Circuit Description

PCM supplies a bias voltage of about 450 mV between the HO2S signal and low circuits. When measured this may display as low as 350 mV. The oxygen sensor signal varies from about 800 mV when exhaust is rich, to about 50 mV when exhaust is lean. If HO2S 1 voltage remains at or about 450 mV bias for an extended period of time, DTC will set. DTC will also set if signal frequency of HO2S Bank 1, Sensor 1 indicates an active sensor (closed loop), but amplitude (voltage) of signal remains within a calibrated range.