Heated Oxygen Sensor

Sensor monitors the amount of oxygen in the exhaust gas. The heater portion of this sensor quickly brings sensor to operating temperature.

On all models, front HO2S provides a voltage signal which is used by ECM to obtain optimum air/fuel mixture. HO2S returns a sweeping return signal which varies between.25 and.75 volt. A rich exhaust gas mixture causes high sensor voltage (0.6-1.0 volt). A lean exhaust gas mixture causes low sensor voltage (0.1-0.3 volt). The ECM monitors signal from sensor and adjusts the injector pulse width accordingly.

Rear HO2S is used to monitor catalyst efficiency. If switching characteristics of front HO2S are shifted, air/fuel ratio is controlled by rear HO2S input. Under normal conditions, rear HO2S is not used for engine control.