Release 05-15      

July 21, 2005


Jerry Martin
Gennet Paauwe
(916) 322-2990
ARB Adopts On-Board Diagnostic Requirement for Big Rigs

-- The California Air Resources Board (ARB) today adopted a regulation that reduces nitrogen oxide emissions from on-road heavy-duty trucks and buses by nearly 110 tons per day by 2020. The regulation requires engine manufacturers to install on-board diagnostic systems (OBD) on heavy duty engines beginning in 2010.

"We expect this rule to lead to lower emissions due to more durable equipment on big rigs and faster repairs on damaged or broken emission control equipment," said Cindy Tuck, ARB Chair. "Easier diagnosis will also cut costs for vehicle owners."

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 those 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 the part is repaired or replaced.

When an emissions control component begins to fail the driver is alerted immediately 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, so repairs can be made before the part fails completely.

The program is similar to one in operation on light and medium duty vehicles since 1996 in California. Today, more than 120 million cars, SUVs and light and medium size trucks nationwide are equipped with OBD. For more information, click here.   

The Air Resources Board is a department of the California Environmental Protection Agency. ARB's mission is to promote and protect public health, welfare, and ecological resources through effective reduction of air pollutants while recognizing and considering effects on the economy. The ARB oversees all air pollution control efforts in California to attain and maintain health based air quality standards.

The energy challenge facing California is real. Every Californian needs to take immediate action to reduce energy consumption. For a list of simple ways you can reduce demand and cut your energy cost, see our website at