Oxygen Sensor
The oxygen sensor is located in the exhaust pipe to measure oxygen content of exhaust gases. The oxygen content reacts with the oxygen sensor to produce a voltage output signal. This signal is low (about .1 volt) when a lean mixture is present and high (about .9 volt) when a rich mixture is present.
When the ECM reads the voltage signal from the oxygen sensor, the ECM will alter commands to the M/C solenoid to produce either a richer or leaner mixture. The oxygen sensor does not function until its temperature reaches 600°F (316°C). A problem in the oxygen sensor circuit may set a Code "13", "44", "45", or "55".
CAUTION:
DO NOT attempt to measure oxygen sensor output voltage. Current drain of voltmeter could damage the sensor. DO NOT connect any wiring or test equipment to the sensor.