Oxygen Sensor: Description and Operation

HEATED OXYGEN SENSOR (HO2S) - II

The heated oxygen sensor senses the oxygen concentration in exhaust gas, converts it into a voltage, which is sent to the ECM. The heated oxygen sensor output is about 1 V when the air fuel ratio is richer than the theoretical ratio, and about 0V when the ratio is leaner (higher oxygen concentration in exhaust gas.).

The ECM controls the fuel injection ratio based on this signal so that the air fuel ratio is maintained at the theoretical ratio. The heated oxygen sensor has a heater element which ensures the sensor performance during all driving conditions.