Oxygen Sensor (O2S)

Oxygen sensor detects oxygen content of exhaust gases and sends signal to PCM, which varies air/fuel ratio to maintain a 14.7:1 ratio under most conditions. This ratio is most efficient for combustion and 3-Way Catalytic Converter (TWC) operation. O2S has an internal heater to stabilize sensor output. Each vehicle has at least 2 Heated Oxygen Sensors (HO2S). There is a primary HO2S mounted in front of TWC and a secondary HO2S behind TWC.