The oxygen sensor is mounted either in the exhaust manifold or the exhaust pipe. Some vehicles use two oxygen sensors. The output signal from the sensor, which varies with the oxygen content of the exhaust gas stream, is sent to the ECM for use in controlling closed loop fuel delivery. The oxygen sensor must at a certain temperature to function properly. Some sensors contain an internal heater to boost sensor temperature during cold starts.
See Figures 1, 2 and 3
- Start the engine and allow it to reach operating temperature.
- Disconnect the oxygen sensor connector.
Measure resistance between the sensor signal and ground terminals
- With the engine idling, voltage should be 400 millivolts or less.
- When the engine is suddenly accelerated, voltage should be 600-1000 millivolts.
- When the engine is suddenly decelerated from 4000 rpm, voltage should be 200 millivolts or less.
If sensor is equipped with a heater (3 or 4 terminal connector), measure resistance between the heater positive and negative terminals.
- With the heater at 750°F (400°C), resistance should be 30 ohms or more.
- If voltage or resistance is not within specification, sensor is faulty.
- If voltage and resistance are within specifications, check power and ground circuits.
REMOVAL & INSTALLATION
See Figures 4 through 11
- Disconnect the negative battery cable.
- Remove the exhaust heat shield as necessary to gain access to the sensor.
- Label and disconnect the sensor electrical harness
Special oxygen sensor wrenches are available from local tool suppliers.
- Carefully remove the sensor using an appropriate wrench.
- Lubricate the sensor threads with antiseize compound.