Oxygen Sensor: Description and Operation

DESCRIPTION
Two Heated Oxygen Sensors (HO2S) sensors are mounted in the exhaust system where they monitor the oxygen content in the exhaust stream. There is a sensor mounted in each exhaust manifold.

OPERATION
A HO2S sensor acts like a battery because it creates its own signal voltage once it reaches operating temperature. This voltage is produced when the oxygen content in the exhaust stream is different than the oxygen content in the atmosphere. A lean condition (high oxygen content in exhaust) will produce a low voltage (near 0 volt) and a rich condition (low oxygen content in exhaust) will produce a high voltage (near one volt). The PCM provides a reference signal voltage (0.45 volt) and a ground to the sensor. The PCM reference voltage is necessary because the HO2S sensors do not provide there own voltage until they reach operating temperature.

The Premium V HO2S sensors also incorporate a heating element inside of the sensor housing. This heating element is energized with the ignition "ON" and allows the sensors to reach operating temperatures quickly. The PCM can then use HO2S sensor information sooner after engine start-up.

The PCM uses oxygen sensor information during "Closed Loop" operation to constantly adjust fuel control to reduce exhaust emissions. Because the Premium V HO2S sensors provide information sooner after engine start-up, exhaust emissions are reduced. Faulty HO2S sensors will cause various driveability conditions and should set a PCM DTC.