Description and Operation: Description
The Heated Oxygen Sensor (HO2S) consists of zirconium and alumina, and is installed both upstream and downstream of the Manifold Catalytic Converter. It varies in accordance with the air/fuel ratio.
The sensor must be hot in order to operate normally. To keep it hot, the sensor has a heater which is controlled by the ECM via a duty cycle signal. When the exhaust gas temperature is lower than the specified value, the heater warms the sensor tip.