Oxygen Sensor: Description and Operation

Heated Oxygen Sensor:

PURPOSE
The oxygen (O2) sensors, mounted in each exhaust manifold, monitor the amount of oxygen in the exhaust gas.

Heated O2 Sensor Operation:

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.

CONSTRUCTION
The sensor has a closed tube made of ceramic zirconia. To improve the generating power of the Zirconia, its tube is coated with platinum. The inner surface of the tube is is exposed to atmosphere while the outer surface is exposed to the exhaust gas. Also, each sensor is equipped with an internal electric heater.