General Information: General Description

The PCM uses heated oxygen sensors (HO2S) placed before and after the catalytic converter to monitor the oxygen content of the exhaust. The front HO2S signal is used by the PCM to calculate air/fuel ratios when in closed loop operation. The signal, of the HO2S placed after the catalytic converter, is used to monitor the operation of the front HO2S and the catalytic converter. The HO2S generates a voltage signal which indicates the difference of oxygen content of the exhaust and the ambient air. The HO2S will generate a higher voltage signal (rich), when the exhaust has a lower content of oxygen than ambient air.