Oxygen Sensor: Description and Operation

Oxygen Sensor (Typical):

The oxygen sensor is mounted in the exhaust system where it can monitor the oxygen content of the exhaust gas stream. 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. By monitoring the voltage output of the 02 sensor, the PCM/ECM will determine what fuel mixture command to send to the injectors.
All models except the fullsize front wheel drive model have two oxygen sensors (right and left).