Circuit Description

PCM supplies a bias voltage (about 450 millivolts) on the HO2S high and low signal circuits. Oxygen sensor voltage ranges from 100 mV when exhaust is lean to 1000 mV when exhaust is rich. PCM monitors and stores HO2S voltage information. PCM then evaluates the voltage samples to determine amount of time HO2S voltage was out of range. PCM will compare the stored HO2S voltage samples taken each sample period and determine if majority of the samples are out of the operating range. If PCM does not detect that voltage went out of the bias range, DTC will set.