The oxygen sensor supplies the computer with a signal which indicates a rich or lean condition during engine operation. The input information assists the computer in determining the proper air/fuel ratio. A low voltage signal from the sensor indicates too much oxygen in the exhaust (lean condition) and, conversely, a high voltage signal indicates too little oxygen in the exhaust (rich condition).
The oxygen sensors are threaded into the exhaust manifold and/or exhaust pipes on all vehicles. Heated oxygen sensors are used on some models to allow the engine to reach the closed loop faster.
- Disconnect the HO2S.
- Measure the resistance between PWR and GND terminals of the sensor. If the reading is approximately 6 ohms at 68°F (20°C). the sensor's heater element is in good condition.
- With the HO2S connected and engine running, measure the voltage with a Digital Volt-Ohmmeter (DVOM) between terminals HO2S and SIG RTN (GND) of the oxygen sensor connector. If the voltage readings are swinging rapidly between 0.01-1.1 volts, the sensor is probably okay.
See Figure 1
- Warm up the engine and allow it to run at idle.
- Disconnect the O2S.
- Connect a voltmeter between the O2S and a good ground.
- Run the engine at 4,500 rpm until the voltmeter reading indicates approximately 0.7V.
- Increase and decrease the engine speed suddenly several times. Check to see that when the speed is increased, the voltmeter reads between 0.5V-1.0V and when the speed is decreased, the reading is between 0V-0.4V.
- If the actual readings are out of specifications, replace the O2S.
REMOVAL & INSTALLATION
See Figures 2 and 3
- Disconnect the negative battery cable.
- Raise and safely support the vehicle on jackstands.
- Disconnect the oxygen sensor from the engine control sensor wiring.
If excessive force is needed to remove the sensors, lubricate the sensor with penetrating oil prior to removal.
- Unscrew the sensor.
- Install the sensor in the mounting boss, then tighten it to 27-33 ft. lbs. (37-45 Nm).
- Reattach the sensor electrical wiring connector to the engine wiring harness.
- Lower the vehicle.
- Connect the negative battery cable.