Oxygen Sensor: Description and Operation

Exhaust Oxygen Sensor (02):

PURPOSE
The oxygen (O2S) sensor measures the oxygen content of the exhaust. The ECM/PCM monitors the sensor to maintain air/fuel mixture of 14.7 to 1.

OPERATION
The ECM/PCM supplies a voltage of about .45 volt between the sensor and ground. (If measured with a 10 megaohm digital voltmeter may read as low as .32 volt). The O2 sensor varies the voltage within a range of about 1 volt if the exhaust is rich, down to about .10 volt if the exhaust is lean.
The sensor is an like open circuit and produces no voltage below 600°F (315°C). An open sensor circuit or cold sensor causes "Open Loop" operation.

LOCATION:
Exhaust Manifold