5 December 2008

The US Environmental Protection Agency (EPA) has signed a final rule to require on-board diagnostic (OBD) systems on heavy-duty highway engines used in vehicles weighing over 14,000 lbs.

The rule requires manufacturers to install OBD systems that monitor the functioning of emission control components and alert the vehicle operator in case emission-related repair is needed. When a malfunction occurs, diagnostic information must be also stored in the engine’s computer to assist in diagnosis and repair of the malfunction. In addition, 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.

In 2010 and later model year heavy-duty diesel and gasoline engines used in highway vehicles over 14,000 lbs, all major emission control systems must be monitored, including aftertreatment devices—e.g., diesel particulate filters and NOx reducing catalysts—as well as all emission-related electronic sensors and actuators. Malfunctions must be detected prior to emissions exceeding a set of OBD emission thresholds.

The phase-in schedule requires that one engine family per manufacturer must 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.

The regulation also includes certain changes to the existing OBD requirements for vehicles below 14,000 lbs. Specifically:

  • For 2010 and later model year highway heavy-duty diesel applications under 14,000 lbs, the EPA adopted a new emission threshold for monitoring of the diesel particulate filter. The existing requirement for these applications—to detect a catastrophic failure of the device—is replaced with a PM emission threshold, which is consistent in stringency and in timing with the PM thresholds for applications over 14,000 lbs.
  • For 2007 and later model year diesel highway heavy-duty applications under 14,000 lbs, the EPA is changing the OBD emission 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 the 2010 NOx standard. These OBD thresholds would not be technologically feasible in the context of EPA’s 2010 NOx emission standard.

The new EPA rule follows the heavy-duty OBD (HDOBD) regulations that have been adopted by California Air Resources Board (ARB), with a phase-in schedule from 2010 to 2016. The EPA has worked closely with California on the final rule, in an effort to develop a consistent set of national HDOBD requirements. The new HDOBD program is consistent with the California program in “almost all important aspects”, said the EPA.

The EPA projected 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.

Source: US EPA