EPA is proposing rules requiring the use of onboard diagnostic (OBD) systems to monitor the emissions control systems of large diesel and gasoline highway trucks and buses weighing more than 14,000 pounds.
Onboard diagnostic systems, used in passenger vehicles since the mid-1990s, monitor emissions control components, detect need for emission-related repairs, and alert the vehicle’s operator of these problems. They also help inform service technicians what problem exists so that it can be repaired properly. The OBD systems for highway trucks will work the same way.
The proposed requirements are part of the Clean Diesel Truck and Bus Program, which is designed to result in significant reductions of nitrogen oxides, particulate matter, non-methane hydrocarbons, carbon monoxide, sulfur dioxide, and air toxics from diesel-powered vehicles. These emission reductions will prevent 8,300 premature deaths, more than 9,500 hospitalizations, and 1.5 million lost work days, according to the EPA.
The proposal also makes changes to certain existing OBD requirements for smaller highway diesel trucks.
Specific components of the proposed rule include:
For 2010 and later model year heavy-duty diesel and gasoline engines used in trucks and buses over 14,000 pounds, all major emissions control systems will be monitored and malfunctions be detected prior to emissions exceeding a set of emissions thresholds. Most notably, the aftertreatment devices&mash;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. EPA is 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, one engine family per manufacturer will need to 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% 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, EPA is 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. EPA now believes 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, EPA is 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. EPA believes these OBD thresholds are not technologically feasible in the context of EPA’s very stringent NOx emission standards, and this proposal addresses that issue.
EPA projects 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, and that the proposed new requirements for diesel heavy-duty applications under 14,000 pounds will cost roughly $5 per engine or vehicle.
Additionally, 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).