Oxygen (O2) Sensor

O2 sensor is threaded into exhaust manifold near header pipe flange, where it is exposed to hot exhaust gases. O2 sensor monitors oxygen content of exhaust and produces voltage signal which is directly proportional to oxygen content. This signal is sent to logic module. If oxygen content is high (lean air/fuel mixture), low voltage signal is sent to logic module. As oxygen content decreases (richer mixture), signal voltage becomes higher. Keeping logic module constantly informed of air/fuel ratio allows it to alter fuel injector pulse width (length of time during which fuel is injected). This response to input signals makes it possible to obtain best air/fuel ratio under any conditions.