emission control system?

Sounds like you need a new Oxygen (O2) sensor. Most modern vehicles have at least 2 of them. They are located before (primary) and bebind (secondary) the catalytic converter. The primary oxygen sensor tends to fail first because it is nearest to the engine exhaust. However any abnormal function of any of these sensors will trip the "Check Engine Light". You probably can take the O2 sensors out and try clean them with brake cleanner and if that doesnt turn off the light then you probably need to buy new O2 sensors. Driving with bad O2 sensors will hurt the catalytic converter. Your fuel economy will drop to 3-5 mpg, your car become more slugglish, and likely you wont pass emission test.

Just2Hot4U2
June 2005