Oxygen Sensor: Description and Operation

Location

Sensor threaded into exhaust manifold.

SENSOR PURPOSE

The Control Module uses the oxygen sensor input (during Closed Loop operation), to determine whether the current air/fuel mixture is too rich or too lean.

PCM then fine tunes the air/fuel mixture by adjusting injector pulse width.

SENSOR OPERATION

Sensor generates a voltage between 0 and 1.0 volts dependant on the difference between the oxygen content of the exhaust gas and the oxygen content of the air outside the exhaust system (approximately 21 %).

^ When a large amount of oxygen is present in the exhaust (caused by a lean air/fuel mixture), the sensor generates a voltage lower than 0.45 volts.

^ When there is a lesser amount of oxygen present in the exhaust (rich air/fuel mixture), the sensor generates voltage higher than 0.45 volts.

By converting the oxygen content of the exhaust into a voltage, the sensor is a lean/rich indicator for the PCM.

SENSOR HEATER PURPOSE

Vehicle enters CLOSED LOOP faster, (because sensor reaches operating temperature sooner).

Allows CLOSED LOOP operation during extended idle, (because heater maintains correct operating temperature).