ArcticTiger

The purpose of a O2 sensor is to detect the oxygen content in the exhaust gases coming out of your engine, it tells the PCM whether it is running rich or lean and the PCM will adjust accordingly. Usually if the O2 sensor is faulty the PCM will default to a rich mixture, but depending on how it faults, the O2 sensor may just provide a constant output to the PCM (not completely sure about the constant output idea)... Hope that helps...