Oxygen (O2) Sensor

The heated oxygen sensor detects amount of oxygen content of the exhaust gases and produces a voltage signal. Engine controller uses this signal to monitor system output signals which control air/fuel mixture.

Variations in voltage signal from O2 sensor serve as air/fuel ratio indicators. Changes occur because oxygen sensor voltage input to engine controller varies. When oxygen content is low (rich mixture), voltage signal will be approximately one volt. When oxygen content is high (lean mixture), voltage signal will be approximately 0.1 volt.

The O2 sensor contains a ceramic heater in the sensor housing. The heater operates on 12 volts. The heater is used in cold starts to help O2 sensor heat up quicker and to maintain the O2 sensor's Zirconia semiconductor at its operational temperature of 932-1112°F (500-600°C).

In "closed loop" operation, engine controller monitors O2 sensor input (along with other sensors) and adjusts the injector pulse width accordingly. During "open loop" operation, engine controller ignores O2 sensor input and adjust injector pulse width to a pre-programmed value based on the other sensor inputs.