Q&A for How to Change an Oxygen Sensor

New oxygen sensors often come with an anti-seizing or anti-corrosion lubricant that should be applied to the sensor when it's being installed. That will keep the threads on the sensor from seizing, which happens when temperatures fluctuate on the vehicle.

It should only take a few minutes depending on your experience level.

It will run, but poorly since the ECU won't know how efficient parts of the exhaust are. It won't sound very good, and it won't run very well, so I don't recommend it.

It can be done in some cases without a special socket, but normally yes you should have the proper socket. Call your local NAPA store to be sure.

It depends on your exhaust system. Probably just two, but it could be four if you have dual exhaust. They are always one in front of the catalytic converter (the skinny muffler looking thing in the exhaust line close to the engine), and the second just downstream from the cat. They are usually rated as S11, S12, S21, and S22 which are designations for bank and front or back. For example, S11 would be bank 1 (which is the #1 plug side for V-type engines) front.

No, there is no need to disconnect the battery when replacing O2 sensors.

It is not under the hood. Look for a spark plug-looking part with a wire coming out of it somewhere along your exhaust pipe system. You may have more than one. Unplug the wire at the connector and remove O2 sensor. They do sell a special tool, but you can do it with a crescent wrench. Use some liquid wrench first. Apply anti-seize to the threads of the new O2 sensor for ease of installation and reconnect the wire.

No, this is not possible. There are always a minimal of 2 oxygen sensors to compare values to the ECU.

You should replace it all at once. The oxygen sensors will make sure that your car has plenty of oxygen and won't suffocate and, for that reason, it's important to replace all your oxygen sensors.

Left bank is the left side of the engine, and right bank would be the right side of the engine as you sit in the car looking out. The sensors would be called upstream and downstream, with upstream being closest to the front and downstream being towards the back of the car.

Check the owner's manual or search the make and model online. You should be able to find out that way, although you are also likely to find out by searching for them on your own. Fortunately, they are pretty easy to spot.

The sensor stops reading the amount of oxygen in the exhaust. That means that the vehicle then uses the wrong amount of oxygen in the fuel. Since the fuel ratio is wrong, the car gas much less efficiently. You may notice you get less mileage out of a tank of gas, or notice odd things like the car struggling to start.

Your vehicle's engine management warning light will be on. Plug in an OBD scanner as described in part one/step one to verify whether the sensor is the cause of the issue (or not!).

First, attach an OBD2 code scanner ($20-$30) to the 16 pin plug under the dashboard and see what code it says is malfunctioning. If you've just replaced that item, then simply use the OBD2 to "reset" the "Check Engine Light". Don't disconnect your battery or pull any fuses, unless you have tried everything else first. Doing so could cause your electronics in the car to not work properly until you re-enter the manufacturer codes. And it can be a pain to track them down online or through dealerships. The OBD2 scanner should do the trick for you.

Use a $25 OBD2 Diagnostic scanner to pinpoint the defective part. It'll tell you exactly what's wrong. Then, when you replace the item, simply use the OBD2 to "reset" the "Check Engine Light". Don't disconnect your battery or pull any fuses, unless you have tried everything else first. Doing so could cause the electronics in your car to not work properly until you re-enter the manufacturer codes.

It comes already attached to the sensor when you buy it. It's all attached as one piece. But screw the sensor in first, and then connect the plug. Or else, you'll twist up the wiring and possibly break it. Or did you mean, how do you get the plug in? If the latter, then there's a little tab you hold in as you plug it in and you'll hear it snap into place. You screw in the other end with a ratchet wrench, an open end wrench, an adjustable wrench (crescent), etc. Screw it in hand tight, tightly, then give it one turn with a wrench.