Oxygen Sensor: Description and Operation

Air Fuel Ratio (A/F) Sensor
The A/F Sensor operates over a wide air/fuel range. The A/F Sensor is installed upstream of the TWC, and sends signals to the ECM which varies the duration of fuel injection accordingly.




Secondary Heated Oxygen Sensor (Secondary HO2S)
The secondary HO2S detects the oxygen content in the exhaust gas downstream of the three way catalytic converter (TWC) and sends signals to the ECM which checks the efficiency of the TWC. To stabilize its output, the sensor has an internal heater. The secondary HO2S is installed in the TWC.