Heated Oxygen Sensor

Heated Oxygen Sensor (HO2S) monitors amount of oxygen in exhaust gas. HO2S provides a voltage signal which is used to adjust air/fuel mixture to obtain optimum combustion. HO2S heater quickly brings sensor to operating temperature, reducing time engine is in open loop mode.

A rich exhaust gas mixture causes high HO2S voltage (0.6-1.0 volt). A lean exhaust gas mixture causes low HO2S voltage (0.1-0.3 volt). ECM monitors signal from HO2S and adjusts air/fuel mixture accordingly.