Heated Oxygen Sensors (Pre-Catalyst)

The main function of the pre-catalyst Heated Oxygen Sensor (HO2S) is to provide the PCM with exhaust stream information in order to maintain the proper fueling in order to hold the emissions within acceptable levels. These oxygen sensors are always located between the exhaust manifold and the catalytic converter. After the sensor reaches the operating temperature, the sensor generates a voltage that is inversely proportional to the amount of oxygen present in the exhaust gases.

The PCM uses the signal voltage from the fuel control heated oxygen sensors in a closed loop in order to adjust the fuel injector pulse width. While in a closed loop, the PCM can adjust fuel delivery in order to maintain an Air/Fuel ratio which allows the best combination of emission control and driveability.

If the oxygen sensor pigtail wiring, the connector, or the terminal are damaged, replace the entire oxygen sensor assembly. Do not attempt to repair the wiring, the connector, or the terminals. In order for the sensor to function properly, the sensor must have a clean air reference provided. This clean air reference is obtained from the oxygen sensor wires. Any attempt to repair the wires, the connectors, or the terminals could result in the obstruction of the air reference. Any attempt to repair the wires, the connectors, or the terminals will degrade the oxygen sensor performance.