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How to Replace the Oxygen Sensor on a 2001 Saturn SL

There are two oxygen sensors integrated into the exhaust system of the 2001 Saturn SL. The sensors help the 1.9-liter four-cylinder engine generate an ideal fuel-to-air ratio for optimum emissions. One sensor is located near the manifold and monitors this mixture. If the mixture becomes compromised (too much air makes the mix too lean; too much fuel makes the mix too rich), the sensor transmits a trouble code to the computer in the car. The rear sensor monitors the efficiency of the catalytic converter, which filters the harmful exhaust gases and converts them into less-harmful emissions.

Instructions

Upstream Sensor

1

Start the engine of the Saturn on a level ground for at least five minutes to warm the engine. This will help expand the metal of the manifold and sensor junction. Be caul and dont let it run too long, because it wont take long for the manifold and sensor to get hot enough to burn you.

2

Open the hood and locate the upstream sensor at the bottom of the manifold in the front of the engine. Disconnect the wire harness plug connection.

3

Spray penetrating lubricant along the threads of the sensor where it screws into the manifold and allow it to soak in for a few minutes.

4

Place the socket onto the ratchet and place the sensor wire into the slot of the socket (or feed the wire through the box end of a 22mm wrench) and turn the sensor counterclockwise to remove it from the manifold.

5

Inspect the new sensor before inserting it into the port hole in the manifold. Most quality aftermarket sensors have a light coat of high-temperature anti-seize compound on the threads of the sensor. If there is none on the threads, apply a very light coat to the threads only. Avoid getting any on the sensor itself.

6

Thread the sensor into the manifold porthole by hand, then tighten snugly. Do not over-tighten the sensor or youll strip the few threads it has and will ruin it. Plug the wire from the new sensor back into the wire-harness connector.

Downstream Sensor

7

Park the Saturn on a hard, level surface and then apply the parking brake (after warming the engine for five minutes; again, this will expand the metal of the exhaust pipe and sensor junction). Use the vehicle jack to lift the front of the Saturn, one front quarter panel at a time, high enough to place a jack stand under each front frame rail.

8

Put on safety glasses and crawl underneath the Saturn with the remaining items.

9

Locate the downstream sensor near the catalytic converter (in the center of the undercarriage under the front seats of the passenger cab).

10

Disconnect the wire-harness connection, then spray the threads with penetrating lubricant. Allow a few minutes to let the spray soak in. Use the ratchet and socket or 22mm wrench as described in Step 4 of Section 1 to remove the sensor from the exhaust piping.

11

Insert the new sensor (again making sure it has a light coat of high-temperature anti-seize compound on the thread section only) into the porthole of the exhaust pipe, and tighten snugly. Reconnect the wire of the sensor to the harness plug connection.