The 1987 Jeep Cherokee featured a single "upstream" oxygen sensor near the exhaust manifold on the driver's side of the lower engine. It wasn't until 1996 that the Cherokee also featured a "downstream" sensor, due to the implementation of the second phase of on-board diagnostics. While the upstream sensor detects the fuel-to-air mix and transmits the data to the electronic control module (ECM), the ECM makes adjustments to keep the mixture as perfect as possible to emit the least amount of harmful emissions, while keeping the vehicle running well.
Tools Used: Set of car ramps, Safety glasses, 22 mm closed-end/open-end combination wrench, Replacement Oxygen sensor
Install Oxygen Sensor
Drive the 1987 Jeep Cherokee onto the car ramps on a paved and level surface. Apply the parking brake and open the hood.
Put on the safety glasses and crawl under the front of the Cherokee to locate the front exhaust pipe on the lower, driver's-side area of the engine. Follow the front pipe upward to the manifold until you locate the oxygen sensor. It is screwed into the pipe just below the manifold and pipe mating flanges.
Follow the oxygen sensor wire to the wire harness plug about 6 inches away. Lift up on the locking clip of the oxygen sensor wire and pull its plug from the wire harness plug.
Place the oxygen sensor plug and wire through the closed end of the wrench and then place the wrench onto the sensor. Sharply tug on the wrench in a counterclockwise way to break the sensor free from the sensor port. Unscrew the sensor to remove it from its port.
Check the box of the replacement sensor. Check the threads of the sensor to determine if there is a compound on the threads or a small tube of it in the box. If applying the compound to the threads is required, put a thin, even coat on the threads, being careful not to get any on the tip of the sensor.
Screw the sensor into the port by hand as far as it will go. Tighten the sensor snugly with the open-end side of the combination wrench. Plug the sensor wire back into the wire harness plug.
Remove the tools and old sensor from underneath the Cherokee, close the hood, release the parking brake and drive it off the ramps.
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