UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

NATIONAL VEHICLE AND FUEL EMISSIONS LABORATORY

2565 PLYMOUTH ROAD

ANN ARBOR, MICHIGAN 48105-2498

 

MEMORANDUM

SUBJECT: Heavy-Duty Hybrid Onboard Diagnostics

FROM: Amy Kopin

TO: The Docket

DATE: July 21, 2011

On June 17th, 2011 the Hybrid Manufacturers Regulatory Collaboration (HMRC) in 

response to concerns raised by members of the HMRC regarding heavy-duty onboard diagnostic 

(OBD) requirements and timing, sent us suggested OBD regulatory revisions. These regulatory 

revisions reflect the concerns raised during the comment period for the heavy-duty greenhouse 

gas notice of proposed rulemaking that heavy-duty hybrid applications may not be able to meet 

the 2013 heavy-duty OBD regulations that were published in the 2009 OBD Final Rulemaking.1,2

Specifically, they have requested a delay of the application of HD OBD requirements for hybrid 

applications until 2020. The marked-up regulations included in this memo reflect their goal of a 

delay of OBD requirements for Heavy-Duty Hybrid applications until at least 2020. The HMRC 

documents were received via email from Jim Lyons, a consultant for Sierra Research, Inc.

representing the HMRC, and are attached below along with a copy of the original email.

 

1 U.S. EPA, NHTSA, and DOT, “Greenhouse Gas Emission Standards and Fuel Efficiency Standards for Mediumand Heavy-Duty Engines and Vehicles,” republished December 29, 2010. Available here: 

http://origin.www.gpo.gov/fdsys/pkg/FR-2010-12-29/html/2010-32726.htm

2 U.S. EPA, “Control of Air Pollution from New Motor Vehicles and New Motor Vehicles Engines; Final Rule 

Regulations Requiring Onboard Diagnostic Systems on 2010 and Later Heavy-Duty Engines Used in Highway 

Applications Over 14,000 Pounds; Revisions to Onboard Diagnostic Requirements for Diesel Highway Heavy-Duty 

Vehicles Under 14,000 Pounds,” published February 24, 2009. Available here: 

http://www.epa.gov/otaq/regs/im/obd/regtech/hd-obd-frm-02-24-09-notice-74-fr-8310.pdf

OFFICE OF

AIR AND RADIATION
HMRC

Jim Lyons to: Amy Kopin 06/17/2011 11:22 AM

Cc: iandmckenzie, barbara.chance, kevin.rodgers, derek.matthews, 

thomas.m.apalenek

History: This message has been forwarded.

Amy:

As we discussed on the phone yesterday, please find attached additional materials from HMRC related

to the hybrid OBD issue.  

As you know, HMRC supports the development of HD OBD for vehicles with hybrid powertrain systems,

but feels strongly, that among other things, that the timing of the implementation of HD OBD systems

on hybrids needs to provide adequate lead time to accomplish all of the steps required to reach

implementation.  To that end, HMRC has created a Gantt chart to lay out the steps and milestones we

believe are needed to implement HD OBD in the market for hybrid commercial vehicles.  It is far from

exhaustive and could be much more detailed, but we feel it captures the main items and events that

need to take place.  The chart also supports HMRC’s position with regard to 2020 model‐year

implementation of fuel HD OBD on hybrids and the appropriateness of generally aligning hybrids with

alternative fuel engines in terms of providing lead time in advance of HD OBD compliance dates.  We’d

like to review this with EPA and discuss both the steps and the timing we’ve attributed to the steps, to

ideally gain a common understanding and consensus on the level of effort and timing, as well as the

parties involved in making HD OBD successful for the hybrid commercial market.   

In addition, please find attached, our thoughts regarding regulatory changes needed to address the

issues that have been raised regarding implementation of HD OBD with hybrid powertrain systems in

light of the timing indicated by the Gantt chart and alignment with alternative fuel engine requirements.

We appreciate your time and consideration of this information and look forward to reviewing it with

you.

James M. Lyons

Sierra Research, Inc.

1801 J Street

Sacramento, CA 95811

Phone 916-444-6666 or 916-273-5138

jlyons@sierraresearch.com
ID Task Name 

1 Definition of Certification requirements and process for hybrids 2 Define components impacted for information sharing of tasks 3 Establish working contractual relationship and ‘rules of engagement’ with engine manufacturer(s) with regards to HD OBD 4 Development of internal specifications for S/W and H/W to begin design process 5 Evaluation of current diagnostic S/W to determine ‘gaps’ to achieve HD OBD compliance 6 Evaluation of current hardware to support HD OBD diagnostic requirements 7 Creation/qualification of data handling algorithm(s) 8 Definition and agreement on the ‘monitors’ as described by CARB specific to the hybrid system (HMRC / CARB / Individuals) 9 Creation of hybrid performance monitoring algorithms 

10 Qualification of monitoring algorithms 11 Theoretical evaluation of potential impacts of current hybrid system(s) on a HD OBD 2013 compliant engine(s) or diagnostic strategy(ies) 12 Physical testing of engine(s), coupled to hybrid system(s) to validate theoretical evaluation 13 Individual manufacturers evaluation of sub-contract requirements for support of OBD development 14 Engine / OEM and Hybrid manufacturers individual development of suggested messages for hybrid/vehicle/engine communication for J1939-73 and ISO 15 Review, evaluation, discussion and ultimately agreement on incorporation of messages to the SAE Standard 16 Implementation by individual companies of the standard messages 17 Theoretical evaluation of potential impacts of HD OBD specific hybrid system(s) on a HD OBD 2013 compliant engine(s) or diagnostic strategy(ies) 18 Physical testing of engine(s), coupled to hybrid system(s) to validate theoretical evaluation 19 Iteration of S/W, possibly H/W based on results of testing 20 Re-qualification of S/W and H/W 21 Release for final integration testing 22 With release of HD OBD hybrid systems, evidence gathering, fleet trials 23 Reports to Gov’t agencies of findings and any possible issues 24 Loop back of process to address and ‘fix’ any identified issues 

TaskSplitProgress

MilestoneSummaryProject Summary

External TasksExternal MilestoneDeadline

Page 1

Project: 2020 timelineDate: Thu 6/16/11
Start Finish

Thu 6/30/11 Wed 5/1/13Thu 6/16/11 Wed 7/13/11Thu 6/30/11 Wed 5/30/12Thu 5/31/12 Wed 11/14/12

Thu 11/15/12 Wed 3/6/13

Thu 3/7/13 Wed 5/29/13

Thu 11/15/12 Wed 5/1/13

Thu 5/2/13 Wed 4/2/14Thu 5/2/13 Wed 6/26/13Thu 4/3/14 Wed 5/28/14

Thu 11/15/12 Wed 5/1/13

Thu 5/29/14 Wed 2/4/15

Thu 11/15/12 Wed 5/1/13

Thu 5/2/13 Wed 3/4/15Thu 3/5/15 Wed 1/4/17Thu 1/5/17 Wed 12/6/17

Thu 12/7/17 Wed 1/31/18

Thu 2/1/18 Wed 7/18/18

Thu 7/19/18 Wed 3/27/19Thu 3/28/19 Wed 6/19/19

Wed 6/19/19 Wed 6/19/19

Thu 6/20/19 Wed 12/4/19Thu 12/5/19 Wed 5/20/20Thu 12/5/19 Wed 5/20/20

Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q

1 2012 2013 2014 2015 2016 2017 2018 

TaskSplitProgress

MilestoneSummaryProject Summary

External TasksExternal MilestoneDeadline

Page 2

Project: 2020 timelineDate: Thu 6/16/11
Details of Hybrid HDOBD Timeline Line Items

Item #

1 Definition of Certification requirements and process for hybrids

 EPA

 CARB (May adopt EPA approach, may delay and consider own wording, and then begin the definition process)

 UDS / WWH (World Wide Harmonized)

 Definition and Development of high level Hybrid HDOBD architecture (eg., distributed vs. centralized)

 Definition of certificate holder (eg., engine tailpipe emissions, engine HDOBD, GHG, hybrid HDOBD, etc.)

 Definition of certificate procedure - Analytical, Engine based, On-dyno, In-Vehicle, 

 Proof by: Analysis, Engine based, On-dyno, In-Vehicle?

 If not analytical based, need a defined test duty cycle.

 Defined test conditions (temperature, humidity, start/end SOC)?

 Engine only test or with Hybrid? Actual hardware or generic hybrid simulator?

 What vehicle/load configuration? (hybrid systems can respond very differently to different GVW)

 Can an engine OBD "strategy" be certified compliant with a hybrid? Shown true on 1 engine, 

valid for entire family or products that use the same "strategy"?

2 Define components impacted for information sharing of tasks, 

 There may be one or more hybrid component supplier who need to share with each other, share with engine supplier, etc.

 The potential list of components can include Engine / Transmission / ABS Controller / Body Controller / 

Push Button Shift Selector / Energy Storage System (battery) / Hybrid System Controller (Inverter) / Motor-Generator / Oil 

Pressure Sensor / Clutch Position Sensor / Low Voltage Electrical system (12V power) / Retarder controller (optional) 

3 Establish working contractual relationship and ‘rules of engagement’ with engine manufacturer(s) with regards to HD OBD

 What engine OEMs will share with regards to diagnostic algorithms

 What hybrid manufacturers will share with regards to diagnostic algorithms

 Terms and Conditions around intellectual property on developed solutions

4 Development of internal specifications for S/W and H/W to begin design process

5 Evaluation of current diagnostic S/W to determine ‘gaps’ to achieve HD OBD compliance

6 Evaluation of current hardware to support HD OBD diagnostic requirements

7 Creation/qualification of data handling algorithm(s)

8 Definition and agreement on the ‘monitors’ as described by CARB specific to the hybrid system (HMRC / CARB / Individuals)

9 Creation of monitoring algorithms

10 Qualification of monitoring algorithms

11 Theoretical evaluation of potential impacts of current hybrid system(s) on a HD OBD 2013 compliant engine(s) or diagnostic strategy(ies)

12 Physical testing of engine(s), coupled to hybrid system(s) to validate theoretical evaluation

 Dyno level initially

 In vehicle testing ultimately

 Many possible combinations depending on hybrid architecture, concept of operation and engine OBD configurations

13 Individual manufacturers evaluation of sub-contract requirements for support of OBD development
 If components like Batteries, DC/DCs, Inverters, Motors are outsourced by a manufacturer, they may need to 

negotiate changes to existing contracts to increase scope to support HD OBD requirements levied upon the sub-suppliers

 In many cases these requirements may not be something the sub-supplier is familiar with or properly 

resourced to support, or even quote.

 As the requirements and specifics of HD OBD for hybrids is vague and still to be determined in detail, will 

make estimation difficult and costs (conservative quotes)

14 Engine / OEM and Hybrid manufacturers individual development of suggested messages for hybrid / vehicle / engine 

communication for J1939 and ISO 15765/15031

Group review and agreement on suggested messages

 May happen directly at the SAE J1939 level

 May initially take place at a ‘stake holders’ level (HMRC for hybrid, EMA for engines) then take message list to SAE committee

15 Review, evaluation, discussion and ultimately agreement on incorporation of messages to the SAE Standard

16 Implementation by individual companies of the standard messages

17 Theoretical evaluation of potential impacts of HD OBD specific hybrid system(s) on a HD OBD 2013 compliant engine(s) or diagnostic strategy(ies)

18 Physical testing of engine(s), coupled to hybrid system(s) to validate theoretical evaluation

 Dyno level initially

 In vehicle testing ultimately

 Many possible combinations depending on hybrid architecture, concept of operation and engine OBD configurations

19 Iteration of S/W, possibly H/W based on results of testing

20 Re-qualification of S/W and H/W

21 With release of HD OBD hybrid systems, evidence gathering, fleet trials

22 Reports to Gov’t agencies of findings and any possible deficiencies

23 Loop back of process to address and ‘fix’ any identified deficiencies
Regulatory text edited and submitted by the Hybrid Manufacturers Regulatory Council.

Page 1 of 2

§ 86.010-2 Definitions.

 The definitions of § 86.004-2 continue to apply to 2004 and later model year vehicles. 

The definitions listed in this section apply beginning with the 2010 model year.

 

 DTC means diagnostic trouble code.

 

 Engine or engine system as used in §§ 86.007-17, 86.007-30, 86.010-18, and 86.010-

38 means the engine, fuel system, induction system, aftertreatment system, and 

everything that makes up the system for which an engine manufacturer has received a 

certificate of conformity.

 

 Engine start as used in § 86.010-18 means the point when the engine reaches a speed 

150 rpm below the normal, warmed-up idle speed (as determined in the drive position for 

vehicles equipped with an automatic transmission). For hybrid vehicles or for engines 

employing alternative engine start hardware or strategies (e.g., integrated starter and 

generators.), the manufacturer may use an alternative definition for engine start (e.g., 

key-on) provided the alternative definition is based on equivalence to an engine start for a 

conventional vehicle.

 

 Functional check, in the context of onboard diagnostics, means verifying that a 

component and/or system that receives information from a control computer responds 

properly to a command from the control computer.

The additions below serve to include hybrid powertrain systems as part of 

the HD OBD regulations. The “manufacturer” definition is intended to 

differentiate companies that design and build (e.g. manufacturer) a 

“hybrid powertrain system” from companies that manufacture

components that are used in hybrid powertrain systems.

 Hybrid powertrain system means a component or a set of components other than an 

internal combustion engine that: 1) provides motive power to the vehicle, 2) also provides 

a regenerative braking function, and 3) includes a hybrid energy storage system other 

than a conventional battery system or conventional flywheel. Supplemental electrical 

batteries and hydraulic accumulators are examples of hybrid energy storage systems.

 

 Hybrid powertrain system manufacturer means an entity that undertakes the physical 

and engineering process of designing, constructing, and assembling hybrid powertrain 

systems.

 Ignition cycle as used in § 86.010-18 means a cycle that begins with engine start, 

meets the engine start definition for at least two seconds plus or minus one second, and 

ends with engine shutoff.

 

 Limp-home operation as used in § 86.010-18 means an operating mode that an engine 

is designed to enter upon determining that normal operation cannot be maintained. In 
Regulatory text edited and submitted by the Hybrid Manufacturers Regulatory Council.

Page 2 of 2

general, limp-home operation implies that a component or system is not operating 

properly or is believed to be not operating properly.

 

 Malfunction means the conditions have been met that require the activation of an 

OBD malfunction indicator light and storage of a DTC.

 

 MIL-on DTC means the diagnostic trouble code stored when an OBD system has 

detected and confirmed that a malfunction exists (e.g., typically on the second drive cycle 

during which a given OBD monitor has evaluated a system or component). Industry 

standards may refer to this as a confirmed or an active DTC.

 

 Onboard Diagnostics (OBD) group means a combination of engines, engine families, 

or engine ratings that use the same OBD strategies and similar calibrations.

 

 Pending DTC means the diagnostic trouble code stored upon the detection of a 

potential malfunction.

 

 Permanent DTC means a DTC that corresponds to a MIL-on DTC and is stored in 

non-volatile random access memory (NVRAM). A permanent DTC can only be erased 

by the OBD system itself and cannot be erased through human interaction with the OBD 

system or any onboard computer.

 

 Potential malfunction means that conditions have been detected that meet the OBD 

malfunction criteria but for which more drive cycles are allowed to provide further 

evaluation prior to confirming that a malfunction exists.

 

 Previous-MIL-on DTC means a DTC that corresponds to a MIL-on DTC but is 

distinguished by representing a malfunction that the OBD system has determined no 

longer exists but for which insufficient operation has occurred to satisfy the DTC erasure 

provisions.

 

 Rationality check, in the context of onboard diagnostics, means verifying that a 

component that provides input to a control computer provides an accurate input to the 

control computer while in the range of normal operation and when compared to all other 

available information.

 

 Similar conditions, in the context of onboard diagnostics, means engine conditions 

having an engine speed within 375 rpm, load conditions within 20 percent, and the same 

warm up status (i.e., cold or hot). The manufacturer may use other definitions of similar

conditions based on comparable timeliness and reliability in detecting similar engine 

operation.

[74 FR 8369, Feb. 24, 2009] 
Regulatory text edited and submitted by the Hybrid Manufacturers Regulatory Council.

Page 1 of 101

§ 86.010-18

On-board Diagnostics for engines used in applications greater than 14,000 pounds 

GVWR.

(a) General. According to the implementation schedule shown in paragraph (o) of this 

section, heavy-duty engines intended for use in a heavy-duty vehicle weighing more 

than 14,000 pounds GVWR must be equipped with an on-board diagnostic (OBD) 

system capable of monitoring all emission-related engine systems or components 

during the life of the engine. The OBD system is required to detect all malfunctions 

specified in paragraphs (g), (h), and (i) of this § 86.010-18 although the OBD system is 

not required to use a unique monitor to detect each of those malfunctions.

(1) When the OBD system detects a malfunction, it must store a pending, a MIL-on, 

or a previous-MIL-on diagnostic trouble code (DTC) in the onboard computer’s 

memory. A malfunction indicator light (MIL) must also be activated as specified in 

paragraph (b) of this section.

(2) Data link connector.

(i) For model years 2010 through 2012, the OBD system must be equipped with a 

data link connector to provide access to the stored DTCs as specified in paragraph 

(k)(2) of this section.

(ii) For model years 2013 and later, the OBD system must be equipped with a 

standardized data link connector to provide access to the stored DTCs as specified 

in paragraph (k)(2) of this section.

(3) The OBD system cannot be programmed or otherwise designed to deactivate 

based on age and/or mileage. This requirement does not alter existing law and 

enforcement practice regarding a manufacturer’s liability for an engine beyond its 

regulatory useful life, except where an engine has been programmed or otherwise 

designed so that an OBD system deactivates based on age and/or mileage of the 

engine.

(4) Drive cycle or driving cycle, in the context of this § 86.010-18, means operation 

that meets any of the conditions of paragraphs (a)(4)(i) through (a)(4)(iv) of this 

section. Further, for OBD monitors that run during engine-off conditions, the period 

of engine-off time following engine shutoff and up to the next engine start may be 

considered part of the drive cycle for the conditions of paragraphs (a)(4)(i) and 

(a)(4)(iv) of this section. For engines/vehicles that employ engine shutoff OBD 

monitoring strategies that do not require the vehicle operator to restart the engine to 

continue vehicle operation (e.g., a hybrid bus with engine shutoff at idle), the 

manufacturer may use an alternative definition for drive cycle (e.g., key-on followed 

by key-off). Any alternative definition must be based on equivalence to engine startup 

and engine shutoff signaling the beginning and ending of a single driving event for a 

conventional vehicle. For engines that are not likely to be routinely operated for long 
Regulatory text edited and submitted by the Hybrid Manufacturers Regulatory Council.

Page 2 of 101

continuous periods of time, a manufacturer may also request approval to use an 

alternative definition for drive cycle (e.g., solely based on engine start and engine 

shutoff without regard to four hours of continuous engine-on time). Administrator 

approval of the alternative definition will be based on manufacturer-submitted data 

and/or information demonstrating the typical usage, operating habits, and/or driving 

patterns of these vehicles.

(i) Begins with engine start and ends with engine shutoff;

(ii) Begins with engine start and ends after four hours of continuous engine-on 

operation;

(iii) Begins at the end of the previous four hours of continuous engine-on operation 

and ends after four hours of continuous engine-on operation; or

(iv) Begins at the end of the previous four hours of continuous engine-on operation 

and ends with engine shutoff.

(5) As an alternative to demonstrating compliance with the provisions of paragraphs 

(b) through (l) of this § 86.010-18, a manufacturer may demonstrate how the OBD 

system they have designed to comply with California OBD requirements for engines 

used in applications greater than 14,000 pounds also complies with the intent of the 

provisions of paragraphs (b) through (l) of this section. To make use of this 

alternative, the manufacturer must demonstrate to the Administrator how the OBD 

system they intend to certify meets the intent behind all of the requirements of this 

section, where applicable (e.g., paragraph (h) of this section would not apply for a 

diesel fueled/CI engine). Furthermore, if making use of this alternative, the 

manufacturer must comply with the specific certification documentation requirements 

of paragraph (m)(3) of this section.

(6) Temporary provisions to address hardship due to unusual circumstances.

(i) After considering the unusual circumstances, the Administrator may permit the 

manufacturer to introduce into U.S. commerce engines that do not comply with this 

§ 86.010-18 for a limited time if all the following conditions apply:

(A) Unusual circumstances that are clearly outside the manufacturer’s control 

prevent compliance with the requirements of this § 86.010-18.

(B) The manufacturer exercised prudent planning and was not able to avoid the 

violation and has taken all reasonable steps to minimize the extent of the 

nonconformity.

(C) No other allowances are available under the regulations in this chapter to 

avoid the impending violation.
Regulatory text edited and submitted by the Hybrid Manufacturers Regulatory Council.

Page 3 of 101

(ii) To apply for an exemption, the manufacturer must send to the Administrator a 

written request as soon as possible before being in violation. In the request, the 

manufacturer must show that all the conditions and requirements of paragraph 

(a)(6)(i) of this section are met.

(iii) The request must also include a plan showing how all the applicable 

requirements will be met as quickly as possible.

(iv) The manufacturer shall give the Administrator other relevant information upon 

request.

(v) The Administrator may include additional conditions on an approval granted 

under the provisions of this paragraph (a)(6), including provisions that may require 

field repair at the manufacturer’s expense to correct the noncompliance.

(vi) Engines sold as non-compliant under this temporary hardship provision must 

display “non-OBD” in the data stream as required under paragraph (k)(4)(ii) of this 

section. Upon correcting the noncompliance, the data stream value must be updated 

accordingly.

(b) Malfunction indicator light (MIL) and Diagnostic Trouble Codes (DTC). The OBD 

system must incorporate a malfunction indicator light (MIL) or equivalent and must 

store specific types of diagnostic trouble codes (DTC). Unless otherwise specified, all 

provisions of this paragraph (b) apply for 2010 and later model years.

(1) MIL specifications.

(i) For model years 2013 and later, the MIL must be located on the primary driver’s 

side instrument panel and be of sufficient illumination and location to be readily 

visible under all lighting conditions. The MIL must be amber (yellow) in color; the 

use of red for the OBD-related MIL is prohibited. More than one general purpose 

malfunction indicator light for emission-related problems shall not be used; separate 

specific purpose warning lights (e.g., brake system, fasten seat belt, oil pressure, 

etc.) are permitted. When activated, the MIL shall display the International 

Standards Organization (ISO) engine symbol.

(ii) The OBD system must activate the MIL when the ignition is in the keyon/engine-off position before engine cranking to indicate that the MIL is functional. 

The MIL shall be activated continuously during this functional check for a 

minimum of 5 seconds. During this MIL key-on functional check, the data stream 

value (see paragraph (k)(4)(ii) of this section) for MIL status must indicate 

“commanded off” unless the OBD system has detected a malfunction and has stored 

a MIL-on DTC. This MIL key-on functional check is not required during vehicle 

operation in the key-on/engine-off position subsequent to the initial engine cranking 

of an ignition cycle (e.g., due to an engine stall or other non-commanded engine 

shutoff).
Regulatory text edited and submitted by the Hybrid Manufacturers Regulatory Council.

Page 4 of 101

(iii) As an option, the MIL may be used to indicate readiness status (see paragraph 

(k)(4)(i) of this section) in a standardized format in the key-on/engine-off position.

(iv) A manufacturer may also use the MIL to indicate which, if any, DTCs are 

currently stored (e.g., to “blink” the stored DTCs). Such use must not activate 

unintentionally during routine driver operation.

(v) For model years 2013 and later, the MIL required by this paragraph (b) must not 

be used in any other way than is specified in this section.

(2) MIL activation and DTC storage protocol.

(i) Within 10 seconds of detecting a potential malfunction, the OBD system must 

store a pending DTC that identifies the potential malfunction.

(ii) If the potential malfunction is again detected before the end of the next drive 

cycle during which monitoring occurs (i.e., the potential malfunction has been 

confirmed as a malfunction), then within 10 seconds of such detection the OBD 

system must activate the MIL continuously and store a MIL-on DTC (systems using 

the SAE J1939 standard protocol specified in paragraph (k)(1) of this section may 

either erase or retain the pending DTC in conjunction with storing the MIL-on 

DTC). If the potential malfunction is not detected before the end of the next drive 

cycle during which monitoring occurs (i.e., there is no indication of the malfunction 

at any time during the drive cycle), the corresponding pending DTC should be 

erased at the end of the drive cycle. Similarly, if a malfunction is detected for the 

first time and confirmed on a given drive cycle without need for further evaluation, 

then within 10 seconds of such detection the OBD system must activate the MIL 

continuously and store a MIL-on DTC (again, systems using the SAE J1939 

standard protocol specified in paragraph (k)(1) of this section may optionally store a 

pending DTC in conjunction with storing the MIL-on DTC).

(iii) A manufacturer may request Administrator approval to employ alternative 

statistical MIL activation and DTC storage protocols to those specified in 

paragraphs (b)(2)(i) and (b)(2)(ii) of this section. Approval will depend upon the 

manufacturer providing data and/or engineering evaluations that demonstrate that 

the alternative protocols can evaluate system performance and detect malfunctions 

in a manner that is equally effective and timely. Strategies requiring on average 

more than six drive cycles for MIL activation will not be accepted.

 

(iv) The OBD system must store a “freeze frame” of the operating conditions (as 

defined in paragraph (k)(4)(iii) of this section) present upon detecting a malfunction 

or a potential malfunction. In the event that a pending DTC has matured to a MILon DTC, the manufacturer shall either retain the currently stored freeze frame 

conditions or replace the stored freeze frame with freeze frame conditions regarding 

the MIL-on DTC. Any freeze frame stored in conjunction with any pending DTC or 

MIL-on DTC should be erased upon erasure of the corresponding DTC.
Regulatory text edited and submitted by the Hybrid Manufacturers Regulatory Council.

Page 5 of 101

(v) If the engine enters a limp-home mode of operation that can affect emissions or 

the performance of the OBD system, or in the event of a malfunction of an onboard 

computer(s) itself that can affect the performance of the OBD system, the OBD 

system must activate the MIL and store a MIL-on DTC within 10 seconds to inform 

the vehicle operator. If the limp-home mode of operation is recoverable (i.e., 

operation automatically returns to normal at the beginning of the following ignition 

cycle), the OBD system may wait to activate the MIL and store the MIL-on DTC if 

the limp-home mode of operation is again entered before the end of the next 

ignition cycle rather than activating the MIL within 10 seconds on the first drive 

cycle during which the limp-home mode of operation is entered.

(vi) Before the end of an ignition cycle, the OBD system must store a permanent 

DTC(s) that corresponds to any stored MIL-on DTC(s).

(3) MIL deactivation and DTC erasure protocol

(i) Deactivating the MIL. Except as otherwise provided for in paragraphs 

(g)(2)(iv)(E) and (g)(6)(iv)(B) of this section for diesel misfire malfunctions and 

empty reductant tanks, and paragraphs (h)(1)(iv)(F), (h)(2)(viii), and (h)(7)(iv)(B) 

of this section for gasoline fuel system, misfire, and evaporative system 

malfunctions, once the MIL has been activated, it may be deactivated after three 

subsequent sequential drive cycles during which the monitoring system responsible 

for activating the MIL functions and the previously detected malfunction is no 

longer present and provided no other malfunction has been detected that would 

independently activate the MIL according to the requirements outlined in paragraph 

(b)(2) of this section.

(ii) Erasing a MIL-on DTC. The OBD system may erase a MIL-on DTC if the 

identified malfunction has not again been detected in at least 40 engine warm up 

cycles and the MIL is presently not activated for that malfunction. The OBD system 

may also erase a MIL-on DTC upon deactivating the MIL according to paragraph 

(b)(3)(i) of this section provided a previous-MIL-on DTC is stored upon erasure of 

the MIL-on DTC. The OBD system may erase a previous-MIL-on DTC if the 

identified malfunction has not again been detected in at least 40 engine warm up 

cycles and the MIL is presently not activated for that malfunction.

(iii) Erasing a permanent DTC. The OBD system can erase a permanent DTC only 

if:

(A) The OBD system itself determines that the malfunction that caused the 

corresponding permanent DTC to be stored is no longer present and is not 

commanding activation of the MIL, concurrent with the requirements of 

paragraph (b)(3)(i) of this section which, for purposes of this paragraph (b)(3)(iii), 

shall apply to all monitors.

(B) All externally erasable DTC information stored in the onboard computer has 

been erased (i.e., through the use of a scan tool or battery disconnect) and the 
Regulatory text edited and submitted by the Hybrid Manufacturers Regulatory Council.

Page 6 of 101

monitor of the malfunction that caused the permanent DTC to be stored is subject 

to the minimum ratio requirements of paragraph (d) of this section, the OBD 

system shall erase the permanent DTC at the end of a drive cycle if the monitor 

has run and made one or more determinations during a drive cycle that the 

malfunction of the component or the system is not present and has not made any 

determinations within the same drive cycle that the malfunction is present.

(C)

1. All externally erasable DTC information stored in the onboard computer 

has been erased (i.e., through the use of a scan tool or battery disconnect) and 

the monitor of the malfunction that caused the permanent DTC to be stored is 

not subject to the minimum ratio requirements of paragraph (d) of this section, 

the OBD system shall erase the permanent DTC at the end of a drive cycle 

provided the following two criteria have independently been satisfied:

i. The monitor has run and made one or more determinations during a 

drive cycle that the malfunction is no longer present and has not made any 

determinations within the same drive cycle that the malfunction is present; 

and,

ii. The monitor does not detect a malfunction on a drive cycle and the 

criteria of paragraph (d)(4)(ii) of this section has been met.

2. These two separate criteria may be met on the same or different drive 

cycles provided the monitor never detects a malfunction during either drive 

cycle, and if criteria (b)(3)(iii)(C)(1)(i) happens first then no malfunction may 

be detected before criteria (b)(3)(iii)(C)(1)(ii) occurs. If a malfunction occurs 

after criteria (b)(3)(iii)(C)(1)(i) then criteria (b)(3)(iii)(C)(1)(i) must be 

satisfied again. For the second criterion, the manufacturer must exclude any 

temperature and/or elevation provisions of paragraph (d)(4)(ii) of this section. 

For this paragraph (b)(3)(iii)(C), monitors required to use “similar conditions”

as defined in § 86.010-2 to store and erase pending and MIL-on DTCs cannot 

require that the similar conditions be met prior to erasure of the permanent 

DTC.

(D) The Administrator shall allow monitors subject to paragraph (b)(3)(iii)(B) of 

this section to use the criteria of paragraph (b)(3)(iii)(C) of this section in lieu of 

paragraph (b)(3)(iii)(B). Further, manufacturers may request Administrator 

approval to use alternative criteria to erase the permanent DTC. The 

Administrator shall approve alternate criteria that will not likely require driving 

conditions that are longer and more difficult to meet than those required under 

paragraph (b)(3)(iii)(C) of this section and do not require access to enhanced scan 

tools to determine conditions necessary to erase the permanent DTC.

(4) Exceptions to MIL and DTC requirements.
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(i) If a limp-home mode of operation causes a overt indication (e.g., activation of a 

red engine shut-down warning light) such that the driver is certain to respond and 

have the problem corrected, a manufacturer may choose not to activate the MIL as 

required by paragraph (b)(2)(v) of this section. Additionally, if an auxiliary 

emission control device has been properly activated as approved by the 

Administrator, a manufacturer may choose not to activate the MIL.

(ii) For gasoline engines, a manufacturer may choose to meet the MIL and DTC 

requirements in § 86.007-17 in lieu of meeting the requirements of paragraph (b) of 

this § 86.010-18.

(c) Monitoring conditions. The OBD system must monitor and detect the malfunctions 

specified in paragraphs (g), (h), and (i) of this section under the following general 

monitoring conditions. The more specific monitoring conditions of paragraph (d) of this 

section are sometimes required according to the provisions of paragraphs (g), (h), and 

(i) of this section.

(1) As specifically provided for in paragraphs (g), (h), and (i) of this section, the 

monitoring conditions for detecting malfunctions must be technically necessary to 

ensure robust detection of malfunctions (e.g., avoid false passes and false indications 

of malfunctions); designed to ensure monitoring will occur under conditions that may 

reasonably be expected to be encountered in normal vehicle operation and normal 

vehicle use; and, designed to ensure monitoring will occur during the FTP transient 

test cycle contained in appendix I paragraph (f), of this part, or similar drive cycle as 

approved by the Administrator.

(2) Monitoring must occur at least once per drive cycle in which the monitoring 

conditions are met.

(3) Manufacturers may define monitoring conditions that are not encountered during 

the FTP cycle as required in paragraph (c)(1) of this section. In doing so, the 

manufacturer would be expected to consider the degree to which the requirement to 

run during the FTP transient cycle restricts monitoring during in-use operation, the 

technical necessity for defining monitoring conditions that are not encountered during 

the FTP cycle, whether monitoring is otherwise not feasible during the FTP cycle, 

and/or the ability to demonstrate that the monitoring conditions satisfy the minimum 

acceptable in-use monitor performance ratio requirement as defined in paragraph (d) 

of this section.

(d) In-use performance tracking. As specifically required in paragraphs (g), (h), and (i) 

of this section, the OBD system must monitor and detect the malfunctions specified in 

paragraphs (g), (h), and (i) of this section according to the criteria of this paragraph (d). 

The OBD system is not required to track and report in-use performance for monitors 

other than those specifically identified in paragraph (d)(1) of this section, but all 

monitors on applicable model year engines are still required to meet the in-use 

performance ratio as specified in paragraph (d)(1)(ii) of this section.
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(1) The manufacturer must implement software algorithms in the OBD system to 

individually track and report the in-use performance of the following monitors, if 

equipped, in the standardized format specified in paragraph (e) of this section: 

NMHC converting catalyst (paragraph (g)(5) of this section); NOx converting catalyst 

(paragraph (g)(6) of this section); gasoline catalyst (paragraph (h)(6) of this section); 

exhaust gas sensor (paragraph (g)(9) of this section) or paragraph (h)(8) of this 

section); evaporative system (paragraph (h)(7) of this section); EGR system 

(paragraph (g)(3) of this section or (h)(3) of this section); VVT system (paragraph 

(g)(10) of this section or (h)(9) of this section); secondary air system (paragraph 

(h)(5) of this section); DPF system (paragraph (g)(8) of this section); boost pressure 

control system (paragraph (g)(4) of this section); and, NOx adsorber system 

(paragraph (g)(7) of this section).

(i) The manufacturer shall not use the calculated ratio specified in paragraph (d)(2) 

of this section or any other indication of monitor frequency as a monitoring 

condition for a monitor (e.g., using a low ratio to enable more frequent monitoring 

through diagnostic executive priority or modification of other monitoring 

conditions, or using a high ratio to enable less frequent monitoring).

(ii) For model years 2013 and later, manufacturers must define monitoring 

conditions that, in addition to meeting the criteria in paragraphs (c)(1) and (d)(1) of 

this section, ensure that the monitor yields an in-use performance ratio (as defined 

in paragraph (d)(2) of this section) that meets or exceeds the minimum acceptable 

in-use monitor performance ratio of 0.100 for all monitors specifically required in 

paragraphs (g), (h), and (i) of this section to meet the monitoring condition 

requirements of this paragraph (d).

(iii) If the most reliable monitoring method developed requires a lower ratio for a 

specific monitor than that specified in paragraph (d)(1)(ii) of this section, the 

Administrator may lower the minimum acceptable in-use monitoring performance 

ratio.

(2) In-use performance ratio definition. For monitors required to meet the 

requirements of paragraph (d) of this section, the performance ratio must be 

calculated in accordance with the specifications of this paragraph (d)(2).

(i) The numerator of the performance ratio is defined as the number of times a 

vehicle has been operated such that all monitoring conditions have been 

encountered that are necessary for the specific monitor to detect a malfunction.

(ii) The denominator is defined as the number of times a vehicle has been operated 

in accordance with the provisions of paragraph (d)(4) of this section.

(iii) The performance ratio is defined as the numerator divided by the denominator.

(3) Specifications for incrementing the numerator.
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(i) Except as provided for in paragraph (d)(3)(v) of this section, the numerator, 

when incremented, must be incremented by an integer of one. The numerator shall 

not be incremented more than once per drive cycle.

(ii) The numerator for a specific monitor must be incremented within 10 seconds if 

and only if the following criteria are satisfied on a single drive cycle:

(A) Every monitoring condition has been satisfied that is necessary for the 

specific monitor to detect a malfunction and store a pending DTC, including 

applicable enable criteria, presence or absence of related DTCs, sufficient length 

of monitoring time, and diagnostic executive priority assignments (e.g., diagnostic 

“A” must execute prior to diagnostic “B”). For the purpose of incrementing the 

numerator, satisfying all the monitoring conditions necessary for a monitor to 

determine that the monitor is not malfunctioning shall not, by itself, be sufficient 

to meet this criteria.

(B) For monitors that require multiple stages or events in a single drive cycle to 

detect a malfunction, every monitoring condition necessary for all events to 

complete must be satisfied.

(C) For monitors that require intrusive operation of components to detect a 

malfunction, a manufacturer must request approval of the strategy used to 

determine that, had a malfunction been present, the monitor would have detected 

the malfunction. Administrator approval of the request will be based on the 

equivalence of the strategy to actual intrusive operation and the ability of the 

strategy to determine accurately if every monitoring condition was satisfied that 

was necessary for the intrusive event to occur.

(D) For the secondary air system monitor, the criteria in paragraphs (d)(3)(ii)(A) 

through (d)(3)(ii)(C) of this section are satisfied during normal operation of the 

secondary air system. Monitoring during intrusive operation of the secondary air 

system later in the same drive cycle for the sole purpose of monitoring shall not, 

by itself, be sufficient to meet these criteria.

(iii) For monitors that can generate results in a “gray zone” or “non-detection zone”

(i.e., monitor results that indicate neither a properly operating system nor a 

malfunctioning system) or in a “non-decision zone” (e.g., monitors that increment 

and decrement counters until a pass or fail threshold is reached), the numerator, in 

general, shall not be incremented when the monitor indicates a result in the “nondetection zone” or prior to the monitor reaching a complete decision. When 

necessary, the Administrator will consider data and/or engineering analyses 

submitted by the manufacturer demonstrating the expected frequency of results in 

the “non-detection zone” and the ability of the monitor to determine accurately, had 

an actual malfunction been present, whether or not the monitor would have detected 

a malfunction instead of a result in the “non-detection zone.”
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(iv) For monitors that run or complete their evaluation with the engine off, the 

numerator must be incremented either within 10 seconds of the monitor completing 

its evaluation in the engine off state, or during the first 10 seconds of engine start on 

the subsequent drive cycle.

(v) Manufacturers that use alternative statistical MIL activation protocols as 

allowed in paragraph (b)(2)(iii) of this section for any of the monitors requiring a 

numerator, are required to increment the numerator(s) appropriately. The 

manufacturer may be required to provide supporting data and/or engineering 

analyses demonstrating both the equivalence of their incrementing approach to the 

incrementing specified in this paragraph (d)(3) for monitors using the standard MIL 

activation protocol, and the overall equivalence of the incrementing approach in 

determining that the minimum acceptable in-use performance ratio of paragraph 

(d)(1)(ii) of this section, if applicable, has been satisfied.

(4) Specifications for incrementing the denominator.

(i) The denominator, when incremented, must be incremented by an integer of one. 

The denominator shall not be incremented more than once per drive cycle.

(ii) The denominator for each monitor must be incremented within 10 seconds if 

and only if the following criteria are satisfied on a single drive cycle:

(A) Cumulative time since the start of the drive cycle is greater than or equal to 

600 seconds while at an elevation of less than 8,000 feet (2,400 meters) above sea 

level and at an ambient temperature of greater than or equal to 20 degrees 

Fahrenheit (−7 C);

(B) Cumulative gasoline engine operation at or above 25 miles per hour or diesel 

engine operation at or above 1,150 rotations per minute (diesel engines may use 

the gasoline criterion for 2010 through 2012 model years), either of which occurs 

for greater than or equal to 300 seconds while at an elevation of less than 8,000 

feet (2,400 meters) above sea level and at an ambient temperature of greater than 

or equal to 20 degrees Fahrenheit (−7 C); and,

(C) Continuous engine operation at idle (e.g., accelerator pedal released by driver 

and engine speed less than or equal to 200 rpm above normal warmed-up idle (as 

determined in the drive position for vehicles equipped with an automatic 

transmission) or vehicle speed less than or equal to one mile per hour) for greater 

than or equal to 30 seconds while at an elevation of less than 8,000 feet (2,400 

meters) above sea level and at an ambient temperature of greater than or equal to 

20 degrees Fahrenheit (−7 C).

(iii) In addition to the requirements of paragraph (d)(4)(ii) of this section, the 

evaporative system monitor denominator(s) may be incremented if and only if:
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(A) Cumulative time since the start of the drive cycle is greater than or equal to 

600 seconds while at an ambient temperature of greater than or equal to 40 

degrees Fahrenheit (4 C) but less than or equal to 95 degrees Fahrenheit (35 C); 

and,

(B) Engine cold start occurs with the engine coolant temperature greater than or 

equal to 40 degrees Fahrenheit (4 C) but less than or equal to 95 degrees 

Fahrenheit (35 C) and less than or equal to 12 degrees Fahrenheit (7 C) higher 

than the ambient temperature.

(iv) In addition to the requirements of paragraph (d)(4)(ii) of this section, the 

denominator(s) for the following monitors may be incremented if and only if the 

component or strategy is commanded “on” for a cumulative time greater than or 

equal to 10 seconds. For purposes of determining this commanded “on” time, the 

OBD system shall not include time during intrusive operation of any of the 

components or strategies that occurs later in the same drive cycle for the sole 

purpose of monitoring.

(A) Secondary air system (paragraph (h)(5) of this section).

(B) Cold start emission reduction strategy (paragraph (h)(4) of this section).

(C) Components or systems that operate only at engine start-up (e.g., glow plugs, 

intake air heaters) and are subject to monitoring under “other emission control 

systems” (paragraph (i)(4) of this section) or comprehensive component output 

components (paragraph (i)(3)(iii) of this section).

(v) In addition to the requirements of paragraph (d)(4)(ii) of this section, the 

denominator(s) for the following monitors of output components (except those 

operated only at engine start-up and subject to the requirements of paragraph 

(d)(4)(iv) of this section, may be incremented if and only if the component is 

commanded to function (e.g., commanded “on”, “opened”, “closed”, “locked”) on 

two or more occasions during the drive cycle or for a cumulative time greater than 

or equal to 10 seconds, whichever occurs first:

(A) Variable valve timing and/or control system (paragraph (g)(10) of this section 

or (h)(9) of this section).

(B) “Other emission control systems” (paragraph (i)(4) of this section).

(C) Comprehensive component output component (paragraph (i)(3) of this 

section) (e.g., turbocharger waste-gates, variable length manifold runners).

(vi) For monitors of the following components, the manufacturer may use 

alternative or additional criteria for incrementing the denominator to that set forth in 

paragraph (d)(4)(ii) of this section. To do so, the alternative criteria must be based 
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on equivalence to the criteria of paragraph (d)(4)(ii) of this section in measuring the 

frequency of monitor operation relative to the amount of engine operation:

(A) Engine cooling system input components (paragraph (i)(1) of this section).

(B) “Other emission control systems” (paragraph (i)(4) of this section).

(C) Comprehensive component input components that require extended 

monitoring evaluation (paragraph (i)(3) of this section) (e.g., stuck fuel level 

sensor rationality).

(D) Comprehensive component input component temperature sensor rationality 

monitors (paragraph (i)(3) of this section) (e.g., intake air temperature sensor, 

ambient temperature sensor, fuel temperature sensor).

(E) Diesel particulate filter (DPF) frequent regeneration (paragraph (g)(8)(ii)(B) 

of this section).

(vii) For monitors of the following components or other emission controls that 

experience infrequent regeneration events, the manufacturer may use alternative or 

additional criteria for incrementing the denominator to that set forth in paragraph 

(d)(4)(ii) of this section. To do so, the alternative criteria must be based on 

equivalence to the criteria of paragraph (d)(4)(ii) of this section in measuring the 

frequency of monitor operation relative to the amount of engine operation:

(A) NMHC converting catalyst (paragraph (g)(5) of this section).

(B) Diesel particulate filter (DPF) (paragraphs (g)(8)(ii)(A) and (g)(8)(ii)(D) of 

this section).

(viii) In addition to the requirements of paragraph (d)(4)(ii) of this section, the 

denominator(s) for the following monitors shall be incremented if and only if a 

regeneration event is commanded for a time greater than or equal to 10 seconds:

(A) DPF incomplete regeneration (paragraph (g)(8)(ii)(C) of this section).

(B) DPF active/intrusive injection (paragraph (g)(8)(ii)(E) of this section).

(ix) For hybrids that employ alternative engine start hardware or strategies (e.g., 

integrated starter and generators), or alternative fuel vehicles (e.g., dedicated, bifuel, or dual-fuel applications), the manufacturer may use alternative criteria for

incrementing the denominator to that set forth in paragraph (d)(4)(ii) of this section. 

In general, the Administrator will not approve alternative criteria for those hybrids 

that employ engine shut off only at or near idle and/or vehicle stop conditions. To 

use alternative criteria, the alternative criteria must be based on the equivalence to 

the criteria of paragraph (d)(4)(ii) of this section in measuring the amount of vehicle 

operation relative to the measure of conventional vehicle operation.
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(5) Disablement of numerators and denominators.

(i) Within 10 seconds of detecting a malfunction (i.e., a pending or a MIL-on DTC 

has been stored) that disables a monitor for which the monitoring conditions in 

paragraph (d) of this section must be met, the OBD system must stop incrementing 

the numerator and denominator for any monitor that may be disabled as a 

consequence of the detected malfunction. Within 10 seconds of the time at which 

the malfunction is no longer being detected (e.g., the pending DTC is erased

through OBD system self-clearing or through a scan tool command), incrementing 

of all applicable numerators and denominators must resume.

(ii) Within 10 seconds of the start of a power take-off unit (e.g., dump bed, snow 

plow blade, or aerial bucket, etc.) that disables a monitor for which the monitoring 

conditions in paragraph (d) of this section must be met, the OBD system must stop 

incrementing the numerator and denominator for any monitor that may be disabled 

as a consequence of power take-off operation. Within 10 seconds of the time at 

which the power take-off operation ends, incrementing of all applicable numerators 

and denominators must resume.

(iii) Within 10 seconds of detecting a malfunction (i.e., a pending or a MIL-on DTC 

has been stored) of any component used to determine if the criteria of paragraphs 

(d)(4)(ii) and (d)(4)(iii) of this section are satisfied, the OBD system must stop 

incrementing all applicable numerators and denominators. Within 10 seconds of the 

time at which the malfunction is no longer being detected (e.g., the pending DTC is 

erased through OBD system self-clearing or through a scan tool command), 

incrementing of all applicable numerators and denominators must resume.

(e) Standardized tracking and reporting of in-use monitor performance

(1) General. For monitors required to track and report in-use monitor performance 

according to paragraph (d) of this section, the performance data must be tracked and 

reported in accordance with the specifications in paragraphs (d)(2), (e), and (k)(5) of 

this section. The OBD system must separately report an in-use monitor performance 

numerator and denominator for each of the following components:

(i) For diesel engines, NMHC catalyst bank 1, NMHC catalyst bank 2, NOx catalyst 

bank 1, NOx catalyst bank 2, exhaust gas sensor bank 1, exhaust gas sensor bank 2, 

EGR/VVT system, DPF, boost pressure control system, and NOx adsorber. The 

OBD system must also report a general denominator and an ignition cycle counter 

in the standardized format specified in paragraphs (e)(5), (e)(6), and (k)(5) of this 

section.

 

(ii) For gasoline engines, catalyst bank 1, catalyst bank 2, exhaust gas sensor bank 

1, exhaust gas sensor bank 2, evaporative leak detection system, EGR/VVT system, 

and secondary air system. The OBD system must also report a general denominator 
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and an ignition cycle counter in the standardized format specified in paragraphs 

(e)(5), (e)(6), and (k)(5) of this section.

(iii) For specific components or systems that have multiple monitors that are 

required to be reported under paragraphs (g) and (h) of this section (e.g., exhaust 

gas sensor bank 1 may have multiple monitors for sensor response or other sensor 

characteristics), the OBD system must separately track numerators and 

denominators for each of the specific monitors and report only the corresponding 

numerator and denominator for the specific monitor that has the lowest numerical 

ratio. If two or more specific monitors have identical ratios, the corresponding 

numerator and denominator for the specific monitor that has the highest 

denominator must be reported for the specific component.

(2) Numerator.

(i) The OBD system must report a separate numerator for each of the applicable 

components listed in paragraph (e)(1) of this section.

(ii) The numerator(s) must be reported in accordance with the specifications in 

paragraph (k)(5)(ii) of this section.

(3) Denominator.

(i) The OBD system must report a separate denominator for each of the applicable 

components listed in paragraph (e)(1) of this section.

(ii) The denominator(s) must be reported in accordance with the specifications in 

paragraph (k)(5)(ii) of this section.

(4) Monitor performance ratio. For purposes of determining which corresponding 

numerator and denominator to report as required in paragraph (e)(1)(iii) of this 

section, the ratio must be calculated in accordance with the specifications in 

paragraph (k)(5)(iii) of this section.

(5) Ignition cycle counter.

(i) The ignition cycle counter is defined as a counter that indicates the number of 

ignition cycles a vehicle has experienced according to the specifications of 

paragraph (e)(5)(ii)(B) of this section. The ignition cycle counter must be reported 

in accordance with the specifications in paragraph (k)(5)(ii) of this section.

(ii) The ignition cycle counter must be incremented as follows:

(A) The ignition cycle counter, when incremented, must be incremented by an 

integer of one. The ignition cycle counter shall not be incremented more than 

once per ignition cycle.
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(B) The ignition cycle counter must be incremented within 10 seconds if and only 

if the engine exceeds an engine speed of 50 to 150 rpm below the normal, 

warmed-up idle speed (as determined in the drive position for engines paired with 

an automatic transmission) for at least two seconds plus or minus one second.

(iii) Within 10 seconds of detecting a malfunction (i.e., a pending or a MIL-on DTC 

has been stored) of any component used to determine if the criteria in paragraph 

(e)(5)(ii)(B) of this section are satisfied (i.e., engine speed or time of operation), the 

OBD system must stop incrementing the ignition cycle counter. Incrementing of the 

ignition cycle counter shall not be stopped for any other condition. Within 10 

seconds of the time at which the malfunction is no longer being detected (e.g., the 

pending DTC is erased through OBD system self-clearing or through a scan tool 

command), incrementing of the ignition cycle counter must resume.

(6) General denominator.

(i) The general denominator is defined as a measure of the number of times an 

engine has been operated according to the specifications of paragraph (e)(6)(ii)(B) 

of this section. The general denominator must be reported in accordance with the 

specifications in paragraph (k)(5)(ii) of this section.

(ii) The general denominator must be incremented as follows:

(A) The general denominator, when incremented, must be incremented by an 

integer of one. The general denominator shall not be incremented more than once 

per drive cycle.

(B) The general denominator must be incremented within 10 seconds if and only 

if the criteria identified in paragraph (d)(4)(ii) of this section are satisfied on a 

single drive cycle.

 

(C) Within 10 seconds of detecting a malfunction (i.e., a pending or a MIL-on 

DTC has been stored) of any component used to determine if the criteria in 

paragraph (d)(4)(ii) of this section are satisfied (i.e., vehicle speed/load, ambient 

temperature, elevation, idle operation, or time of operation), the OBD system 

must stop incrementing the general denominator. Incrementing of the general 

denominator shall not be stopped for any other condition (e.g., the disablement 

criteria in paragraphs (d)(5)(i) and (d)(5)(ii) of this section shall not disable the 

general denominator). Within 10 seconds of the time at which the malfunction is 

no longer being detected (e.g., the pending DTC is erased through OBD system 

self-clearing or through a scan tool command), incrementing of the general 

denominator must resume.

(f) Malfunction criteria determination.

(1) In determining the malfunction criteria for the diesel engine monitors required 

under paragraphs (g) and (i) of this section that are required to indicate a malfunction 
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before emissions exceed an emission threshold based on any applicable standard, the 

manufacturer must:

(i) Use the emission test cycle and standard (i.e., the transient FTP or the 

supplemental emissions test (SET)) determined by the manufacturer to provide the 

most effective monitoring conditions and robust monitor provided all other 

applicable requirements of this section are met.

(ii) Identify in the certification documentation required under paragraph (m) of this 

section, the test cycle and standard determined by the manufacturer to be the most 

stringent for each applicable monitor and the most effective and robust for each 

applicable monitor.

(iii) If the Administrator reasonably believes that a manufacturer has determined 

incorrectly the test cycle and standard that is most stringent or effective, the 

manufacturer must be able to provide emission data and/or engineering analysis 

supporting their choice of test cycle and standard.

(2) On engines equipped with emission controls that experience infrequent 

regeneration events, a manufacturer need not adjust the emission test results that are 

used to determine the malfunction criteria for monitors that are required to indicate a 

malfunction before emissions exceed a certain emission threshold. For each such 

monitor, should the manufacturer choose to adjust the emission test results, the 

manufacturer must adjust the emission result as done in accordance with the 

provisions of § 86.004-28(i) with the component for which the malfunction criteria 

are being established having been deteriorated to the malfunction threshold. The 

adjusted emission value must be used for purposes of determining whether or not the 

applicable emission threshold is exceeded.

(i) For purposes of this paragraph (f)(2), regeneration means an event, by design, 

during which emissions levels change while the emission control performance is 

being restored.

(ii) For purposes of this paragraph (f)(2), infrequent means having an expected 

frequency of less than once per transient FTP cycle.

(3) For gasoline engines, rather than meeting the malfunction criteria specified under 

paragraphs (h) and (i) of this section, the manufacturer may request approval to use 

an OBD system certified to the requirements of § 86.007-17. To do so, the 

manufacturer must demonstrate use of good engineering judgment in determining 

equivalent malfunction detection criteria to those required in this section.

(g) OBD monitoring requirements for diesel-fueled/compression-ignition engines. The 

following table shows the thresholds at which point certain components or systems, as 

specified in this paragraph (g), are considered malfunctioning.

(1) Fuel system monitoring
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(i) General. The OBD system must monitor the fuel delivery system to verify that it 

is functioning properly. The individual electronic components (e.g., actuators, 

valves, sensors, pumps) that are used in the fuel system and are not specifically 

addressed in this paragraph (g)(1) must be monitored in accordance with the 

requirements of paragraph (i)(3) of this section.

(ii) Fuel system malfunction criteria

(A) Fuel system pressure control. The OBD system must monitor the fuel 

system’s ability to control to the desired fuel pressure. This monitoring must be 

done continuously unless new hardware has to be added, in which case the 

monitoring must be done at least once per drive cycle. The OBD system must 

detect a malfunction of the fuel system’s pressure control system when the 

pressure control system is unable to maintain an engine’s emissions at or below 

the emissions thresholds for “other monitors” as shown in Table 1 of this 

paragraph (g). For engines in which no failure or deterioration of the fuel system 

pressure control could result in an engine’s emissions exceeding the applicable 

emissions thresholds, the OBD system must detect a malfunction when the system 

has reached its control limits such that the commanded fuel system pressure 

cannot be delivered. For model year 2010 to 2012 engines with a unit injector fuel 

system, this requirement may be met by conducting a functional check of the fuel 

system pressure control in lieu of monitoring for conditions that could cause an 

engine’s emissions to exceed the applicable emissions thresholds.

(B) Fuel system injection quantity. The OBD system must detect a malfunction of 

the fuel injection system when the system is unable to deliver the commanded 

quantity of fuel necessary to maintain an engine’s emissions at or below the 

emissions thresholds for “other monitors” as shown in Table 1 of this paragraph 

(g). For engines in which no failure or deterioration of the fuel injection quantity 

could result in an engine’s emissions exceeding the applicable emissions 

thresholds, the OBD system must detect a malfunction when the system has 

reached its control limits such that the commanded fuel quantity cannot be 

delivered. For model year 2010 to 2012 engines with a unit injector fuel system, 

this requirement may be met by conducting a functional check of the fuel system 

injection quantity in lieu of monitoring for conditions that could cause an engine’s 

emissions to exceed the applicable emissions thresholds.

(C) Fuel system injection timing. The OBD system must detect a malfunction of 

the fuel injection system when the system is unable to deliver fuel at the proper 

crank angle/timing (e.g., injection timing too advanced or too retarded) necessary 

to maintain an engine’s emissions at or below the emissions thresholds for “other 

monitors” as shown in Table 1 of this paragraph (g). For engines in which no 

failure or deterioration of the fuel injection timing could result in an engine’s 

emissions exceeding the applicable emissions thresholds, the OBD system must 

detect a malfunction when the system has reached its control limits such that the
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Table 1 – OBD Emissions Thresholds for Diesel-Fueled/Compression-Ignition Engines 

Meant for Placement in Applications Greater Than 14,000 Pounds GVWR (g/bhp-hr)

Notes: FEL = Family Emissions Limit; 2.5x std means a multiple of 2.5 times the applicable emissions 

standard; +0.3 means the standard or FEL plus 0.3; 0.05/+0.04 means an absolute level of 0.05 or an 

additive level of the standard or FEL plus 0.04, whichever level is higher; these emissions thresholds apply 

to the monitoring requirements of paragraph (g) of this § 86.010-18.

commanded fuel injection timing cannot be achieved. For model year 2010 to 

2012 engines with a unit injector fuel system, this requirement may be met by 

conducting a functional check of the fuel system injection timing in lieu of 

monitoring for conditions that could cause an engine’s emissions to exceed the 

applicable emissions thresholds.

(D) Combined Monitoring. For engines with a unit injector fuel system, the 

manufacturer may request Administrator approval to combine the malfunction 

criteria of paragraphs (g)(1)(ii)(A) through (g)(1)(ii)(C) of this section into one 

malfunction provided the manufacturer can demonstrate that the combined 

malfunction will satisfy the intent of each separate malfunction criteria. For 

engines with a common rail fuel system, the manufacturer may request 

Administrator approval to combine the malfunction criteria of paragraphs 

(g)(1)(ii)(B) through (g)(1)(ii)(C) of this section into one malfunction provided 

the manufacturer can demonstrate that the combined malfunction will satisfy the 

intent of each separate malfunction criteria.

(E) Fuel system feedback control. See paragraph (i)(6) of this section.
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(iii) Fuel system monitoring conditions.

(A) With the exceptions noted in this paragraph for unit injector systems, the 

OBD system must monitor continuously for malfunctions identified in paragraphs 

(g)(1)(ii)(A) and (g)(1)(ii)(E) of this section. For 2010 through 2012 unit injector 

systems, where functional monitoring is done in lieu of emission threshold 

monitoring for malfunctions identified in paragraph (g)(1)(ii)(A) of this section, 

the manufacturer must define the monitoring conditions in accordance with 

paragraphs (c) and (d) of this section. For 2013 and later unit injector systems, the 

manufacturer must define the monitoring conditions for malfunctions identified in 

paragraph (g)(1)(ii)(A) of this section in accordance with paragraphs (c) and (d) 

of this section, with the exception that monitoring must occur every time the 

monitoring conditions are met during the drive cycle rather than once per drive 

cycle as required in paragraph (c)(2) of this section.

(B) For 2010 through 2012, the manufacturer must define the monitoring 

conditions for malfunctions identified in paragraphs (g)(1)(ii)(B), (g)(1)(ii)(C), 

and (g)(1)(ii)(D) of this section in accordance with paragraphs (c) and (d) of this 

section. For 2013 and later, the manufacturer must define the monitoring 

conditions in accordance with paragraphs (c) and (d) of this section, with the 

exception that monitoring must occur every time the monitoring conditions are 

met during the drive cycle rather than once per drive cycle as required in 

paragraph (c)(2) of this section.

(iv) Fuel system MIL activation and DTC storage. The MIL must activate and 

DTCs must be stored according to the provisions of paragraph (b) of this section.

(2) Engine misfire monitoring

(i) General. The OBD system must monitor the engine for misfire causing excess 

emissions.

(ii) Engine misfire malfunction criteria.

(A) The OBD system must be capable of detecting misfire occurring in one or 

more cylinders. To the extent possible without adding hardware for this specific 

purpose, the OBD system must also identify the specific misfiring cylinder. If 

more than one cylinder is misfiring continuously, or if more than one but less than 

half of the cylinders are misfiring continuously (if the manufacturer can 

demonstrate the robustness of their monitor to the approval of the Administrator), 

a separate DTC must be stored indicating that multiple cylinders are misfiring. 

When identifying multiple cylinder misfire, the OBD system is not required to 

identify individually through separate DTCs each of the continuously misfiring 

cylinders.

(B) For model years 2013 and later, on engines equipped with sensors that can 

detect combustion or combustion quality (e.g., for use in engines with 
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homogeneous charge compression ignition (HCCI) control systems), the OBD 

system must detect a misfire malfunction causing emissions to exceed the 

applicable thresholds for “other monitors” shown in Table 1 of this paragraph (g). 

To determine what level of misfire would cause emissions to exceed the 

applicable emissions thresholds, the manufacturer must determine the percentage 

of misfire evaluated in 1,000 revolution increments that would cause emissions 

from an emission durability demonstration engine to exceed the emissions 

thresholds if the percentage of misfire were present from the beginning of the test. 

To establish this percentage of misfire, the manufacturer must use misfire events 

occurring at equally spaced, complete engine cycle intervals, across randomly 

selected cylinders throughout each 1,000-revolution increment. If this percentage 

of misfire is determined to be lower than one percent, the manufacturer may set 

the malfunction criteria at one percent. Any misfire malfunction must be detected 

if the percentage of misfire established via this testing is exceeded regardless of 

the pattern of misfire events (e.g., random, equally spaced, continuous). The 

manufacturer may employ other revolution increments besides the 1,000 

revolution increment. To do so, the manufacturer must demonstrate that the 

strategy is equally effective and timely in detecting misfire.

(iii) Engine misfire monitoring conditions.

(A) The OBD system must monitor for engine misfire during engine idle 

conditions at least once per drive cycle in which the monitoring conditions for 

misfire are met. The manufacturer must be able to demonstrate via engineering 

analysis and/or data that the self-defined monitoring conditions: are technically 

necessary to ensure robust detection of malfunctions (e.g., avoid false passes and 

false detection of malfunctions); require no more than 1000 cumulative engine 

revolutions; and, do not require any single continuous idle operation of more than 

15 seconds to make a determination that a malfunction is present (e.g., a decision 

can be made with data gathered during several idle operations of 15 seconds or 

less); or, satisfy the requirements of paragraph (c) of this section with alternative 

engine operating conditions.

(B) Manufacturers may employ alternative monitoring conditions (e.g., off-idle) 

provided the manufacturer is able to demonstrate that the alternative monitoring 

ensure equivalent robust detection of malfunctions and equivalent timeliness in 

detection of malfunctions.

(C) For model years 2013 and later, on engines equipped with sensors that can 

detect combustion or combustion quality the OBD system must monitor 

continuously for engine misfire under all positive torque engine speed and load 

conditions. If a monitoring system cannot detect all misfire patterns under all 

required engine speed and load conditions, the manufacturer may request that the 

Administrator approve the monitoring system nonetheless. In evaluating the 

manufacturer’s request, the Administrator will consider the following factors: the 

magnitude of the region(s) in which misfire detection is limited; the degree to 

which misfire detection is limited in the region(s) (i.e., the probability of detection 
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of misfire events); the frequency with which said region(s) are expected to be 

encountered in-use; the type of misfire patterns for which misfire detection is 

troublesome; and demonstration that the monitoring technology employed is not 

inherently incapable of detecting misfire under required conditions (i.e., 

compliance can be achieved on other engines). The evaluation will be based on 

the following misfire patterns: equally spaced misfire occurring on randomly 

selected cylinders; single cylinder continuous misfire; and, paired cylinder 

(cylinders firing at the same crank angle) continuous misfire.

(iv) Engine misfire MIL activation and DTC storage.

(A) General requirements for MIL activation and DTC storage are set forth in 

paragraph (b) of this section.

(B) For model years 2013 and later, on engines equipped with sensors that can 

detect combustion or combustion quality, upon detection of the percentage of 

misfire specified in paragraph (g)(2)(ii)(B) of this section, the following criteria 

shall apply for MIL activation and DTC storage: A pending DTC must be stored 

no later than after the fourth exceedance of the percentage of misfire specified in 

paragraph (g)(2)(ii) of this section during a single drive cycle; if a pending fault 

code has been stored, the OBD system must activate the MIL and store a MIL-on 

DTC within 10 seconds if the percentage of misfire specified in paragraph 

(g)(2)(ii) of this section is again exceeded four times during the drive cycle 

immediately following storage of the pending DTC, regardless of the conditions 

encountered during the drive cycle, or on the next drive cycle in which similar 

conditions are encountered to those that were occurring when the pending DTC 

was stored. Similar conditions means an engine speed within 375 rpm, engine 

load within 20 percent, and the same warm up status (i.e., cold or hot). The 

Administrator may approve other definitions of similar conditions based on 

comparable timeliness and reliability in detecting similar engine operation. The 

pending DTC may be erased at the end of the next drive cycle in which similar 

conditions are encountered to those that were occurring when the pending DTC 

was stored provided the specified percentage of misfire was not again exceeded. 

The pending DTC may also be erased if similar conditions are not encountered 

during the 80 drive cycles immediately following initial detection of the 

malfunction.

(C) For model years 2013 and later, on engines equipped with sensors that can 

detect combustion or combustion quality, the OBD system must store and erase 

freeze frame conditions either in conjunction with storing and erasing a pending 

DTC or in conjunction with storing and erasing a MIL-on DTC. If freeze frame 

conditions are stored for a malfunction other than a misfire malfunction when a 

DTC is stored as specified in paragraph (g)(2)(iv)(B) of this section, the stored 

freeze frame information must be replaced with the freeze frame information 

regarding the misfire malfunction.
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(D) For model years 2013 and later, on engines equipped with sensors that can 

detect combustion or combustion quality, upon detection of misfire according to 

paragraph (g)(2)(iv)(B) of this section, the OBD system must also store the 

following engine conditions: engine speed, load, and warm up status of the first 

misfire event that resulted in the storage of the pending DTC.

(E) For model years 2013 and later, on engines equipped with sensors that can 

detect combustion or combustion quality, the MIL may be deactivated after three 

sequential drive cycles in which similar conditions have been encountered without 

an exceedance of the specified percentage of misfire.

(3) EGR system monitoring

(i) General. The OBD system must monitor the EGR system on engines so 

equipped for low flow rate, high flow rate, and slow response malfunctions. For 

engines equipped with EGR coolers (e.g., heat exchangers), the OBD system must 

monitor the cooler for insufficient cooling malfunctions. The individual electronic 

components (e.g., actuators, valves, sensors) that are used in the EGR system must 

be monitored in accordance with the comprehensive component requirements in 

paragraph (i)(3) of this section.

(ii) EGR system malfunction criteria

(A) EGR low flow. The OBD system must detect a malfunction of the EGR 

system prior to a decrease from the manufacturer’s specified EGR flow rate that 

would cause an engine’s emissions to exceed the emissions thresholds for “other 

monitors” as shown in Table 1 of this paragraph (g). For engines in which no 

failure or deterioration of the EGR system that causes a decrease in flow could 

result in an engine’s emissions exceeding the applicable emissions thresholds, the 

OBD system must detect a malfunction when the system has reached its control 

limits such that it cannot increase EGR flow to achieve the commanded flow rate.

(B) EGR high flow. The OBD system must detect a malfunction of the EGR

system, including a leaking EGR valve (i.e., exhaust gas flowing through the 

valve when the valve is commanded closed) prior to an increase from the 

manufacturer’s specified EGR flow rate that would cause an engine’s emissions 

to exceed the emissions thresholds for “other monitors” as shown in Table 1 of 

this paragraph (g). For engines in which no failure or deterioration of the EGR 

system that causes an increase in flow could result in an engine’s emissions 

exceeding the applicable emissions thresholds, the OBD system must detect a 

malfunction when the system has reached its control limits such that it cannot 

reduce EGR flow to achieve the commanded flow rate.

(C) EGR slow response. The OBD system must detect a malfunction of the EGR 

system prior to any failure or deterioration in the capability of the EGR system to 

achieve the commanded flow rate within a manufacturer-specified time that 

would cause an engine’s emissions to exceed the emissions thresholds for “other 
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monitors” as shown in Table 1 of this paragraph (g). The OBD system must 

monitor both the capability of the EGR system to respond to a commanded 

increase in flow and the capability of the EGR system to respond to a commanded 

decrease in flow.

(D) EGR system feedback control. See paragraph (i)(6) of this section.

(E) EGR cooler performance. The OBD system must detect a malfunction of the 

EGR cooler prior to a reduction from the manufacturer’s specified cooling 

performance that would cause an engine’s emissions to exceed the emissions 

thresholds for “other monitors” as shown in Table 1 of this paragraph (g). For 

engines in which no failure or deterioration of the EGR cooler could result in an 

engine’s emissions exceeding the applicable emissions thresholds, the OBD 

system must detect a malfunction when the system has no detectable amount of 

EGR cooling.

(iii) EGR system monitoring conditions.

(A) The OBD system must monitor continuously for malfunctions identified in 

paragraphs (g)(3)(ii)(A), (g)(3)(ii)(B), and (g)(3)(ii)(D) of this section.

(B) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraph (g)(3)(ii)(C) of this section in accordance with paragraphs 

(c) and (d) of this section, with the exception that monitoring must occur every 

time the monitoring conditions are met during the drive cycle rather than once per 

drive cycle as required in paragraph (c)(2) of this section. For purposes of 

tracking and reporting as required in paragraph (d)(1) of this section, all monitors 

used to detect malfunctions identified in paragraph (g)(3)(ii)(C) of this section 

must be tracked separately but reported as a single set of values as specified in 

paragraph (e)(1)(iii) of this section.

(C) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraph (g)(3)(ii)(E) of this section in accordance with paragraphs 

(c) and (d) of this section. For purposes of tracking and reporting as required in 

paragraph (d)(1) of this section, all monitors used to detect malfunctions 

identified in paragraph (g)(3)(ii)(E) of this section must be tracked separately but 

reported as a single set of values as specified in paragraph (e)(1)(iii) of this 

section.

(D) The manufacturer may request Administrator approval to disable temporarily 

the EGR system monitor(s) under specific ambient conditions (e.g., when freezing 

may affect performance of the system) or during specific operating conditions 

(e.g., transients, extreme low or high flow conditions). The manufacturer must be 

able to demonstrate via data or engineering analysis that a reliable system monitor 

cannot be run when these conditions exist because it cannot robustly distinguish 

between a malfunctioning system and a properly operating system. The 
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manufacturer is still required to maintain comprehensive component monitoring 

as required in paragraph (i)(3) of this section.

 

(iv) EGR system MIL activation and DTC storage. The MIL must activate and 

DTCs must be stored according to the provisions of paragraph (b) of this section.

(4) Turbo boost control system monitoring

(i) General. The OBD system must monitor the boost pressure control system (e.g., 

turbocharger) on engines so equipped for under and over boost malfunctions. For 

engines equipped with variable geometry turbochargers (VGT), the OBD system 

must monitor the VGT system for slow response malfunctions. For engines 

equipped with charge air cooler systems, the OBD system must monitor the charge 

air cooler system for cooling system performance malfunctions. The individual 

electronic components (e.g., actuators, valves, sensors) that are used in the boost 

pressure control system must be monitored in accordance with the comprehensive 

component requirements in paragraph (i)(3) of this section.

(ii) Turbo boost control system malfunction criteria

(A) Turbo underboost. The OBD system must detect a malfunction of the boost 

pressure control system prior to a decrease from the manufacturer’s commanded 

boost pressure, or expected boost pressure on engines not equipped with a boost 

pressure control system, that would cause an engine’s emissions to exceed the 

emissions thresholds for “other monitors” as shown in Table 1 of this paragraph 

(g). For engines in which no failure or deterioration of the boost pressure control 

system that causes a decrease in boost could result in an engine’s emissions 

exceeding the applicable emissions thresholds, the OBD system must detect a 

malfunction when the system has reached its control limits such that it cannot 

increase boost to achieve the commanded boost pressure.

(B) Turbo overboost. The OBD system must detect a malfunction of the boost 

pressure control system on engines so equipped prior to an increase from the 

manufacturer’s commanded boost pressure that would cause an engine’s 

emissions to exceed the emissions thresholds for “other monitors” as shown in 

Table 1 of this paragraph (g). For engines in which no failure or deterioration of 

the boost pressure control system that causes an increase in boost could result in 

an engine’s emissions exceeding the applicable emissions thresholds, the OBD 

system must detect a malfunction when the system has reached its control limits 

such that it cannot decrease boost to achieve the commanded boost pressure.

(C) VGT slow response. The OBD system must detect a malfunction prior to any 

failure or deterioration in the capability of the VGT system on engines so 

equipped to achieve the commanded turbocharger geometry within a 

manufacturer-specified time that would cause an engine’s emissions to exceed the 

emissions thresholds for “other monitors” as shown in Table 1 of this paragraph 

(g). For engines in which no failure or deterioration of the VGT system response 
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could result in an engine’s emissions exceeding the applicable emissions 

thresholds, the OBD system must detect a malfunction of the VGT system when 

proper functional response of the system to computer commands does not occur.

(D) Turbo boost feedback control. See paragraph (i)(6)of this section.

(E) Charge air undercooling. The OBD system must detect a malfunction of the 

charge air cooling system prior to a decrease from the manufacturer’s specified 

cooling rate that would cause an engine’s emissions to exceed the emissions 

thresholds for “other monitors” as shown in Table 1 of this paragraph (g). For 

engines in which no failure or deterioration of the charge air cooling system that 

causes a decrease in cooling performance could result in an engine’s emissions 

exceeding the applicable emissions thresholds, the OBD system must detect a 

malfunction when the system has no detectable amount of charge air cooling.

(iii) Turbo boost monitoring conditions.

(A) The OBD system must monitor continuously for malfunctions identified in 

paragraphs (g)(4)(ii)(A), (g)(4)(ii)(B), and (g)(4)(ii)(D) of this section.

(B) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraph (g)(4)(ii)(C) of this section in accordance with paragraphs 

(c) and (d) of this section, with the exception that monitoring must occur every 

time the monitoring conditions are met during the drive cycle rather than once per 

drive cycle as required in paragraph (c)(2) of this section. For purposes of 

tracking and reporting as required in paragraph (d)(1) of this section, all monitors 

used to detect malfunctions identified in paragraph (g)(4)(ii)(C) of this section 

must be tracked separately but reported as a single set of values as specified in 

paragraph (e)(1)(iii) of this section.

(C) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraph (g)(4)(ii)(E) of this section in accordance with paragraphs 

(c) and (d) of this section. For purposes of tracking and reporting as required in 

paragraph (d)(1) of this section, all monitors used to detect malfunctions 

identified in paragraph (g)(4)(ii)(E) of this section must be tracked separately but 

reported as a single set of values as specified in paragraph (e)(1)(iii) of this 

section.

(D) The manufacturer may request Administrator approval to disable temporarily 

the turbo boost system monitor(s) during specific operating conditions (e.g., 

transients, extreme low or high flow conditions). The manufacturer must be able 

to demonstrate via data or engineering analysis that a reliable system monitor 

cannot be run when these conditions exist because it cannot robustly distinguish 

between a malfunctioning system and a properly operating system. The 

manufacturer is still required to maintain comprehensive component monitoring 

as required in paragraph (i)(3) of this section.
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(iv) Turbo boost system MIL activation and DTC storage. The MIL must activate 

and DTCs must be stored according to the provisions of paragraph (b) of this 

section.

(5) NMHC converting catalyst monitoring

(i) General. The OBD system must monitor the NMHC converting catalyst(s) for 

proper NMHC conversion capability. For purposes of this paragraph (g)(5), each 

catalyst that converts NMHC must be monitored either individually or in 

combination with others. For purposes of this paragraph (g)(5), NMHC conversion 

that may occur over the DPF or other aftertreatment devices is not included.

(ii) NMHC converting catalyst malfunction criteria

(A) NMHC converting catalyst conversion efficiency. The OBD system must 

detect a malfunction when the catalyst has no detectable amount of NMHC 

conversion capability.

(B) NMHC converting catalyst aftertreatment assistance functions. For catalysts 

used to generate an exotherm to assist DPF regeneration, the OBD system must 

detect a malfunction when the catalyst is unable to generate a sufficient exotherm 

to achieve DPF regeneration. In meeting this requirement, the OBD system must 

detect a malfunction when the DOC is unable to generate a temperature rise of 

100 degrees C, or to reach the necessary DPF regeneration temperature, within 60 

seconds of initiating an active DPF regeneration. Further, the OBD system must 

detect a malfunction when the DOC is unable to sustain the necessary 

regeneration temperature for the duration of the regeneration event. The OBD or 

control system must abort the regeneration if the regeneration temperature has not 

been reached within five minutes of initiating an active regeneration event, or if 

the regeneration temperature cannot be sustained for the duration of the 

regeneration event. As an alternative to these specific malfunction criteria, the 

manufacturer may employ different criteria. To do so, the manufacturer must 

submit a description with supporting data, subject to Administrator approval, of 

their DPF regeneration monitoring strategy. The Administrator will consider the 

strategy’s equivalence to the specific criteria stated in this paragraph when 

considering the request. Also as an alternative to these specific malfunction 

criteria, the manufacturer may employ an OBD monitor that detects a catalyst 

malfunction when the catalyst conversion capability decreases to the point that 

NMHC emissions exceed 2.5 times the applicable NMHC emission standard but 

must adjust emission test results pursuant to paragraph (f)(2) of this section. For 

catalysts located downstream of a DPF and used to convert NMHC emissions 

during DPF regeneration, the OBD system must detect a malfunction when the 

catalyst has no detectable amount of NMHC conversion capability unless the 

manufacturer can demonstrate that deterioration or malfunction of the catalyst 

will not result in emissions that exceed the applicable NMHC standard.
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(iii) NMHC converting catalyst monitoring conditions. The manufacturer must 

define the monitoring conditions for malfunctions identified in paragraphs 

(g)(5)(ii)(A) and (g)(5)(ii)(B) of this section in accordance with paragraphs (c) and 

(d) of this section. For purposes of tracking and reporting as required in paragraph 

(d)(1) of this section, all monitors used to detect malfunctions identified in 

paragraphs (g)(5)(ii)(A) and (g)(5)(ii)(B) of this section must be tracked separately 

but reported as a single set of values as specified in paragraph (e)(1)(iii) of this 

section.

(iv) NMHC converting catalyst MIL activation and DTC storage. The MIL must 

activate and DTCs must be stored according to the provisions of paragraph (b) of 

this section. The monitoring method for the NMHC converting catalyst(s) must be 

capable of detecting all instances, except diagnostic self-clearing, when a catalyst 

DTC has been erased but the catalyst has not been replaced (e.g., catalyst overtemperature histogram approaches are not acceptable).

(6) Selective catalytic reduction (SCR) and lean NOx catalyst monitoring

(i) General. The OBD system must monitor the SCR and/or the lean NOx

converting catalyst(s) for proper conversion capability. For engines equipped with 

SCR systems or other catalyst systems that use an active/intrusive reductant 

injection (e.g., active lean NOx catalysts that use diesel fuel post-injection or inexhaust injection), the OBD system must monitor the active/intrusive reductant 

injection system for proper performance. The individual electronic components 

(e.g., actuators, valves, sensors, heaters, pumps) in the active/intrusive reductant 

injection system must be monitored in accordance with the comprehensive 

component requirements in paragraph (i)(3) of this section. For purposes of this 

paragraph (g)(6), each catalyst that converts NOx must be monitored either 

individually or in combination with others.

(ii) SCR and lean NOx catalyst malfunction criteria

(A) SCR and lean NOx catalyst conversion efficiency. The OBD system must 

detect a catalyst malfunction when the catalyst conversion capability decreases to 

the point that would cause an engine’s emissions to exceed the emissions 

thresholds for NOx aftertreatment systems as shown in Table 1 of this paragraph 

(g). If no failure or deterioration of the catalyst NOx conversion capability could 

result in an engine’s emissions exceeding any of the applicable emissions 

thresholds, the OBD system must detect a malfunction when the catalyst has no 

detectable amount of NOx conversion capability.

(B) SCR and lean NOx catalyst active/intrusive reductant delivery performance. 

The OBD system must detect a malfunction prior to any failure or deterioration of 

the system to properly regulate reductant delivery (e.g., urea injection, separate 

injector fuel injection, post injection of fuel, air assisted injection/mixing) that 

would cause an engine’s emissions to exceed any of the applicable emissions 

thresholds for NOx aftertreatment systems as shown in Table 1 of this paragraph 
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(g). If no failure or deterioration of the reductant delivery system could result in 

an engine’s emissions exceeding any of the applicable thresholds, the OBD 

system must detect a malfunction when the system has reached its control limits 

such that it is no longer able to deliver the desired quantity of reductant.

(C) SCR and lean NOx catalyst active/intrusive reductant quantity. If the SCR or 

lean NOx catalyst system uses a reductant other than the fuel used for the engine, 

or uses a reservoir/tank for the reductant that is separate from the fuel tank used 

for the engine, the OBD system must detect a malfunction when there is no longer 

sufficient reductant available (e.g., the reductant tank is empty).

(D) SCR and lean NOx catalyst active/intrusive reductant quality. If the SCR or 

lean NOx catalyst system uses a reservoir/tank for the reductant that is separate 

from the fuel tank used for the engine, the OBD system must detect a malfunction 

when an improper reductant is used in the reductant reservoir/tank (e.g., the 

reductant tank is filled with something other than the reductant).

(E) SCR and lean NOx catalyst active/intrusive reductant feedback control. See 

paragraph (i)(6) of this section.

(iii) SCR and lean NOx catalyst monitoring conditions.

(A) The manufacturers must define the monitoring conditions for malfunctions 

identified in paragraphs (g)(6)(ii)(A) and (g)(6)(ii)(D) of this section in 

accordance with paragraphs (c) and (d) of this section. For purposes of tracking 

and reporting as required in paragraph (d)(1) of this section, all monitors used to 

detect malfunctions identified in paragraph (g)(6)(ii)(A) of this section must be 

tracked separately but reported as a single set of values as specified in paragraph 

(e)(1)(iii) of this section.

(B) The OBD system must monitor continuously for malfunctions identified in 

paragraphs (g)(6)(ii)(B), (g)(6)(ii)(C), and (g)(6)(ii)(E) of this section.

(iv) SCR and lean NOx catalyst MIL activation and DTC storage.

(A) For malfunctions identified in paragraph (g)(6)(ii)(A) of this section, the MIL 

must activate and DTCs must be stored according to the provisions of paragraph 

(b) of this section.

(B) For malfunctions identified in paragraphs (g)(6)(ii)(B), (g)(6)(ii)(C), and 

(g)(6)(ii)(D) of this section, the manufacturer may delay activating the MIL if the 

vehicle is equipped with an alternative indicator for notifying the vehicle operator 

of the malfunction. The alternative indicator must be of sufficient illumination 

and be located such that it is readily visible to the vehicle operator under all 

lighting conditions. If the vehicle is not equipped with such an alternative 

indicator and the OBD MIL activates, the MIL may be immediately deactivated 

and the corresponding DTC(s) erased once the OBD system has verified that the 
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reductant tank has been refilled properly and the MIL has not been activated for 

any other malfunction. The Administrator may approve other strategies that 

provide equivalent assurance that a vehicle operator would be promptly notified 

and that corrective action would be taken.

(C) The monitoring method for the SCR and lean NOx catalyst(s) must be capable 

of detecting all instances, except diagnostic self-clearing, when a catalyst DTC(s) 

has been erased but the catalyst has not been replaced (e.g., catalyst overtemperature histogram approaches are not acceptable).

(7) NOx adsorber system monitoring

(i) General. The OBD system must monitor the NOx adsorber on engines soequipped for proper performance. For engines equipped with active/intrusive 

injection (e.g., in-exhaust fuel and/or air injection) to achieve desorption of the NOx

adsorber, the OBD system must monitor the active/intrusive injection system for 

proper performance. The individual electronic components (e.g., injectors, valves, 

sensors) that are used in the active/intrusive injection system must be monitored in 

accordance with the comprehensive component requirements in paragraph (i)(3) of 

this section.

(ii) NOx adsorber system malfunction criteria

(A) NOx adsorber system capability. The OBD system must detect a NOx

adsorber malfunction when its capability (i.e., its combined adsorption and 

conversion capability) decreases to the point that would cause an engine’s NOx

emissions to exceed the emissions thresholds for NOx aftertreatment systems as 

shown in Table 1 of this paragraph (g). If no failure or deterioration of the NOx

adsorber capability could result in an engine’s NOx emissions exceeding the 

applicable emissions thresholds, the OBD system must detect a malfunction when 

the system has no detectable amount of NOx adsorber capability.

(B) NOx adsorber system active/intrusive reductant delivery performance. For 

NOx adsorber systems that use active/intrusive injection (e.g., in-cylinder post 

fuel injection, in-exhaust air-assisted fuel injection) to achieve desorption of the 

NOx adsorber, the OBD system must detect a malfunction if any failure or 

deterioration of the injection system’s ability to properly regulate injection causes 

the system to be unable to achieve desorption of the NOx adsorber.

(C) NOx adsorber system feedback control. Malfunction criteria for the NOx

adsorber and the NOx adsorber active/instrusive reductant delivery system are 

contained in paragraph (i)(6) of this section.

(iii) NOx adsorber system monitoring conditions.

(A) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraph (g)(7)(ii)(A) of this section in accordance with paragraphs 
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(c) and (d) of this section. For purposes of tracking and reporting as required in 

paragraph (d)(1) of this section, all monitors used to detect malfunctions 

identified in paragraph (g)(7)(ii)(A) of this section must be tracked separately but 

reported as a single set of values as specified in paragraph (e)(1)(iii) of this 

section.

(B) The OBD system must monitor continuously for malfunctions identified in 

paragraphs (g)(7)(ii)(B) and (g)(7)(ii)(C) of this section.

(iv) NOx adsorber system MIL activation and DTC storage. The MIL must activate 

and DTCs must be stored according to the provisions of paragraph (b) of this 

section.

(8) Diesel particulate filter (DPF) system monitoring

(i) General. The OBD system must monitor the DPF on engines so-equipped for 

proper performance. For engines equipped with active regeneration systems that use 

an active/intrusive injection (e.g., in-exhaust fuel injection, in-exhaust fuel/air 

burner), the OBD system must monitor the active/intrusive injection system for 

proper performance. The individual electronic components (e.g., injectors, valves, 

sensors) that are used in the active/intrusive injection system must be monitored in 

accordance with the comprehensive component requirements in paragraph (i)(3) of 

this section.

(ii) DPF system malfunction criteria

(A) DPF filtering performance. The OBD system must detect a malfunction prior 

to a decrease in the PM filtering capability of the DPF (e.g., cracking, melting, 

etc.) that would cause an engine’s PM emissions to exceed the emissions 

thresholds for DPF systems as shown in Table 1 of this paragraph (g). If no failure 

or deterioration of the PM filtering performance could result in an engine’s PM 

emissions exceeding the applicable emissions thresholds, the OBD system must 

detect a malfunction when no detectable amount of PM filtering occurs. As an 

alternative to a threshold monitor, the OBD system, on model year 2010 through 

2012 engines only, can be designed to detect a malfunction based on a detectable 

decrease in the expected pressure drop across the DPF for a period of 5 seconds or 

more. The monitoring area for this alternative is determined using engine speed 

and load points defined in test cycles and procedures for the supplemental 

emissions test (SET) under § 86.1360-2007. The monitoring area shall include all 

engine speed and load points greater than a region bounded by a line connecting 

mode numbers 2, 6, 3, and 13 (i.e. A100, A75, B50, and C50). At engine speeds 

greater than “speed C”, the monitor shall run whenever engine load is greater than 

50%. For purposes of this paragraph, the detectable change in pressure drop is 

determined by operating the engine at the B50 engine speed and load point (as 

described in the SET test procedures), observing the pressure drop on a clean, 

nominal DPF, and multiplying the observed pressure drop by 0.5 or other factor 

supported by data and approved by the Administrator. The detectable change in 
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pressure drop shall be reported in units of kilopascals (kPa). At time of 

certification, manufacturers shall provide the detectable change in pressure drop 

value along with OBD data stream parameters recorded with a clean DPF under 

the following nine engine speed/load operating points of the SET: A50, A75, 

A100, B50, B75, B100, C50, C75, and C100. The OBD data stream pararmeters 

to be reported are described in (k)(4)(ii) of this section and shall include the 

following: Engine speed; calculated load; air flow rate from mass air flow sensor 

(if so equipped); fuel rate; and DPF delta pressure.

(B) DPF regeneration frequency. The OBD system must detect a malfunction 

when the DPF regeneration frequency increases from (i.e., occurs more often 

than) the manufacturer’s specified regeneration frequency to a level such that it 

would cause an engine’s NMHC emissions to exceed the emissions threshold for 

DPF systems as shown in Table 1 of this paragraph (g). If no such regeneration 

frequency exists that could cause NMHC emissions to exceed the applicable 

emission threshold, the OBD system must detect a malfunction when the DPF 

regeneration frequency exceeds the manufacturer’s specified design limits for 

allowable regeneration frequency.

(C) DPF incomplete regeneration. The OBD system must detect a regeneration 

malfunction when the DPF does not properly regenerate under manufacturerdefined conditions where regeneration is designed to occur.

(D) DPF missing substrate. The OBD system must detect a malfunction if either 

the DPF substrate is completely destroyed, removed, or missing, or if the DPF 

assembly has been replaced with a muffler or straight pipe.

(E) DPF system active/intrusive injection. For DPF systems that use 

active/intrusive injection (e.g., in-cylinder post fuel injection, in-exhaust airassisted fuel injection) to achieve regeneration of the DPF, the OBD system must 

detect a malfunction if any failure or deterioration of the injection system’s ability 

to properly regulate injection causes the system to be unable to achieve 

regeneration of the DPF.

(F) DPF regeneration feedback control. See paragraph (i)(6) of this section.

(iii) DPF monitoring conditions. The manufacturer must define the monitoring 

conditions for malfunctions identified in paragraph (g)(8)(ii) of this section in 

accordance with paragraphs (c) and (d) of this section, with the exception that 

monitoring must occur every time the monitoring conditions are met during the 

drive cycle rather than once per drive cycle as required in paragraph (c)(2) of this 

section. For OBD systems designed to the alternative malfunction criteria of 

paragraph (g)(8)(ii)(A) of this section, the alternative DPF monitor shall run 

continuously whenever engine speed and load conditions are within the monitoring 

area described in paragraph (g)(8)(ii)(A). The OBD system may make a 

malfunction or potential malfunction determination during any successful 

monitoring event but shall include in the enable criteria of any subsequent 
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monitoring events a confirmed successful and complete DPF regeneration. The 

subsequent monitoring events must be conducted within an operating period that 

ensures that the detected malfunction has not “healed” due to trapped particulates in 

the compromised portion of the DPF substrate. For purposes of tracking and 

reporting as required in paragraph (d)(1) of this section, all monitors used to detect 

malfunctions identified in paragraph (g)(8)(ii) of this section must be tracked 

separately but reported as a single set of values as specified in paragraph (e)(1)(iii) 

of this section.

(iv)DPF system MIL activation and DTC storage. The MIL must activate and DTCs 

must be stored according to the provisions of paragraph (b) of this section.

(9) Exhaust gas sensor and sensor heater monitoring

(i) General. The OBD system must monitor for proper output signal, activity, 

response rate, and any other parameter that can affect emissions, all exhaust gas 

sensors (e.g., oxygen, air-fuel ratio, NOx) used for emission control system 

feedback (e.g., EGR control/feedback, SCR control/feedback, NOx adsorber 

control/feedback) and/or as a monitoring device. For engines equipped with heated 

exhaust gas sensors, the OBD system must monitor the heater for proper 

performance.

(ii) Malfunction criteria for air-fuel ratio sensors located upstream of aftertreatment 

devices

(A) Sensor performance. The OBD system must detect a malfunction prior to any 

failure or deterioration of the sensor voltage, resistance, impedance, current, 

response rate, amplitude, offset, or other characteristic(s) that would cause an 

engine’s emissions to exceed the emissions thresholds for “other monitors” as 

shown in Table 1 of this paragraph (g).

(B) Circuit integrity. The OBD system must detect malfunctions of the sensor 

related to a lack of circuit continuity or signal out-of-range values.

(C) Feedback function. The OBD system must detect a malfunction of the sensor 

if the emission control system (e.g., EGR, SCR, or NOx adsorber) is unable to use 

that sensor as a feedback input (e.g., causes limp-home or open-loop operation).

(D) Monitoring function. To the extent feasible, the OBD system must detect a 

malfunction of the sensor when the sensor output voltage, resistance, impedance, 

current, amplitude, activity, offset, or other characteristics are no longer sufficient 

for use as an OBD system monitoring device (e.g., for catalyst, EGR, SCR, or 

NOx adsorber monitoring).

(iii) Malfunction criteria for air-fuel ratio sensors located downstream of 

aftertreatment devices
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(A) Sensor performance. The OBD system must detect a malfunction prior to any 

failure or deterioration of the sensor voltage, resistance, impedance, current, 

response rate, amplitude, offset, or other characteristic(s) that would cause an 

engine’s emissions to exceed the emissions thresholds for air-fuel ratio sensors 

downstream of aftertreatment devices as shown in Table 1 of this paragraph (g).

(B) Circuit integrity. The OBD system must detect malfunctions of the sensor 

related to a lack of circuit continuity or signal out-of-range values.

(C) Feedback function. The OBD system must detect a malfunction of the sensor 

if the emission control system (e.g., EGR, SCR, or NOx absorber) is unable to use 

that sensor as a feedback input (e.g., causes limp-home or open-loop operation).

(D) Monitoring function. To the extent feasible, the OBD system must detect a 

malfunction of the sensor when the sensor output voltage, resistance, impedance, 

current, amplitude, activity, offset, or other characteristics are no longer sufficient 

for use as an OBD system monitoring device (e.g., for catalyst, EGR, SCR, or 

NOx absorber monitoring).

(iv) Malfunction criteria for NOx sensors

(A) Sensor performance. The OBD system must detect a malfunction prior to any 

failure or deterioration of the sensor voltage, resistance, impedance, current, 

response rate, amplitude, offset, or other characteristic(s) that would cause an 

engine’s emissions to exceed the emissions thresholds for NOx sensors as shown 

in Table 1 of this paragraph (g).

(B) Circuit integrity. The OBD system must detect malfunctions of the sensor 

related to a lack of circuit continuity or signal out-of-range values.

(C) Feedback function. The OBD system must detect a malfunction of the sensor 

if the emission control system (e.g., EGR, SCR, or NOx adsorber) is unable to use 

that sensor as a feedback input (e.g., causes limp-home or open-loop operation).

(D) Monitoring function. To the extent feasible, the OBD system must detect a 

malfunction of the sensor when the sensor output voltage, resistance, impedance, 

current, amplitude, activity, offset, or other characteristics are no longer sufficient 

for use as an OBD system monitoring device (e.g., for catalyst, EGR, SCR, or 

NOx adsorber monitoring).

(v) Malfunction criteria for other exhaust gas sensors. For other exhaust gas 

sensors, the manufacturer must submit a monitoring plan to the Administrator for 

approval. The plan must include data and/or engineering evaluations that 

demonstrate that the monitoring plan is as reliable and effective as the monitoring 

required in paragraphs (g)(9)(ii), (g)(9)(iii), (g)(9)(iv) of this section.

(vi) Malfunction criteria for exhaust gas sensor heaters.
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(A) The OBD system must detect a malfunction of the heater performance when 

the current or voltage drop in the heater circuit is no longer within the 

manufacturer’s specified limits for normal operation (i.e., within the criteria

required to be met by the component vendor for heater circuit performance at high 

mileage). The manufacturer may use other malfunction criteria for heater 

performance malfunctions. To do so, the manufacturer must be able to 

demonstrate via data and/or an engineering evaluation that the monitor is reliable 

and robust.

(B) The OBD system must detect malfunctions of the heater circuit including 

open or short circuits that conflict with the commanded state of the heater (e.g., 

shorted to 12 Volts when commanded to 0 Volts (ground)).

(vii) Monitoring conditions for exhaust gas sensors.

(A) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraphs (g)(9)(ii)(A), (g)(9)(iii)(A), and (g)(9)(iv)(A) of this 

section (i.e., sensor performance) in accordance with paragraphs (c) and (d) of 

this section. For purposes of tracking and reporting as required in paragraph (d)(1) 

of this section, all monitors used to detect malfunctions identified in paragraphs 

(g)(9)(ii)(A), (g)(9)(iii)(A), and (g)(9)(iv)(A) of this section must be tracked 

separately but reported as a single set of values as specified in paragraph 

(e)(1)(iii) of this section.

(B) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraphs (g)(9)(ii)(D), (g)(9)(iii)(D), and (g)(9)(iv)(D) of this 

section (i.e., monitoring function) in accordance with paragraphs (c) and (d) of 

this section with the exception that monitoring must occur every time the 

monitoring conditions are met during the drive cycle rather than once per drive 

cycle as required in paragraph (c)(2) of this section.

(C) Except as provided for in paragraph (g)(9)(vii)(D) of this section, the OBD 

system must monitor continuously for malfunctions identified in paragraphs 

(g)(9)(ii)(B), (g)(9)(ii)(C), (g)(9)(iii)(B), (g)(9)(iii)(C), (g)(9)(iv)(B), (g)(9)(iv)(C) 

of this section (i.e., circuit integrity and feedback function).

(D) A manufacturer may request approval to disable continuous exhaust gas 

sensor monitoring when an exhaust gas sensor malfunction cannot be 

distinguished from other effects (e.g., disable monitoring for out-of-range on the 

low side during fuel cut conditions). To do so, the manufacturer must demonstrate 

via data and/or engineering analyses that a properly functioning sensor cannot be 

distinguished from a malfunctioning sensor and that the disablement interval is 

limited only to that necessary for avoiding false malfunction detection.

(viii) Monitoring conditions for exhaust gas sensor heaters
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(A) The manufacturer must define monitoring conditions for malfunctions 

identified in paragraph (g)(9)(vi)(A) of this section (i.e., sensor heater 

performance) in accordance with paragraphs (c) and (d) of this section.

(B) The OBD system must monitor continuously for malfunctions identified in 

paragraph (g)(9)(vi)(B) of this section (i.e., circuit malfunctions).

(ix) Exhaust gas sensor and sensor heater MIL activation and DTC storage. The 

MIL must activate and DTCs must be stored according to the provisions of 

paragraph (b) of this section.

(10) Variable Valve Timing (VVT) system monitoring

(i) General. The OBD system must monitor the VVT system on engines so 

equipped for target error and slow response malfunctions. The individual electronic 

components (e.g., actuators, valves, sensors) that are used in the VVT system must 

be monitored in accordance with the comprehensive components requirements in 

paragraph (i)(3) of this section.

(ii) VVT system malfunction criteria

(A) VVT system target error. The OBD system must detect a malfunction prior to 

any failure or deterioration in the capability of the VVT system to achieve the 

commanded valve timing and/or control within a crank angle and/or lift tolerance 

that would cause an engine’s emissions to exceed the emission thresholds for 

“other monitors” as shown in Table 1 of this paragraph (g).

(B) VVT slow response. The OBD system must detect a malfunction prior to any 

failure or deterioration in the capability of the VVT system to achieve the 

commanded valve timing and/or control within a manufacturer-specified time that 

would cause an engine’s emissions to exceed the emission thresholds for “other 

monitors” as shown in Table 1 of this paragraph (g).

(C) For engines in which no failure or deterioration of the VVT system could 

result in an engine’s emissions exceeding the applicable emissions thresholds of 

paragraphs (g)(10)(ii)(A) and (g)(10)(ii)(B) of this section, the OBD system must 

detect a malfunction of the VVT system when proper functional response of the 

system to computer commands does not occur.

(iii) VVT system monitoring conditions. Manufacturers must define the monitoring 

conditions for VVT system malfunctions identified in paragraph (g)(10)(ii) of this 

section in accordance with paragraphs (c) and (d) of this section, with the exception 

that monitoring must occur every time the monitoring conditions are met during the 

drive cycle rather than once per drive cycle as required in paragraph (c)(2) of this 

section. For purposes of tracking and reporting as required in paragraph (d)(1) of 

this section, all monitors used to detect malfunctions identified in paragraph 
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(g)(10)(ii) of this section must be tracked separately but reported as a single set of 

values as specified in paragraph (e)(1)(iii) of this section.

(iv) VVT MIL activation and DTC storage. The MIL must activate and DTCs must 

be stored according to the provisions of paragraph (b) of this section.

(h) OBD monitoring requirements for gasoline-fueled/spark-ignition engines. The 

following table shows the thresholds at which point certain components or systems, as 

specified in this paragraph (h), are considered malfunctioning.

(1) Fuel system monitoring

(i) General. The OBD system must monitor the fuel delivery system to determine its 

ability to provide compliance with emission standards.

(ii) Fuel system malfunction criteria.

(A) The OBD system must detect a malfunction of the fuel delivery system 

(including feedback control based on a secondary oxygen sensor) when the fuel 

delivery system is unable to maintain an engine’s emissions at or below the 

emissions thresholds for “other monitors” as shown in Table 2 of this paragraph 

(h).

Table 2 – OBD Emissions Thresholds for Gasoline-Fueled/Spark-Ignition Engines Meant 

for Placement in Applications Greater Than 14,000 Pounds GVWR (g/bhp-hr)

Notes: 1.75x std means a multiple of 1.75 times the applicable emissions standard; these emissions 

thresholds apply to the monitoring requirements of paragraph (h) of this section; The evaporative emissions 

control system threshold is not, technically, an emissions threshold but rather a leak size that must be 

detected; nonetheless, for ease we refer to this as the threshold.

 

(B) Except as provided for in paragraph (h)(1)(ii)(C) of this section, if the engine 

is equipped with adaptive feedback control, the OBD system must detect a 

malfunction when the adaptive feedback control has used up all of the adjustment 

allowed by the manufacturer.

(C) If the engine is equipped with feedback control that is based on a secondary 

oxygen (or equivalent) sensor, the OBD system is not required to detect a 

malfunction of the fuel system solely when the feedback control based on a 
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secondary oxygen sensor has used up all of the adjustment allowed by the 

manufacturer. However, if a failure or deterioration results in engine emissions 

that exceed the emissions thresholds for “other monitors” as shown in Table 2 of 

this paragraph (h), the OBD system is required to detect a malfunction.

(D) The OBD system must detect a malfunction whenever the fuel control system 

fails to enter closed loop operation following engine start within a manufacturer 

specified time interval. The specified time interval must be supported by data 

and/or engineering analyses submitted by the manufacturer.

(E) The manufacturer may adjust the malfunction criteria and/or monitoring 

conditions to compensate for changes in altitude, for temporary introduction of 

large amounts of purge vapor, or for other similar identifiable operating 

conditions when such conditions occur.

(iii) Fuel system monitoring conditions. The fuel system must be monitored 

continuously for the presence of a malfunction.

(iv) Fuel system MIL activation and DTC storage.

(A) A pending DTC must be stored immediately upon the fuel system exceeding

the malfunction criteria established in paragraph (h)(1)(ii) of this section.

(B) Except as provided for in paragraph (h)(1)(iv)(C) of this section, if a pending 

DTC is stored, the OBD system must activate the MIL immediately and store a 

MIL-on DTC if a malfunction is again detected during either the drive cycle 

immediately following storage of the pending DTC regardless of the conditions 

encountered during that drive cycle, or on the next drive cycle in which similar 

conditions are encountered to those that occurred when the pending DTC was 

stored. Similar conditions means engine conditions having an engine speed within 

375 rpm, load conditions within 20 percent, and the same warm-up status (i.e., 

cold or hot) as the engine conditions stored pursuant to paragraph (h)(1)(iv)(E) of 

this section. Other definitions of similar conditions may be used but must result in 

comparable timeliness and reliability in detecting similar engine operation.

(C) The pending DTC may be erased at the end of the next drive cycle in which 

similar conditions have been encountered without having again exceeded the 

specified fuel system malfunction criteria. The pending DTC may also be erased 

if similar conditions are not encountered during the 80 drive cycles immediately 

following detection of the potential malfunction for which the pending DTC was 

stored.

(D) Storage of freeze frame conditions. The OBD system must store and erase 

freeze frame conditions either in conjunction with storing and erasing a pending 

DTC or in conjunction with storing and erasing a MIL-on DTC. Freeze frame 

information associated with a fuel system malfunction shall be stored in 
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preference to freeze frame information required elsewhere in paragraphs (h) or (i) 

of this section.

(E) Storage of fuel system conditions for determining similar conditions of 

operation. The OBD must store the engine speed, load, and warm-up status 

present at the time it first detects a potential malfunction meeting the criteria of 

paragraph (h)(1)(ii) of this section and stores a pending DTC.

(F) Deactivating the MIL. The MIL may be extinguished after three sequential 

driving cycles in which similar conditions have been encountered without 

detecting a malfunction of the fuel system.

(2) Engine misfire monitoring

(i) General.

(A) The OBD system must monitor the engine for misfire causing catalyst 

damage and misfire causing excess emissions.

(B) The OBD system must identify the specific cylinder that is misfiring. The 

manufacturer may store a general misfire DTC instead of a cylinder specific DTC 

under certain operating conditions. To do so, the manufacturer must submit data 

and/or engineering analyses that demonstrate that the misfiring cylinder cannot be 

identified reliably when the conditions occur.

(C) If more than one cylinder is misfiring, a separate DTC must be stored to 

indicate that multiple cylinders are misfiring unless otherwise allowed by this 

paragraph (h)(2). When identifying multiple cylinder misfire, the OBD system is 

not required to also identify using separate DTCs each of the misfiring cylinders 

individually. If more than 90 percent of the detected misfires occur in a single 

cylinder, an appropriate DTC may be stored that indicates the specific misfiring 

cylinder rather than storing the multiple cylinder misfire DTC. If two or more 

cylinders individually have more than 10 percent of the total number of detected 

misfires, a multiple cylinder DTC must be stored.

(ii) Engine misfire malfunction criteria

(A) Misfire causing catalyst damage. The manufacturer must determine the 

percentage of misfire evaluated in 200 revolution increments for each engine 

speed and load condition that would result in a temperature that causes catalyst 

damage. If this percentage of misfire is exceeded, it shall be considered a 

malfunction that must be detected. For every engine speed and load condition for 

which this percentage of misfire is determined to be lower than five percent, the 

manufacturer may set the malfunction criteria at five percent. The manufacturer 

may use a longer interval than 200 revolutions but only for determining, on a 

given drive cycle, the first misfire exceedance as provided in paragraph 

(h)(2)(iv)(A) of this section. To do so, the manufacturer must demonstrate that the 
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interval is not so long that catalyst damage would occur prior to the interval being 

elapsed.

(B) Misfire causing emissions to exceed the applicable thresholds. The 

manufacturer must determine the percentage of misfire evaluated in 1000 

revolution increments that would cause emissions from an emissions durability 

demonstration engine to exceed the emissions thresholds for “other monitors” as 

shown in Table 2 of this paragraph (h) if that percentage of misfire were present 

from the beginning of the test. If this percentage of misfire is exceeded, regardless 

of the pattern of misfire events (e.g., random, equally spaced, continuous), it shall 

be considered a malfunction that must be detected. To establish this percentage of 

misfire, the manufacturer must use misfire events occurring at equally spaced, 

complete engine cycle intervals, across randomly selected cylinders throughout 

each 1000-revolution increment. If this percentage of misfire is determined to be 

lower than one percent, the manufacturer may set the malfunction criteria at one 

percent. The manufacturer may use a longer interval than 1000 revolutions. To do 

so, the manufacturer must demonstrate that the strategy would be equally 

effective and timely at detecting misfire.

(iii) Engine misfire monitoring conditions.

(A) The OBD system must monitor continuously for misfire under the following 

conditions: from no later than the end of the second crankshaft revolution after 

engine start; during the rise time and settling time for engine speed to reach the 

desired idle engine speed at engine start-up (i.e., “flare-up” and “flare-down”); 

and, under all positive torque engine speeds and load conditions except within the 

engine operating region bound by the positive torque line (i.e., engine load with 

the transmission in neutral), and the points represented by an engine speed of 

3000 rpm with the engine load at the positive torque line and the redline engine 

speed with the engine’s manifold vacuum at four inches of mercury lower than 

that at the positive torque line. For this purpose, redline engine speed is defined as 

either the recommended maximum engine speed as displayed on the instrument 

panel tachometer, or the engine speed at which fuel shutoff occurs.

(B) If an OBD monitor cannot detect all misfire patterns under all required engine 

speed and load conditions as required by paragraph (h)(2)(iii)(A) of this section, 

the OBD system may still be acceptable. The Administrator will evaluate the 

following factors in making a determination: The magnitude of the region(s) in 

which misfire detection is limited; the degree to which misfire detection is limited 

in the region(s) (i.e., the probability of detection of misfire events); the frequency 

with which said region(s) are expected to be encountered in-use; the type of 

misfire patterns for which misfire detection is troublesome; and demonstration 

that the monitoring technology employed is not inherently incapable of detecting 

misfire under the required conditions (i.e., compliance can be achieved on other 

engines). The evaluation will be based on the following misfire patterns: equally 

spaced misfire occurring on randomly selected cylinders; single cylinder 
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continuous misfire; and paired cylinder (cylinders firing at the same crank angle) 

continuous misfire.

(C) The manufacturer may use monitoring system that has reduced misfire 

detection capability during the portion of the first 1000 revolutions after engine 

start that a cold start emission reduction strategy is active that reduces engine 

torque (e.g., spark retard strategies). To do so, the manufacturer must demonstrate 

that the probability of detection is greater than or equal to 75 percent during the 

worst case condition (i.e., lowest generated torque) for a vehicle operated 

continuously at idle (park/neutral idle) on a cold start between 50 and 86 degrees 

Fahrenheit and that the technology cannot reliably detect a higher percentage of 

the misfire events during the conditions.

(D) The manufacturer may disable misfire monitoring or use an alternative 

malfunction criterion when misfire cannot be distinguished from other effects. To 

do so, the manufacturer must demonstrate that the disablement interval or the 

period of use of an alternative malfunction criterion is limited only to that 

necessary for avoiding false detection and for one or more of the following 

operating conditions: Rough road; fuel cut; gear changes for manual transmission 

vehicles; traction control or other vehicle stability control activation such as antilock braking or other engine torque modifications to enhance vehicle stability; 

off-board control or intrusive activation of vehicle components or monitors during 

service or assembly plant testing; portions of intrusive evaporative system or EGR 

monitors that can significantly affect engine stability (i.e., while the purge valve is 

open during the vacuum pull-down of an evaporative system leak check but not 

while the purge valve is closed and the evaporative system is sealed or while an 

EGR monitor causes the EGR valve to be cycled intrusively on and off during 

positive torque conditions); or, engine speed, load, or torque transients due to 

throttle movements more rapid than those that occur over the FTP cycle for the 

worst case engine within each engine family. In general, the Administrator will 

not approve disablement for conditions involving normal air conditioning 

compressor cycling from on-to-off or off-to-on, automatic transmission gear shifts 

(except for shifts occurring during wide open throttle operation), transitions from 

idle to off-idle, normal engine speed or load changes that occur during the engine 

speed rise time and settling time (i.e., “flare-up” and “flare-down”) immediately 

after engine starting without any vehicle operator-induced actions (e.g., throttle 

stabs), or excess acceleration (except for acceleration rates that exceed the 

maximum acceleration rate obtainable at wide open throttle while the vehicle is in 

gear due to abnormal conditions such as slipping of a clutch). The Administrator 

may approve misfire monitoring disablement or use of an alternate malfunction 

criterion for any other condition on a case by case basis upon determining that the 

manufacturer has demonstrated that the request is based on an unusual or 

unforeseen circumstance and that it is applying the best available computer and 

monitoring technology.

(E) For engines with more than eight cylinders that cannot meet the requirements 

of paragraph (h)(2)(iii)(A) of this section, a manufacturer may use alternative 
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misfire monitoring conditions. Such use must be based on data and/or an 

engineering evaluation submitted by the manufacturer that demonstrate that 

misfire detection throughout the required operating region cannot be achieved 

when employing proven monitoring technology (i.e., a technology that provides 

for compliance with these requirements on other engines) and provided misfire is 

detected to the fullest extent permitted by the technology. However, the misfire 

detection system must still monitor during all positive torque operating conditions 

encountered during an FTP cycle.

(iv) MIL activation and DTC storage for engine misfire causing catalyst damage

(A) Pending DTCs. A pending DTC must be stored immediately if, during a 

single drive cycle, the specified misfire percentage described in paragraph 

(h)(2)(ii)(A) of this section is exceeded three times when operating in the positive 

torque region encountered during a FTP cycle or is exceeded on a single occasion 

when operating at any other engine speed and load condition in the positive 

torque region defined in paragraph (h)(2)(iii)(A) of this section. Immediately after 

a pending DTC is stored pursuant to this paragraph, the MIL must blink once per 

second at all times during the drive cycle that engine misfire is occurring. The 

MIL may be deactivated during those times that misfire is not occurring. If, at the 

time that a catalyst damaging misfire malfunction occurs, the MIL is already 

activated for a malfunction other than misfire, the MIL must still blink once per 

second at all times during the drive cycle that engine misfire is occurring. If 

misfire ceases, the MIL must stop blinking but remain activated as appropriate in 

accordance with the other malfunction.

(B) MIL-on DTCs. If a pending DTC is stored in accordance with paragraph 

(h)(2)(iv)(A) of this section, the OBD system must immediately store a MIL-on 

DTC if the percentage of misfire described in paragraph (h)(2)(ii)(A) of this 

section is again exceeded one or more times during either the drive cycle 

immediately following storage of the pending DTC, regardless of the conditions 

encountered during that drive cycle, or on the next drive cycle in which similar 

conditions are encountered to those that occurred when the pending DTC was 

stored. If, during a previous drive cycle, a pending DTC is stored in accordance 

with paragraph (h)(2)(iv)(A) of this section, a MIL-on DTC must be stored 

immediately upon exceeding the percentage misfire described in paragraph 

(h)(2)(ii)(A) of this section regardless of the conditions encountered. Upon 

storage of a MIL-on DTC, the MIL must blink once per second at all times during 

the drive cycle that engine misfire is occurring. If misfire ceases, the MIL must 

stop blinking but remain activated until the conditions are met for extinguishing 

the MIL.

(C) Erasure of pending DTCs. Pending DTCs stored in accordance with paragraph 

(h)(2)(iv)(A) of this section must be erased at the end of the next drive cycle in 

which similar conditions are encountered to those that occurred when the pending 

DTC was stored provided no exceedances have been detected of the misfire 

percentage described in paragraph (h)(2)(ii)(A) of this section. The pending DTC 
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may also be erased if similar conditions are not encountered during the next 80 

drive cycles immediately following storage of the pending DTC.

(D) Exemptions for engines with fuel shutoff and default fuel control. In engines 

that provide for fuel shutoff and default fuel control to prevent over fueling during 

catalyst damaging misfire conditions, the MIL need not blink as required by 

paragraphs (h)(2)(iv)(A) and (h)(2)(iv)(B) of this section. Instead, the MIL may 

be activated continuously upon misfire detection provided that the fuel shutoff 

and default fuel control are activated immediately upon misfire detection. Fuel 

shutoff and default fuel control may be deactivated only when the engine is 

outside of the misfire range except that the manufacturer may periodically, but not 

more than once every 30 seconds, deactivate fuel shutoff and default fuel control 

to determine if the catalyst damaging misfire is still occurring. Normal fueling 

and fuel control may be resumed if the catalyst damaging misfire is no longer 

occurring.

(E) The manufacturer may use a strategy that activates the MIL continuously 

rather than blinking the MIL during extreme catalyst damage misfire conditions 

(i.e., catalyst damage misfire occurring at all engine speeds and loads). Use of 

such a strategy must be limited to catalyst damage misfire levels that cannot be 

avoided during reasonable driving conditions. To use such a strategy, the 

manufacturer must be able to demonstrate that the strategy will encourage 

operation of the vehicle in conditions that will minimize catalyst damage (e.g., at 

low engine speeds and loads).

(v) MIL activation and DTC storage for engine misfire causing emissions to exceed 

applicable emissions thresholds.

(A) Immediately upon detection, during the first 1000 revolutions after engine 

start of the misfire percentage described in paragraph (h)(2)(ii)(B) of this section, 

a pending DTC must be stored. If such a pending DTC is stored already and 

another such exceedance of the misfire percentage is detected within the first 

1000 revolutions after engine start on any subsequent drive cycle, the MIL must 

activate and a MIL-on DTC must be stored. The pending DTC may be erased if, 

at the end of the next drive cycle in which similar conditions are encountered to 

those that occurred when the pending DTC was stored, there has been no 

exceedance of the misfire percentage described in paragraph (h)(2)(ii)(B) of this 

section. The pending DTC may also be erased if similar conditions are not 

encountered during the next 80 drive cycles immediately following storage of the 

pending DTC.

(B) No later than the fourth detection during a single drive cycle, following the 

first 1000 revolutions after engine start of the misfire percentage described in 

paragraph (h)(2)(ii)(B) of this section, a pending DTC must be stored. If such a 

pending DTC is stored already, then the MIL must activate and a MIL-on DTC 

must be stored within 10 seconds of the fourth detection of the misfire percentage 

described in paragraph (h)(2)(ii)(B) of this section during either the drive cycle 
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immediately following storage of the pending DTC, regardless of the conditions 

encountered during that drive cycle excepting those conditions within the first 

1000 revolutions after engine start, or on the next drive cycle in which similar 

conditions are encountered to those that occurred when the pending DTC was 

stored excepting those conditions within the first 1000 revolutions after engine 

start. The pending DTC may be erased if, at the end of the next drive cycle in 

which similar conditions are encountered to those that occurred when the pending 

DTC was stored, there has been no exceedance of the misfire percentage 

described in paragraph (h)(2)(ii)(B) of this section. The pending DTC may also be 

erased if similar conditions are not encountered during the next 80 drive cycles 

immediately following storage of the pending DTC.

(vi) Storage of freeze frame conditions for engine misfire.

(A) The OBD system must store and erase freeze frame conditions (as defined in 

paragraph (k)(4)(iii) of this section) either in conjunction with storing and erasing 

a pending DTC or in conjunction with storing and erasing a MIL-on DTC.

(B) If, upon storage of a DTC as required by paragraphs (h)(2)(iv) and (h)(2)(v) 

of this section, there already exist stored freeze frame conditions for a 

malfunction other than a misfire or fuel system malfunction (see paragraph (h)(1) 

of this section) then the stored freeze frame information shall be replaced with 

freeze frame information associated with the misfire malfunction.

(vii) Storage of engine conditions in association with engine misfire. Upon 

detection of the misfire percentages described in paragraphs (h)(2)(ii)(A) and 

(h)(2)(ii)(B) of this section, the following engine conditions must be stored for use 

in determining similar conditions: Engine speed, load, and warm up status of the 

first misfire event that resulted in pending DTC storage.

(viii) MIL deactivation in association with engine misfire. The MIL may be 

deactivated after three sequential drive cycles in which similar conditions have been 

encountered without an exceedance of the misfire percentages described in 

paragraphs (h)(2)(ii)(A) and (h)(2)(ii)(B) of this section.

(3) Exhaust gas recirculation system monitoring

(i) General. The OBD system must monitor the EGR system on engines so 

equipped for low and high flow rate malfunctions. The individual electronic 

components (e.g., actuators, valves, sensors) that are used in the EGR system must 

be monitored in accordance with the comprehensive component requirements in 

paragraph (i)(3) of this section.

(ii) EGR system malfunction criteria.

(A) The OBD system must detect a malfunction of the EGR system prior to a 

decrease from the manufacturer’s specified EGR flow rate that would cause an 
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engine’s emissions to exceed the emissions thresholds for “other monitors” as 

shown in Table 2 of this paragraph (h). For engines in which no failure or 

deterioration of the EGR system that causes a decrease in flow could result in an 

engine’s emissions exceeding the applicable emissions thresholds, the OBD 

system must detect a malfunction when the system has no detectable amount of 

EGR flow.

(B) The OBD system must detect a malfunction of the EGR system prior to an 

increase from the manufacturer’s specified EGR flow rate that would cause an 

engine’s emissions to exceed the emissions thresholds for “other monitors” as 

shown in Table 2 of this paragraph (h). For engines in which no failure or 

deterioration of the EGR system that causes an increase in flow could result in an 

engine’s emissions exceeding the applicable emissions thresholds, the OBD 

system must detect a malfunction when the system has reached its control limits 

such that it cannot reduce EGR flow.

(iii) EGR system monitoring conditions.

(A) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraph (h)(3)(ii) of this section in accordance with paragraphs (c) 

and (d) of this section. For purposes of tracking and reporting as required by 

paragraph (d)(1) of this section, all monitors used to detect malfunctions 

identified in paragraph (h)(3)(ii) of this section must be tracked separately but 

reported as a single set of values as specified in paragraph (e)(1)(iii) of this 

section.

(B) The manufacturer may disable temporarily the EGR monitor under conditions 

when monitoring may not be reliable (e.g., when freezing may affect performance 

of the system). To do so, the manufacturer must be able to demonstrate that the 

monitor is unreliable when such conditions exist.

(iv) EGR system MIL activation and DTC storage. The MIL must activate and 

DTCs must be stored according to the provisions of paragraph (b) of this section.

(4) Cold start emission reduction strategy monitoring

(i) General. If an engine incorporates a specific engine control strategy to reduce 

cold start emissions, the OBD system must monitor the key components (e.g., idle 

air control valve), other than secondary air, while the control strategy is active to 

ensure proper operation of the control strategy.

(ii) Cold start strategy malfunction criteria.

(A) The OBD system must detect a malfunction prior to any failure or 

deterioration of the individual components associated with the cold start emission 

reduction control strategy that would cause an engine’s emissions to exceed the 

emissions thresholds for “other monitors” as shown in Table 2 of this paragraph 
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(h). The manufacturer must establish the malfunction criteria based on data from 

one or more representative engine(s) and provide an engineering evaluation for 

establishing the malfunction criteria for the remainder of the manufacturer’s 

product line.

(B) Where no failure or deterioration of a component used for the cold start 

emission reduction strategy could result in an engine’s emissions exceeding the 

applicable emissions thresholds, the individual component must be monitored for 

proper functional response while the control strategy is active in accordance with 

the malfunction criteria in paragraphs (i)(3)(ii) and (i)(3)(iii) of this section.

(iii) Cold start strategy monitoring conditions. The manufacturer must define 

monitoring conditions for malfunctions identified in paragraph (h)(4)(ii) of this 

section in accordance with paragraphs (c) and (d) of this section.

(iv) Cold start strategy MIL activation and DTC storage. The MIL must activate 

and DTCs must be stored according to the provisions of paragraph (b) of this 

section.

(5) Secondary air system monitoring

(i) General. The OBD system on engines equipped with any form of secondary air 

delivery system must monitor the proper functioning of the secondary air delivery 

system including all air switching valve(s). The individual electronic components 

(e.g., actuators, valves, sensors) that are used in the secondary air system must be 

monitored in accordance with the comprehensive component requirements in 

paragraph (i)(3) of this section. For purposes of this paragraph (h)(5), “air flow” is 

defined as the air flow delivered by the secondary air system to the exhaust system. 

For engines using secondary air systems with multiple air flow paths/distribution 

points, the air flow to each bank (i.e., a group of cylinders that share a common 

exhaust manifold, catalyst, and control sensor) must be monitored in accordance 

with the malfunction criteria in paragraph (h)(5)(ii) of this section. Also for 

purposes of this paragraph (h)(5), “normal operation” is defined as the condition 

when the secondary air system is activated during catalyst and/or engine warm-up 

following engine start. “Normal operation” does not include the condition when the 

secondary air system is turned on intrusively for the sole purpose of monitoring.

(ii) Secondary air system malfunction criteria.

(A) Except as provided in paragraph (h)(5)(ii)(C) of this section, the OBD system 

must detect a secondary air system malfunction prior to a decrease from the 

manufacturer’s specified air flow during normal operation that would cause an 

engine’s emissions to exceed the emissions thresholds for “other monitors” as 

shown in Table 2 of this paragraph (h).

(B) Except as provided in paragraph (h)(5)(ii)(C) of this section, the OBD system 

must detect a secondary air system malfunction prior to an increase from the 
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manufacturer’s specified air flow during normal operation that would cause an 

engine’s emissions to exceed the emissions thresholds for “other monitors” as 

shown in Table 2 of this paragraph (h).

(C) For engines in which no deterioration or failure of the secondary air system 

would result in an engine’s emissions exceeding the applicable emissions 

thresholds, the OBD system must detect a malfunction when no detectable 

amount of air flow is delivered by the secondary air system during normal 

operation.

 

(iii) Secondary air system monitoring conditions. The manufacturer must define 

monitoring conditions for malfunctions identified in paragraph (h)(5)(ii) of this 

section in accordance with paragraphs (c) and (d) of this section. For purposes of 

tracking and reporting as required by paragraph (d)(1) of this section, all monitors 

used to detect malfunctions identified in paragraph (h)(5)(ii) of this section must be 

tracked separately but reported as a single set of values as specified in paragraph 

(e)(1)(iii) of this section.

(iv) Secondary air system MIL activation and DTC storage. The MIL must activate 

and DTCs must be stored according to the provisions of paragraph (b) of this 

section.

(6) Catalyst system monitoring

(i) General. The OBD system must monitor the catalyst system for proper 

conversion capability.

(ii) Catalyst system malfunction criteria. The OBD system must detect a catalyst 

system malfunction when the catalyst system’s conversion capability decreases to 

the point that emissions exceed the emissions thresholds for the catalyst system as 

shown in Table 2 of this paragraph (h).

(iii) Catalyst system monitoring conditions. The manufacturer must define 

monitoring conditions for malfunctions identified in paragraph (h)(6)(ii) of this 

section in accordance with paragraphs (c) and (d) of this section. For purposes of 

tracking and reporting as required by paragraph (d)(1) of this section, all monitors 

used to detect malfunctions identified in paragraph (h)(6)(ii) of this section must be 

tracked separately but reported as a single set of values as specified in paragraph 

(e)(1)(iii) of this section.

(iv) Catalyst system MIL activation and DTC storage.

(A) The MIL must activate and DTCs must be stored according to the provisions 

of paragraph (b) of this section.

(B) The monitoring method for the catalyst system must be capable of detecting 

when a catalyst DTC has been erased (except OBD system self erasure), but the 
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catalyst has not been replaced (e.g., catalyst overtemperature histogram 

approaches are not acceptable).

(7) Evaporative system monitoring

(i) General. The OBD system must verify purge flow from the evaporative system 

and monitor the complete evaporative system, excluding the tubing and connections 

between the purge valve and the intake manifold, for vapor leaks to the atmosphere. 

Individual components of the evaporative system (e.g. valves, sensors) must be 

monitored in accordance with the comprehensive components requirements in 

paragraph (i)(3) of this section.

(ii) Evaporative system malfunction criteria

(A) Purge monitor. The OBD system must detect an evaporative system 

malfunction when no purge flow from the evaporative system to the engine can be 

detected by the OBD system.

(B) Leak monitor. The OBD system must detect an evaporative system 

malfunction when the complete evaporative system contains a leak or leaks that 

cumulatively are greater than or equal to a leak caused by a 0.150 inch diameter 

hole.

(C) The manufacturer may demonstrate that detection of a larger hole is more 

appropriate than that specified in paragraph (h)(7)(ii)(B) of this section. To do so, 

the manufacturer must demonstrate through data and/or engineering analyses that 

holes smaller than the proposed detection size would not result in evaporative or 

running loss emissions that exceed 1.5 times the applicable evaporative emissions 

standards. Upon such a demonstration, the proposed detection size could be 

substituted for the requirement of paragraph (h)(7)(ii)(B) of this section.

(iii) Evaporative system monitoring conditions.

(A) The manufacturer must define monitoring conditions for malfunctions 

identified in paragraph (h)(7)(ii)(A) of this section in accordance with paragraphs 

(c) and (d) of this section.

(B) The manufacturer must define monitoring conditions for malfunctions 

identified in paragraph (h)(7)(ii)(B) of this section in accordance with paragraphs 

(c) and (d) of this section. For purposes of tracking and reporting as required by 

paragraph (d)(1) of this section, all monitors used to detect malfunctions 

identified in paragraph (h)(7)(ii)(B) of this section must be tracked separately but 

reported as a single set of values as specified in paragraph (e)(1)(iii) of this 

section.
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(C) The manufacturer may disable or abort an evaporative system monitor when 

the fuel tank level is over 85 percent of nominal tank capacity or during a 

refueling event.

(D) The manufacturer may request Administrator approval to run the evaporative 

system monitor during only those drive cycles characterized as cold starts 

provided such a condition is needed to ensure reliable monitoring. In making the 

request, the manufacturer must demonstrate through data and/or engineering 

analyses that a reliable monitor can only be run on drive cycles that begin with a 

specific set of cold start criteria. A set of cold start criteria based solely on 

ambient temperature exceeding engine coolant temperature will not be acceptable.

(E) The OBD system may disable temporarily the evaporative purge system to run 

an evaporative system leak monitor.

(iv) Evaporative system MIL activation and DTC storage.

(A) Except as provided for in paragraph (h)(7)(iv)(B) of this section, the MIL 

must activate and DTCs must be stored according to the provisions of paragraph 

(b) of this section.

(B) If the OBD system is capable of discerning that a system leak is being caused 

by a missing or improperly secured gas cap, the OBD system need not activate the 

MIL or store a DTC provided the vehicle is equipped with an alternative indicator 

for notifying the operator of the gas cap problem. The alternative indicator must 

be of sufficient illumination and location to be readily visible under all lighting 

conditions. If the vehicle is not equipped with such an alternative indicator, the 

MIL must activate and a DTC be stored as required in paragraph (h)(7)(iv)(A) of 

this section; however, these may be deactivated and erased, respectively, if the 

OBD system determines that the gas cap problem has been corrected and the MIL 

has not been activated for any other malfunction. The Administrator may approve

other strategies that provide equivalent assurance that a vehicle operator will be 

notified promptly of a missing or improperly secured gas cap and that corrective 

action will be undertaken.

(8) Exhaust gas sensor monitoring

(i) General.

(A) The OBD system must monitor for malfunctions the output signal, response 

rate, and any other parameter that can affect emissions of all primary (i.e., fuel 

control) exhaust gas sensors (e.g., oxygen, wide-range air/fuel). Both the lean-torich and rich-to-lean response rates must be monitored.

(B) The OBD system must also monitor all secondary exhaust gas sensors (those 

used for secondary fuel trim control or as a monitoring device) for proper output 

signal, activity, and response rate.
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(C) For engines equipped with heated exhaust gas sensor, the OBD system must 

monitor the heater for proper performance.

(ii) Primary exhaust gas sensor malfunction criteria.

(A) The OBD system must detect a malfunction prior to any failure or 

deterioration of the exhaust gas sensor output voltage, resistance, impedance, 

current, response rate, amplitude, offset, or other characteristic(s) (including drift 

or bias corrected for by secondary sensors) that would cause an engine’s 

emissions to exceed the emissions thresholds for “other monitors” as shown in 

Table 2 of this paragraph (h).

(B) The OBD system must detect malfunctions of the exhaust gas sensor caused 

by either a lack of circuit continuity or out-of-range values.

(C) The OBD system must detect a malfunction of the exhaust gas sensor when a 

sensor failure or deterioration causes the fuel system to stop using that sensor as a 

feedback input (e.g., causes default or open-loop operation).

(D) The OBD system must detect a malfunction of the exhaust gas sensor when 

the sensor output voltage, resistance, impedance, current, amplitude, activity, or 

other characteristics are no longer sufficient for use as an OBD system monitoring 

device (e.g., for catalyst monitoring).

(iii) Secondary exhaust gas sensor malfunction criteria.

(A) The OBD system must detect a malfunction prior to any failure or 

deterioration of the exhaust gas sensor voltage, resistance, impedance, current, 

response rate, amplitude, offset, or other characteristic(s) that would cause an 

engine’s emissions to exceed the emissions thresholds for “other monitors” as 

shown in Table 2 of this paragraph (h).

(B) The OBD system must detect malfunctions of the exhaust gas sensor caused 

by a lack of circuit continuity.

(C) To the extent feasible, the OBD system must detect a malfunction of the 

exhaust gas sensor when the sensor output voltage, resistance, impedance, current, 

amplitude, activity, offset, or other characteristics are no longer sufficient for use 

as an OBD system monitoring device (e.g., for catalyst monitoring).

(D) The OBD system must detect malfunctions of the exhaust gas sensor caused 

by out-of-range values.

(E) The OBD system must detect a malfunction of the exhaust gas sensor when a 

sensor failure or deterioration causes the fuel system (e.g., fuel control) to stop 

using that sensor as a feedback input (e.g., causes default or open-loop operation).
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(iv) Exhaust gas sensor heater malfunction criteria.

(A) The OBD system must detect a malfunction of the heater performance when 

the current or voltage drop in the heater circuit is no longer within the 

manufacturer’s specified limits for normal operation (i.e., within the criteria 

required to be met by the component vendor for heater circuit performance at high 

mileage). Other malfunction criteria for heater performance malfunctions may be 

used upon demonstrating via data or engineering analyses that the monitoring 

reliability and timeliness is equivalent to the stated criteria in this paragraph 

(h)(8)(iv)(A).

(B) The OBD system must detect malfunctions of the heater circuit including 

open or short circuits that conflict with the commanded state of the heater (e.g., 

shorted to 12 Volts when commanded to 0 Volts (ground)).

(v) Primary exhaust gas sensor monitoring conditions.

(A) The manufacturer must define monitoring conditions for malfunctions 

identified in paragraphs (h)(8)(ii)(A) and (h)(8)(ii)(D) of this section in 

accordance with paragraphs (c) and (d) of this section. For purposes of tracking 

and reporting as required by paragraph (d)(1) of this section, all monitors used to 

detect malfunctions identified in paragraphs (h)(8)(ii)(A) and (h)(8)(ii)(D) of this 

section must be tracked separately but reported as a single set of values as 

specified in paragraph (e)(1)(iii) of this section.

(B) Except as provided for in paragraph (h)(8)(v)(C) of this section, monitoring 

for malfunctions identified in paragraphs (h)(8)(ii)(B) and (h)(8)(ii)(C) of this 

section must be conducted continuously.

(C) The manufacturer may disable continuous primary exhaust gas sensor

monitoring when a primary exhaust gas sensor malfunction cannot be 

distinguished from other effects (e.g., disable out-of-range low monitoring during 

fuel cut conditions). To do so, the manufacturer must demonstrate via data or 

engineering analyses that a properly functioning sensor cannot be distinguished 

from a malfunctioning sensor and that the disablement interval is limited only to 

that necessary for avoiding false detection.

(vi) Secondary exhaust gas sensor monitoring conditions.

(A) The manufacturer must define monitoring conditions for malfunctions 

identified in paragraphs (h)(8)(iii)(A) through (h)(8)(iii)(C) of this section in 

accordance with paragraphs (c) and (d) of this section.

(B) Except as provided for in paragraph (h)(8)(vi)(C) of this section, monitoring 

for malfunctions identified in paragraphs (h)(8)(iii)(D) and (h)(8)(iii)(E) of this 

section must be conducted continuously.
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(C) The manufacturer may disable continuous secondary exhaust gas sensor 

monitoring when a secondary exhaust gas sensor malfunction cannot be 

distinguished from other effects (e.g., disable out-of-range low monitoring during 

fuel cut conditions). To do so, the manufacturer must demonstrate via data or 

engineering analyses that a properly functioning sensor cannot be distinguished 

from a malfunctioning sensor and that the disablement interval is limited only to 

that necessary for avoiding false detection.

(vii) Exhaust gas sensor heater monitoring conditions.

(A) The manufacturer must define monitoring conditions for malfunctions 

identified in paragraph (h)(8)(iv)(A) of this section in accordance with paragraphs 

(c) and (d) of this section.

(B) Monitoring for malfunctions identified in paragraph (h)(8)(iv)(B) of this 

section must be conducted continuously.

(viii) Exhaust gas sensor MIL activation and DTC storage. The MIL must activate 

and DTCs must be stored according to the provisions of paragraph (b) of this 

section.

(9) Variable valve timing (VVT) system monitoring\

(i) General. The OBD system must monitor the VVT system on engines so 

equipped for target error and slow response malfunctions. The individual electronic 

components (e.g., actuators, valves, sensors) that are used in the VVT system must 

be monitored in accordance with the comprehensive components requirements in 

paragraph (i)(3).

(ii) VVT system malfunction criteria

(A) VVT system target error. The OBD system must detect a malfunction prior to 

any failure or deterioration in the capability of the VVT system to achieve the 

commanded valve timing and/or control within a crank angle and/or lift tolerance 

that would cause an engine’s emissions to exceed the emission thresholds for 

“other monitors” as shown in Table 2 of this paragraph (h).

(B) VVT slow response. The OBD system must detect a malfunction prior to any 

failure or deterioration in the capability of the VVT system to achieve the 

commanded valve timing and/or control within a manufacturer-specified time that 

would cause an engine’s emissions to exceed the emission thresholds for “other 

monitors” as shown in Table 2 of this paragraph (h).

(C) For engines in which no failure or deterioration of the VVT system could 

result in an engine’s emissions exceeding the applicable emissions thresholds of 

paragraphs (h)(9)(ii)(A) and (h)(9)(ii)(B) of this section, the OBD system must 
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detect a malfunction of the VVT system when proper functional response of the 

system to computer commands does not occur.

(iii) VVT system monitoring conditions. Manufacturers must define the monitoring 

conditions for VVT system malfunctions identified in paragraph (h)(9)(ii) in 

accordance with paragraphs (c) and (d) of this section, with the exception that 

monitoring must occur every time the monitoring conditions are met during the 

drive cycle rather than once per drive cycle as required in paragraph (c)(2) of this 

section. For purposes of tracking and reporting as required in paragraph (d)(1) of 

this section, all monitors used to detect malfunctions identified in paragraph 

(h)(9)(ii) must be tracked separately but reported as a single set of values as 

specified in paragraph (e)(1)(iii) of this section.

(iv) VVT MIL activation and DTC storage. The MIL must activate and DTCs must 

be stored according to the provisions of paragraph (b) of this section.

(i) OBD monitoring requirements for all engines

(1) Engine cooling system monitoring

(i) General.

(A) The OBD system must monitor the thermostat on engines so equipped for 

proper operation.

(B) The OBD system must monitor the engine coolant temperature (ECT) sensor 

for electrical circuit continuity, out-of-range values, and rationality malfunctions.

(C) For engines that use a system other than the cooling system and ECT sensor 

(e.g., oil temperature, cylinder head temperature) to determine engine operating 

temperature for emission control purposes (e.g., to modify spark or fuel injection 

timing or quantity), the manufacturer may forego cooling system monitoring and 

instead monitor the components or systems used in their approach. To do so, the 

manufacturer must to submit data and/or engineering analyses that demonstrate 

that their monitoring plan is as reliable and effective as the monitoring required in 

this paragraph (i)(1).

(ii) Malfunction criteria for the thermostat.

(A) The OBD system must detect a thermostat malfunction if, within the 

manufacturer specified time interval following engine start, any of the following 

conditions occur: The coolant temperature does not reach the highest temperature 

required by the OBD system to enable other diagnostics; and, the coolant 

temperature does not reach a warmed-up temperature within 20 degrees 

Fahrenheit of the manufacturer’s nominal thermostat regulating temperature. For 

the second of these two conditions, the manufacturer may use a lower temperature 

for this criterion if either the manufacturer can demonstrate that the fuel, spark 
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timing, and/or other coolant temperature-based modification to the engine control 

strategies would not cause an emissions increase greater than or equal to 50 

percent of any of the applicable emissions standards; or, ambient air temperature 

is between 20 degrees Fahrenheit and 50 degrees Fahrenheit in which case, upon 

Administrator approval, the minimum coolant temperature required to be reached 

may be decreased based on the ambient air temperature.

(B) With Administrator approval, the manufacturer may use alternative 

malfunction criteria to those of paragraph (i)(1)(ii)(A) of this section and/or 

alternative monitoring conditions to those of paragraph (i)(1)(iv) of this section 

that are a function of temperature at engine start on engines that do not reach the 

temperatures specified in the malfunction criteria when the thermostat is 

functioning properly. To do so, the manufacturer is required to submit data and/or 

engineering analyses that demonstrate that a properly operating system does not 

reach the specified temperatures and that the possibility is minimized for cooling 

system malfunctions to go undetected thus disabling other OBD monitors.

(C) The manufacturer may request Administrator approval to forego monitoring 

of the thermostat if the manufacturer can demonstrate that a malfunctioning 

thermostat cannot cause a measurable increase in emissions during any reasonable 

driving condition nor cause any disablement of other OBD monitors.

(iii) Malfunction criteria for the ECT sensor

(A) Circuit integrity. The OBD system must detect malfunctions of the ECT 

sensor related to a lack of circuit continuity or out-of-range values.

(B) Time to reach closed-loop/feedback enable temperature. The OBD system 

must detect if, within the manufacturer specified time interval following engine 

start, the ECT sensor does not achieve the highest stabilized minimum 

temperature that is needed to initiate closed-loop/feedback control of all affected 

emission control systems (e.g., fuel system, EGR system). The manufacturer 

specified time interval must be a function of the engine coolant temperature 

and/or intake air temperature at startup. The manufacturer time interval must be 

supported by data and/or engineering analyses demonstrating that it provides 

robust monitoring and minimizes the likelihood of other OBD monitors being 

disabled. The manufacturer may forego the requirements of this paragraph 

(i)(1)(iii)(B) provided the manufacturer does not use engine coolant temperature 

or the ECT sensor to enable closed-loop/feedback control of any emission control 

systems.

(C) Stuck in range below the highest minimum enable temperature. To the extent 

feasible when using all available information, the OBD system must detect a 

malfunction if the ECT sensor inappropriately indicates a temperature below the 

highest minimum enable temperature required by the OBD system to enable other 

monitors (e.g., an OBD system that requires ECT to be greater than 140 degrees 

Fahrenheit to enable a diagnostic must detect malfunctions that cause the ECT 
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sensor to inappropriately indicate a temperature below 140 degrees Fahrenheit). 

The manufacturer may forego this requirement for temperature regions in which 

the monitors required under paragraphs (i)(1)(ii) or (i)(1)(iii)(B) of this section 

will detect ECT sensor malfunctions as defined in this paragraph (i)(1)(iii)(C).

(D) Stuck in range above the lowest maximum enable temperature. The OBD 

system must detect a malfunction if the ECT sensor inappropriately indicates a 

temperature above the lowest maximum enable temperature required by the OBD 

system to enable other monitors (e.g., an OBD system that requires an engine 

coolant temperature less than 90 degrees Fahrenheit at startup prior to enabling an 

OBD monitor must detect malfunctions that cause the ECT sensor to indicate 

inappropriately a temperature above 90 degrees Fahrenheit). The manufacturer 

may forego this requirement within temperature regions in which the monitors 

required under paragraphs (i)(1)(ii), (i)(1)(iii)(B), (i)(1)(iii)(C) of this section will 

detect ECT sensor malfunctions as defined in this paragraph (i)(1)(iii)(D) or in 

which the MIL will be activated according to the provisions of paragraph 

(b)(2)(v) of this section. The manufacturer may also forego this monitoring within 

temperature regions where a temperature gauge on the instrument panel indicates 

a temperature in the “red zone” (engine overheating zone) and displays the same 

temperature information as used by the OBD system.

(iv) Monitoring conditions for the thermostat.

(A) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraph (i)(1)(ii)(A) of this section in accordance with paragraph 

(c) of this section. Additionally, except as provided for in paragraphs (i)(1)(iv)(B) 

and (i)(1)(iv)(C) of this section, monitoring for malfunctions identified in 

paragraph (i)(1)(ii)(A) of this section must be conducted once per drive cycle on 

every drive cycle in which the ECT sensor indicates, at engine start, a temperature 

lower than the temperature established as the malfunction criteria in paragraph 

(i)(1)(ii)(A) of this section.

(B) The manufacturer may disable thermostat monitoring at ambient engine start 

temperatures below 20 degrees Fahrenheit.

(C) The manufacturers may request Administrator approval to suspend or disable 

thermostat monitoring if the engine is subjected to conditions that could lead to 

false diagnosis. To do so, the manufacturer must submit data and/or engineering 

analyses that demonstrate that the suspension or disablement is necessary. In 

general, the manufacturer will not be allowed to suspend or disable the thermostat 

monitor on engine starts where the engine coolant temperature at engine start is 

more than 35 degrees Fahrenheit lower than the thermostat malfunction threshold 

temperature determined under paragraph (i)(1)(ii)(A) of this section.

(v) Monitoring conditions for the ECT sensor.
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(A) Except as provided for in paragraph (i)(1)(v)(D) of this section, the OBD 

system must monitor continuously for malfunctions identified in paragraph 

monitoring for malfunctions identified in paragraph (i)(1)(iii)(A) of this section 

(i.e., circuit integrity and out-of-range).

(B) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraph (i)(1)(iii)(B) of this section in accordance with paragraph 

(c) of this section. Additionally, except as provided for in paragraph (i)(1)(v)(D) 

of this section, monitoring for malfunctions identified in paragraph (i)(1)(iii)(B) 

of this section must be conducted once per drive cycle on every drive cycle in 

which the ECT sensor indicates a temperature lower than the closed-loop enable 

temperature at engine start (i.e., all engine start temperatures greater than the ECT 

sensor out-of-range low temperature and less than the closed-loop enable 

temperature).

(C) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraphs (i)(1)(iii)(C) and (i)(1)(iii)(D) of this section in 

accordance with paragraphs (c) and (d) of this section.

(D) The manufacturer may suspend or delay the monitor for the time to reach 

closed-loop enable temperature if the engine is subjected to conditions that could 

lead to false diagnosis (e.g., vehicle operation at idle for more than 50 to 75 

percent of the warm-up time).

(E) The manufacturer may request Administrator approval to disable continuous 

ECT sensor monitoring when an ECT sensor malfunction cannot be distinguished 

from other effects. To do so, the manufacturer must submit data and/or 

engineering analyses that demonstrate a properly functioning sensor cannot be 

distinguished from a malfunctioning sensor and that the disablement interval is 

limited only to that necessary for avoiding false detection.

(vi) Engine cooling system MIL activation and DTC storage. The MIL must 

activate and DTCs must be stored according to the provisions of paragraph (b) of 

this section.

(2) Crankcase ventilation (CV) system monitoring

(i) General. The OBD system must monitor the CV system on engines so equipped 

for system integrity. Engines not required to be equipped with CV systems are 

exempt from monitoring the CV system. For diesel engines, the manufacturer must 

submit a plan for Administrator approval prior to OBD certification. That plan must 

include descriptions of the monitoring strategy, malfunction criteria, and monitoring 

conditions for CV system monitoring. The plan must demonstrate that the CV 

system monitor is of equivalent effectiveness, to the extent feasible, to the 

malfunction criteria and the monitoring conditions of this paragraph (i)(2).

(ii) Crankcase ventilation system malfunction criteria.
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(A) For the purposes of this paragraph (i)(2), “CV system” is defined as any form 

of crankcase ventilation system, regardless of whether it utilizes positive pressure. 

“CV valve” is defined as any form of valve or orifice used to restrict or control 

crankcase vapor flow. Further, any additional external CV system tubing or hoses 

used to equalize crankcase pressure or to provide a ventilation path between 

various areas of the engine (e.g., crankcase and valve cover) are considered part 

of the CV system “between the crankcase and the CV valve” and subject to the 

malfunction criteria in paragraph (i)(2)(ii)(B) of this section.

(B) Except as provided for in paragraphs (i)(2)(ii)(C) through (i)(2)(ii)(E) of this 

section, the OBD system must detect a malfunction of the CV system when a 

disconnection of the system occurs between either the crankcase and the CV 

valve, or between the CV valve and the intake manifold.

(C) The manufacturer may forego monitoring for a disconnection between the 

crankcase and the CV valve provided the CV system is designed such that the CV 

valve is fastened directly to the crankcase such that it is significantly more 

difficult to remove the CV valve from the crankcase than to disconnect the line 

between the CV valve and the intake manifold (taking aging effects into 

consideration). To do so, the manufacturer must be able to provide data and/or an 

engineering evaluation demonstrating that the CV system is so designed.

(D) The manufacturer may forego monitoring for a disconnection between the 

crankcase and the CV valve provided the CV system is designed such that it uses 

tubing connections between the CV valve and the crankcase that are: resistant to 

deterioration or accidental disconnection; significantly more difficult to 

disconnect than is the line between the CV valve and the intake manifold; and, not 

subject to disconnection per the manufacturer’s repair procedures for any non-CV 

system repair. To do so, the manufacturer must be able to provide data and/or 

engineering evaluation demonstrating that the CV system is so designed.

(E) The manufacturer may forego monitoring for a disconnection between the CV 

valve and the intake manifold provided the CV system is designed such that any 

disconnection either causes the engine to stall immediately during idle operation, 

or is unlikely to occur due to a CV system design that is integral to the induction 

system (e.g., machined passages rather than tubing or hoses). To do so, the 

manufacturer must be able to provide data and/or an engineering evaluation 

demonstrating that the CV system is so designed.

(iii) Crankcase ventilation system monitoring conditions. The manufacturer must 

define the monitoring conditions for malfunctions identified in paragraph (i)(2) of 

this section in accordance with paragraphs (c) and (d) of this section.

(iv) Crankcase ventilation system MIL activation and DTC storage. The MIL must 

activate and DTCs must be stored according to the provisions of paragraph (b) of 

this section. The stored DTC need not identify specifically the CV system (e.g., a 
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DTC for idle speed control or fuel system monitoring can be stored) if the 

manufacturer can demonstrate that additional monitoring hardware is necessary to 

make such an identification and provided the manufacturer’s diagnostic and repair 

procedures for the 

detected malfunction include directions to check the integrity of the CV system.

(3) Comprehensive component monitoring

(i) General. Except as provided for in paragraph (i)(4) of this section, the OBD 

system must detect a malfunction of any electronic engine component or system not 

otherwise described in paragraphs (g), (h), (i)(1), and (i)(2) of this section that 

either provides input to (directly or indirectly, such components may include the 

crank angle sensor, knock sensor, throttle position sensor, cam position sensor, 

intake air temperature sensor, boost pressure sensor, manifold pressure sensor, mass

air flow sensor, exhaust temperature sensor, exhaust pressure sensor, fuel pressure 

sensor, fuel composition sensor of a flexible fuel vehicle, etc.) or receives 

commands from (such components or systems may include the idle speed control 

system, glow plug system, variable length intake manifold runner systems, 

supercharger or turbocharger electronic components, heated fuel preparation 

systems, the wait-to-start lamp on diesel applications, the MIL, etc.) the onboard 

computer(s) and meets either of the criteria described in paragraphs (i)(3)(i)(A) 

and/or (i)(3)(i)(B) of this section. Note that, for the purposes of this paragraph 

(i)(3), “electronic engine component or system” does not include components that 

are driven by the engine and are not related to the control of the fueling, air 

handling, or emissions of the engine (e.g., PTO components, air conditioning 

system components, and power steering components).

(A) It can cause emissions to exceed applicable emission standards. To preclude 

monitoring, the manufacturer must be able to provide emission data showing that 

the component or system, when malfunctioning and installed on a suitable test 

engine, does not cause emissions to exceed the emission standards.

(B) It is used as part of the monitoring strategy for any other monitored system or 

component.

(ii) Comprehensive component malfunction criteria for input components.

(A) The OBD system must detect malfunctions of input components caused by a 

lack of circuit continuity and out-of-range values. In addition, where feasible, 

rationality checks must also be done and shall verify that a sensor output is neither 

inappropriately high nor inappropriately low (i.e., “two-sided” monitoring).

(B) To the extent feasible, the OBD system must separately detect and store 

different DTCs that distinguish rationality malfunctions from lack of circuit 

continuity and out-of-range malfunctions. For lack of circuit continuity and outof-range malfunctions, the OBD system must, to the extent feasible, separately 

detect and store different DTCs for each distinct malfunction (e.g., out-of-range 
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low, out-of-range high, open circuit). The OBD system is not required to store 

separate DTCs for lack of circuit continuity malfunctions that cannot be 

distinguished from other out-of-range circuit malfunctions.

(C) For input components that are used to activate alternative strategies that can 

affect emissions (e.g., AECDs, engine shutdown systems), the OBD system must 

conduct rationality checks to detect malfunctions that cause the system to activate 

erroneously or deactivate the alternative strategy. To the extent feasible when 

using all available information, the rationality check must detect a malfunction if 

the input component inappropriately indicates a value that activates or deactivates 

the alternative strategy. For example, for an alternative strategy that activates 

when the intake air temperature is greater than 120 degrees Fahrenheit, the OBD 

system must detect malfunctions that cause the intake air temperature sensor to 

indicate inappropriately a temperature above 120 degrees Fahrenheit.

(D) For engines that require precise alignment between the camshaft and the 

crankshaft, the OBD system must monitor the crankshaft position sensor(s) and 

camshaft position sensor(s) to verify proper alignment between the camshaft and 

crankshaft in addition to monitoring the sensors for circuit continuity and proper 

rationality. Proper alignment monitoring between a camshaft and a crankshaft is 

required only in cases where both are equipped with position sensors. For engines 

equipped with VVT systems and a timing belt or chain, the OBD system must 

detect a malfunction if the alignment between the camshaft and crankshaft is off 

by one or more cam/crank sprocket cogs (e.g., the timing belt/chain has slipped by 

one or more teeth/cogs). If a manufacturer demonstrates that a single tooth/cog 

misalignment cannot cause a measurable increase in emissions during any 

reasonable driving condition, the OBD system must detect a malfunction when 

the minimum number of teeth/cogs misalignment has occurred that does cause a 

measurable emission increase.

(iii) Comprehensive component malfunction criteria for output 

components/systems.

(A) The OBD system must detect a malfunction of an output component/system 

when proper functional response does not occur in response to computer 

commands. If such a functional check is not feasible, the OBD system must detect 

malfunctions of output components/systems caused by a lack of circuit continuity 

or circuit malfunction (e.g., short to ground or high voltage). For output 

component lack of circuit continuity malfunctions and circuit malfunctions, the 

OBD system is not required to store different DTCs for each distinct malfunction 

(e.g., open circuit, shorted low). Manufacturers are not required to activate an 

output component/system when it would not normally be active for the sole 

purpose of performing a functional check of it as required in this paragraph (i)(3).

(B) For gasoline engines, the idle control system must be monitored for proper 

functional response to computer commands. For gasoline engines using 

monitoring strategies based on deviation from target idle speed, a malfunction 
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must be detected when either of the following conditions occurs: The idle speed 

control system cannot achieve the target idle speed within 200 revolutions per 

minute (rpm) above the target speed or 100 rpm below the target speed; or, the 

idle speed control system cannot achieve the target idle speed within the smallest 

engine speed tolerance range required by the OBD system to enable any other 

monitors. Regarding the former of these conditions, the manufacturer may use 

larger engine speed tolerances. To do so, the manufacturer must be able to 

provide data and/or engineering analyses that demonstrate that the tolerances can 

be exceeded without a malfunction being present.

(C) For diesel engines, the idle control system must be monitored for proper 

functional response to computer commands. For diesel engines, a malfunction 

must be detected when either of the following conditions occurs: the idle fuel 

control system cannot achieve the target idle speed or fuel injection quantity 

within ±50 percent of the manufacturer-specified fuel quantity and engine speed 

tolerances; or, the idle fuel control system cannot achieve the target idle speed or 

fueling quantity within the smallest engine speed or fueling quantity tolerance 

range required by the OBD system to enable any other monitors.

(D) For model years 2010 through 2012, glow plugs must be monitored for circuit 

continuity malfunctions. For model years 2010 and later, intake air heater systems 

and, for model years 2013 and later, glow plugs must be monitored for proper 

functional response to computer commands and for circuit continuity 

malfunctions. The glow plug/intake air heater circuit(s) must be monitored for 

proper current and voltage drop. The manufacturer may use other monitoring 

strategies but must be able to provide data and/or engineering analyses that 

demonstrate reliable and timely detection of malfunctions. The OBD system must 

also detect a malfunction when a single glow plug no longer operates within the 

manufacturer’s specified limits for normal operation. If a manufacturer can 

demonstrate that a single glow plug malfunction cannot cause a measurable 

increase in emissions during any reasonable driving condition, the OBD system 

must instead detect a malfunction when the number of glow plugs needed to cause 

an emission increase is malfunctioning. To the extent feasible, the stored DTC 

must identify the specific malfunctioning glow plug(s).

(E) The wait-to-start lamp circuit and the MIL circuit must be monitored for 

malfunctions that cause either lamp to fail to activate when commanded to do so 

(e.g., burned out bulb). This monitoring of the wait-to-start lamp circuit and the 

MIL circuit is not required for wait-to-start lamps and MILs using light-emitting 

diodes (LEDs).

(iv) Monitoring conditions for input components.

(A) The OBD system must monitor input components continuously for out-ofrange values and circuit continuity. The manufacturer may disable continuous 

monitoring for circuit continuity and out-of-range values when a malfunction 

cannot be distinguished from other effects. To do so, the manufacturer must be 
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able to provide data and/or engineering analyses that demonstrate that a properly 

functioning input component cannot be distinguished from a malfunctioning input 

component and that the disablement interval is limited only to that necessary for 

avoiding false malfunction detection.

(B) For input component rationality checks (where applicable), the manufacturer 

must define the monitoring conditions for detecting malfunctions in accordance 

with paragraphs (c) and (d) of this section, with the exception that rationality 

checks must occur every time the monitoring conditions are met during the drive 

cycle rather than once per drive cycle as required in paragraph (c)(2) of this 

section.

(v) Monitoring conditions for output components/systems.

(A) The OBD system must monitor output components/systems continuously for 

circuit continuity and circuit malfunctions. The manufacturer may disable 

continuous monitoring for circuit continuity and circuit malfunctions when a 

malfunction cannot be distinguished from other effects. To do so, the 

manufacturer must be able to provide data and/or engineering analyses that 

demonstrate that a properly functioning output component/system cannot be 

distinguished from a malfunctioning one and that the disablement interval is 

limited only to that necessary for avoiding false malfunction detection.

(B) For output component/system functional checks, the manufacturer must 

define the monitoring conditions for detecting malfunctions in accordance with 

paragraphs (c) and (d) of this section. Specifically for the idle control system, the 

manufacturer must define the monitoring conditions for detecting malfunctions in 

accordance with paragraphs (c) and (d) of this section, with the exception that 

functional checks must occur every time the monitoring conditions are met during 

the drive cycle rather than once per drive cycle as required in paragraph (c)(2) of 

this section.

(vi) Comprehensive component MIL activation and DTC storage.

(A) Except as provided for in paragraphs (i)(3)(vi)(B) and (i)(3)(vi)(C) of this 

section, the MIL must activate and DTCs must be stored according to the 

provisions of paragraph (b) of this section.

(B) The MIL need not be activated in conjunction with storing a MIL-on DTC for 

any comprehensive component if: the component or system, when 

malfunctioning, could not cause engine emissions to increase by 15 percent or 

more of the applicable FTP standard during any reasonable driving condition; or, 

the component or system is not used as part of the monitoring strategy for any 

other system or component that is required to be monitored.

(C) The MIL need not be activated if a malfunction has been detected in the MIL 

circuit that prevents the MIL from activating (e.g., burned out bulb or light-
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emitting diode, LED). Nonetheless, the electronic MIL status (see paragraph 

(k)(4)(ii) of this section) must be reported as MIL commanded-on and a MIL-on 

DTC must be stored.

(4) Other emission control system monitoring

(i) General. For other emission control systems that are either not addressed in 

paragraphs (g) through (i)(3) of this section (e.g., hydrocarbon traps, homogeneous 

charge compression ignition control systems), or addressed in paragraph (i)(3) of 

this section but not corrected or compensated for by an adaptive control system 

(e.g., swirl control valves), the manufacturer must submit a plan for Administrator 

approval of the monitoring strategy, malfunction criteria, and monitoring conditions 

prior to introduction on a production engine. The plan must demonstrate the 

effectiveness of the monitoring strategy, the malfunction criteria used, the 

monitoring conditions required by the monitor, and, if applicable, the determination 

that the requirements of paragraph (i)(4)(ii) of this section are satisfied.

(ii) For engines that use emission control systems that alter intake air flow or 

cylinder charge characteristics by actuating valve(s), flap(s), etc., in the intake air 

delivery system (e.g., swirl control valve systems), the manufacturer, in addition to 

meeting the requirements of paragraph (i)(4)(i) of this section, may elect to have the 

OBD system monitor the shaft to which all valves in one intake bank are physically 

attached rather than performing a functional check of the intake air flow, cylinder 

charge, or individual valve(s)/flap(s). For non-metal shafts or segmented shafts, the 

monitor must verify all shaft segments for proper functional response (e.g., by 

verifying that the segment or portion of the shaft farthest from the actuator 

functions properly). For systems that have more than one shaft to operate valves in 

multiple intake banks, the manufacturer is not required to add more than one set of 

detection hardware (e.g., sensor, switch) per intake bank to meet this requirement.

This section is intended to exempt engine monitoring systems from having 

to monitor hybrid powertrain systems from the 2013 through the 2019 

model-years as the issues needed to accomplish such monitoring in the 

non-vertically integrated market for vehicles with GVWR > 14,000 lbs are 

addressed by engine and hybrid system manufacturers as well as 

regulatory agencies and industry groups (e.g. SAE). 

(iii) For the 2013 through the 2019 model-year, engines used with hybrid 

powertrain systems as defined in 86.010-02 are not required to monitor the hybrid 

powertrain system or components of the hybrid powertrain system.

This section is intended to ensure that EPA is provided with information 

on hybrid powertrain system diagnostic capabilities during the 2013 

through 2019 model-years without creating a significant new reporting 

responsibility for hybrid powertrain system manufacturers. It also 

requires that hybrid powertrain system manufacturers provide EPA with 

annual updates of the progress being made to integrate system diagnostics 
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with the comprehensive monitoring and standardization requirements that 

apply to engine monitoring systems as well as in achieving integration 

with the monitoring systems of 2020 and later model-year engines with 

which they will be used. It also clarifies that the OBD “certification 

process” applies to engines not hybrid powertrain systems. 

 

(iv) A hybrid powertrain system manufacturer, as defined in 86.010-02, whose 

systems are used with 2013 through 2019 model-year engines must provide 

technical description of the system’s fault detection and diagnostic capabilities to 

the Administrator. The Administrator will accept this information in the form 

provided by the manufacturer. In addition, manufacturers of hybrid powertrain 

systems must provide an annual report to the Administrator describing the 

manufacturer’s product plans, activities, and progress toward achieving integration 

of their hybrid powertrain systems such that 2020 and later-model-year engine 

monitoring systems comply with the requirements of paragraph (i)(3) of this 

section. 

(5) Exceptions to OBD monitoring requirements.

(i) The Administrator may revise the PM filtering performance malfunction criteria 

for DPFs to exclude detection of specific failure modes such as partially melted 

substrates, if the most reliable monitoring method developed requires it.

(ii) The manufacturer may disable an OBD system monitor at ambient engine start 

temperatures below 20 degrees Fahrenheit (low ambient temperature conditions 

may be determined based on intake air or engine coolant temperature at engine 

start) or at elevations higher than 8,000 feet above sea level. To do so, the 

manufacturer must submit data and/or engineering analyses that demonstrate that 

monitoring is unreliable during the disable conditions. A manufacturer may request 

that an OBD system monitor be disabled at other ambient engine start temperatures 

by submitting data and/or engineering analyses demonstrating that misdiagnosis 

would occur at the given ambient temperatures due to their effect on the component 

itself (e.g., component freezing).

(iii) The manufacturer may disable an OBD system monitor when the fuel level is 

15 percent or less of the nominal fuel tank capacity for those monitors that can be 

affected by low fuel level or running out of fuel (e.g., misfire detection). To do so, 

the manufacturer must submit data and/or engineering analyses that demonstrate 

that monitoring at the given fuel levels is unreliable, and that the OBD system is 

still able to detect a malfunction if the component(s) used to determine fuel level 

indicates erroneously a fuel level that causes the disablement.

(iv) The manufacturer may disable OBD monitors that can be affected by engine 

battery or system voltage levels.
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(A) For an OBD monitor affected by low vehicle battery or system voltages, 

manufacturers may disable monitoring when the battery or system voltage is 

below 11.0 Volts. The manufacturer may use a voltage threshold higher than 11.0 

Volts to disable monitors but must submit data and/or engineering analyses that 

demonstrate that monitoring at those voltages is unreliable and that either 

operation of a vehicle below the disablement criteria for extended periods of time 

is unlikely or the OBD system monitors the battery or system voltage and will 

detect a malfunction at the voltage used to disable other monitors.

(B) For an OBD monitor affected by high engine battery or system voltages, the 

manufacturer may disable monitoring when the battery or system voltage exceeds 

a manufacturer-defined voltage. To do so, the manufacturer must submit data 

and/or engineering analyses that demonstrate that monitoring above the 

manufacturer-defined voltage is unreliable and that either the electrical charging 

system/alternator warning light will be activated (or voltage gauge would be in 

the “red zone”) or the OBD system monitors the battery or system voltage and 

will detect a malfunction at the voltage used to disable other monitors.

(v) The manufacturer may also disable affected OBD monitors in systems designed 

to accommodate the installation of power take off (PTO) units provided monitors 

are disabled only while the PTO unit is active and the OBD readiness status (see 

paragraph (k)(4)(i) of this section) is cleared by the onboard computer (i.e., all 

monitors set to indicate “not complete” or “not ready”) while the PTO unit is 

activated. If monitors are so disabled and when the disablement ends, the readiness 

status may be restored to its state prior to PTO activation.

(6) Feedback control system monitoring. If the engine is equipped with feedback 

control of any of the systems covered in paragraphs (g), (h) and (i) of this section, 

then the OBD system must detect as malfunctions the conditions specified in this 

paragraph (i)(6) for each of the individual feedback controls.

(i) The OBD system must detect when the system fails to begin feedback control 

within a manufacturer specified time interval.

(ii) When any malfunction or deterioration causes open loop or limp-home 

operation.

(iii) When feedback control has used up all of the adjustment allowed by the 

manufacturer.

(iv) A manufacturer may temporarily disable monitoring for malfunctions specified 

in paragraph (i)(6)(iii) of this section during conditions that the specific monitor 

cannot distinguish robustly between a malfunctioning system and a properly 

operating system. To do so, the manufacturer is required to submit data and/or 

engineering analyses demonstrating that the individual feedback control system, 

when operating as designed on an engine with all emission controls working 

properly, routinely operates during these conditions while having used up all of the 
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adjustment allowed by the manufacturer. In lieu of detecting, with a system specific 

monitor, the malfunctions specified in paragraphs (i)(6)(i) and (i)(6)(ii) of this 

section the OBD system may monitor the individual parameters or components that 

are used as inputs for individual feedback control systems provided that the 

monitors detect all malfunctions that meet the criteria of paragraphs (i)(6)(i) and 

(i)(6)(ii) of this section.

(j) Production evaluation testing

(1) Verification of standardization requirements.

(i) For model years 2013 and later, the manufacturer must perform testing to verify 

that production vehicles meet the requirements of paragraphs (k)(3) and (k)(4) of 

this section relevant to the proper communication of required emissions-related 

messages to a SAE J1978 or SAE J1939 (both as specified in paragraph (k)(1) of 

this section) scan tool.

(ii) Selection of test vehicles.

(A) The manufacturer must perform this testing every model year on ten unique 

production vehicles (i.e., engine rating and chassis application combination) per 

engine family. If there are less than ten unique production vehicles for a certain 

engine family, the manufacturer must test each unique production vehicle in that 

engine family. The manufacturer must perform this testing within either three 

months of the start of engine production or one month of the start of vehicle 

production, whichever is later. The manufacturer may request approval to group 

multiple production vehicles together and test one representative vehicle per 

group. To do so, the software and hardware designed to comply with the 

standardization requirements of paragraph (k)(1) of this section (e.g., 

communication protocol message timing, number of supported data stream 

parameters, engine and vehicle communication network architecture) in the 

representative vehicle must be identical to all others in the group and any 

differences in the production vehicles cannot be relevant with respect to meeting 

the criteria of paragraph (j)(1)(iv) of this section.

(B) For 2016 and subsequent model years, the required number of vehicles to be 

tested shall be reduced to five per engine family provided zero vehicles fail the 

testing required by paragraph (j)(1) of this section for two consecutive years.

(C) For 2019 and subsequent model years, the required number of vehicles to be 

tested shall be reduced to three per engine family provided zero vehicles fail the 

testing required by paragraph (j)(1) of this section for three consecutive years.

(D) The requirement for submittal of data from one or more of the production 

vehicles shall be waived if data have been submitted previously for all of the 

production vehicles. The manufacturer may request approval to carry over data 

collected in previous model years. To do so, the software and hardware designed 
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to comply with the standardization requirements of paragraph (k)(1) of this 

section must be identical to the previous model year and there must not have been 

other hardware or software changes that affect compliance with the 

standardization requirements.

 

(iii) Test equipment. For the testing required by paragraph (j)(1) of this section, the 

manufacturer shall use an off-board device to conduct the testing. The manufacturer 

must be able to show that the off-board device is able to verify that the vehicles 

tested using the device are able to perform all of the required functions in paragraph 

(j)(1)(iv) of this section with any other off-board device designed and built in 

accordance with the SAE J1978 or SAE J1939 (both as specified in paragraph 

(k)(1) of this section) generic scan tool specifications.

(iv) Required testing. The testing must verify that communication can be 

established properly between all emission-related on-board computers and a SAE 

J1978 or SAE J1939 (both as specified in paragraph (k)(1) of this section) scan tool 

designed to adhere strictly to the communication protocols allowed in paragraph 

(k)(3) of this section. The testing must also verify that all emission-related 

information is communicated properly between all emission-related on-board 

computers and a SAE J1978 or SAE J1939 (both as specified in paragraph (k)(1) of 

this section) scan tool in accordance with the requirements of paragraph (k)(1) of 

this section and the applicable ISO and SAE specifications including specifications 

for physical layer, network layer, message structure, and message content. The 

testing must also verify that the onboard computer(s) can properly respond to a SAE 

J1978 or SAE J1939 (both as specified in paragraph (k)(1) of this section) scan tool 

request to clear emissions-related DTCs and reset the ready status in accordance 

with paragraph (k)(4)(ix) of this section. The testing must further verify that the 

following information can be properly communicated to a SAE J1978 or SAE 

J1939 (both as specified in paragraph (k)(1) of this section) scan tool:

(A) The current ready status from all onboard computers required to support ready 

status in accordance with SAE J1978 or SAE J1939-73 (both as specified in 

paragraph (k)(1) of this section) and paragraph (k)(4)(i) of this section in the keyon, engine-off position and while the engine is running.

(B) The MIL command status while a deactivated MIL is commanded and while 

an activated MIL is commanded in accordance with SAE J1979 or SAE J1939 

(both as specified in paragraph (k)(1) of this section) and paragraph (k)(4)(ii) of 

this section in the key-on, engine-off position and while the engine is running, and 

in accordance with SAE J1979 or SAE J1939 (both as specified in paragraph 

(k)(1) of this section) and paragraphs (b)(1)(ii) of this section during the MIL 

functional check, if applicable, and, if applicable, (k)(4)(i)(C) of this section 

during the MIL ready status check while the engine is off.

(C) All data stream parameters required in paragraph (k)(4)(ii) of this section in 

accordance with SAE J1979 or SAE J1939 (both as specified in paragraph (k)(1) 
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of this section) including, if applicable, the proper identification of each data 

stream parameter as supported in SAE J1979 (e.g., Mode/Service $01, PID $00).

(D) The CAL ID, CVN, and VIN as required by paragraphs (k)(4)(vi), (k)(4)(vii), 

and (k)(4)(viii) of this section and in accordance with SAE J1979 or SAE J1939 

(both as specified in paragraph (k)(1) of this section).

(E) An emissions-related DTC (permanent, pending, MIL-on, previous-MIL-on) 

in accordance with SAE J1979 or SAE J1939-73 (both as specified in paragraph 

(k)(1) of this section) including the correct indication of the number of stored 

DTCs (e.g., Mode/Service $01, PID $01, Data A for SAE J1979 (as specified in 

paragraph (k)(1) of this section)) and paragraph (k)(4)(iv) of this section.

(v) Reporting of results. The manufacturer must submit to the Administrator the 

following, based on the results of the testing required by paragraph (j)(1)(iv) of this 

section:

(A) If a variant meets all the requirements of paragraph (j)(1)(iv) of this section, a 

statement specifying that the variant passed all the tests. Upon request from the 

Administrator, the detailed results of any such testing may have to be submitted.

(B) If any variant does not meet the requirements paragraph (j)(1)(iv) of this 

section, a written report detailing the problem(s) identified and the manufacturer’s 

proposed corrective action (if any) to remedy the problem(s). This report must be 

submitted within one month of testing the specific variant. The Administrator will 

consider the proposed remedy and, if in disagreement, will work with the 

manufacturer to propose an alternative remedy. Factors to be considered by the 

Administrator in considering the proposed remedy will include the severity of the 

problem(s), the ability of service technicians to access the required diagnostic 

information, the impact on equipment and tool manufacturers, and the amount of 

time prior to implementation of the proposed corrective action.

(vi) Alternative testing protocols. Manufacturers may request approval to use other 

testing protocols. To do so, the manufacturer must demonstrate that the alternative 

testing methods and equipment will provide an equivalent level of verification of 

compliance with the standardization requirements as is required by paragraph (j)(1) 

of this section.

(2) Verification of monitoring requirements.

(i) Within either the first six months of the start of engine production or the first 

three months of the start of vehicle production, whichever is later, the manufacturer 

must conduct a complete evaluation of the OBD system of one or more production 

vehicles (test vehicles) and submit the results of the evaluation to the Administrator.

(ii) Selection of test vehicles.
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(A) For each engine selected for monitoring system demonstration in paragraph 

(l) of this section, the manufacturer must evaluate one production vehicle 

equipped with an engine from the same engine family and rating as the 

demonstration engine. The vehicle selection must be approved by the 

Administrator.

(B) If the manufacturer is required to test more than one test vehicle, the 

manufacturer may test an engine in lieu of a vehicle for all but one of the required 

test vehicles.

(C) The requirement for submittal of data from one or more of the test vehicles 

may be waived if data have been submitted previously for all of the engine ratings 

and variants.

(iii) Evaluation requirements.

(A) The evaluation must demonstrate the ability of the OBD system on the 

selected test vehicle to detect a malfunction, activate the MIL, and, where 

applicable, store an appropriate DTC readable by a scan tool when a malfunction 

is present and the monitoring conditions have been satisfied for each individual 

monitor required by this section. For model years 2013 and later, the evaluation 

must demonstrate the ability of the OBD system on the selected test vehicle to 

detect a malfunction, activate the MIL, and, where applicable, store an 

appropriate DTC readable by a SAE J1978 or SAE J1939 (both as specified in 

paragraph (k)(1) of this section) scan tool when a malfunction is present and the 

monitoring conditions have been satisfied for each individual monitor required by 

this section.

(B) The evaluation must verify that the malfunction of any component used to 

enable another OBD monitor but that does not itself result in MIL activation (e.g.,

fuel level sensor) will not inhibit the ability of other OBD monitors to detect 

malfunctions properly.

(C) The evaluation must verify that the software used to track the numerator and 

denominator for the purpose of determining in-use monitoring frequency

increments as required by paragraph (d)(2) of this section.

(D) Malfunctions may be implanted mechanically or simulated electronically, but 

internal onboard computer hardware or software changes shall not be used to 

simulate malfunctions. For monitors that are required to indicate a malfunction 

before emissions exceed an emission threshold, manufacturers are not required to 

use malfunctioning components/systems set exactly at their malfunction criteria 

limits. Emission testing is not required to confirm that the malfunction is detected 

before the appropriate emission thresholds are exceeded.
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(E) The manufacturer must submit a proposed test plan for approval prior to 

performing evaluation testing. The test plan must identify the method used to 

induce a malfunction for each monitor.

(F) If the demonstration of a specific monitor cannot be reasonably performed 

without causing physical damage to the test vehicle (e.g., onboard computer 

internal circuit malfunctions), the manufacturer may omit the specific 

demonstration.

 

(G) For evaluation of test vehicles selected in accordance with paragraph (j)(2)(ii) 

of this section, the manufacturer is not required to demonstrate monitors that were 

demonstrated prior to certification as required in paragraph (l) of this section.

(iv) The manufacturer must submit a report of the results of all testing conducted as 

required by paragraph (j)(2) of this section. The report must identify the method 

used to induce a malfunction in each monitor, the MIL activation status, and the 

DTC(s) stored.

(3) Verification of in-use monitoring performance ratios.

(i) The manufacturer must collect and report in-use monitoring performance data 

representative of production vehicles (i.e., engine rating and chassis application 

combination). The manufacturer must collect and report the data to the 

Administrator within 12 months after the first production vehicle was first 

introduced into commerce.

(ii) The manufacturer must separate production vehicles into the monitoring 

performance groups and submit data that represents each of these groups. The 

groups shall be based on the following criteria:

(A) Emission control system architecture. All engines that use the same or similar 

emissions control system architecture (e.g., EGR with DPF and SCR; EGR with 

DPF and NOx adsorber; EGR with DPF-only) and associated monitoring system 

would be in the same emission architecture category.

(B) Vehicle application type. Within an emission architecture category, engines 

shall be separated into one of three vehicle application types: Engines intended 

primarily for line-haul chassis applications, engines intended primarily for urban 

delivery chassis applications, and all other engines.

(iii) The manufacturer may use an alternative grouping method to collect 

representative data. To do so, the manufacturer must show that the alternative 

groups include production vehicles using similar emission controls, OBD strategies, 

monitoring condition calibrations, and vehicle application driving/usage patterns 

such that they are expected to have similar in-use monitoring performance. The 

manufacturer will still be required to submit one set of data for each of the 

alternative groups.
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(iv) For each monitoring performance group, the data must include all of the in-use 

performance tracking data (i.e., all numerators, denominators, the general 

denominator, and the ignition cycle counter), the date the data were collected, the 

odometer reading, the VIN, and the calibration ID. For model years 2013 and later, 

for each monitoring performance group, the data must include all of the in-use 

performance tracking data reported through SAE J1979 or SAE J1939 (both as 

specified in paragraph (k)(1) of this section; i.e., all numerators, denominators, the 

general denominator, and the ignition cycle counter), the date the data were 

collected, the odometer reading, the VIN, and the calibration ID.

(v) The manufacturer must submit a plan to the Administrator that details the types 

of production vehicles in each monitoring performance group, the number of 

vehicles per group to be sampled, the sampling method, the timeline to collect the 

data, and the reporting format. The plan must provide for effective collection of 

data from, at least, 15 vehicles per monitoring performance group and provide for 

data that represent a broad range of temperature conditions. The plan shall not, by 

design, exclude or include specific vehicles in an attempt to collect data only from 

vehicles expected to have the highest in-use performance ratios.

(vi) The 12 month deadline for reporting may be extended to 18 months if the 

manufacturer can show that the delay is justified. In such a case, an interim report 

of progress to date must be submitted within the 12 month deadline.

(k) Standardization requirements

(1) Reference materials. The following documents are incorporated by reference, see 

§ 86.1. Anyone may inspect copies at the U.S. EPA or at the National Archives and 

Records Administration (NARA). For information on the availability of this material 

at U.S. EPA, NARA, or the standard making bodies directly, refer to § 86.1.

(i) SAE J1930, Revised April 2002.

(ii) SAE J1939, Revised October 2007.

 

(iii) SAE J1939-13, Revised March 2004, for model years 2013 and later.

(iv) SAE J1939-73, Revised September 2006.

(v) SAE J1962, Revised April 2002, for model years 2013 and later.

(vi) SAE J1978, Revised April 2002.

(vii) SAE J1979, Revised May 2007.

(viii) SAE J2012, Revised April 2002.
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(ix) SAE J2403, Revised August 2007.

(x) ISO 15765-4:2005(E), January 15, 2005.

(2) Diagnostic connector. For model years 2010 through 2012, the manufacturer 

defined data link connector must be accessible to a trained service technician. For 

model years 2013 and later, a standard data link connector conforming to SAE J1962 

(as specified in paragraph (k)(1) of this section) or SAE J1939-13 (as specified in 

paragraph (k)(1) of this section) specifications (except as provided for in paragraph 

(k)(2)(iii) if this section) must be included in each vehicle.

(i) For model years 2013 and later, the connector must be located in the driver’s 

side foot-well region of the vehicle interior in the area bound by the driver’s side of 

the vehicle and the driver’s side edge of the center console (or the vehicle centerline 

if the vehicle does not have a center console) and at a location no higher than the 

bottom of the steering wheel when in the lowest adjustable position. The connector 

shall not be located on or in the center console (i.e., neither on the horizontal faces 

near the floor-mounted gear selector, parking brake lever, or cup-holders nor on the 

vertical faces near the car stereo, climate system, or navigation system controls). 

The location of the connector shall be capable of being easily identified and 

accessed (e.g., to connect an off-board tool). For vehicles equipped with a driver’s 

side door, the connector must be identified and accessed easily by someone 

standing (or “crouched”) on the ground outside the driver’s side of the vehicle with 

the driver’s side door open. The Administrator may approve an alternative location 

upon request from the manufacturer. In all cases, the installation position of the 

connector must be both identified and accessed easily by someone standing outside 

the vehicle and protected from accidental damage during normal vehicle use.

(ii) For model years 2013 and later, if the connector is covered, the cover must be 

removable by hand without the use of any tools and be labeled “OBD” to aid 

technicians in identifying the location of the connector. Access to the diagnostic 

connector shall not require opening or the removal of any storage accessory (e.g., 

ashtray, coinbox). The label must clearly identify that the connector is located 

behind the cover and is consistent with language and/or symbols commonly used in

the automobile and/or heavy truck industry.

(iii) For model years 2013 and later, if the ISO 15765-4:2005(E) (as specified in 

paragraph (k)(1) of this section) communication protocol is used for the required 

OBD standardized functions, the connector must meet the “Type A” specifications 

of SAE J1962 (as specified in paragraph (k)(1) of this section). Any pins in the 

connector that provide electrical power must be properly fused to protect the 

integrity and usefulness of the connector for diagnostic purposes and shall not 

exceed 20.0 Volts DC regardless of the nominal vehicle system or battery voltage 

(e.g., 12V, 24V, 42V).

(iv) For model years 2013 and later, if the SAE J1939 (as specified in paragraph 

(k)(1) of this section) protocol is used for the required OBD standardized functions, 
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the connector must meet the specifications of SAE J1939-13 (as specified in 

paragraph (k)(1) of this section). Any pins in the connector that provide electrical 

power must be properly fused to protect the integrity and usefulness of the 

connector for diagnostic purposes.

(v) For model years 2013 and later, the manufacturer may equip engines/vehicles 

with additional diagnostic connectors for manufacturer-specific purposes (i.e., 

purposes other than the required OBD functions). However, if the additional 

connector conforms to the “Type A” specifications of SAE J1962 (as specified in 

paragraph (k)(1) of this section) or the specifications of SAE J1939-13 (as specified 

in paragraph (k)(1) of this section) and is located in the vehicle interior near the 

required connector as described in this paragraph (k)(2), the connector(s) must be 

labeled clearly to identify which connector is used to access the standardized OBD 

information required by paragraph (k) of this section.

(3) Communications to a scan tool. For model years 2013 and later, all OBD control 

modules (e.g., engine, auxiliary emission control module) on a single vehicle must 

use the same protocol for communication of required emission-related messages from 

on-board to off-board network communications to a scan tool meeting SAE J1978 (as 

specified in paragraph (k)(1) of this section) specifications or designed to 

communicate with an SAE J1939 (as specified in paragraph (k)(1) of this section) 

network. Engine manufacturers shall not alter normal operation of the engine 

emission control system due to the presence of off-board test equipment accessing 

information required by this paragraph (k). The OBD system must use one of the 

following standardized protocols:

(i) ISO 15765-4:2005(E) (as specified in paragraph (k)(1) of this section). All 

required emission-related messages using this protocol must use a 500 kbps baud 

rate.

(ii) SAE J1939 (as specified in paragraph (k)(1) of this section). This protocol may 

only be used on vehicles with diesel engines.

(4) Required emission related functions. The following functions must be 

implemented and must be accessible by, at a minimum, a manufacturer scan tool. For 

model years 2013 and later, the following standardized functions must be

implemented in accordance with the specifications in SAE J1979 (as specified in 

paragraph (k)(1) of this section) or SAE J1939 (as specified in paragraph (k)(1) of 

this section) to allow for access to the required information by a scan tool meeting 

SAE J1978 (as specified in paragraph (k)(1) of this section) specifications or designed 

to communicate with an SAE J1939 (as specified in paragraph (k)(1) of this section) 

network:

(i) Ready status. The OBD system must indicate, in accordance with SAE J1979 or 

SAE J1939-73 (both as specified in paragraph (k)(1) of this section) specifications 

for model years 2013 and later, “complete” or “not complete” for each of the 

installed monitored components and systems identified in paragraphs (g), (h) with 
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the exception of (h)(4), and (i)(3) of this section. All components or systems 

identified in paragraphs (h)(1), (h)(2), or (i)(3) of this section that are monitored 

continuously must always indicate “complete.” Components or systems that are not 

subject to being monitored continuously must immediately indicate “complete”

upon the respective monitor(s) being executed fully and determining that the 

component or system is not malfunctioning. A component or system must also 

indicate “complete” if, after the requisite number of decisions necessary for 

determining MIL status has been executed fully, the monitor indicates a 

malfunction of the component or system. The status for each of the monitored 

components or systems must indicate “not complete” whenever diagnostic memory 

has been cleared or erased by a means other than that allowed in paragraph (b) of 

this section. Normal vehicle shut down (i.e., key-off/engine-off) shall not cause the 

status to indicate “not complete.”

(A) The manufacturer may request that the ready status for a monitor be set to 

indicate “complete” without the monitor having completed if monitoring is 

disabled for a multiple number of drive cycles due to the continued presence of 

extreme operating conditions (e.g., cold ambient temperatures, high altitudes). 

Any such request must specify the conditions for monitoring system disablement 

and the number of drive cycles that would pass without monitor completion 

before ready status would be indicated as “complete.”

(B) For the evaporative system monitor, the ready status must be set in 

accordance with this paragraph (k)(4)(i) when both the functional check of the 

purge valve and, if applicable, the leak detection monitor of the hole size 

specified in paragraph (h)(7)(ii)(B) of this section indicate that they are complete.

(C) If the manufacturer elects to indicate ready status through the MIL in the keyon/engine-off position as provided for in paragraph (b)(1)(iii) of this section, the 

ready status must be indicated in the following manner: If the ready status for all 

monitored components or systems is “complete,” the MIL shall remain 

continuously activated in the key-on/engine-off position for at least 10-20 

seconds. If the ready status for one or more of the monitored components or 

systems is “not complete,” after at least 5 seconds of operation in the keyon/engine-off position with the MIL activated continuously, the MIL shall blink 

once per second for 5-10 seconds. The data stream value for MIL status as 

required in paragraph (k)(4)(ii) of this section must indicate “commanded off”

during this sequence unless the MIL has also been “commanded on” for a 

detected malfunction.

(ii) Data stream. For model years 2010 through 2012, the following signals must be 

made available on demand through the data link connector. For model years 2013 

and later, the following signals must be made available on demand through the 

standardized data link connector in accordance with SAE J1979 or SAE J1939 

(both as specified in paragraph (k)(1) of this section) specifications. The actual 

signal value must always be used instead of a limp home value. Data link signals 

may report an error state or other predefined status indicator if they are defined for 
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those signals in the SAE J1979 or SAE J1939 (both as specified in paragraph (k)(1) 

of this section) specifications.

(A) For gasoline engines.

1. Calculated load value, engine coolant temperature, engine speed, vehicle 

speed, and time elapsed since engine start.

2. Absolute load, fuel level (if used to enable or disable any other monitors), 

barometric pressure (directly measured or estimated), engine control module 

system voltage, and commanded equivalence ratio.

3. Number of stored MIL-on DTCs, catalyst temperature (if directly measured 

or estimated for purposes of enabling the catalyst monitor(s)), monitor status 

(i.e., disabled for the rest of this drive cycle, complete this drive cycle, or not 

complete this drive cycle) since last engine shut-off for each monitor used for 

ready status, distance traveled (or engine run time for engines not using 

vehicle speed information) while MIL activated, distance traveled (or engine 

run time for engines not using vehicle speed information) since DTC memory 

last erased, and number of warm-up cycles since DTC memory last erased, 

OBD requirements to which the engine is certified (e.g., California OBD, 

EPA OBD, European OBD, non-OBD) and MIL status (i.e., commanded-on 

or commanded-off).

(B) For diesel engines.

1. Calculated load (engine torque as a percentage of maximum torque 

available at the current engine speed), driver’s demand engine torque (as a 

percentage of maximum engine torque), actual engine torque (as a percentage 

of maximum engine torque), reference engine maximum torque, reference 

maximum engine torque as a function of engine speed (suspect parameter 

numbers (SPN) 539 through 543 defined by SAE J1939 (as specified in 

paragraph (k)(1) of this section) within parameter group number (PGN) 65251 

for engine configuration), engine coolant temperature, engine oil temperature 

(if used for emission control or any OBD monitors), engine speed, and time 

elapsed since engine start.

2. Fuel level (if used to enable or disable any other monitors), vehicle speed 

(if used for emission control or any OBD monitors), barometric pressure 

(directly measured or estimated), and engine control module system voltage.

3. Number of stored MIL-on DTCs, monitor status (i.e., disabled for the rest 

of this drive cycle, complete this drive cycle, or not complete this drive cycle) 

since last engine shut-off for each monitor used for ready status, distance 

traveled (or engine run time for engines not using vehicle speed information) 

while MIL activated, distance traveled (or engine run time for engines not 

using vehicle speed information) since DTC memory last erased, number of 
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warm-up cycles since DTC memory last erased, OBD requirements to which 

the engine is certified (e.g., California OBD, EPA OBD, European OBD, nonOBD), and MIL status (i.e., commanded-on or commanded-off).

4. NOx NTE control area status (i.e., inside control area, outside control area, 

inside manufacturer-specific NOx NTE carve-out area, or deficiency active 

area) and PM NTE control area status (i.e., inside control area, outside control 

area, inside manufacturer-specific PM NTE carve-out area, or deficiency 

active area).

5. For purposes of the calculated load and torque parameters in paragraph 

(k)(4)(ii)(B)(1) of this section, manufacturers must report the most accurate 

values that are calculated within the applicable electronic control unit (e.g.,

the engine control module). Most accurate, in this context, must be of 

sufficient accuracy, resolution, and filtering to be used for the purposes of inuse emission testing with the engine still in a vehicle (e.g., using portable 

emission measurement equipment).

(C) For all engines so equipped.

 

1. Absolute throttle position, relative throttle position, fuel control system 

status (e.g., open loop, closed loop), fuel trim, fuel pressure, ignition timing 

advance, fuel injection timing, intake air/manifold temperature, engine 

intercooler temperature, manifold absolute pressure, air flow rate from mass 

air flow sensor, secondary air status (upstream, downstream, or atmosphere), 

ambient air temperature, commanded purge valve duty cycle/position, 

commanded EGR valve duty cycle/position, actual EGR valve duty 

cycle/position, EGR error between actual and commanded, PTO status (active 

or not active), redundant absolute throttle position (for electronic throttle or 

other systems that utilize two or more sensors), absolute pedal position, 

redundant absolute pedal position, commanded throttle motor position, fuel 

rate, boost pressure, commanded/target boost pressure, turbo inlet air 

temperature, fuel rail pressure, commanded fuel rail pressure, DPF inlet 

pressure, DPF inlet temperature, DPF outlet pressure, DPF outlet temperature, 

DPF delta pressure, exhaust pressure sensor output, exhaust gas temperature 

sensor output, injection control pressure, commanded injection control 

pressure, turbocharger/turbine speed, variable geometry turbo position, 

commanded variable geometry turbo position, turbocharger compressor inlet 

temperature, turbocharger compressor inlet pressure, turbocharger turbine 

inlet temperature, turbocharger turbine outlet temperature, waste gate valve 

position, and glow plug lamp status.

2. Oxygen sensor output, air/fuel ratio sensor output, NOx sensor output, and 

evaporative system vapor pressure.

(iii) Freeze frame.
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(A) For model years 2010 through 2012, “Freeze frame” information required to 

be stored pursuant to paragraphs (b)(2)(iv), (h)(1)(iv)(D), and (h)(2)(vi) of this 

section must be made available on demand through the data link connector. For 

model years 2013 and later, “Freeze frame” information required to be stored 

pursuant to paragraphs (b)(2)(iv), (h)(1)(iv)(D), and (h)(2)(vi) of this section must 

be made available on demand through the standardized data link connector in 

accordance with SAE J1979 or SAE J1939-73 (both as specified in paragraph 

(k)(1) of this section) specifications.

(B) “Freeze frame” conditions must include the DTC that caused the data to be 

stored along with all of the signals required in paragraphs (k)(4)(ii)(A)(1) and 

(k)(4)(ii)(B)(1) of this section. Freeze frame conditions must also include all of 

the signals required on the engine in paragraphs (k)(4)(ii)(A)(2) and 

(k)(4)(ii)(B)(2) of this section, and paragraph (k)(4)(ii)(C)(1) of this section that 

are used for diagnostic or control purposes in the specific monitor or emissioncritical powertrain control unit that stored the DTC.

(C) Only one frame of data is required to be recorded. For model years 2010 

through 2012, the manufacturer may choose to store additional frames provided 

that at least the required frame can be read by, at a minimum, a manufacturer scan 

tool. For model years 2013 and later, the manufacturer may choose to store 

additional frames provided that at least the required frame can be read by a scan 

tool meeting SAE J1978 (as specified in paragraph (k)(1) of this section) 

specifications or designed to communicate with an SAE J1939 (as specified in 

paragraph (k)(1) of this section) network.

(iv) Diagnostic trouble codes.

(A) For model years 2010 through 2012, For all monitored components and 

systems, any stored pending, MIL-on, and previous-MIL-on DTCs must be made 

available through the diagnostic connector. For model years 2013 and later, all 

monitored components and systems, any stored pending, MIL-on, and previousMIL-on DTCs must be made available through the diagnostic connector in a 

standardized format in accordance with SAE J1939 (as specified in paragraph 

(k)(1) of this section) or ISO 15765-4:2005(E) (as specified in paragraph (k)(1) of 

this section) specifications; standardized DTCs conforming to the applicable 

standardized specifications must be employed.

(B) The stored DTC must, to the extent possible, pinpoint the probable cause of 

the malfunction or potential malfunction. To the extent feasible, the manufacturer 

must use separate DTCs for every monitor where the monitor and repair 

procedure or probable cause of the malfunction is different. In general, rationality 

and functional checks must use different DTCs than the respective circuit 

integrity checks. Additionally, to the extent possible, input component circuit 

integrity checks must use different DTCs for distinct malfunctions (e.g., out-ofrange low, out-of-range high, open circuit).
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(C) The manufacturer must use appropriate standard-defined DTCs whenever 

possible. With Administrator approval, the manufacturer may use manufacturerdefined DTCs in accordance with the applicable standard’s specifications. To do 

so, the manufacturer must be able to show a lack of available standard-defined 

DTCs, uniqueness of the monitor or monitored component, expected future usage 

of the monitor or component, and estimated usefulness in providing additional 

diagnostic and repair information to service technicians. Manufacturer-defined 

DTCs must be used in a consistent manner (i.e., the same DTC shall not be used 

to represent two different failure modes) across a manufacturer’s entire product 

line.

(D) For model years 2010 through 2012, a pending or MIL-on DTC (as required 

in paragraphs (g) through (i) of this section) must be stored and available to, at a 

minimum, a manufacturer scan tool within 10 seconds after a monitor has 

determined that a malfunction or potential malfunction has occurred. A permanent 

DTC must be stored and available to, at a minimum, a manufacturer scan tool no 

later than the end of an ignition cycle in which the corresponding MIL-on DTC 

that caused MIL activation has been stored. For model years 2013 and later, a 

pending or MIL-on DTC (as required in paragraphs (g) through (i) of this section) 

must be stored and available to an SAE J1978 (as specified in paragraph (k)(1) of 

this section) or SAE J1939 (as specified in paragraph (k)(1) of this section) scan 

tool within 10 seconds after a monitor has determined that a malfunction or 

potential malfunction has occurred. A permanent DTC must be stored and 

available to an SAE J1978 (as specified in paragraph (k)(1) of this section) or 

SAE J1939 (as specified in paragraph (k)(1) of this section) scan tool no later than 

the end of an ignition cycle in which the corresponding MIL-on DTC that caused 

MIL activation has been stored.

(E) For model years 2010 through 2012, pending DTCs for all components and 

systems (including those monitored continuously and non-continuously) must be 

made available through the diagnostic connector. For model years 2013 and later, 

pending DTCs for all components and systems (including those monitored 

continuously and non-continuously) must be made available through the 

diagnostic connector in accordance with the applicable standard’s specifications. 

For all model years, a manufacturer using alternative statistical protocols for MIL 

activation as allowed in paragraph (b)(2)(iii) of this section must submit the 

details of their protocol for setting pending DTCs. The protocol must be, overall, 

equivalent to the requirements of this paragraph (k)(4)(iv)(E) and provide service 

technicians with a quick and accurate indication of a potential malfunction.

(F) For model years 2010 through 2012, permanent DTC for all components and 

systems must be made available through the diagnostic connector in a format that 

distinguishes permanent DTCs from pending DTCs, MIL-on DTCs, and previousMIL-on DTCs. A MIL-on DTC must be stored as a permanent DTC no later than 

the end of the ignition cycle and subsequently at all times that the MIL-on DTC is 

commanding the MIL on. For model years 2013 and later, permanent DTC for all 

components and systems must be made available through the diagnostic connector 
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in a standardized format that distinguishes permanent DTCs from pending DTCs, 

MIL-on DTCs, and previous-MIL-on DTCs. A MIL-on DTC must be stored as a 

permanent DTC no later than the end of the ignition cycle and subsequently at all 

times that the MIL-on DTC is commanding the MIL on. For all model years, 

permanent DTCs must be stored in non-volatile random access memory 

(NVRAM) and shall not be erasable by any scan tool command or by 

disconnecting power to the on-board computer. Permanent DTCs must be 

erasable if the engine control module is reprogrammed and the ready status 

described in paragraph (k)(4)(i) of this section for all monitored components and 

systems are set to “not complete.” The OBD system must have the ability to store 

a minimum of four current MIL-on DTCs as permanent DTCs in NVRAM. If the 

number of MIL-on DTCs currently commanding activation of the MIL exceeds 

the maximum number of permanent DTCs that can be stored, the OBD system 

must store the earliest detected MIL-on DTC as permanent DTC. If additional 

MIL-on DTCs are stored when the maximum number of permanent DTCs is 

already stored in NVRAM, the OBD system shall not replace any existing 

permanent DTC with the additional MIL-on DTCs.

(v) Test results.

(A) For model years 2010 through 2012 and except as provided for in paragraph 

(k)(4)(v)(G) of this section, for all monitored components and systems identified 

in paragraphs (g) and (h) of this section, results of the most recent monitoring of 

the components and systems and the test limits established for monitoring the 

respective components and systems must be stored and available through the data 

link. For model years 2013 and later and except as provided for in paragraph 

(k)(4)(v)(G) of this section, for all monitored components and systems identified 

in paragraphs (g) and (h) of this section, results of the most recent monitoring of 

the components and systems and the test limits established for monitoring the 

respective components and systems must be stored and available through the data 

link in accordance with the standardized format specified in SAE J1979 (as 

specified in paragraph (k)(1) of this section) for engines using the ISO 15765-

4:2005(E) (as specified in paragraph (k)(1) of this section) protocol or SAE J1939 

(as specified in paragraph (k)(1) of this section).

(B) The test results must be reported such that properly functioning components 

and systems (e.g., “passing” systems) do not store test values outside of the 

established test limits. Test limits must include both minimum and maximum 

acceptable values and must be defined so that a test result equal to either test limit 

is a “passing” value, not a “failing” value.

(C) For model years 2013 and later, the test results must be standardized such that 

the name of the monitored component (e.g., catalyst bank 1) can be identified by a 

generic scan tool and the test results and limits can be scaled and reported by a 

generic scan tool with the appropriate engineering units.
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(D) The test results must be stored until updated by a more recent valid test result 

or the DTC memory of the OBD system computer is cleared. Upon DTC memory 

being cleared, test results reported for monitors that have not yet completed with 

valid test results since the last time the fault memory was cleared must report 

values of zero for the test result and test limits.

(E) All test results and test limits must always be reported and the test results 

must be stored until updated by a more recent valid test result or the DTC 

memory of the OBD system computer is cleared.

(F) The OBD system must store and report unique test results for each separate 

monitor.

(G) The requirements of this paragraph (k)(4)(v) do not apply to continuous fuel 

system monitoring, cold start emission reduction strategy monitoring, and 

continuous circuit monitoring.

(vi) Software calibration identification (CAL ID). On all engines, a single software 

calibration identification number (CAL ID) for each monitor or emission critical 

control unit(s) must be made available through, for model years 2010 through 2012, 

the data link connector or, for model years 2013 and later, the standardized data link 

connector in accordance with the SAE J1979 or SAE J1939 (both as specified in 

paragraph (k)(1) of this section) specifications. A unique CAL ID must be used for 

every emission-related calibration and/or software set having at least one bit of 

different data from any other emission-related calibration and/or software set. 

Control units coded with multiple emission or diagnostic calibrations and/or 

software sets must indicate a unique CAL ID for each variant in a manner that 

enables an off-board device to determine which variant is being used by the engine. 

Control units that use a strategy that will result in MIL activation if the incorrect 

variant is used (e.g., control units that contain variants for manual and automatic 

transmissions but will activate the MIL if the selected variant does not match the 

type of transmission mated to the engine) are not required to use unique CAL IDs. 

Manufacturers may request Administrator approval to respond with more than one 

CAL ID per diagnostic or emission critical control unit. Administrator approval of 

the request shall be based on the method used by the manufacturer to ensure each 

control unit will respond to a scan tool with the CAL IDs in order of highest to 

lowest priority with regards to areas of the software most critical to emission and 

OBD system performance.

(vii) Software calibration verification number (CVN).

(A) All engines must use an algorithm to calculate a single calibration verification 

number (CVN) that verifies the on-board computer software integrity for each 

monitor or emission critical control unit that is electronically reprogrammable. 

The CVN must be made available through, for model years 2010 through 2012, 

the data link connector or, for model years 2013 and later, the standardized data 

link connector in accordance with the SAE J1979 or SAE J1939 (both as specified 
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in paragraph (k)(1) of this section) specifications. The CVN must indicate 

whether the emission-related software and/or calibration data are valid and 

applicable for the given vehicle and CAL ID. For systems having more than one 

CAL ID as allowed under paragraph (k)(4)(vi) of this section, one CVN must be 

made available for each CAL ID and must be output to a scan tool in the same 

order as the corresponding CAL IDs. For 2010 through 2012, manufacturers may 

use a default value for the CVN if their emissions critical powertrain control 

modules are not programmable in the field. For all years, manufacturers may use 

a default value for the CVN if their emissions critical powertrain control modules 

are one-time programmable or masked read-only memory. Any default CVN shall 

be 00000000 for systems designed in accordance with the SAE J1979 (as 

specified in paragraph (k)(1) of this section) specifications, and FFFFFFFFh for 

systems designed in accordance with the SAE J1939 (as specified in paragraph 

(k)(1) of this section) specifications.

(B) The CVN algorithm used to calculate the CVN must be of sufficient 

complexity that the same CVN is difficult to achieve with modified calibration 

values.

(C) The CVN must be calculated at least once per ignition cycle and stored until 

the CVN is subsequently updated. Except for immediately after a reprogramming 

event or a non-volatile memory clear or for the first 30 seconds of engine 

operation after a volatile memory clear or battery disconnect, the stored value 

must be made available through, for model years 2010 through 2012, the data link 

connector to, at a minimum, a manufacturer scan tool or, for model years 2013 

and later, the data link connector to a generic scan tool in accordance with SAE 

J1979 or SAE J1939 (both as specified in paragraph (k)(1) of this section) 

specifications. For model years 2010 through 2012, the stored CVN value shall 

not be erased when DTC memory is erased or during normal vehicle shut down 

(i.e., key-off/engine-off). For model years 2013 and later, the stored CVN value 

shall not be erased when DTC memory is erased by a generic scan tool in 

accordance with SAE J1979 or SAE J1939 (both as specified in paragraph (k)(1) 

of this section) specifications or during normal vehicle shut down (i.e., keyoff/engine-off).

(D) For model years 2013 and later, the CVN and CAL ID combination 

information must be available for all engines/vehicles in a standardized electronic 

format that allows for off-board verification that the CVN is valid and appropriate 

for a specific vehicle and CAL ID.

(viii) Vehicle identification number (VIN).

(A) For model years 2010 through 2012, all vehicles must have the vehicle 

identification number (VIN) available through the data link connector to, at a 

minimum, a manufacturer scan tool Only one electronic control unit per vehicle 

may report the VIN to a scan tool. For model years 2013 and later, all vehicles 

must have the vehicle identification number (VIN) available in a standardized 
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format through the standardized data link connector in accordance with SAE 

J1979 or SAE J1939 (both as specified in paragraph (k)(1) of this section) 

specifications. Only one electronic control unit per vehicle may report the VIN to 

an SAE J1978 or SAE J1939 (both as specified in paragraph (k)(1) of this section) 

scan tool.

(B) If the VIN is reprogrammable, all emission-related diagnostic information 

identified in paragraph (k)(4)(ix)(A) of this section must be erased in conjunction 

with reprogramming of the VIN.

(ix) Erasure of diagnostic information.

(A) For purposes of this paragraph (k)(4)(ix), “emission-related diagnostic 

information” includes all of the following: ready status as required by paragraph 

(k)(4)(i) of this section; data stream information as required by paragraph 

(k)(4)(ii) of this section including the number of stored MIL-on DTCs, distance 

traveled while MIL activated, number of warm-up cycles since DTC memory last 

erased, and distance traveled since DTC memory last erased; freeze frame 

information as required by paragraph (k)(4)(iii) of this section; pending, MIL-on, 

and previous-MIL-on DTCs as required by paragraph (k)(4)(iv) of this section; 

and, test results as required by paragraph (k)(4)(v) of this section.

(B) For all engines, the emission-related diagnostic information must be erased if 

commanded by any scan tool and may be erased if the power to the on-board 

computer is disconnected. If any of the emission-related diagnostic information is 

commanded to be erased by any scan tool, all emission-related diagnostic 

information must be erased from all diagnostic or emission critical control units. 

The OBD system shall not allow a scan tool to erase a subset of the emissionrelated diagnostic information (e.g., the OBD system shall not allow a scan tool to 

erase only one of three stored DTCs or only information from one control unit 

without erasing information from the other control unit(s)).

(5) In-use performance ratio tracking requirements.

(i) For each monitor required in paragraphs (g) through (i) of this section to 

separately report an in-use performance ratio, manufacturers must implement 

software algorithms to, for model years 2010 through 2012, report a numerator and 

denominator or, for model years 2013 and later, report a numerator and 

denominator in the standardized format specified in this paragraph (k)(5) in 

accordance with the SAE J1979 or SAE J1939 (both as specified in paragraph 

(k)(1) of this section) specifications.

(ii) For the numerator, denominator, general denominator, and ignition cycle 

counters required by paragraph (e) of this section, the following numerical value 

specifications apply:
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(A) Each number shall have a minimum value of zero and a maximum value of 

65,535 with a resolution of one.

(B) Each number shall be reset to zero only when a non-volatile random access 

memory (NVRAM) reset occurs (e.g., reprogramming event) or, if the numbers 

are stored in keep-alive memory (KAM), when KAM is lost due to an interruption 

in electrical power to the control unit (e.g., battery disconnect). Numbers shall not 

be reset to zero under any other circumstances including when a scan tool 

command to clear DTCs or reset KAM is received.

(C) To avoid overflow problems, if either the numerator or denominator for a 

specific component reaches the maximum value of 65,535 ±2, both numbers shall 

be divided by two before either is incremented again.

(D) To avoid overflow problems, if the ignition cycle counter reaches the 

maximum value of 65,535 ±2, the ignition cycle counter shall rollover and

increment to zero on the next ignition cycle.

(E) To avoid overflow problems, if the general denominator reaches the 

maximum value of 65,535 ±2, the general denominator shall rollover and 

increment to zero on the next drive cycle that meets the general denominator 

definition.

(F) If a vehicle is not equipped with a component (e.g., oxygen sensor bank 2, 

secondary air system), the corresponding numerator and denominator for that 

specific component shall always be reported as zero.

(iii) For the ratio required by paragraph (e) of this section, the following numerical 

value specifications apply:

(A) The ratio shall have a minimum value of zero and a maximum value of 

7.99527 with a resolution of 0.000122.

(B) The ratio for a specific component shall be considered to be zero whenever 

the corresponding numerator is equal to zero and the corresponding denominator 

is not zero.

(C) The ratio for a specific component shall be considered to be the maximum 

value of 7.99527 if the corresponding denominator is zero or if the actual value of 

the numerator divided by the denominator exceeds the maximum value of 

7.99527.

(6) Engine run time tracking requirements.

(i) For all gasoline and diesel engines, the manufacturer must implement software 

algorithms to, for model years 2010 through 2012, track and report individually or, 
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for model years 2013 and later, track and report individually in a standardized 

format the amount of time the engine has been operated in the following conditions:

(A) Total engine run time.

(B) Total idle run time (with “idle” defined as accelerator pedal released by the 

driver, engine speed less than or equal to 200 rpm above normal warmed-up idle 

(as determined in the drive position for vehicles equipped with an automatic 

transmission) or vehicle speed less than or equal to one mile per hour, and power 

take-off not active).

(C) Total run time with power take off active.

(ii) For each counter specified in paragraph (k)(6)(i) of this section, the following 

numerical value specifications apply:

(A) Each number shall be a four-byte value with a minimum value of zero, a 

resolution of one second per bit, and an accuracy of ± ten seconds per drive cycle.

(B) Each number shall be reset to zero only when a non-volatile memory reset 

occurs (e.g., reprogramming event). Numbers shall not be reset to zero under any 

other circumstances including when a scan tool (generic or enhanced) command 

to clear fault codes or reset KAM is received.

(C) To avoid overflow problems, if any of the individual counters reach the 

maximum value, all counters shall be divided by two before any are incremented 

again.

(D) For model years 2010 through 2012, the counters shall be made available to, 

at a minimum, a manufacturer scan tool and may be rescaled when transmitted 

from a resolution of one second per bit to no more than three minutes per bit. For 

model years 2013 and later, the counters shall be made available to a generic scan 

tool in accordance with the SAE J1979 or SAE J1939 (both as specified in 

paragraph (k)(1) of this section) specifications and may be rescaled when 

transmitted, if required by the SAE specifications, from a resolution of one second 

per bit to no more than three minutes per bit.

(7) For 2019 and subsequent model year alternative-fueled engines derived from a 

diesel-cycle engine, a manufacturer may meet the standardization requirements of 

paragraph (k) of this section that are applicable to diesel engines rather than the 

requirements applicable to gasoline engines.

(l) Monitoring system demonstration requirements for certification

(1) General.
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(i) The manufacturer must submit emissions test data from one or more durability 

demonstration test engines (test engines).

(ii) The Administrator may approve other demonstration protocols if the 

manufacturer can provide comparable assurance that the malfunction criteria are 

chosen based on meeting the malfunction criteria requirements and that the 

timeliness of malfunction detection is within the constraints of the applicable 

monitoring requirements.

 

(iii) For flexible fuel engines capable of operating on more than one fuel or fuel 

combinations, the manufacturer must submit a plan for providing emission test data. 

The plan must demonstrate that testing will represent properly the expected in-use 

fuel or fuel combinations.

(2) Selection of test engines.

(i) Prior to submitting any applications for certification for a model year, the 

manufacturer must notify the Administrator regarding the planned engine families 

and engine ratings within each family for that model year. The Administrator will 

select the engine family(ies) and the specific engine rating within the engine 

family(ies) that the manufacturer shall use as demonstration test engines. The 

selection of test vehicles for production evaluation testing as specified in paragraph 

(j)(2) of this section may take place during this selection process.

(ii) For model years 2010 through 2012. The manufacturer must provide emissions 

test data from the OBD parent rating as defined in paragraph (o)(1) of this section.

(iii) For model years 2013 and later.

(A) A manufacturer certifying one to five engine families in a given model year 

must provide emissions test data for a single test engine from one engine rating. A 

manufacturer certifying six to ten engine families in a given model year must 

provide emissions test data for a single test engine from two different engine 

ratings. A manufacturer certifying eleven or more engine families in a given 

model year must provide emissions test data for a single test engine from three 

different engine ratings. A manufacturer may forego submittal of test data for one 

or more of these test engines if data have been submitted previously for all of the 

engine ratings and/or if all requirements for certification carry-over from one 

model year to the next are satisfied.

(B) For a given model year, a manufacturer may elect to provide emissions data 

for test engines from more engine ratings than required by paragraph (l)(2)(iii)(A) 

of this section. For each additional engine rating tested in that given model year, 

the number of engine ratings required for testing in one future model year will be 

reduced by one.
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(iv) For the test engine, the manufacturer must use an engine (excluding 

aftertreatment devices) aged for a minimum of 125 hours fitted with exhaust 

aftertreatment emission controls aged to be representative of useful life aging. In the 

event that an accelerated aging procedure is used, the manufacturer is required to 

submit a description of the accelerated aging process and/or supporting data or use 

the accelerated aging procedure used for emission certification deterioration factor 

generation. The process and/or data must demonstrate that deterioration of the 

exhaust aftertreatment emission controls is stabilized sufficiently such that it 

represents emission control performance at the end of the useful life.

(3) Required testing. Except as otherwise described in this paragraph (l)(3), the 

manufacturer must perform single malfunction testing based on the applicable test 

with the components/systems set at their malfunction criteria limits as determined by 

the manufacturer for meeting the emissions thresholds required in paragraphs (g), (h), 

and (i) of this section.

(i) Required testing for diesel-fueled/compression ignition engines

(A) Fuel system. The manufacturer must perform a separate test for each 

malfunction limit established by the manufacturer for the fuel system parameters 

(e.g., fuel pressure, injection timing) specified in paragraphs (g)(1)(ii)(A) through 

(g)(1)(ii)(C) and/or (g)(1)(ii)(D) of this section, if applicable, of this section. 

When performing a test for a specific parameter, the fuel system must be 

operating at the malfunction criteria limit for the applicable parameter only. All 

other parameters must be operating with normal characteristics. In conducting the 

fuel system demonstration tests, the manufacturer may use computer 

modifications to cause the fuel system to operate at the malfunction limit if the 

manufacturer can demonstrate that the computer modifications produce test 

results equivalent to an induced hardware malfunction.

(B) Engine misfire. For model years 2013 and later, the manufacturer must 

perform a test at the malfunction limit established by the manufacturer for the 

monitoring required by paragraph (g)(2)(ii)(B) of this section.

(C) EGR system. The manufacturer must perform a separate test for each 

malfunction limit established by the manufacturer for the EGR system parameters 

(e.g., low flow, high flow, slow response) specified in paragraphs (g)(3)(ii)(A) 

through (g)(3)(ii)(C) and in (g)(3)(ii)(E) of this section. In conducting the EGR 

system slow response demonstration tests, the manufacturer may use computer 

modifications to cause the EGR system to operate at the malfunction limit if the 

manufacturer can demonstrate that the computer modifications produce test 

results equivalent to an induced hardware malfunction.

(D) Turbo boost control system. The manufacturer must perform a separate test 

for each malfunction limit established by the manufacturer for the turbo boost 

control system parameters (e.g., underboost, overboost, response) specified in 

paragraphs (g)(4)(ii)(A) through (g)(4)(ii)(C) and in (g)(4)(ii)(E) of this section.
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(E) NMHC catalyst. The manufacturer must perform a separate test for each 

monitored NMHC catalyst(s). The catalyst(s) being evaluated must be 

deteriorated to the applicable malfunction limit established by the manufacturer 

for the monitoring required by paragraph (g)(5)(ii)(A) of this section and using 

methods established by the manufacturer in accordance with paragraph (l)(7) of 

this section. For each monitored NMHC catalyst(s), the manufacturer must also 

demonstrate that the OBD system will detect a catalyst malfunction with the 

catalyst at its maximum level of deterioration (i.e., the substrate(s) completely 

removed from the catalyst container or “empty” can). Emissions data are not 

required for the empty can demonstration.

(F) NOx catalyst. The manufacturer must perform a separate test for each 

monitored NOx catalyst(s) (e.g., SCR catalyst). The catalyst(s) being evaluated 

must be deteriorated to the applicable malfunction criteria established by the 

manufacturer for the monitoring required by paragraphs (g)(6)(ii)(A) and 

(g)(6)(ii)(B) of this section and using methods established by the manufacturer in 

accordance with paragraph (l)(7) of this section. For each monitored NOx

catalyst(s), the manufacturer must also demonstrate that the OBD system will 

detect a catalyst malfunction with the catalyst at its maximum level of 

deterioration (i.e., the substrate(s) completely removed from the catalyst container 

or “empty” can). Emissions data are not required for the empty can 

demonstration.

(G) NOx adsorber. The manufacturer must perform a test using a NOx adsorber(s) 

deteriorated to the applicable malfunction limit established by the manufacturer 

for the monitoring required by paragraph (g)(7)(ii)(A) of this section. The 

manufacturer must also demonstrate that the OBD system will detect a NOx

adsorber malfunction with the NOx adsorber at its maximum level of 

deterioration (i.e., the substrate(s) completely removed from the container or 

“empty” can). Emissions data are not required for the empty can demonstration.

(H) Diesel particulate filter. The manufacturer must perform a separate test using 

a DPF deteriorated to the applicable malfunction limits established by the 

manufacturer for the monitoring required by paragraph (g)(8)(ii)(A) and 

(g)(8)(ii)(B) of this section. For systems using the optional DPF monitoring 

provision of paragraph (g)(8)(ii)(A) of this section, the manufacturer must 

perform a separate test using a DPF modified in a manner approved by the 

Administrator (e.g., drilling of wallflow channel end plugs, drilling of through 

holes, etc.) and testing at each of the nine test points specified in paragraph 

(g)(8)(ii)(A) of this section. The manufacturer must also demonstrate that the 

OBD system will detect a DPF malfunction with the DPF at its maximum level of 

deterioration (i.e., the filter(s) completely removed from the filter container or 

“empty” can). Emissions data are not required for the empty can demonstration.

(I) Exhaust gas sensor. The manufacturer must perform a separate test for each 

malfunction limit established by the manufacturer for the monitoring required in 
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paragraphs (g)(9)(ii)(A), (g)(9)(iii)(A), and (g)(9)(iv)(A) of this section. When 

performing a test, all exhaust gas sensors used for the same purpose (e.g., for the 

same feedback control loop, for the same control feature on parallel exhaust 

banks) must be operating at the malfunction criteria limit for the applicable 

parameter only. All other exhaust gas sensor parameters must be operating with 

normal characteristics.

(J) VVT system. The manufacturer must perform a separate test for each 

malfunction limit established by the manufacturer for the monitoring required in 

paragraphs (g)(10)(ii)(A) and (g)(10)(ii)(B) of this section. In conducting the 

VVT system demonstration tests, the manufacturer may use computer 

modifications to cause the VVT system to operate at the malfunction limit if the 

manufacturer can demonstrate that the computer modifications produce test 

results equivalent to an induced hardware malfunction.

(K) For each of the testing requirements of this paragraph (l)(3)(i) of this section, 

if the manufacturer has established that only a functional check is required 

because no failure or deterioration of the specific tested system could result in an 

engine’s emissions exceeding the applicable emissions thresholds, the 

manufacturer is not required to perform a demonstration test; however, the 

manufacturer is required to provide the data and/or engineering analysis used to 

determine that only a functional test of the system(s) is required.

(ii) Required testing for gasoline-fueled/spark-ignition engines

(A) Fuel system. For engines with adaptive feedback based on the primary fuel 

control sensor(s), the manufacturer must perform a test with the adaptive feedback 

based on the primary fuel control sensor(s) at the rich limit(s) and a test at the lean 

limit(s) established by the manufacturer as required by paragraph (h)(1)(ii)(A) of 

this section to detect a malfunction before emissions exceed applicable emissions 

thresholds. For engines with feedback based on a secondary fuel control sensor(s) 

and subject to the malfunction criteria in paragraph (h)(1)(ii)(A) of this section, 

the manufacturer must perform a test with the feedback based on the secondary 

fuel control sensor(s) at the rich limit(s) and a test at the lean limit(s) established

by the manufacturer as required by paragraph (h)(1)(ii)(A) of this section to detect 

a malfunction before emissions exceed the applicable emissions thresholds. For 

other fuel metering or control systems, the manufacturer must perform a test at the 

criteria limit(s). For purposes of fuel system testing as required by this paragraph 

(l)(3)(ii)(A), the malfunction(s) induced may result in a uniform distribution of 

fuel and air among the cylinders. Non uniform distribution of fuel and air used to 

induce a malfunction shall not cause misfire. In conducting the fuel system 

demonstration tests, the manufacturer may use computer modifications to cause 

the fuel system to operate at the malfunction limit. To do so, the manufacturer 

must be able to demonstrate that the computer modifications produce test results 

equivalent to an induced hardware malfunction.
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(B) Misfire. The manufacturer must perform a test at the malfunction criteria limit 

specified in paragraph (h)(2)(ii)(B) of this section.

(C) EGR system. The manufacturer must perform a test at each flow limit 

calibrated to the malfunction criteria specified in paragraphs (h)(3)(ii)(A) and 

(h)(3)(ii)(B) of this section.

(D) Cold start emission reduction strategy. The manufacturer must perform a test 

at the malfunction criteria for each component monitored according to paragraph 

(h)(4)(ii)(A) of this section.

(E) Secondary air system. The manufacturer must perform a test at each flow limit 

calibrated to the malfunction criteria specified in paragraphs (h)(5)(ii)(A) and 

(h)(5)(ii)(B) of this section.

(F) Catalyst. The manufacturer must perform a test using a catalyst system 

deteriorated to the malfunction criteria specified in paragraph (h)(6)(ii) of this 

section using methods established by the manufacturer in accordance with 

paragraph (l)(7)(ii) of this section. The manufacturer must also demonstrate that 

the OBD system will detect a catalyst system malfunction with the catalyst system 

at its maximum level of deterioration (i.e., the substrate(s) completely removed 

from the catalyst container or “empty” can). Emission data are not required for the 

empty can demonstration.

(G) Exhaust gas sensor. The manufacturer must perform a test with all primary 

exhaust gas sensors used for fuel control simultaneously possessing a response 

rate deteriorated to the malfunction criteria limit specified in paragraph 

(h)(8)(ii)(A) of this section. The manufacturer must also perform a test for any 

other primary or secondary exhaust gas sensor parameter under parargraphs 

(h)(8)(ii)(A) and (h)(8)(iii)(A) of this section that can cause engine emissions to 

exceed the applicable emissions thresholds (e.g., shift in air/fuel ratio at which 

oxygen sensor switches, decreased amplitude). When performing additional 

test(s), all primary and secondary (if applicable) exhaust gas sensors used for 

emission control must be operating at the malfunction criteria limit for the 

applicable parameter only. All other primary and secondary exhaust gas sensor 

parameters must be operating with normal characteristics.

(H) VVT system. The manufacturer must perform a test at each target error limit 

and slow response limit calibrated to the malfunction criteria specified in 

paragraphs (h)(9)(ii)(A) and (h)(9)(ii)(B) of this section. In conducting the VVT 

system demonstration tests, the manufacturer may use computer modifications to 

cause the VVT system to operate at the malfunction limit. To do so, the 

manufacturer must be able to demonstrate that the computer modifications 

produce test results equivalent to an induced hardware malfunction.

(I) For each of the testing requirements of this paragraph (l)(3)(ii), if the 

manufacturer has established that only a functional check is required because no 
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failure or deterioration of the specific tested system could cause an engine’s 

emissions to exceed the applicable emissions thresholds, the manufacturer is not 

required to perform a demonstration test; however the manufacturer is required to 

provide the data and/or engineering analyses used to determine that only a 

functional test of the system(s) is required.

(iii) Required testing for all engines.

(A) Other emission control systems. The manufacturer must conduct 

demonstration tests for all other emission control components (e.g., hydrocarbon 

traps, adsorbers) designed and calibrated to a malfunction limit based on an 

emissions threshold based on the requirements of paragraph (i)(4) of this section.

(B) For each of the testing requirements of paragraph (l)(3)(iii)(A) of this section, 

if the manufacturer has established that only a functional check is required 

because no failure or deterioration of the specific tested system could result in an 

engine’s emissions exceeding the applicable emissions thresholds, the 

manufacturer is not required to perform a demonstration test; however, the 

manufacturer is required to provide the data and/or engineering analysis used to 

determine that only a functional test of the system(s) is required.

(iv) The manufacturer may electronically simulate deteriorated components but 

shall not make any engine control unit modifications when performing 

demonstration tests unless approved by the Administrator. All equipment necessary 

to duplicate the demonstration test must be made available to the Administrator 

upon request.

(4) Testing protocol

(i) Preconditioning. The manufacturer must use an applicable cycle for 

preconditioning test engines prior to conducting each of the emission tests required 

by paragraph (l)(3) of this section. The manufacturer may perform a single 

additional preconditioning cycle, identical to the initial one, after a 20-minute hot 

soak but must demonstrate that such an additional cycle is necessary to stabilize the 

emissions control system. A practice of requiring a cold soak prior to conducting 

preconditioning cycles is not permitted.

(ii) Test sequence.

(A) The manufacturer must set individually each system or component on the test 

engine at the malfunction criteria limit prior to conducting the applicable 

preconditioning cycle(s). If a second preconditioning cycle is permitted in 

accordance with paragraph (l)(4)(i) of this section, the manufacturer may adjust 

the system or component to be tested before conducting the second 

preconditioning cycle. The manufacturer shall not replace, modify, or adjust the 

system or component after the last preconditioning cycle has been completed.
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(B) After preconditioning, the test engine must be operated over the applicable 

cycle to allow for the initial detection of the tested system or component 

malfunction. This test cycle may be omitted from the testing protocol if it is 

unnecessary. If required by the monitoring strategy being tested, a cold soak may 

be performed prior to conducting this test cycle.

(C) The test engine must then be operated over the applicable exhaust emissions 

test.

(iii) A manufacturer required to test more than one test engine according to 

paragraph (l)(2)(iii) of this section may use internal calibration sign-off test 

procedures (e.g., forced cool downs, less frequently calibrated emission analyzers) 

instead of official test procedures to obtain the emission test data required by this 

paragraph (l) of this section for all but one of the required test engines. The 

manufacturer may elect this option if the data from the alternative test procedure are 

representative of official emissions test results. A manufacturer using this option is 

still responsible for meeting the malfunction criteria specified in paragraphs (g) 

through (i) of this section if and when emissions tests are performed in accordance 

with official test procedures.

(iv) The manufacturer may request approval to use an alternative testing protocol 

for demonstration of MIL activation if the engine dynamometer emission test cycle 

does not allow all of a given monitor’s enable conditions to be satisfied. The

manufacturer may request the use of an alternative engine dynamometer test cycle 

or the use of chassis testing to demonstrate proper MIL activation. To do so, the 

manufacturer must demonstrate the technical necessity for using an alternative test 

cycle and the degree to which the alternative test cycle demonstrates that in-use 

operation with the malfunctioning component will result in proper MIL activation.

(5) Evaluation protocol. Full OBD engine ratings, as defined by paragraph (o)(1) of 

this section, shall be evaluated according to the following protocol:

(i) For all tests conducted as required by paragraph (l) of this section, the MIL must 

activate before the end of the first engine start portion of the applicable test.

(ii) If the MIL activates prior to emissions exceeding the applicable malfunction 

criteria limits specified in paragraphs (g) through (i), no further demonstration is 

required. With respect to the misfire monitor demonstration test, if the manufacturer 

has elected to use the minimum misfire malfunction criteria of one percent as 

allowed in paragraphs (g)(2)(ii)(B), if applicable, and (h)(2)(ii)(B) of this section, 

no further demonstration is required provided the MIL activates with engine misfire 

occurring at the malfunction criteria limit.

(iii) If the MIL does not activate when the system or component is set at its 

malfunction criteria limit(s), the criteria limit(s) or the OBD system is not 

acceptable.
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(A) Except for testing of the catalyst or DPF system, if the MIL first activates 

after emissions exceed the applicable malfunction criteria specified in paragraphs 

(g) through (i) of this section, the test engine shall be retested with the tested 

system or component adjusted so that the MIL will activate before emissions 

exceed the applicable malfunction criteria specified in paragraphs (g) through (i) 

of this section. If the component cannot be so adjusted because an alternative fuel 

or emission control strategy is used when a malfunction is detected (e.g., open 

loop fuel control used after an oxygen sensor malfunction is detected), the test 

engine shall be retested with the component adjusted to the worst acceptable limit 

(i.e., the applicable OBD monitor indicates that the component is performing at or 

slightly better than the malfunction criteria limit). When tested with the 

component so adjusted, the MIL must not activate during the test and the engine 

emissions must be below the applicable malfunction criteria specified in 

paragraphs (g) through (i) of this section.

 

(B) In testing the catalyst or DPF system, if the MIL first activates after emissions 

exceed the applicable emissions threshold(s) specified in paragraphs (g) and (h), 

the tested engine shall be retested with a less deteriorated catalyst or DPF system 

(i.e., more of the applicable engine out pollutants are converted or trapped). For 

the OBD system to be approved, testing shall be continued until the MIL activates 

with emissions below the applicable thresholds of paragraphs (g) and (h) of this 

section, or the MIL activates with emissions within a range no more than 20 

percent below the applicable emissions thresholds and 10 percent or less above 

those emissions thresholds.

(iv) If an OBD system is determined to be unacceptable by the criteria of this 

paragraph (l)(5) of this section, the manufacturer may recalibrate and retest the 

system on the same test engine. In such a case, the manufacturer must confirm, by 

retesting, that all systems and components that were tested prior to the recalibration 

and are affected by it still function properly with the recalibrated OBD system.

(6) Confirmatory testing.

(i) The Administrator may perform confirmatory testing to verify the emission test 

data submitted by the manufacturer as required by this paragraph (l) of this section 

comply with its requirements and the malfunction criteria set forth in paragraphs (g) 

through (i) of this section. Such confirmatory testing is limited to the test engine(s) 

required by paragraph (l)(2) of this section.

(ii) To conduct this confirmatory testing, the Administrator may install 

appropriately deteriorated or malfunctioning components (or simulate them) in an 

otherwise properly functioning test engine of an engine rating represented by the 

demonstration test engine in order to test any of the components or systems required 

to be tested by paragraph (l) of this section. The manufacturer shall make available, 

if requested, an engine and all test equipment (e.g., malfunction simulators, 

deteriorated components) necessary to duplicate the manufacturer’s testing. Such a 

request from the Administrator shall occur within six months of reviewing and 
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approving the demonstration test engine data submitted by the manufacturer for the 

specific engine rating.

(7) Catalyst aging

(i) Diesel catalysts. For purposes of determining the catalyst malfunction limits for 

the monitoring required by paragraphs (g)(5)(ii)(A), (g)(5)(ii)(B), and (g)(6)(ii)(A) 

of this section, where those catalysts are monitored individually, the manufacturer 

must use a catalyst deteriorated to the malfunction criteria using methods 

established by the manufacturer to represent real world catalyst deterioration under 

normal and malfunctioning engine operating conditions. For purposes of 

determining the catalyst malfunction limits for the monitoring required by 

paragraphs (g)(5)(ii)(A), (g)(5)(ii)(B), and (g)(6)(ii)(A) of this section, where those 

catalysts are monitored in combination with other catalysts, the manufacturer must 

submit their catalyst system aging and monitoring plan to the Administrator as part 

of their certification documentation package. The plan must include the description, 

emission control purpose, and location of each component, the monitoring strategy 

for each component and/or combination of components, and the method for

determining the applicable malfunction criteria including the deterioration/aging 

process.

(ii) Gasoline catalysts. For the purposes of determining the catalyst system 

malfunction criteria in paragraph (h)(6)(ii) of this section, the manufacturer must 

use a catalyst system deteriorated to the malfunction criteria using methods 

established by the manufacturer to represent real world catalyst deterioration under 

normal and malfunctioning operating conditions. The malfunction criteria must be 

established by using a catalyst system with all monitored and unmonitored 

(downstream of the sensor utilized for catalyst monitoring) catalysts simultaneously 

deteriorated to the malfunction criteria except for those engines that use fuel shutoff 

to prevent over-fueling during engine misfire conditions. For such engines, the 

malfunction criteria must be established by using a catalyst system with all 

monitored catalysts simultaneously deteriorated to the malfunction criteria while 

unmonitored catalysts shall be deteriorated to the end of the engine’s useful life.

(m) Certification documentation requirements.

(1) When submitting an application for certification of an engine, the manufacturer 

must submit the following documentation. If any of the items listed here are 

standardized for all of the manufacturer’s engines, the manufacturer may, for each 

model year, submit one set of documents covering the standardized items for all of its 

engines.

(i) For the required documentation that is not standardized across all engines, the 

manufacturer may be allowed to submit documentation for certification from one 

engine that is representative of other engines. All such engines shall be considered 

to be part of an OBD certification documentation group. To represent the OBD 

group, the chosen engine must be certified to the most stringent emissions standards 
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and OBD monitoring requirements and cover all of the emissions control devices 

for the engines in the group and covered by the submitted documentation. Such 

OBD groups must be approved in advance of certification.

(ii) Upon approval, one or more of the documentation requirements of this 

paragraph (m) of this section may be waived or modified if the information required 

is redundant or unnecessarily burdensome to generate.

(iii) To the extent possible, the certification documentation must use SAE J1930 (as 

specified in paragraph (k)(1) of this section) or SAE J2403 (as specified in 

paragraph (k)(1) of this section) terms, abbreviations, and acronyms as specified in 

paragraph (k)(1) of this section.

(2) Unless otherwise specified, the following information must be submitted as part 

of the certification application and prior to receiving a certificate.

(i) A description of the functional operation of the OBD system including a 

complete written description for each monitoring strategy that outlines every step in 

the decision-making process of the monitor. Algorithms, diagrams, samples of data, 

and/or other graphical representations of the monitoring strategy shall be included 

where necessary to adequately describe the information.

(ii) A table including the following information for each monitored component or 

system (either computer-sensed or computer-controlled) of the emissions control 

system:

(A) Corresponding diagnostic trouble code.

(B) Monitoring method or procedure for malfunction detection.

(C) Primary malfunction detection parameter and its type of output signal.

(D) Malfunction criteria limits used to evaluate output signal of primary 

parameter.

(E) Other monitored secondary parameters and conditions (in engineering units) 

necessary for malfunction detection.

(F) Monitoring time length and frequency of monitoring events.

(G) Criteria for storing a diagnostic trouble code.

(H) Criteria for activating a malfunction indicator light.

(I) Criteria used for determining out-of-range values and input component 

rationality checks.
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(iii) Whenever possible, the table required by paragraph (m)(2)(ii) of this section 

shall use the following engineering units:

(A) Degrees Celsius for all temperature criteria.

(B) KiloPascals (KPa) for all pressure criteria related to manifold or atmospheric 

pressure.

(C) Grams (g) for all intake air mass criteria.

(D) Pascals (Pa) for all pressure criteria related to evaporative system vapor 

pressure.

(E) Miles per hour (mph) for all vehicle speed criteria.

(F) Relative percent (%) for all relative throttle position criteria (as defined in 

SAE J1979 or SAE J1939 (both as specified in paragraph (k)(1) of this section)).

(G) Voltage (V) for all absolute throttle position criteria (as defined in SAE J1979 

or SAE J1939 (both as specified in paragraph (k)(1) of this section)).

(H) Per crankshaft revolution (/rev) for all changes per ignition event based 

criteria (e.g., g/rev instead of g/stroke or g/firing).

 

(I) Per second (/sec) for all changes per time based criteria (e.g., g/sec).

(J) Percent of nominal tank volume (%) for all fuel tank level criteria.

(iv) A logic flowchart describing the step-by-step evaluation of the enable criteria 

and malfunction criteria for each monitored emission related component or system.

(v) Emissions test data, a description of the testing sequence (e.g., the number and 

types of preconditioning cycles), approximate time (in seconds) of MIL activation 

during the test, diagnostic trouble code(s) and freeze frame information stored at the 

time of detection, corresponding test results (e.g. SAE J1979 (as specified in 

paragraph (k)(1) of this section) Mode/Service $06, SAE J1939 (as specified in 

paragraph (k)(1) of this section) Diagnostic Message 8 (DM8)) stored during the 

test, and a description of the modified or deteriorated components used for 

malfunction simulation with respect to the demonstration tests specified in 

paragraph (l) of this section. The freeze frame data are not required for engines 

termed “Extrapolated OBD” engines.

(vi) For gasoline engines, data supporting the misfire monitor, including:

(A) The established percentage of misfire that can be tolerated without damaging 

the catalyst over the full range of engine speed and load conditions.
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(B) Data demonstrating the probability of detection of misfire events by the 

misfire monitoring system over the full engine speed and load operating range for 

the following misfire patterns: random cylinders misfiring at the malfunction 

criteria established in paragraph (h)(2)(ii)(B) of this section, one cylinder 

continuously misfiring, and paired cylinders continuously misfiring.

(C) Data identifying all disablement of misfire monitoring that occurs during the 

FTP. For every disablement that occurs during the cycles, the data shall identify: 

when the disablement occurred relative to the driver’s trace, the number of engine 

revolutions during which each disablement was present, and which disable 

condition documented in the certification application caused the disablement.

(D) Manufacturers are not required to use the durability demonstration engine to 

collect the misfire data required by paragraph (m)(2)(vi) of this section.

(vii) Data supporting the limit for the time between engine starting and attaining the 

designated heating temperature for after-start heated catalyst systems.

(viii) Data supporting the criteria used to detect a malfunction of the fuel system, 

EGR system, boost pressure control system, catalyst, NOx adsorber, DPF, cold start 

emission reduction strategy, secondary air, evaporative system, VVT system, 

exhaust gas sensors, and other emission controls that causes emissions to exceed the 

applicable malfunction criteria specified in paragraphs (g) through (i) of this 

section. For diesel engine monitors required by paragraphs (g) and (i) of this section 

that are required to indicate a malfunction before emissions exceed an emission 

threshold based on any applicable standard (e.g., 2.5 times any of the applicable 

standards), the test cycle and standard determined by the manufacturer to be the 

most stringent for each applicable monitor in accordance with paragraph (f)(1) of 

this section.

(ix) A list of all electronic powertrain input and output signals (including those not 

monitored by the OBD system) that identifies which signals are monitored by the 

OBD system. For input and output signals that are monitored as comprehensive 

components, the listing shall also identify the specific diagnostic trouble code for 

each malfunction criteria (e.g., out-of-range low, out-of-range high, open circuit, 

rationality low, rationality high).

(x) A written description of all parameters and conditions necessary to begin 

closed-loop/feedback control of emission control systems (e.g., fuel system, boost 

pressure, EGR flow, SCR reductant delivery, DPF regeneration, fuel system 

pressure).

(xi) A written identification of the communication protocol utilized by each engine 

for communication with a scan tool (model years 2010 through 2012) or an SAE 

J1978 or SAE J1939 (both as specified in paragraph (k)(1) of this section) scan tool 

(model years 2013 and later).
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(xii) For model years 2013 and later, a pictorial representation or written description 

of the diagnostic connector location including any covers or labels.

(xiii) A written description of the method used by the manufacturer to meet the 

requirements of paragraph (i)(2) of this section (crankcase ventilation system 

monitoring) including diagrams or pictures of valve and/or hose connections.

(xiv) Build specifications provided to engine purchasers or chassis manufacturers 

detailing all specifications or limitations imposed on the engine purchaser relevant 

to OBD requirements or emissions compliance (e.g., cooling system heat rejection 

rates, allowable MIL locations, connector location specifications). A description of 

the method or copies of agreements used to ensure engine purchasers or chassis 

manufacturers will comply with the OBD and emissions relevant build 

specifications (e.g., signed agreements, required audit/evaluation procedures).

(xv) Any other information determined by the Administrator to be necessary to 

demonstrate compliance with the requirements of this section.

(3) In addition to the documentation required by paragraphs (m)(1) and (m)(2) of this 

section, a manufacturer making use of paragraph (a)(5) of this section must submit 

the following information with their application for certification.

(i) A detailed description of how the OBD system meets the intent of § 86.010-18.

(ii) A detailed description of why the manufacturer has chosen not to design the 

OBD system to meet the requirements of § 86.010-18 and has instead designed the 

OBD system to meet the applicable California OBD requirements.

(iii) A detailed description of any deficiencies granted by the California staff and 

any concerns raised by California staff. A copy of a California Executive Order 

alone will not be considered acceptable toward meeting this requirement. This 

description shall also include, to the extent feasible, a plan with timelines for 

resolving deficiencies and/or concerns.

(n) Deficiencies.

Changes below are intended to align alternative fuel engines requirements 

with those for engines used with hybrid powertrain systems. They also 

allow engine manufacturers to perform a general analysis of monitors 

where reliability may be influenced by hybrid powertrain systems rather 

than requiring analysis to be performed for specific hybrid powertrain 

systems. Finally, they clarify that a waiver of a monitoring requirement is 

not a deficiency. 

(1) Upon application by the manufacturer, the Administrator may accept an OBD 

system as compliant even though specific requirements are not fully met. Such 

compliances without meeting specific requirements, or deficiencies, will be granted 
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only if compliance is infeasible or unreasonable considering such factors as, but not 

limited to: Technical feasibility of the given monitor and lead time and production 

cycles including phase-in or phase-out of engines or vehicle designs and programmed 

upgrades of computers. Unmet requirements shall not be carried over from the 

previous model year except where unreasonable hardware or software modifications 

are necessary to correct the deficiency, and the manufacturer has demonstrated an 

acceptable level of effort toward compliance as determined by the Administrator. 

Furthermore, EPA will not accept any deficiency requests that include the complete 

lack of a major diagnostic monitor (“major” diagnostic monitors being those for 

exhaust aftertreatment devices, oxygen sensor, air-fuel ratio sensor, NOx sensor, 

engine misfire, evaporative leaks, and diesel EGR, if equipped), with the possible 

exception of the special provisions for alternative fueled engines. For alternative 

fueled heavy-duty engines (e.g., natural gas, liquefied petroleum gas, methanol, 

ethanol) and engines used with any hybrid powertrain system as defined in § 86-010-

02, manufacturers may request the Administrator to waive specific monitoring 

requirements of this section for which monitoring may not be reliable with respect to 

the use of the alternative fuel or hybrid powertrain systems. At a minimum, 

alternative fuel engines and engines used with hybrid powertrain systems must be 

equipped with an OBD system meeting OBD requirements to the extent feasible as 

approved by the Administrator. However, with respect to engines used with hybrid 

powertrain systems, the Administrator shall accept a manufacturer’s general 

engineering analysis of monitoring requirements for which monitoring may not be 

reliable and not require separate analyses for different hybrid powertrain systems. A 

waiver of specific monitoring requirements for engines used with hybrid powertrain 

systems does not constitute a deficiency with respect to this section (n).

(2) In the event the manufacturer seeks to carry-over a deficiency from a past model 

year to the current model year, the manufacturer must re-apply for approval to do so. 

In considering the request to carry-over a deficiency, the Administrator shall consider 

the manufacturer’s progress towards correcting the deficiency. The Administrator 

may not allow manufacturers to carry over monitoring system deficiencies for more 

than two model years unless it can be demonstrated that substantial engine hardware 

modifications and additional lead time beyond two years are necessary to correct the 

deficiency.

(3) A deficiency shall not be granted retroactively (i.e., after the engine has been 

certified).

Changes that follow in paragraph (o) are intended to align requirements 

for alternative fueled engines with those that apply to engines used with 

hybrid powertrain systems 

(o) Implementation schedule. Except as specifically provided for in this paragraph (o) 

for small volume manufacturers, and alternative fueled engines, and engines used with 

hybrid powertrain systems, the requirements of this section must be met according to 

the following provisions:
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(1) For model years 2010 through 2012

(i) Full OBD. The manufacturer must implement an OBD system meeting the 

applicable requirements of § 86.010-18 on one engine rating within one engine 

family of the manufacturer’s product line. This “Full OBD” rating will be known as 

the “OBD parent” rating. The OBD parent rating must be chosen, unless otherwise 

approved by the Administrator, as the rating having the highest weighted projected 

U.S. sales within the engine family having the highest weighted projected U.S. 

sales, with U.S. sales being weighted by the useful life of the engine rating.

(ii) Extrapolated OBD. For all other engine ratings within the engine family from 

which the OBD parent rating has been selected, the manufacturer must implement 

an OBD system meeting the applicable requirements of § 86.010-18 except that the 

OBD system is not required to detect a malfunction prior to exceeding the emission 

thresholds shown in Table 1 of paragraph (g) and Table 2 of paragraph (h) of this 

section. These “Extrapolated OBD” engines will be known as the “OBD child”

ratings. On these OBD child ratings, rather than detecting a malfunction prior to 

exceeding the emission thresholds, the manufacturer must submit a plan for 

Administrator review and approval that details the engineering evaluation the 

manufacturer will use to establish the malfunction criteria for the OBD child 

ratings. The plan must demonstrate both the use of good engineering judgment in 

establishing the malfunction criteria, and robust detection of malfunctions, 

including consideration of differences of base engine, calibration, emission control 

components, and emission control strategies.

(iii) Engine families other than those from which the parent and child ratings have 

been selected, are not subject to the requirements of this section.

(iv) Small volume manufacturers, as defined in § 86.094-14(b)(1) and (2) and as 

determined using 2010 model year sales, are exempt from the requirements of this § 

86.010-18, unless model year 2011 or model year 2012 sales exceed 20,000 units.

This change specifically exempts engines used with hybrid powertrain 

systems from compliance with HD OBD requirements through the 2012 

model-year

(v) Engines certified as alternative fueled engines and engines used with hybrid 

powertrain systems are exempt from the requirements of this § 86.010-18.

(2) For model years 2013 through 2015

(i) OBD groups. The manufacturer shall define one or more OBD groups to cover 

all engine ratings in all engine families. The manufacturer must submit a grouping 

plan for Administrator review and approval detailing the OBD groups and the 

engine families and engine ratings within each group for a given model year.
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(ii) Full OBD.

(A) For all model year 2010 through 2012 “Full OBD” and “Extrapolated OBD”

engine ratings, the manufacturer must implement an OBD system meeting the 

applicable requirements of this section.

(B) On one engine rating within each of the manufacturer’s OBD groups, the 

manufacturer must implement an OBD system meeting the applicable 

requirements of this section. These “Full OBD” ratings will be known as the 

“OBD parent” ratings. The OBD parent rating for each OBD group shall be 

chosen, unless otherwise approved by the Administrator, as the rating having the 

highest weighted projected U.S. sales within the OBD group, with U.S. sales 

being weighted by the useful life of the engine rating.

(iii) Extrapolated OBD. For all other engine ratings within each OBD group, the 

manufacturer must implement an OBD system meeting the requirements of this 

section except that the OBD system is not required to detect a malfunction prior to 

exceeding the emission thresholds shown in Table 1 of paragraph (g) and Table 2 of 

paragraph (h) of this section. These extrapolated OBD engines will be know as the 

“OBD child” ratings. On these OBD child ratings, rather than detecting a 

malfunction prior to exceeding the emission thresholds, the manufacturer must 

submit a plan for Administrator review and approval that details the engineering 

evaluation the manufacturer will use to establish the malfunction criteria for the 

OBD child ratings. The plan must demonstrate both the use of good engineering 

judgment in establishing the malfunction criteria, and robust detection of 

malfunctions, including consideration of differences of base engine, calibration, 

emission control components, and emission control strategies.

(iv) Engines certified as alternative fueled engines shall meet, to the extent feasible, 

the requirements specified in paragraph (i)(3) of this § 86.010-18. Additionally, 

such engines and engines used with hybrid powertrain systems shall monitor the 

NOx aftertreatment system on engines so equipped and detect a malfunction if:

(A) The NOx aftertreatment system has no detectable amount of NOx

aftertreatement capability (i.e., NOx catalyst conversion or NOx adsorption).

(B) The NOx aftertreatment substrate is completely destroyed, removed, or 

missing.

(C) The NOx aftertreatment assembly is replaced with a straight pipe.

(3) For model years 2016 through 2018

(i) OBD groups. The manufacturer shall define one or more OBD groups to cover 

all engine ratings in all engine families. The manufacturer must submit a grouping 

plan for Administrator review and approval detailing the OBD groups and the 

engine families and engine ratings within each group for a given model year.
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(ii) Full OBD. The manufacturer must implement an OBD system meeting the 

applicable requirements of this section on all engine ratings in all engine families.

(iii) Engines certified as alternative fueled engines shall meet, to the extent feasible, 

the requirements specified in paragraph (i)(3) of this § 86.010-18. Additionally, 

such engines and engines used with hybrid powertrain systems shall monitor the 

NOx aftertreatment system on engines so equipped and detect a malfunction if:

(A) The NOx aftertreatment system has no detectable amount of NOx

aftertreatement capability (i.e., NOx catalyst conversion or NOx adsorption).

(B) The NOx aftertreatment substrate is completely destroyed, removed, or 

missing.

(C) The NOx aftertreatment assembly is replaced with a straight pipe.

The language below provides for full OBD monitoring on engines used 

with hybrid powertrain systems beginning with the 2020 model-year.

(4) For model years 2019 and later. (i) The manufacturer must implement an OBD 

system meeting the applicable requirements of § 86.010-18 on all engines except 

those used with hybrid powertrain systems which must implement an OBD system 

meeting the applicable requirements of §86.010-18 no later than the 2020 model-year.

Added language in paragraph (p) is intended to provide engine 

manufacturers with protection from OBD non-compliance related to or 

attributable to hybrid powertrain systems through the 2022 modelyear. The three additional years 2020-2022 are provided to allow for 

an opportunity to make refinements to hybrid powertrain system 

integration and diagnostic performance based on in-use experience. 

(p) In-use compliance standards. For monitors required to indicate a malfunction before 

emissions exceed a certain emission threshold (e.g., 2.5 times any of the applicable 

standards):

(1) For model years 2010 through 2012.

(i) On the full OBD rating (i.e., the parent rating) as defined in paragraph (o)(1) of 

this section, separate in-use emissions thresholds shall apply. These thresholds are 

determined by doubling the applicable thresholds as shown in Table 1 of paragraph 

(g) and Table 2 of paragraph (h) of this section. The resultant thresholds apply only 

in-use and do not apply for certification or selective enforcement auditing.
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(ii) The extrapolated OBD ratings (i.e., the child ratings) as defined in paragraph 

(o)(1) of this section shall not be evaluated against emissions levels for purposes of 

OBD compliance in-use.

(iii) Only the test cycle and standard determined and identified by the manufacturer 

at the time of certification in accordance with paragraph (f) of this section as the 

most stringent shall be used for the purpose of determining OBD system 

noncompliance in-use.

(iv) An OBD system shall not be considered noncompliant solely due to a failure or 

deterioration mode of a monitored component or system that could not have been 

reasonably foreseen to occur by the manufacturer or which is related to or 

attributable to use of a certified engine with a hybrid powertrain system.

(2) For model years 2013 through 2015.

(i) On the full OBD ratings as defined in paragraph (o)(2) of this section, separate 

in-use emissions thresholds shall apply. These thresholds are determined by 

doubling the applicable thresholds as shown in Table 1 of paragraph (g) and Table 2 

of paragraph (h) of this section. The resultant thresholds apply only in-use and do 

not apply for certification or selective enforcement auditing.

(ii) The extrapolated OBD ratings as defined in paragraph (o)(2) of this section shall 

not be evaluated against emissions levels for purposes of OBD compliance in-use.

(iii) Only the test cycle and standard determined and identified by the manufacturer 

at the time of certification in accordance with paragraph (f) of this section as the 

most stringent shall be used for the purpose of determining OBD system 

noncompliance in-use.

(iv) For monitors subject to meeting the minimum in-use monitor performance ratio 

of 0.100 in paragraph (d)(1)(ii), the OBD system shall not be considered 

noncompliant unless a representative sample indicates the in-use ratio is below 

0.050.

(v) An OBD system shall not be considered noncompliant solely due to a failure or 

deterioration mode of a monitored component or system that could not have been 

reasonably foreseen to occur by the manufacturer or which is related to or 

attributable to use of a certified engine with a hybrid powertrain system

.

.

(3) For model years 2016 through 2018.

(i) On the engine ratings tested according to (l)(2)(iii) of this section, the 

certification emissions thresholds shall apply in-use.
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(ii) On the manufacturer’s remaining engine ratings, separate in-use emissions 

thresholds shall apply. These thresholds are determined by doubling the applicable 

thresholds as shown in Table 1 of paragraph (g) and Table 2 of paragraph (h) of this 

section. The resultant thresholds apply only in-use and do not apply for certification 

or selective enforcement auditing.

(iii) An OBD system shall not be considered noncompliant solely due to a failure or 

deterioration mode of a monitored component or system that could not have been 

reasonably foreseen to occur by the manufacturer or which is related to or 

attributable to use of a certified engine with a hybrid powertrain system.

(4) For model years 2019 and later.

(i) On all engine ratings, the certification emissions thresholds shall apply in-use.

(ii) An OBD system shall not be considered noncompliant solely due to a failure or 

deterioration mode of a monitored component or system that could not have been 

reasonably foreseen to occur by the manufacturer. Through the 2022 model-year, 

an OBD system will not be considered noncompliant as the result of any failure or 

deterioration mode of a monitored component or system that is related to or 

attributable to a hybrid powertrain system

.

.

[74 FR 8369, Feb. 24, 2009]

 
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§ 86.010-18

On-board Diagnostics for engines used in applications greater than 14,000 pounds 

GVWR.

(a) General. According to the implementation schedule shown in paragraph (o) of this 

section, heavy-duty engines intended for use in a heavy-duty vehicle weighing more 

than 14,000 pounds GVWR must be equipped with an on-board diagnostic (OBD) 

system capable of monitoring all emission-related engine systems or components 

during the life of the engine. The OBD system is required to detect all malfunctions 

specified in paragraphs (g), (h), and (i) of this § 86.010-18 although the OBD system is 

not required to use a unique monitor to detect each of those malfunctions.

(1) When the OBD system detects a malfunction, it must store a pending, a MIL-on, 

or a previous-MIL-on diagnostic trouble code (DTC) in the onboard computer’s 

memory. A malfunction indicator light (MIL) must also be activated as specified in 

paragraph (b) of this section.

(2) Data link connector.

(i) For model years 2010 through 2012, the OBD system must be equipped with a 

data link connector to provide access to the stored DTCs as specified in paragraph 

(k)(2) of this section.

(ii) For model years 2013 and later, the OBD system must be equipped with a 

standardized data link connector to provide access to the stored DTCs as specified 

in paragraph (k)(2) of this section.

(3) The OBD system cannot be programmed or otherwise designed to deactivate 

based on age and/or mileage. This requirement does not alter existing law and 

enforcement practice regarding a manufacturer’s liability for an engine beyond its 

regulatory useful life, except where an engine has been programmed or otherwise 

designed so that an OBD system deactivates based on age and/or mileage of the 

engine.

(4) Drive cycle or driving cycle, in the context of this § 86.010-18, means operation 

that meets any of the conditions of paragraphs (a)(4)(i) through (a)(4)(iv) of this 

section. Further, for OBD monitors that run during engine-off conditions, the period 

of engine-off time following engine shutoff and up to the next engine start may be 

considered part of the drive cycle for the conditions of paragraphs (a)(4)(i) and 

(a)(4)(iv) of this section. For engines/vehicles that employ engine shutoff OBD 

monitoring strategies that do not require the vehicle operator to restart the engine to 

continue vehicle operation (e.g., a hybrid bus with engine shutoff at idle), the 

manufacturer may use an alternative definition for drive cycle (e.g., key-on followed 

by key-off). Any alternative definition must be based on equivalence to engine startup 

and engine shutoff signaling the beginning and ending of a single driving event for a 

conventional vehicle. For engines that are not likely to be routinely operated for long 
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continuous periods of time, a manufacturer may also request approval to use an 

alternative definition for drive cycle (e.g., solely based on engine start and engine 

shutoff without regard to four hours of continuous engine-on time). Administrator 

approval of the alternative definition will be based on manufacturer-submitted data 

and/or information demonstrating the typical usage, operating habits, and/or driving 

patterns of these vehicles.

(i) Begins with engine start and ends with engine shutoff;

(ii) Begins with engine start and ends after four hours of continuous engine-on 

operation;

(iii) Begins at the end of the previous four hours of continuous engine-on operation 

and ends after four hours of continuous engine-on operation; or

(iv) Begins at the end of the previous four hours of continuous engine-on operation 

and ends with engine shutoff.

(5) As an alternative to demonstrating compliance with the provisions of paragraphs 

(b) through (l) of this § 86.010-18, a manufacturer may demonstrate how the OBD 

system they have designed to comply with California OBD requirements for engines 

used in applications greater than 14,000 pounds also complies with the intent of the 

provisions of paragraphs (b) through (l) of this section. To make use of this 

alternative, the manufacturer must demonstrate to the Administrator how the OBD 

system they intend to certify meets the intent behind all of the requirements of this 

section, where applicable (e.g., paragraph (h) of this section would not apply for a 

diesel fueled/CI engine). Furthermore, if making use of this alternative, the 

manufacturer must comply with the specific certification documentation requirements 

of paragraph (m)(3) of this section.

(6) Temporary provisions to address hardship due to unusual circumstances.

(i) After considering the unusual circumstances, the Administrator may permit the 

manufacturer to introduce into U.S. commerce engines that do not comply with this 

§ 86.010-18 for a limited time if all the following conditions apply:

(A) Unusual circumstances that are clearly outside the manufacturer’s control 

prevent compliance with the requirements of this § 86.010-18.

(B) The manufacturer exercised prudent planning and was not able to avoid the 

violation and has taken all reasonable steps to minimize the extent of the 

nonconformity.

(C) No other allowances are available under the regulations in this chapter to 

avoid the impending violation.
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(ii) To apply for an exemption, the manufacturer must send to the Administrator a 

written request as soon as possible before being in violation. In the request, the 

manufacturer must show that all the conditions and requirements of paragraph 

(a)(6)(i) of this section are met.

(iii) The request must also include a plan showing how all the applicable 

requirements will be met as quickly as possible.

(iv) The manufacturer shall give the Administrator other relevant information upon 

request.

(v) The Administrator may include additional conditions on an approval granted 

under the provisions of this paragraph (a)(6), including provisions that may require 

field repair at the manufacturer’s expense to correct the noncompliance.

(vi) Engines sold as non-compliant under this temporary hardship provision must 

display “non-OBD” in the data stream as required under paragraph (k)(4)(ii) of this 

section. Upon correcting the noncompliance, the data stream value must be updated 

accordingly.

(b) Malfunction indicator light (MIL) and Diagnostic Trouble Codes (DTC). The OBD 

system must incorporate a malfunction indicator light (MIL) or equivalent and must 

store specific types of diagnostic trouble codes (DTC). Unless otherwise specified, all 

provisions of this paragraph (b) apply for 2010 and later model years.

(1) MIL specifications.

(i) For model years 2013 and later, the MIL must be located on the primary driver’s 

side instrument panel and be of sufficient illumination and location to be readily 

visible under all lighting conditions. The MIL must be amber (yellow) in color; the 

use of red for the OBD-related MIL is prohibited. More than one general purpose 

malfunction indicator light for emission-related problems shall not be used; separate 

specific purpose warning lights (e.g., brake system, fasten seat belt, oil pressure, 

etc.) are permitted. When activated, the MIL shall display the International 

Standards Organization (ISO) engine symbol.

(ii) The OBD system must activate the MIL when the ignition is in the keyon/engine-off position before engine cranking to indicate that the MIL is functional. 

The MIL shall be activated continuously during this functional check for a 

minimum of 5 seconds. During this MIL key-on functional check, the data stream 

value (see paragraph (k)(4)(ii) of this section) for MIL status must indicate 

“commanded off” unless the OBD system has detected a malfunction and has stored 

a MIL-on DTC. This MIL key-on functional check is not required during vehicle 

operation in the key-on/engine-off position subsequent to the initial engine cranking 

of an ignition cycle (e.g., due to an engine stall or other non-commanded engine 

shutoff).
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(iii) As an option, the MIL may be used to indicate readiness status (see paragraph 

(k)(4)(i) of this section) in a standardized format in the key-on/engine-off position.

(iv) A manufacturer may also use the MIL to indicate which, if any, DTCs are 

currently stored (e.g., to “blink” the stored DTCs). Such use must not activate 

unintentionally during routine driver operation.

(v) For model years 2013 and later, the MIL required by this paragraph (b) must not 

be used in any other way than is specified in this section.

(2) MIL activation and DTC storage protocol.

(i) Within 10 seconds of detecting a potential malfunction, the OBD system must 

store a pending DTC that identifies the potential malfunction.

(ii) If the potential malfunction is again detected before the end of the next drive 

cycle during which monitoring occurs (i.e., the potential malfunction has been 

confirmed as a malfunction), then within 10 seconds of such detection the OBD 

system must activate the MIL continuously and store a MIL-on DTC (systems using 

the SAE J1939 standard protocol specified in paragraph (k)(1) of this section may 

either erase or retain the pending DTC in conjunction with storing the MIL-on 

DTC). If the potential malfunction is not detected before the end of the next drive 

cycle during which monitoring occurs (i.e., there is no indication of the malfunction 

at any time during the drive cycle), the corresponding pending DTC should be 

erased at the end of the drive cycle. Similarly, if a malfunction is detected for the 

first time and confirmed on a given drive cycle without need for further evaluation, 

then within 10 seconds of such detection the OBD system must activate the MIL 

continuously and store a MIL-on DTC (again, systems using the SAE J1939 

standard protocol specified in paragraph (k)(1) of this section may optionally store a 

pending DTC in conjunction with storing the MIL-on DTC).

(iii) A manufacturer may request Administrator approval to employ alternative 

statistical MIL activation and DTC storage protocols to those specified in 

paragraphs (b)(2)(i) and (b)(2)(ii) of this section. Approval will depend upon the 

manufacturer providing data and/or engineering evaluations that demonstrate that 

the alternative protocols can evaluate system performance and detect malfunctions 

in a manner that is equally effective and timely. Strategies requiring on average 

more than six drive cycles for MIL activation will not be accepted.

 

(iv) The OBD system must store a “freeze frame” of the operating conditions (as 

defined in paragraph (k)(4)(iii) of this section) present upon detecting a malfunction 

or a potential malfunction. In the event that a pending DTC has matured to a MILon DTC, the manufacturer shall either retain the currently stored freeze frame 

conditions or replace the stored freeze frame with freeze frame conditions regarding 

the MIL-on DTC. Any freeze frame stored in conjunction with any pending DTC or 

MIL-on DTC should be erased upon erasure of the corresponding DTC.
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(v) If the engine enters a limp-home mode of operation that can affect emissions or 

the performance of the OBD system, or in the event of a malfunction of an onboard 

computer(s) itself that can affect the performance of the OBD system, the OBD 

system must activate the MIL and store a MIL-on DTC within 10 seconds to inform 

the vehicle operator. If the limp-home mode of operation is recoverable (i.e., 

operation automatically returns to normal at the beginning of the following ignition 

cycle), the OBD system may wait to activate the MIL and store the MIL-on DTC if 

the limp-home mode of operation is again entered before the end of the next 

ignition cycle rather than activating the MIL within 10 seconds on the first drive 

cycle during which the limp-home mode of operation is entered.

(vi) Before the end of an ignition cycle, the OBD system must store a permanent 

DTC(s) that corresponds to any stored MIL-on DTC(s).

(3) MIL deactivation and DTC erasure protocol

(i) Deactivating the MIL. Except as otherwise provided for in paragraphs 

(g)(2)(iv)(E) and (g)(6)(iv)(B) of this section for diesel misfire malfunctions and 

empty reductant tanks, and paragraphs (h)(1)(iv)(F), (h)(2)(viii), and (h)(7)(iv)(B) 

of this section for gasoline fuel system, misfire, and evaporative system 

malfunctions, once the MIL has been activated, it may be deactivated after three 

subsequent sequential drive cycles during which the monitoring system responsible 

for activating the MIL functions and the previously detected malfunction is no 

longer present and provided no other malfunction has been detected that would 

independently activate the MIL according to the requirements outlined in paragraph 

(b)(2) of this section.

(ii) Erasing a MIL-on DTC. The OBD system may erase a MIL-on DTC if the 

identified malfunction has not again been detected in at least 40 engine warm up 

cycles and the MIL is presently not activated for that malfunction. The OBD system 

may also erase a MIL-on DTC upon deactivating the MIL according to paragraph 

(b)(3)(i) of this section provided a previous-MIL-on DTC is stored upon erasure of 

the MIL-on DTC. The OBD system may erase a previous-MIL-on DTC if the 

identified malfunction has not again been detected in at least 40 engine warm up 

cycles and the MIL is presently not activated for that malfunction.

(iii) Erasing a permanent DTC. The OBD system can erase a permanent DTC only 

if:

(A) The OBD system itself determines that the malfunction that caused the 

corresponding permanent DTC to be stored is no longer present and is not 

commanding activation of the MIL, concurrent with the requirements of 

paragraph (b)(3)(i) of this section which, for purposes of this paragraph (b)(3)(iii), 

shall apply to all monitors.

(B) All externally erasable DTC information stored in the onboard computer has 

been erased (i.e., through the use of a scan tool or battery disconnect) and the 
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monitor of the malfunction that caused the permanent DTC to be stored is subject 

to the minimum ratio requirements of paragraph (d) of this section, the OBD 

system shall erase the permanent DTC at the end of a drive cycle if the monitor 

has run and made one or more determinations during a drive cycle that the 

malfunction of the component or the system is not present and has not made any 

determinations within the same drive cycle that the malfunction is present.

(C)

1. All externally erasable DTC information stored in the onboard computer 

has been erased (i.e., through the use of a scan tool or battery disconnect) and 

the monitor of the malfunction that caused the permanent DTC to be stored is 

not subject to the minimum ratio requirements of paragraph (d) of this section, 

the OBD system shall erase the permanent DTC at the end of a drive cycle 

provided the following two criteria have independently been satisfied:

i. The monitor has run and made one or more determinations during a 

drive cycle that the malfunction is no longer present and has not made any 

determinations within the same drive cycle that the malfunction is present; 

and,

ii. The monitor does not detect a malfunction on a drive cycle and the 

criteria of paragraph (d)(4)(ii) of this section has been met.

2. These two separate criteria may be met on the same or different drive 

cycles provided the monitor never detects a malfunction during either drive 

cycle, and if criteria (b)(3)(iii)(C)(1)(i) happens first then no malfunction may 

be detected before criteria (b)(3)(iii)(C)(1)(ii) occurs. If a malfunction occurs 

after criteria (b)(3)(iii)(C)(1)(i) then criteria (b)(3)(iii)(C)(1)(i) must be 

satisfied again. For the second criterion, the manufacturer must exclude any 

temperature and/or elevation provisions of paragraph (d)(4)(ii) of this section. 

For this paragraph (b)(3)(iii)(C), monitors required to use “similar conditions”

as defined in § 86.010-2 to store and erase pending and MIL-on DTCs cannot 

require that the similar conditions be met prior to erasure of the permanent 

DTC.

(D) The Administrator shall allow monitors subject to paragraph (b)(3)(iii)(B) of 

this section to use the criteria of paragraph (b)(3)(iii)(C) of this section in lieu of 

paragraph (b)(3)(iii)(B). Further, manufacturers may request Administrator 

approval to use alternative criteria to erase the permanent DTC. The 

Administrator shall approve alternate criteria that will not likely require driving 

conditions that are longer and more difficult to meet than those required under 

paragraph (b)(3)(iii)(C) of this section and do not require access to enhanced scan 

tools to determine conditions necessary to erase the permanent DTC.

(4) Exceptions to MIL and DTC requirements.
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(i) If a limp-home mode of operation causes a overt indication (e.g., activation of a 

red engine shut-down warning light) such that the driver is certain to respond and 

have the problem corrected, a manufacturer may choose not to activate the MIL as 

required by paragraph (b)(2)(v) of this section. Additionally, if an auxiliary 

emission control device has been properly activated as approved by the 

Administrator, a manufacturer may choose not to activate the MIL.

(ii) For gasoline engines, a manufacturer may choose to meet the MIL and DTC 

requirements in § 86.007-17 in lieu of meeting the requirements of paragraph (b) of 

this § 86.010-18.

(c) Monitoring conditions. The OBD system must monitor and detect the malfunctions 

specified in paragraphs (g), (h), and (i) of this section under the following general 

monitoring conditions. The more specific monitoring conditions of paragraph (d) of this 

section are sometimes required according to the provisions of paragraphs (g), (h), and 

(i) of this section.

(1) As specifically provided for in paragraphs (g), (h), and (i) of this section, the 

monitoring conditions for detecting malfunctions must be technically necessary to 

ensure robust detection of malfunctions (e.g., avoid false passes and false indications 

of malfunctions); designed to ensure monitoring will occur under conditions that may 

reasonably be expected to be encountered in normal vehicle operation and normal 

vehicle use; and, designed to ensure monitoring will occur during the FTP transient 

test cycle contained in appendix I paragraph (f), of this part, or similar drive cycle as 

approved by the Administrator.

(2) Monitoring must occur at least once per drive cycle in which the monitoring 

conditions are met.

(3) Manufacturers may define monitoring conditions that are not encountered during 

the FTP cycle as required in paragraph (c)(1) of this section. In doing so, the 

manufacturer would be expected to consider the degree to which the requirement to 

run during the FTP transient cycle restricts monitoring during in-use operation, the 

technical necessity for defining monitoring conditions that are not encountered during 

the FTP cycle, whether monitoring is otherwise not feasible during the FTP cycle, 

and/or the ability to demonstrate that the monitoring conditions satisfy the minimum 

acceptable in-use monitor performance ratio requirement as defined in paragraph (d) 

of this section.

(d) In-use performance tracking. As specifically required in paragraphs (g), (h), and (i) 

of this section, the OBD system must monitor and detect the malfunctions specified in 

paragraphs (g), (h), and (i) of this section according to the criteria of this paragraph (d). 

The OBD system is not required to track and report in-use performance for monitors 

other than those specifically identified in paragraph (d)(1) of this section, but all 

monitors on applicable model year engines are still required to meet the in-use 

performance ratio as specified in paragraph (d)(1)(ii) of this section.
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(1) The manufacturer must implement software algorithms in the OBD system to 

individually track and report the in-use performance of the following monitors, if 

equipped, in the standardized format specified in paragraph (e) of this section: 

NMHC converting catalyst (paragraph (g)(5) of this section); NOx converting catalyst 

(paragraph (g)(6) of this section); gasoline catalyst (paragraph (h)(6) of this section); 

exhaust gas sensor (paragraph (g)(9) of this section) or paragraph (h)(8) of this 

section); evaporative system (paragraph (h)(7) of this section); EGR system 

(paragraph (g)(3) of this section or (h)(3) of this section); VVT system (paragraph 

(g)(10) of this section or (h)(9) of this section); secondary air system (paragraph 

(h)(5) of this section); DPF system (paragraph (g)(8) of this section); boost pressure 

control system (paragraph (g)(4) of this section); and, NOx adsorber system 

(paragraph (g)(7) of this section).

(i) The manufacturer shall not use the calculated ratio specified in paragraph (d)(2) 

of this section or any other indication of monitor frequency as a monitoring 

condition for a monitor (e.g., using a low ratio to enable more frequent monitoring 

through diagnostic executive priority or modification of other monitoring 

conditions, or using a high ratio to enable less frequent monitoring).

(ii) For model years 2013 and later, manufacturers must define monitoring 

conditions that, in addition to meeting the criteria in paragraphs (c)(1) and (d)(1) of 

this section, ensure that the monitor yields an in-use performance ratio (as defined 

in paragraph (d)(2) of this section) that meets or exceeds the minimum acceptable 

in-use monitor performance ratio of 0.100 for all monitors specifically required in 

paragraphs (g), (h), and (i) of this section to meet the monitoring condition 

requirements of this paragraph (d).

(iii) If the most reliable monitoring method developed requires a lower ratio for a 

specific monitor than that specified in paragraph (d)(1)(ii) of this section, the 

Administrator may lower the minimum acceptable in-use monitoring performance 

ratio.

(2) In-use performance ratio definition. For monitors required to meet the 

requirements of paragraph (d) of this section, the performance ratio must be 

calculated in accordance with the specifications of this paragraph (d)(2).

(i) The numerator of the performance ratio is defined as the number of times a 

vehicle has been operated such that all monitoring conditions have been 

encountered that are necessary for the specific monitor to detect a malfunction.

(ii) The denominator is defined as the number of times a vehicle has been operated 

in accordance with the provisions of paragraph (d)(4) of this section.

(iii) The performance ratio is defined as the numerator divided by the denominator.

(3) Specifications for incrementing the numerator.
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(i) Except as provided for in paragraph (d)(3)(v) of this section, the numerator, 

when incremented, must be incremented by an integer of one. The numerator shall 

not be incremented more than once per drive cycle.

(ii) The numerator for a specific monitor must be incremented within 10 seconds if 

and only if the following criteria are satisfied on a single drive cycle:

(A) Every monitoring condition has been satisfied that is necessary for the 

specific monitor to detect a malfunction and store a pending DTC, including 

applicable enable criteria, presence or absence of related DTCs, sufficient length 

of monitoring time, and diagnostic executive priority assignments (e.g., diagnostic 

“A” must execute prior to diagnostic “B”). For the purpose of incrementing the 

numerator, satisfying all the monitoring conditions necessary for a monitor to 

determine that the monitor is not malfunctioning shall not, by itself, be sufficient 

to meet this criteria.

(B) For monitors that require multiple stages or events in a single drive cycle to 

detect a malfunction, every monitoring condition necessary for all events to 

complete must be satisfied.

(C) For monitors that require intrusive operation of components to detect a 

malfunction, a manufacturer must request approval of the strategy used to 

determine that, had a malfunction been present, the monitor would have detected 

the malfunction. Administrator approval of the request will be based on the 

equivalence of the strategy to actual intrusive operation and the ability of the 

strategy to determine accurately if every monitoring condition was satisfied that 

was necessary for the intrusive event to occur.

(D) For the secondary air system monitor, the criteria in paragraphs (d)(3)(ii)(A) 

through (d)(3)(ii)(C) of this section are satisfied during normal operation of the 

secondary air system. Monitoring during intrusive operation of the secondary air 

system later in the same drive cycle for the sole purpose of monitoring shall not, 

by itself, be sufficient to meet these criteria.

(iii) For monitors that can generate results in a “gray zone” or “non-detection zone”

(i.e., monitor results that indicate neither a properly operating system nor a 

malfunctioning system) or in a “non-decision zone” (e.g., monitors that increment 

and decrement counters until a pass or fail threshold is reached), the numerator, in 

general, shall not be incremented when the monitor indicates a result in the “nondetection zone” or prior to the monitor reaching a complete decision. When 

necessary, the Administrator will consider data and/or engineering analyses 

submitted by the manufacturer demonstrating the expected frequency of results in 

the “non-detection zone” and the ability of the monitor to determine accurately, had 

an actual malfunction been present, whether or not the monitor would have detected 

a malfunction instead of a result in the “non-detection zone.”
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(iv) For monitors that run or complete their evaluation with the engine off, the 

numerator must be incremented either within 10 seconds of the monitor completing 

its evaluation in the engine off state, or during the first 10 seconds of engine start on 

the subsequent drive cycle.

(v) Manufacturers that use alternative statistical MIL activation protocols as 

allowed in paragraph (b)(2)(iii) of this section for any of the monitors requiring a 

numerator, are required to increment the numerator(s) appropriately. The 

manufacturer may be required to provide supporting data and/or engineering 

analyses demonstrating both the equivalence of their incrementing approach to the 

incrementing specified in this paragraph (d)(3) for monitors using the standard MIL 

activation protocol, and the overall equivalence of the incrementing approach in 

determining that the minimum acceptable in-use performance ratio of paragraph 

(d)(1)(ii) of this section, if applicable, has been satisfied.

(4) Specifications for incrementing the denominator.

(i) The denominator, when incremented, must be incremented by an integer of one. 

The denominator shall not be incremented more than once per drive cycle.

(ii) The denominator for each monitor must be incremented within 10 seconds if 

and only if the following criteria are satisfied on a single drive cycle:

(A) Cumulative time since the start of the drive cycle is greater than or equal to 

600 seconds while at an elevation of less than 8,000 feet (2,400 meters) above sea 

level and at an ambient temperature of greater than or equal to 20 degrees 

Fahrenheit (−7 C);

(B) Cumulative gasoline engine operation at or above 25 miles per hour or diesel 

engine operation at or above 1,150 rotations per minute (diesel engines may use 

the gasoline criterion for 2010 through 2012 model years), either of which occurs 

for greater than or equal to 300 seconds while at an elevation of less than 8,000 

feet (2,400 meters) above sea level and at an ambient temperature of greater than 

or equal to 20 degrees Fahrenheit (−7 C); and,

(C) Continuous engine operation at idle (e.g., accelerator pedal released by driver 

and engine speed less than or equal to 200 rpm above normal warmed-up idle (as 

determined in the drive position for vehicles equipped with an automatic 

transmission) or vehicle speed less than or equal to one mile per hour) for greater 

than or equal to 30 seconds while at an elevation of less than 8,000 feet (2,400 

meters) above sea level and at an ambient temperature of greater than or equal to 

20 degrees Fahrenheit (−7 C).

(iii) In addition to the requirements of paragraph (d)(4)(ii) of this section, the 

evaporative system monitor denominator(s) may be incremented if and only if:
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(A) Cumulative time since the start of the drive cycle is greater than or equal to 

600 seconds while at an ambient temperature of greater than or equal to 40 

degrees Fahrenheit (4 C) but less than or equal to 95 degrees Fahrenheit (35 C); 

and,

(B) Engine cold start occurs with the engine coolant temperature greater than or 

equal to 40 degrees Fahrenheit (4 C) but less than or equal to 95 degrees 

Fahrenheit (35 C) and less than or equal to 12 degrees Fahrenheit (7 C) higher 

than the ambient temperature.

(iv) In addition to the requirements of paragraph (d)(4)(ii) of this section, the 

denominator(s) for the following monitors may be incremented if and only if the 

component or strategy is commanded “on” for a cumulative time greater than or 

equal to 10 seconds. For purposes of determining this commanded “on” time, the 

OBD system shall not include time during intrusive operation of any of the 

components or strategies that occurs later in the same drive cycle for the sole 

purpose of monitoring.

(A) Secondary air system (paragraph (h)(5) of this section).

(B) Cold start emission reduction strategy (paragraph (h)(4) of this section).

(C) Components or systems that operate only at engine start-up (e.g., glow plugs, 

intake air heaters) and are subject to monitoring under “other emission control 

systems” (paragraph (i)(4) of this section) or comprehensive component output 

components (paragraph (i)(3)(iii) of this section).

(v) In addition to the requirements of paragraph (d)(4)(ii) of this section, the 

denominator(s) for the following monitors of output components (except those 

operated only at engine start-up and subject to the requirements of paragraph 

(d)(4)(iv) of this section, may be incremented if and only if the component is 

commanded to function (e.g., commanded “on”, “opened”, “closed”, “locked”) on 

two or more occasions during the drive cycle or for a cumulative time greater than 

or equal to 10 seconds, whichever occurs first:

(A) Variable valve timing and/or control system (paragraph (g)(10) of this section 

or (h)(9) of this section).

(B) “Other emission control systems” (paragraph (i)(4) of this section).

(C) Comprehensive component output component (paragraph (i)(3) of this 

section) (e.g., turbocharger waste-gates, variable length manifold runners).

(vi) For monitors of the following components, the manufacturer may use 

alternative or additional criteria for incrementing the denominator to that set forth in 

paragraph (d)(4)(ii) of this section. To do so, the alternative criteria must be based 
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on equivalence to the criteria of paragraph (d)(4)(ii) of this section in measuring the 

frequency of monitor operation relative to the amount of engine operation:

(A) Engine cooling system input components (paragraph (i)(1) of this section).

(B) “Other emission control systems” (paragraph (i)(4) of this section).

(C) Comprehensive component input components that require extended 

monitoring evaluation (paragraph (i)(3) of this section) (e.g., stuck fuel level 

sensor rationality).

(D) Comprehensive component input component temperature sensor rationality 

monitors (paragraph (i)(3) of this section) (e.g., intake air temperature sensor, 

ambient temperature sensor, fuel temperature sensor).

(E) Diesel particulate filter (DPF) frequent regeneration (paragraph (g)(8)(ii)(B) 

of this section).

(vii) For monitors of the following components or other emission controls that 

experience infrequent regeneration events, the manufacturer may use alternative or 

additional criteria for incrementing the denominator to that set forth in paragraph 

(d)(4)(ii) of this section. To do so, the alternative criteria must be based on 

equivalence to the criteria of paragraph (d)(4)(ii) of this section in measuring the 

frequency of monitor operation relative to the amount of engine operation:

(A) NMHC converting catalyst (paragraph (g)(5) of this section).

(B) Diesel particulate filter (DPF) (paragraphs (g)(8)(ii)(A) and (g)(8)(ii)(D) of 

this section).

(viii) In addition to the requirements of paragraph (d)(4)(ii) of this section, the 

denominator(s) for the following monitors shall be incremented if and only if a 

regeneration event is commanded for a time greater than or equal to 10 seconds:

(A) DPF incomplete regeneration (paragraph (g)(8)(ii)(C) of this section).

(B) DPF active/intrusive injection (paragraph (g)(8)(ii)(E) of this section).

(ix) For hybrids that employ alternative engine start hardware or strategies (e.g., 

integrated starter and generators), or alternative fuel vehicles (e.g., dedicated, bifuel, or dual-fuel applications), the manufacturer may use alternative criteria for

incrementing the denominator to that set forth in paragraph (d)(4)(ii) of this section. 

In general, the Administrator will not approve alternative criteria for those hybrids 

that employ engine shut off only at or near idle and/or vehicle stop conditions. To 

use alternative criteria, the alternative criteria must be based on the equivalence to 

the criteria of paragraph (d)(4)(ii) of this section in measuring the amount of vehicle 

operation relative to the measure of conventional vehicle operation.
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(5) Disablement of numerators and denominators.

(i) Within 10 seconds of detecting a malfunction (i.e., a pending or a MIL-on DTC 

has been stored) that disables a monitor for which the monitoring conditions in 

paragraph (d) of this section must be met, the OBD system must stop incrementing 

the numerator and denominator for any monitor that may be disabled as a 

consequence of the detected malfunction. Within 10 seconds of the time at which 

the malfunction is no longer being detected (e.g., the pending DTC is erased

through OBD system self-clearing or through a scan tool command), incrementing 

of all applicable numerators and denominators must resume.

(ii) Within 10 seconds of the start of a power take-off unit (e.g., dump bed, snow 

plow blade, or aerial bucket, etc.) that disables a monitor for which the monitoring 

conditions in paragraph (d) of this section must be met, the OBD system must stop 

incrementing the numerator and denominator for any monitor that may be disabled 

as a consequence of power take-off operation. Within 10 seconds of the time at 

which the power take-off operation ends, incrementing of all applicable numerators 

and denominators must resume.

(iii) Within 10 seconds of detecting a malfunction (i.e., a pending or a MIL-on DTC 

has been stored) of any component used to determine if the criteria of paragraphs 

(d)(4)(ii) and (d)(4)(iii) of this section are satisfied, the OBD system must stop 

incrementing all applicable numerators and denominators. Within 10 seconds of the 

time at which the malfunction is no longer being detected (e.g., the pending DTC is 

erased through OBD system self-clearing or through a scan tool command), 

incrementing of all applicable numerators and denominators must resume.

(e) Standardized tracking and reporting of in-use monitor performance

(1) General. For monitors required to track and report in-use monitor performance 

according to paragraph (d) of this section, the performance data must be tracked and 

reported in accordance with the specifications in paragraphs (d)(2), (e), and (k)(5) of 

this section. The OBD system must separately report an in-use monitor performance 

numerator and denominator for each of the following components:

(i) For diesel engines, NMHC catalyst bank 1, NMHC catalyst bank 2, NOx catalyst 

bank 1, NOx catalyst bank 2, exhaust gas sensor bank 1, exhaust gas sensor bank 2, 

EGR/VVT system, DPF, boost pressure control system, and NOx adsorber. The 

OBD system must also report a general denominator and an ignition cycle counter 

in the standardized format specified in paragraphs (e)(5), (e)(6), and (k)(5) of this 

section.

 

(ii) For gasoline engines, catalyst bank 1, catalyst bank 2, exhaust gas sensor bank 

1, exhaust gas sensor bank 2, evaporative leak detection system, EGR/VVT system, 

and secondary air system. The OBD system must also report a general denominator 
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and an ignition cycle counter in the standardized format specified in paragraphs 

(e)(5), (e)(6), and (k)(5) of this section.

(iii) For specific components or systems that have multiple monitors that are 

required to be reported under paragraphs (g) and (h) of this section (e.g., exhaust 

gas sensor bank 1 may have multiple monitors for sensor response or other sensor 

characteristics), the OBD system must separately track numerators and 

denominators for each of the specific monitors and report only the corresponding 

numerator and denominator for the specific monitor that has the lowest numerical 

ratio. If two or more specific monitors have identical ratios, the corresponding 

numerator and denominator for the specific monitor that has the highest 

denominator must be reported for the specific component.

(2) Numerator.

(i) The OBD system must report a separate numerator for each of the applicable 

components listed in paragraph (e)(1) of this section.

(ii) The numerator(s) must be reported in accordance with the specifications in 

paragraph (k)(5)(ii) of this section.

(3) Denominator.

(i) The OBD system must report a separate denominator for each of the applicable 

components listed in paragraph (e)(1) of this section.

(ii) The denominator(s) must be reported in accordance with the specifications in 

paragraph (k)(5)(ii) of this section.

(4) Monitor performance ratio. For purposes of determining which corresponding 

numerator and denominator to report as required in paragraph (e)(1)(iii) of this 

section, the ratio must be calculated in accordance with the specifications in 

paragraph (k)(5)(iii) of this section.

(5) Ignition cycle counter.

(i) The ignition cycle counter is defined as a counter that indicates the number of 

ignition cycles a vehicle has experienced according to the specifications of 

paragraph (e)(5)(ii)(B) of this section. The ignition cycle counter must be reported 

in accordance with the specifications in paragraph (k)(5)(ii) of this section.

(ii) The ignition cycle counter must be incremented as follows:

(A) The ignition cycle counter, when incremented, must be incremented by an 

integer of one. The ignition cycle counter shall not be incremented more than 

once per ignition cycle.
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(B) The ignition cycle counter must be incremented within 10 seconds if and only 

if the engine exceeds an engine speed of 50 to 150 rpm below the normal, 

warmed-up idle speed (as determined in the drive position for engines paired with 

an automatic transmission) for at least two seconds plus or minus one second.

(iii) Within 10 seconds of detecting a malfunction (i.e., a pending or a MIL-on DTC 

has been stored) of any component used to determine if the criteria in paragraph 

(e)(5)(ii)(B) of this section are satisfied (i.e., engine speed or time of operation), the 

OBD system must stop incrementing the ignition cycle counter. Incrementing of the 

ignition cycle counter shall not be stopped for any other condition. Within 10 

seconds of the time at which the malfunction is no longer being detected (e.g., the 

pending DTC is erased through OBD system self-clearing or through a scan tool 

command), incrementing of the ignition cycle counter must resume.

(6) General denominator.

(i) The general denominator is defined as a measure of the number of times an 

engine has been operated according to the specifications of paragraph (e)(6)(ii)(B) 

of this section. The general denominator must be reported in accordance with the 

specifications in paragraph (k)(5)(ii) of this section.

(ii) The general denominator must be incremented as follows:

(A) The general denominator, when incremented, must be incremented by an 

integer of one. The general denominator shall not be incremented more than once 

per drive cycle.

(B) The general denominator must be incremented within 10 seconds if and only 

if the criteria identified in paragraph (d)(4)(ii) of this section are satisfied on a 

single drive cycle.

 

(C) Within 10 seconds of detecting a malfunction (i.e., a pending or a MIL-on 

DTC has been stored) of any component used to determine if the criteria in 

paragraph (d)(4)(ii) of this section are satisfied (i.e., vehicle speed/load, ambient 

temperature, elevation, idle operation, or time of operation), the OBD system 

must stop incrementing the general denominator. Incrementing of the general 

denominator shall not be stopped for any other condition (e.g., the disablement 

criteria in paragraphs (d)(5)(i) and (d)(5)(ii) of this section shall not disable the 

general denominator). Within 10 seconds of the time at which the malfunction is 

no longer being detected (e.g., the pending DTC is erased through OBD system 

self-clearing or through a scan tool command), incrementing of the general 

denominator must resume.

(f) Malfunction criteria determination.

(1) In determining the malfunction criteria for the diesel engine monitors required 

under paragraphs (g) and (i) of this section that are required to indicate a malfunction 
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before emissions exceed an emission threshold based on any applicable standard, the 

manufacturer must:

(i) Use the emission test cycle and standard (i.e., the transient FTP or the 

supplemental emissions test (SET)) determined by the manufacturer to provide the 

most effective monitoring conditions and robust monitor provided all other 

applicable requirements of this section are met.

(ii) Identify in the certification documentation required under paragraph (m) of this 

section, the test cycle and standard determined by the manufacturer to be the most 

stringent for each applicable monitor and the most effective and robust for each 

applicable monitor.

(iii) If the Administrator reasonably believes that a manufacturer has determined 

incorrectly the test cycle and standard that is most stringent or effective, the 

manufacturer must be able to provide emission data and/or engineering analysis 

supporting their choice of test cycle and standard.

(2) On engines equipped with emission controls that experience infrequent 

regeneration events, a manufacturer need not adjust the emission test results that are 

used to determine the malfunction criteria for monitors that are required to indicate a 

malfunction before emissions exceed a certain emission threshold. For each such 

monitor, should the manufacturer choose to adjust the emission test results, the 

manufacturer must adjust the emission result as done in accordance with the 

provisions of § 86.004-28(i) with the component for which the malfunction criteria 

are being established having been deteriorated to the malfunction threshold. The 

adjusted emission value must be used for purposes of determining whether or not the 

applicable emission threshold is exceeded.

(i) For purposes of this paragraph (f)(2), regeneration means an event, by design, 

during which emissions levels change while the emission control performance is 

being restored.

(ii) For purposes of this paragraph (f)(2), infrequent means having an expected 

frequency of less than once per transient FTP cycle.

(3) For gasoline engines, rather than meeting the malfunction criteria specified under 

paragraphs (h) and (i) of this section, the manufacturer may request approval to use 

an OBD system certified to the requirements of § 86.007-17. To do so, the 

manufacturer must demonstrate use of good engineering judgment in determining 

equivalent malfunction detection criteria to those required in this section.

(g) OBD monitoring requirements for diesel-fueled/compression-ignition engines. The 

following table shows the thresholds at which point certain components or systems, as 

specified in this paragraph (g), are considered malfunctioning.

(1) Fuel system monitoring
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(i) General. The OBD system must monitor the fuel delivery system to verify that it 

is functioning properly. The individual electronic components (e.g., actuators, 

valves, sensors, pumps) that are used in the fuel system and are not specifically 

addressed in this paragraph (g)(1) must be monitored in accordance with the 

requirements of paragraph (i)(3) of this section.

(ii) Fuel system malfunction criteria

(A) Fuel system pressure control. The OBD system must monitor the fuel 

system’s ability to control to the desired fuel pressure. This monitoring must be 

done continuously unless new hardware has to be added, in which case the 

monitoring must be done at least once per drive cycle. The OBD system must 

detect a malfunction of the fuel system’s pressure control system when the 

pressure control system is unable to maintain an engine’s emissions at or below 

the emissions thresholds for “other monitors” as shown in Table 1 of this 

paragraph (g). For engines in which no failure or deterioration of the fuel system 

pressure control could result in an engine’s emissions exceeding the applicable 

emissions thresholds, the OBD system must detect a malfunction when the system 

has reached its control limits such that the commanded fuel system pressure 

cannot be delivered. For model year 2010 to 2012 engines with a unit injector fuel 

system, this requirement may be met by conducting a functional check of the fuel 

system pressure control in lieu of monitoring for conditions that could cause an 

engine’s emissions to exceed the applicable emissions thresholds.

(B) Fuel system injection quantity. The OBD system must detect a malfunction of 

the fuel injection system when the system is unable to deliver the commanded 

quantity of fuel necessary to maintain an engine’s emissions at or below the 

emissions thresholds for “other monitors” as shown in Table 1 of this paragraph 

(g). For engines in which no failure or deterioration of the fuel injection quantity 

could result in an engine’s emissions exceeding the applicable emissions 

thresholds, the OBD system must detect a malfunction when the system has 

reached its control limits such that the commanded fuel quantity cannot be 

delivered. For model year 2010 to 2012 engines with a unit injector fuel system, 

this requirement may be met by conducting a functional check of the fuel system 

injection quantity in lieu of monitoring for conditions that could cause an engine’s 

emissions to exceed the applicable emissions thresholds.

(C) Fuel system injection timing. The OBD system must detect a malfunction of 

the fuel injection system when the system is unable to deliver fuel at the proper 

crank angle/timing (e.g., injection timing too advanced or too retarded) necessary 

to maintain an engine’s emissions at or below the emissions thresholds for “other 

monitors” as shown in Table 1 of this paragraph (g). For engines in which no 

failure or deterioration of the fuel injection timing could result in an engine’s 

emissions exceeding the applicable emissions thresholds, the OBD system must 

detect a malfunction when the system has reached its control limits such that the
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Table 1 – OBD Emissions Thresholds for Diesel-Fueled/Compression-Ignition Engines 

Meant for Placement in Applications Greater Than 14,000 Pounds GVWR (g/bhp-hr)

Notes: FEL = Family Emissions Limit; 2.5x std means a multiple of 2.5 times the applicable emissions 

standard; +0.3 means the standard or FEL plus 0.3; 0.05/+0.04 means an absolute level of 0.05 or an 

additive level of the standard or FEL plus 0.04, whichever level is higher; these emissions thresholds apply 

to the monitoring requirements of paragraph (g) of this § 86.010-18.

commanded fuel injection timing cannot be achieved. For model year 2010 to 

2012 engines with a unit injector fuel system, this requirement may be met by 

conducting a functional check of the fuel system injection timing in lieu of 

monitoring for conditions that could cause an engine’s emissions to exceed the 

applicable emissions thresholds.

(D) Combined Monitoring. For engines with a unit injector fuel system, the 

manufacturer may request Administrator approval to combine the malfunction 

criteria of paragraphs (g)(1)(ii)(A) through (g)(1)(ii)(C) of this section into one 

malfunction provided the manufacturer can demonstrate that the combined 

malfunction will satisfy the intent of each separate malfunction criteria. For 

engines with a common rail fuel system, the manufacturer may request 

Administrator approval to combine the malfunction criteria of paragraphs 

(g)(1)(ii)(B) through (g)(1)(ii)(C) of this section into one malfunction provided 

the manufacturer can demonstrate that the combined malfunction will satisfy the 

intent of each separate malfunction criteria.

(E) Fuel system feedback control. See paragraph (i)(6) of this section.
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(iii) Fuel system monitoring conditions.

(A) With the exceptions noted in this paragraph for unit injector systems, the 

OBD system must monitor continuously for malfunctions identified in paragraphs 

(g)(1)(ii)(A) and (g)(1)(ii)(E) of this section. For 2010 through 2012 unit injector 

systems, where functional monitoring is done in lieu of emission threshold 

monitoring for malfunctions identified in paragraph (g)(1)(ii)(A) of this section, 

the manufacturer must define the monitoring conditions in accordance with 

paragraphs (c) and (d) of this section. For 2013 and later unit injector systems, the 

manufacturer must define the monitoring conditions for malfunctions identified in 

paragraph (g)(1)(ii)(A) of this section in accordance with paragraphs (c) and (d) 

of this section, with the exception that monitoring must occur every time the 

monitoring conditions are met during the drive cycle rather than once per drive 

cycle as required in paragraph (c)(2) of this section.

(B) For 2010 through 2012, the manufacturer must define the monitoring 

conditions for malfunctions identified in paragraphs (g)(1)(ii)(B), (g)(1)(ii)(C), 

and (g)(1)(ii)(D) of this section in accordance with paragraphs (c) and (d) of this 

section. For 2013 and later, the manufacturer must define the monitoring 

conditions in accordance with paragraphs (c) and (d) of this section, with the 

exception that monitoring must occur every time the monitoring conditions are 

met during the drive cycle rather than once per drive cycle as required in 

paragraph (c)(2) of this section.

(iv) Fuel system MIL activation and DTC storage. The MIL must activate and 

DTCs must be stored according to the provisions of paragraph (b) of this section.

(2) Engine misfire monitoring

(i) General. The OBD system must monitor the engine for misfire causing excess 

emissions.

(ii) Engine misfire malfunction criteria.

(A) The OBD system must be capable of detecting misfire occurring in one or 

more cylinders. To the extent possible without adding hardware for this specific 

purpose, the OBD system must also identify the specific misfiring cylinder. If 

more than one cylinder is misfiring continuously, or if more than one but less than 

half of the cylinders are misfiring continuously (if the manufacturer can 

demonstrate the robustness of their monitor to the approval of the Administrator), 

a separate DTC must be stored indicating that multiple cylinders are misfiring. 

When identifying multiple cylinder misfire, the OBD system is not required to 

identify individually through separate DTCs each of the continuously misfiring 

cylinders.

(B) For model years 2013 and later, on engines equipped with sensors that can 

detect combustion or combustion quality (e.g., for use in engines with 
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homogeneous charge compression ignition (HCCI) control systems), the OBD 

system must detect a misfire malfunction causing emissions to exceed the 

applicable thresholds for “other monitors” shown in Table 1 of this paragraph (g). 

To determine what level of misfire would cause emissions to exceed the 

applicable emissions thresholds, the manufacturer must determine the percentage 

of misfire evaluated in 1,000 revolution increments that would cause emissions 

from an emission durability demonstration engine to exceed the emissions 

thresholds if the percentage of misfire were present from the beginning of the test. 

To establish this percentage of misfire, the manufacturer must use misfire events 

occurring at equally spaced, complete engine cycle intervals, across randomly 

selected cylinders throughout each 1,000-revolution increment. If this percentage 

of misfire is determined to be lower than one percent, the manufacturer may set 

the malfunction criteria at one percent. Any misfire malfunction must be detected 

if the percentage of misfire established via this testing is exceeded regardless of 

the pattern of misfire events (e.g., random, equally spaced, continuous). The 

manufacturer may employ other revolution increments besides the 1,000 

revolution increment. To do so, the manufacturer must demonstrate that the 

strategy is equally effective and timely in detecting misfire.

(iii) Engine misfire monitoring conditions.

(A) The OBD system must monitor for engine misfire during engine idle 

conditions at least once per drive cycle in which the monitoring conditions for 

misfire are met. The manufacturer must be able to demonstrate via engineering 

analysis and/or data that the self-defined monitoring conditions: are technically 

necessary to ensure robust detection of malfunctions (e.g., avoid false passes and 

false detection of malfunctions); require no more than 1000 cumulative engine 

revolutions; and, do not require any single continuous idle operation of more than 

15 seconds to make a determination that a malfunction is present (e.g., a decision 

can be made with data gathered during several idle operations of 15 seconds or 

less); or, satisfy the requirements of paragraph (c) of this section with alternative 

engine operating conditions.

(B) Manufacturers may employ alternative monitoring conditions (e.g., off-idle) 

provided the manufacturer is able to demonstrate that the alternative monitoring 

ensure equivalent robust detection of malfunctions and equivalent timeliness in 

detection of malfunctions.

(C) For model years 2013 and later, on engines equipped with sensors that can 

detect combustion or combustion quality the OBD system must monitor 

continuously for engine misfire under all positive torque engine speed and load 

conditions. If a monitoring system cannot detect all misfire patterns under all 

required engine speed and load conditions, the manufacturer may request that the 

Administrator approve the monitoring system nonetheless. In evaluating the 

manufacturer’s request, the Administrator will consider the following factors: the 

magnitude of the region(s) in which misfire detection is limited; the degree to 

which misfire detection is limited in the region(s) (i.e., the probability of detection 
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of misfire events); the frequency with which said region(s) are expected to be 

encountered in-use; the type of misfire patterns for which misfire detection is 

troublesome; and demonstration that the monitoring technology employed is not 

inherently incapable of detecting misfire under required conditions (i.e., 

compliance can be achieved on other engines). The evaluation will be based on 

the following misfire patterns: equally spaced misfire occurring on randomly 

selected cylinders; single cylinder continuous misfire; and, paired cylinder 

(cylinders firing at the same crank angle) continuous misfire.

(iv) Engine misfire MIL activation and DTC storage.

(A) General requirements for MIL activation and DTC storage are set forth in 

paragraph (b) of this section.

(B) For model years 2013 and later, on engines equipped with sensors that can 

detect combustion or combustion quality, upon detection of the percentage of 

misfire specified in paragraph (g)(2)(ii)(B) of this section, the following criteria 

shall apply for MIL activation and DTC storage: A pending DTC must be stored 

no later than after the fourth exceedance of the percentage of misfire specified in 

paragraph (g)(2)(ii) of this section during a single drive cycle; if a pending fault 

code has been stored, the OBD system must activate the MIL and store a MIL-on 

DTC within 10 seconds if the percentage of misfire specified in paragraph 

(g)(2)(ii) of this section is again exceeded four times during the drive cycle 

immediately following storage of the pending DTC, regardless of the conditions 

encountered during the drive cycle, or on the next drive cycle in which similar 

conditions are encountered to those that were occurring when the pending DTC 

was stored. Similar conditions means an engine speed within 375 rpm, engine 

load within 20 percent, and the same warm up status (i.e., cold or hot). The 

Administrator may approve other definitions of similar conditions based on 

comparable timeliness and reliability in detecting similar engine operation. The 

pending DTC may be erased at the end of the next drive cycle in which similar 

conditions are encountered to those that were occurring when the pending DTC 

was stored provided the specified percentage of misfire was not again exceeded. 

The pending DTC may also be erased if similar conditions are not encountered 

during the 80 drive cycles immediately following initial detection of the 

malfunction.

(C) For model years 2013 and later, on engines equipped with sensors that can 

detect combustion or combustion quality, the OBD system must store and erase 

freeze frame conditions either in conjunction with storing and erasing a pending 

DTC or in conjunction with storing and erasing a MIL-on DTC. If freeze frame 

conditions are stored for a malfunction other than a misfire malfunction when a 

DTC is stored as specified in paragraph (g)(2)(iv)(B) of this section, the stored 

freeze frame information must be replaced with the freeze frame information 

regarding the misfire malfunction.
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(D) For model years 2013 and later, on engines equipped with sensors that can 

detect combustion or combustion quality, upon detection of misfire according to 

paragraph (g)(2)(iv)(B) of this section, the OBD system must also store the 

following engine conditions: engine speed, load, and warm up status of the first 

misfire event that resulted in the storage of the pending DTC.

(E) For model years 2013 and later, on engines equipped with sensors that can 

detect combustion or combustion quality, the MIL may be deactivated after three 

sequential drive cycles in which similar conditions have been encountered without 

an exceedance of the specified percentage of misfire.

(3) EGR system monitoring

(i) General. The OBD system must monitor the EGR system on engines so 

equipped for low flow rate, high flow rate, and slow response malfunctions. For 

engines equipped with EGR coolers (e.g., heat exchangers), the OBD system must 

monitor the cooler for insufficient cooling malfunctions. The individual electronic 

components (e.g., actuators, valves, sensors) that are used in the EGR system must 

be monitored in accordance with the comprehensive component requirements in 

paragraph (i)(3) of this section.

(ii) EGR system malfunction criteria

(A) EGR low flow. The OBD system must detect a malfunction of the EGR 

system prior to a decrease from the manufacturer’s specified EGR flow rate that 

would cause an engine’s emissions to exceed the emissions thresholds for “other 

monitors” as shown in Table 1 of this paragraph (g). For engines in which no 

failure or deterioration of the EGR system that causes a decrease in flow could 

result in an engine’s emissions exceeding the applicable emissions thresholds, the 

OBD system must detect a malfunction when the system has reached its control 

limits such that it cannot increase EGR flow to achieve the commanded flow rate.

(B) EGR high flow. The OBD system must detect a malfunction of the EGR

system, including a leaking EGR valve (i.e., exhaust gas flowing through the 

valve when the valve is commanded closed) prior to an increase from the 

manufacturer’s specified EGR flow rate that would cause an engine’s emissions 

to exceed the emissions thresholds for “other monitors” as shown in Table 1 of 

this paragraph (g). For engines in which no failure or deterioration of the EGR 

system that causes an increase in flow could result in an engine’s emissions 

exceeding the applicable emissions thresholds, the OBD system must detect a 

malfunction when the system has reached its control limits such that it cannot 

reduce EGR flow to achieve the commanded flow rate.

(C) EGR slow response. The OBD system must detect a malfunction of the EGR 

system prior to any failure or deterioration in the capability of the EGR system to 

achieve the commanded flow rate within a manufacturer-specified time that 

would cause an engine’s emissions to exceed the emissions thresholds for “other 
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monitors” as shown in Table 1 of this paragraph (g). The OBD system must 

monitor both the capability of the EGR system to respond to a commanded 

increase in flow and the capability of the EGR system to respond to a commanded 

decrease in flow.

(D) EGR system feedback control. See paragraph (i)(6) of this section.

(E) EGR cooler performance. The OBD system must detect a malfunction of the 

EGR cooler prior to a reduction from the manufacturer’s specified cooling 

performance that would cause an engine’s emissions to exceed the emissions 

thresholds for “other monitors” as shown in Table 1 of this paragraph (g). For 

engines in which no failure or deterioration of the EGR cooler could result in an 

engine’s emissions exceeding the applicable emissions thresholds, the OBD 

system must detect a malfunction when the system has no detectable amount of 

EGR cooling.

(iii) EGR system monitoring conditions.

(A) The OBD system must monitor continuously for malfunctions identified in 

paragraphs (g)(3)(ii)(A), (g)(3)(ii)(B), and (g)(3)(ii)(D) of this section.

(B) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraph (g)(3)(ii)(C) of this section in accordance with paragraphs 

(c) and (d) of this section, with the exception that monitoring must occur every 

time the monitoring conditions are met during the drive cycle rather than once per 

drive cycle as required in paragraph (c)(2) of this section. For purposes of 

tracking and reporting as required in paragraph (d)(1) of this section, all monitors 

used to detect malfunctions identified in paragraph (g)(3)(ii)(C) of this section 

must be tracked separately but reported as a single set of values as specified in 

paragraph (e)(1)(iii) of this section.

(C) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraph (g)(3)(ii)(E) of this section in accordance with paragraphs 

(c) and (d) of this section. For purposes of tracking and reporting as required in 

paragraph (d)(1) of this section, all monitors used to detect malfunctions 

identified in paragraph (g)(3)(ii)(E) of this section must be tracked separately but 

reported as a single set of values as specified in paragraph (e)(1)(iii) of this 

section.

(D) The manufacturer may request Administrator approval to disable temporarily 

the EGR system monitor(s) under specific ambient conditions (e.g., when freezing 

may affect performance of the system) or during specific operating conditions 

(e.g., transients, extreme low or high flow conditions). The manufacturer must be 

able to demonstrate via data or engineering analysis that a reliable system monitor 

cannot be run when these conditions exist because it cannot robustly distinguish 

between a malfunctioning system and a properly operating system. The 
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manufacturer is still required to maintain comprehensive component monitoring 

as required in paragraph (i)(3) of this section.

 

(iv) EGR system MIL activation and DTC storage. The MIL must activate and 

DTCs must be stored according to the provisions of paragraph (b) of this section.

(4) Turbo boost control system monitoring

(i) General. The OBD system must monitor the boost pressure control system (e.g., 

turbocharger) on engines so equipped for under and over boost malfunctions. For 

engines equipped with variable geometry turbochargers (VGT), the OBD system 

must monitor the VGT system for slow response malfunctions. For engines 

equipped with charge air cooler systems, the OBD system must monitor the charge 

air cooler system for cooling system performance malfunctions. The individual 

electronic components (e.g., actuators, valves, sensors) that are used in the boost 

pressure control system must be monitored in accordance with the comprehensive 

component requirements in paragraph (i)(3) of this section.

(ii) Turbo boost control system malfunction criteria

(A) Turbo underboost. The OBD system must detect a malfunction of the boost 

pressure control system prior to a decrease from the manufacturer’s commanded 

boost pressure, or expected boost pressure on engines not equipped with a boost 

pressure control system, that would cause an engine’s emissions to exceed the 

emissions thresholds for “other monitors” as shown in Table 1 of this paragraph 

(g). For engines in which no failure or deterioration of the boost pressure control 

system that causes a decrease in boost could result in an engine’s emissions 

exceeding the applicable emissions thresholds, the OBD system must detect a 

malfunction when the system has reached its control limits such that it cannot 

increase boost to achieve the commanded boost pressure.

(B) Turbo overboost. The OBD system must detect a malfunction of the boost 

pressure control system on engines so equipped prior to an increase from the 

manufacturer’s commanded boost pressure that would cause an engine’s 

emissions to exceed the emissions thresholds for “other monitors” as shown in 

Table 1 of this paragraph (g). For engines in which no failure or deterioration of 

the boost pressure control system that causes an increase in boost could result in 

an engine’s emissions exceeding the applicable emissions thresholds, the OBD 

system must detect a malfunction when the system has reached its control limits 

such that it cannot decrease boost to achieve the commanded boost pressure.

(C) VGT slow response. The OBD system must detect a malfunction prior to any 

failure or deterioration in the capability of the VGT system on engines so 

equipped to achieve the commanded turbocharger geometry within a 

manufacturer-specified time that would cause an engine’s emissions to exceed the 

emissions thresholds for “other monitors” as shown in Table 1 of this paragraph 

(g). For engines in which no failure or deterioration of the VGT system response 
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could result in an engine’s emissions exceeding the applicable emissions 

thresholds, the OBD system must detect a malfunction of the VGT system when 

proper functional response of the system to computer commands does not occur.

(D) Turbo boost feedback control. See paragraph (i)(6)of this section.

(E) Charge air undercooling. The OBD system must detect a malfunction of the 

charge air cooling system prior to a decrease from the manufacturer’s specified 

cooling rate that would cause an engine’s emissions to exceed the emissions 

thresholds for “other monitors” as shown in Table 1 of this paragraph (g). For 

engines in which no failure or deterioration of the charge air cooling system that 

causes a decrease in cooling performance could result in an engine’s emissions 

exceeding the applicable emissions thresholds, the OBD system must detect a 

malfunction when the system has no detectable amount of charge air cooling.

(iii) Turbo boost monitoring conditions.

(A) The OBD system must monitor continuously for malfunctions identified in 

paragraphs (g)(4)(ii)(A), (g)(4)(ii)(B), and (g)(4)(ii)(D) of this section.

(B) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraph (g)(4)(ii)(C) of this section in accordance with paragraphs 

(c) and (d) of this section, with the exception that monitoring must occur every 

time the monitoring conditions are met during the drive cycle rather than once per 

drive cycle as required in paragraph (c)(2) of this section. For purposes of 

tracking and reporting as required in paragraph (d)(1) of this section, all monitors 

used to detect malfunctions identified in paragraph (g)(4)(ii)(C) of this section 

must be tracked separately but reported as a single set of values as specified in 

paragraph (e)(1)(iii) of this section.

(C) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraph (g)(4)(ii)(E) of this section in accordance with paragraphs 

(c) and (d) of this section. For purposes of tracking and reporting as required in 

paragraph (d)(1) of this section, all monitors used to detect malfunctions 

identified in paragraph (g)(4)(ii)(E) of this section must be tracked separately but 

reported as a single set of values as specified in paragraph (e)(1)(iii) of this 

section.

(D) The manufacturer may request Administrator approval to disable temporarily 

the turbo boost system monitor(s) during specific operating conditions (e.g., 

transients, extreme low or high flow conditions). The manufacturer must be able 

to demonstrate via data or engineering analysis that a reliable system monitor 

cannot be run when these conditions exist because it cannot robustly distinguish 

between a malfunctioning system and a properly operating system. The 

manufacturer is still required to maintain comprehensive component monitoring 

as required in paragraph (i)(3) of this section.
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(iv) Turbo boost system MIL activation and DTC storage. The MIL must activate 

and DTCs must be stored according to the provisions of paragraph (b) of this 

section.

(5) NMHC converting catalyst monitoring

(i) General. The OBD system must monitor the NMHC converting catalyst(s) for 

proper NMHC conversion capability. For purposes of this paragraph (g)(5), each 

catalyst that converts NMHC must be monitored either individually or in 

combination with others. For purposes of this paragraph (g)(5), NMHC conversion 

that may occur over the DPF or other aftertreatment devices is not included.

(ii) NMHC converting catalyst malfunction criteria

(A) NMHC converting catalyst conversion efficiency. The OBD system must 

detect a malfunction when the catalyst has no detectable amount of NMHC 

conversion capability.

(B) NMHC converting catalyst aftertreatment assistance functions. For catalysts 

used to generate an exotherm to assist DPF regeneration, the OBD system must 

detect a malfunction when the catalyst is unable to generate a sufficient exotherm 

to achieve DPF regeneration. In meeting this requirement, the OBD system must 

detect a malfunction when the DOC is unable to generate a temperature rise of 

100 degrees C, or to reach the necessary DPF regeneration temperature, within 60 

seconds of initiating an active DPF regeneration. Further, the OBD system must 

detect a malfunction when the DOC is unable to sustain the necessary 

regeneration temperature for the duration of the regeneration event. The OBD or 

control system must abort the regeneration if the regeneration temperature has not 

been reached within five minutes of initiating an active regeneration event, or if 

the regeneration temperature cannot be sustained for the duration of the 

regeneration event. As an alternative to these specific malfunction criteria, the 

manufacturer may employ different criteria. To do so, the manufacturer must 

submit a description with supporting data, subject to Administrator approval, of 

their DPF regeneration monitoring strategy. The Administrator will consider the 

strategy’s equivalence to the specific criteria stated in this paragraph when 

considering the request. Also as an alternative to these specific malfunction 

criteria, the manufacturer may employ an OBD monitor that detects a catalyst 

malfunction when the catalyst conversion capability decreases to the point that 

NMHC emissions exceed 2.5 times the applicable NMHC emission standard but 

must adjust emission test results pursuant to paragraph (f)(2) of this section. For 

catalysts located downstream of a DPF and used to convert NMHC emissions 

during DPF regeneration, the OBD system must detect a malfunction when the 

catalyst has no detectable amount of NMHC conversion capability unless the 

manufacturer can demonstrate that deterioration or malfunction of the catalyst 

will not result in emissions that exceed the applicable NMHC standard.
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(iii) NMHC converting catalyst monitoring conditions. The manufacturer must 

define the monitoring conditions for malfunctions identified in paragraphs 

(g)(5)(ii)(A) and (g)(5)(ii)(B) of this section in accordance with paragraphs (c) and 

(d) of this section. For purposes of tracking and reporting as required in paragraph 

(d)(1) of this section, all monitors used to detect malfunctions identified in 

paragraphs (g)(5)(ii)(A) and (g)(5)(ii)(B) of this section must be tracked separately 

but reported as a single set of values as specified in paragraph (e)(1)(iii) of this 

section.

(iv) NMHC converting catalyst MIL activation and DTC storage. The MIL must 

activate and DTCs must be stored according to the provisions of paragraph (b) of 

this section. The monitoring method for the NMHC converting catalyst(s) must be 

capable of detecting all instances, except diagnostic self-clearing, when a catalyst 

DTC has been erased but the catalyst has not been replaced (e.g., catalyst overtemperature histogram approaches are not acceptable).

(6) Selective catalytic reduction (SCR) and lean NOx catalyst monitoring

(i) General. The OBD system must monitor the SCR and/or the lean NOx

converting catalyst(s) for proper conversion capability. For engines equipped with 

SCR systems or other catalyst systems that use an active/intrusive reductant 

injection (e.g., active lean NOx catalysts that use diesel fuel post-injection or inexhaust injection), the OBD system must monitor the active/intrusive reductant 

injection system for proper performance. The individual electronic components 

(e.g., actuators, valves, sensors, heaters, pumps) in the active/intrusive reductant 

injection system must be monitored in accordance with the comprehensive 

component requirements in paragraph (i)(3) of this section. For purposes of this 

paragraph (g)(6), each catalyst that converts NOx must be monitored either 

individually or in combination with others.

(ii) SCR and lean NOx catalyst malfunction criteria

(A) SCR and lean NOx catalyst conversion efficiency. The OBD system must 

detect a catalyst malfunction when the catalyst conversion capability decreases to 

the point that would cause an engine’s emissions to exceed the emissions 

thresholds for NOx aftertreatment systems as shown in Table 1 of this paragraph 

(g). If no failure or deterioration of the catalyst NOx conversion capability could 

result in an engine’s emissions exceeding any of the applicable emissions 

thresholds, the OBD system must detect a malfunction when the catalyst has no 

detectable amount of NOx conversion capability.

(B) SCR and lean NOx catalyst active/intrusive reductant delivery performance. 

The OBD system must detect a malfunction prior to any failure or deterioration of 

the system to properly regulate reductant delivery (e.g., urea injection, separate 

injector fuel injection, post injection of fuel, air assisted injection/mixing) that 

would cause an engine’s emissions to exceed any of the applicable emissions 

thresholds for NOx aftertreatment systems as shown in Table 1 of this paragraph 
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(g). If no failure or deterioration of the reductant delivery system could result in 

an engine’s emissions exceeding any of the applicable thresholds, the OBD 

system must detect a malfunction when the system has reached its control limits 

such that it is no longer able to deliver the desired quantity of reductant.

(C) SCR and lean NOx catalyst active/intrusive reductant quantity. If the SCR or 

lean NOx catalyst system uses a reductant other than the fuel used for the engine, 

or uses a reservoir/tank for the reductant that is separate from the fuel tank used 

for the engine, the OBD system must detect a malfunction when there is no longer 

sufficient reductant available (e.g., the reductant tank is empty).

(D) SCR and lean NOx catalyst active/intrusive reductant quality. If the SCR or 

lean NOx catalyst system uses a reservoir/tank for the reductant that is separate 

from the fuel tank used for the engine, the OBD system must detect a malfunction 

when an improper reductant is used in the reductant reservoir/tank (e.g., the 

reductant tank is filled with something other than the reductant).

(E) SCR and lean NOx catalyst active/intrusive reductant feedback control. See 

paragraph (i)(6) of this section.

(iii) SCR and lean NOx catalyst monitoring conditions.

(A) The manufacturers must define the monitoring conditions for malfunctions 

identified in paragraphs (g)(6)(ii)(A) and (g)(6)(ii)(D) of this section in 

accordance with paragraphs (c) and (d) of this section. For purposes of tracking 

and reporting as required in paragraph (d)(1) of this section, all monitors used to 

detect malfunctions identified in paragraph (g)(6)(ii)(A) of this section must be 

tracked separately but reported as a single set of values as specified in paragraph 

(e)(1)(iii) of this section.

(B) The OBD system must monitor continuously for malfunctions identified in 

paragraphs (g)(6)(ii)(B), (g)(6)(ii)(C), and (g)(6)(ii)(E) of this section.

(iv) SCR and lean NOx catalyst MIL activation and DTC storage.

(A) For malfunctions identified in paragraph (g)(6)(ii)(A) of this section, the MIL 

must activate and DTCs must be stored according to the provisions of paragraph 

(b) of this section.

(B) For malfunctions identified in paragraphs (g)(6)(ii)(B), (g)(6)(ii)(C), and 

(g)(6)(ii)(D) of this section, the manufacturer may delay activating the MIL if the 

vehicle is equipped with an alternative indicator for notifying the vehicle operator 

of the malfunction. The alternative indicator must be of sufficient illumination 

and be located such that it is readily visible to the vehicle operator under all 

lighting conditions. If the vehicle is not equipped with such an alternative 

indicator and the OBD MIL activates, the MIL may be immediately deactivated 

and the corresponding DTC(s) erased once the OBD system has verified that the 
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reductant tank has been refilled properly and the MIL has not been activated for 

any other malfunction. The Administrator may approve other strategies that 

provide equivalent assurance that a vehicle operator would be promptly notified 

and that corrective action would be taken.

(C) The monitoring method for the SCR and lean NOx catalyst(s) must be capable 

of detecting all instances, except diagnostic self-clearing, when a catalyst DTC(s) 

has been erased but the catalyst has not been replaced (e.g., catalyst overtemperature histogram approaches are not acceptable).

(7) NOx adsorber system monitoring

(i) General. The OBD system must monitor the NOx adsorber on engines soequipped for proper performance. For engines equipped with active/intrusive 

injection (e.g., in-exhaust fuel and/or air injection) to achieve desorption of the NOx

adsorber, the OBD system must monitor the active/intrusive injection system for 

proper performance. The individual electronic components (e.g., injectors, valves, 

sensors) that are used in the active/intrusive injection system must be monitored in 

accordance with the comprehensive component requirements in paragraph (i)(3) of 

this section.

(ii) NOx adsorber system malfunction criteria

(A) NOx adsorber system capability. The OBD system must detect a NOx

adsorber malfunction when its capability (i.e., its combined adsorption and 

conversion capability) decreases to the point that would cause an engine’s NOx

emissions to exceed the emissions thresholds for NOx aftertreatment systems as 

shown in Table 1 of this paragraph (g). If no failure or deterioration of the NOx

adsorber capability could result in an engine’s NOx emissions exceeding the 

applicable emissions thresholds, the OBD system must detect a malfunction when 

the system has no detectable amount of NOx adsorber capability.

(B) NOx adsorber system active/intrusive reductant delivery performance. For 

NOx adsorber systems that use active/intrusive injection (e.g., in-cylinder post 

fuel injection, in-exhaust air-assisted fuel injection) to achieve desorption of the 

NOx adsorber, the OBD system must detect a malfunction if any failure or 

deterioration of the injection system’s ability to properly regulate injection causes 

the system to be unable to achieve desorption of the NOx adsorber.

(C) NOx adsorber system feedback control. Malfunction criteria for the NOx

adsorber and the NOx adsorber active/instrusive reductant delivery system are 

contained in paragraph (i)(6) of this section.

(iii) NOx adsorber system monitoring conditions.

(A) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraph (g)(7)(ii)(A) of this section in accordance with paragraphs 
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(c) and (d) of this section. For purposes of tracking and reporting as required in 

paragraph (d)(1) of this section, all monitors used to detect malfunctions 

identified in paragraph (g)(7)(ii)(A) of this section must be tracked separately but 

reported as a single set of values as specified in paragraph (e)(1)(iii) of this 

section.

(B) The OBD system must monitor continuously for malfunctions identified in 

paragraphs (g)(7)(ii)(B) and (g)(7)(ii)(C) of this section.

(iv) NOx adsorber system MIL activation and DTC storage. The MIL must activate 

and DTCs must be stored according to the provisions of paragraph (b) of this 

section.

(8) Diesel particulate filter (DPF) system monitoring

(i) General. The OBD system must monitor the DPF on engines so-equipped for 

proper performance. For engines equipped with active regeneration systems that use 

an active/intrusive injection (e.g., in-exhaust fuel injection, in-exhaust fuel/air 

burner), the OBD system must monitor the active/intrusive injection system for 

proper performance. The individual electronic components (e.g., injectors, valves, 

sensors) that are used in the active/intrusive injection system must be monitored in 

accordance with the comprehensive component requirements in paragraph (i)(3) of 

this section.

(ii) DPF system malfunction criteria

(A) DPF filtering performance. The OBD system must detect a malfunction prior 

to a decrease in the PM filtering capability of the DPF (e.g., cracking, melting, 

etc.) that would cause an engine’s PM emissions to exceed the emissions 

thresholds for DPF systems as shown in Table 1 of this paragraph (g). If no failure 

or deterioration of the PM filtering performance could result in an engine’s PM 

emissions exceeding the applicable emissions thresholds, the OBD system must 

detect a malfunction when no detectable amount of PM filtering occurs. As an 

alternative to a threshold monitor, the OBD system, on model year 2010 through 

2012 engines only, can be designed to detect a malfunction based on a detectable 

decrease in the expected pressure drop across the DPF for a period of 5 seconds or 

more. The monitoring area for this alternative is determined using engine speed 

and load points defined in test cycles and procedures for the supplemental 

emissions test (SET) under § 86.1360-2007. The monitoring area shall include all 

engine speed and load points greater than a region bounded by a line connecting 

mode numbers 2, 6, 3, and 13 (i.e. A100, A75, B50, and C50). At engine speeds 

greater than “speed C”, the monitor shall run whenever engine load is greater than 

50%. For purposes of this paragraph, the detectable change in pressure drop is 

determined by operating the engine at the B50 engine speed and load point (as 

described in the SET test procedures), observing the pressure drop on a clean, 

nominal DPF, and multiplying the observed pressure drop by 0.5 or other factor 

supported by data and approved by the Administrator. The detectable change in 
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pressure drop shall be reported in units of kilopascals (kPa). At time of 

certification, manufacturers shall provide the detectable change in pressure drop 

value along with OBD data stream parameters recorded with a clean DPF under 

the following nine engine speed/load operating points of the SET: A50, A75, 

A100, B50, B75, B100, C50, C75, and C100. The OBD data stream pararmeters 

to be reported are described in (k)(4)(ii) of this section and shall include the 

following: Engine speed; calculated load; air flow rate from mass air flow sensor 

(if so equipped); fuel rate; and DPF delta pressure.

(B) DPF regeneration frequency. The OBD system must detect a malfunction 

when the DPF regeneration frequency increases from (i.e., occurs more often 

than) the manufacturer’s specified regeneration frequency to a level such that it 

would cause an engine’s NMHC emissions to exceed the emissions threshold for 

DPF systems as shown in Table 1 of this paragraph (g). If no such regeneration 

frequency exists that could cause NMHC emissions to exceed the applicable 

emission threshold, the OBD system must detect a malfunction when the DPF 

regeneration frequency exceeds the manufacturer’s specified design limits for 

allowable regeneration frequency.

(C) DPF incomplete regeneration. The OBD system must detect a regeneration 

malfunction when the DPF does not properly regenerate under manufacturerdefined conditions where regeneration is designed to occur.

(D) DPF missing substrate. The OBD system must detect a malfunction if either 

the DPF substrate is completely destroyed, removed, or missing, or if the DPF 

assembly has been replaced with a muffler or straight pipe.

(E) DPF system active/intrusive injection. For DPF systems that use 

active/intrusive injection (e.g., in-cylinder post fuel injection, in-exhaust airassisted fuel injection) to achieve regeneration of the DPF, the OBD system must 

detect a malfunction if any failure or deterioration of the injection system’s ability 

to properly regulate injection causes the system to be unable to achieve 

regeneration of the DPF.

(F) DPF regeneration feedback control. See paragraph (i)(6) of this section.

(iii) DPF monitoring conditions. The manufacturer must define the monitoring 

conditions for malfunctions identified in paragraph (g)(8)(ii) of this section in 

accordance with paragraphs (c) and (d) of this section, with the exception that 

monitoring must occur every time the monitoring conditions are met during the 

drive cycle rather than once per drive cycle as required in paragraph (c)(2) of this 

section. For OBD systems designed to the alternative malfunction criteria of 

paragraph (g)(8)(ii)(A) of this section, the alternative DPF monitor shall run 

continuously whenever engine speed and load conditions are within the monitoring 

area described in paragraph (g)(8)(ii)(A). The OBD system may make a 

malfunction or potential malfunction determination during any successful 

monitoring event but shall include in the enable criteria of any subsequent 
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monitoring events a confirmed successful and complete DPF regeneration. The 

subsequent monitoring events must be conducted within an operating period that 

ensures that the detected malfunction has not “healed” due to trapped particulates in 

the compromised portion of the DPF substrate. For purposes of tracking and 

reporting as required in paragraph (d)(1) of this section, all monitors used to detect 

malfunctions identified in paragraph (g)(8)(ii) of this section must be tracked 

separately but reported as a single set of values as specified in paragraph (e)(1)(iii) 

of this section.

(iv)DPF system MIL activation and DTC storage. The MIL must activate and DTCs 

must be stored according to the provisions of paragraph (b) of this section.

(9) Exhaust gas sensor and sensor heater monitoring

(i) General. The OBD system must monitor for proper output signal, activity, 

response rate, and any other parameter that can affect emissions, all exhaust gas 

sensors (e.g., oxygen, air-fuel ratio, NOx) used for emission control system 

feedback (e.g., EGR control/feedback, SCR control/feedback, NOx adsorber 

control/feedback) and/or as a monitoring device. For engines equipped with heated 

exhaust gas sensors, the OBD system must monitor the heater for proper 

performance.

(ii) Malfunction criteria for air-fuel ratio sensors located upstream of aftertreatment 

devices

(A) Sensor performance. The OBD system must detect a malfunction prior to any 

failure or deterioration of the sensor voltage, resistance, impedance, current, 

response rate, amplitude, offset, or other characteristic(s) that would cause an 

engine’s emissions to exceed the emissions thresholds for “other monitors” as 

shown in Table 1 of this paragraph (g).

(B) Circuit integrity. The OBD system must detect malfunctions of the sensor 

related to a lack of circuit continuity or signal out-of-range values.

(C) Feedback function. The OBD system must detect a malfunction of the sensor 

if the emission control system (e.g., EGR, SCR, or NOx adsorber) is unable to use 

that sensor as a feedback input (e.g., causes limp-home or open-loop operation).

(D) Monitoring function. To the extent feasible, the OBD system must detect a 

malfunction of the sensor when the sensor output voltage, resistance, impedance, 

current, amplitude, activity, offset, or other characteristics are no longer sufficient 

for use as an OBD system monitoring device (e.g., for catalyst, EGR, SCR, or 

NOx adsorber monitoring).

(iii) Malfunction criteria for air-fuel ratio sensors located downstream of 

aftertreatment devices
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(A) Sensor performance. The OBD system must detect a malfunction prior to any 

failure or deterioration of the sensor voltage, resistance, impedance, current, 

response rate, amplitude, offset, or other characteristic(s) that would cause an 

engine’s emissions to exceed the emissions thresholds for air-fuel ratio sensors 

downstream of aftertreatment devices as shown in Table 1 of this paragraph (g).

(B) Circuit integrity. The OBD system must detect malfunctions of the sensor 

related to a lack of circuit continuity or signal out-of-range values.

(C) Feedback function. The OBD system must detect a malfunction of the sensor 

if the emission control system (e.g., EGR, SCR, or NOx absorber) is unable to use 

that sensor as a feedback input (e.g., causes limp-home or open-loop operation).

(D) Monitoring function. To the extent feasible, the OBD system must detect a 

malfunction of the sensor when the sensor output voltage, resistance, impedance, 

current, amplitude, activity, offset, or other characteristics are no longer sufficient 

for use as an OBD system monitoring device (e.g., for catalyst, EGR, SCR, or 

NOx absorber monitoring).

(iv) Malfunction criteria for NOx sensors

(A) Sensor performance. The OBD system must detect a malfunction prior to any 

failure or deterioration of the sensor voltage, resistance, impedance, current, 

response rate, amplitude, offset, or other characteristic(s) that would cause an 

engine’s emissions to exceed the emissions thresholds for NOx sensors as shown 

in Table 1 of this paragraph (g).

(B) Circuit integrity. The OBD system must detect malfunctions of the sensor 

related to a lack of circuit continuity or signal out-of-range values.

(C) Feedback function. The OBD system must detect a malfunction of the sensor 

if the emission control system (e.g., EGR, SCR, or NOx adsorber) is unable to use 

that sensor as a feedback input (e.g., causes limp-home or open-loop operation).

(D) Monitoring function. To the extent feasible, the OBD system must detect a 

malfunction of the sensor when the sensor output voltage, resistance, impedance, 

current, amplitude, activity, offset, or other characteristics are no longer sufficient 

for use as an OBD system monitoring device (e.g., for catalyst, EGR, SCR, or 

NOx adsorber monitoring).

(v) Malfunction criteria for other exhaust gas sensors. For other exhaust gas 

sensors, the manufacturer must submit a monitoring plan to the Administrator for 

approval. The plan must include data and/or engineering evaluations that 

demonstrate that the monitoring plan is as reliable and effective as the monitoring 

required in paragraphs (g)(9)(ii), (g)(9)(iii), (g)(9)(iv) of this section.

(vi) Malfunction criteria for exhaust gas sensor heaters.
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(A) The OBD system must detect a malfunction of the heater performance when 

the current or voltage drop in the heater circuit is no longer within the 

manufacturer’s specified limits for normal operation (i.e., within the criteria

required to be met by the component vendor for heater circuit performance at high 

mileage). The manufacturer may use other malfunction criteria for heater 

performance malfunctions. To do so, the manufacturer must be able to 

demonstrate via data and/or an engineering evaluation that the monitor is reliable 

and robust.

(B) The OBD system must detect malfunctions of the heater circuit including 

open or short circuits that conflict with the commanded state of the heater (e.g., 

shorted to 12 Volts when commanded to 0 Volts (ground)).

(vii) Monitoring conditions for exhaust gas sensors.

(A) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraphs (g)(9)(ii)(A), (g)(9)(iii)(A), and (g)(9)(iv)(A) of this 

section (i.e., sensor performance) in accordance with paragraphs (c) and (d) of 

this section. For purposes of tracking and reporting as required in paragraph (d)(1) 

of this section, all monitors used to detect malfunctions identified in paragraphs 

(g)(9)(ii)(A), (g)(9)(iii)(A), and (g)(9)(iv)(A) of this section must be tracked 

separately but reported as a single set of values as specified in paragraph 

(e)(1)(iii) of this section.

(B) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraphs (g)(9)(ii)(D), (g)(9)(iii)(D), and (g)(9)(iv)(D) of this 

section (i.e., monitoring function) in accordance with paragraphs (c) and (d) of 

this section with the exception that monitoring must occur every time the 

monitoring conditions are met during the drive cycle rather than once per drive 

cycle as required in paragraph (c)(2) of this section.

(C) Except as provided for in paragraph (g)(9)(vii)(D) of this section, the OBD 

system must monitor continuously for malfunctions identified in paragraphs 

(g)(9)(ii)(B), (g)(9)(ii)(C), (g)(9)(iii)(B), (g)(9)(iii)(C), (g)(9)(iv)(B), (g)(9)(iv)(C) 

of this section (i.e., circuit integrity and feedback function).

(D) A manufacturer may request approval to disable continuous exhaust gas 

sensor monitoring when an exhaust gas sensor malfunction cannot be 

distinguished from other effects (e.g., disable monitoring for out-of-range on the 

low side during fuel cut conditions). To do so, the manufacturer must demonstrate 

via data and/or engineering analyses that a properly functioning sensor cannot be 

distinguished from a malfunctioning sensor and that the disablement interval is 

limited only to that necessary for avoiding false malfunction detection.

(viii) Monitoring conditions for exhaust gas sensor heaters
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(A) The manufacturer must define monitoring conditions for malfunctions 

identified in paragraph (g)(9)(vi)(A) of this section (i.e., sensor heater 

performance) in accordance with paragraphs (c) and (d) of this section.

(B) The OBD system must monitor continuously for malfunctions identified in 

paragraph (g)(9)(vi)(B) of this section (i.e., circuit malfunctions).

(ix) Exhaust gas sensor and sensor heater MIL activation and DTC storage. The 

MIL must activate and DTCs must be stored according to the provisions of 

paragraph (b) of this section.

(10) Variable Valve Timing (VVT) system monitoring

(i) General. The OBD system must monitor the VVT system on engines so 

equipped for target error and slow response malfunctions. The individual electronic 

components (e.g., actuators, valves, sensors) that are used in the VVT system must 

be monitored in accordance with the comprehensive components requirements in 

paragraph (i)(3) of this section.

(ii) VVT system malfunction criteria

(A) VVT system target error. The OBD system must detect a malfunction prior to 

any failure or deterioration in the capability of the VVT system to achieve the 

commanded valve timing and/or control within a crank angle and/or lift tolerance 

that would cause an engine’s emissions to exceed the emission thresholds for 

“other monitors” as shown in Table 1 of this paragraph (g).

(B) VVT slow response. The OBD system must detect a malfunction prior to any 

failure or deterioration in the capability of the VVT system to achieve the 

commanded valve timing and/or control within a manufacturer-specified time that 

would cause an engine’s emissions to exceed the emission thresholds for “other 

monitors” as shown in Table 1 of this paragraph (g).

(C) For engines in which no failure or deterioration of the VVT system could 

result in an engine’s emissions exceeding the applicable emissions thresholds of 

paragraphs (g)(10)(ii)(A) and (g)(10)(ii)(B) of this section, the OBD system must 

detect a malfunction of the VVT system when proper functional response of the 

system to computer commands does not occur.

(iii) VVT system monitoring conditions. Manufacturers must define the monitoring 

conditions for VVT system malfunctions identified in paragraph (g)(10)(ii) of this 

section in accordance with paragraphs (c) and (d) of this section, with the exception 

that monitoring must occur every time the monitoring conditions are met during the 

drive cycle rather than once per drive cycle as required in paragraph (c)(2) of this 

section. For purposes of tracking and reporting as required in paragraph (d)(1) of 

this section, all monitors used to detect malfunctions identified in paragraph 
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(g)(10)(ii) of this section must be tracked separately but reported as a single set of 

values as specified in paragraph (e)(1)(iii) of this section.

(iv) VVT MIL activation and DTC storage. The MIL must activate and DTCs must 

be stored according to the provisions of paragraph (b) of this section.

(h) OBD monitoring requirements for gasoline-fueled/spark-ignition engines. The 

following table shows the thresholds at which point certain components or systems, as 

specified in this paragraph (h), are considered malfunctioning.

(1) Fuel system monitoring

(i) General. The OBD system must monitor the fuel delivery system to determine its 

ability to provide compliance with emission standards.

(ii) Fuel system malfunction criteria.

(A) The OBD system must detect a malfunction of the fuel delivery system 

(including feedback control based on a secondary oxygen sensor) when the fuel 

delivery system is unable to maintain an engine’s emissions at or below the 

emissions thresholds for “other monitors” as shown in Table 2 of this paragraph 

(h).

Table 2 – OBD Emissions Thresholds for Gasoline-Fueled/Spark-Ignition Engines Meant 

for Placement in Applications Greater Than 14,000 Pounds GVWR (g/bhp-hr)

Notes: 1.75x std means a multiple of 1.75 times the applicable emissions standard; these emissions 

thresholds apply to the monitoring requirements of paragraph (h) of this section; The evaporative emissions 

control system threshold is not, technically, an emissions threshold but rather a leak size that must be 

detected; nonetheless, for ease we refer to this as the threshold.

 

(B) Except as provided for in paragraph (h)(1)(ii)(C) of this section, if the engine 

is equipped with adaptive feedback control, the OBD system must detect a 

malfunction when the adaptive feedback control has used up all of the adjustment 

allowed by the manufacturer.

(C) If the engine is equipped with feedback control that is based on a secondary 

oxygen (or equivalent) sensor, the OBD system is not required to detect a 

malfunction of the fuel system solely when the feedback control based on a 
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secondary oxygen sensor has used up all of the adjustment allowed by the 

manufacturer. However, if a failure or deterioration results in engine emissions 

that exceed the emissions thresholds for “other monitors” as shown in Table 2 of 

this paragraph (h), the OBD system is required to detect a malfunction.

(D) The OBD system must detect a malfunction whenever the fuel control system 

fails to enter closed loop operation following engine start within a manufacturer 

specified time interval. The specified time interval must be supported by data 

and/or engineering analyses submitted by the manufacturer.

(E) The manufacturer may adjust the malfunction criteria and/or monitoring 

conditions to compensate for changes in altitude, for temporary introduction of 

large amounts of purge vapor, or for other similar identifiable operating 

conditions when such conditions occur.

(iii) Fuel system monitoring conditions. The fuel system must be monitored 

continuously for the presence of a malfunction.

(iv) Fuel system MIL activation and DTC storage.

(A) A pending DTC must be stored immediately upon the fuel system exceeding

the malfunction criteria established in paragraph (h)(1)(ii) of this section.

(B) Except as provided for in paragraph (h)(1)(iv)(C) of this section, if a pending 

DTC is stored, the OBD system must activate the MIL immediately and store a 

MIL-on DTC if a malfunction is again detected during either the drive cycle 

immediately following storage of the pending DTC regardless of the conditions 

encountered during that drive cycle, or on the next drive cycle in which similar 

conditions are encountered to those that occurred when the pending DTC was 

stored. Similar conditions means engine conditions having an engine speed within 

375 rpm, load conditions within 20 percent, and the same warm-up status (i.e., 

cold or hot) as the engine conditions stored pursuant to paragraph (h)(1)(iv)(E) of 

this section. Other definitions of similar conditions may be used but must result in 

comparable timeliness and reliability in detecting similar engine operation.

(C) The pending DTC may be erased at the end of the next drive cycle in which 

similar conditions have been encountered without having again exceeded the 

specified fuel system malfunction criteria. The pending DTC may also be erased 

if similar conditions are not encountered during the 80 drive cycles immediately 

following detection of the potential malfunction for which the pending DTC was 

stored.

(D) Storage of freeze frame conditions. The OBD system must store and erase 

freeze frame conditions either in conjunction with storing and erasing a pending 

DTC or in conjunction with storing and erasing a MIL-on DTC. Freeze frame 

information associated with a fuel system malfunction shall be stored in 
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preference to freeze frame information required elsewhere in paragraphs (h) or (i) 

of this section.

(E) Storage of fuel system conditions for determining similar conditions of 

operation. The OBD must store the engine speed, load, and warm-up status 

present at the time it first detects a potential malfunction meeting the criteria of 

paragraph (h)(1)(ii) of this section and stores a pending DTC.

(F) Deactivating the MIL. The MIL may be extinguished after three sequential 

driving cycles in which similar conditions have been encountered without 

detecting a malfunction of the fuel system.

(2) Engine misfire monitoring

(i) General.

(A) The OBD system must monitor the engine for misfire causing catalyst 

damage and misfire causing excess emissions.

(B) The OBD system must identify the specific cylinder that is misfiring. The 

manufacturer may store a general misfire DTC instead of a cylinder specific DTC 

under certain operating conditions. To do so, the manufacturer must submit data 

and/or engineering analyses that demonstrate that the misfiring cylinder cannot be 

identified reliably when the conditions occur.

(C) If more than one cylinder is misfiring, a separate DTC must be stored to 

indicate that multiple cylinders are misfiring unless otherwise allowed by this 

paragraph (h)(2). When identifying multiple cylinder misfire, the OBD system is 

not required to also identify using separate DTCs each of the misfiring cylinders 

individually. If more than 90 percent of the detected misfires occur in a single 

cylinder, an appropriate DTC may be stored that indicates the specific misfiring 

cylinder rather than storing the multiple cylinder misfire DTC. If two or more 

cylinders individually have more than 10 percent of the total number of detected 

misfires, a multiple cylinder DTC must be stored.

(ii) Engine misfire malfunction criteria

(A) Misfire causing catalyst damage. The manufacturer must determine the 

percentage of misfire evaluated in 200 revolution increments for each engine 

speed and load condition that would result in a temperature that causes catalyst 

damage. If this percentage of misfire is exceeded, it shall be considered a 

malfunction that must be detected. For every engine speed and load condition for 

which this percentage of misfire is determined to be lower than five percent, the 

manufacturer may set the malfunction criteria at five percent. The manufacturer 

may use a longer interval than 200 revolutions but only for determining, on a 

given drive cycle, the first misfire exceedance as provided in paragraph 

(h)(2)(iv)(A) of this section. To do so, the manufacturer must demonstrate that the 
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interval is not so long that catalyst damage would occur prior to the interval being 

elapsed.

(B) Misfire causing emissions to exceed the applicable thresholds. The 

manufacturer must determine the percentage of misfire evaluated in 1000 

revolution increments that would cause emissions from an emissions durability 

demonstration engine to exceed the emissions thresholds for “other monitors” as 

shown in Table 2 of this paragraph (h) if that percentage of misfire were present 

from the beginning of the test. If this percentage of misfire is exceeded, regardless 

of the pattern of misfire events (e.g., random, equally spaced, continuous), it shall 

be considered a malfunction that must be detected. To establish this percentage of 

misfire, the manufacturer must use misfire events occurring at equally spaced, 

complete engine cycle intervals, across randomly selected cylinders throughout 

each 1000-revolution increment. If this percentage of misfire is determined to be 

lower than one percent, the manufacturer may set the malfunction criteria at one 

percent. The manufacturer may use a longer interval than 1000 revolutions. To do 

so, the manufacturer must demonstrate that the strategy would be equally 

effective and timely at detecting misfire.

(iii) Engine misfire monitoring conditions.

(A) The OBD system must monitor continuously for misfire under the following 

conditions: from no later than the end of the second crankshaft revolution after 

engine start; during the rise time and settling time for engine speed to reach the 

desired idle engine speed at engine start-up (i.e., “flare-up” and “flare-down”); 

and, under all positive torque engine speeds and load conditions except within the 

engine operating region bound by the positive torque line (i.e., engine load with 

the transmission in neutral), and the points represented by an engine speed of 

3000 rpm with the engine load at the positive torque line and the redline engine 

speed with the engine’s manifold vacuum at four inches of mercury lower than 

that at the positive torque line. For this purpose, redline engine speed is defined as 

either the recommended maximum engine speed as displayed on the instrument 

panel tachometer, or the engine speed at which fuel shutoff occurs.

(B) If an OBD monitor cannot detect all misfire patterns under all required engine 

speed and load conditions as required by paragraph (h)(2)(iii)(A) of this section, 

the OBD system may still be acceptable. The Administrator will evaluate the 

following factors in making a determination: The magnitude of the region(s) in 

which misfire detection is limited; the degree to which misfire detection is limited 

in the region(s) (i.e., the probability of detection of misfire events); the frequency 

with which said region(s) are expected to be encountered in-use; the type of 

misfire patterns for which misfire detection is troublesome; and demonstration 

that the monitoring technology employed is not inherently incapable of detecting 

misfire under the required conditions (i.e., compliance can be achieved on other 

engines). The evaluation will be based on the following misfire patterns: equally 

spaced misfire occurring on randomly selected cylinders; single cylinder 
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continuous misfire; and paired cylinder (cylinders firing at the same crank angle) 

continuous misfire.

(C) The manufacturer may use monitoring system that has reduced misfire 

detection capability during the portion of the first 1000 revolutions after engine 

start that a cold start emission reduction strategy is active that reduces engine 

torque (e.g., spark retard strategies). To do so, the manufacturer must demonstrate 

that the probability of detection is greater than or equal to 75 percent during the 

worst case condition (i.e., lowest generated torque) for a vehicle operated 

continuously at idle (park/neutral idle) on a cold start between 50 and 86 degrees 

Fahrenheit and that the technology cannot reliably detect a higher percentage of 

the misfire events during the conditions.

(D) The manufacturer may disable misfire monitoring or use an alternative 

malfunction criterion when misfire cannot be distinguished from other effects. To 

do so, the manufacturer must demonstrate that the disablement interval or the 

period of use of an alternative malfunction criterion is limited only to that 

necessary for avoiding false detection and for one or more of the following 

operating conditions: Rough road; fuel cut; gear changes for manual transmission 

vehicles; traction control or other vehicle stability control activation such as antilock braking or other engine torque modifications to enhance vehicle stability; 

off-board control or intrusive activation of vehicle components or monitors during 

service or assembly plant testing; portions of intrusive evaporative system or EGR 

monitors that can significantly affect engine stability (i.e., while the purge valve is 

open during the vacuum pull-down of an evaporative system leak check but not 

while the purge valve is closed and the evaporative system is sealed or while an 

EGR monitor causes the EGR valve to be cycled intrusively on and off during 

positive torque conditions); or, engine speed, load, or torque transients due to 

throttle movements more rapid than those that occur over the FTP cycle for the 

worst case engine within each engine family. In general, the Administrator will 

not approve disablement for conditions involving normal air conditioning 

compressor cycling from on-to-off or off-to-on, automatic transmission gear shifts 

(except for shifts occurring during wide open throttle operation), transitions from 

idle to off-idle, normal engine speed or load changes that occur during the engine 

speed rise time and settling time (i.e., “flare-up” and “flare-down”) immediately 

after engine starting without any vehicle operator-induced actions (e.g., throttle 

stabs), or excess acceleration (except for acceleration rates that exceed the 

maximum acceleration rate obtainable at wide open throttle while the vehicle is in 

gear due to abnormal conditions such as slipping of a clutch). The Administrator 

may approve misfire monitoring disablement or use of an alternate malfunction 

criterion for any other condition on a case by case basis upon determining that the 

manufacturer has demonstrated that the request is based on an unusual or 

unforeseen circumstance and that it is applying the best available computer and 

monitoring technology.

(E) For engines with more than eight cylinders that cannot meet the requirements 

of paragraph (h)(2)(iii)(A) of this section, a manufacturer may use alternative 
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misfire monitoring conditions. Such use must be based on data and/or an 

engineering evaluation submitted by the manufacturer that demonstrate that 

misfire detection throughout the required operating region cannot be achieved 

when employing proven monitoring technology (i.e., a technology that provides 

for compliance with these requirements on other engines) and provided misfire is 

detected to the fullest extent permitted by the technology. However, the misfire 

detection system must still monitor during all positive torque operating conditions 

encountered during an FTP cycle.

(iv) MIL activation and DTC storage for engine misfire causing catalyst damage

(A) Pending DTCs. A pending DTC must be stored immediately if, during a 

single drive cycle, the specified misfire percentage described in paragraph 

(h)(2)(ii)(A) of this section is exceeded three times when operating in the positive 

torque region encountered during a FTP cycle or is exceeded on a single occasion 

when operating at any other engine speed and load condition in the positive 

torque region defined in paragraph (h)(2)(iii)(A) of this section. Immediately after 

a pending DTC is stored pursuant to this paragraph, the MIL must blink once per 

second at all times during the drive cycle that engine misfire is occurring. The 

MIL may be deactivated during those times that misfire is not occurring. If, at the 

time that a catalyst damaging misfire malfunction occurs, the MIL is already 

activated for a malfunction other than misfire, the MIL must still blink once per 

second at all times during the drive cycle that engine misfire is occurring. If 

misfire ceases, the MIL must stop blinking but remain activated as appropriate in 

accordance with the other malfunction.

(B) MIL-on DTCs. If a pending DTC is stored in accordance with paragraph 

(h)(2)(iv)(A) of this section, the OBD system must immediately store a MIL-on 

DTC if the percentage of misfire described in paragraph (h)(2)(ii)(A) of this 

section is again exceeded one or more times during either the drive cycle 

immediately following storage of the pending DTC, regardless of the conditions 

encountered during that drive cycle, or on the next drive cycle in which similar 

conditions are encountered to those that occurred when the pending DTC was 

stored. If, during a previous drive cycle, a pending DTC is stored in accordance 

with paragraph (h)(2)(iv)(A) of this section, a MIL-on DTC must be stored 

immediately upon exceeding the percentage misfire described in paragraph 

(h)(2)(ii)(A) of this section regardless of the conditions encountered. Upon 

storage of a MIL-on DTC, the MIL must blink once per second at all times during 

the drive cycle that engine misfire is occurring. If misfire ceases, the MIL must 

stop blinking but remain activated until the conditions are met for extinguishing 

the MIL.

(C) Erasure of pending DTCs. Pending DTCs stored in accordance with paragraph 

(h)(2)(iv)(A) of this section must be erased at the end of the next drive cycle in 

which similar conditions are encountered to those that occurred when the pending 

DTC was stored provided no exceedances have been detected of the misfire 

percentage described in paragraph (h)(2)(ii)(A) of this section. The pending DTC 
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may also be erased if similar conditions are not encountered during the next 80 

drive cycles immediately following storage of the pending DTC.

(D) Exemptions for engines with fuel shutoff and default fuel control. In engines 

that provide for fuel shutoff and default fuel control to prevent over fueling during 

catalyst damaging misfire conditions, the MIL need not blink as required by 

paragraphs (h)(2)(iv)(A) and (h)(2)(iv)(B) of this section. Instead, the MIL may 

be activated continuously upon misfire detection provided that the fuel shutoff 

and default fuel control are activated immediately upon misfire detection. Fuel 

shutoff and default fuel control may be deactivated only when the engine is 

outside of the misfire range except that the manufacturer may periodically, but not 

more than once every 30 seconds, deactivate fuel shutoff and default fuel control 

to determine if the catalyst damaging misfire is still occurring. Normal fueling 

and fuel control may be resumed if the catalyst damaging misfire is no longer 

occurring.

(E) The manufacturer may use a strategy that activates the MIL continuously 

rather than blinking the MIL during extreme catalyst damage misfire conditions 

(i.e., catalyst damage misfire occurring at all engine speeds and loads). Use of 

such a strategy must be limited to catalyst damage misfire levels that cannot be 

avoided during reasonable driving conditions. To use such a strategy, the 

manufacturer must be able to demonstrate that the strategy will encourage 

operation of the vehicle in conditions that will minimize catalyst damage (e.g., at 

low engine speeds and loads).

(v) MIL activation and DTC storage for engine misfire causing emissions to exceed 

applicable emissions thresholds.

(A) Immediately upon detection, during the first 1000 revolutions after engine 

start of the misfire percentage described in paragraph (h)(2)(ii)(B) of this section, 

a pending DTC must be stored. If such a pending DTC is stored already and 

another such exceedance of the misfire percentage is detected within the first 

1000 revolutions after engine start on any subsequent drive cycle, the MIL must 

activate and a MIL-on DTC must be stored. The pending DTC may be erased if, 

at the end of the next drive cycle in which similar conditions are encountered to 

those that occurred when the pending DTC was stored, there has been no 

exceedance of the misfire percentage described in paragraph (h)(2)(ii)(B) of this 

section. The pending DTC may also be erased if similar conditions are not 

encountered during the next 80 drive cycles immediately following storage of the 

pending DTC.

(B) No later than the fourth detection during a single drive cycle, following the 

first 1000 revolutions after engine start of the misfire percentage described in 

paragraph (h)(2)(ii)(B) of this section, a pending DTC must be stored. If such a 

pending DTC is stored already, then the MIL must activate and a MIL-on DTC 

must be stored within 10 seconds of the fourth detection of the misfire percentage 

described in paragraph (h)(2)(ii)(B) of this section during either the drive cycle 
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immediately following storage of the pending DTC, regardless of the conditions 

encountered during that drive cycle excepting those conditions within the first 

1000 revolutions after engine start, or on the next drive cycle in which similar 

conditions are encountered to those that occurred when the pending DTC was 

stored excepting those conditions within the first 1000 revolutions after engine 

start. The pending DTC may be erased if, at the end of the next drive cycle in 

which similar conditions are encountered to those that occurred when the pending 

DTC was stored, there has been no exceedance of the misfire percentage 

described in paragraph (h)(2)(ii)(B) of this section. The pending DTC may also be 

erased if similar conditions are not encountered during the next 80 drive cycles 

immediately following storage of the pending DTC.

(vi) Storage of freeze frame conditions for engine misfire.

(A) The OBD system must store and erase freeze frame conditions (as defined in 

paragraph (k)(4)(iii) of this section) either in conjunction with storing and erasing 

a pending DTC or in conjunction with storing and erasing a MIL-on DTC.

(B) If, upon storage of a DTC as required by paragraphs (h)(2)(iv) and (h)(2)(v) 

of this section, there already exist stored freeze frame conditions for a 

malfunction other than a misfire or fuel system malfunction (see paragraph (h)(1) 

of this section) then the stored freeze frame information shall be replaced with 

freeze frame information associated with the misfire malfunction.

(vii) Storage of engine conditions in association with engine misfire. Upon 

detection of the misfire percentages described in paragraphs (h)(2)(ii)(A) and 

(h)(2)(ii)(B) of this section, the following engine conditions must be stored for use 

in determining similar conditions: Engine speed, load, and warm up status of the 

first misfire event that resulted in pending DTC storage.

(viii) MIL deactivation in association with engine misfire. The MIL may be 

deactivated after three sequential drive cycles in which similar conditions have been 

encountered without an exceedance of the misfire percentages described in 

paragraphs (h)(2)(ii)(A) and (h)(2)(ii)(B) of this section.

(3) Exhaust gas recirculation system monitoring

(i) General. The OBD system must monitor the EGR system on engines so 

equipped for low and high flow rate malfunctions. The individual electronic 

components (e.g., actuators, valves, sensors) that are used in the EGR system must 

be monitored in accordance with the comprehensive component requirements in 

paragraph (i)(3) of this section.

(ii) EGR system malfunction criteria.

(A) The OBD system must detect a malfunction of the EGR system prior to a 

decrease from the manufacturer’s specified EGR flow rate that would cause an 
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engine’s emissions to exceed the emissions thresholds for “other monitors” as 

shown in Table 2 of this paragraph (h). For engines in which no failure or 

deterioration of the EGR system that causes a decrease in flow could result in an 

engine’s emissions exceeding the applicable emissions thresholds, the OBD 

system must detect a malfunction when the system has no detectable amount of 

EGR flow.

(B) The OBD system must detect a malfunction of the EGR system prior to an 

increase from the manufacturer’s specified EGR flow rate that would cause an 

engine’s emissions to exceed the emissions thresholds for “other monitors” as 

shown in Table 2 of this paragraph (h). For engines in which no failure or 

deterioration of the EGR system that causes an increase in flow could result in an 

engine’s emissions exceeding the applicable emissions thresholds, the OBD 

system must detect a malfunction when the system has reached its control limits 

such that it cannot reduce EGR flow.

(iii) EGR system monitoring conditions.

(A) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraph (h)(3)(ii) of this section in accordance with paragraphs (c) 

and (d) of this section. For purposes of tracking and reporting as required by 

paragraph (d)(1) of this section, all monitors used to detect malfunctions 

identified in paragraph (h)(3)(ii) of this section must be tracked separately but 

reported as a single set of values as specified in paragraph (e)(1)(iii) of this 

section.

(B) The manufacturer may disable temporarily the EGR monitor under conditions 

when monitoring may not be reliable (e.g., when freezing may affect performance 

of the system). To do so, the manufacturer must be able to demonstrate that the 

monitor is unreliable when such conditions exist.

(iv) EGR system MIL activation and DTC storage. The MIL must activate and 

DTCs must be stored according to the provisions of paragraph (b) of this section.

(4) Cold start emission reduction strategy monitoring

(i) General. If an engine incorporates a specific engine control strategy to reduce 

cold start emissions, the OBD system must monitor the key components (e.g., idle 

air control valve), other than secondary air, while the control strategy is active to 

ensure proper operation of the control strategy.

(ii) Cold start strategy malfunction criteria.

(A) The OBD system must detect a malfunction prior to any failure or 

deterioration of the individual components associated with the cold start emission 

reduction control strategy that would cause an engine’s emissions to exceed the 

emissions thresholds for “other monitors” as shown in Table 2 of this paragraph 
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(h). The manufacturer must establish the malfunction criteria based on data from 

one or more representative engine(s) and provide an engineering evaluation for 

establishing the malfunction criteria for the remainder of the manufacturer’s 

product line.

(B) Where no failure or deterioration of a component used for the cold start 

emission reduction strategy could result in an engine’s emissions exceeding the 

applicable emissions thresholds, the individual component must be monitored for 

proper functional response while the control strategy is active in accordance with 

the malfunction criteria in paragraphs (i)(3)(ii) and (i)(3)(iii) of this section.

(iii) Cold start strategy monitoring conditions. The manufacturer must define 

monitoring conditions for malfunctions identified in paragraph (h)(4)(ii) of this 

section in accordance with paragraphs (c) and (d) of this section.

(iv) Cold start strategy MIL activation and DTC storage. The MIL must activate 

and DTCs must be stored according to the provisions of paragraph (b) of this 

section.

(5) Secondary air system monitoring

(i) General. The OBD system on engines equipped with any form of secondary air 

delivery system must monitor the proper functioning of the secondary air delivery 

system including all air switching valve(s). The individual electronic components 

(e.g., actuators, valves, sensors) that are used in the secondary air system must be 

monitored in accordance with the comprehensive component requirements in 

paragraph (i)(3) of this section. For purposes of this paragraph (h)(5), “air flow” is 

defined as the air flow delivered by the secondary air system to the exhaust system. 

For engines using secondary air systems with multiple air flow paths/distribution 

points, the air flow to each bank (i.e., a group of cylinders that share a common 

exhaust manifold, catalyst, and control sensor) must be monitored in accordance 

with the malfunction criteria in paragraph (h)(5)(ii) of this section. Also for 

purposes of this paragraph (h)(5), “normal operation” is defined as the condition 

when the secondary air system is activated during catalyst and/or engine warm-up 

following engine start. “Normal operation” does not include the condition when the 

secondary air system is turned on intrusively for the sole purpose of monitoring.

(ii) Secondary air system malfunction criteria.

(A) Except as provided in paragraph (h)(5)(ii)(C) of this section, the OBD system 

must detect a secondary air system malfunction prior to a decrease from the 

manufacturer’s specified air flow during normal operation that would cause an 

engine’s emissions to exceed the emissions thresholds for “other monitors” as 

shown in Table 2 of this paragraph (h).

(B) Except as provided in paragraph (h)(5)(ii)(C) of this section, the OBD system 

must detect a secondary air system malfunction prior to an increase from the 
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manufacturer’s specified air flow during normal operation that would cause an 

engine’s emissions to exceed the emissions thresholds for “other monitors” as 

shown in Table 2 of this paragraph (h).

(C) For engines in which no deterioration or failure of the secondary air system 

would result in an engine’s emissions exceeding the applicable emissions 

thresholds, the OBD system must detect a malfunction when no detectable 

amount of air flow is delivered by the secondary air system during normal 

operation.

 

(iii) Secondary air system monitoring conditions. The manufacturer must define 

monitoring conditions for malfunctions identified in paragraph (h)(5)(ii) of this 

section in accordance with paragraphs (c) and (d) of this section. For purposes of 

tracking and reporting as required by paragraph (d)(1) of this section, all monitors 

used to detect malfunctions identified in paragraph (h)(5)(ii) of this section must be 

tracked separately but reported as a single set of values as specified in paragraph 

(e)(1)(iii) of this section.

(iv) Secondary air system MIL activation and DTC storage. The MIL must activate 

and DTCs must be stored according to the provisions of paragraph (b) of this 

section.

(6) Catalyst system monitoring

(i) General. The OBD system must monitor the catalyst system for proper 

conversion capability.

(ii) Catalyst system malfunction criteria. The OBD system must detect a catalyst 

system malfunction when the catalyst system’s conversion capability decreases to 

the point that emissions exceed the emissions thresholds for the catalyst system as 

shown in Table 2 of this paragraph (h).

(iii) Catalyst system monitoring conditions. The manufacturer must define 

monitoring conditions for malfunctions identified in paragraph (h)(6)(ii) of this 

section in accordance with paragraphs (c) and (d) of this section. For purposes of 

tracking and reporting as required by paragraph (d)(1) of this section, all monitors 

used to detect malfunctions identified in paragraph (h)(6)(ii) of this section must be 

tracked separately but reported as a single set of values as specified in paragraph 

(e)(1)(iii) of this section.

(iv) Catalyst system MIL activation and DTC storage.

(A) The MIL must activate and DTCs must be stored according to the provisions 

of paragraph (b) of this section.

(B) The monitoring method for the catalyst system must be capable of detecting 

when a catalyst DTC has been erased (except OBD system self erasure), but the 
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catalyst has not been replaced (e.g., catalyst overtemperature histogram 

approaches are not acceptable).

(7) Evaporative system monitoring

(i) General. The OBD system must verify purge flow from the evaporative system 

and monitor the complete evaporative system, excluding the tubing and connections 

between the purge valve and the intake manifold, for vapor leaks to the atmosphere. 

Individual components of the evaporative system (e.g. valves, sensors) must be 

monitored in accordance with the comprehensive components requirements in 

paragraph (i)(3) of this section.

(ii) Evaporative system malfunction criteria

(A) Purge monitor. The OBD system must detect an evaporative system 

malfunction when no purge flow from the evaporative system to the engine can be 

detected by the OBD system.

(B) Leak monitor. The OBD system must detect an evaporative system 

malfunction when the complete evaporative system contains a leak or leaks that 

cumulatively are greater than or equal to a leak caused by a 0.150 inch diameter 

hole.

(C) The manufacturer may demonstrate that detection of a larger hole is more 

appropriate than that specified in paragraph (h)(7)(ii)(B) of this section. To do so, 

the manufacturer must demonstrate through data and/or engineering analyses that 

holes smaller than the proposed detection size would not result in evaporative or 

running loss emissions that exceed 1.5 times the applicable evaporative emissions 

standards. Upon such a demonstration, the proposed detection size could be 

substituted for the requirement of paragraph (h)(7)(ii)(B) of this section.

(iii) Evaporative system monitoring conditions.

(A) The manufacturer must define monitoring conditions for malfunctions 

identified in paragraph (h)(7)(ii)(A) of this section in accordance with paragraphs 

(c) and (d) of this section.

(B) The manufacturer must define monitoring conditions for malfunctions 

identified in paragraph (h)(7)(ii)(B) of this section in accordance with paragraphs 

(c) and (d) of this section. For purposes of tracking and reporting as required by 

paragraph (d)(1) of this section, all monitors used to detect malfunctions 

identified in paragraph (h)(7)(ii)(B) of this section must be tracked separately but 

reported as a single set of values as specified in paragraph (e)(1)(iii) of this 

section.
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(C) The manufacturer may disable or abort an evaporative system monitor when 

the fuel tank level is over 85 percent of nominal tank capacity or during a 

refueling event.

(D) The manufacturer may request Administrator approval to run the evaporative 

system monitor during only those drive cycles characterized as cold starts 

provided such a condition is needed to ensure reliable monitoring. In making the 

request, the manufacturer must demonstrate through data and/or engineering 

analyses that a reliable monitor can only be run on drive cycles that begin with a 

specific set of cold start criteria. A set of cold start criteria based solely on 

ambient temperature exceeding engine coolant temperature will not be acceptable.

(E) The OBD system may disable temporarily the evaporative purge system to run 

an evaporative system leak monitor.

(iv) Evaporative system MIL activation and DTC storage.

(A) Except as provided for in paragraph (h)(7)(iv)(B) of this section, the MIL 

must activate and DTCs must be stored according to the provisions of paragraph 

(b) of this section.

(B) If the OBD system is capable of discerning that a system leak is being caused 

by a missing or improperly secured gas cap, the OBD system need not activate the 

MIL or store a DTC provided the vehicle is equipped with an alternative indicator 

for notifying the operator of the gas cap problem. The alternative indicator must 

be of sufficient illumination and location to be readily visible under all lighting 

conditions. If the vehicle is not equipped with such an alternative indicator, the 

MIL must activate and a DTC be stored as required in paragraph (h)(7)(iv)(A) of 

this section; however, these may be deactivated and erased, respectively, if the 

OBD system determines that the gas cap problem has been corrected and the MIL 

has not been activated for any other malfunction. The Administrator may approve

other strategies that provide equivalent assurance that a vehicle operator will be 

notified promptly of a missing or improperly secured gas cap and that corrective 

action will be undertaken.

(8) Exhaust gas sensor monitoring

(i) General.

(A) The OBD system must monitor for malfunctions the output signal, response 

rate, and any other parameter that can affect emissions of all primary (i.e., fuel 

control) exhaust gas sensors (e.g., oxygen, wide-range air/fuel). Both the lean-torich and rich-to-lean response rates must be monitored.

(B) The OBD system must also monitor all secondary exhaust gas sensors (those 

used for secondary fuel trim control or as a monitoring device) for proper output 

signal, activity, and response rate.
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(C) For engines equipped with heated exhaust gas sensor, the OBD system must 

monitor the heater for proper performance.

(ii) Primary exhaust gas sensor malfunction criteria.

(A) The OBD system must detect a malfunction prior to any failure or 

deterioration of the exhaust gas sensor output voltage, resistance, impedance, 

current, response rate, amplitude, offset, or other characteristic(s) (including drift 

or bias corrected for by secondary sensors) that would cause an engine’s 

emissions to exceed the emissions thresholds for “other monitors” as shown in 

Table 2 of this paragraph (h).

(B) The OBD system must detect malfunctions of the exhaust gas sensor caused 

by either a lack of circuit continuity or out-of-range values.

(C) The OBD system must detect a malfunction of the exhaust gas sensor when a 

sensor failure or deterioration causes the fuel system to stop using that sensor as a 

feedback input (e.g., causes default or open-loop operation).

(D) The OBD system must detect a malfunction of the exhaust gas sensor when 

the sensor output voltage, resistance, impedance, current, amplitude, activity, or 

other characteristics are no longer sufficient for use as an OBD system monitoring 

device (e.g., for catalyst monitoring).

(iii) Secondary exhaust gas sensor malfunction criteria.

(A) The OBD system must detect a malfunction prior to any failure or 

deterioration of the exhaust gas sensor voltage, resistance, impedance, current, 

response rate, amplitude, offset, or other characteristic(s) that would cause an 

engine’s emissions to exceed the emissions thresholds for “other monitors” as 

shown in Table 2 of this paragraph (h).

(B) The OBD system must detect malfunctions of the exhaust gas sensor caused 

by a lack of circuit continuity.

(C) To the extent feasible, the OBD system must detect a malfunction of the 

exhaust gas sensor when the sensor output voltage, resistance, impedance, current, 

amplitude, activity, offset, or other characteristics are no longer sufficient for use 

as an OBD system monitoring device (e.g., for catalyst monitoring).

(D) The OBD system must detect malfunctions of the exhaust gas sensor caused 

by out-of-range values.

(E) The OBD system must detect a malfunction of the exhaust gas sensor when a 

sensor failure or deterioration causes the fuel system (e.g., fuel control) to stop 

using that sensor as a feedback input (e.g., causes default or open-loop operation).
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(iv) Exhaust gas sensor heater malfunction criteria.

(A) The OBD system must detect a malfunction of the heater performance when 

the current or voltage drop in the heater circuit is no longer within the 

manufacturer’s specified limits for normal operation (i.e., within the criteria 

required to be met by the component vendor for heater circuit performance at high 

mileage). Other malfunction criteria for heater performance malfunctions may be 

used upon demonstrating via data or engineering analyses that the monitoring 

reliability and timeliness is equivalent to the stated criteria in this paragraph 

(h)(8)(iv)(A).

(B) The OBD system must detect malfunctions of the heater circuit including 

open or short circuits that conflict with the commanded state of the heater (e.g., 

shorted to 12 Volts when commanded to 0 Volts (ground)).

(v) Primary exhaust gas sensor monitoring conditions.

(A) The manufacturer must define monitoring conditions for malfunctions 

identified in paragraphs (h)(8)(ii)(A) and (h)(8)(ii)(D) of this section in 

accordance with paragraphs (c) and (d) of this section. For purposes of tracking 

and reporting as required by paragraph (d)(1) of this section, all monitors used to 

detect malfunctions identified in paragraphs (h)(8)(ii)(A) and (h)(8)(ii)(D) of this 

section must be tracked separately but reported as a single set of values as 

specified in paragraph (e)(1)(iii) of this section.

(B) Except as provided for in paragraph (h)(8)(v)(C) of this section, monitoring 

for malfunctions identified in paragraphs (h)(8)(ii)(B) and (h)(8)(ii)(C) of this 

section must be conducted continuously.

(C) The manufacturer may disable continuous primary exhaust gas sensor

monitoring when a primary exhaust gas sensor malfunction cannot be 

distinguished from other effects (e.g., disable out-of-range low monitoring during 

fuel cut conditions). To do so, the manufacturer must demonstrate via data or 

engineering analyses that a properly functioning sensor cannot be distinguished 

from a malfunctioning sensor and that the disablement interval is limited only to 

that necessary for avoiding false detection.

(vi) Secondary exhaust gas sensor monitoring conditions.

(A) The manufacturer must define monitoring conditions for malfunctions 

identified in paragraphs (h)(8)(iii)(A) through (h)(8)(iii)(C) of this section in 

accordance with paragraphs (c) and (d) of this section.

(B) Except as provided for in paragraph (h)(8)(vi)(C) of this section, monitoring 

for malfunctions identified in paragraphs (h)(8)(iii)(D) and (h)(8)(iii)(E) of this 

section must be conducted continuously.
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(C) The manufacturer may disable continuous secondary exhaust gas sensor 

monitoring when a secondary exhaust gas sensor malfunction cannot be 

distinguished from other effects (e.g., disable out-of-range low monitoring during 

fuel cut conditions). To do so, the manufacturer must demonstrate via data or 

engineering analyses that a properly functioning sensor cannot be distinguished 

from a malfunctioning sensor and that the disablement interval is limited only to 

that necessary for avoiding false detection.

(vii) Exhaust gas sensor heater monitoring conditions.

(A) The manufacturer must define monitoring conditions for malfunctions 

identified in paragraph (h)(8)(iv)(A) of this section in accordance with paragraphs 

(c) and (d) of this section.

(B) Monitoring for malfunctions identified in paragraph (h)(8)(iv)(B) of this 

section must be conducted continuously.

(viii) Exhaust gas sensor MIL activation and DTC storage. The MIL must activate 

and DTCs must be stored according to the provisions of paragraph (b) of this 

section.

(9) Variable valve timing (VVT) system monitoring\

(i) General. The OBD system must monitor the VVT system on engines so 

equipped for target error and slow response malfunctions. The individual electronic 

components (e.g., actuators, valves, sensors) that are used in the VVT system must 

be monitored in accordance with the comprehensive components requirements in 

paragraph (i)(3).

(ii) VVT system malfunction criteria

(A) VVT system target error. The OBD system must detect a malfunction prior to 

any failure or deterioration in the capability of the VVT system to achieve the 

commanded valve timing and/or control within a crank angle and/or lift tolerance 

that would cause an engine’s emissions to exceed the emission thresholds for 

“other monitors” as shown in Table 2 of this paragraph (h).

(B) VVT slow response. The OBD system must detect a malfunction prior to any 

failure or deterioration in the capability of the VVT system to achieve the 

commanded valve timing and/or control within a manufacturer-specified time that 

would cause an engine’s emissions to exceed the emission thresholds for “other 

monitors” as shown in Table 2 of this paragraph (h).

(C) For engines in which no failure or deterioration of the VVT system could 

result in an engine’s emissions exceeding the applicable emissions thresholds of 

paragraphs (h)(9)(ii)(A) and (h)(9)(ii)(B) of this section, the OBD system must 
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detect a malfunction of the VVT system when proper functional response of the 

system to computer commands does not occur.

(iii) VVT system monitoring conditions. Manufacturers must define the monitoring 

conditions for VVT system malfunctions identified in paragraph (h)(9)(ii) in 

accordance with paragraphs (c) and (d) of this section, with the exception that 

monitoring must occur every time the monitoring conditions are met during the 

drive cycle rather than once per drive cycle as required in paragraph (c)(2) of this 

section. For purposes of tracking and reporting as required in paragraph (d)(1) of 

this section, all monitors used to detect malfunctions identified in paragraph 

(h)(9)(ii) must be tracked separately but reported as a single set of values as 

specified in paragraph (e)(1)(iii) of this section.

(iv) VVT MIL activation and DTC storage. The MIL must activate and DTCs must 

be stored according to the provisions of paragraph (b) of this section.

(i) OBD monitoring requirements for all engines

(1) Engine cooling system monitoring

(i) General.

(A) The OBD system must monitor the thermostat on engines so equipped for 

proper operation.

(B) The OBD system must monitor the engine coolant temperature (ECT) sensor 

for electrical circuit continuity, out-of-range values, and rationality malfunctions.

(C) For engines that use a system other than the cooling system and ECT sensor 

(e.g., oil temperature, cylinder head temperature) to determine engine operating 

temperature for emission control purposes (e.g., to modify spark or fuel injection 

timing or quantity), the manufacturer may forego cooling system monitoring and 

instead monitor the components or systems used in their approach. To do so, the 

manufacturer must to submit data and/or engineering analyses that demonstrate 

that their monitoring plan is as reliable and effective as the monitoring required in 

this paragraph (i)(1).

(ii) Malfunction criteria for the thermostat.

(A) The OBD system must detect a thermostat malfunction if, within the 

manufacturer specified time interval following engine start, any of the following 

conditions occur: The coolant temperature does not reach the highest temperature 

required by the OBD system to enable other diagnostics; and, the coolant 

temperature does not reach a warmed-up temperature within 20 degrees 

Fahrenheit of the manufacturer’s nominal thermostat regulating temperature. For 

the second of these two conditions, the manufacturer may use a lower temperature 

for this criterion if either the manufacturer can demonstrate that the fuel, spark 
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timing, and/or other coolant temperature-based modification to the engine control 

strategies would not cause an emissions increase greater than or equal to 50 

percent of any of the applicable emissions standards; or, ambient air temperature 

is between 20 degrees Fahrenheit and 50 degrees Fahrenheit in which case, upon 

Administrator approval, the minimum coolant temperature required to be reached 

may be decreased based on the ambient air temperature.

(B) With Administrator approval, the manufacturer may use alternative 

malfunction criteria to those of paragraph (i)(1)(ii)(A) of this section and/or 

alternative monitoring conditions to those of paragraph (i)(1)(iv) of this section 

that are a function of temperature at engine start on engines that do not reach the 

temperatures specified in the malfunction criteria when the thermostat is 

functioning properly. To do so, the manufacturer is required to submit data and/or 

engineering analyses that demonstrate that a properly operating system does not 

reach the specified temperatures and that the possibility is minimized for cooling 

system malfunctions to go undetected thus disabling other OBD monitors.

(C) The manufacturer may request Administrator approval to forego monitoring 

of the thermostat if the manufacturer can demonstrate that a malfunctioning 

thermostat cannot cause a measurable increase in emissions during any reasonable 

driving condition nor cause any disablement of other OBD monitors.

(iii) Malfunction criteria for the ECT sensor

(A) Circuit integrity. The OBD system must detect malfunctions of the ECT 

sensor related to a lack of circuit continuity or out-of-range values.

(B) Time to reach closed-loop/feedback enable temperature. The OBD system 

must detect if, within the manufacturer specified time interval following engine 

start, the ECT sensor does not achieve the highest stabilized minimum 

temperature that is needed to initiate closed-loop/feedback control of all affected 

emission control systems (e.g., fuel system, EGR system). The manufacturer 

specified time interval must be a function of the engine coolant temperature 

and/or intake air temperature at startup. The manufacturer time interval must be 

supported by data and/or engineering analyses demonstrating that it provides 

robust monitoring and minimizes the likelihood of other OBD monitors being 

disabled. The manufacturer may forego the requirements of this paragraph 

(i)(1)(iii)(B) provided the manufacturer does not use engine coolant temperature 

or the ECT sensor to enable closed-loop/feedback control of any emission control 

systems.

(C) Stuck in range below the highest minimum enable temperature. To the extent 

feasible when using all available information, the OBD system must detect a 

malfunction if the ECT sensor inappropriately indicates a temperature below the 

highest minimum enable temperature required by the OBD system to enable other 

monitors (e.g., an OBD system that requires ECT to be greater than 140 degrees 

Fahrenheit to enable a diagnostic must detect malfunctions that cause the ECT 
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sensor to inappropriately indicate a temperature below 140 degrees Fahrenheit). 

The manufacturer may forego this requirement for temperature regions in which 

the monitors required under paragraphs (i)(1)(ii) or (i)(1)(iii)(B) of this section 

will detect ECT sensor malfunctions as defined in this paragraph (i)(1)(iii)(C).

(D) Stuck in range above the lowest maximum enable temperature. The OBD 

system must detect a malfunction if the ECT sensor inappropriately indicates a 

temperature above the lowest maximum enable temperature required by the OBD 

system to enable other monitors (e.g., an OBD system that requires an engine 

coolant temperature less than 90 degrees Fahrenheit at startup prior to enabling an 

OBD monitor must detect malfunctions that cause the ECT sensor to indicate 

inappropriately a temperature above 90 degrees Fahrenheit). The manufacturer 

may forego this requirement within temperature regions in which the monitors 

required under paragraphs (i)(1)(ii), (i)(1)(iii)(B), (i)(1)(iii)(C) of this section will 

detect ECT sensor malfunctions as defined in this paragraph (i)(1)(iii)(D) or in 

which the MIL will be activated according to the provisions of paragraph 

(b)(2)(v) of this section. The manufacturer may also forego this monitoring within 

temperature regions where a temperature gauge on the instrument panel indicates 

a temperature in the “red zone” (engine overheating zone) and displays the same 

temperature information as used by the OBD system.

(iv) Monitoring conditions for the thermostat.

(A) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraph (i)(1)(ii)(A) of this section in accordance with paragraph 

(c) of this section. Additionally, except as provided for in paragraphs (i)(1)(iv)(B) 

and (i)(1)(iv)(C) of this section, monitoring for malfunctions identified in 

paragraph (i)(1)(ii)(A) of this section must be conducted once per drive cycle on 

every drive cycle in which the ECT sensor indicates, at engine start, a temperature 

lower than the temperature established as the malfunction criteria in paragraph 

(i)(1)(ii)(A) of this section.

(B) The manufacturer may disable thermostat monitoring at ambient engine start 

temperatures below 20 degrees Fahrenheit.

(C) The manufacturers may request Administrator approval to suspend or disable 

thermostat monitoring if the engine is subjected to conditions that could lead to 

false diagnosis. To do so, the manufacturer must submit data and/or engineering 

analyses that demonstrate that the suspension or disablement is necessary. In 

general, the manufacturer will not be allowed to suspend or disable the thermostat 

monitor on engine starts where the engine coolant temperature at engine start is 

more than 35 degrees Fahrenheit lower than the thermostat malfunction threshold 

temperature determined under paragraph (i)(1)(ii)(A) of this section.

(v) Monitoring conditions for the ECT sensor.
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(A) Except as provided for in paragraph (i)(1)(v)(D) of this section, the OBD 

system must monitor continuously for malfunctions identified in paragraph 

monitoring for malfunctions identified in paragraph (i)(1)(iii)(A) of this section 

(i.e., circuit integrity and out-of-range).

(B) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraph (i)(1)(iii)(B) of this section in accordance with paragraph 

(c) of this section. Additionally, except as provided for in paragraph (i)(1)(v)(D) 

of this section, monitoring for malfunctions identified in paragraph (i)(1)(iii)(B) 

of this section must be conducted once per drive cycle on every drive cycle in 

which the ECT sensor indicates a temperature lower than the closed-loop enable 

temperature at engine start (i.e., all engine start temperatures greater than the ECT 

sensor out-of-range low temperature and less than the closed-loop enable 

temperature).

(C) The manufacturer must define the monitoring conditions for malfunctions 

identified in paragraphs (i)(1)(iii)(C) and (i)(1)(iii)(D) of this section in 

accordance with paragraphs (c) and (d) of this section.

(D) The manufacturer may suspend or delay the monitor for the time to reach 

closed-loop enable temperature if the engine is subjected to conditions that could 

lead to false diagnosis (e.g., vehicle operation at idle for more than 50 to 75 

percent of the warm-up time).

(E) The manufacturer may request Administrator approval to disable continuous 

ECT sensor monitoring when an ECT sensor malfunction cannot be distinguished 

from other effects. To do so, the manufacturer must submit data and/or 

engineering analyses that demonstrate a properly functioning sensor cannot be 

distinguished from a malfunctioning sensor and that the disablement interval is 

limited only to that necessary for avoiding false detection.

(vi) Engine cooling system MIL activation and DTC storage. The MIL must 

activate and DTCs must be stored according to the provisions of paragraph (b) of 

this section.

(2) Crankcase ventilation (CV) system monitoring

(i) General. The OBD system must monitor the CV system on engines so equipped 

for system integrity. Engines not required to be equipped with CV systems are 

exempt from monitoring the CV system. For diesel engines, the manufacturer must 

submit a plan for Administrator approval prior to OBD certification. That plan must 

include descriptions of the monitoring strategy, malfunction criteria, and monitoring 

conditions for CV system monitoring. The plan must demonstrate that the CV 

system monitor is of equivalent effectiveness, to the extent feasible, to the 

malfunction criteria and the monitoring conditions of this paragraph (i)(2).

(ii) Crankcase ventilation system malfunction criteria.
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(A) For the purposes of this paragraph (i)(2), “CV system” is defined as any form 

of crankcase ventilation system, regardless of whether it utilizes positive pressure. 

“CV valve” is defined as any form of valve or orifice used to restrict or control 

crankcase vapor flow. Further, any additional external CV system tubing or hoses 

used to equalize crankcase pressure or to provide a ventilation path between 

various areas of the engine (e.g., crankcase and valve cover) are considered part 

of the CV system “between the crankcase and the CV valve” and subject to the 

malfunction criteria in paragraph (i)(2)(ii)(B) of this section.

(B) Except as provided for in paragraphs (i)(2)(ii)(C) through (i)(2)(ii)(E) of this 

section, the OBD system must detect a malfunction of the CV system when a 

disconnection of the system occurs between either the crankcase and the CV 

valve, or between the CV valve and the intake manifold.

(C) The manufacturer may forego monitoring for a disconnection between the 

crankcase and the CV valve provided the CV system is designed such that the CV 

valve is fastened directly to the crankcase such that it is significantly more 

difficult to remove the CV valve from the crankcase than to disconnect the line 

between the CV valve and the intake manifold (taking aging effects into 

consideration). To do so, the manufacturer must be able to provide data and/or an 

engineering evaluation demonstrating that the CV system is so designed.

(D) The manufacturer may forego monitoring for a disconnection between the 

crankcase and the CV valve provided the CV system is designed such that it uses 

tubing connections between the CV valve and the crankcase that are: resistant to 

deterioration or accidental disconnection; significantly more difficult to 

disconnect than is the line between the CV valve and the intake manifold; and, not 

subject to disconnection per the manufacturer’s repair procedures for any non-CV 

system repair. To do so, the manufacturer must be able to provide data and/or 

engineering evaluation demonstrating that the CV system is so designed.

(E) The manufacturer may forego monitoring for a disconnection between the CV 

valve and the intake manifold provided the CV system is designed such that any 

disconnection either causes the engine to stall immediately during idle operation, 

or is unlikely to occur due to a CV system design that is integral to the induction 

system (e.g., machined passages rather than tubing or hoses). To do so, the 

manufacturer must be able to provide data and/or an engineering evaluation 

demonstrating that the CV system is so designed.

(iii) Crankcase ventilation system monitoring conditions. The manufacturer must 

define the monitoring conditions for malfunctions identified in paragraph (i)(2) of 

this section in accordance with paragraphs (c) and (d) of this section.

(iv) Crankcase ventilation system MIL activation and DTC storage. The MIL must 

activate and DTCs must be stored according to the provisions of paragraph (b) of 

this section. The stored DTC need not identify specifically the CV system (e.g., a 
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DTC for idle speed control or fuel system monitoring can be stored) if the 

manufacturer can demonstrate that additional monitoring hardware is necessary to 

make such an identification and provided the manufacturer’s diagnostic and repair 

procedures for the 

detected malfunction include directions to check the integrity of the CV system.

(3) Comprehensive component monitoring

(i) General. Except as provided for in paragraph (i)(4) of this section, the OBD 

system must detect a malfunction of any electronic engine component or system not 

otherwise described in paragraphs (g), (h), (i)(1), and (i)(2) of this section that 

either provides input to (directly or indirectly, such components may include the 

crank angle sensor, knock sensor, throttle position sensor, cam position sensor, 

intake air temperature sensor, boost pressure sensor, manifold pressure sensor, mass

air flow sensor, exhaust temperature sensor, exhaust pressure sensor, fuel pressure 

sensor, fuel composition sensor of a flexible fuel vehicle, etc.) or receives 

commands from (such components or systems may include the idle speed control 

system, glow plug system, variable length intake manifold runner systems, 

supercharger or turbocharger electronic components, heated fuel preparation 

systems, the wait-to-start lamp on diesel applications, the MIL, etc.) the onboard 

computer(s) and meets either of the criteria described in paragraphs (i)(3)(i)(A) 

and/or (i)(3)(i)(B) of this section. Note that, for the purposes of this paragraph 

(i)(3), “electronic engine component or system” does not include components that 

are driven by the engine and are not related to the control of the fueling, air 

handling, or emissions of the engine (e.g., PTO components, air conditioning 

system components, and power steering components).

(A) It can cause emissions to exceed applicable emission standards. To preclude 

monitoring, the manufacturer must be able to provide emission data showing that 

the component or system, when malfunctioning and installed on a suitable test 

engine, does not cause emissions to exceed the emission standards.

(B) It is used as part of the monitoring strategy for any other monitored system or 

component.

(ii) Comprehensive component malfunction criteria for input components.

(A) The OBD system must detect malfunctions of input components caused by a 

lack of circuit continuity and out-of-range values. In addition, where feasible, 

rationality checks must also be done and shall verify that a sensor output is neither 

inappropriately high nor inappropriately low (i.e., “two-sided” monitoring).

(B) To the extent feasible, the OBD system must separately detect and store 

different DTCs that distinguish rationality malfunctions from lack of circuit 

continuity and out-of-range malfunctions. For lack of circuit continuity and outof-range malfunctions, the OBD system must, to the extent feasible, separately 

detect and store different DTCs for each distinct malfunction (e.g., out-of-range 
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low, out-of-range high, open circuit). The OBD system is not required to store 

separate DTCs for lack of circuit continuity malfunctions that cannot be 

distinguished from other out-of-range circuit malfunctions.

(C) For input components that are used to activate alternative strategies that can 

affect emissions (e.g., AECDs, engine shutdown systems), the OBD system must 

conduct rationality checks to detect malfunctions that cause the system to activate 

erroneously or deactivate the alternative strategy. To the extent feasible when 

using all available information, the rationality check must detect a malfunction if 

the input component inappropriately indicates a value that activates or deactivates 

the alternative strategy. For example, for an alternative strategy that activates 

when the intake air temperature is greater than 120 degrees Fahrenheit, the OBD 

system must detect malfunctions that cause the intake air temperature sensor to 

indicate inappropriately a temperature above 120 degrees Fahrenheit.

(D) For engines that require precise alignment between the camshaft and the 

crankshaft, the OBD system must monitor the crankshaft position sensor(s) and 

camshaft position sensor(s) to verify proper alignment between the camshaft and 

crankshaft in addition to monitoring the sensors for circuit continuity and proper 

rationality. Proper alignment monitoring between a camshaft and a crankshaft is 

required only in cases where both are equipped with position sensors. For engines 

equipped with VVT systems and a timing belt or chain, the OBD system must 

detect a malfunction if the alignment between the camshaft and crankshaft is off 

by one or more cam/crank sprocket cogs (e.g., the timing belt/chain has slipped by 

one or more teeth/cogs). If a manufacturer demonstrates that a single tooth/cog 

misalignment cannot cause a measurable increase in emissions during any 

reasonable driving condition, the OBD system must detect a malfunction when 

the minimum number of teeth/cogs misalignment has occurred that does cause a 

measurable emission increase.

(iii) Comprehensive component malfunction criteria for output 

components/systems.

(A) The OBD system must detect a malfunction of an output component/system 

when proper functional response does not occur in response to computer 

commands. If such a functional check is not feasible, the OBD system must detect 

malfunctions of output components/systems caused by a lack of circuit continuity 

or circuit malfunction (e.g., short to ground or high voltage). For output 

component lack of circuit continuity malfunctions and circuit malfunctions, the 

OBD system is not required to store different DTCs for each distinct malfunction 

(e.g., open circuit, shorted low). Manufacturers are not required to activate an 

output component/system when it would not normally be active for the sole 

purpose of performing a functional check of it as required in this paragraph (i)(3).

(B) For gasoline engines, the idle control system must be monitored for proper 

functional response to computer commands. For gasoline engines using 

monitoring strategies based on deviation from target idle speed, a malfunction 
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must be detected when either of the following conditions occurs: The idle speed 

control system cannot achieve the target idle speed within 200 revolutions per 

minute (rpm) above the target speed or 100 rpm below the target speed; or, the 

idle speed control system cannot achieve the target idle speed within the smallest 

engine speed tolerance range required by the OBD system to enable any other 

monitors. Regarding the former of these conditions, the manufacturer may use 

larger engine speed tolerances. To do so, the manufacturer must be able to 

provide data and/or engineering analyses that demonstrate that the tolerances can 

be exceeded without a malfunction being present.

(C) For diesel engines, the idle control system must be monitored for proper 

functional response to computer commands. For diesel engines, a malfunction 

must be detected when either of the following conditions occurs: the idle fuel 

control system cannot achieve the target idle speed or fuel injection quantity 

within ±50 percent of the manufacturer-specified fuel quantity and engine speed 

tolerances; or, the idle fuel control system cannot achieve the target idle speed or 

fueling quantity within the smallest engine speed or fueling quantity tolerance 

range required by the OBD system to enable any other monitors.

(D) For model years 2010 through 2012, glow plugs must be monitored for circuit 

continuity malfunctions. For model years 2010 and later, intake air heater systems 

and, for model years 2013 and later, glow plugs must be monitored for proper 

functional response to computer commands and for circuit continuity 

malfunctions. The glow plug/intake air heater circuit(s) must be monitored for 

proper current and voltage drop. The manufacturer may use other monitoring 

strategies but must be able to provide data and/or engineering analyses that 

demonstrate reliable and timely detection of malfunctions. The OBD system must 

also detect a malfunction when a single glow plug no longer operates within the 

manufacturer’s specified limits for normal operation. If a manufacturer can 

demonstrate that a single glow plug malfunction cannot cause a measurable 

increase in emissions during any reasonable driving condition, the OBD system 

must instead detect a malfunction when the number of glow plugs needed to cause 

an emission increase is malfunctioning. To the extent feasible, the stored DTC 

must identify the specific malfunctioning glow plug(s).

(E) The wait-to-start lamp circuit and the MIL circuit must be monitored for 

malfunctions that cause either lamp to fail to activate when commanded to do so 

(e.g., burned out bulb). This monitoring of the wait-to-start lamp circuit and the 

MIL circuit is not required for wait-to-start lamps and MILs using light-emitting 

diodes (LEDs).

(iv) Monitoring conditions for input components.

(A) The OBD system must monitor input components continuously for out-ofrange values and circuit continuity. The manufacturer may disable continuous 

monitoring for circuit continuity and out-of-range values when a malfunction 

cannot be distinguished from other effects. To do so, the manufacturer must be 
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able to provide data and/or engineering analyses that demonstrate that a properly 

functioning input component cannot be distinguished from a malfunctioning input 

component and that the disablement interval is limited only to that necessary for 

avoiding false malfunction detection.

(B) For input component rationality checks (where applicable), the manufacturer 

must define the monitoring conditions for detecting malfunctions in accordance 

with paragraphs (c) and (d) of this section, with the exception that rationality 

checks must occur every time the monitoring conditions are met during the drive 

cycle rather than once per drive cycle as required in paragraph (c)(2) of this 

section.

(v) Monitoring conditions for output components/systems.

(A) The OBD system must monitor output components/systems continuously for 

circuit continuity and circuit malfunctions. The manufacturer may disable 

continuous monitoring for circuit continuity and circuit malfunctions when a 

malfunction cannot be distinguished from other effects. To do so, the 

manufacturer must be able to provide data and/or engineering analyses that 

demonstrate that a properly functioning output component/system cannot be 

distinguished from a malfunctioning one and that the disablement interval is 

limited only to that necessary for avoiding false malfunction detection.

(B) For output component/system functional checks, the manufacturer must 

define the monitoring conditions for detecting malfunctions in accordance with 

paragraphs (c) and (d) of this section. Specifically for the idle control system, the 

manufacturer must define the monitoring conditions for detecting malfunctions in 

accordance with paragraphs (c) and (d) of this section, with the exception that 

functional checks must occur every time the monitoring conditions are met during 

the drive cycle rather than once per drive cycle as required in paragraph (c)(2) of 

this section.

(vi) Comprehensive component MIL activation and DTC storage.

(A) Except as provided for in paragraphs (i)(3)(vi)(B) and (i)(3)(vi)(C) of this 

section, the MIL must activate and DTCs must be stored according to the 

provisions of paragraph (b) of this section.

(B) The MIL need not be activated in conjunction with storing a MIL-on DTC for 

any comprehensive component if: the component or system, when 

malfunctioning, could not cause engine emissions to increase by 15 percent or 

more of the applicable FTP standard during any reasonable driving condition; or, 

the component or system is not used as part of the monitoring strategy for any 

other system or component that is required to be monitored.

(C) The MIL need not be activated if a malfunction has been detected in the MIL 

circuit that prevents the MIL from activating (e.g., burned out bulb or light-
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emitting diode, LED). Nonetheless, the electronic MIL status (see paragraph 

(k)(4)(ii) of this section) must be reported as MIL commanded-on and a MIL-on 

DTC must be stored.

(4) Other emission control system monitoring

(i) General. For other emission control systems that are either not addressed in 

paragraphs (g) through (i)(3) of this section (e.g., hydrocarbon traps, homogeneous 

charge compression ignition control systems), or addressed in paragraph (i)(3) of 

this section but not corrected or compensated for by an adaptive control system 

(e.g., swirl control valves), the manufacturer must submit a plan for Administrator 

approval of the monitoring strategy, malfunction criteria, and monitoring conditions 

prior to introduction on a production engine. The plan must demonstrate the 

effectiveness of the monitoring strategy, the malfunction criteria used, the 

monitoring conditions required by the monitor, and, if applicable, the determination 

that the requirements of paragraph (i)(4)(ii) of this section are satisfied.

(ii) For engines that use emission control systems that alter intake air flow or 

cylinder charge characteristics by actuating valve(s), flap(s), etc., in the intake air 

delivery system (e.g., swirl control valve systems), the manufacturer, in addition to 

meeting the requirements of paragraph (i)(4)(i) of this section, may elect to have the 

OBD system monitor the shaft to which all valves in one intake bank are physically 

attached rather than performing a functional check of the intake air flow, cylinder 

charge, or individual valve(s)/flap(s). For non-metal shafts or segmented shafts, the 

monitor must verify all shaft segments for proper functional response (e.g., by 

verifying that the segment or portion of the shaft farthest from the actuator 

functions properly). For systems that have more than one shaft to operate valves in 

multiple intake banks, the manufacturer is not required to add more than one set of 

detection hardware (e.g., sensor, switch) per intake bank to meet this requirement.

This section is intended to exempt engine monitoring systems from having 

to monitor hybrid powertrain systems from the 2013 through the 2019 

model-years as the issues needed to accomplish such monitoring in the 

non-vertically integrated market for vehicles with GVWR > 14,000 lbs are 

addressed by engine and hybrid system manufacturers as well as 

regulatory agencies and industry groups (e.g. SAE).

(iii) For the 2013 through the 2019 model-year, engines used with hybrid 

powertrain systems as defined in 86.010-02 are not required to monitor the hybrid 

powertrain system or components of the hybrid powertrain system.

This section is intended to ensure that EPA is provided with information 

on hybrid powertrain system diagnostic capabilities during the 2013 

through 2019 model-years without creating a significant new reporting 

responsibility for hybrid powertrain system manufacturers. It also 

requires that hybrid powertrain system manufacturers provide EPA with 

annual updates of the progress being made to integrate systems 
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diagnostics with the comprehensive monitoring and standardization 

requirements that apply to engine monitoring systems as well as in 

achieving integration with the monitoring systems of 2020 and later 

model-year engines with which they will be used. It also clarifies that the 

OBD “certification process” applies to engines not hybrid powertrain 

systems. 

 

(iv) A hybrid powertrain system manufacturer, as defined in 86.010-02, whose 

systems are used with 2013 through 2019 model-year engines must provide 

technical description of the system’s fault detection and diagnostic capabilities to 

the Administrator. The Administrator will accept this information in the form 

provided by the manufacturer. In addition, manufacturers of hybrid powertrain 

systems must provide an annual report to the Administrator describing the 

manufacturer’s product plans, activities, and progress toward achieving integration 

of their hybrid powertrain systems such that 2020 and later-model-year engine

monitoring systems comply with the requirements of paragraph (i)(3) of this 

section. 

(5) Exceptions to OBD monitoring requirements.

(i) The Administrator may revise the PM filtering performance malfunction criteria 

for DPFs to exclude detection of specific failure modes such as partially melted 

substrates, if the most reliable monitoring method developed requires it.

(ii) The manufacturer may disable an OBD system monitor at ambient engine start 

temperatures below 20 degrees Fahrenheit (low ambient temperature conditions 

may be determined based on intake air or engine coolant temperature at engine 

start) or at elevations higher than 8,000 feet above sea level. To do so, the 

manufacturer must submit data and/or engineering analyses that demonstrate that 

monitoring is unreliable during the disable conditions. A manufacturer may request 

that an OBD system monitor be disabled at other ambient engine start temperatures 

by submitting data and/or engineering analyses demonstrating that misdiagnosis 

would occur at the given ambient temperatures due to their effect on the component 

itself (e.g., component freezing).

(iii) The manufacturer may disable an OBD system monitor when the fuel level is 

15 percent or less of the nominal fuel tank capacity for those monitors that can be 

affected by low fuel level or running out of fuel (e.g., misfire detection). To do so, 

the manufacturer must submit data and/or engineering analyses that demonstrate 

that monitoring at the given fuel levels is unreliable, and that the OBD system is 

still able to detect a malfunction if the component(s) used to determine fuel level 

indicates erroneously a fuel level that causes the disablement.

(iv) The manufacturer may disable OBD monitors that can be affected by engine 

battery or system voltage levels.
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(A) For an OBD monitor affected by low vehicle battery or system voltages, 

manufacturers may disable monitoring when the battery or system voltage is 

below 11.0 Volts. The manufacturer may use a voltage threshold higher than 11.0 

Volts to disable monitors but must submit data and/or engineering analyses that 

demonstrate that monitoring at those voltages is unreliable and that either 

operation of a vehicle below the disablement criteria for extended periods of time 

is unlikely or the OBD system monitors the battery or system voltage and will 

detect a malfunction at the voltage used to disable other monitors.

(B) For an OBD monitor affected by high engine battery or system voltages, the 

manufacturer may disable monitoring when the battery or system voltage exceeds 

a manufacturer-defined voltage. To do so, the manufacturer must submit data 

and/or engineering analyses that demonstrate that monitoring above the 

manufacturer-defined voltage is unreliable and that either the electrical charging 

system/alternator warning light will be activated (or voltage gauge would be in 

the “red zone”) or the OBD system monitors the battery or system voltage and 

will detect a malfunction at the voltage used to disable other monitors.

(v) The manufacturer may also disable affected OBD monitors in systems designed 

to accommodate the installation of power take off (PTO) units provided monitors 

are disabled only while the PTO unit is active and the OBD readiness status (see 

paragraph (k)(4)(i) of this section) is cleared by the onboard computer (i.e., all 

monitors set to indicate “not complete” or “not ready”) while the PTO unit is 

activated. If monitors are so disabled and when the disablement ends, the readiness 

status may be restored to its state prior to PTO activation.

(6) Feedback control system monitoring. If the engine is equipped with feedback 

control of any of the systems covered in paragraphs (g), (h) and (i) of this section, 

then the OBD system must detect as malfunctions the conditions specified in this 

paragraph (i)(6) for each of the individual feedback controls.

(i) The OBD system must detect when the system fails to begin feedback control 

within a manufacturer specified time interval.

(ii) When any malfunction or deterioration causes open loop or limp-home 

operation.

(iii) When feedback control has used up all of the adjustment allowed by the 

manufacturer.

(iv) A manufacturer may temporarily disable monitoring for malfunctions specified 

in paragraph (i)(6)(iii) of this section during conditions that the specific monitor 

cannot distinguish robustly between a malfunctioning system and a properly 

operating system. To do so, the manufacturer is required to submit data and/or 

engineering analyses demonstrating that the individual feedback control system, 

when operating as designed on an engine with all emission controls working 

properly, routinely operates during these conditions while having used up all of the 
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adjustment allowed by the manufacturer. In lieu of detecting, with a system specific 

monitor, the malfunctions specified in paragraphs (i)(6)(i) and (i)(6)(ii) of this 

section the OBD system may monitor the individual parameters or components that 

are used as inputs for individual feedback control systems provided that the 

monitors detect all malfunctions that meet the criteria of paragraphs (i)(6)(i) and 

(i)(6)(ii) of this section.

(j) Production evaluation testing

(1) Verification of standardization requirements.

(i) For model years 2013 and later, the manufacturer must perform testing to verify 

that production vehicles meet the requirements of paragraphs (k)(3) and (k)(4) of 

this section relevant to the proper communication of required emissions-related 

messages to a SAE J1978 or SAE J1939 (both as specified in paragraph (k)(1) of 

this section) scan tool.

(ii) Selection of test vehicles.

(A) The manufacturer must perform this testing every model year on ten unique 

production vehicles (i.e., engine rating and chassis application combination) per 

engine family. If there are less than ten unique production vehicles for a certain 

engine family, the manufacturer must test each unique production vehicle in that 

engine family. The manufacturer must perform this testing within either three 

months of the start of engine production or one month of the start of vehicle 

production, whichever is later. The manufacturer may request approval to group 

multiple production vehicles together and test one representative vehicle per 

group. To do so, the software and hardware designed to comply with the 

standardization requirements of paragraph (k)(1) of this section (e.g., 

communication protocol message timing, number of supported data stream 

parameters, engine and vehicle communication network architecture) in the 

representative vehicle must be identical to all others in the group and any 

differences in the production vehicles cannot be relevant with respect to meeting 

the criteria of paragraph (j)(1)(iv) of this section.

(B) For 2016 and subsequent model years, the required number of vehicles to be 

tested shall be reduced to five per engine family provided zero vehicles fail the 

testing required by paragraph (j)(1) of this section for two consecutive years.

(C) For 2019 and subsequent model years, the required number of vehicles to be 

tested shall be reduced to three per engine family provided zero vehicles fail the 

testing required by paragraph (j)(1) of this section for three consecutive years.

(D) The requirement for submittal of data from one or more of the production 

vehicles shall be waived if data have been submitted previously for all of the 

production vehicles. The manufacturer may request approval to carry over data 

collected in previous model years. To do so, the software and hardware designed 
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to comply with the standardization requirements of paragraph (k)(1) of this 

section must be identical to the previous model year and there must not have been 

other hardware or software changes that affect compliance with the 

standardization requirements.

 

(iii) Test equipment. For the testing required by paragraph (j)(1) of this section, the 

manufacturer shall use an off-board device to conduct the testing. The manufacturer 

must be able to show that the off-board device is able to verify that the vehicles 

tested using the device are able to perform all of the required functions in paragraph 

(j)(1)(iv) of this section with any other off-board device designed and built in 

accordance with the SAE J1978 or SAE J1939 (both as specified in paragraph 

(k)(1) of this section) generic scan tool specifications.

(iv) Required testing. The testing must verify that communication can be 

established properly between all emission-related on-board computers and a SAE 

J1978 or SAE J1939 (both as specified in paragraph (k)(1) of this section) scan tool 

designed to adhere strictly to the communication protocols allowed in paragraph 

(k)(3) of this section. The testing must also verify that all emission-related 

information is communicated properly between all emission-related on-board 

computers and a SAE J1978 or SAE J1939 (both as specified in paragraph (k)(1) of 

this section) scan tool in accordance with the requirements of paragraph (k)(1) of 

this section and the applicable ISO and SAE specifications including specifications 

for physical layer, network layer, message structure, and message content. The 

testing must also verify that the onboard computer(s) can properly respond to a SAE 

J1978 or SAE J1939 (both as specified in paragraph (k)(1) of this section) scan tool 

request to clear emissions-related DTCs and reset the ready status in accordance 

with paragraph (k)(4)(ix) of this section. The testing must further verify that the 

following information can be properly communicated to a SAE J1978 or SAE 

J1939 (both as specified in paragraph (k)(1) of this section) scan tool:

(A) The current ready status from all onboard computers required to support ready 

status in accordance with SAE J1978 or SAE J1939-73 (both as specified in 

paragraph (k)(1) of this section) and paragraph (k)(4)(i) of this section in the keyon, engine-off position and while the engine is running.

(B) The MIL command status while a deactivated MIL is commanded and while 

an activated MIL is commanded in accordance with SAE J1979 or SAE J1939 

(both as specified in paragraph (k)(1) of this section) and paragraph (k)(4)(ii) of 

this section in the key-on, engine-off position and while the engine is running, and 

in accordance with SAE J1979 or SAE J1939 (both as specified in paragraph 

(k)(1) of this section) and paragraphs (b)(1)(ii) of this section during the MIL 

functional check, if applicable, and, if applicable, (k)(4)(i)(C) of this section 

during the MIL ready status check while the engine is off.

(C) All data stream parameters required in paragraph (k)(4)(ii) of this section in 

accordance with SAE J1979 or SAE J1939 (both as specified in paragraph (k)(1) 
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of this section) including, if applicable, the proper identification of each data 

stream parameter as supported in SAE J1979 (e.g., Mode/Service $01, PID $00).

(D) The CAL ID, CVN, and VIN as required by paragraphs (k)(4)(vi), (k)(4)(vii), 

and (k)(4)(viii) of this section and in accordance with SAE J1979 or SAE J1939 

(both as specified in paragraph (k)(1) of this section).

(E) An emissions-related DTC (permanent, pending, MIL-on, previous-MIL-on) 

in accordance with SAE J1979 or SAE J1939-73 (both as specified in paragraph 

(k)(1) of this section) including the correct indication of the number of stored 

DTCs (e.g., Mode/Service $01, PID $01, Data A for SAE J1979 (as specified in 

paragraph (k)(1) of this section)) and paragraph (k)(4)(iv) of this section.

(v) Reporting of results. The manufacturer must submit to the Administrator the 

following, based on the results of the testing required by paragraph (j)(1)(iv) of this 

section:

(A) If a variant meets all the requirements of paragraph (j)(1)(iv) of this section, a 

statement specifying that the variant passed all the tests. Upon request from the 

Administrator, the detailed results of any such testing may have to be submitted.

(B) If any variant does not meet the requirements paragraph (j)(1)(iv) of this 

section, a written report detailing the problem(s) identified and the manufacturer’s 

proposed corrective action (if any) to remedy the problem(s). This report must be 

submitted within one month of testing the specific variant. The Administrator will 

consider the proposed remedy and, if in disagreement, will work with the 

manufacturer to propose an alternative remedy. Factors to be considered by the 

Administrator in considering the proposed remedy will include the severity of the 

problem(s), the ability of service technicians to access the required diagnostic 

information, the impact on equipment and tool manufacturers, and the amount of 

time prior to implementation of the proposed corrective action.

(vi) Alternative testing protocols. Manufacturers may request approval to use other 

testing protocols. To do so, the manufacturer must demonstrate that the alternative 

testing methods and equipment will provide an equivalent level of verification of 

compliance with the standardization requirements as is required by paragraph (j)(1) 

of this section.

(2) Verification of monitoring requirements.

(i) Within either the first six months of the start of engine production or the first 

three months of the start of vehicle production, whichever is later, the manufacturer 

must conduct a complete evaluation of the OBD system of one or more production 

vehicles (test vehicles) and submit the results of the evaluation to the Administrator.

(ii) Selection of test vehicles.
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(A) For each engine selected for monitoring system demonstration in paragraph 

(l) of this section, the manufacturer must evaluate one production vehicle 

equipped with an engine from the same engine family and rating as the 

demonstration engine. The vehicle selection must be approved by the 

Administrator.

(B) If the manufacturer is required to test more than one test vehicle, the 

manufacturer may test an engine in lieu of a vehicle for all but one of the required 

test vehicles.

(C) The requirement for submittal of data from one or more of the test vehicles 

may be waived if data have been submitted previously for all of the engine ratings 

and variants.

(iii) Evaluation requirements.

(A) The evaluation must demonstrate the ability of the OBD system on the 

selected test vehicle to detect a malfunction, activate the MIL, and, where 

applicable, store an appropriate DTC readable by a scan tool when a malfunction 

is present and the monitoring conditions have been satisfied for each individual 

monitor required by this section. For model years 2013 and later, the evaluation 

must demonstrate the ability of the OBD system on the selected test vehicle to 

detect a malfunction, activate the MIL, and, where applicable, store an 

appropriate DTC readable by a SAE J1978 or SAE J1939 (both as specified in 

paragraph (k)(1) of this section) scan tool when a malfunction is present and the 

monitoring conditions have been satisfied for each individual monitor required by 

this section.

(B) The evaluation must verify that the malfunction of any component used to 

enable another OBD monitor but that does not itself result in MIL activation (e.g.,

fuel level sensor) will not inhibit the ability of other OBD monitors to detect 

malfunctions properly.

(C) The evaluation must verify that the software used to track the numerator and 

denominator for the purpose of determining in-use monitoring frequency

increments as required by paragraph (d)(2) of this section.

(D) Malfunctions may be implanted mechanically or simulated electronically, but 

internal onboard computer hardware or software changes shall not be used to 

simulate malfunctions. For monitors that are required to indicate a malfunction 

before emissions exceed an emission threshold, manufacturers are not required to 

use malfunctioning components/systems set exactly at their malfunction criteria 

limits. Emission testing is not required to confirm that the malfunction is detected 

before the appropriate emission thresholds are exceeded.
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(E) The manufacturer must submit a proposed test plan for approval prior to 

performing evaluation testing. The test plan must identify the method used to 

induce a malfunction for each monitor.

(F) If the demonstration of a specific monitor cannot be reasonably performed 

without causing physical damage to the test vehicle (e.g., onboard computer 

internal circuit malfunctions), the manufacturer may omit the specific 

demonstration.

 

(G) For evaluation of test vehicles selected in accordance with paragraph (j)(2)(ii) 

of this section, the manufacturer is not required to demonstrate monitors that were 

demonstrated prior to certification as required in paragraph (l) of this section.

(iv) The manufacturer must submit a report of the results of all testing conducted as 

required by paragraph (j)(2) of this section. The report must identify the method 

used to induce a malfunction in each monitor, the MIL activation status, and the 

DTC(s) stored.

(3) Verification of in-use monitoring performance ratios.

(i) The manufacturer must collect and report in-use monitoring performance data 

representative of production vehicles (i.e., engine rating and chassis application 

combination). The manufacturer must collect and report the data to the 

Administrator within 12 months after the first production vehicle was first 

introduced into commerce.

(ii) The manufacturer must separate production vehicles into the monitoring 

performance groups and submit data that represents each of these groups. The 

groups shall be based on the following criteria:

(A) Emission control system architecture. All engines that use the same or similar 

emissions control system architecture (e.g., EGR with DPF and SCR; EGR with 

DPF and NOx adsorber; EGR with DPF-only) and associated monitoring system 

would be in the same emission architecture category.

(B) Vehicle application type. Within an emission architecture category, engines 

shall be separated into one of three vehicle application types: Engines intended 

primarily for line-haul chassis applications, engines intended primarily for urban 

delivery chassis applications, and all other engines.

(iii) The manufacturer may use an alternative grouping method to collect 

representative data. To do so, the manufacturer must show that the alternative 

groups include production vehicles using similar emission controls, OBD strategies, 

monitoring condition calibrations, and vehicle application driving/usage patterns 

such that they are expected to have similar in-use monitoring performance. The 

manufacturer will still be required to submit one set of data for each of the 

alternative groups.
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(iv) For each monitoring performance group, the data must include all of the in-use 

performance tracking data (i.e., all numerators, denominators, the general 

denominator, and the ignition cycle counter), the date the data were collected, the 

odometer reading, the VIN, and the calibration ID. For model years 2013 and later, 

for each monitoring performance group, the data must include all of the in-use 

performance tracking data reported through SAE J1979 or SAE J1939 (both as 

specified in paragraph (k)(1) of this section; i.e., all numerators, denominators, the 

general denominator, and the ignition cycle counter), the date the data were 

collected, the odometer reading, the VIN, and the calibration ID.

(v) The manufacturer must submit a plan to the Administrator that details the types 

of production vehicles in each monitoring performance group, the number of 

vehicles per group to be sampled, the sampling method, the timeline to collect the 

data, and the reporting format. The plan must provide for effective collection of 

data from, at least, 15 vehicles per monitoring performance group and provide for 

data that represent a broad range of temperature conditions. The plan shall not, by 

design, exclude or include specific vehicles in an attempt to collect data only from 

vehicles expected to have the highest in-use performance ratios.

(vi) The 12 month deadline for reporting may be extended to 18 months if the 

manufacturer can show that the delay is justified. In such a case, an interim report 

of progress to date must be submitted within the 12 month deadline.

(k) Standardization requirements

(1) Reference materials. The following documents are incorporated by reference, see 

§ 86.1. Anyone may inspect copies at the U.S. EPA or at the National Archives and 

Records Administration (NARA). For information on the availability of this material 

at U.S. EPA, NARA, or the standard making bodies directly, refer to § 86.1.

(i) SAE J1930, Revised April 2002.

(ii) SAE J1939, Revised October 2007.

 

(iii) SAE J1939-13, Revised March 2004, for model years 2013 and later.

(iv) SAE J1939-73, Revised September 2006.

(v) SAE J1962, Revised April 2002, for model years 2013 and later.

(vi) SAE J1978, Revised April 2002.

(vii) SAE J1979, Revised May 2007.

(viii) SAE J2012, Revised April 2002.
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(ix) SAE J2403, Revised August 2007.

(x) ISO 15765-4:2005(E), January 15, 2005.

(2) Diagnostic connector. For model years 2010 through 2012, the manufacturer 

defined data link connector must be accessible to a trained service technician. For 

model years 2013 and later, a standard data link connector conforming to SAE J1962 

(as specified in paragraph (k)(1) of this section) or SAE J1939-13 (as specified in 

paragraph (k)(1) of this section) specifications (except as provided for in paragraph 

(k)(2)(iii) if this section) must be included in each vehicle.

(i) For model years 2013 and later, the connector must be located in the driver’s 

side foot-well region of the vehicle interior in the area bound by the driver’s side of 

the vehicle and the driver’s side edge of the center console (or the vehicle centerline 

if the vehicle does not have a center console) and at a location no higher than the 

bottom of the steering wheel when in the lowest adjustable position. The connector 

shall not be located on or in the center console (i.e., neither on the horizontal faces 

near the floor-mounted gear selector, parking brake lever, or cup-holders nor on the 

vertical faces near the car stereo, climate system, or navigation system controls). 

The location of the connector shall be capable of being easily identified and 

accessed (e.g., to connect an off-board tool). For vehicles equipped with a driver’s 

side door, the connector must be identified and accessed easily by someone 

standing (or “crouched”) on the ground outside the driver’s side of the vehicle with 

the driver’s side door open. The Administrator may approve an alternative location 

upon request from the manufacturer. In all cases, the installation position of the 

connector must be both identified and accessed easily by someone standing outside 

the vehicle and protected from accidental damage during normal vehicle use.

(ii) For model years 2013 and later, if the connector is covered, the cover must be 

removable by hand without the use of any tools and be labeled “OBD” to aid 

technicians in identifying the location of the connector. Access to the diagnostic 

connector shall not require opening or the removal of any storage accessory (e.g., 

ashtray, coinbox). The label must clearly identify that the connector is located 

behind the cover and is consistent with language and/or symbols commonly used in

the automobile and/or heavy truck industry.

(iii) For model years 2013 and later, if the ISO 15765-4:2005(E) (as specified in 

paragraph (k)(1) of this section) communication protocol is used for the required 

OBD standardized functions, the connector must meet the “Type A” specifications 

of SAE J1962 (as specified in paragraph (k)(1) of this section). Any pins in the 

connector that provide electrical power must be properly fused to protect the 

integrity and usefulness of the connector for diagnostic purposes and shall not 

exceed 20.0 Volts DC regardless of the nominal vehicle system or battery voltage 

(e.g., 12V, 24V, 42V).

(iv) For model years 2013 and later, if the SAE J1939 (as specified in paragraph 

(k)(1) of this section) protocol is used for the required OBD standardized functions, 
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the connector must meet the specifications of SAE J1939-13 (as specified in 

paragraph (k)(1) of this section). Any pins in the connector that provide electrical 

power must be properly fused to protect the integrity and usefulness of the 

connector for diagnostic purposes.

(v) For model years 2013 and later, the manufacturer may equip engines/vehicles 

with additional diagnostic connectors for manufacturer-specific purposes (i.e., 

purposes other than the required OBD functions). However, if the additional 

connector conforms to the “Type A” specifications of SAE J1962 (as specified in 

paragraph (k)(1) of this section) or the specifications of SAE J1939-13 (as specified 

in paragraph (k)(1) of this section) and is located in the vehicle interior near the 

required connector as described in this paragraph (k)(2), the connector(s) must be 

labeled clearly to identify which connector is used to access the standardized OBD 

information required by paragraph (k) of this section.

(3) Communications to a scan tool. For model years 2013 and later, all OBD control 

modules (e.g., engine, auxiliary emission control module) on a single vehicle must 

use the same protocol for communication of required emission-related messages from 

on-board to off-board network communications to a scan tool meeting SAE J1978 (as 

specified in paragraph (k)(1) of this section) specifications or designed to 

communicate with an SAE J1939 (as specified in paragraph (k)(1) of this section) 

network. Engine manufacturers shall not alter normal operation of the engine 

emission control system due to the presence of off-board test equipment accessing 

information required by this paragraph (k). The OBD system must use one of the 

following standardized protocols:

(i) ISO 15765-4:2005(E) (as specified in paragraph (k)(1) of this section). All 

required emission-related messages using this protocol must use a 500 kbps baud 

rate.

(ii) SAE J1939 (as specified in paragraph (k)(1) of this section). This protocol may 

only be used on vehicles with diesel engines.

(4) Required emission related functions. The following functions must be 

implemented and must be accessible by, at a minimum, a manufacturer scan tool. For 

model years 2013 and later, the following standardized functions must be

implemented in accordance with the specifications in SAE J1979 (as specified in 

paragraph (k)(1) of this section) or SAE J1939 (as specified in paragraph (k)(1) of 

this section) to allow for access to the required information by a scan tool meeting 

SAE J1978 (as specified in paragraph (k)(1) of this section) specifications or designed 

to communicate with an SAE J1939 (as specified in paragraph (k)(1) of this section) 

network:

(i) Ready status. The OBD system must indicate, in accordance with SAE J1979 or 

SAE J1939-73 (both as specified in paragraph (k)(1) of this section) specifications 

for model years 2013 and later, “complete” or “not complete” for each of the 

installed monitored components and systems identified in paragraphs (g), (h) with 
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the exception of (h)(4), and (i)(3) of this section. All components or systems 

identified in paragraphs (h)(1), (h)(2), or (i)(3) of this section that are monitored 

continuously must always indicate “complete.” Components or systems that are not 

subject to being monitored continuously must immediately indicate “complete”

upon the respective monitor(s) being executed fully and determining that the 

component or system is not malfunctioning. A component or system must also 

indicate “complete” if, after the requisite number of decisions necessary for 

determining MIL status has been executed fully, the monitor indicates a 

malfunction of the component or system. The status for each of the monitored 

components or systems must indicate “not complete” whenever diagnostic memory 

has been cleared or erased by a means other than that allowed in paragraph (b) of 

this section. Normal vehicle shut down (i.e., key-off/engine-off) shall not cause the 

status to indicate “not complete.”

(A) The manufacturer may request that the ready status for a monitor be set to 

indicate “complete” without the monitor having completed if monitoring is 

disabled for a multiple number of drive cycles due to the continued presence of 

extreme operating conditions (e.g., cold ambient temperatures, high altitudes). 

Any such request must specify the conditions for monitoring system disablement 

and the number of drive cycles that would pass without monitor completion 

before ready status would be indicated as “complete.”

(B) For the evaporative system monitor, the ready status must be set in 

accordance with this paragraph (k)(4)(i) when both the functional check of the 

purge valve and, if applicable, the leak detection monitor of the hole size 

specified in paragraph (h)(7)(ii)(B) of this section indicate that they are complete.

(C) If the manufacturer elects to indicate ready status through the MIL in the keyon/engine-off position as provided for in paragraph (b)(1)(iii) of this section, the 

ready status must be indicated in the following manner: If the ready status for all 

monitored components or systems is “complete,” the MIL shall remain 

continuously activated in the key-on/engine-off position for at least 10-20 

seconds. If the ready status for one or more of the monitored components or 

systems is “not complete,” after at least 5 seconds of operation in the keyon/engine-off position with the MIL activated continuously, the MIL shall blink 

once per second for 5-10 seconds. The data stream value for MIL status as 

required in paragraph (k)(4)(ii) of this section must indicate “commanded off”

during this sequence unless the MIL has also been “commanded on” for a 

detected malfunction.

(ii) Data stream. For model years 2010 through 2012, the following signals must be 

made available on demand through the data link connector. For model years 2013 

and later, the following signals must be made available on demand through the 

standardized data link connector in accordance with SAE J1979 or SAE J1939 

(both as specified in paragraph (k)(1) of this section) specifications. The actual 

signal value must always be used instead of a limp home value. Data link signals 

may report an error state or other predefined status indicator if they are defined for 
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those signals in the SAE J1979 or SAE J1939 (both as specified in paragraph (k)(1) 

of this section) specifications.

(A) For gasoline engines.

1. Calculated load value, engine coolant temperature, engine speed, vehicle 

speed, and time elapsed since engine start.

2. Absolute load, fuel level (if used to enable or disable any other monitors), 

barometric pressure (directly measured or estimated), engine control module 

system voltage, and commanded equivalence ratio.

3. Number of stored MIL-on DTCs, catalyst temperature (if directly measured 

or estimated for purposes of enabling the catalyst monitor(s)), monitor status 

(i.e., disabled for the rest of this drive cycle, complete this drive cycle, or not 

complete this drive cycle) since last engine shut-off for each monitor used for 

ready status, distance traveled (or engine run time for engines not using 

vehicle speed information) while MIL activated, distance traveled (or engine 

run time for engines not using vehicle speed information) since DTC memory 

last erased, and number of warm-up cycles since DTC memory last erased, 

OBD requirements to which the engine is certified (e.g., California OBD, 

EPA OBD, European OBD, non-OBD) and MIL status (i.e., commanded-on 

or commanded-off).

(B) For diesel engines.

1. Calculated load (engine torque as a percentage of maximum torque 

available at the current engine speed), driver’s demand engine torque (as a 

percentage of maximum engine torque), actual engine torque (as a percentage 

of maximum engine torque), reference engine maximum torque, reference 

maximum engine torque as a function of engine speed (suspect parameter 

numbers (SPN) 539 through 543 defined by SAE J1939 (as specified in 

paragraph (k)(1) of this section) within parameter group number (PGN) 65251 

for engine configuration), engine coolant temperature, engine oil temperature 

(if used for emission control or any OBD monitors), engine speed, and time 

elapsed since engine start.

2. Fuel level (if used to enable or disable any other monitors), vehicle speed 

(if used for emission control or any OBD monitors), barometric pressure 

(directly measured or estimated), and engine control module system voltage.

3. Number of stored MIL-on DTCs, monitor status (i.e., disabled for the rest 

of this drive cycle, complete this drive cycle, or not complete this drive cycle) 

since last engine shut-off for each monitor used for ready status, distance 

traveled (or engine run time for engines not using vehicle speed information) 

while MIL activated, distance traveled (or engine run time for engines not 

using vehicle speed information) since DTC memory last erased, number of 
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warm-up cycles since DTC memory last erased, OBD requirements to which 

the engine is certified (e.g., California OBD, EPA OBD, European OBD, nonOBD), and MIL status (i.e., commanded-on or commanded-off).

4. NOx NTE control area status (i.e., inside control area, outside control area, 

inside manufacturer-specific NOx NTE carve-out area, or deficiency active 

area) and PM NTE control area status (i.e., inside control area, outside control 

area, inside manufacturer-specific PM NTE carve-out area, or deficiency 

active area).

5. For purposes of the calculated load and torque parameters in paragraph 

(k)(4)(ii)(B)(1) of this section, manufacturers must report the most accurate 

values that are calculated within the applicable electronic control unit (e.g.,

the engine control module). Most accurate, in this context, must be of 

sufficient accuracy, resolution, and filtering to be used for the purposes of inuse emission testing with the engine still in a vehicle (e.g., using portable 

emission measurement equipment).

(C) For all engines so equipped.

 

1. Absolute throttle position, relative throttle position, fuel control system 

status (e.g., open loop, closed loop), fuel trim, fuel pressure, ignition timing 

advance, fuel injection timing, intake air/manifold temperature, engine 

intercooler temperature, manifold absolute pressure, air flow rate from mass 

air flow sensor, secondary air status (upstream, downstream, or atmosphere), 

ambient air temperature, commanded purge valve duty cycle/position, 

commanded EGR valve duty cycle/position, actual EGR valve duty 

cycle/position, EGR error between actual and commanded, PTO status (active 

or not active), redundant absolute throttle position (for electronic throttle or 

other systems that utilize two or more sensors), absolute pedal position, 

redundant absolute pedal position, commanded throttle motor position, fuel 

rate, boost pressure, commanded/target boost pressure, turbo inlet air 

temperature, fuel rail pressure, commanded fuel rail pressure, DPF inlet 

pressure, DPF inlet temperature, DPF outlet pressure, DPF outlet temperature, 

DPF delta pressure, exhaust pressure sensor output, exhaust gas temperature 

sensor output, injection control pressure, commanded injection control 

pressure, turbocharger/turbine speed, variable geometry turbo position, 

commanded variable geometry turbo position, turbocharger compressor inlet 

temperature, turbocharger compressor inlet pressure, turbocharger turbine 

inlet temperature, turbocharger turbine outlet temperature, waste gate valve 

position, and glow plug lamp status.

2. Oxygen sensor output, air/fuel ratio sensor output, NOx sensor output, and 

evaporative system vapor pressure.

(iii) Freeze frame.
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(A) For model years 2010 through 2012, “Freeze frame” information required to 

be stored pursuant to paragraphs (b)(2)(iv), (h)(1)(iv)(D), and (h)(2)(vi) of this 

section must be made available on demand through the data link connector. For 

model years 2013 and later, “Freeze frame” information required to be stored 

pursuant to paragraphs (b)(2)(iv), (h)(1)(iv)(D), and (h)(2)(vi) of this section must 

be made available on demand through the standardized data link connector in 

accordance with SAE J1979 or SAE J1939-73 (both as specified in paragraph 

(k)(1) of this section) specifications.

(B) “Freeze frame” conditions must include the DTC that caused the data to be 

stored along with all of the signals required in paragraphs (k)(4)(ii)(A)(1) and 

(k)(4)(ii)(B)(1) of this section. Freeze frame conditions must also include all of 

the signals required on the engine in paragraphs (k)(4)(ii)(A)(2) and 

(k)(4)(ii)(B)(2) of this section, and paragraph (k)(4)(ii)(C)(1) of this section that 

are used for diagnostic or control purposes in the specific monitor or emissioncritical powertrain control unit that stored the DTC.

(C) Only one frame of data is required to be recorded. For model years 2010 

through 2012, the manufacturer may choose to store additional frames provided 

that at least the required frame can be read by, at a minimum, a manufacturer scan 

tool. For model years 2013 and later, the manufacturer may choose to store 

additional frames provided that at least the required frame can be read by a scan 

tool meeting SAE J1978 (as specified in paragraph (k)(1) of this section) 

specifications or designed to communicate with an SAE J1939 (as specified in 

paragraph (k)(1) of this section) network.

(iv) Diagnostic trouble codes.

(A) For model years 2010 through 2012, For all monitored components and 

systems, any stored pending, MIL-on, and previous-MIL-on DTCs must be made 

available through the diagnostic connector. For model years 2013 and later, all 

monitored components and systems, any stored pending, MIL-on, and previousMIL-on DTCs must be made available through the diagnostic connector in a 

standardized format in accordance with SAE J1939 (as specified in paragraph 

(k)(1) of this section) or ISO 15765-4:2005(E) (as specified in paragraph (k)(1) of 

this section) specifications; standardized DTCs conforming to the applicable 

standardized specifications must be employed.

(B) The stored DTC must, to the extent possible, pinpoint the probable cause of 

the malfunction or potential malfunction. To the extent feasible, the manufacturer 

must use separate DTCs for every monitor where the monitor and repair 

procedure or probable cause of the malfunction is different. In general, rationality 

and functional checks must use different DTCs than the respective circuit 

integrity checks. Additionally, to the extent possible, input component circuit 

integrity checks must use different DTCs for distinct malfunctions (e.g., out-ofrange low, out-of-range high, open circuit).
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(C) The manufacturer must use appropriate standard-defined DTCs whenever 

possible. With Administrator approval, the manufacturer may use manufacturerdefined DTCs in accordance with the applicable standard’s specifications. To do 

so, the manufacturer must be able to show a lack of available standard-defined 

DTCs, uniqueness of the monitor or monitored component, expected future usage 

of the monitor or component, and estimated usefulness in providing additional 

diagnostic and repair information to service technicians. Manufacturer-defined 

DTCs must be used in a consistent manner (i.e., the same DTC shall not be used 

to represent two different failure modes) across a manufacturer’s entire product 

line.

(D) For model years 2010 through 2012, a pending or MIL-on DTC (as required 

in paragraphs (g) through (i) of this section) must be stored and available to, at a 

minimum, a manufacturer scan tool within 10 seconds after a monitor has 

determined that a malfunction or potential malfunction has occurred. A permanent 

DTC must be stored and available to, at a minimum, a manufacturer scan tool no 

later than the end of an ignition cycle in which the corresponding MIL-on DTC 

that caused MIL activation has been stored. For model years 2013 and later, a 

pending or MIL-on DTC (as required in paragraphs (g) through (i) of this section) 

must be stored and available to an SAE J1978 (as specified in paragraph (k)(1) of 

this section) or SAE J1939 (as specified in paragraph (k)(1) of this section) scan 

tool within 10 seconds after a monitor has determined that a malfunction or 

potential malfunction has occurred. A permanent DTC must be stored and 

available to an SAE J1978 (as specified in paragraph (k)(1) of this section) or 

SAE J1939 (as specified in paragraph (k)(1) of this section) scan tool no later than 

the end of an ignition cycle in which the corresponding MIL-on DTC that caused 

MIL activation has been stored.

(E) For model years 2010 through 2012, pending DTCs for all components and 

systems (including those monitored continuously and non-continuously) must be 

made available through the diagnostic connector. For model years 2013 and later, 

pending DTCs for all components and systems (including those monitored 

continuously and non-continuously) must be made available through the 

diagnostic connector in accordance with the applicable standard’s specifications. 

For all model years, a manufacturer using alternative statistical protocols for MIL 

activation as allowed in paragraph (b)(2)(iii) of this section must submit the 

details of their protocol for setting pending DTCs. The protocol must be, overall, 

equivalent to the requirements of this paragraph (k)(4)(iv)(E) and provide service 

technicians with a quick and accurate indication of a potential malfunction.

(F) For model years 2010 through 2012, permanent DTC for all components and 

systems must be made available through the diagnostic connector in a format that 

distinguishes permanent DTCs from pending DTCs, MIL-on DTCs, and previousMIL-on DTCs. A MIL-on DTC must be stored as a permanent DTC no later than 

the end of the ignition cycle and subsequently at all times that the MIL-on DTC is 

commanding the MIL on. For model years 2013 and later, permanent DTC for all 

components and systems must be made available through the diagnostic connector 
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in a standardized format that distinguishes permanent DTCs from pending DTCs, 

MIL-on DTCs, and previous-MIL-on DTCs. A MIL-on DTC must be stored as a 

permanent DTC no later than the end of the ignition cycle and subsequently at all 

times that the MIL-on DTC is commanding the MIL on. For all model years, 

permanent DTCs must be stored in non-volatile random access memory 

(NVRAM) and shall not be erasable by any scan tool command or by 

disconnecting power to the on-board computer. Permanent DTCs must be 

erasable if the engine control module is reprogrammed and the ready status 

described in paragraph (k)(4)(i) of this section for all monitored components and 

systems are set to “not complete.” The OBD system must have the ability to store 

a minimum of four current MIL-on DTCs as permanent DTCs in NVRAM. If the 

number of MIL-on DTCs currently commanding activation of the MIL exceeds 

the maximum number of permanent DTCs that can be stored, the OBD system 

must store the earliest detected MIL-on DTC as permanent DTC. If additional 

MIL-on DTCs are stored when the maximum number of permanent DTCs is 

already stored in NVRAM, the OBD system shall not replace any existing 

permanent DTC with the additional MIL-on DTCs.

(v) Test results.

(A) For model years 2010 through 2012 and except as provided for in paragraph 

(k)(4)(v)(G) of this section, for all monitored components and systems identified 

in paragraphs (g) and (h) of this section, results of the most recent monitoring of 

the components and systems and the test limits established for monitoring the 

respective components and systems must be stored and available through the data 

link. For model years 2013 and later and except as provided for in paragraph 

(k)(4)(v)(G) of this section, for all monitored components and systems identified 

in paragraphs (g) and (h) of this section, results of the most recent monitoring of 

the components and systems and the test limits established for monitoring the 

respective components and systems must be stored and available through the data 

link in accordance with the standardized format specified in SAE J1979 (as 

specified in paragraph (k)(1) of this section) for engines using the ISO 15765-

4:2005(E) (as specified in paragraph (k)(1) of this section) protocol or SAE J1939 

(as specified in paragraph (k)(1) of this section).

(B) The test results must be reported such that properly functioning components 

and systems (e.g., “passing” systems) do not store test values outside of the 

established test limits. Test limits must include both minimum and maximum 

acceptable values and must be defined so that a test result equal to either test limit 

is a “passing” value, not a “failing” value.

(C) For model years 2013 and later, the test results must be standardized such that 

the name of the monitored component (e.g., catalyst bank 1) can be identified by a 

generic scan tool and the test results and limits can be scaled and reported by a 

generic scan tool with the appropriate engineering units.
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(D) The test results must be stored until updated by a more recent valid test result 

or the DTC memory of the OBD system computer is cleared. Upon DTC memory 

being cleared, test results reported for monitors that have not yet completed with 

valid test results since the last time the fault memory was cleared must report 

values of zero for the test result and test limits.

(E) All test results and test limits must always be reported and the test results 

must be stored until updated by a more recent valid test result or the DTC 

memory of the OBD system computer is cleared.

(F) The OBD system must store and report unique test results for each separate 

monitor.

(G) The requirements of this paragraph (k)(4)(v) do not apply to continuous fuel 

system monitoring, cold start emission reduction strategy monitoring, and 

continuous circuit monitoring.

(vi) Software calibration identification (CAL ID). On all engines, a single software 

calibration identification number (CAL ID) for each monitor or emission critical 

control unit(s) must be made available through, for model years 2010 through 2012, 

the data link connector or, for model years 2013 and later, the standardized data link 

connector in accordance with the SAE J1979 or SAE J1939 (both as specified in 

paragraph (k)(1) of this section) specifications. A unique CAL ID must be used for 

every emission-related calibration and/or software set having at least one bit of 

different data from any other emission-related calibration and/or software set. 

Control units coded with multiple emission or diagnostic calibrations and/or 

software sets must indicate a unique CAL ID for each variant in a manner that 

enables an off-board device to determine which variant is being used by the engine. 

Control units that use a strategy that will result in MIL activation if the incorrect 

variant is used (e.g., control units that contain variants for manual and automatic 

transmissions but will activate the MIL if the selected variant does not match the 

type of transmission mated to the engine) are not required to use unique CAL IDs. 

Manufacturers may request Administrator approval to respond with more than one 

CAL ID per diagnostic or emission critical control unit. Administrator approval of 

the request shall be based on the method used by the manufacturer to ensure each 

control unit will respond to a scan tool with the CAL IDs in order of highest to 

lowest priority with regards to areas of the software most critical to emission and 

OBD system performance.

(vii) Software calibration verification number (CVN).

(A) All engines must use an algorithm to calculate a single calibration verification 

number (CVN) that verifies the on-board computer software integrity for each 

monitor or emission critical control unit that is electronically reprogrammable. 

The CVN must be made available through, for model years 2010 through 2012, 

the data link connector or, for model years 2013 and later, the standardized data 

link connector in accordance with the SAE J1979 or SAE J1939 (both as specified 
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in paragraph (k)(1) of this section) specifications. The CVN must indicate 

whether the emission-related software and/or calibration data are valid and 

applicable for the given vehicle and CAL ID. For systems having more than one 

CAL ID as allowed under paragraph (k)(4)(vi) of this section, one CVN must be 

made available for each CAL ID and must be output to a scan tool in the same 

order as the corresponding CAL IDs. For 2010 through 2012, manufacturers may 

use a default value for the CVN if their emissions critical powertrain control 

modules are not programmable in the field. For all years, manufacturers may use 

a default value for the CVN if their emissions critical powertrain control modules 

are one-time programmable or masked read-only memory. Any default CVN shall 

be 00000000 for systems designed in accordance with the SAE J1979 (as 

specified in paragraph (k)(1) of this section) specifications, and FFFFFFFFh for 

systems designed in accordance with the SAE J1939 (as specified in paragraph 

(k)(1) of this section) specifications.

(B) The CVN algorithm used to calculate the CVN must be of sufficient 

complexity that the same CVN is difficult to achieve with modified calibration 

values.

(C) The CVN must be calculated at least once per ignition cycle and stored until 

the CVN is subsequently updated. Except for immediately after a reprogramming 

event or a non-volatile memory clear or for the first 30 seconds of engine 

operation after a volatile memory clear or battery disconnect, the stored value 

must be made available through, for model years 2010 through 2012, the data link 

connector to, at a minimum, a manufacturer scan tool or, for model years 2013 

and later, the data link connector to a generic scan tool in accordance with SAE 

J1979 or SAE J1939 (both as specified in paragraph (k)(1) of this section) 

specifications. For model years 2010 through 2012, the stored CVN value shall 

not be erased when DTC memory is erased or during normal vehicle shut down 

(i.e., key-off/engine-off). For model years 2013 and later, the stored CVN value 

shall not be erased when DTC memory is erased by a generic scan tool in 

accordance with SAE J1979 or SAE J1939 (both as specified in paragraph (k)(1) 

of this section) specifications or during normal vehicle shut down (i.e., keyoff/engine-off).

(D) For model years 2013 and later, the CVN and CAL ID combination 

information must be available for all engines/vehicles in a standardized electronic 

format that allows for off-board verification that the CVN is valid and appropriate 

for a specific vehicle and CAL ID.

(viii) Vehicle identification number (VIN).

(A) For model years 2010 through 2012, all vehicles must have the vehicle 

identification number (VIN) available through the data link connector to, at a 

minimum, a manufacturer scan tool Only one electronic control unit per vehicle 

may report the VIN to a scan tool. For model years 2013 and later, all vehicles 

must have the vehicle identification number (VIN) available in a standardized 
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format through the standardized data link connector in accordance with SAE 

J1979 or SAE J1939 (both as specified in paragraph (k)(1) of this section) 

specifications. Only one electronic control unit per vehicle may report the VIN to 

an SAE J1978 or SAE J1939 (both as specified in paragraph (k)(1) of this section) 

scan tool.

(B) If the VIN is reprogrammable, all emission-related diagnostic information 

identified in paragraph (k)(4)(ix)(A) of this section must be erased in conjunction 

with reprogramming of the VIN.

(ix) Erasure of diagnostic information.

(A) For purposes of this paragraph (k)(4)(ix), “emission-related diagnostic 

information” includes all of the following: ready status as required by paragraph 

(k)(4)(i) of this section; data stream information as required by paragraph 

(k)(4)(ii) of this section including the number of stored MIL-on DTCs, distance 

traveled while MIL activated, number of warm-up cycles since DTC memory last 

erased, and distance traveled since DTC memory last erased; freeze frame 

information as required by paragraph (k)(4)(iii) of this section; pending, MIL-on, 

and previous-MIL-on DTCs as required by paragraph (k)(4)(iv) of this section; 

and, test results as required by paragraph (k)(4)(v) of this section.

(B) For all engines, the emission-related diagnostic information must be erased if 

commanded by any scan tool and may be erased if the power to the on-board 

computer is disconnected. If any of the emission-related diagnostic information is 

commanded to be erased by any scan tool, all emission-related diagnostic 

information must be erased from all diagnostic or emission critical control units. 

The OBD system shall not allow a scan tool to erase a subset of the emissionrelated diagnostic information (e.g., the OBD system shall not allow a scan tool to 

erase only one of three stored DTCs or only information from one control unit 

without erasing information from the other control unit(s)).

(5) In-use performance ratio tracking requirements.

(i) For each monitor required in paragraphs (g) through (i) of this section to 

separately report an in-use performance ratio, manufacturers must implement 

software algorithms to, for model years 2010 through 2012, report a numerator and 

denominator or, for model years 2013 and later, report a numerator and 

denominator in the standardized format specified in this paragraph (k)(5) in 

accordance with the SAE J1979 or SAE J1939 (both as specified in paragraph 

(k)(1) of this section) specifications.

(ii) For the numerator, denominator, general denominator, and ignition cycle 

counters required by paragraph (e) of this section, the following numerical value 

specifications apply:
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(A) Each number shall have a minimum value of zero and a maximum value of 

65,535 with a resolution of one.

(B) Each number shall be reset to zero only when a non-volatile random access 

memory (NVRAM) reset occurs (e.g., reprogramming event) or, if the numbers 

are stored in keep-alive memory (KAM), when KAM is lost due to an interruption 

in electrical power to the control unit (e.g., battery disconnect). Numbers shall not 

be reset to zero under any other circumstances including when a scan tool 

command to clear DTCs or reset KAM is received.

(C) To avoid overflow problems, if either the numerator or denominator for a 

specific component reaches the maximum value of 65,535 ±2, both numbers shall 

be divided by two before either is incremented again.

(D) To avoid overflow problems, if the ignition cycle counter reaches the 

maximum value of 65,535 ±2, the ignition cycle counter shall rollover and

increment to zero on the next ignition cycle.

(E) To avoid overflow problems, if the general denominator reaches the 

maximum value of 65,535 ±2, the general denominator shall rollover and 

increment to zero on the next drive cycle that meets the general denominator 

definition.

(F) If a vehicle is not equipped with a component (e.g., oxygen sensor bank 2, 

secondary air system), the corresponding numerator and denominator for that 

specific component shall always be reported as zero.

(iii) For the ratio required by paragraph (e) of this section, the following numerical 

value specifications apply:

(A) The ratio shall have a minimum value of zero and a maximum value of 

7.99527 with a resolution of 0.000122.

(B) The ratio for a specific component shall be considered to be zero whenever 

the corresponding numerator is equal to zero and the corresponding denominator 

is not zero.

(C) The ratio for a specific component shall be considered to be the maximum 

value of 7.99527 if the corresponding denominator is zero or if the actual value of 

the numerator divided by the denominator exceeds the maximum value of 

7.99527.

(6) Engine run time tracking requirements.

(i) For all gasoline and diesel engines, the manufacturer must implement software 

algorithms to, for model years 2010 through 2012, track and report individually or, 
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for model years 2013 and later, track and report individually in a standardized 

format the amount of time the engine has been operated in the following conditions:

(A) Total engine run time.

(B) Total idle run time (with “idle” defined as accelerator pedal released by the 

driver, engine speed less than or equal to 200 rpm above normal warmed-up idle 

(as determined in the drive position for vehicles equipped with an automatic 

transmission) or vehicle speed less than or equal to one mile per hour, and power 

take-off not active).

(C) Total run time with power take off active.

(ii) For each counter specified in paragraph (k)(6)(i) of this section, the following 

numerical value specifications apply:

(A) Each number shall be a four-byte value with a minimum value of zero, a 

resolution of one second per bit, and an accuracy of ± ten seconds per drive cycle.

(B) Each number shall be reset to zero only when a non-volatile memory reset 

occurs (e.g., reprogramming event). Numbers shall not be reset to zero under any 

other circumstances including when a scan tool (generic or enhanced) command 

to clear fault codes or reset KAM is received.

(C) To avoid overflow problems, if any of the individual counters reach the 

maximum value, all counters shall be divided by two before any are incremented 

again.

(D) For model years 2010 through 2012, the counters shall be made available to, 

at a minimum, a manufacturer scan tool and may be rescaled when transmitted 

from a resolution of one second per bit to no more than three minutes per bit. For 

model years 2013 and later, the counters shall be made available to a generic scan 

tool in accordance with the SAE J1979 or SAE J1939 (both as specified in 

paragraph (k)(1) of this section) specifications and may be rescaled when 

transmitted, if required by the SAE specifications, from a resolution of one second 

per bit to no more than three minutes per bit.

(7) For 2019 and subsequent model year alternative-fueled engines derived from a 

diesel-cycle engine, a manufacturer may meet the standardization requirements of 

paragraph (k) of this section that are applicable to diesel engines rather than the 

requirements applicable to gasoline engines.

(l) Monitoring system demonstration requirements for certification

(1) General.
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(i) The manufacturer must submit emissions test data from one or more durability 

demonstration test engines (test engines).

(ii) The Administrator may approve other demonstration protocols if the 

manufacturer can provide comparable assurance that the malfunction criteria are 

chosen based on meeting the malfunction criteria requirements and that the 

timeliness of malfunction detection is within the constraints of the applicable 

monitoring requirements.

 

(iii) For flexible fuel engines capable of operating on more than one fuel or fuel 

combinations, the manufacturer must submit a plan for providing emission test data. 

The plan must demonstrate that testing will represent properly the expected in-use 

fuel or fuel combinations.

(2) Selection of test engines.

(i) Prior to submitting any applications for certification for a model year, the 

manufacturer must notify the Administrator regarding the planned engine families 

and engine ratings within each family for that model year. The Administrator will 

select the engine family(ies) and the specific engine rating within the engine 

family(ies) that the manufacturer shall use as demonstration test engines. The 

selection of test vehicles for production evaluation testing as specified in paragraph 

(j)(2) of this section may take place during this selection process.

(ii) For model years 2010 through 2012. The manufacturer must provide emissions 

test data from the OBD parent rating as defined in paragraph (o)(1) of this section.

(iii) For model years 2013 and later.

(A) A manufacturer certifying one to five engine families in a given model year 

must provide emissions test data for a single test engine from one engine rating. A 

manufacturer certifying six to ten engine families in a given model year must 

provide emissions test data for a single test engine from two different engine 

ratings. A manufacturer certifying eleven or more engine families in a given 

model year must provide emissions test data for a single test engine from three 

different engine ratings. A manufacturer may forego submittal of test data for one 

or more of these test engines if data have been submitted previously for all of the 

engine ratings and/or if all requirements for certification carry-over from one 

model year to the next are satisfied.

(B) For a given model year, a manufacturer may elect to provide emissions data 

for test engines from more engine ratings than required by paragraph (l)(2)(iii)(A) 

of this section. For each additional engine rating tested in that given model year, 

the number of engine ratings required for testing in one future model year will be 

reduced by one.
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(iv) For the test engine, the manufacturer must use an engine (excluding 

aftertreatment devices) aged for a minimum of 125 hours fitted with exhaust 

aftertreatment emission controls aged to be representative of useful life aging. In the 

event that an accelerated aging procedure is used, the manufacturer is required to 

submit a description of the accelerated aging process and/or supporting data or use 

the accelerated aging procedure used for emission certification deterioration factor 

generation. The process and/or data must demonstrate that deterioration of the 

exhaust aftertreatment emission controls is stabilized sufficiently such that it 

represents emission control performance at the end of the useful life.

(3) Required testing. Except as otherwise described in this paragraph (l)(3), the 

manufacturer must perform single malfunction testing based on the applicable test 

with the components/systems set at their malfunction criteria limits as determined by 

the manufacturer for meeting the emissions thresholds required in paragraphs (g), (h), 

and (i) of this section.

(i) Required testing for diesel-fueled/compression ignition engines

(A) Fuel system. The manufacturer must perform a separate test for each 

malfunction limit established by the manufacturer for the fuel system parameters 

(e.g., fuel pressure, injection timing) specified in paragraphs (g)(1)(ii)(A) through 

(g)(1)(ii)(C) and/or (g)(1)(ii)(D) of this section, if applicable, of this section. 

When performing a test for a specific parameter, the fuel system must be 

operating at the malfunction criteria limit for the applicable parameter only. All 

other parameters must be operating with normal characteristics. In conducting the 

fuel system demonstration tests, the manufacturer may use computer 

modifications to cause the fuel system to operate at the malfunction limit if the 

manufacturer can demonstrate that the computer modifications produce test 

results equivalent to an induced hardware malfunction.

(B) Engine misfire. For model years 2013 and later, the manufacturer must 

perform a test at the malfunction limit established by the manufacturer for the 

monitoring required by paragraph (g)(2)(ii)(B) of this section.

(C) EGR system. The manufacturer must perform a separate test for each 

malfunction limit established by the manufacturer for the EGR system parameters 

(e.g., low flow, high flow, slow response) specified in paragraphs (g)(3)(ii)(A) 

through (g)(3)(ii)(C) and in (g)(3)(ii)(E) of this section. In conducting the EGR 

system slow response demonstration tests, the manufacturer may use computer 

modifications to cause the EGR system to operate at the malfunction limit if the 

manufacturer can demonstrate that the computer modifications produce test 

results equivalent to an induced hardware malfunction.

(D) Turbo boost control system. The manufacturer must perform a separate test 

for each malfunction limit established by the manufacturer for the turbo boost 

control system parameters (e.g., underboost, overboost, response) specified in 

paragraphs (g)(4)(ii)(A) through (g)(4)(ii)(C) and in (g)(4)(ii)(E) of this section.
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(E) NMHC catalyst. The manufacturer must perform a separate test for each 

monitored NMHC catalyst(s). The catalyst(s) being evaluated must be 

deteriorated to the applicable malfunction limit established by the manufacturer 

for the monitoring required by paragraph (g)(5)(ii)(A) of this section and using 

methods established by the manufacturer in accordance with paragraph (l)(7) of 

this section. For each monitored NMHC catalyst(s), the manufacturer must also 

demonstrate that the OBD system will detect a catalyst malfunction with the 

catalyst at its maximum level of deterioration (i.e., the substrate(s) completely 

removed from the catalyst container or “empty” can). Emissions data are not 

required for the empty can demonstration.

(F) NOx catalyst. The manufacturer must perform a separate test for each 

monitored NOx catalyst(s) (e.g., SCR catalyst). The catalyst(s) being evaluated 

must be deteriorated to the applicable malfunction criteria established by the 

manufacturer for the monitoring required by paragraphs (g)(6)(ii)(A) and 

(g)(6)(ii)(B) of this section and using methods established by the manufacturer in 

accordance with paragraph (l)(7) of this section. For each monitored NOx

catalyst(s), the manufacturer must also demonstrate that the OBD system will 

detect a catalyst malfunction with the catalyst at its maximum level of 

deterioration (i.e., the substrate(s) completely removed from the catalyst container 

or “empty” can). Emissions data are not required for the empty can 

demonstration.

(G) NOx adsorber. The manufacturer must perform a test using a NOx adsorber(s) 

deteriorated to the applicable malfunction limit established by the manufacturer 

for the monitoring required by paragraph (g)(7)(ii)(A) of this section. The 

manufacturer must also demonstrate that the OBD system will detect a NOx

adsorber malfunction with the NOx adsorber at its maximum level of 

deterioration (i.e., the substrate(s) completely removed from the container or 

“empty” can). Emissions data are not required for the empty can demonstration.

(H) Diesel particulate filter. The manufacturer must perform a separate test using 

a DPF deteriorated to the applicable malfunction limits established by the 

manufacturer for the monitoring required by paragraph (g)(8)(ii)(A) and 

(g)(8)(ii)(B) of this section. For systems using the optional DPF monitoring 

provision of paragraph (g)(8)(ii)(A) of this section, the manufacturer must 

perform a separate test using a DPF modified in a manner approved by the 

Administrator (e.g., drilling of wallflow channel end plugs, drilling of through 

holes, etc.) and testing at each of the nine test points specified in paragraph 

(g)(8)(ii)(A) of this section. The manufacturer must also demonstrate that the 

OBD system will detect a DPF malfunction with the DPF at its maximum level of 

deterioration (i.e., the filter(s) completely removed from the filter container or 

“empty” can). Emissions data are not required for the empty can demonstration.

(I) Exhaust gas sensor. The manufacturer must perform a separate test for each 

malfunction limit established by the manufacturer for the monitoring required in 
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paragraphs (g)(9)(ii)(A), (g)(9)(iii)(A), and (g)(9)(iv)(A) of this section. When 

performing a test, all exhaust gas sensors used for the same purpose (e.g., for the 

same feedback control loop, for the same control feature on parallel exhaust 

banks) must be operating at the malfunction criteria limit for the applicable 

parameter only. All other exhaust gas sensor parameters must be operating with 

normal characteristics.

(J) VVT system. The manufacturer must perform a separate test for each 

malfunction limit established by the manufacturer for the monitoring required in 

paragraphs (g)(10)(ii)(A) and (g)(10)(ii)(B) of this section. In conducting the 

VVT system demonstration tests, the manufacturer may use computer 

modifications to cause the VVT system to operate at the malfunction limit if the 

manufacturer can demonstrate that the computer modifications produce test 

results equivalent to an induced hardware malfunction.

(K) For each of the testing requirements of this paragraph (l)(3)(i) of this section, 

if the manufacturer has established that only a functional check is required 

because no failure or deterioration of the specific tested system could result in an 

engine’s emissions exceeding the applicable emissions thresholds, the 

manufacturer is not required to perform a demonstration test; however, the 

manufacturer is required to provide the data and/or engineering analysis used to 

determine that only a functional test of the system(s) is required.

(ii) Required testing for gasoline-fueled/spark-ignition engines

(A) Fuel system. For engines with adaptive feedback based on the primary fuel 

control sensor(s), the manufacturer must perform a test with the adaptive feedback 

based on the primary fuel control sensor(s) at the rich limit(s) and a test at the lean 

limit(s) established by the manufacturer as required by paragraph (h)(1)(ii)(A) of 

this section to detect a malfunction before emissions exceed applicable emissions 

thresholds. For engines with feedback based on a secondary fuel control sensor(s) 

and subject to the malfunction criteria in paragraph (h)(1)(ii)(A) of this section, 

the manufacturer must perform a test with the feedback based on the secondary 

fuel control sensor(s) at the rich limit(s) and a test at the lean limit(s) established

by the manufacturer as required by paragraph (h)(1)(ii)(A) of this section to detect 

a malfunction before emissions exceed the applicable emissions thresholds. For 

other fuel metering or control systems, the manufacturer must perform a test at the 

criteria limit(s). For purposes of fuel system testing as required by this paragraph 

(l)(3)(ii)(A), the malfunction(s) induced may result in a uniform distribution of 

fuel and air among the cylinders. Non uniform distribution of fuel and air used to 

induce a malfunction shall not cause misfire. In conducting the fuel system 

demonstration tests, the manufacturer may use computer modifications to cause 

the fuel system to operate at the malfunction limit. To do so, the manufacturer 

must be able to demonstrate that the computer modifications produce test results 

equivalent to an induced hardware malfunction.
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(B) Misfire. The manufacturer must perform a test at the malfunction criteria limit 

specified in paragraph (h)(2)(ii)(B) of this section.

(C) EGR system. The manufacturer must perform a test at each flow limit 

calibrated to the malfunction criteria specified in paragraphs (h)(3)(ii)(A) and 

(h)(3)(ii)(B) of this section.

(D) Cold start emission reduction strategy. The manufacturer must perform a test 

at the malfunction criteria for each component monitored according to paragraph 

(h)(4)(ii)(A) of this section.

(E) Secondary air system. The manufacturer must perform a test at each flow limit 

calibrated to the malfunction criteria specified in paragraphs (h)(5)(ii)(A) and 

(h)(5)(ii)(B) of this section.

(F) Catalyst. The manufacturer must perform a test using a catalyst system 

deteriorated to the malfunction criteria specified in paragraph (h)(6)(ii) of this 

section using methods established by the manufacturer in accordance with 

paragraph (l)(7)(ii) of this section. The manufacturer must also demonstrate that 

the OBD system will detect a catalyst system malfunction with the catalyst system 

at its maximum level of deterioration (i.e., the substrate(s) completely removed 

from the catalyst container or “empty” can). Emission data are not required for the 

empty can demonstration.

(G) Exhaust gas sensor. The manufacturer must perform a test with all primary 

exhaust gas sensors used for fuel control simultaneously possessing a response 

rate deteriorated to the malfunction criteria limit specified in paragraph 

(h)(8)(ii)(A) of this section. The manufacturer must also perform a test for any 

other primary or secondary exhaust gas sensor parameter under parargraphs 

(h)(8)(ii)(A) and (h)(8)(iii)(A) of this section that can cause engine emissions to 

exceed the applicable emissions thresholds (e.g., shift in air/fuel ratio at which 

oxygen sensor switches, decreased amplitude). When performing additional 

test(s), all primary and secondary (if applicable) exhaust gas sensors used for 

emission control must be operating at the malfunction criteria limit for the 

applicable parameter only. All other primary and secondary exhaust gas sensor 

parameters must be operating with normal characteristics.

(H) VVT system. The manufacturer must perform a test at each target error limit 

and slow response limit calibrated to the malfunction criteria specified in 

paragraphs (h)(9)(ii)(A) and (h)(9)(ii)(B) of this section. In conducting the VVT 

system demonstration tests, the manufacturer may use computer modifications to 

cause the VVT system to operate at the malfunction limit. To do so, the 

manufacturer must be able to demonstrate that the computer modifications 

produce test results equivalent to an induced hardware malfunction.

(I) For each of the testing requirements of this paragraph (l)(3)(ii), if the 

manufacturer has established that only a functional check is required because no 
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failure or deterioration of the specific tested system could cause an engine’s 

emissions to exceed the applicable emissions thresholds, the manufacturer is not 

required to perform a demonstration test; however the manufacturer is required to 

provide the data and/or engineering analyses used to determine that only a 

functional test of the system(s) is required.

(iii) Required testing for all engines.

(A) Other emission control systems. The manufacturer must conduct 

demonstration tests for all other emission control components (e.g., hydrocarbon 

traps, adsorbers) designed and calibrated to a malfunction limit based on an 

emissions threshold based on the requirements of paragraph (i)(4) of this section.

(B) For each of the testing requirements of paragraph (l)(3)(iii)(A) of this section, 

if the manufacturer has established that only a functional check is required 

because no failure or deterioration of the specific tested system could result in an 

engine’s emissions exceeding the applicable emissions thresholds, the 

manufacturer is not required to perform a demonstration test; however, the 

manufacturer is required to provide the data and/or engineering analysis used to 

determine that only a functional test of the system(s) is required.

(iv) The manufacturer may electronically simulate deteriorated components but 

shall not make any engine control unit modifications when performing 

demonstration tests unless approved by the Administrator. All equipment necessary 

to duplicate the demonstration test must be made available to the Administrator 

upon request.

(4) Testing protocol

(i) Preconditioning. The manufacturer must use an applicable cycle for 

preconditioning test engines prior to conducting each of the emission tests required 

by paragraph (l)(3) of this section. The manufacturer may perform a single 

additional preconditioning cycle, identical to the initial one, after a 20-minute hot 

soak but must demonstrate that such an additional cycle is necessary to stabilize the 

emissions control system. A practice of requiring a cold soak prior to conducting 

preconditioning cycles is not permitted.

(ii) Test sequence.

(A) The manufacturer must set individually each system or component on the test 

engine at the malfunction criteria limit prior to conducting the applicable 

preconditioning cycle(s). If a second preconditioning cycle is permitted in 

accordance with paragraph (l)(4)(i) of this section, the manufacturer may adjust 

the system or component to be tested before conducting the second 

preconditioning cycle. The manufacturer shall not replace, modify, or adjust the 

system or component after the last preconditioning cycle has been completed.
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(B) After preconditioning, the test engine must be operated over the applicable 

cycle to allow for the initial detection of the tested system or component 

malfunction. This test cycle may be omitted from the testing protocol if it is 

unnecessary. If required by the monitoring strategy being tested, a cold soak may 

be performed prior to conducting this test cycle.

(C) The test engine must then be operated over the applicable exhaust emissions 

test.

(iii) A manufacturer required to test more than one test engine according to 

paragraph (l)(2)(iii) of this section may use internal calibration sign-off test 

procedures (e.g., forced cool downs, less frequently calibrated emission analyzers) 

instead of official test procedures to obtain the emission test data required by this 

paragraph (l) of this section for all but one of the required test engines. The 

manufacturer may elect this option if the data from the alternative test procedure are 

representative of official emissions test results. A manufacturer using this option is 

still responsible for meeting the malfunction criteria specified in paragraphs (g) 

through (i) of this section if and when emissions tests are performed in accordance 

with official test procedures.

(iv) The manufacturer may request approval to use an alternative testing protocol 

for demonstration of MIL activation if the engine dynamometer emission test cycle 

does not allow all of a given monitor’s enable conditions to be satisfied. The

manufacturer may request the use of an alternative engine dynamometer test cycle 

or the use of chassis testing to demonstrate proper MIL activation. To do so, the 

manufacturer must demonstrate the technical necessity for using an alternative test 

cycle and the degree to which the alternative test cycle demonstrates that in-use 

operation with the malfunctioning component will result in proper MIL activation.

(5) Evaluation protocol. Full OBD engine ratings, as defined by paragraph (o)(1) of 

this section, shall be evaluated according to the following protocol:

(i) For all tests conducted as required by paragraph (l) of this section, the MIL must 

activate before the end of the first engine start portion of the applicable test.

(ii) If the MIL activates prior to emissions exceeding the applicable malfunction 

criteria limits specified in paragraphs (g) through (i), no further demonstration is 

required. With respect to the misfire monitor demonstration test, if the manufacturer 

has elected to use the minimum misfire malfunction criteria of one percent as 

allowed in paragraphs (g)(2)(ii)(B), if applicable, and (h)(2)(ii)(B) of this section, 

no further demonstration is required provided the MIL activates with engine misfire 

occurring at the malfunction criteria limit.

(iii) If the MIL does not activate when the system or component is set at its 

malfunction criteria limit(s), the criteria limit(s) or the OBD system is not 

acceptable.
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(A) Except for testing of the catalyst or DPF system, if the MIL first activates 

after emissions exceed the applicable malfunction criteria specified in paragraphs 

(g) through (i) of this section, the test engine shall be retested with the tested 

system or component adjusted so that the MIL will activate before emissions 

exceed the applicable malfunction criteria specified in paragraphs (g) through (i) 

of this section. If the component cannot be so adjusted because an alternative fuel 

or emission control strategy is used when a malfunction is detected (e.g., open 

loop fuel control used after an oxygen sensor malfunction is detected), the test 

engine shall be retested with the component adjusted to the worst acceptable limit 

(i.e., the applicable OBD monitor indicates that the component is performing at or 

slightly better than the malfunction criteria limit). When tested with the 

component so adjusted, the MIL must not activate during the test and the engine 

emissions must be below the applicable malfunction criteria specified in 

paragraphs (g) through (i) of this section.

 

(B) In testing the catalyst or DPF system, if the MIL first activates after emissions 

exceed the applicable emissions threshold(s) specified in paragraphs (g) and (h), 

the tested engine shall be retested with a less deteriorated catalyst or DPF system 

(i.e., more of the applicable engine out pollutants are converted or trapped). For 

the OBD system to be approved, testing shall be continued until the MIL activates 

with emissions below the applicable thresholds of paragraphs (g) and (h) of this 

section, or the MIL activates with emissions within a range no more than 20 

percent below the applicable emissions thresholds and 10 percent or less above 

those emissions thresholds.

(iv) If an OBD system is determined to be unacceptable by the criteria of this 

paragraph (l)(5) of this section, the manufacturer may recalibrate and retest the 

system on the same test engine. In such a case, the manufacturer must confirm, by 

retesting, that all systems and components that were tested prior to the recalibration 

and are affected by it still function properly with the recalibrated OBD system.

(6) Confirmatory testing.

(i) The Administrator may perform confirmatory testing to verify the emission test 

data submitted by the manufacturer as required by this paragraph (l) of this section 

comply with its requirements and the malfunction criteria set forth in paragraphs (g) 

through (i) of this section. Such confirmatory testing is limited to the test engine(s) 

required by paragraph (l)(2) of this section.

(ii) To conduct this confirmatory testing, the Administrator may install 

appropriately deteriorated or malfunctioning components (or simulate them) in an 

otherwise properly functioning test engine of an engine rating represented by the 

demonstration test engine in order to test any of the components or systems required 

to be tested by paragraph (l) of this section. The manufacturer shall make available, 

if requested, an engine and all test equipment (e.g., malfunction simulators, 

deteriorated components) necessary to duplicate the manufacturer’s testing. Such a 

request from the Administrator shall occur within six months of reviewing and 
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approving the demonstration test engine data submitted by the manufacturer for the 

specific engine rating.

(7) Catalyst aging

(i) Diesel catalysts. For purposes of determining the catalyst malfunction limits for 

the monitoring required by paragraphs (g)(5)(ii)(A), (g)(5)(ii)(B), and (g)(6)(ii)(A) 

of this section, where those catalysts are monitored individually, the manufacturer 

must use a catalyst deteriorated to the malfunction criteria using methods 

established by the manufacturer to represent real world catalyst deterioration under 

normal and malfunctioning engine operating conditions. For purposes of 

determining the catalyst malfunction limits for the monitoring required by 

paragraphs (g)(5)(ii)(A), (g)(5)(ii)(B), and (g)(6)(ii)(A) of this section, where those 

catalysts are monitored in combination with other catalysts, the manufacturer must 

submit their catalyst system aging and monitoring plan to the Administrator as part 

of their certification documentation package. The plan must include the description, 

emission control purpose, and location of each component, the monitoring strategy 

for each component and/or combination of components, and the method for

determining the applicable malfunction criteria including the deterioration/aging 

process.

(ii) Gasoline catalysts. For the purposes of determining the catalyst system 

malfunction criteria in paragraph (h)(6)(ii) of this section, the manufacturer must 

use a catalyst system deteriorated to the malfunction criteria using methods 

established by the manufacturer to represent real world catalyst deterioration under 

normal and malfunctioning operating conditions. The malfunction criteria must be 

established by using a catalyst system with all monitored and unmonitored 

(downstream of the sensor utilized for catalyst monitoring) catalysts simultaneously 

deteriorated to the malfunction criteria except for those engines that use fuel shutoff 

to prevent over-fueling during engine misfire conditions. For such engines, the 

malfunction criteria must be established by using a catalyst system with all 

monitored catalysts simultaneously deteriorated to the malfunction criteria while 

unmonitored catalysts shall be deteriorated to the end of the engine’s useful life.

(m) Certification documentation requirements.

(1) When submitting an application for certification of an engine, the manufacturer 

must submit the following documentation. If any of the items listed here are 

standardized for all of the manufacturer’s engines, the manufacturer may, for each 

model year, submit one set of documents covering the standardized items for all of its 

engines.

(i) For the required documentation that is not standardized across all engines, the 

manufacturer may be allowed to submit documentation for certification from one 

engine that is representative of other engines. All such engines shall be considered 

to be part of an OBD certification documentation group. To represent the OBD 

group, the chosen engine must be certified to the most stringent emissions standards 
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and OBD monitoring requirements and cover all of the emissions control devices 

for the engines in the group and covered by the submitted documentation. Such 

OBD groups must be approved in advance of certification.

(ii) Upon approval, one or more of the documentation requirements of this 

paragraph (m) of this section may be waived or modified if the information required 

is redundant or unnecessarily burdensome to generate.

(iii) To the extent possible, the certification documentation must use SAE J1930 (as 

specified in paragraph (k)(1) of this section) or SAE J2403 (as specified in 

paragraph (k)(1) of this section) terms, abbreviations, and acronyms as specified in 

paragraph (k)(1) of this section.

(2) Unless otherwise specified, the following information must be submitted as part 

of the certification application and prior to receiving a certificate.

(i) A description of the functional operation of the OBD system including a 

complete written description for each monitoring strategy that outlines every step in 

the decision-making process of the monitor. Algorithms, diagrams, samples of data, 

and/or other graphical representations of the monitoring strategy shall be included 

where necessary to adequately describe the information.

(ii) A table including the following information for each monitored component or 

system (either computer-sensed or computer-controlled) of the emissions control 

system:

(A) Corresponding diagnostic trouble code.

(B) Monitoring method or procedure for malfunction detection.

(C) Primary malfunction detection parameter and its type of output signal.

(D) Malfunction criteria limits used to evaluate output signal of primary 

parameter.

(E) Other monitored secondary parameters and conditions (in engineering units) 

necessary for malfunction detection.

(F) Monitoring time length and frequency of monitoring events.

(G) Criteria for storing a diagnostic trouble code.

(H) Criteria for activating a malfunction indicator light.

(I) Criteria used for determining out-of-range values and input component 

rationality checks.
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(iii) Whenever possible, the table required by paragraph (m)(2)(ii) of this section 

shall use the following engineering units:

(A) Degrees Celsius for all temperature criteria.

(B) KiloPascals (KPa) for all pressure criteria related to manifold or atmospheric 

pressure.

(C) Grams (g) for all intake air mass criteria.

(D) Pascals (Pa) for all pressure criteria related to evaporative system vapor 

pressure.

(E) Miles per hour (mph) for all vehicle speed criteria.

(F) Relative percent (%) for all relative throttle position criteria (as defined in 

SAE J1979 or SAE J1939 (both as specified in paragraph (k)(1) of this section)).

(G) Voltage (V) for all absolute throttle position criteria (as defined in SAE J1979 

or SAE J1939 (both as specified in paragraph (k)(1) of this section)).

(H) Per crankshaft revolution (/rev) for all changes per ignition event based 

criteria (e.g., g/rev instead of g/stroke or g/firing).

 

(I) Per second (/sec) for all changes per time based criteria (e.g., g/sec).

(J) Percent of nominal tank volume (%) for all fuel tank level criteria.

(iv) A logic flowchart describing the step-by-step evaluation of the enable criteria 

and malfunction criteria for each monitored emission related component or system.

(v) Emissions test data, a description of the testing sequence (e.g., the number and 

types of preconditioning cycles), approximate time (in seconds) of MIL activation 

during the test, diagnostic trouble code(s) and freeze frame information stored at the 

time of detection, corresponding test results (e.g. SAE J1979 (as specified in 

paragraph (k)(1) of this section) Mode/Service $06, SAE J1939 (as specified in 

paragraph (k)(1) of this section) Diagnostic Message 8 (DM8)) stored during the 

test, and a description of the modified or deteriorated components used for 

malfunction simulation with respect to the demonstration tests specified in 

paragraph (l) of this section. The freeze frame data are not required for engines 

termed “Extrapolated OBD” engines.

(vi) For gasoline engines, data supporting the misfire monitor, including:

(A) The established percentage of misfire that can be tolerated without damaging 

the catalyst over the full range of engine speed and load conditions.
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(B) Data demonstrating the probability of detection of misfire events by the 

misfire monitoring system over the full engine speed and load operating range for 

the following misfire patterns: random cylinders misfiring at the malfunction 

criteria established in paragraph (h)(2)(ii)(B) of this section, one cylinder 

continuously misfiring, and paired cylinders continuously misfiring.

(C) Data identifying all disablement of misfire monitoring that occurs during the 

FTP. For every disablement that occurs during the cycles, the data shall identify: 

when the disablement occurred relative to the driver’s trace, the number of engine 

revolutions during which each disablement was present, and which disable 

condition documented in the certification application caused the disablement.

(D) Manufacturers are not required to use the durability demonstration engine to 

collect the misfire data required by paragraph (m)(2)(vi) of this section.

(vii) Data supporting the limit for the time between engine starting and attaining the 

designated heating temperature for after-start heated catalyst systems.

(viii) Data supporting the criteria used to detect a malfunction of the fuel system, 

EGR system, boost pressure control system, catalyst, NOx adsorber, DPF, cold start 

emission reduction strategy, secondary air, evaporative system, VVT system, 

exhaust gas sensors, and other emission controls that causes emissions to exceed the 

applicable malfunction criteria specified in paragraphs (g) through (i) of this 

section. For diesel engine monitors required by paragraphs (g) and (i) of this section 

that are required to indicate a malfunction before emissions exceed an emission 

threshold based on any applicable standard (e.g., 2.5 times any of the applicable 

standards), the test cycle and standard determined by the manufacturer to be the 

most stringent for each applicable monitor in accordance with paragraph (f)(1) of 

this section.

(ix) A list of all electronic powertrain input and output signals (including those not 

monitored by the OBD system) that identifies which signals are monitored by the 

OBD system. For input and output signals that are monitored as comprehensive 

components, the listing shall also identify the specific diagnostic trouble code for 

each malfunction criteria (e.g., out-of-range low, out-of-range high, open circuit, 

rationality low, rationality high).

(x) A written description of all parameters and conditions necessary to begin 

closed-loop/feedback control of emission control systems (e.g., fuel system, boost 

pressure, EGR flow, SCR reductant delivery, DPF regeneration, fuel system 

pressure).

(xi) A written identification of the communication protocol utilized by each engine 

for communication with a scan tool (model years 2010 through 2012) or an SAE 

J1978 or SAE J1939 (both as specified in paragraph (k)(1) of this section) scan tool 

(model years 2013 and later).
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(xii) For model years 2013 and later, a pictorial representation or written description 

of the diagnostic connector location including any covers or labels.

(xiii) A written description of the method used by the manufacturer to meet the 

requirements of paragraph (i)(2) of this section (crankcase ventilation system 

monitoring) including diagrams or pictures of valve and/or hose connections.

(xiv) Build specifications provided to engine purchasers or chassis manufacturers 

detailing all specifications or limitations imposed on the engine purchaser relevant 

to OBD requirements or emissions compliance (e.g., cooling system heat rejection 

rates, allowable MIL locations, connector location specifications). A description of 

the method or copies of agreements used to ensure engine purchasers or chassis 

manufacturers will comply with the OBD and emissions relevant build 

specifications (e.g., signed agreements, required audit/evaluation procedures).

(xv) Any other information determined by the Administrator to be necessary to 

demonstrate compliance with the requirements of this section.

(3) In addition to the documentation required by paragraphs (m)(1) and (m)(2) of this 

section, a manufacturer making use of paragraph (a)(5) of this section must submit 

the following information with their application for certification.

(i) A detailed description of how the OBD system meets the intent of § 86.010-18.

(ii) A detailed description of why the manufacturer has chosen not to design the 

OBD system to meet the requirements of § 86.010-18 and has instead designed the 

OBD system to meet the applicable California OBD requirements.

(iii) A detailed description of any deficiencies granted by the California staff and 

any concerns raised by California staff. A copy of a California Executive Order 

alone will not be considered acceptable toward meeting this requirement. This 

description shall also include, to the extent feasible, a plan with timelines for 

resolving deficiencies and/or concerns.

(n) Deficiencies.

Changes below are intended to align alternative fuel engines requirements 

with those for engines used with hybrid powertrain systems and with the 

California requirements for alternative fuel engines. They also clarify 

that the waiver of a monitoring requirement for alternative fuel engines 

and engines used with hybrid powertrains is not a deficiency. 

(1) Upon application by the manufacturer, the Administrator may accept an OBD 

system as compliant even though specific requirements are not fully met. Such 

compliances without meeting specific requirements, or deficiencies, will be granted 

only if compliance is infeasible or unreasonable considering such factors as, but not 

limited to: Technical feasibility of the given monitor and lead time and production 
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cycles including phase-in or phase-out of engines or vehicle designs and programmed 

upgrades of computers. Unmet requirements shall not be carried over from the 

previous model year except where unreasonable hardware or software modifications 

are necessary to correct the deficiency, and the manufacturer has demonstrated an 

acceptable level of effort toward compliance as determined by the Administrator. 

Furthermore, EPA will not accept any deficiency requests that include the complete 

lack of a major diagnostic monitor (“major” diagnostic monitors being those for 

exhaust aftertreatment devices, oxygen sensor, air-fuel ratio sensor, NOx sensor,

engine misfire, evaporative leaks, and diesel EGR, if equipped), with the possible 

exception of the special provisions for alternative fueled engines. For 2013 through 

2019 model-year alternative fueled heavy-duty engines (e.g., natural gas, liquefied 

petroleum gas, methanol, ethanol) and engines used with any hybrid powertrain 

system as defined in § 86-010-02, manufacturers must at least comply with the 

monitoring requirements set forth in § 1971.1(d)(7.5.2) Title 13, California Code of 

Regulations. Such alternative fueled heavy-duty engines and engines used with 

hybrid powertrain systems will not be treated as having received any deficiencies 

with respect to this paragraph (n). may request the Administrator to waive specific 

monitoring requirements of this section for which monitoring may not be reliable 

with respect to the use of the alternative fuel. At a minimum, alternative fuel engines 

must be equipped with an OBD system meeting OBD requirements to the extent 

feasible as approved by the Administrator.

(2) In the event the manufacturer seeks to carry-over a deficiency from a past model 

year to the current model year, the manufacturer must re-apply for approval to do so. 

In considering the request to carry-over a deficiency, the Administrator shall consider 

the manufacturer’s progress towards correcting the deficiency. The Administrator 

may not allow manufacturers to carry over monitoring system deficiencies for more 

than two model years unless it can be demonstrated that substantial engine hardware 

modifications and additional lead time beyond two years are necessary to correct the 

deficiency.

(3) A deficiency shall not be granted retroactively (i.e., after the engine has been 

certified).

Changes that follow in paragraph (o) are also intended to align 

requirements for alternative fueled engines with those that apply to 

engines used with hybrid powertrain systems 

(o) Implementation schedule. Except as specifically provided for in this paragraph (o) 

for small volume manufacturers, and alternative fueled engines, and engines used with 

hybrid powertrain systems, the requirements of this section must be met according to 

the following provisions:

(1) For model years 2010 through 2012
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(i) Full OBD. The manufacturer must implement an OBD system meeting the 

applicable requirements of § 86.010-18 on one engine rating within one engine 

family of the manufacturer’s product line. This “Full OBD” rating will be known as 

the “OBD parent” rating. The OBD parent rating must be chosen, unless otherwise 

approved by the Administrator, as the rating having the highest weighted projected 

U.S. sales within the engine family having the highest weighted projected U.S. 

sales, with U.S. sales being weighted by the useful life of the engine rating.

(ii) Extrapolated OBD. For all other engine ratings within the engine family from 

which the OBD parent rating has been selected, the manufacturer must implement 

an OBD system meeting the applicable requirements of § 86.010-18 except that the 

OBD system is not required to detect a malfunction prior to exceeding the emission 

thresholds shown in Table 1 of paragraph (g) and Table 2 of paragraph (h) of this 

section. These “Extrapolated OBD” engines will be known as the “OBD child”

ratings. On these OBD child ratings, rather than detecting a malfunction prior to 

exceeding the emission thresholds, the manufacturer must submit a plan for 

Administrator review and approval that details the engineering evaluation the 

manufacturer will use to establish the malfunction criteria for the OBD child 

ratings. The plan must demonstrate both the use of good engineering judgment in 

establishing the malfunction criteria, and robust detection of malfunctions, 

including consideration of differences of base engine, calibration, emission control 

components, and emission control strategies.

(iii) Engine families other than those from which the parent and child ratings have 

been selected, are not subject to the requirements of this section.

(iv) Small volume manufacturers, as defined in § 86.094-14(b)(1) and (2) and as 

determined using 2010 model year sales, are exempt from the requirements of this § 

86.010-18, unless model year 2011 or model year 2012 sales exceed 20,000 units.

This change specifically exempts engines used with hybrid powertrain 

systems from compliance with HD OBD requirements through the 2012 

model-year

(v) Engines certified as alternative fueled engines and engines used with hybrid 

powertrain systems are exempt from the requirements of this § 86.010-18.

(2) For model years 2013 through 2015

(i) OBD groups. The manufacturer shall define one or more OBD groups to cover 

all engine ratings in all engine families. The manufacturer must submit a grouping 

plan for Administrator review and approval detailing the OBD groups and the 

engine families and engine ratings within each group for a given model year.

(ii) Full OBD.
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(A) For all model year 2010 through 2012 “Full OBD” and “Extrapolated OBD”

engine ratings, the manufacturer must implement an OBD system meeting the 

applicable requirements of this section.

(B) On one engine rating within each of the manufacturer’s OBD groups, the 

manufacturer must implement an OBD system meeting the applicable 

requirements of this section. These “Full OBD” ratings will be known as the 

“OBD parent” ratings. The OBD parent rating for each OBD group shall be 

chosen, unless otherwise approved by the Administrator, as the rating having the 

highest weighted projected U.S. sales within the OBD group, with U.S. sales 

being weighted by the useful life of the engine rating.

(iii) Extrapolated OBD. For all other engine ratings within each OBD group, the 

manufacturer must implement an OBD system meeting the requirements of this 

section except that the OBD system is not required to detect a malfunction prior to 

exceeding the emission thresholds shown in Table 1 of paragraph (g) and Table 2 of 

paragraph (h) of this section. These extrapolated OBD engines will be known as the 

“OBD child” ratings. On these OBD child ratings, rather than detecting a 

malfunction prior to exceeding the emission thresholds, the manufacturer must 

submit a plan for Administrator review and approval that details the engineering 

evaluation the manufacturer will use to establish the malfunction criteria for the 

OBD child ratings. The plan must demonstrate both the use of good engineering 

judgment in establishing the malfunction criteria, and robust detection of 

malfunctions, including consideration of differences of base engine, calibration, 

emission control components, and emission control strategies.

(iv) Engines certified as alternative fueled engines shall meet, to the extent feasible, 

the requirements specified in paragraph (i)(3) of this § 86.010-18. Additionally, 

such engines shall monitor the NOx aftertreatment system on engines so equipped 

and detect a malfunction if:

(A) The NOx aftertreatment system has no detectable amount of NOx

aftertreatement capability (i.e., NOx catalyst conversion or NOx adsorption).

(B) The NOx aftertreatment substrate is completely destroyed, removed, or 

missing.

(C) The NOx aftertreatment assembly is replaced with a straight pipe.

(3) For model years 2016 through 2018

(i) OBD groups. The manufacturer shall define one or more OBD groups to cover 

all engine ratings in all engine families. The manufacturer must submit a grouping 

plan for Administrator review and approval detailing the OBD groups and the 

engine families and engine ratings within each group for a given model year.
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(ii) Full OBD. The manufacturer must implement an OBD system meeting the 

applicable requirements of this section on all engine ratings in all engine families.

(iii) Engines certified as alternative fueled engines shall meet, to the extent feasible, 

the requirements specified in paragraph (i)(3) of this § 86.010-18. Additionally, 

such engines shall monitor the NOx aftertreatment system on engines so equipped 

and detect a malfunction if:

(A) The NOx aftertreatment system has no detectable amount of NOx

aftertreatement capability (i.e., NOx catalyst conversion or NOx adsorption).

(B) The NOx aftertreatment substrate is completely destroyed, removed, or 

missing.

(C) The NOx aftertreatment assembly is replaced with a straight pipe.

The changes below specify that alternative fuel engines and engines 

used with hybrid powertrain systems begin compliance with the 2020 

model-year and provide engine manufacturers with protection from

OBD non-compliance related to or attributable to hybrid powertrain 

systems through the 2022 model-year. The three additional years 

2020-2022 are provided to allow for an opportunity to refine hybrid 

powertrain system integration and diagnostic performance based on inuse experience. 

(4) For model years 2019 and later. (i) The manufacturer must implement an OBD 

system meeting the applicable requirements of § 86.010-18 on all engines except

alternative fuel engines and engines used with hybrid powertrain systems which must 

implement an OBD system meeting the applicable requirements of §86.010-18 no 

later than the 2020 model-year.

(p) In-use compliance standards. For monitors required to indicate a malfunction before 

emissions exceed a certain emission threshold (e.g., 2.5 times any of the applicable 

standards):

(1) For model years 2010 through 2012.

(i) On the full OBD rating (i.e., the parent rating) as defined in paragraph (o)(1) of 

this section, separate in-use emissions thresholds shall apply. These thresholds are 

determined by doubling the applicable thresholds as shown in Table 1 of paragraph 

(g) and Table 2 of paragraph (h) of this section. The resultant thresholds apply only 

in-use and do not apply for certification or selective enforcement auditing.

(ii) The extrapolated OBD ratings (i.e., the child ratings) as defined in paragraph 

(o)(1) of this section shall not be evaluated against emissions levels for purposes of

OBD compliance in-use.
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(iii) Only the test cycle and standard determined and identified by the manufacturer 

at the time of certification in accordance with paragraph (f) of this section as the 

most stringent shall be used for the purpose of determining OBD system 

noncompliance in-use.

(iv) An OBD system shall not be considered noncompliant solely due to a failure or 

deterioration mode of a monitored component or system that could not have been 

reasonably foreseen to occur by the manufacturer or which is related to or 

attributable to use of a certified engine with a hybrid powertrain system.

(2) For model years 2013 through 2015.

(i) On the full OBD ratings as defined in paragraph (o)(2) of this section, separate 

in-use emissions thresholds shall apply. These thresholds are determined by 

doubling the applicable thresholds as shown in Table 1 of paragraph (g) and Table 2 

of paragraph (h) of this section. The resultant thresholds apply only in-use and do 

not apply for certification or selective enforcement auditing.

(ii) The extrapolated OBD ratings as defined in paragraph (o)(2) of this section shall 

not be evaluated against emissions levels for purposes of OBD compliance in-use.

(iii) Only the test cycle and standard determined and identified by the manufacturer 

at the time of certification in accordance with paragraph (f) of this section as the 

most stringent shall be used for the purpose of determining OBD system 

noncompliance in-use.

(iv) For monitors subject to meeting the minimum in-use monitor performance ratio 

of 0.100 in paragraph (d)(1)(ii), the OBD system shall not be considered 

noncompliant unless a representative sample indicates the in-use ratio is below 

0.050.

(v) An OBD system shall not be considered noncompliant solely due to a failure or

deterioration mode of a monitored component or system that could not have been 

reasonably foreseen to occur by the manufacturer or which is related to or 

attributable to use of a certified engine with a hybrid powertrain system.

(3) For model years 2016 through 2018.

(i) On the engine ratings tested according to (l)(2)(iii) of this section, the 

certification emissions thresholds shall apply in-use.

(ii) On the manufacturer’s remaining engine ratings, separate in-use emissions 

thresholds shall apply. These thresholds are determined by doubling the applicable 

thresholds as shown in Table 1 of paragraph (g) and Table 2 of paragraph (h) of this 

section. The resultant thresholds apply only in-use and do not apply for certification 

or selective enforcement auditing.
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(iii) An OBD system shall not be considered noncompliant solely due to a failure or 

deterioration mode of a monitored component or system that could not have been 

reasonably foreseen to occur by the manufacturer or which is related to or 

attributable to use of a certified engine with a hybrid powertrain system

.

.

(4) For model years 2019 and later.

(i) On all engine ratings, the certification emissions thresholds shall apply in-use.

(ii) An OBD system shall not be considered noncompliant solely due to a failure or 

deterioration mode of a monitored component or system that could not have been 

reasonably foreseen to occur by the manufacturer. Through the 2022 model-year,

an OBD system will not be considered noncompliant as the result of any failure or 

deterioration mode of a monitored component or system that is related to or 

attributable to a hybrid powertrain system.

[74 FR 8369, Feb. 24, 2009]

 
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§ 86.010-38 Maintenance instructions.

(a) The manufacturer shall furnish or cause to be furnished to the purchaser of each new 

motor vehicle (or motor vehicle engine) subject to the standards prescribed in § 86.099-

8, § 86.004-9, § 86.004-10, or § 86.004-11, as applicable, written instructions for the 

proper maintenance and use of the vehicle (or engine), by the purchaser consistent with 

the provisions of § 86.004-25, which establishes what scheduled maintenance the 

Administrator approves as being reasonable and necessary.

(1) The maintenance instructions required by this section shall be in clear, and to the 

extent practicable, nontechnical language.

(2) The maintenance instructions required by this section shall contain a general 

description of the documentation which the manufacturer will require from the 

ultimate purchaser or any subsequent purchaser as evidence of compliance with the 

instructions.

(b) Instructions provided to purchasers under paragraph (a) of this section shall specify 

the performance of all scheduled maintenance performed by the manufacturer on 

certification durability vehicles and, in cases where the manufacturer performs less 

maintenance on certification durability vehicles than the allowed limit, may specify the 

performance of any scheduled maintenance allowed under § 86.004-25.

(c) Scheduled emission-related maintenance in addition to that performed under § 

86.004-25(b) may only be recommended to offset the effects of abnormal in-use 

operating conditions, except as provided in paragraph (d) of this section. The 

manufacturer shall be required to demonstrate, subject to the approval of the 

Administrator, that such maintenance is reasonable and technologically necessary to 

assure the proper functioning of the emission control system. Such additional 

recommended maintenance shall be clearly differentiated, in a form approved by the 

Administrator, from that approved under § 86.004-25(b).

(d) Inspections of emission-related parts or systems with instructions to replace, repair, 

clean, or adjust the parts or systems if necessary, are not considered to be items of 

scheduled maintenance which insure the proper functioning of the emission control 

system. Such inspections, and any recommended maintenance beyond that approved by 

the Administrator as reasonable and necessary under paragraphs (a), (b), and (c) of this 

section, may be included in the written instructions furnished to vehicle owners under 

paragraph (a) of this section: Provided, That such instructions clearly state, in a form 

approved by the Administrator, that the owner need not perform such inspections or 

recommended maintenance in order to maintain the emissions defect and emissions 

performance warranty or manufacturer recall liability.

(e) The manufacturer may choose to include in such instructions an explanation of any 

distinction between the useful life specified on the label, and the emissions defect and 

emissions performance warranty period. The explanation must clearly state that the 

useful life period specified on the label represents the average period of use up to 
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retirement or rebuild for the engine family represented by the engine used in the 

vehicle. An explanation of how the actual useful lives of engines used in various 

applications are expected to differ from the average useful life may be included. The 

explanation(s) shall be in clear, non-technical language that is understandable to the 

ultimate purchaser.

(f) If approved by the Administrator, the instructions provided to purchasers under 

paragraph (a) of this section shall indicate what adjustments or modifications, if any, 

are necessary to allow the vehicle to meet applicable emission standards at elevations 

above 4,000 feet, or at elevations of 4,000 feet or less.

(g) Emission control diagnostic service information. (1) Manufacturers are subject to 

the provisions of this paragraph (g) beginning in the 1996 model year for manufacturers 

of light-duty vehicles and light-duty trucks, and beginning in the 2005 model year for 

manufacturers of heavy-duty vehicles and heavy-duty engines weighing 14,000 pounds 

gross vehicle weight (GVW) and less that are subject to the OBD requirements of this 

part.

(2) General requirements

(i) Manufacturers shall furnish or cause to be furnished to any person engaged in 

the repairing or servicing of motor vehicles or motor vehicle engines, or the 

Administrator upon request, any and all information needed to make use of the onboard diagnostic system and such other information, including instructions for 

making emission-related diagnoses and repairs, including but not limited to service 

manuals, technical service bulletins, recall service information, bi-directional 

control information, and training information, unless such information is protected 

by section 208(c) of the Act as a trade secret. No such information may be withheld 

under section 208(c) of the Act if that information is provided (directly or 

indirectly) by the manufacturer to franchised dealers or other persons engaged in 

the repair, diagnosing, or servicing of motor vehicles or motor vehicle engines.

(ii) Definitions. The following definitions apply for this paragraph (g):

(A) Aftermarket service provider means any individual or business engaged in the 

diagnosis, service, and repair of a motor vehicle or engine, who is not directly 

affiliated with a manufacturer or manufacturer-franchised dealership.

(B) Bi-directional control means the capability of a diagnostic tool to send 

messages on the data bus that temporarily overrides the module's control over a 

sensor or actuator and gives control to the diagnostic tool operator. Bi-directional 

controls do not create permanent changes to engine or component calibrations.

(C) Data stream information means information (i.e., messages and parameters) 

originated within the vehicle by a module or intelligent sensors (i.e., a sensor that 

contains and is controlled by its own module) and transmitted between a network 

of modules and/or intelligent sensors connected in parallel with either one or more 
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communication wires. The information is broadcast over the communication 

wires for use by the OBD system to gather information on emissions-related 

components or systems and from other vehicle modules that may impact 

emissions, including but not limited to systems such as chassis or transmission. 

For the purposes of this section, data stream information does not include engine 

calibration-related information, or any data stream information from systems or 

modules that do not impact emissions.

(D) Emissions-related information means any information related to the diagnosis, 

service, and repair of emissions-related components. Emissions-related 

information includes, but is not limited to, information regarding any system, 

component or part of a vehicle that controls emissions and any system, 

component and/or part associated with the powertrain system, including, but not 

limited to:

(1) The engine, the fuel system and ignition system,

(2) Information for any system, component or part that is likely to impact emissions, 

such as transmission systems, and any other information specified by the 

Administrator to be relevant to the diagnosis and repair of an emissions-related 

problem; and

(3) Any other information specified by the Administrator to be relevant for the 

diagnosis and repair of an emissions-related failure found through the inspection and 

maintenance program after such finding has been communicated to the affected 

manufacturer(s).

(E) Emissions-related training information means any information-related training 

or instruction for the purpose of the diagnosis, service, and repair of emissionsrelated components.

(F) Enhanced service and repair information means information which is specific 

for an original equipment manufacturer's brand of tools and equipment. This 

includes computer or anti-theft system initialization information necessary for the 

completion of any emissions-related repair on motor vehicles that employ integral 

vehicle security systems.

(G) Equipment and tool company means a registered automotive equipment or 

software company either public or private that is engaged in, or plans to engage 

in, the manufacture of automotive scan tool reprogramming equipment or 

software.

(H) Generic service and repair information means information which is not 

specific for an original equipment manufacturer's brand of tools and equipment.

(I) Indirect information means any information that is not specifically contained 

in the service literature, but is contained in items such as tools or equipment 
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provided to franchised dealers (or others). This includes computer or anti-theft 

system initialization information necessary for the completion of any emissionsrelated repair on motor vehicles that employ integral vehicle security systems.

(J) Intermediary means any individual or entity, other than an original equipment 

manufacturer, which provides service or equipment to aftermarket service 

providers.

(K) Manufacturer-franchised dealership means any service provider with which a 

manufacturer has a direct business relationship.

(L) Third-party information provider means any individual or entity, other than an 

original equipment manufacturer, who consolidates manufacturer service 

information and makes this information available to aftermarket service providers.

(M) Third-party training provider means any individual or entity, other than an 

original equipment manufacturer who develops and/or delivers instructional and 

educational material for automotive training courses.

(3) Information dissemination. By December 24, 2003, each manufacturer was 

required to provide or cause to be provided to the persons specified in paragraph 

(g)(2)(i) of this section and to any other interested parties a manufacturer-specific 

World Wide Web site containing the information specified in paragraph (g)(2)(i) of 

this section for 1996 and later model year vehicles which have been offered for sale; 

this requirement does not apply to indirect information, including the information 

specified in paragraphs (g)(12) through (g)(16) of this section. Upon request and 

approval of the Administrator, manufacturers who can demonstrate significant 

hardship in complying with this provision by December 26, 2003, may request an 

additional six months lead time to meet this requirement. Each manufacturer Web site 

shall:

(i) Provide access in full-text to all of the information specified in paragraph (g)(5) 

of this section.

(ii) Be updated at the same time as manufacturer-franchised dealership World Wide 

Web sites;

(iii) Provide users with a description of the minimum computer hardware and 

software needed by the user to access that manufacturer's information (e.g., 

computer processor speed and operating system software). This description shall 

appear when users first log-on to the home page of the manufacturer Web site.

(iv) Provide Short-Term (24 to 72 hours), Mid-Term (30 day period), and LongTerm (365 day period) Web site subscription options to any person specified in 

paragraph (g)(2)(i) of this section whereby the user will be able to access the site, 

search for the information, and purchase, view and print the information at a fair 

and reasonable cost as specified in paragraph (g)(7) of this section for each of the 
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subscription options. In addition, for each of the subscription options, 

manufacturers are required to make their entire site accessible for the respective 

period of time and price. In other words, a manufacturer may not limit any or all of 

the subscription options to just one make or one model.

(v) Allow the user to search the manufacturer Web site by various topics including 

but not limited to model, model year, key words or phrases, etc., while allowing 

ready identification of the latest vehicle calibration. Manufacturers who do not use 

model year to classify their vehicles in their service information may use an 

alternate vehicle delineation such as body series. Any manufacturer utilizing this 

flexibility shall create a cross-reference to the corresponding model year and 

provide this cross-reference on the manufacturer Web site home page.

(vi) Provide accessibility using common, readily available software and shall not 

require the use of software, hardware, viewers, or browsers that are not readily 

available to the general public. Manufacturers shall also provide hyperlinks to any 

plug-ins, viewers or browsers (e.g., Adobe Acrobat or Netscape) needed to access 

the manufacturer Web site.

(vii) Allow simple hyper-linking to the manufacturer Web site from government 

Web sites and automotive-related Web sites.

(viii) Allow access to the manufacturer Web site with no limits on the modem speed 

by which aftermarket service providers or other interested parties can connect to the 

manufacturer Web site.

(ix) Possess sufficient server capacity to allow ready access by all users and have 

sufficient capacity to assure that all users may obtain needed information without 

undue delay.

(x) Correct or delete broken Web links on a weekly basis.

(xi) Allow for Web site navigation that does not require a user to return to the 

manufacturer home page or a search engine in order to access a different portion of 

the site.

(xii) Allow users to print out any and all of the materials required to be made 

available on the manufacturer Web site including the ability to print it at the user's 

location.

(4) Small volume provisions for information dissemination.

(i) Manufacturers with annual sales of less than 5,000 vehicles had until June 28, 

2004 to launch their individual Web sites as required by paragraph (g)(3) of this 

section.
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(ii) Manufacturers with annual sales of less than 1,000 vehicles may, in lieu of 

meeting the requirement of paragraph (g)(3) of this section, request the 

Administrator to approve an alternative method by which the required emissionsrelated information can be obtained by the persons specified in paragraph (g)(2)(i) 

of this section.

(5) Required information. All information relevant to the diagnosis and completion of 

emissions-related repairs shall be posted on manufacturer Web sites. This excludes 

indirect information specified in paragraphs (g)(6) and (g)(12) through (g)(16) of this 

section. To the extent that this information does not already exist in some form for 

their manufacturer franchised dealerships, manufacturers are required to develop and 

make available the information required by this section to both their manufacturer 

franchised dealerships and the aftermarket. The required information includes, but is 

not limited to:

(i) Manuals, including subsystem and component manuals developed by a 

manufacturer's third party supplier that are made available to manufacturer

franchised dealerships, technical service bulletins (TSBs), recall service 

information, diagrams, charts, and training materials. Manuals and other such 

service information from third party suppliers are not required to be made available 

in full-text on manufacturer Web sites as described in paragraph (g)(3) of this 

section. Rather, manufacturers must make available on the manufacturer Web site 

as required by paragraph (g)(3) of this section an index of the relevant information 

and instructions on how to order such third party information. In the alternative, a 

manufacturer can create a link from its Web site to the Web site(s) of the third party 

supplier.

(ii) OBD system information which includes, but is not limited to, the following:

(A) A general description of the operation of each monitor, including a 

description of the parameter that is being monitored;

(B) A listing of all typical OBD diagnostic trouble codes associated with each 

monitor;

(C) A description of the typical enabling conditions (either generic or monitorspecific) for each monitor (if equipped) to execute during vehicle operation, 

including, but not limited to, minimum and maximum intake air and engine 

coolant temperature, vehicle speed range, and time after engine startup. In 

addition, manufacturers shall list all monitor-specific OBD drive cycle 

information for all major OBD monitors as equipped including, but not limited to, 

catalyst, catalyst heater, oxygen sensor, oxygen sensor heater, evaporative system, 

exhaust gas re-circulation (EGR), secondary air, and air conditioning system. 

Additionally, for diesel vehicles under 14,000 pounds. GVWR which also 

perform misfire, fuel system and comprehensive component monitoring under 

specific driving conditions (i.e., non-continuous monitoring; as opposed to spark 

ignition engines that monitor these systems under all conditions or continuous 
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monitoring), the manufacturer shall make available monitor-specific drive cycles. 

Any manufacturer who develops generic drive cycles, either in addition to, or 

instead of, monitor-specific drive cycles shall also make these available in fulltext on manufacturer Web sites;

(D) A listing of each monitor sequence, execution frequency and typical duration;

(E) A listing of typical malfunction thresholds for each monitor;

(F) For OBD parameters for specific vehicles that deviate from the typical 

parameters, the OBD description shall indicate the deviation and provide a 

separate listing of the typical values for those vehicles;

(G) Identification and scaling information necessary to interpret and understand 

data available to a generic scan tool through “mode 6,” pursuant to SAE J1979 (as 

specified in paragraph (g)(17) of this section).

(H) Algorithms, look-up tables, or any values associated with look-up tables are 

not required to be made available.

(iii) Any information regarding any system, component, or part of a vehicle 

monitored by the OBD system that could in a failure mode cause the OBD system 

to illuminate the malfunction indicator light (MIL);

(iv) Any information on other systems that can effect the emission system within a 

multiplexed system (including how information is sent between emission-related 

system modules and other modules on a multiplexed bus);

(v) Manufacturer-specific emissions-related diagnostic trouble codes (DTCs) and 

any related service bulletins, trouble shooting guides, and/or repair procedures 

associated with these manufacturer-specific DTCs; and

(vi) Information regarding how to obtain the information needed to perform 

reinitialization of any vehicle computer or anti-theft system following an emissionsrelated repair.

(6) Anti-theft system initialization information. Computer or anti-theft system 

initialization information and/or related tools necessary for the proper installation of 

on-board computers or necessary for the completion of any emissions-related repair 

on motor vehicles that employ integral vehicle security systems or the repair or 

replacement of any other emission-related part shall be made available at a fair and 

reasonable cost to the persons specified in paragraph (g)(2)(i) of this section.

(i) Except as provided under paragraph (g)(6)(ii) of this section, manufacturers must 

make this information available to persons specified in paragraph (g)(2)(i) of this 

section, such that such persons will not need any special tools or manufacturerspecific scan tools to perform the initialization. Manufacturers may make such 
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information available through, for example, generic aftermarket tools, a passthrough device, or inexpensive manufacturer-specific cables.

(ii) A manufacturer may request Administrator approval for an alternative means to 

re-initialize vehicles for some or all model year vehicles through the 2007 model 

year by September 26, 2003. The Administrator shall approve the request only after 

the following conditions have been met:

(A) The manufacturer must demonstrate that the availability of such information 

to aftermarket service providers would significantly increase the risk of vehicle 

theft.

(B) The manufacturer must make available a reasonable alternative means to 

install or repair computers, or to otherwise repair or replace an emission-related 

part.

(C) Any alternative means proposed by a manufacturer cannot require aftermarket 

technicians to use a manufacturer franchised dealership to obtain information or 

special tools to re-initialize the anti-theft system. All information must come 

directly from the manufacturer or a single manufacturer-specified designee.

(D) Any alternative means proposed by a manufacturer must be available to 

aftermarket technicians at a fair and reasonable price.

(E) Any alternative must be available to aftermarket technicians within twentyfour hours of the initial request.

(F) Any alternative must not require the purchase of a special tool or tools, 

including manufacturer-specific tools, to complete this repair. Alternatives may 

include lease of such tools, but only for appropriately minimal cost.

(G) In lieu of leasing their manufacturer-specific tool to meet this requirement, a 

manufacturer may also release the necessary information to equipment and tool 

manufacturers for incorporation into aftermarket scan tools. Any manufacturer 

choosing this option must release the information to equipment and tool 

manufacturers within 60 days of Administrator approval. Manufacturers may also 

comply with this requirement using SAE J2534 (as specified in paragraph (g)(17) 

of this section) for some or all model years through model year 2007.

(7) Cost of required information. (i) All information required to be made available by 

this section shall be made available at a fair and reasonable price. In determining 

whether a price is fair and reasonable, consideration may be given to relevant factors, 

including, but not limited to, the following:

(A) The net cost to the manufacturer-franchised dealerships for similar 

information obtained from manufacturers, less any discounts, rebates, or other 

incentive programs.
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(B) The cost to the manufacturer for preparing and distributing the information, 

excluding any research and development costs incurred in designing and 

implementing, upgrading or altering the onboard computer and its software or any 

other vehicle part or component. Amortized capital costs for the preparation and 

distribution of the information may be included.

(C) The price charged by other manufacturers for similar information.

(D) The price charged by manufacturers for similar information prior to the 

launch of manufacturer Web sites.

(E) The ability of aftermarket technicians or shops to afford the information.

(F) The means by which the information is distributed;

(G) The extent to which the information is used, which includes the number of 

users, and frequency, duration, and volume of use.

(H) Inflation.

(ii) By August 25, 2003, each manufacturer was required to submit to the 

Administrator a request for approval of their pricing structure for their Web sites 

and amounts to be charged for the information required to be made available under 

paragraphs (g)(3) and (g)(5) of this section. Subsequent to the approval of the 

manufacturer Web site pricing structure, manufacturers shall notify the 

Administrator upon the increase in price of any one or all of the subscription 

options of 20 percent or more above the previously-approved price, taking inflation 

into account.

(A) The manufacturer shall submit a request to the Administrator that sets forth a 

detailed description of the pricing structure and amounts, and support for the 

position that the pricing structure and amounts are fair and reasonable by 

addressing, at a minimum, each of the factors specified in paragraph (g)(7)(i) of 

this section.

(B) The Administrator will act upon the request within 180 days following receipt 

of a complete request or following receipt of any additional information requested 

by the Administrator.

(C) The Administrator may decide not to approve, or to withdraw approval for a 

manufacturer's pricing structure and amounts based on a conclusion that this 

pricing structure and/or amounts are not, or are no longer, fair and reasonable, by 

sending written notice to the manufacturer explaining the basis for this decision.

(D) In the case of a decision by the Administrator not to approve or to withdraw 

approval, the manufacturer shall within three months following notice of this 
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decision, obtain Administrator approval for a revised pricing structure and 

amounts by following the approval process described in this paragraph (g)(7)(ii).

(8) Unavailable information. Any information which is not provided at a fair and

reasonable price shall be considered unavailable, in violation of these regulations and 

section 202(m)(5) of the Clean Air Act.

(9) Third-party information providers. By December 24, 2003, manufacturers shall, 

for model year 2004 and later vehicles and engines, make available to third-party 

information providers as defined in paragraph (g)(2)(ii) of this section with whom 

they engage in licensing or business arrangements;

(i) The required emissions-related information as specified in paragraph (g)(5) of 

this section either:

(A) Directly in electronic format such as diskette or CD-ROM using nonproprietary software, in English; or

(B) Indirectly via a Web site other than that required by paragraph (g)(3) of this 

section;

(ii) For any manufacturer who utilizes an automated process in their manufacturerspecific scan tool for diagnostic fault trees, the data schema, detail specifications, 

including category types/codes and vehicle codes, and data format/content structure 

of the diagnostic trouble trees.

(iii) Manufacturers can satisfy the requirement of paragraph (g)(9)(ii) of this section 

by making available diagnostic trouble trees on their manufacturer Web sites in 

full-text.

(iv) Manufacturers are not responsible for the accuracy of the information 

distributed by third parties. However, where manufacturers charge information 

intermediaries for information, whether through licensing agreements or other 

arrangements, manufacturers are responsible for inaccuracies contained in the 

information they provide to third-party information providers.

(10) Required emissions-related training information. By December 24, 2003, for 

emissions-related training information, manufacturers were required to:

(i) Video tape or otherwise duplicate and make available for sale on manufacturer 

Web sites within 30 days after transmission any emissions-related training courses 

provided to manufacturer franchised dealerships via the Internet or satellite 

transmission;

(ii) Provide on the manufacturer Web site an index of all emissions-related training 

information available for purchase by aftermarket service providers for 1994 and 

newer vehicles. For model years subsequent to 2003, the required information must 
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be made available for purchase within 3 months of model introduction and then 

must be made available at the same time it is made available to manufacturer 

franchised dealerships, whichever is earlier. The index shall describe the title of the 

course or instructional session, the cost of the video tape or duplicate, and 

information on how to order the item(s) from the manufacturer Web site. All of the 

items available must be shipped within 24 hours of the order being placed and are to 

be made available at a fair and reasonable price as described in paragraph (g)(7) of 

this section. Manufacturers unable to meet the 24 hour shipping requirement under 

circumstances where orders exceed supply and additional time is needed by the 

distributor to reproduce the item being ordered, may exceed the 24 hour shipping 

requirement, but in no instance can take longer than 14 days to ship the item.

(iii) Provide access to third-party training providers as defined in paragraph 

(g)(2)(ii) of this section all emission-related training courses transmitted via satellite 

or Internet offered to their manufacturer franchised dealerships. Manufacturers may 

not charge unreasonable up-front fees to third-party training providers for this 

access, but may require a royalty, percentage, or other arranged fee based on peruse enrollment/subscription basis. Manufacturers may take reasonable steps to 

protect any copyrighted information and are not required to provide this information 

to parties that do not agree to such steps.

(11) Timeliness and maintenance of information dissemination

(i) General requirements. Subsequent to the initial launch of the manufacturer's 

Web site, manufacturers must make the information required under paragraph (g)(5) 

of this section available on their Web site within six months of model introduction, 

or at the same time it is made available to manufacturer franchised dealerships, 

whichever is earlier. After this six-month period, the information must be available 

and updated on the manufacturer Web site at the same time that the updated 

information is made available to manufacturer franchised dealerships, except as 

otherwise specified in this section.

(ii) Archived information. Beginning with the 1996 model year, manufacturers must 

maintain the required information on their Web sites in full-text as defined in 

paragraph (g)(5) of this section for a minimum of 15 years after model introduction. 

Subsequent to this fifteen year period, manufacturers may archive the information 

in the manufacturer's format of choice and provide an index of the archived 

information on the manufacturer Web site and how it can be obtained by interested 

parties. Manufacturers shall index their available information with a title that 

adequately describes the contents of the document to which it refers. Manufacturers 

may allow for the ordering of information directly from their Web site, or from a 

Web site hyperlinked to the manufacturer Web site. In the alternative, 

manufacturers shall list a phone number and address where aftermarket service 

providers can call or write to obtain the desired information. Manufacturers must 

also provide the price of each item listed, as well as the price of items ordered on a 

subscription basis. To the extent that any additional information is added or 

changed for these model years, manufacturers shall update the index as appropriate. 
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Manufacturers will be responsible for ensuring that all information, including 

information that is distributed through information distributors, is provided within 

one regular business day of receiving the order. Items that are less than 20 pages 

(e.g. technical service bulletins) shall be faxed, if requested, to the requestor and 

manufacturers are required to deliver the information overnight if requested and 

paid for by the ordering party. Archived information must be made available on 

demand and at a fair and reasonable price.

(12) Reprogramming information.

(i) For model years 1996 and later, manufacturers shall make available to the 

persons specified in paragraph (g)(2)(i) of this section all emissions-related 

recalibration or reprogramming events (including driveability reprogramming 

events that may affect emissions) in the format of its choice at the same time they 

are made available to manufacturer franchised dealerships. This requirement takes 

effect on September 25, 2003, and within 3 months of model introduction for all 

new model years.

 

(ii) For model years 1996 and later manufacturers shall provide persons specified in 

paragraph (g)(2)(i) of this section with an efficient and cost-effective method for 

identifying whether the calibrations on vehicles are the latest to be issued. This 

requirement takes effect on September 25, 2003, and within 3 months of model 

introduction for all new model years.

(iii) For all 2004 and later OBD vehicles equipped with reprogramming capability, 

manufacturers shall comply with SAE J2534 (as specified in paragraph (g)(17) of 

this section). Any manufacturer who cannot comply with SAE J2534 in model year 

2004 may request one year additional lead time from the Administrator.

(iv) For model years 2004 and later, manufacturers shall make available to 

aftermarket service providers the necessary manufacturer-specific software 

applications and calibrations needed to initiate pass-through reprogramming. This 

software shall be able to run on a standard personal computer that utilizes standard 

operating systems as specified in SAE J2534 (as specified in paragraph (g)(17) of 

this section).

(v) For model years prior to 2004, manufacturers may use SAE J2534 (as specified 

in paragraph (g)(17) of this section) as described above, provided they make 

available to the aftermarket any additional required hardware (i.e. cables). 

Manufacturers may not require the purchase or use of a manufacturer-specific scan 

tool to receive or use this additional hardware. Manufacturers must also make 

available the necessary manufacturer-specific software applications and calibrations 

needed to initiate pass-through reprogramming. Manufacturers must also make 

available to equipment and tool companies any information needed to develop 

aftermarket equivalents of the manufacturer-specific hardware.
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(vi) Manufacturers may take any reasonable business precautions necessary to 

protect proprietary business information and are not required to provide this 

information to any party that does not agree to these reasonable business 

precautions. The requirement to make hardware available and to release the 

information to equipment and tool companies takes effect on September 25, 2003, 

and within 3 months of model introduction for all new model years.

(vii) Manufacturers who cannot comply with paragraphs (g)(12)(v) and (g)(12)(vi) 

of this section shall make available to equipment and tool companies by September 

25, 2003 the following information necessary for reprogramming the Electronic 

Control Unit (ECU):

(A) The physical hardware requirements for reprogramming events or tools (e.g. 

system voltage requirements, cable terminals/pins, connections such as RS232 or 

USB, wires, etc.).

(B) ECU data communication (e.g. serial data protocols, transmission speed or 

baud rate, bit timing requirements, etc.).

(C) Information on the application physical interface (API) or layers (descriptions 

for procedures such as connection, initialization, performing and verifying 

programming/download, and termination).

(D) Vehicle application information or any other related service information such 

as special pins and voltages for reprogramming events or additional vehicle 

connectors that require enablement and specifications for the enablement.

(E) Information that describes what interfaces or combinations of interfaces are 

used to deliver calibrations from database media (e.g. PC using CDROM to the 

reprogramming device e.g. scan tool or black box).

(viii) A manufacturer can propose an alternative to the requirements of paragraph 

(g)(12)(vii) of this section for how aftermarket service providers can reprogram an 

ECU. The Administrator will approve this alternative if the manufacturer 

demonstrates all of the following:

(A) That it cannot comply with paragraph (g)(12)(v) of this section for the 

vehicles subject to the alternative plan;

(B) That a very small percentage of its vehicles in model years prior to 2004 

cannot be reprogrammed with the provisions described in paragraph (g)(12)(v) of 

this section, or that releasing the information to tool companies would likely not 

result in this information being incorporated into aftermarket tools; and

(C) That aftermarket service providers will be able to reprogram promptly at a 

reasonable cost.
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(ix) In meeting the requirements of paragraphs (g)(12)(v) through (g)(12)(vii) of 

this section, manufacturers may take any reasonable business precautions necessary 

to protect proprietary business information and are not required to provide this 

information to any party that does not agree to these reasonable business 

precautions.

(13) Generic and enhanced information for scan tools. By September 25, 2003, 

manufacturers shall make available to equipment and tool companies all generic and 

enhanced service information including bi-directional control and data stream 

information as defined in paragraph (g)(2)(ii) of this section. This requirement applies 

for 1996 and later model year vehicles.

(i) The information required by paragraph (g)(13) of this section shall be provided 

electronically using common document formats to equipment and tool companies 

with whom they have appropriate licensing, contractual, and/or confidentiality 

arrangements. To the extent that a central repository for this information (e.g. the 

TEK-NET library developed by the Equipment and Tool Institute) is used to 

warehouse this information, the Administrator shall have free unrestricted access. In 

addition, information required in paragraph (g)(13) of this section shall be made 

available to equipment and tool companies who are not otherwise members of any 

central repository and shall have access if the non-members have arranged for the 

appropriate licensing, contractual and/or confidentiality arrangements with the 

manufacturer and/or a central repository.

(ii) In addition to the generic and enhanced information defined in paragraph 

(g)(2)(ii) of this section, manufacturers shall also make available the following 

information necessary for developing generic diagnostic scan tools:

(A) The physical hardware requirements for data communication (e.g. system 

voltage requirements, cable terminals/pins, connections such as RS232 or USB, 

wires, etc.),

(B) ECU data communication (e.g. serial data protocols, transmission speed or 

baud rate, bit timing requirements, etc.),

(C) Information on the application physical interface (API) or layers. (i.e., 

processing algorithms or software design descriptions for procedures such as 

connection, initialization, and termination),

(D) Vehicle application information or any other related service information such 

as special pins and voltages or additional vehicle connectors that require 

enablement and specifications for the enablement.

(iii) Any manufacturer who utilizes an automated process in its manufacturerspecific scan tool for diagnostic fault trees shall make available to equipment and 

tool companies the data schema, detail specifications, including category 
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types/codes and vehicle codes, and data format/content structure of the diagnostic 

trouble trees.

(iv) Manufacturers can satisfy the requirement of paragraph (g)(13)(iii) of this 

section by making available diagnostic trouble trees on their manufacturer Web 

sites in full-text.

(14) Availability of manufacturer-specific scan tools. Manufacturers shall make 

available for sale to the persons specified in paragraph (g)(2)(i) of this section their 

own manufacturer-specific diagnostic tools at a fair and reasonable cost. These tools 

shall also be made available in a timely fashion either through the manufacturer Web 

site or through a manufacturer-designated intermediary. Manufacturers who develop 

different versions of one or more of their diagnostic tools that are used in whole or in 

part for emission-related diagnosis and repair shall insure that all emission-related 

diagnosis and repair information is available for sale to the aftermarket at a fair and 

reasonable cost. Manufacturers shall provide technical support to aftermarket service 

providers for the tools described in this section, either themselves or through a third 

party of its choice. Factors for determining fair and reasonable cost include, but are 

not limited to:

(i) The net cost to the manufacturer's franchised dealerships for similar tools 

obtained from manufacturers, less any discounts, rebates, or other incentive 

programs;

(ii) The cost to the manufacturer for preparing and distributing the tools, excluding 

any research and development costs;

(iii) The price charged by other manufacturers of similar sizes for similar tools;

(iv) The capabilities and functionality of the manufacturer tool;

(v) The means by which the tools are distributed;

(vi) Inflation.

(vii) The ability of aftermarket technicians and shops to afford the tools.

(15) Changing content of manufacturer-specific scan tools. Manufacturers who opt to 

remove non-emissions related content from their manufacturer-specific scan tools and 

sell them to the persons specified in paragraph (g)(2)(i) of this section shall adjust the 

cost of the tool accordingly lower to reflect the decreased value of the scan tool. All 

emissions-related content that remains in the manufacturer-specific tool shall be 

identical to the information that is contained in the complete version of the 

manufacturer-specific tool. Any manufacturer who wishes to implement this option 

must request approval from the Administrator prior to the introduction of the tool into 

commerce.
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(16) Special tools.

(i) Manufacturers who have developed special tools to extinguish the malfunction 

indicator light (MIL) for Model Years 1994 through 2003 shall make available the

necessary information to equipment and tool companies to design a comparable 

generic tool. This information was required to be made available to equipment and 

tool companies no later than September 25, 2003.

(ii) Manufacturers are prohibited from requiring special tools to extinguish the 

malfunction indicator light (MIL) beginning with Model Year 2004.

(17) Reference materials. Manufacturers shall conform with the following Society of 

Automotive Engineers (SAE) standards. These documents are incorporated by 

reference, see § 86.1. Anyone may inspect copies at the U.S. EPA or at the National 

Archives and Records Administration (NARA). For information on the availability of 

this material at U.S. EPA, NARA, or the standard making body directly, refer to § 

86.1.

(i) SAE J1930, Revised May 1998. For Web-based delivery of service information, 

manufacturers shall comply with this industry standard. This recommended practice 

standardizes various terms, abbreviations, and acronyms associated with on-board 

diagnostics. Manufacturers shall comply with SAE J1930 beginning with Model 

Year 2004.

(ii) SAE J1979, Revised September 1997. For identification and scaling information 

necessary to interpret and understand data available to a generic scan tool through 

“mode 6,” manufacturers shall comply with this industry standard. This 

recommended practice describes the implementation of the diagnostic test modes 

for emissions-related test data. Manufacturers shall comply with this industry 

standard beginning with Model Year 2004.

(iii) SAE J2284-3, May 2001. For allowing ECU and equipment and tool 

manufacturers to satisfy the needs of multiple end users with minimum 

modification to a basic ECU design, manufacturers shall comply with this industry 

standard which establishes standard ECU physical layer, data link layer, and media 

design criteria. Manufacturers may comply with SAE J2284-3 beginning with 

model year 2003 and shall comply with SAE J2284-3 beginning with model year 

2008.

(iv) SAE J2534, February 2002. For pass-through reprogramming capabilities, 

manufacturers shall comply with this industry standard which provides technical 

specifications and information that manufacturers must supply to equipment and 

tool companies to develop aftermarket pass-through reprogramming tools. 

Manufacturers shall comply with SAE J2534 beginning with model year 2004.
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(18) Reporting requirements. Manufacturers shall provide to the Administrator 

reports on an annual basis within 30 days of the end of the calendar year and upon 

request of the Administrator, that describe the performance of their individual Web 

sites. These annual reports shall be submitted to the Administrator electronically 

utilizing non-proprietary software in the format as agreed to by the Administrator and 

the manufacturers. Manufacturers may request Administrator approval to report on 

parameters other than those described below if the manufacturer can demonstrate that 

those alternate parameters will provide sufficient and similar information for the 

Administrator to effectively evaluate the manufacturer Web site. These annual reports 

shall include, at a minimum, monthly measurements of the following parameters:

(i) Total successful requests (measured in number of files including graphic 

interchange formats (GIFs) and joint photographic expert group (JPEG) images, 

i.e., electronic images such as wiring or other diagrams or pictures). This is defined 

as the total successful request counts of all the files which have been requested, 

including pages, graphics, etc.

(ii) Total failed requests (measured in number of files). This is defined as the total 

failed request counts of all the files which were requested but failed because they 

could not be found or were read-protected. This includes pages, graphics, etc.

(iii) Average data transferred per day (measured by bytes). This is defined as 

average amount of data transferred per day from one place to another.

(iv) Daily Summary (measured in number of files/pages by day of week). This is 

defined as the total number of requests each day of the week, over the time period 

given at the beginning of the report.

(v) Daily report (measured in number of files/pages by the day of the month). This 

is defined as how many requests there were in each day of a specific month.

(vi) Browser Summary (measured in number of files/pages by browser type, i.e., 

Netscape, Internet Explorer). This is defined as the versions of a browser by vendor.

(vii) Any other information deemed necessary by the Administrator to determine 

the adequacy of a manufacturer Web site.

(19) Prohibited acts, liability and remedies. (i) It is a prohibited act for any person to 

fail to promptly provide or cause a failure to promptly provide information as 

required by this paragraph (g), or to otherwise fail to comply or cause a failure to 

comply with any provision of this paragraph (g).

(ii) Any person who fails or causes the failure to comply with any provision of this 

paragraph (g) is liable for a violation of that provision. A corporation is presumed 

liable for any violations of this subpart that are committed by any of its subsidiaries, 

affiliates or parents that are substantially owned by it or substantially under its 

control.
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(iii) Any person who violates a provision of this paragraph (g) shall be subject to a 

civil penalty of not more than $32,500 per day for each violation. This maximum 

penalty is shown for calendar year 2004. Maximum penalty limits for later years 

may be set higher based on the Consumer Price Index, as specified in 40 CFR part 

19. In addition, such person shall be liable for all other remedies set forth in Title II 

of the Clean Air Act, remedies pertaining to provisions of Title II of the Clean Air 

Act, or other applicable provisions of law.

(h) The manufacturer shall furnish or cause to be furnished to the purchaser of each 

new motor engine subject to the standards prescribed in § 86.004-10 or § 86.004-11, as 

applicable, the following:

(1) Instructions for all maintenance needed after the end of the useful life of the 

engine for critical emissions-related components as provided in § 86.004-25(b), 

including recommended practices for diagnosis, cleaning, adjustment, repair, and 

replacement of the component (or a statement that such component is maintenance 

free for the life of the engine) and instructions for accessing and responding to any 

emissions-related diagnostic codes that may be stored in on-board monitoring 

systems;

(2) A copy of the engine rebuild provisions contained in § 86.004-40.

(i) For each new diesel-fueled engine subject to the standards prescribed in § 86.007-

11, as applicable, the manufacturer shall furnish or cause to be furnished to the ultimate 

purchaser a statement that “This engine must be operated only with ultra low-sulfur 

diesel fuel (meeting EPA specifications for highway diesel fuel, including a 15 ppm 

sulfur cap).”

(j) The following provisions describe requirements related to emission control 

diagnostic service information for heavy-duty engines used in vehicles over 14,000 

pounds gross vehicle weight (GVW):

(1) Manufacturers of heavy-duty engines used in applications weighing more than 

14,000 pounds gross vehicle weight (GVW) that are subject to the applicable OBD 

requirements of this subpart A are subject to the provisions of this paragraph (j) 

beginning in the 2010 model year. The provisions of this paragraph (j) apply only to 

those heavy-duty engines subject to the applicable OBD requirements.

(2) Upon Administrator approval, manufacturers of vehicles may alternatively 

comply with all service information and tool provisions found in § 86.1808-01 that 

are applicable to 2001 and subsequent model year vehicles weighing less than 14,000 

pounds gross vehicle weight (GVW). Upon Administrator approval, manufacturers 

that produce engines for use in vehicles between 8,500 and 14,000 pounds may, for 

those engines, alternatively comply with all service information and tool provisions in 

§ 86.010-38(j) that are applicable to 2010 and subsequent model year vehicles over 
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14,000 pounds. Implementation dates must comply with the service information 

provision dates applicable to engines in vehicles between 8,500 and 14,000 pounds.

(3) General requirements.

(i) Manufacturers shall furnish or cause to be furnished to any person engaged in 

the repairing or servicing of heavy-duty engines, or the Administrator upon request, 

any and all information needed to make use of the on-board diagnostic system and 

such other information, including instructions for making emission-related 

diagnosis and repairs, including but not limited to service manuals, technical service 

bulletins, recall service information, bi-directional control information, and training 

information, unless such information is protected by section 208(c) as a trade secret. 

Manufacturers may take steps to restrict warranty and customer assurance plan 

information used only for the purpose of providing such manufacturer covered 

repairs to only those repair locations authorized by the manufacturer. No such 

information may be withheld under section 208(c) of the Act if that information is

provided (directly or indirectly) by the manufacturer to franchised dealers, 

authorized service networks, or other persons engaged in the repair, diagnosing, or 

servicing of heavy-duty engines.

(ii) Definitions. The following definitions apply for this paragraph (j):

(A) Aftermarket service provider means any individual or business engaged in the 

diagnosis, service, and repair of a heavy-duty engine, who is not directly affiliated 

with a manufacturer or manufacturer franchised dealership, or authorized service 

network.

(B) Authorized service network means a group of independent service and repair 

facilities that are recognized by engine manufacturers as being capable of 

performing repairs to factory specification, including warranty repair work.

(C) Bi-directional control means the capability of a diagnostic tool to send 

messages on the data bus that temporarily overrides the module's control over a 

sensor or actuator and gives control to the diagnostic tool operator. Bi-directional 

controls do not create permanent changes to engine or component calibrations.

This section has been modified to exempt hybrid powertrain systems 

from the data stream information requirements through the 2019 

model-year.

(D) Data stream information means information (i.e., messages and parameters) 

originated within the engine by a module or intelligent sensors (i.e., a sensor that 

contains and is controlled by its own module) and transmitted between a network 

of modules and/or intelligent sensors connected in parallel with either one or more 

communication wires. The information is broadcast over the communication 

wires for use by the OBD system to gather information on emissions-related 
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components or systems and from other engine modules that may impact 

emissions. For the purposes of this section, data stream information does not 

include engine calibration related information, or any data stream information 

from systems or modules that do not impact emissions including hybrid 

powertrain systems, as defined in § 86-.010-02, that are used in combination with 

certified engines through the 2019 model-year. 

This section has been modified to exempt hybrid powertrain systems 

from the service information requirements through the 2019 modelyear.

(E) Emissions-related information means any information related to the diagnosis, 

service, and repair of emissions-related components. Hybrid powertrain systems,

as defined in § 86-.010-02, that are used in combination with certified engines 

through the 2019 model-year are not considered emission-related components. 

Emissions-related information includes, but is not limited to, information 

regarding any system, component or part of an engine that controls emissions and 

that is part of the diagnostic strategy for an OBD monitor, but not limited to: The 

engine, the fuel system and ignition system; information for any system, 

component or part that is likely to impact emissions, and any other information 

specified by the Administrator to be relevant to the diagnosis and repair of an 

emissions-related problem; any other information specified by the Administrator 

to be relevant for the diagnosis and repair of an emissions-related failure found 

through an evaluation of vehicles in-use and after such finding has been 

communicated to the affected manufacturer(s).

(F) Emissions-related training information means any information related training 

or instruction for the purpose of the diagnosis, service, and repair of emissionsrelated components.

(G) Enhanced service and repair information means information which is specific 

for an original equipment manufacturer's brand of tools and equipment. This 

includes computer or anti-theft system initialization information necessary for the 

completion of any emissions-related repair on engines that employ integral 

security systems.

(H) Equipment and tool company means a registered equipment or software 

company either public or private that is engaged in, or plans to engage in, the 

manufacture of scan tool reprogramming equipment or software.

(I) Generic service and repair information means information which is not 

specific for an original equipment manufacturer's brand of tools and equipment.

(J) Indirect information means any information that is not specifically contained 

in the service literature, but is contained in items such as tools or equipment 

provided to franchised dealers or authorized service networks (or others). This 
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includes computer or anti-theft system initialization information necessary for the 

completion of any emissions-related repair on engines that employ integral 

security systems.

(K) Intermediary means any individual or entity, other than an original equipment 

manufacturer, which provides service or equipment to aftermarket service 

providers.

(L) Manufacturer franchised dealership means any service provider with which a 

manufacturer has a direct business relationship.

(M) Recalibration means the process of downloading to an engine's on-board 

computer emissions-related revisions of on-board computer application software 

and calibration parameters with default configurations. Recalibration is not 

dependent on the use of the vehicle identification number (VIN) in determining 

vehicle configuration.

(N) Reconfiguration means the process of enabling or adjusting engine features or 

engine parameters associated with such features to adapt a heavy-duty engine to a 

particular vehicle and/or application.

(O) Third party information provider means any individual or entity, other than an 

original equipment manufacturer, who consolidates manufacturer service 

information and makes this information available to aftermarket service providers.

(P) Third party training provider means any individual or entity, other than an 

original equipment manufacturer who develops and/or delivers instructional and 

educational material for training courses.

(4) Information dissemination. By July 1, 2010 each manufacturer shall provide or 

cause to be provided to the persons specified in paragraph (j)(3)(i) of this section and 

to any other interested parties a manufacturer-specific World Wide Web site 

containing the information specified in paragraph (j)(3)(i) of this section for 2010 and 

later model year engines which have been certified to the OBD requirements 

specified in § 86.010-18 and are offered for sale; this requirement does not apply to 

indirect information, including the information specified in paragraphs (j)(13) through 

(j)(17) of this section. Upon request and approval of the Administrator, manufacturers 

who can demonstrate significant hardship in complying with this provision by August 

27, 2009, may request an additional six months lead time to meet this requirement. 

Each manufacturer Web site shall:

 

(i) Provide access in full-text to all of the information specified in paragraph (j)(6) 

of this section.

(ii) Be updated at the same time as manufacturer franchised dealership or 

authorized service network World Wide Web sites.
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(iii) Provide users with a description of the minimum computer hardware and 

software needed by the user to access that manufacturer's information (e.g., 

computer processor speed and operating system software). This description shall 

appear when users first log-on to the home page of the manufacturer's Web site.

(iv) Upon Administrator approval, implement a range of time periods for online 

access to any person specified in paragraph (j)(3)(i) of this section whereby the user 

will be able to access the site, search for the information, and purchase, view and 

print the information at a fair and reasonable cost as specified in paragraph (j)(8) of 

this section for each of the options. In addition, for each of the range of time 

periods, manufacturers are required to make their entire site accessible for the 

respective period of time and price. In other words, a manufacturer may not limit 

Web site access to just one make or one model.

(v) Allow the user to search the manufacturer Web site by various topics including 

but not limited to model, model year, key words or phrases, etc., while allowing 

ready identification of the latest calibration. Manufacturers who do not use model 

year to classify their engines in their service information may use an alternate 

delineation such as body series. Any manufacturer utilizing this flexibility shall 

create a cross-reference to the corresponding model year and provide this crossreference on the manufacturer Web site home page.

(vi) Provide accessibility using common, readily available software and shall not 

require the use of software, hardware, viewers, or browsers that are not readily 

available to the general public. Manufacturers shall also provide hyperlinks to any 

plug-ins, viewers or browsers (e.g. Adobe Acrobat or Netscape) needed to access 

the manufacturer Web site.

(vii) Allow simple hyper-linking to the manufacturer Web site from Government 

Web sites and automotive-related Web sites.

(viii) Possess sufficient server capacity to allow ready access by all users and has 

sufficient capacity to assure that all users may obtain needed information without 

undue delay.

(ix) Correct or delete any reported broken Web links on a weekly basis.

(x) Allow for Web site navigation that does not require a user to return to the 

manufacturer home page or a search engine in order to access a different portion of 

the site.

(xi) Allow users to print out any and all of the materials required to be made 

available on the manufacturers Web site that can be reasonably printed on a 

standard printer, including the ability to print it at the user's location.
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(5) Small volume provisions for information dissemination. (i) Manufacturers with 

total annual sales of less than 5,000 engines shall have until July 1, 2011 to launch 

their individual Web sites as required by paragraph (j)(4) of this section.

(ii) Manufacturers with total annual sales of less than 1,000 engines may, in lieu of 

meeting the requirement of paragraph (j)(4) of this section, request the 

Administrator to approve an alternative method by which the required emissionsrelated information can be obtained by the persons specified in paragraph (j)(3)(i) 

of this section.

(6) Required information. All information relevant to the diagnosis and completion of 

emissions-related repairs shall be posted on manufacturer Web sites. This excludes 

indirect information specified in paragraphs (j)(7) and (j)(13) through (j)(17) of this 

section. To the extent that this information does not already exist in some form for 

their manufacturer franchised dealerships or authorized service networks, 

manufacturers are required to develop and make available the information required by 

this section to both their manufacturer franchised dealerships or authorized service 

networks and the aftermarket. The required information includes, but is not limited to:

(i) Manuals, including subsystem and component manuals developed by a 

manufacturer's third party supplier that are made available to manufacturer 

franchised dealerships or authorized service networks, technical service bulletins 

(TSBs), recall service information, diagrams, charts, and training materials. 

Informal recall service information such as engineering notes and/or sketches are 

not required to be made available as long as this information is not made available 

to manufacturer franchised dealerships or authorized service networks in the form 

of manuals. Manuals and other such service information from third party suppliers 

are not required to be made available in full-text on manufacturer Web sites as 

described in paragraph (j)(4) of this section. Rather, manufacturers must make 

available on the manufacturer Web site as required by paragraph (j)(4) of this 

section an index of the relevant information and instructions on how to order such 

information. In the alternate, a manufacturer can create a link from its Web site to 

the Web site(s) of the third party supplier.

(ii) OBD system information which includes, but is not limited to, the following:

(A) A general description of the operation of each monitor, including a 

description of the parameter that is being monitored;

(B) A listing of all typical OBD diagnostic trouble codes associated with each 

monitor;

(C) A description of the typical enabling conditions (either generic or monitorspecific) for each monitor (if equipped) to execute during engine operation, 

including, but not limited to, minimum and maximum intake air and engine 

coolant temperature, speed range, and time after engine startup. In addition, 

manufacturers shall list all monitor-specific OBD drive cycle information for all 
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major OBD monitors as equipped including, but not limited to, catalyst, catalyst 

heater, oxygen sensor, oxygen sensor heater, evaporative system, exhaust gas recirculation (EGR), secondary air, and air conditioning system. Additionally, for 

diesel engines which also perform misfire, fuel system and comprehensive 

component monitoring under specific driving conditions (i.e., non-continuous 

monitoring; as opposed to spark ignition engines that monitor these systems under 

all conditions or continuous monitoring), the manufacturer shall make available 

monitor-specific drive cycles for these monitors. Any manufacturer who develops 

generic drive cycles, either in addition to, or instead of, monitor-specific drive 

cycles shall also make these available in full-text on manufacturer Web sites;

(D) A listing of each monitor sequence, execution frequency and typical duration;

(E) A listing of typical malfunction thresholds for each monitor;

(F) For OBD parameters for specific engines that deviate from the typical 

parameters, the OBD description shall indicate the deviation and provide a 

separate listing of the typical values for those engines;

(G) Identification and scaling information necessary to interpret and understand 

data available through Diagnostic Message 8 pursuant to SAE J1939-73 (as 

specified in paragraph (j)(17) of this section), or through Service/Mode $06 

pursuant to SAE J1979 (as specified in paragraph (j)(17) of this section).

(H) Algorithms, look-up tables, or any values associated with look-up tables are 

not required to be made available.

(iii) Any information regarding any system, component, or part of a engine 

monitored by the OBD system that could in a failure mode cause the OBD system 

to illuminate the malfunction indicator light (MIL);

(iv) Manufacturer-specific emissions-related diagnostic trouble codes (DTCs) and 

any related service bulletins, troubleshooting guides, and/or repair procedures 

associated with these manufacturer-specific DTCs; and

(v) Information regarding how to obtain the information needed to perform 

reinitialization of any computer or anti-theft system following an emissions-related 

repair.

(7) Anti-theft System Initialization Information. Computer or anti-theft system 

initialization information and/or related tools necessary for the proper installation of 

on-board computers or necessary for the completion of any emissions-related repair 

on engines that employ integral security systems or the repair or replacement of any 

other emission-related part shall be made available at a fair and reasonable cost to the 

persons specified in paragraph (j)(3)(i) of this section.
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(i) Except as provided under paragraph (j)(7)(ii) of this section, manufacturers must 

make this information available to persons specified in paragraph (j)(3)(i) of this 

section, such that such persons will not need any special tools or manufacturerspecific scan tools to perform the initialization. Manufacturers may make such 

information available through, for example, generic aftermarket tools, a passthrough device, or inexpensive manufacturer specific cables.

(ii) A manufacturer may request Administrator approval for an alternative means to 

re-initialize engines for some or all model years through the 2013 model year by 

July 27, 2009. The Administrator shall approve the request only after the following 

conditions have been met:

(A) The manufacturer must demonstrate that the availability of such information 

to aftermarket service providers would significantly increase the risk of theft.

(B) The manufacturer must make available a reasonable alternative means to 

install or repair computers, or to otherwise repair or replace an emission-related 

part.

(C) Any alternative means proposed by a manufacturer cannot require aftermarket 

technicians to use a manufacturer franchised dealership or authorized service 

networks to obtain information or special tools to re-initialize the anti-theft 

system. All information must come directly from the manufacturer or a single 

manufacturer-specified designee.

(D) Any alternative means proposed by a manufacturer must be available to 

aftermarket technicians at a fair and reasonable price.

(E) Any alternative must be available to aftermarket technicians within twentyfour hours of the initial request.

(F) Any alternative must not require the purchase of a special tool or tools, 

including manufacturer-specific tools, to complete this repair. Alternatives may 

include lease of such tools, but only for appropriately minimal cost.

(G) In lieu of leasing their manufacturer-specific tool to meet this requirement, a 

manufacturer may also choose to release the necessary information to equipment 

and tool manufacturers for incorporation into aftermarket scan tools. Any 

manufacturer choosing this option must release the information to equipment and 

tool manufacturers within 60 days of Administrator approval.

(8) Cost of required information.

(i) All information required to be made available by this section, shall be made 

available at a fair and reasonable price. In determining whether a price is fair and 

reasonable, consideration may be given to relevant factors, including, but not 

limited to, the following:
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(A) The net cost to the manufacturer franchised dealerships or authorized service 

networks for similar information obtained from manufacturers, less any discounts, 

rebates, or other incentive programs;

(B) The cost to the manufacturer for preparing and distributing the information, 

excluding any research and development costs incurred in designing and 

implementing, upgrading or altering the onboard computer and its software or any 

other engine part or component. Amortized capital costs for the preparation and 

distribution of the information may be included;

(C) The price charged by other manufacturers for similar information;

(D) The price charged by manufacturers for similar information prior to the 

launch of manufacturer Web sites;

(E) The ability of the average aftermarket technician or shop to afford the 

information;

(F) The means by which the information is distributed;

(G) The extent to which the information is used, which includes the number of 

users, and frequency, duration, and volume of use; and

(H) Inflation.

(ii) Manufacturers must submit to EPA a request for approval of their pricing 

structure for their Web sites and amounts to be charged for the information required 

to be made available under paragraphs (j)(4) and (j)(6) of this section at least 180 

days in advance of the launch of the web site. Subsequent to the approval of the 

manufacturer Web site pricing structure, manufacturers shall notify EPA upon the 

increase in price of any one or all of the subscription options of 20 percent or more 

above the previously approved price, taking inflation into account.

(A) The manufacturer shall submit a request to EPA that sets forth a detailed 

description of the pricing structure and amounts, and support for the position that 

the pricing structure and amounts are fair and reasonable by addressing, at a 

minimum, each of the factors specified in paragraph (j)(8)(i) of this section.

(B) EPA will act upon on the request within180 days following receipt of a 

complete request or following receipt of any additional information requested by 

EPA.

(C) EPA may decide not to approve, or to withdraw approval for a manufacturer's 

pricing structure and amounts based on a conclusion that this pricing structure 

and/or amounts are not, or are no longer, fair and reasonable, by sending written 

notice to the manufacturer explaining the basis for this decision.
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(D) In the case of a decision by EPA not to approve or to withdraw approval, the 

manufacturer shall within three months following notice of this decision, obtain 

EPA approval for a revised pricing structure and amounts by following the 

approval process described in this paragraph.

(9) Unavailable information. Any information which is not provided at a fair and 

reasonable price shall be considered unavailable, in violation of these regulations and 

section 202(m)(5) of the Clean Air Act.

(10) Third party information providers. (i) By January 1, 2011 manufacturers shall, 

for model year 2010 and later engines, make available to third-party information 

providers as defined in paragraph (j)(3)(ii) of this section with whom they may wish 

to engage in licensing or business arrangements, the required emissions-related 

information as specified in paragraph (j)(6) of this section either:

(A) Directly in electronic format such as diskette or CD-ROM using nonproprietary software, in English; or

(B) Indirectly via a Web site other than that required by paragraph (j)(4) of this 

section

(ii) Manufacturers are not responsible for the accuracy of the information 

distributed by third parties. However, where manufacturers charge information 

intermediaries for information, whether through licensing agreements or other 

arrangements, manufacturers are responsible for inaccuracies contained in the 

information they provide to third party information providers.

(11) Required emissions-related training information. By January 1, 2011, for 

emissions-related training information, manufacturers shall:

(i) Video tape or otherwise duplicate and make available for sale on manufacturer 

Web sites within 30 days after transmission any emissions-related training courses 

provided to manufacturer franchised dealerships or authorized service networks via 

the Internet or satellite transmission. Manufacturers shall not be required to 

duplicate transmitted emissions-related training courses if anyone engaged in the 

repairing or servicing of heavy-duty engines has the opportunity to receive the 

Internet or satellite transmission, even if there is a cost associated with the 

equipment required to receive the transmission;

(ii) Provide on the manufacturer Web site an index of all emissions-related training 

information available for purchase by aftermarket service providers for 2010 and 

newer engines. The required information must be made available for purchase 

within 3 months of model introduction and then must be made available at the same 

time it is made available to manufacturer franchised dealerships or authorized 

service networks, whichever is earlier. The index shall describe the title of the 

course or instructional session, the cost of the video tape or duplicate, and 
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information on how to order the item(s) from the manufacturer Web site. All of the 

items available must be shipped within 3 business day of the order being placed and 

are to made available at a fair and reasonable price as described in paragraph (j)(8) 

of this section. Manufacturers unable to meet the 3 business day shipping 

requirement under circumstances where orders exceed supply and additional time is 

needed by the distributor to reproduce the item being ordered, may exceed the 3 

business day shipping requirement, but in no instance can take longer than 14 days 

to ship the item.

(12) Timeliness and maintenance of information dissemination. (i) Subsequent to the 

initial launch of the manufacturer's Web site, manufacturers must make the 

information required under paragraph (j)(6) of this section available on their Web site 

within six months of model introduction, or at the same time it is made available to 

manufacturer franchised dealerships or authorized service networks, whichever is 

earlier. After this six month period, the information must be available and updated on 

the manufacturer Web site at the same time that the updated information is made 

available to manufacturer franchised dealerships or authorized service networks, 

except as otherwise specified in this section.

(ii) Archived information. Manufacturers must maintain the required information on 

their Web sites in full-text as defined in paragraph (j)(6) of this section for a 

minimum of 15 years after model introduction. Subsequent to this fifteen year 

period, manufacturers may archive the information in the manufacturer's format of 

choice and provide an index of the archived information on the manufacturer Web 

site and how it can be obtained by interested parties. Manufacturers shall index their 

available information with a title that adequately describes the contents of the 

document to which it refers. Manufacturers may allow for the ordering of 

information directly from their Web site, or from a Web site hyperlinked to the 

manufacturer Web site. In the alternate, manufacturers shall list a phone number 

and address where aftermarket service providers can call or write to obtain the 

desired information. Manufacturers must also provide the price of each item listed, 

as well as the price of items ordered on a subscription basis. To the extent that any 

additional information is added or changed for these model years, manufacturers 

shall update the index as appropriate. Manufacturers will be responsible for 

ensuring that their information distributors do so within one regular business day of 

receiving the order. Items that are less than 20 pages (e.g. technical service 

bulletins) shall be faxed to the requestor and distributors are required to deliver the 

information overnight if requested and paid for by the ordering party. Archived 

information must be made available on demand and at a fair and reasonable price.

(13) Recalibration information. (i) Manufacturers shall make available to the persons 

specified in paragraph (j)(3)(i) of this section all emissions-related recalibration or 

reprogramming events (including driveability reprogramming events that may affect 

emissions) in the format of their choice at the same time they are made available to 

manufacturer franchised dealerships or authorized service networks. This requirement 

applies on July 1, 2013.
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(ii) Manufacturers shall provide persons specified in paragraph (j)(3)(i) of this 

section with an efficient and cost-effective method for identifying whether the 

calibrations on engines are the latest to be issued. This requirement applies on July 

1, 2013.

(iii) For all 2013 and later OBD engines equipped with reprogramming capability, 

manufacturers shall comply with either SAE J2534-1 (as specified in paragraph 

(j)(17) of this section), or the Technology and Maintenance Council's (TMC) 

Recommended Practice TMC RP 1210B (as specified in paragraph (j)(17) of this 

section).

(iv) For model years 2013 and later, manufacturers shall make available to 

aftermarket service providers the necessary manufacturer-specific software 

applications and calibrations needed to initiate pass-through reprogramming. This 

software shall be able to run on a standard personal computer that utilizes standard 

operating systems as specified in either SAE J2534-1 (as specified in paragraph 

(j)(17) of this section) or TMC RP 1210B (as specified in paragraph (j)(17) of this 

section).

(v) Manufacturers may take any reasonable business precautions necessary to 

protect proprietary business information and are not required to provide this 

information to any party that does not agree to these reasonable business 

precautions. The requirements to make hardware available and to release the 

information to equipment and tool companies apply on July 1, 2013, and within 3 

months of model introduction for all new model years.

(14) Generic and enhanced information for scan tools. By July 1, 2013, manufacturers 

shall make available to equipment and tool companies all generic and enhanced 

service information including bi-directional control and data stream information as 

defined in paragraph (j)(3(ii) of this section. This requirement applies for 2013 and 

later model year engines.

(i) The information required by this paragraph (j)(14) shall be provided 

electronically using common document formats to equipment and tool companies 

with whom they have appropriate licensing, contractual, and/or confidentiality 

arrangements. To the extent that a central repository for this information (e.g. the 

TEK-NET library developed by the Equipment and Tool Institute) is used to 

warehouse this information, the Administrator shall have free unrestricted access. In 

addition, information required by this paragraph (j)(14) shall be made available to 

equipment and tool companies who are not otherwise members of any central 

repository and shall have access if the non-members have arranged for the 

appropriate licensing, contractual and/or confidentiality arrangements with the 

manufacturer and/or a central repository.

(ii) In addition to the generic and enhanced information defined in paragraph 

(j)(3)(ii) of this section, manufacturers shall also make available the following 

information necessary for developing generic diagnostic scan tools:
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(A) The physical hardware requirements for data communication (e.g., system 

voltage requirements, cable terminals/pins, connections such as RS232 or USB, 

wires, etc.),

(B) Electronic Control Unit (ECU) data communication (e.g., serial data 

protocols, transmission speed or baud rate, bit timing requirements, etc.),

(C) Information on the application physical interface (API) or layers. (i.e., 

processing algorithms or software design descriptions for procedures such as 

connection, initialization, and termination),

(D) Engine application information or any other related service information such 

as special pins and voltages or additional connectors that require enablement and 

specifications for the enablement.

(iii) Any manufacturer who utilizes an automated process in their manufacturerspecific scan tool for diagnostic fault trees shall make available to equipment and 

tool companies the data schema, detail specifications, including category 

types/codes and codes, and data format/content structure of the diagnostic trouble 

trees.

(iv) Manufacturers can satisfy the requirement of paragraph (j)(14)(iii) of this 

section by making available diagnostic trouble trees on their manufacturer Web 

sites in full-text.

(v) Manufacturers shall make all required information available to the requesting 

equipment and tool company within 14 days after the request to purchase has been 

made unless the manufacturer requests Administrator approval to refuse to disclose 

such information to the requesting company or requests Administrator approval for 

additional time to comply. After receipt of a request and consultation with the 

affected parties, the Administrator shall either grant or refuse the petition based on 

the evidence submitted during the consultation process:

(A) If the evidence demonstrates that the engine manufacturer has a reasonably 

based belief that the requesting equipment and tool company could not produce 

safe and functionally accurate tools that would not cause damage to the engine, 

the petition for non-disclosure will be granted. Engine manufacturers are not 

required to provide data stream and bi-directional control information that would 

permit an equipment and tool company's products to modify an EPA-certified 

engine or transmission configuration.

(B) If the evidence does not demonstrate that the engine manufacturer has a 

reasonably-based belief that the requesting equipment and tool company could not 

produce safe and functionally accurate tools that would not cause damage to the 

engine, the petition for non-disclosure will be denied and the engine 
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manufacturer, as applicable, shall make the requested information available to the 

requesting equipment and tool company within 2 days of the denial.

(vi) If the manufacturer submits a request for Administrator approval for additional 

time, and satisfactorily demonstrates to the Administrator that the engine 

manufacturer is able to comply but requires additional time within which to do so, 

the Administrator shall grant the request and provide additional time to fully and 

expeditiously comply.

(vii) Manufacturers may require that tools using information covered under 

paragraph (j)(14) of this section comply with the Component Identifier message 

specified in SAE J1939-71 (as specified in paragraph (j)(17) of this section) as

Parameter Group Number (PGN) 65249 (including the message parameter's make, 

model, and serial number) and the SAE J1939-81 (as specified in paragraph (j)(17) 

of this section) Address Claim PGN.

(viii) Manufacturers are not required to make available to equipment and tool 

companies any information related to reconfiguration capabilities or any other 

information that would make permanent changes to existing engine configurations.

(15) Availability of manufacturer-specific scan tools. (i) By July 1, 2013, 

manufacturers shall make available for sale to the persons specified in paragraph 

(j)(3)(i) of this section their own manufacturer-specific diagnostic tools at a fair and 

reasonable cost. These tools shall also be made available in a timely fashion either 

through the manufacturer Web site or through a manufacturer-designated 

intermediary. Upon Administrator approval, manufacturers will not be required to 

make available manufacturer-specific tools with reconfiguration capabilities if they 

can demonstrate to the satisfaction of the Administrator that these tools are not 

essential to the completion of an emissions-related repair, such as recalibration. As a 

condition of purchase, manufacturers may request that the purchaser take all 

necessary training offered by the engine manufacturer. Any required training 

materials and classes must comply with the following:

(A) Similar training must be required by the engine manufacturer for the use of 

the same tool by its franchised dealerships or authorized service networks;

(B) The training must be substantially similar to such training in terms of material 

covered and the length of training;

(C) The training must be made available within six months after a tool request has 

been made;

(D) The training must be made available at a fair and reasonable price.

(ii) Manufacturers shall ship purchased tools in a timely manner after a request and 

training, if any, has been completed. Any required training materials and classes 

must be made available at a fair and reasonable price. Manufacturers who develop 
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different versions of one or more of their diagnostic tools that are used in whole or 

in part for emission-related diagnosis and repair shall also insure that all emissionrelated diagnosis and repair information is available for sale to the aftermarket at a 

fair and reasonable cost. Factors for determining fair and reasonable cost include, 

but are not limited to:

(A) The net cost to the manufacturer's franchised dealerships or authorized service 

network for similar tools obtained from manufacturers, less any discounts, 

rebates, or other incentive programs;

(B) The cost to the manufacturer for preparing and distributing the tools, 

excluding any research and development costs;

(C) The price charged by other manufacturers of similar sizes for similar tools;

(D) The capabilities and functionality of the manufacturer tool;

(E) The means by which the tools are distributed;

(F) Inflation;

(G) The ability of aftermarket technicians and shops to afford the tools.

Manufacturers shall provide technical support to aftermarket service providers for 

the tools described in this section, either themselves or through a third-party of 

their choice.

(16) Changing content of manufacturer-specific scan tools. Manufacturers who opt to 

remove non-emissions related content from their manufacturer-specific scan tools and 

sell them to the persons specified in paragraph (j)(3)(i) of this section shall adjust the 

cost of the tool accordingly lower to reflect the decreased value of the scan tool. All

emissions-related content that remains in the manufacturer-specific tool shall be 

identical to the information that is contained in the complete version of the 

manufacturer-specific tool. Any manufacturer who wishes to implement this option 

must request approval from the Administrator prior to the introduction of the tool into 

commerce.

(17) Reference materials. Manufacturers shall conform with the following industry 

standards. These documents are incorporated by reference in § 86.1. Anyone may 

inspect copies at the U.S. EPA or at the National Archives and Records 

Administration (NARA). For information on the availability of this material at U.S. 

EPA, NARA, or the standard making bodies directly, refer to § 86.1.

(i) SAE J1939-71, Revised January 2008. For providing a means for the application 

processes to access the OSI environment, manufacturers shall comply with this 

industry standard.
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(ii) SAE J1939-73, Revised September 2006. For identification and scaling 

information necessary to interpret and understand data available through Diagnostic 

Message 8, manufacturers shall comply with this industry standard. In the alternate, 

manufacturers may comply with Service/Mode $06 pursuant to SAE J1979, 

Revised May 2007. These recommended practices describe the implementation of 

diagnostic test modes for emissions related test data. Manufacturers shall comply 

with either SAE J1939-73 or SAE J1979 beginning with Model Year 2013.

(iii) SAE J1939-81, Revised May 2003. For management of source addresses and 

the association of those address with an actual function and with the detection and 

reporting of network realized errors, manufacturers shall comply with this industry 

standard.

(iv) SAE J2403, Revised August 2007. For Web-based delivery of service 

information, manufacturers shall comply with this industry standard which 

standardizes various terms, abbreviations, and acronyms associated with on-board 

diagnostics. Manufacturers shall comply with SAE J2403 beginning with the Model 

Year 2013.

(v) TMC RP 1210B, Revised June 2007. For pass-thru reprogramming capabilities, 

manufacturers shall comply with Technology and Maintenance Council's (TMC) 

Recommended Practice TMC RP 1210B. In the alternate, manufacturers may 

comply with SAE J2534-1, Revised December 2004. These recommended practices 

provide technical specifications and information that manufacturers must supply to 

equipment and tool companies to develop aftermarket pass-thru reprogramming 

tools. Manufacturers shall comply with either TMC RP 1210B or SAE J2534-1 

beginning with Model Year 2013.

(18) Reporting requirements. Performance reports that adequately demonstrate that 

each manufacturers website meets the information requirements outlined in 

paragraphs (j)(6)(i) through (j)(6)(vi) of this section shall be submitted to the 

Administrator annually or upon request by the Administrator. These reports shall 

indicate the performance and effectiveness of the websites by using commonly used 

Internet statistics (e.g., successful requests, frequency of use, number of subscriptions 

purchased, etc.). Manufacturers shall provide to the Administrator reports on an 

annual basis within 30 days of the end of the calendar year. These annual reports shall 

be submitted to the Administrator electronically utilizing non-proprietary software in 

the format as agreed to by the Administrator and the manufacturers.

(19) Prohibited acts, liability and remedies.

(i) It is a prohibited act for any person to fail to promptly provide or cause a failure 

to promptly provide information as required by this paragraph (j), or to otherwise 

fail to comply or cause a failure to comply with any provision of this subsection.

(ii) Any person who fails or causes the failure to comply with any provision of this 

paragraph (j) is liable for a violation of that provision. A corporation is presumed 
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liable for any violations of this subpart that are committed by any of its subsidiaries, 

affiliates or parents that are substantially owned by it or substantially under its 

control.

(iii) Any person who violates a provision of this paragraph (j) shall be subject to a 

civil penalty of not more than $ 31,500 per day for each violation. This maximum 

penalty is shown for calendar year 2002. Maximum penalty limits for later years 

may be set higher based on the Consumer Price Index, as specified in 40 CFR part 

19. In addition, such person shall be liable for all other remedies set forth in Title II 

of the Clean Air Act, remedies pertaining to provisions of Title II of the Clean Air 

Act, or other applicable provisions of law.

(iv) Manufacturers will not have any emissions warranty, in-use compliance, defect 

reporting or recall liability for service on a heavy-duty engine that is not undertaken 

by the manufacturer, for any damage caused by their own tools in the hands of 

independent service providers, or for the use and misuse of third party tools.

[74 FR 8408, Feb. 24, 2009, as amended at 75 FR 22978, Apr. 30, 2010]