Oxygen Sensor: Description and Operation

Oxygen Sensor:

PURPOSE AND LOCATION
The oxygen (O2) sensor, mounted in the exhaust manifold, 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.