Heated Oxygen Sensor (HO2S)

HO2S sensor monitors amount of oxygen in exhaust gas. Sensor 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 sensor voltage (0.6-1.0 volt). A lean exhaust gas mixture causes low sensor voltage (0.1-0.3 volt). ECM monitors signal from sensor and adjusts air/fuel mixture accordingly.