Oxygen Sensor: Description and Operation

Heated 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. Also inside the sensor is an electrical heater.

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.

To help the sensor to reach operating temperature quickly, a heating element is incorporated inside the housing. The heater enables the 02 sensor to reach operating temperature in a matter of seconds, as opposed to minutes with non-heated sensors. The advantages of a heated sensor are better driveability and lower emissions during warm-up.