Oxygen Sensor

This sensor is mounted in engine exhaust stream, in front of catalytic converter. It supplies a low voltage (under .5 volt) when fuel mixture is lean (too much oxygen) and a higher voltage (up to 1 volt) when fuel mixture is rich (not enough oxygen).

The oxygen sensor must be hot (over 480°F/250°C) to function properly, and to allow CU to accept its electrical signals. The oxygen sensor measures quantity of oxygen only.

All Calif. models are equipped with a special electrically heated oxygen sensor. This oxygen sensor reaches operating temperature sooner and also begins to function earlier. The heated oxygen sensor has 3 wires, 2 for the heater element (power and ground), and a single wire for the oxygen sensor signal.

The heating begins with ignition on (via fuel pump and DME relay terminal 87). The plugs from the sensor to the wiring harness are located near the flywheel sensor plugs (speed, reference mark).

NOTE: No attempt should be made to measure oxygen sensor voltage output. Current drain of conventional voltmeter may permanently damage sensor, shift sensor calibration range and/or render sensor unusable. DO NOT connect jumper wire, test leads or other electrical connectors to sensor. Use these devices only on CU side of harness after disconnecting sensor.