Heated Oxygen Sensors

The main function of the pre-catalyst HO2S is to provide the PCM with exhaust stream information in order to maintain proper fueling to hold emissions within acceptable levels. These oxygen sensors are always located between the exhaust manifold and the 3-way Catalytic Converter (TWC). After the sensor reaches the operating temperature, the sensor generates a voltage inversely proportional to the amount of oxygen present in the exhaust gases.

The PCM uses the signal voltage from the fuel control HO2S 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 to fuel ratio which allows the best combination of emission control and driveability.

If the HO2S pigtail wiring, connector, or terminal are damaged, replace the entire HO2S assembly. Do not attempt to repair the wiring, the connector, or the terminals. In order for the sensor to function properly, the sensor must be provided with a clean air reference. This clean air reference is obtained by way of the HO2S wires. Any attempt to repair the wires, connectors, or terminals could result in the obstruction of the air reference. Any attempt to repair the wires, connectors, or terminals could degrade HO2S performance.