In 1993, Jeep upped the ante in the SUV market by releasing the Grand Cherokee, a more luxurious mid-sized SUV. The 2002 Grand Cherokee came standard with a 195-horsepower, 4.0-liter in-line six-cylinder engine. Being an in-line-six engine, federal emission regulations require just two oxygen sensors, one upstream and one downstream. Replacing the two oxygen sensors in a federal emission-compliant 2002 Jeep Grand Cherokee is a straightforward process, but it may require additional heat for those hard-to-remove sensors.
Park the Grand Cherokee on a flat surface and allow it to sit until the engine is completely cool. Allow the vehicle to sit for an additional hour to let the exhaust pipes cool.
Lift the front of the Grand Cherokee with a floor jack and slide jack stands under the frame rails. Lower the SUV onto the frame rails.
Crawl under the front of the Jeep until you have a good view of the bottom of the down pipe – the pipe that bolts to the exhaust manifold. Find the upstream oxygen sensor screwed into the bottom of the exhaust manifold, near the front of the transmission.
Trace the sensor’s wiring until you reach where its harness connects to the Grand Cherokee’s harness. Unplug the oxygen sensor’s wiring harness from the Grand Cherokee’s wiring harness.
Unscrew the oxygen sensor from the exhaust down pipe, using a ratchet and oxygen sensor socket. If the sensor is seized, heat its base with a propane torch, then loosen it. Once the sensor cools, unscrew the sensor from the pipe.
Thread the new oxygen sensor into the down pipe by hand, then tighten it to 22 foot-pounds with a torque wrench and socket.
Connect the oxygen sensor’s wiring harness to the Grand Cherokee’s harness.
Raise the SUV off the jack stands and remove the stands. Lower the vehicle to the ground.
Lift the front of the Grand Cherokee off the ground with a floor jack and position jack stands under its frame rails. Lower the vehicle onto the jack stands.
Position yourself under the vehicle, just behind the transmission and toward the passenger’s side. Find the catalytic converter, the muffler-like component attached to the exhaust pipe. Find the downstream oxygen sensor, which screws into the exhaust pipe right after the catalytic converter.
Trace the downstream oxygen sensor’s wiring upward until you find where it connects to the Grand Cherokee’s wiring harness. Unplug the oxygen sensor’s wiring harness from the Grand Cherokee’s harness.
Remove the oxygen sensor by unscrewing it from the exhaust pipe, using a ratchet and oxygen sensor socket. If the sensor is seized, heat its base with a propane torch, then loosen it. Allow the sensor to sit until it is cool, then continue removing it.
Thread the new oxygen sensor into the exhaust pipe by hand, then tighten it to 22 foot-pounds with a torque wrench and oxygen sensor socket.
Connect the oxygen sensor’s wiring harness to the Grand Cherokee’s wiring harness.
Lift the SUV off of the jack stands and remove the stands. Lower the vehicle to the ground.
