California to make emissions diagnostics mandatory

user-gravatar Headshot

A new California Air Resources Board regulation will start requiring heavy truck and bus onboard diagnostic systems in 2010, which is expected to increase engine prices $132.

The board estimates the requirement will reduce daily nitrogen oxide emissions by 110 tons by 2020.

“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 board Chairwoman Cindy Tuck. “Easier diagnosis will also cut costs for vehicle owners.”

Full compliance with the new rule is set for 2016.

This regulation requires heavy-diesel and gasoline-powered truck and bus manufacturers to equip vehicles with sensors monitoring engine parts that affect emissions. The monitors alert drivers of emission problems via a dashboard indicator light. An access port under the dash allows mechanics to use a scan tool to obtain information necessary to make the repair before the part fails completely.

This new rule is similar to one passed in 1996 affecting California’s light- and medium-duty vehicles.

CARB is a department of the California Environmental Protection Agency. More information is available by calling the board at 800-242-4450 or visiting