22 July 2005

The California Air Resources Board (ARB) adopted a regulation that requires engine manufacturers to install on-board diagnostic systems (OBD) on heavy duty truck and bus engines beginning in 2010. By 2020, the rule would reduce NOx emissions from heavy-duty on-road engines by nearly 110 tons per day due to more durable emission control equipment, said the ARB.

The new rule—set for introduction in 2010, with full compliance by 2016—will monitor 120 different engine locations that can leak emissions when they age or break down. The new OBD regulation requires heavy-duty diesel and gasoline powered truck and bus manufacturers to equip the vehicles with a system of sensors that can monitor the performance of engine parts that may affect emissions. The monitors are designed to alert vehicle operators that part of the pollution control system is failing and emissions are likely to increase unless repairs are made.

The OBD regulation requires manufacturers to monitor such components as the fuel system, catalyst system, exhaust gas recirculation (EGR) system, particulate filter, and cooling system. The regulation requires the calibration of most major emission control system and component monitors to emission levels correlated to the emission standards (i.e., require a fault to be detected before emissions exceed the standards by a certain amount).

When a fault in an emission control component is detected, the driver must be alerted by a dashboard indicator light. An access port under the dash allows a mechanic with a handheld computer to obtain detailed information about the vehicle’s performance and directs him to the failing equipment.

The ARB adopted first OBD regulations in 1989, requiring passenger cars, light-duty trucks, and medium-duty vehicles to be equipped with OBD systems (known as OBD II) starting with model year 1996. First OBD requirements for heavy-duty vehicles (GVWR > 14,000 lb) were adopted in 2004. The 2004 rule, known as the Engine Manufacturer Diagnostic system (EMD) regulation, requires heavy-duty engine manufacturers to implement diagnostic systems on all 2007 and later model year on-road heavy-duty diesel and gasoline engines. However, the EMD regulation—which requires the monitoring of a few major emission control technologies and contains no standardized requirements—is much less comprehensive than the OBD II regulation. The ARB had indicated during the EMD rulemaking that more comprehensive diagnostic, testing, and standardization requirements for future heavy-duty engines would be adopted in 2005.

Source: California ARB (press release | Initial Statement of Reasons)