Oxygen Sensor: Description and Operation

Oxygen Sensor:

The Oxygen (02) Sensor 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 sensor to produce a voltage output. This voltage ranges from approximately 0.1 volt (high 02 - lean mixture) to 0.9 Volts (low 02 - rich mixture). This voltage can be measured with a digital voltmeter having at least 10 Meg ohms input impedance, or displayed on a scan tool. Use of standard shop type voltmeters will result in very inaccurate readings. By monitoring the voltage output of the 02 sensor, the ECM will know what fuel mixture command to give to the injector (lean mixture - low 02 voltage = rich command, rich mixture - high 02 voltage = lean command). The O2 sensor circuit, if open, should set a Code 13. A constant low voltage in the sensor circuit should set a Code 44. While a constant high voltage in the circuit should seta Code 45. Codes 44 and 45 could also be set as a result of rule system problems. See appropriate code charts.