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 ECM will determine what fuel mixture command to send to the injectors.