hybrid vehicles from maintaining 

existing OBD system capability for an extended period of time. 
46

Regarding the comments that transit buses are not vertically integrated 

and thus warrant additional relief, staff does not agree that transit buses 

should be exempt from meeting the HD OBD requirements. ARB’s goal is 

not to have all products vertically integrated but rather to have the engine 

and hybrid system properly designed to be compatible with each other to 

have the resultant system comply with all emission requirements including 

OBD. With respect to OBD, transit buses are no different from any other 

heavy-duty hybrid or non-hybrid application and thus will require a similar 

approach as other applications to implement a full OBD system for the 

engine and hybrid system. Transit buses do, however, often operate in 

densely-populated areas that are economically and environmentally 

challenged, and such areas would likely benefit the most from fully 

compliant systems that minimize in-use emissions.

Concerning the comment that ARB provided only one year of lead time to 

implement OBD systems on hybrid vehicles, this statement is incorrect 

since the HD OBD regulation has required monitoring of the hybrid 

components since regulation was first adopted in 2005 and these issues 

have been discussed at length during the 2009 HD OBD rulemaking 

update. Regarding the comment that it is ARB’s belief that the availability 

of HVIP funding is sufficient to offset the costs associated with developing 

OBD systems on hybrids, ARB never claimed this but believes that the 

HVIP funds, intended to accelerate the introduction of clean technologies, 

should not be used to support hybrid systems that lead to increased in-use 

emissions. Funding should instead be used to accelerate introduction of 

technologies that offer benefits above and beyond what is required by 

emissions standards, which include greenhouse gas standards, criteria 

pollutant tailpipe standards, and OBD requirements. Further, while the 

commenter denies ARB’s claim of the heavy-duty hybrid manufacturers’

lack of progress in meeting the OBD requirements since 2009, ARB notes 

that the issues identified back in 2009 as needing work and resolution to 

make hybrid systems compatible with OBD systems do not seem to be 

any closer to being resolved today. Concerning the commenters’ 

indication that ARB contradicted itself in the Staff Report by stating heavyduty hybrid manufacturers are not expected to expend resources to 

comply in 2014 and then stating later that they assume all manufacturers 

will comply, the commenter misunderstood the language in the Staff 

Report in that we never asserted that we believe all hybrid manufacturers 

will comply with the OBD requirements in 2014. 

Lastly, ARB disagrees with the comment that ARB’s goal is for vertical 

integration of the industry. ARB’s goal is to have hybrid vehicles that have 

maximum efficiency and meet all of the ARB standards (including tailpipe 

standards and OBD requirements) to ensure low emissions in-use. While 

ARB does believe that this will likely require more interaction between 

hybrid system manufacturers and engine manufacturers, ARB does not 

believe that this necessitates vertical integration of the heavy-duty 

industry. A significant amount of integration already occurs between 

hybrid system and engine manufacturers, though this likely focuses solely 
47

on meeting acceptable driveability and performance requirements and 

without a corresponding level of effort dedicated to ensuring the combined 

system meets tailpipe standards and OBD requirements.

OTHER REQUIREMENTS

44.Comment: ARB’s proposed revised definition of “diagnostic or emission 

critical” in the HD OBD and OBD II regulations appears to include all or 

most sensors and other potential devices used in connection with the 

engine, and potentially will require a proliferation of calibration identifiers 

(CAL IDs) and calibration verification numbers (CVNs). The language is 

ambiguous and raises concerns that more CAL IDs and CVNs may be 

required. The definition should be revised to minimize the number of 

controllers required to report CAL IDs and CVNs, which seems to be the 

ARB staff’s intent in the Staff Report, and should state not only what is 

“diagnostic or emission critical” but also what is not, which may require 

specific exceptions be written in. (EMA)

Agency Response: The commenter is mistaken regarding the OBD II 

regulation – ARB did not propose any revisions to the definition of 

“diagnostic or emission critical” in the OBD II regulation as part of this 

rulemaking, and thus did not make any changes in response to these 

comments. However, for the HD OBD regulation, ARB agrees with the 

commenter and made additional revisions to the definition of “diagnostic or 

emission critical” to address the concerns as part of the 15-day notice. 

ARB staff intends to propose similar changes to the OBD II regulation at 

the next OBD II biennial review.

45.Comment: In the OBD II regulation, the PM filter frequent regeneration 

monitor and the PM filter incomplete regeneration monitor should use the 

denominator specifications requiring at least 500 cumulative miles of 

vehicle operation, the same as the other PM filter monitors. (Mercedes)

Agency Response: ARB disagrees and did not make this change. The 

OBD II regulation currently requires manufacturers to submit alternate 

criteria to increment the denominator for the PM filter frequent 

regeneration monitor and requires manufacturers to increment the PM 

filter incomplete regeneration monitor if, in addition to the general 

denominator criteria, a regeneration event is commanded for at least ten 

seconds. The commenter believes that the requirements should be 

streamlined to require all PM filter-related monitors to use the same 

denominator criteria, though they did not indicate the specific reason for 

the streamlining. The PM filter incomplete regeneration monitor is 

supposed to detect faults “when the PM filter does not properly regenerate 

under manufacturer-defined conditions where regeneration is designed to 

occur”, and thus should require that the system is commanding 

regeneration to occur in order to determine if a fault is present. The PM 

filter frequent regeneration monitor detects faults that cause regeneration 

to occur more frequently than normal, and thus should not be tied to a 
48

denominator that increments when at least 500 cumulative miles of vehicle 

operation have occurred, which is the estimated time a regeneration 

event is expected to occur once. Thus, ARB staff believes the current 

denominator criteria for both monitors are appropriate. 

46.Comment: The HD OBD and OBD II regulations should be modified to be 

consistent with the SAE J1939-73 standard language that existed since 

the late 1990s for the reporting of J1939 test results. Specifically, if the 

OBD system fault memory is cleared in a J1939 system, the test results 

should report either zero for the test results and test limits or “test not 

complete”, and starting in 2016, the test results should report “test not 

complete”. (EMA)

Agency Response: For the HD OBD regulation, ARB agrees and made 

the changes as part of the 15-day notice. For the OBD II regulation, ARB 

did not make the changes, since this issue only applies to engines or 

vehicles using the SAE J1939 protocol and that protocol is limited to use 

only on heavy-duty diesel engines.

47.Comment: We are concerned about the proposal in the OBD II regulation 

to require medium-duty vehicles certified on the chassis dynamometer to 

meet the monitoring requirements and malfunction criteria applicable to 

passenger cars, light-duty trucks, and medium-duty passenger vehicles 

starting in the 2016 model year. We are concerned this will not be 

feasible for some monitors due to the significant increase in stringency of 

the requirement, particularly for aftertreatment monitoring. Chassis dynocertified medium-duty vehicles use similar emission control technology as 

engine dyno-certified medium- and heavy-duty vehicles. In fact, the diesel 

engines used in medium-duty vehicles are most often used in enginecertified medium- and heavy-duty applications. So they will be faced with 

the same monitoring feasibility issues as their engine-certified 

counterparts. There is no reason chassis-certified vehicles then should be 

subject to more stringent malfunction criteria than engine-certified 

vehicles. Among the advantages of chassis dyno-certified medium-duty 

vehicles is the ability of ARB to readily conduct confirmatory testing of 

compliance with the OBD requirements. But this proposal would deter 

manufacturers from certifying medium-duty vehicles on the chassis 

dynamometer in the future. ARB should instead require chassis dynocertified medium-duty vehicles to meet the same requirements as engine 

dyno-certified medium-duty vehicles. (EMA)

Agency Response: ARB disagrees and did not make the changes. 

Gasoline and diesel medium-duty vehicles are subject to less stringent 

chassis dynamometer tailpipe emission standards than light-duty 

passenger cars and trucks. Further, the chassis dynamometer test cycles 

exercise the engines over a smaller range of speed and loads compared 

to the engine dynamometer test cycles. As such, the OBD II threshold, 

which is a multiplicative factor applied to the tailpipe standard, is also 

correspondingly less stringent than the OBD threshold for light-duty 
49

passenger cars. Additionally, the OBD II regulation currently requires

manufacturers of diesel engines who choose to certify to the chassis 

standards to submit a proposal for equivalent OBD thresholds to those 

defined for engine dynamometer-certified products. At the time that 

language was created, there were no diesel medium-duty products 

choosing the path of chassis certification. However, since that time, 

virtually every diesel medium-duty product has switched to chassis 

certification, and staff has obtained knowledge about the fault detection 

capabilities of these systems. Based on the past few years of certification, 

several manufacturers have already demonstrated fault detection 

capability at the equivalent multiplicative factor to which the light-duty 

passenger cars are subject and this is more telling about stringency and 

feasibility than arguments about the relative stringency of chassis based 

detection to engine based detection. As such, the same relative 

thresholds are both feasible and appropriate to ensure emission-related 

faults are detected in a timely manner to minimize excess emissions inuse.

48.Comment: EMA requests that ARB either remove infrequent regenerationbased monitors from readiness groups or create a new readiness group to 

capture all infrequent regeneration-based monitors. EMA is concerned 

that these monitors, which run only once every 300-500+ miles, are 

causing properly functioning vehicles to frequently appear “not ready” for 

I/M testing, which causes problems for inspection facilities, end users, and 

manufacturers. While various monitors depend on PM filter regeneration 

to complete, PM filter regeneration occur at intervals of hundreds or 

thousands of miles, or tens to hundreds of hours so that these monitors 

also take similarly long to complete. Additionally, Infrequent monitors are 

spread among several readiness groups, so it may take a long time for all 

(or all but one) readiness groups to complete after code clearing events, 

which may occur when the control module is reprogrammed or a vehicle 

serviced at a repair facility prior to an inspection. Jurisdictions with I/M 

programs that currently test medium-duty diesel vehicles typically adopt 

the gasoline vehicle practice of allowing zero or one “not ready” monitor 

readiness group to pass. As a result, properly functioning diesel vehicles 

in California are at risk of failing inspection, especially after codes are 

cleared. If a vehicle fails, the customer may be inconvenienced and 

frustrated by such a failure and by the steps necessary to address the 

“failure” and prepare the vehicle for inspection, including unnecessary time 

and expense devoted to “solving” the problem. For example, a customer 

who has completed an OBD repair may still fail I/M and may be told to 

drive the vehicle for a certain number of miles or hours before returning to 

the I/M station. This may be repeated if insufficient miles or hours have 

accumulated to have all monitors pass readiness. (EMA)

Agency Response: ARB disagrees with separating out the infrequent 

regeneration-based monitors and did not make the changes. Section 

1971.1(h)(4.1) requires manufacturers to store whether or not primary 

emission controls on the engine have been monitored by the OBD system 
50

since the system’s fault memory was last cleared. These data constitute 

the “readiness groups” referenced in the comment. The data are

important for users of the OBD system (e.g., repair technicians and 

inspectors) to know whether the OBD system has judged specific 

emission controls as passing, failing, or condition currently unknown. 

Eliminating individual emission control readiness data or combining the 

data into one indicator will specifically hinder the ability to learn that the 

emission control’s level or performance is currently unknown. It is true 

that monitors for some emission controls may operate only once every 

couple hundred miles, and thus readiness is more likely to be unset for a 

period of time after the memory has been cleared (e.g., after repair work is 

done). However, eliminating the data because of how it might be misused 

in a future Inspection and Maintenance (I/M) program is counterproductive 

and unnecessary.

Jurisdictions throughout the U.S. that have I/M programs based on OBDsystem inspections have the responsibility to understand how OBD 

systems work and the nature of the data they produce. Further, it is these 

jurisdictions that have the authority, subject to U.S. EPA approval, to 

determine their own procedures and policies concerning pass, fail, and 

system readiness requirements. Each jurisdiction develops these rules 

and procedures with the understanding that it needs to balance inspection 

effectiveness with readiness criteria that will not be overly burdensome for 

the vehicle operator to satisfy.

In this light, the U.S. EPA has already worked with jurisdictions (including 

California) that use OBD-based inspections for medium-duty diesel 

vehicles, and with vehicle and engine manufacturers, to address the very 

issues raised by EMA through proper use of the data as opposed to its 

elimination as is suggested in the comment. The guidance, titled “Best 

Practices for Addressing OBD Readiness in IM Testing of Diesel Vehicles 

Under 14,000 Pounds Gross Vehicle Weight Rating” was published by the 

US EPA on March 7, 2013, and is available online:

(e.g., www.obdclearinghouse.com/index.php?body=get_file&id=1612). 

No jurisdiction in the U.S. currently has an OBD-based inspection and 

maintenance program for heavy-duty vehicles (greater than 14,000 lbs); 

however, similar principles and concepts can and would be applied should 

such programs be implemented in the future.

49.Comment: The service information requirements in the HD OBD regulation 

should be deleted since ARB adopted amendments to section 1969 in 

2006 incorporating heavy-duty engine service information requirements 

and since it’s inappropriate for two separate ARB regulations to separately 

promulgate rules and separately administer them on the same topic.

(EMA)

Agency Response: ARB agrees and deleted the service information 

requirements from the HD OBD regulation as part of the 15-day notice.
51

50.Comment: The diesel medium-duty and heavy-duty OBD timing for 

production engine/vehicle testing of monitoring requirements should be 

extended from the proposed six months after the start of engine or vehicle 

production to nine months in order to address manufacturers’ real 

concerns and challenges in getting testing completed. Concurrently, the 

retroactive deficiency allowance should be extended from six months to 

nine months after the start of production. Such changes are necessary 

because of the unique nature of diesel engines and systems, with diesel 

OBD systems often having twice as many MIL-illuminating fault codes to 

demonstrate (up to 500+ fault codes) compared with gasoline engines, 

and many diesel monitors requiring extended vehicle operation and/or 

extended soak periods to detect faults. Engine manufacturers typically 

have been unable to complete testing within the six month requirement, 

with staff often extending the testing periods. It is important to 

manufacturers that issues identified beyond the six-month period be 

allowed to be considered for retroactive deficiencies. (EMA)

Agency Response: ARB disagrees and didn’t make the changes. One of 

the main goals of the production engine/vehicle testing of monitoring 

requirements is for manufacturers to find problems and implement fixes as 

early as possible to minimize the number of engines/vehicles with these 

problems on the road. The problems found during this testing were never 

meant to make it to production, and finding them early in the model year 

would minimize any adverse impacts. Extending the deadline for this 

testing would result in manufacturers finding problems too late to 

effectively achieve this. Extending to 9 months would essentially allow the 

entire model year to be built before the problem was discovered and 

reported to ARB, which greatly undermines the intent to find problems 

early enough to correct them, if necessary, during the model year. 

51.Comment: For the HD OBD regulation, EMA proposes that deficiencies 

identified in 2010 (or later) be allowed to be carried over for three years 

(instead of the currently required two years) without additional EO 

approval, with the option of one additional year if substantial hardware 

changes are necessary, and with the allowance extending into the 2013 

and 2014 model year only. This issue deals with deficiencies that apply to 

a particular technology and where further refinement is needed in order to 

make the technology fully compliant. The extra year would allow 

manufacturers to achieve compliance without having the “hard stop” of 

having to pull the product out of production. (EMA)

Agency Response: ARB staff agrees with extending the allowance for 

deficiencies first identified in 2010 or 2011, and revised the HD OBD 

regulation as part of the 15-day notice.

52.Comment: The medium-duty OBD II NOx enforcement threshold (+0.2 

additive) in the OBD II enforcement regulation (section 

1968.5(b)(6)(A)(ii)(d)) are significantly tighter than the HD OBD threshold 
52

(2 times multiplier) for the same malfunction threshold (section 

1971.5(b)(6)(A)(ii)(a)). Using a standard of 0.2 as an example, the OBD 

threshold is 0.2+0.3=0.5, with the medium-duty OBD II enforcement 

threshold being 0.5+0.2=0.7 and the HD OBD enforcement threshold 

being 0.5x2=1.0. The medium-duty OBD II NOx enforcement threshold 

should be changed to +0.4 above the malfunction threshold, which is still 

tighter than the HD OBD threshold but will allow more in-use separation 

and better measure of a non-conforming system. (EMA)

Agency Response: ARB staff disagrees and did not make the change. 

Medium-duty vehicles have been subject to OBD requirements since 1997 

while OBD requirements for heavy-duty engines started in the 2010 model 

year. So while both classes have relatively the same time with newer 

emission control technologies, the medium-duty sector is much further 

along in OBD system capability as well as have much more constrained

applications (as opposed to the horizontally-integrated nature of the 

heavy-duty industry) that make it more likely for manufacturers to correctly 

calibrate emission-threshold-based OBD monitors on medium-duty 

vehicles versus their heavy-duty counterparts. 

15-DAY COMMENTS

DEFINITION OF “EMISSION STANDARD” AND “NONCONFORMING OBD 

SYSTEM”

53.Comment: ARB’s proposed redefinition of the term “emission standard” 

does not conform to any specific federal law or regulation, and so is 

unlawful. ARB asserts that its proposal to redefine “emission standards” –

solely “for the purposes of HD OBD compliance” – is consistent with dicta 

from a U.S. Supreme Court case, EMA v. SCAQMD, 541 U.S. 246 (2004). 

But ARB’s position reflects a fundamental misunderstanding of the 

SCAQMD case, which did not alter the definitions of terms found in any 

federal laws or regulations. In SCAQMD, the Court was interpreting the 

CAA’s provision broadly preempting states from adopting or enforcing 

“any standard relating to the control of new motor vehicles or new motor 

vehicle engines...” CAA § 209, 42 U.S.C. § 7543. The issue before the 

SCAQMD court was whether or not state restrictions on the purchase of 

certain vehicles by fleet owners constituted “standards related to the 

control of emissions.” The respondent in the case, South Coast Air 

Quality Management District, took the position that the phrase “standards 

related to the control of emissions” referred only to emission-related sales 

restrictions imposed directly on vehicle/engine manufacturers. The 

SCAQMD Court ultimately held that the phrase “standards related to the 

control of emissions” does apply to state purchase restrictions, and 

therefore such restrictions are subject to the preemptive effect of CAA § 

209. ARB’s attempt to use the SCAQMD case as support for its proposed 

change to California’s definition of “emission standards” is faulty. The 

CAA § 209 phrase “standards related to the control of emissions,” on its 
53

face, has a different and broader meaning than the term “emission 

standards” in the California HSC. Congress sought to preempt states from 

adopting or enforcing any sort of measure with any connection to motor 

vehicle emissions, and therefore inserted an expansive phrase into CAA § 

209 to suit that specific purpose. The fact that the Court gave this 

broadly-worded phrase an appropriately broad meaning, in the context of 

an express preemption provision, does not mean that the Court imparted a 

new definition to the meaning of “standard” everywhere that it appears in 

the CAA. (EMA)

54.Comment: The proposed additional revisions to the terms “emission 

standard” and “nonconforming OBD system” are invalid under California 

law, arbitrary and capricious, and clearly violates the directly applicable 

ruling of the California Superior Court in EMA vs. CARB (Case No. 34-

2010-82774), which held that OBD sensor malfunction criteria are not 

emission standards and cannot serve as a basis for mandatory engine 

recalls under California HSC Section 43105. So they should not be 

approved. (DTNA) 

Agency Response to Comments 53-54: See the agency response to 

comments 11-12 above.

55.Comment: ARB’s position here relies on the Court’s in-passing 

statements to the effect that CAA “standards” encompass “some other 

design feature related to the control of emissions” in addition to numerical 

limits on the emissions of pollutants. While such statements make sense 

in the context of the Court’s review of the broadly-worded phrase in CAA § 

209, they are nothing more than dicta outside of that context. The 

SCAQMD Court was not asked to determine the technological scope of 

the term “emission standards” or any comparable term in federal laws or 

regulations, nor was it asked to decide whether OBD requirements are 

“emission standards” for all purposes under federal laws and regulations. 

Such questions were simply not before the Court, and not briefed by the 

parties in SCAQMD; yet ARB seeks to seize on this dicta and use it as the 

basis for changing its regulations. Supreme Court dicta is not the 

equivalent of a federal statute or regulation, and so is not a proper basis 

for redefining terms under the California HSC in any event. Thus, ARB’s 

effort to redefine terms to meet its own agenda – an agenda to grant to 

itself expanded recall authority beyond that intended by the California 

legislature -- is inconsistent with HSC section 39601(b) and, as a result, 

invalid. In reality, ARB’s pending proposal to redefine statutory terms is 

nothing more than an exercise in bootstrapping. ARB wants the authority 

to order mandatory engine recalls if OBD sensors do not trigger MILs 

when various OBD sensor malfunction criteria are exceeded. But ARB 

faces a fundamental problem in that regard due to the fact that mandatory 

engine recalls are only available under HSC section 43105 when there 

has been a violation of emission standards, and OBD sensor malfunction 

criteria are not “emission standards,” as defined under California law. To 

“fix” that, ARB seeks to invent for itself a new and expanded definition of 
54

“emission standard,” which ARB hopes will be broad enough to 

encompass OBD sensor malfunction criteria. In that way, ARB can 

attempt to bootstrap itself into a position of unilaterally-expanded authority 

to compel mandatory engine recalls. While ARB’s attempted power grab 

is certainly bold and transparent, it is nonetheless invalid. A basic 

requirement to any attempt by ARB to redefine terms is that ARB “conform 

those definitions to federal laws and rules and regulations.” (HSC 

§39601(b).) In its eagerness to expand its recall authority unilaterally, ARB 

failed to adhere to that basic requirement. As a result, the proposed 

amended definitions are invalid and should not be approved. (EMA)

Agency Response: Please see the agency response to comments 9-12

above. As stated there, the Supreme Court’s interpretation of what is a 

standard related to the control of emissions (i.e., an emission standard) 

was at the heart of its decision in EMA v. SCAQMD. The Court’s 

interpretation of that term, in the Court’s own words, was fully consistent 

with Congress’ use of the term throughout Title II of the CAA. ARB was 

fully within its authority to conform the definition of emission standard to 

the definition of the term as used in Title II of the CAA, as interpreted by 

the Supreme Court. 

ARB disagrees with the commenter that ARB only has authority to take 

corrective action, including recall, for violations of emission standards. 

Although EMA prevailed on this question before the lower court in EMA v. 

ARB, that decision is presently undergoing appellate review, and the 

appellate court will consider de novo ARB’s arguments that it has authority 

to fully enforce its regulations. No injunction or stay has been put into 

place by either the lower court or the appellate court that prevents ARB 

from prudently amending the HD OBD and OBD II regulations to ensure 

their enforceability. In amending the regulations, ARB reserves its right in 

the de novo review in the appellate court to pursue all arguments raised in 

the lower court as to its authority under the Health and Safety Code to fully 

and completely enforce its regulations pursuant to the directives of the 

Legislature. 

56.Comment: ARB claims that it is redefining the term “emission standard” 

solely “for the purposes of HD OBD compliance” (solely “as it applies to 

OBD compliance and the remedies provided for in the Health and Safety 

Code for noncompliance”), which presumably means that the existing 

definition of “emission standard” as codified at HSC section 39027 will 

apply for all other purposes. ARB’s provisional authority under HSC 

section 39601(b) to redefine terms does not include the authority to give a 

different meaning to the same statutory term solely to suit ARB’s 

fluctuating purposes. To the contrary, ARB’s effort to ascribe a different 

meaning to the same statutory term solely for the purpose of 

manufacturing expanded recall authority for itself is nothing short of 

arbitrary and capricious, and is far outside the scope of ARB’s delegated 

authority. Consequently, ARB’s proposed exercise in semantic 

gamesmanship is, again, unlawful and invalid. (EMA)
55

Agency Response: Please see the agency response to comments 11-12

above. Contrary to the commenter, nowhere in the regulation or 

supporting documents does ARB claim that the revised definition will only 

apply to the HD OBD regulation. As stated above, the definition has been 

initially included as part of the OBD regulation because of issues and 

concerns raised by stakeholders regulated by the OBD regulations, and 

the fact that it has long-planned to reopen the HD OBD and OBD II rules 

for amendment in 2012. ARB’s intent in specifically applying the revised 

definition to the two OBD rules was to prudently act to make it clear that 

the regulations are fully and completely enforceable under California law. 

As stated in the agency response to comment 11-12, ARB staff will in the 

near future be bringing to the Board for its consideration a proposal that 

the revised definition be applicable to other motor vehicle regulations. 

57.Comment: ARB’s proposal to redefine the term “emission standard” solely 

for the purposes of HD OBD compliance and enforcement is a transparent 

attempt to short-circuit the Superior Court’s ruling. It is an attempt that is 

bound to fail. No amount of definitional gymnastics can contort a 

malfunction criterion for an OBD sensor into an “emission standard” as 

properly defined under current California or federal law. Thus, ARB’s 

latest and last-minute revisions to its HD OBD program should be 

recognized for what they are - - a bald attempt to disregard the directly 

applicable ruling of the California Superior Court, and an even more 

transparent grab for expanded recall authority that ARB is not entitled to 

under the controlling California statutes. ARB should not continue with 

this misguided course of action, as its only result will be additional legal 

proceedings. (EMA)

Agency Response: Please see Response to Comments 9-12 above and 

56. As stated, ARB has appealed the decision of the lower court, and the 

appellate court will review that decision de novo. While continuing to 

reserve all arguments raised in the lower court, ARB determined that the 

most prudent action was to amend the regulation expeditiously to make it 

clear that OBD systems are emission standards and fully enforceable 

under California law. ARB took such action pursuant to authority 

expressly granted to it under HSC sections 39010 and 39601(b). ARB 

was not precluded from taking such action as EMA has not pursued, and 

no court has granted, any injunction prohibiting ARB from attempting to 

cure any perceived defects identified by the lower court regarding the 

ARB’s authority. Regarding EMA’s claims of definitional gymnastics, the 

definition adopted by the Board fully conforms to the Supreme Court’s 

interpretation of the meaning of standard as used by Congress in Title II of 

the CAA. 
56

HEAVY-DUTY HYBRIDS

58.Comment: ARB should delay the implementation of the 2014 single party 

certification requirements and OBD compliance for heavy-duty hybrid 

transit buses to coincide with the EPA implementation in 2016/2017. The 

2014 requirement means GILLIG will be unable to provide fuel efficiency 

hybrid transit buses to California transit properties. GILLIG, which 

purchases engines from Cummins and hybrid systems from Allison and 

BAE, has hybrid suppliers that are uncertain if their OBD systems will 

meet ARB requirements in 2014. GILLIG is unable to obtain a 

commitment from any of our suppliers to carry the single party certification 

for the combined heavy-duty engine/hybrid powertrain system 

combination. If we continue down this path, California transit properties 

will be forced to purchase less efficient larger displacement diesel engine 

conventional transmission powertrains instead of hybrid powertrains, 

which are capable of fuel economy improvements of 25 percent over the 

conventional configuration. The economic impact of higher fuel 

consumption will be felt for the 12-year bus life with a larger environmental 

impact. (GILLIG)

59.Comment: The ARB regulations should match those of EPA. While we 

hoped for faster commercialization, lower costs and greater technological 

improvements with increased market penetration of diesel hybrid vehicles, 

the market expansion has been slower than anticipated. Any regulatory 

efforts that discourage further hybrid use will keep the hybrid market in this 

immature state for a longer time, leading to less development of the kind 

of technology integration that would make comprehensive OBD much 

more practical to design and certify. While we appreciate the delay to 

2014, this requirement is still unrealistic in the heavy-duty transit bus 

market. Not extending the compliance deadline like EPA will eliminate 

further expansion of heavy-duty diesel hybrid transit buses in California 

and will force transit properties to buy straight diesel engines, resulting in 

higher greenhouse gas emissions and increased fuel usage. 

VTA understands the frustrations that the subsidies provided in the HVIP 

program have not been met with sufficient efforts in technological 

integration that would allow for straightforward compliance with the OBD 

requirements. However, no heavy-duty transit bus is included in the 

approved HVIP vehicle list, and the hybrid systems used in vehicles on the 

list have been found unsuitable (the Eaton system used on most does not 

fit when the engine is in the rear) for any heavy-duty bus. The heavy-duty 

bus market is much smaller and more unique than medium truck and 

cutaway buses, so even if there is progress in the trucking hybrid market, 

developments there would not be automatically transferred over to the bus 

side. Heavy-duty transit hybrid volumes from Allison and BAE are low 

nationwide, so their leverage with Cummins, the only engine manufacturer 

in the heavy duty transit field, is low. So there is nothing hybrid suppliers 

can do if Cummins does not want to work with them. From a business 

standpoint, cooperating with Cummins may be hard, since the engineering 
57

needed would be as great or more compared to other markets but with 

much lower potential sales in California (a Cummins-Eaton design would 

cover most of the truck market, but Cummins would need to work with 

both BAE and Allison for the heavy-duty transit market). The reason 

hybrid technology is not gaining greater market share in the heavy-duty 

transit is the high costs, and making the case for higher costs not for 

emissions but for getting likely rare warnings of emissions equipment 

issues is difficult. 

While it is possible hybrid system controls could unintentionally subvert 

engine emission systems, this is speculative. Another ARB department is 

investigating this via in-use vehicle testing, but the testing protocol won’t 

be determined until the end of 2013 at the earliest. So it’s premature to 

require fixing a problem that may be non-existent. The environmental 

benefits of hybrids are not in dispute, with lower emissions due to reduced 

fuel consumption and engine shutdown at idle. However, there may still 

be idle allowed in case of constant stop-and-go traffic and for bus comfort 

at layovers up to the 5-minute limit, with the idle time as much as OBD 

compliant diesel trucks, so ARB’s concern that emission control strategies 

that require input from the idle stage in order to calculate overall emissions 

will be affected is unlikely. Further, any deterioration of the battery as 

hybrid systems age (resulting in higher emissions) will be noticed as lower 

fuel mileage by transit providers and would spur them to immediately 

address the issue. BAE and Allison anticipate this and both offer 5-year 

warranties on their battery packs and offer battery rebuild kits expected to 

be needed after 6-7 years of service based on experience at other transit 

properties nationwide. Further, the likely worst case for battery pack 

deterioration are NOx emissions at the same levels of straight diesel 

buses, and PM emissions are currently not affected either way by the 

hybrid system due to modern control strategies focused on exhaust 

aftertreatment, though they are reduced by engine shutdown at idle.

ARB’s proposal to allow some deficiencies in 2014 is a high risk strategy 

for manufacturers, depending on staff’s judgment of the good faith effort, 

and is difficult to achieve. One manufacturer now has some OBD 

designed but is unlikely to have only the few deficiencies allowed, while 

the other manufacturer is further behind with their lower-cost system that 

is the only competition that can drive hybrid prices down, a prerequisite for 

getting the necessary diesel hybrid market growth in heavy-duty transit. 

Asking them to reduce their current engineering efforts in areas such as 

electrification of onboard components (to reduce fuel consumption and 

greenhouse gas emissions) and the engine shutdown at idle feature to 

work on OBD would likely make them withdraw from the California market. 

Even if there is one heavy-duty transit hybrid drive manufacturer that 

meets ARB’s requirements, the California transit properties would be at 

the mercy of the higher cost supplier. Lower prices makes diesel hybrids 

a better choice, while higher prices to recoup OBD development costs 

would make buying diesel hybrids a bad choice for the transit properties. 

ARB staff had already recognized that the path to achieve hybridization of 
58

California’s transit buses involves increased competition, which leads to 

lower prices, which lead to increased sales, which lead to further 

development of the technology, which lead to the ability to have single 

certification of OBD equipment. (VTA)

Agency Response to Comments 58-59:This comment extends beyond the 

scope of the modifications made available in the 15-Day Notice because it 

does not raise any objections or recommendations directed to those 

specified modifications. Nevertheless, ARB provides the following 

response.

ARB supports the efforts to promote hybrid technologies in the heavy-duty 

vehicle sector and believes they are necessary to ARB’s plans to reduce 

greenhouse gases and criteria pollutants. Hybrid technologies, however, 

need to be carefully implemented to ensure low emissions, and OBD 

systems are an integral and critical part of every emission control solution. 

To ensure proper operation of emission controls and the OBD system, 

there needs to be a high level of integration between the engine and 

hybrid systems. Integrating hybrid systems without this attention can have 

detrimental effects on the system, and ARB therefore expressly disagrees 

with the commenter’s statement that it is “speculative” whether hybrid 

system controls could subvert engine emission systems. In fact, recent 

certification data of OBD-equipped engines for hybrid applications 

indicates that certain monitors had to be disabled to prevent the false 

detection of malfunctions while the ability of other monitors to correctly 

detect faults had not been verified. 

ARB disagrees with the statement that its proposal to allow some 

deficiencies in 2014 is a high risk strategy and is difficult to achieve. 

Despite the lack of significant progress in the development of heavy-duty 

hybrid OBD systems by manufacturers of heavy-duty vehicle powertrains, 

ARB seeks to keep hybrids in the marketplace while maintaining a clear 

target for full compliance. This would involve certifying noncompliant OBD 

systems with deficiencies under the OBD regulation, which ARB plans to 

use to encourage continued certification of hybrid powertrains for the 2014 

and subsequent model years. The need for deficiencies was anticipated 

during the development of ARB’s proposal and accordingly the proposal 

includes more latitude in the deficiency provisions for hybrid related issues 

for the 2013 through 2015 model years. ARB has worked and is 

committed to continue working with heavy-duty engine and hybrid system 

manufacturers and other stakeholders to identify hurdles to certification 

with the intent to have industry on the path of rapid progress toward full 

compliance over the next few years, while advocating products to be 

available in the interim so that the industry is able to meet its goals for 

near-term procurement of hybrid buses. Indeed, discussions with these 

manufacturers have indicated that many of the issues applicable to hybrid 

buses may be addressed using the deficiency provisions in the regulation, 

which are not limited in quantity as long as there is an ongoing good faith 

effort in complying with the regulation and continuing improvement to the 
59

overall capability of the system, though there is a limit to the number of 

years the deficiencies can be carried over. Also see agency response to 

comments 37-43.