Check Yourself

EPA mandates onboard diagnostics systems for heavy-duty trucks.

On Feb. 24, 2009, the U.S. Environmental Protection Agency (EPA) published a final rule that requires emission control systems on large highway diesel and gasoline trucks with engines manufactured during or after 2010 to be monitored for malfunctions through an onboard diagnostic (OBD) system (74 FR 8310). These OBD systems are similar to those that have been required on passenger cars since the mid-1990s.

The rule requires manufacturers to install OBD systems that monitor the emission control components and alert the vehicle operator to any malfunctions and needs for repair. This requirement must be met with a dashboard malfunction light and a diagnostic trouble code. In addition, when a malfunction occurs, diagnostic information must be stored in the engine's computer to assist in diagnosis of the malfunction. The rule also requires manufacturers to make available to the service and repair industry the information necessary to repair the OBD systems and other emission related engine components.

For new diesel engines used in highway vehicles that weigh more than 14,000 pounds, the type commonly used by the waste industry, the OBD systems must include:

  • Fuel system monitoring, including pressure control, injection quantity and injection timing.

  • Engine misfire monitoring, including the ability to identify which cylinders are misfiring.

  • Exhaust gas recirculation (EGR) system monitoring, including EGR low and high flow rates, EGR slow response, and EGR cooler performance.

  • Turbo boost control system monitoring, including turbo under- and over-boost, variable geometry turbochargers (VGT) slow response, and charge air under-cooling.

  • Non-methane hydrocarbon (NMOC) conversion monitoring, including conversion efficiency and after-treatment assistance functions.

  • Selective catalytic reduction (SCR) and lean NOx catalyst monitoring, including conversion efficiency, active/intrusive reductant delivery performance, quantity and quality.

  • NOx adsorber system monitoring, including capability and active/intrusive reductant delivery performance.

  • Diesel particulate filter (DPF) system monitoring, including filter performance, regeneration frequency, incomplete regeneration, missing substrate and active/intrusive injection.

  • Exhaust gas sensor and sensor heater monitoring, including sensors located upstream and downstream of after-treatment devices for performance and circuit integrity.

The requirements for new gasoline engines in vehicles weighing more than 14,000 pounds are similar but tailored to the unique qualities of those engines. Gas engines must monitor fuel systems, engine misfire, exhaust gas recirculation, cold-start emission reduction strategy systems, secondary air systems, catalyst system, evaporative system, exhaust gas sensors, variable value timing system, engine cooling system and crankcase ventilation system.

EPA did not estimate the emission reductions associated with the new OBD rule. Nevertheless, the agency considers the rule to be a critical element of the overall emission control program established under the 2007 heavy-duty highway rule. As a result of these rules, each new truck and bus will be 90 percent cleaner than the current models. EPA projects that there will be a 2.6 million-ton reduction of NOx emissions, and annual emissions of NMHC and particulate matter (PM) will be reduced by 115,000 tons and 109,000 tons respectively.

Edward Repa is the director of environmental programs at NSWMA. He can be reached at 202-364-3773 or [email protected]