Oxygen (O2) Sensor

Oxygen sensor is mounted in exhaust manifold or exhaust pipe, where it contacts exhaust gases. The O2 sensor generates voltage according to oxygen content of exhaust gases. Voltage will vary from .1 volt (lean condition) to as high as one volt (rich condition).

Sensor will not generate a voltage signal until it reaches operating temperature. Sensor sends voltage signal to ECM, which uses it to obtain correct emissions by adjusting air/fuel ratio. Until sensor is warmed up, ECM adjusts air/fuel mixture based upon preprogrammed tables in ECM memory.