The oxygen, or o2, sensors on a 2002 Pontiac Grand Prix are located in two places: the exhaust manifold and the exhaust pipe, underneath the vehicle. These sensors measure the amount of oxygen present in the exhaust gas and send this information to the powertrain control module, or PCM. The PCM analyzes this information to calculate the optimum air/fuel ratio for the engine and to determine the effectiveness of the catalytic converter. New oxygen sensors can be purchased from local automotive parts stores and General Motors dealerships.
Place the Grand Prix's gear shift lever in the "P" position. Turn off the engine, engage the parking brake, open the hood and allow the car to cool down for at least 1 hour.
Raise the front of the vehicle using an automotive jack and lower it down onto jack stands. Place wheel chocks behind the rear wheels. Disconnect the negative battery lead using an 8 mm box-end wrench.
Locate the primary o2 sensor at the bottom of the exhaust manifold. It screws into the manifold and has a single purple wire attached to it.
Depress the locking tab on the sensor's electrical connector and remove the connector. Remove the sensor from the manifold using a 7/8-inch box-end wrench. Install the new sensor in the manifold using the 7/8-inch box-end wrench and reconnect its electrical connector.
Crawl underneath the vehicle and locate the secondary o2 sensor in the exhaust pipe, just behind the catalytic converter. It is identical to the sensor located in the exhaust manifold.
Disconnect the sensor's electrical connector and remove the sensor from the exhaust pipe using a 7/8-inch box-end wrench. Install the new sensor using the 7/8-inch box-end wrench and reconnect its electrical connector.
Raise the vehicle and remove the jack stands. Lower the vehicle back to the ground. Reconnect the negative battery lead using an 8 mm box-end wrench. Start the engine and verify that the vehicle operates normally.
