Oxygen (O2) Sensor

The O2 sensor is constructed in such way that exhaust gases pass by bottom of sensor. When exposed to O2, sensor produces electrical voltage. This voltage ranges from approximately .1 volt (high O2-lean mixture) to .9 volt (low O2-rich mixture). By comparing amount of O2 present in exhaust gases to amount of O2 in atmosphere, sensor produces signal which is proportional to O2 concentration in exhaust gases. The ECM interprets the electrical signal and adjusts injector pulse width to maintain air/fuel ratio close to 14.7:1.