Regulatory Announcement

EPA Finalizes 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 Applications 

Under 14,000 Pounds 

The U.S. Environmental Protection Agency (EPA) is promulgating regulations that will require the emission control systems of large 

highway diesel and gasoline trucks to be monitored for malfunctions 

via an onboard diagnostic system (OBD) similar to those systems that 

have been required on passenger cars since the mid-1990s. In addition to these requirements, EPA is requiring manufacturers to make 

available to the service and repair industry information necessary to 

perform repair and maintenance service on OBD systems and other 

emission-related engine components. This rule also makes changes to 

certain existing OBD requirements for smaller highway heavy-duty 

diesel trucks. 

Background 

•	 On January 18, 2001, EPA established a comprehensive national control 

program—the Clean Diesel Trucks and Buses program—to regulate the 

heavy-duty vehicle and its fuel as a single system. (66 FR 5002) As part of this 

Office of Transportation and Air Quality 

EPA-420-F-08-032 

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Regulatory Announcement

program, new emission standards for heavy-duty highway engines and vehicles began to 

take effect in model year 2007 and are being phased in through 2010. These standards 

are based on the use of high-efficiency catalytic exhaust emission control devices or comparably effective advanced technologies. Because these devices are damaged by sulfur, the 

program also reduces the level of sulfur in highway diesel fuel by 97 percent. The emissions reductions associated with this program are estimated to result in over $70 billion 

in benefits through reduced hospitalizations and lost work days. The OBD requirements 

will help to ensure that these benefits are realized. 

•	 In October of 2000, EPA published a final rule requiring OBD systems on heavy-duty 

vehicles and engines up to 14,000 pounds gross vehicle weight rating (GVWR) 

(65 FR 59896). In that rule, EPA expressed its intention to develop in a future rule 

OBD requirements for vehicles and engines used in vehicles over 14,000 pounds. EPA 

again expressed this same intention in its Clean Diesel Trucks and Busses final rule 

(66 FR 5002) which established new heavy-duty highway emissions standards for 2007 

and later model year engines (i.e., the “2007 Highway Rule”). 

•	 On February 19, 1993, EPA published a final rule requiring manufacturers of light-duty 

applications to install OBD systems on their vehicles beginning with the 1994 model 

year (58 FR 9468). The OBD systems must monitor emission control components for 

any malfunction or deterioration that could cause exceedance of certain emission thresholds. 

The regulation also required that the driver be notified of any need for repair via a dashboard light, or malfunction indicator light (MIL), when the diagnostic system detected a 

problem. 

•	 On August 9, 1995, EPA published a final rule that established service information 

regulations for light-duty vehicles and light-duty trucks (60 FR 40474). These regulations, in part, required each Original Equipment Manufacturer (OEM) to list all of its 

emission-related service and repair information on a Web site and note how to obtain 

that information and at what cost. The intent being to ensure that aftermarket service 

and repair facilities have access to the same emission-related service information, in the 

same or similar manner, as that provided by OEMs to their franchised dealerships. These 

service information availability requirements have been revised since that first final rule 

in response to changing technology among other reasons. (68 FR 38428) 

•	 In June of 2003, EPA published a final rule extending service information availability 

requirements to heavy-duty vehicles and engines weighing up to 14,000 pounds GVWR. 

EPA did not extend these requirements to engines above 14,000 pounds GVWR, deciding 

to wait until such engines were subject to OBD requirements. 

Overview of the OBD Final Rule 

In September 2008, EPA granted a waiver from federal preemption to the State of California, 

allowing it to implement/establish heavy-duty onboard diagnostic (HDOBD) requirements. 

Given the nature of the heavy-duty trucking industry in the United States and the importance 

of the free and open movement of goods across state borders, EPA believes that a consistent 

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Regulatory Announcement

nationwide HDOBD program is a desirable outcome. EPA has worked closely with California 

on the proposed rule and with both California and industry stakeholders on this final rule, in 

an effort to develop a consistent set of HDOBD requirements. As a result, EPA’s new HDOBD 

program is consistent with the California program in almost all important aspects. EPA believes 

that, while minor differences exist between these requirements and the California requirements, 

we will end up with OBD systems that will be compliant with both the federal program and the 

California program. Issuing and implementing this final rule is an important step in EPA’s efforts 

to work with the California Air Resources Board to develop a consistent national program. 

The rule requires manufacturers to install OBD systems that monitor the functioning of emission control components and alert the vehicle operator to any detected need for emission-related repair. In addition, when a malfunction occurs, diagnostic information must be stored in the 

engine’s computer to assist in diagnosis and repair of the malfunction. Also, manufacturers are 

required to make available to the service and repair industry information necessary to perform 

repair and maintenance service on OBD systems and other emission related engine components. 

All of these requirements will help to ensure that the significant benefits of EPA’s 2007 and 2010 

heavy-duty highway standards will be realized in-use. Specifically: 

•	 For 2010 and later model year heavy-duty diesel and gasoline engines used in highway applications over 14,000 pounds, we are requiring that all major emissions control 

systems be monitored and malfunctions be detected prior to emissions exceeding a set of 

emissions thresholds. Most notably, we are requiring that the aftertreatment devices— 

e.g., the diesel particulate filters and oxides of nitrogen (NOx) reducing catalysts—that 

will be used on highway diesel engines to comply with the 2010 emissions standards will 

be monitored and their failure will be detected and noted to the driver. We are also requiring that all emission-related electronic sensors and actuators be monitored for proper 

operation. 

•	 For these highway applications over 14,000 pounds, we are requiring that one engine 

family per manufacturer be certified to the OBD requirements in the 2010 through 2012 

model years. Beginning in 2013, all highway engines for all manufacturers would have to 

be certified to the OBD requirements. This phase-in is designed to spread over a number of years the development effort required of industry and to provide industry with a 

learning period prior to implementing the complex OBD requirements on 100 percent of 

their highway product line. 

•	 For applications over 14,000 pounds, the service information availability requirements 

would apply for those engines certified to the OBD requirements. 

•	 For 2010 and later model year highway heavy-duty diesel applications under 14,000 

pounds, we are promulgating a new emissions threshold for monitoring of the diesel particulate filter. The existing requirement for these applications is to detect a catastrophic 

failure of the device. We believe that a more stringent requirement is appropriate and 

feasible. The emission threshold is consistent, both in stringency and in timing, with 

the particulate matter (PM) thresholds for over 14,000 pound applications. 

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Regulatory Announcement

•	 For 2007 and later model year diesel highway heavy-duty applications under 14,000 

pounds, we are changing the emission thresholds for NOx emissions. The existing 

thresholds, typically 1.5 times the applicable NOx standard, were established when the 

engine’s NOx standard (i.e., the 2004 NOx standard) was much higher than today’s very 

low level (i.e., the 2010 NOx standard). We believe these OBD thresholds are not technologically feasible in the context of EPA’s very stringent NOx emission standard, and 

this change addresses that issue. 

Health and Environmental Effects 

In our 2007 heavy-duty highway rule, we estimated that the new 2007 highway standards will 

result in substantial benefits to the public health and welfare through significant annual reductions in emissions of NOx, PM, nonmethane hydrocarbons (NMHC), carbon monoxide, sulfur 

dioxide, and air toxics. These emission reductions will prevent 8,300 premature deaths, more 

than 9,500 hospitalizations, and 1.5 million work days lost. The OBD requirements will help to 

ensure that these projected benefits will be realized. 

As a result of the 2007 highway program, each new truck and bus will be more than 90 percent 

cleaner than current models. We project a 2.6 million ton reduction of NOx emissions in 2030 

when the current heavy-duty vehicle fleet is completely replaced with newer heavy-duty vehicles that comply with the 2007 program’s emission standards. By 2030, the program will reduce 

annual emissions of NMHC by 115,000 tons and PM by 109,000 tons. 

Ozone causes a range of health problems related to breathing, including chest pain, coughing, and 

shortness of breath. PM is deposited deep in the lungs and causes premature death, increased 

emergency room visits, and increased respiratory symptoms and disease. With both ozone and 

PM, children and the elderly are most at risk. In addition, ozone, NOx, and PM adversely 

affect the environment in various ways, including crop damage, acid rain, and visibility impairment. 

We have not estimated new emissions reductions associated with this OBD rule. We consider 

OBD to be a critical element to an overall emissions control program. As such, OBD requirements and their associated benefits were assumed in our estimated emissions reductions associated with the 2007 highway rule. 

Cost Effects 

We project that the OBD requirements will result in an increased hardware cost of roughly $60 

per diesel engine and $70 per gasoline engine used in applications over 14,000 pounds. We 

project that the new requirements for diesel heavy-duty applications under 14,000 pounds will 

have no increased hardware cost since these engines and vehicles have complied with OBD 

requirements since 2004. 

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Public Participation Opportunities 

You can access the rule and related documents on EPA’s Office of Transportation and Air Quality (OTAQ) Web site at: www.epa.gov/obd. 

For More Information 

For additional information specific to OBD, please contact: 

Todd Sherwood 

U.S. Environmental Protection Agency


Office of Transportation and Air Quality


Assessment and Standards Division


2000 Traverwood Drive


Ann Arbor, MI 48105


734-214-4405


E-mail sherwood.todd@epa.gov.


For additional information specific to service information availability, please contact:| 

Holly Pugliese 

U.S. Environmental Protection Agency


Office of Transportation and Air Quality


Compliance and Innovative Strategies Division


Ann Arbor, MI 48105


734-214-4288


E-mail pugliese.holly@epa.gov.


Regulatory Announcement