US EPA proposes OBD requirements for large trucks and buses

14 December 2006

The US Environmental Protection Agency (EPA) has issued a Notice of Proposed Rulemaking to implement onboard diagnostic systems (OBD) on 2010 and later heavy-duty engines used in highway vehicles over 14,000 pounds. It will be the first OBD regulation for large trucks and buses.

The new OBD proposal would require the emissions control systems of large highway diesel and gasoline trucks to be monitored for malfunctions via an OBD system, similar to those systems that have been required on passenger cars since the mid-1990s. The proposal also introduces revisions to the exsting OBD requirements for highway heavy-duty vehicles under 14,000 pounds. In addition, the EPA is 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).

Specifically, the proposal calls for the following OBD measures:

• For 2010 and later heavy-duty diesel and gasoline engines used in trucks and buses over 14,000 pounds:
  • All major emission control systems must be monitored and malfunctions be detected prior to emissions exceeding a set of emissions thresholds. The aftertreatment devices—e.g., the diesel particulate filters and NOx reducing catalysts—that will be used on highway diesel engines to comply with the 2010 emissions standards must be monitored and their failure should be detected and noted to the driver. All emission-related electronic sensors and actuators must be monitored for proper operation.
  • 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.
• For 2010 and later model year highway heavy-duty diesel vehicles under 14,000 pounds, a new emissions threshold for monitoring of the diesel particulate filter is proposed. The existing requirement for these applications is to detect a catastrophic failure of the device. A more stringent requirement has been proposed, consistent in stringency and in timing with the proposed PM thresholds for over 14,000 pound applications.
• For 2007 and later model year highway heavy-duty diesel vehicles under 14,000 pounds, a change to the existing emissions thresholds for NOx emissions are proposed. 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. The EPA concluded that these OBD thresholds are not technologically feasible in the context of EPA’s very stringent NOx emission standards, and the proposal addresses that issue.

Source: US EPA