Oxygen Sensor: Description and Operation

COMPONENT DESCRIPTION







Front Heated Oxygen Sensor
The front HO2S is placed into the exhaust manifold. It detects the amount of oxygen in the exhaust gas compared to the outside air. The sensor has a closed-end tube made of ceramic zirconia. The zirconia generates voltage from approximately 1V in richer conditions to 0V in leaner conditions. The sensor signal is sent to the ECM. The ECM adjusts the injection pulse duration to achieve the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from 1V to 0V.




Rear Heated Oxygen Sensor
The rear heated oxygen sensor (Rear HO2S), after the three way catalyst, monitors the oxygen level in the exhaust gas.
Even if the switching characteristics of the front heated oxygen sensor shift, the air-fuel ratio is controlled to stoichiometric by the signal from the rear heated oxygen sensor.
The sensor has a closed-end tube made of ceramic zirconia.
The zirconia generates voltage from approximately 1V in richer conditions to 0V in leaner conditions.
Under normal conditions, the rear heated oxygen sensor is not used for engine control operation.