Oxygen Sensor: Description and Operation

Oxygen Sensor (Typical):

PURPOSE
The Oxygen Sensor (O2S) is mounted in the exhaust system where it can monitor the oxygen content of the exhaust gas stream. By monitoring the voltage output of the 02S, the Powertrain Control Module (PCM) will determine what fuel mixture command to send to the injectors. All models have two oxygen sensors (right and left).

OPERATION
The PCM provides a 0.45 volt reference signal to the oxygen sensor. When the oxygen sensor is cold (below 200°C), the oxygen sensor signal voltage will be around 0.45 volts and the PCM will keep the system in open loop operation. When the oxygen sesor is warm (above 200°C), the oxygen sensor will swing from rich to lean (above and below 0.45 volts) rapidly, at least one swing every two seconds, if the PCM is in good control of the air fuel mixture.

The oxygen sensor acts as an electro-chemical cell or battery. A voltage is produced in response to the amount of oxygen in the exhaust stream, compared to the oxygen content in the atmosphere. A lean mixture, high O2 content in the exhaust, will produce a low voltage. A rich mixture, low O2 content in the exhaust, will produce a high voltage. Oxygen sensor voltages range from approximately 100 millivolts to 900 millivolts.

DIAGNOSTIC NOTES
The oxygen sensor, if open, should set a code P013 or P017. A shorted sensor circuit to ground should set a code P042 or code P044. Oxygen sensor related problems may also set codes P043, P045, or P046.

Some oxygen sensors (dependant on vehicle options) also incorporate a heating element inside 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 sensor information sooner after engine start-up.

LOCATION
The two oxygen sensors are mounted in the left and right side manifolds.