How to Replace an O2 Sensor on a 2002 Dodge Ram 1500. To run efficiently, your pickup's engine relies on sensors that measure the oxygen in the exhaust gases. The engine computer reads the measurements and adjusts the fuel mixture to optimize performance. An oxygen sensor or O2 sensor that works incorrectly can cause a too-rich or too-lean fuel mix. On Dodge's 2002 Ram 1500s equipped with 3.7-liter six-cylinder engines, two oxygen sensors are located on each exhaust pipe. One sensor is before the catalytic converter; the other is after it on the two pipes -- a total of four oxygen sensors on the 2002 Ram 1500. Make sure you know what sensor specifically needs to be replaced before performing this procedure.
Park the Ram on a level surface and set the parking brake. Raise the front of the truck with a floor jack so you can place jack stands under the frame rails. Lower the truck until it sits securely on the jack stands. Allow the engine and exhaust to cool completely before continuing.
Locate the sensor to be replaced. All four oxygen sensors are located near the transmission. Follow the oxygen sensor pigtail wiring to its connection at the vehicle wiring harness. Squeeze the locking tab and remove the pigtail connector from the harness connector.
Spray penetrating oil around the base of the oxygen sensor and allow it to work into the oxygen sensor threads. Install the oxygen sensor socket over the oxygen sensor. The pigtail should extend through the cutout in the socket. Rotate the oxygen sensor and socket counterclockwise with a ratchet to remove it. If the oxygen sensor will not remove easily, apply heat to the exhaust pipe around the oxygen sensor with a propane torch. Remove the oxygen sensor from the exhaust pipe.
Inspect the new oxygen sensor for anti-seize compound; apply a coat if needed. Thread the oxygen sensor into the exhaust pipe by hand. Tighten the oxygen sensor to 22 foot-pounds with a torque wrench and an oxygen sensor socket.
Route the oxygen sensor pigtail to the wiring harness connection. Push the oxygen sensor pigtail connector into the wire harness connector. The locking tab should click lightly when properly connected.
Lift the truck and remove the jack stands. Lower the truck to the ground. Start the engine and check for any exhaust leaks around the new sensor. The "Check Engine" light may take a few driving cycles to shut itself off, or you can clear it with a scan tool.