Exhaust Gas Oxygen (O2) Sensor

The O2 sensor is mounted in the exhaust system. It monitors quantity of oxygen in exhaust gas. O2 sensor is constructed of metals (platinum and rhodium) which produce an electrical voltage when hot and in the presence of oxygen. A lean combustion condition, which has a large oxygen content, produces a low voltage signal (approximately .1 volt) and a rich combustion condition, which will have a low O2 content, will produce a higher voltage signal (up to .9 volt). The ECM uses O2 sensor signals to compute fuel injector signals. A DVOM with 10 megohm impedance may be used to check output voltage of O2 sensor.