The O2 sensor on a Mitsubishi Montero measures the exhaust gases coming out of the exhaust for contaminants. This information is sent to the Montero's electronic control unit, and then the air to fuel ratio is adjusted accordingly. After 75,000 miles, the O2 sensor may start to fail. When it finally fails, your vehicle will run very poorly. For the Montero, you can install a universal O2 sensor. These sensors replace the factory sensor.
Loosen the wheel lug nuts on the front of the car by turning them 35 degrees counterclockwise with a tire wrench.
Raise the Montero up onto jack stands. Lift up on the front crossmember with a jack and place jack stands under the front pinch welds of the Montero. Then lower the vehicle onto the stands.
Climb under the Montero and locate the O2 sensor. The sensor is located on the catalytic converter just behind the exhaust manifold.
Remove the electrical leads running to the O2 sensor.
Remove the sensor by turning it counterclockwise with the O2 sensor tool and a socket wrench.
Thread the universal O2 sensor into the converter. The sensor should replace the factory sensor although it may not look exactly the same. The thread count and pitch should fit the existing bung.
Cut and strip the factory O2 sensor harness with wire cutters and strippers so that there is about 1/2 inch of bare wire exposed on the factory harness.
Twist the red lead on the universal O2 sensor to the red lead on the factory harness.
Twist the black leads on the universal sensor and the factory harness together.
Place a small amount of soldering wire over the twisted wires on the red leads and heat the solder with a soldering gun. This will form a positive connection that should not come apart. Repeat this process with the black leads.
Wrap both leads (separately) with electrical tape. The lead wires must not touch each other. Once each lead has been wrapped with electrical tape so that no bare wire is exposed, wrap both wires together with electrical tape.
