Oxygen Sensor: Description and Operation

Oxygen Sensor:

PURPOSE AND LOCATION

The oxygen (O2) sensor, mounted in the exhaust flow, monitors the amount of oxygen in the exhaust gas.

CONSTRUCTION

The sensor has a closed tube made of ceramic zirconia. The inner surface of the tube is is exposed to atmosphere while the outer surface is exposed to the exhaust gas.

OPERATION

The differences in oxygen content between the exhaust gas and the atmosphere make the sensor generate a voltage signal.

^A richer A/F mixture equals higher voltage (Approx. 1 volt).
^A leaner A/F mixture equals a lower voltage (Approx 0.1 volt).

The ECM interprets the voltages and number of voltage "swings" (cross-counts) and will vary injector open times to control the air-fuel ratio.