EPA Finalizes Onboard Diagnostic Systems Requirement for Heavy-Duty Engines Used in Highway Applications

December 24, 2008 // Published as a news service by IHS

In addition to these requirements, the EPA now requires 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.

In September 2008, the EPA granted a waiver from federal preemption to the state of California, allowing it to implement/establish heavy-duty onboard diagnostic (HDOBD) requirements.

The EPA worked with both California and industry stakeholders on this final rule in an effort to develop a consistent set of HDOBD requirements. Issuing and implementing this final rule is a step in the 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.

All of these requirements will help ensure that the benefits of EPA’s 2007 and 2010 heavy-duty highway standards will be realized in use, according to the EPA.

Specifically the rule requires:

• For 2010 and later model year heavy-duty diesel and gasoline engines used in highway applications over 14,000 pounds, the EPA requires that all major emissions control systems be monitored and malfunctions be detected prior to emissions exceeding a set of emissions thresholds.

• The EPA requires that the after-treatment devices, such as 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.

• The EPA requires that all emission-related electronic sensors and actuators be monitored for proper operation.

• For highway applications over 14,000 pounds, the EPA requires 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 will be certified to the OBD requirements. This phase-in is designed to spread out the development effort required of industry and to provide a learning period prior to implementing the OBD requirements on 100% 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, the EPA issued 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. The emission threshold is consistent with the particulate matter (PM) thresholds for over 14,000 pound applications, according to the EPA.

• For 2007 and later model year diesel highway heavy-duty applications under 14,000 pounds, the EPA changed 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 (the 2004 NOx standard) was higher than today’s level (the 2010 NOx standard). The EPA believes these OBD thresholds are not technologically feasible in the context of EPA’s NOx emission standard and this change addresses that issue.

The EPA 2007 heavy-duty highway rule estimated that the new highway standards would result in benefits to the public health and welfare through annual reductions in emissions of NOx, PM, non-methane hydrocarbons (NMHC), carbon monoxide, sulfur dioxide and air toxics.

These emission reductions are touted as preventing 8,300 premature deaths, more than 9,500 hospitalizations and 1.5 million work days lost, claims the EPA.

As a result of the 2007 highway program, each new truck and bus is promoted as being more than 90% cleaner than current models, according to the EPA. The agency projects a 2.6 million ton reduction of NOx emissions in 2030 when the current heavy-duty vehicle fleet is replaced with newer heavy-duty vehicles.

By 2030, the program is designed to reduce annual emissions of NMHC by 115,000 tons and PM by 109,000 tons, according to the EPA.

The EPA did not estimate new emissions reductions associated with the new OBD rule. The EPA said it considers OBD to be a critical element to an overall emissions control program. As such, OBD requirements and their associated benefits were assumed in the EPA’s estimated emissions reductions associated with the 2007 highway rule.

The EPA projects 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.

Experts said 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. The EPA 2009 OBD final rule is available at the EPA’s Office of Transportation and Air Quality web site.

Source: U.S. Environmental Protection Agency (EPA).