Oxygen Sensor

The amount of oxygen in exhaust gases varies according to the air/fuel ratio of the intake charge. The exhaust gas oxygen sensor, located in the exhaust pipe, detects this content and transmits a low-voltage signal to the ECU.

The outer surface of the sensor is exposed to exhaust gases, the inner surface to outside air. The difference in the amount of oxygen contacting the inner and outer surfaces of the sensor creates a pressure, which results in a small voltage signal. This signal, which is a measure of the unburned oxygen in the exhaust gas, is transmitted to the ECU.

If the amount of oxygen in the exhaust system is low (rich mixture), the sensor voltage signal will be high. If the mixture is lean, the oxygen sensor will generate a low voltage signal.