Kia Niro: Engine Control System / Heated Oxygen Sensor (HO2S) Description and operation

Heated Oxygen Sensor (HO2S), consisting of zirconium and alumina, is installed on both upstream and downstream of the Manifold Catalytic Converter (MCC) to detect the air/fuel ratio and send it to the ECM. The sensor output voltage 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.