REMOVAL & INSTALLATION

1. Start the engine and allow it to reach normal operating temperature, then turn the ignition switch OFF.
2. Disconnect the negative battery cable.
3. Open the hood and locate the O2sensor connector. It may be necessary to raise and safely support the vehicle for access to the sensor and its connector.

   NOTE: On a few models, it may be necessary to remove the passenger seat and lift the carpeting in order to access the connector for a downstream O2sensor.

   Fig. 1: Since sensor locations vary between vehicles, the first step in removal is to locate the O2sensors (arrows) . . .

   Fig. 2: . . . and the sensor connector (2), which is usually near the O2sensor (1), but removed enough from the heat of the exhaust system

   Fig. 3: Disengage the sensor pigtail connector half from the vehicle harness connector half

   Fig. 4: For flange type sensors, loosen the hold-down fasteners . . .

   Fig. 5: . . . which happen to be nuts in this particular case — some models may use bolts rather than nuts

   Fig. 6: Then, pull the sensor out of the exhaust component

   Fig. 7: For screw-in type sensors (arrow) . . .

   Fig. 8: . . . either use a box end wrench to loosen the sensor or a socket designed expressly for this purpose . . .

   Fig. 9: . . . then remove the sensor from the exhaust component

4. Disengage the O2sensor pigtail connector from the vehicle harness connector.

   NOTE: There are generally 2 methods used to mount an O2sensor in the exhaust system. Either the O2sensor is threaded directly into the exhaust component (screw-in type) or the O2sensor is retained by a flange and 2 nuts or bolts (flange type).

   WARNING
   To prevent damaging a screw-in type O2sensor, if excessive force is needed to remove the sensor lubricate it with penetrating oil prior to removal. Also, be sure to protect the tip of the sensor; O2sensor tips are very sensitive and may be easily damaged if allowed to strike or come in contact with other objects.

5. Remove the sensor, as follows:
   • Screw-in type sensors: Since O2sensors are usually designed with a permanently-attached wiring pigtail, it may be necessary to use a socket or wrench that is designed specifically for this purpose. Before purchasing such a socket, be sure that you can't save some money by using a box end wrench for sensor removal.
   • Flange type sensors: Loosen the hold-down nuts or bolts and pull the sensor out of the exhaust component. Be sure to remove and discard the old sensor gasket, if equipped. You will need a new gasket for installation.
6. Perform a visual inspection of the sensor. Black sooty deposits may indicate a rich air/fuel mixture, brown deposits may indicate an oil consumption problem, and white gritty deposits may indicate an internal coolant leak. All of these conditions can destroy a new sensor if not corrected before installation.

   To install:

7. Install the sensor, as follows:

   NOTE: A special anti-seize compound is used on most screw-in type O2sensor threads, and is designed to ease O2sensor removal. New sensors usually have the compound already applied to the threads. However, if installing the old O2sensor or the new sensor did not come with compound, apply a thin coating of electrically conductive anti-seize compound to the sensor threads.

   WARNING
   Be sure to prevent any of the anti-seize compound from coming in contact with the O2sensor tip. Also, take precautions to protect the sensor tip from physical damage during installation.

   • Screw-in type sensors: Install the sensor in the mounting boss, then tighten it securely.
   • Flange type sensors: Position a new sensor gasket on the exhaust component and insert the sensor. Tighten the hold-down fasteners securely and evenly.
8. Reattach the sensor pigtail connector to the vehicle harness connector.
9. Lower the vehicle.
10. Connect the negative battery cable.
11. Start the engine and ensure no Diagnostic Trouble Codes (DTC's) are set.