Like most cars manufactured after 1990, the 2000 Chevy Malibu actually has two oxygen sensors. These sensors test and monitor the emissions in the Malibu's exhaust manifold, and the Malibu's computer uses the gathered information to adjust the mixture of air and fuel going into the combustion chambers of its engine. When an oxygen sensor goes bad, the amount of harmful emissions the Malibu puts out can increase significantly, which can easily cause your car to fail a smog test.
Raise your Malibu off the ground with your jack, then settle the car down on the jack stands.
Locate your oxygen sensor by starting at the back of your exhaust manifold and moving up toward the front of the car. The oxygen sensors look like fat cylindrical pegs with a thick wire coming out of the tip, and are located in the exhaust manifold just before and just after the catalytic converter.
Unplug the oxygen sensor wire from your Malibu's wiring harness. Take care when pulling the plug out that you do not damage the electrical socket on the car; doing so may make it impossible for your new oxygen sensor to function properly.
Use your wrench or ratchet and socket to loosen and remove the oxygen sensor from the exhaust manifold. Because of their location, and the high temperature they are constantly subjected to, oxygen sensors often stick or "freeze" in place, and may require extra force be applied to loosen them. Discard the old oxygen sensor once you have gotten it loose.
Apply WD-40 or an anti-seize compound to the threads of your new oxygen sensor. This will make installation and removal much easier, and will also help prevent damage to the screw threads.
Screw your new oxygen sensor into the exhaust manifold and tighten it down securely. Once the sensor is properly installed, connect the wire back into the electrical socket mentioned in Step 3.
Repeat Steps 2 through 6 for the remaining oxygen sensor, if necessary.
