Oxygen Sensor (O2S)

O2S produces a small electrical voltage(.1-.9 volt) when exposed to oxygen in exhaust gas flow. O2S is electrically heated for faster switching.

When a large amount of oxygen is present in exhaust gas, O2S will produce a low voltage (.1 volt). With a small amount of oxygen present in exhaust gas, O2S sensor will produce a high voltage (.9 volt). O2S informs PCM of oxygen content in exhaust gas. PCM uses this information to adjust air/fuel ratio.