Regulatory Announcement

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 HeavyDuty Applications Under 14,000 Pounds

EPA420-F-06-058

December 2006

Office of Transportation and Air Quality

The U.S. Environmental Protection Agency (EPA) is proposing regulations that would require the emissions 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. We are seeking comment on possible future regulations 

that would require OBD systems on heavy-duty diesel engines used 

in nonroad equipment (e.g., construction, industrial, agricultural). 

This proposal 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 Truck and Bus Program—to 

regulate heavy-duty vehicles and diesel fuel as a single system (66 

FR 5002). As part of this program, new emission standards for heavyduty engines and vehicles take effect in model years 2007 through 

2010 and will apply to heavy-duty highway engines and vehicles. 

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 
Regulatory Announcement

Proposed OBD Requirements for Heavy-Duty Engines 

percent. The emissions reductions associated with this program are estimated 

to result in over $70 billion in public health and welfare benefits through reduced 

hospitalizations and lost work days. The proposed OBD requirements will help to 

ensure that these benefits are realized. 

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

passenger vehicles to install OBD systems on 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 driver notification of any 

need for repair via a dashboard light, or malfunction indicator light (MIL), when 

the diagnostic system detected a problem. This is commonly referred to as the 

“Check Engine” light. 

• On August 9, 1995, EPA published a rulemaking that set forth automotive 

service information requirements for light-duty vehicles and light-duty trucks 

(60 FR 40474). These regulations, in part, required each Original Equipment 

Manufacturer (OEM) to list all emission-related service and repair information 

on a Web site and explain how to obtain that information and at what cost. The 

intent of this provision is 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 the 1995 

rule in response to changing technology (68 FR 38428). 

• In October 2000, EPA published a 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 Truck and 

Bus rule (66 FR 5002) which established new heavy-duty highway emissions 

standards for 2007 and later model year engines.

• In June 2003, EPA published a 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 Proposal

The proposal requires manufacturers to install OBD systems that monitor the function 

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 proposed are requirements that would make available to the service 
Regulatory Announcement

Proposed OBD Requirements for Heavy-Duty Engines 

and repair industry information necessary to perform repair and maintenance service 

on OBD systems and other emission related engine components. These proposed 

requirements will help to ensure that the significant benefits of EPA’s Clean Diesel 

Program exhaust emission standards will be realized in-use. Specifically:

• For 2010 and later model year heavy-duty diesel and gasoline engines used in 

trucks and buses over 14,000 pounds, we are proposing 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 proposing that all emission-related 

electronic sensors and actuators be monitored for proper operation.

• For 2010 and later highway vehicles over 14,000 pounds, we are proposing 

that one engine family per manufacturer be certified to the proposed 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 proposed 

OBD requirements. This phase-in is designed to spread over a number of years 

the development effort required by industry and to provide industry with a 

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

their highway product line.

• For vehicles 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 vehicles under 14,000 

pounds, we are proposing 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 now that a more stringent 

requirement is appropriate and feasible. The proposed emissions threshold is 

consistent, both in stringency and in timing, with the proposed particulate matter 

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

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

pounds, we are proposing a change to the existing emissions thresholds for 

NOx emissions. The existing thresholds, typically 1.5 times the applicable 

NOx standard, were established when the engine’s NOx standard was much 

higher than today’s very low level. We believe these OBD thresholds are not 

technologically feasible in the context of EPA’s very stringent NOx emission 

standards, and this proposal addresses that issue.

For heavy-duty diesel engines used in nonroad equipment, we are seeking comment 

on possible future regulations that would require OBD systems. Diesel engines used 
Regulatory Announcement

Proposed OBD Requirements for Heavy-Duty Engines 

in nonroad equipment are, like highway engines, a major source of NOx and PM 

emissions, and the diesel engines used in nonroad equipment are essentially the same 

as those used in heavy-duty highway trucks. Further, new regulations applicable to 

nonroad diesel engines will result in the introduction of advanced emissions control 

systems like those expected for highway diesel engines. (69 FR 38958) Therefore, 

having OBD systems and OBD regulations for nonroad engines seems to be a natural 

progression from the proposed requirements for heavy-duty highway engines. 

Health and Environmental Effects • In our 2007 Clean Diesel Truck and Bus rule, we estimated that the new 2007 

emission 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. This OBD proposal will 

help to ensure that these projected benefits will be realized.

• As a result of this 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 proposal. 

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 Clean 

Diesel Truck and Bus Program. 

Cost Effects

We project that the proposed OBD requirements will result in an increased cost of 

roughly $50 per diesel engine and $60 per gasoline engine used in applications over 

14,000 pounds. We project that the proposed new requirements for diesel heavy-duty 

applications under 14,000 pounds will cost roughly $5 per engine or vehicle.
Regulatory Announcement

Proposed OBD Requirements for Heavy-Duty Engines 

Public Participation Opportunities

We welcome your comments on this proposed rule. Comments will be accepted for 60 

days beginning when this proposal is published in the Federal Register. All comments 

should be identified by Docket ID No. EPA-HQ-OAR-2005-0047 and submitted by one of 

the following methods:

• Internet: www.regulations.gov

• E-mail: A-and-R-Docket@epa.gov

• Mail:

Environmental Protection Agency

EPA Docket Center (EPA/DC)

Air and Radiation Docket and Information Center

1700 Pennsylvania Avenue NW

Washington, DC 20460

• Hand delivery:

EPA Docket Center

EPA West Building

Room 3340

1301 Constitution Avenue NW

Washington, DC

For More Information

You can access the proposed rule and related documents on EPA’s Office of 

Transportation and Air Quality (OTAQ) Web site at:

www.epa.gov/obd/regtech/heavy.htm

For additional information specific to OBD, please contact:

• Todd Sherwood

U.S. Environmental Protection Agency

National Vehicle and Fuels Emission Laboratory

Assessment and Standards Division

2000 Traverwood, Ann Arbor, MI 48105

phone: 734-214-4405

fax: 734-214-4816

E-mail: sherwood.todd@epa.gov
Regulatory Announcement

Proposed OBD Requirements for Heavy-Duty Engines 

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

• Holly Pugliese

U.S. Environmental Protection Agency

National Vehicle and Fuels Emission Laboratory

Compliance and Innovative Strategies Division

2000 Traverwood, Ann Arbor, MI 48105

phone: 734-214-4288

fax: 734-214-4869

E-mail: pugliese.holly@epa.gov