Oxygen Sensor: Description and Operation

Oxygen Sensor Wiring Circuit:

Exhaust Oxygen Sensor (02):

The exhaust Oxygen Sensor (02S) is mounted in the exhaust system where it can monitor the oxygen content of the exhaust gas stream. The oxygen content in the exhaust reacts with the oxygen sensor to produce a voltage output. This voltage ranges from approximately 0.010 volt (high 02S - lean mixture) to 0.9 volt (low 02S - rich mixture).

By monitoring the voltage output of the 02S the Powertrain Control Module (PCM) will know what fuel mixture command to give to the injector (lean mixture-low voltage-rich command, rich mixture-high voltage-lean command). This voltage can be measured with a digital voltmeter having at least 10 megohms input impedance. Use of standard shop type voltmeters will result in very inaccurate readings.

An open 02S circuit should set a DTC 13. A shorted sensor circuit should set a DTC 44. A high voltage in the circuit should set a DTC 45. When any of these DTC(s) are set, the vehicle will run in the "Open Loop" mode.