Oxygen (O2) Sensor

O2 sensor produces a small electrical voltage (.1-.9 volt) when exposed to oxygen in exhaust gas flow. O2 sensor is electrically heated for faster switching.

When a large amount of oxygen is present in exhaust gas, O2 sensor will produce a low voltage (.1 volt). With a small amount of oxygen present in exhaust gas, O2 sensor will produce a high voltage (.9 volt).

With O2 sensor monitoring oxygen content in exhaust gas, O2 sensor acts like a rich/lean switch. This information is used by PCM to adjust air/fuel ratio.