Oxygen Sensor: Description and Operation

HEATED OXYGEN SENSOR (HO2S)




HO2S sensor senses the oxygen concentration in exhaust gas and converts it into a voltage which is sent to the ECU. For Zirconium type sensors, the HO2S outputs about 1 V when the air fuel ratio is richer than the theoretical ratio, and outputs about 0 V when the ratio is leaner (higher oxygen concentration in exhaust gas.). The ECU controls the fuel injection ratio based on this signal so that the air fuel ratio is maintained at the stoichiometric ratio. HO2S has a heating element which ensures sensor performance during all driving conditions.