Oxygen Sensor: Description and Operation

The oxygen sensor is positioned in the exhaust system ahead of the catalytic converter. It provides air/fuel mixture information to the ECM by measuring oxygen content in unburned exhaust gasses against an atmospheric reference calibration. The sensor emits a low voltage signal (under 0.2 volts) when fuel mixture is lean and a higher voltage (up to 1 volt) when mixture is rich. Voltage signals are not supplied by the sensor until exhaust temperature reaches 600°F. The ECM uses these signals to control Mixture Control (MC) solenoid operation.