Oxygen sensors — replacement
Note: Because it is installed in the exhaust manifold or pipe, which contracts when cool, the oxygen sensor may be very difficult to loosen when the engine is cold. Rather than risk damage to the sensor (assuming you are planning to reuse it in another manifold or pipe), start and run the engine for a minute or two, then shut it off. Be careful not to burn yourself during the following procedure.
Note: «Upstream» refers to the sensor before the catalytic converter and is also referred to as the Air/Fuel Ratio Sensor (Bank 1, Sensor 1). «Downstream» refers to the sensor after the catalytic converter and is also referred to as the Heated Oxygen Sensor (Bank 1, Sensor 2).
1. Disconnect the cable from the negative battery terminal (see Engine electrical systems).
2. The upstream sensor (see illustration) can be replaced without raising the vehicle. Locate the sensor in the engine compartment and unplug the sensor electrical connector. Also unclip (but don’t disconnect) any interfering coolant hoses from their retainers, as necessary. Unscrew the sensor using a special oxygen sensor socket (tool shown in illustration 10.5).
i. 2 Upstream oxygen (air/fuel ratio) sensor details (radiator hose disconnected for clarity)
A Electrical connector
В Electrical connector
3. If you’re replacing the downstream sensor, raise the vehicle and support it on jack stands. Access the oxygen sensor harness and unplug the electrical connector (see illustration).
i.3 Downstream oxygen sensor connector
4. At first glance, it may look possible to remove the downstream sensor at this stage. However, there might be a lack of ‘wrenching room’ to allow for unscrewing. If this happens to be the case, this section of the exhaust pipe will have to be removed (see illustration). A penetrating lubricant sprayed onto the bolts/ threads will help with removing the bolts.
i. 4 Remove the front (A) and rear (B) exhaust pipe section fasteners
Note: The best tool for removing an oxygen sensor is a special slotted socket, especially if you’re planning to reuse a sensor. If you don’t have this tool, and you plan to reuse the sensor, be extremely careful not to round-off the hex fitting when unscrewing the sensor.
5. Unscrew the sensor from the exhaust manifold or exhaust pipe (see illustration).
i. 5 Use a slotted socket to unscrew the oxygen sensor
6. Apply anti-seize compound to the threads of the sensor to facilitate future removal. The threads of new sensors should already be coated with this compound, but if you’re planning to reuse an old sensor, re-coat the threads. Install the sensor and tighten it securely. For the downstream sensor, install the exhaust pipe section and tighten the fasteners securely.
7. Reconnect the electrical connector of the pigtail lead to the main wiring harness (and attach any connector retaining clips, if necessary).
8. Lower the vehicle (if it was raised), then test drive it and verify that no trouble codes have been set.