Oxygen (O2) Sensor

The O2 sensor is screwed into the top of the exhaust manifold, just ahead of the tail pipe connection, so that it is exposed to exhaust gas flow. Its function is to monitor the oxygen content of the exhaust, and to supply the logic module with a voltage signal which is directly proportional to this content.

If the oxygen content of the exhaust is high (lean air/fuel mixture), the voltage signal from the sensor to the logic module is low. As oxygen content decreases (mixture becomes richer), the signal voltage increases. In this manner, the logic module is kept constantly informed of air/fuel ratio. It can then alter fuel injector "on" time, in response to these signals, to obtain the best air/fuel ratio under any given condition.