How To Replace Your Oxygen Sensor

01
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Does Your Oxygen Sensor Need Replacement?

An illuminated CEL may mean repairs are needed.
The repair bill classic, the Check Engine Light. photo CC Licensed by Dinomite

Is your Check Engine Light haunting you from the dash like a tiny, orange, burning ember? If it is, there's a fairly good chance that a bad O2 sensor is causing the problem. These sensors go bad all the time. Some experts say that new fuels with higher ethanol content are causing parts of our cars, including the O2 sensors, to go bad prematurely. Whether this is the case or not, if your CEL (Check Engine Light) is on you won't be on the road much longer thanks to most states' inspection programs.

Of course before you go replacing an O2 sensor you'll want to be sure that's the problem. Even the parts are expensive, not to mention the labor if you're paying a shop to do the work for you. A Check Engine Light can mean a lot of things, and even though the oxygen sensor is often the culprit, there are hundreds of other possibilities.

How do you know if your car or truck needs a new O2 sensor?

The answer to this question is simple. Your Check Engine Light is on because the computer is "throwing a code." In tech speak this means that the computer has detected a malfunctioning system, and has produced an error message which caused the Check Engine Light to come on. With a code reader, you can read this error, called an OBD Code, and determine if the O2 sensor is the culprit. If you don't have a code reader, there's a free and easy way to retrieve that error message. Learn how.

02
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What Type of O2 Sensor Do You Have?

Oxygen sensor ready for installation.
This is a typical screw-type O2 sensor ready to be installed. photo by John Lake, 2011

The question of whether or not you can replace your own O2 sensor will probably be answered by figuring out what type your car or truck has. There are two types of sensor, a screw-in type and a weld-in type. Needless to say there are a lot of differences in what goes into the installation of these two types of sensors. Save yourself some time and energy by figuring it out ahead of time.


The best way to determine what type of O2 sensor you have is to consult your repair manual, or simply ask the clerk at the auto parts store. They can look up your car by make and model and tell you in less than 5 minutes whether you are on the road to a DIY job, or headed to the repair shop. If you are blessed with the screw-in type, read on and you can replace your own. You'll save major bucks. If you are cursed with a weld-in type sensor (unless you're a welder) you probably need to head to the repair shop for this job. Don't try to install a weld-in O2 sensor with something like epoxy -- it won't stand up to the task.

03
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Oxygen Sensor Removal

Remove the old sensor.
Removing the old O2 sensor with the special oxygen sensor removal tool. photo by John Lake, 2011

Now that you have determined that you have a screw-in type O2 sensor and you think you can tackle the task of installing it yourself, let's get to it. The good news is once you get to it, the job isn't super tough. Start by spraying the sensor with a good penetrant to loosen it up a bit. The constant heating and cooling of that area can make any bolt tough to remove. If you want to do this job more safely and easily, I recommend buying a proper oxygen sensor wrench. This will ensure an easy removal of the old sensor without damaging any of the delicate wires hanging out of it.
If your O2 sensor is being stubborn, you may have to apply the added force of a breaker bar to get it out of there. This is not uncommon, so don't be afraid to add some leverage to the equation.

04
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Installing Your New O2 Sensor

The O2 sensor has declicate wires.
Oxygen sensor wiring being reattached. photo by John Lake, 2011

With your old sensor out, you are ready to get the new one in. Start the installation by hand so you can be sure you don't crossthread the expensive new sensor. That would suck. Using the same wrench you used to safely remove the old oxygen sensor, install the new one tightly. You can now reconnect the wiring to the sensor. Once you've done that, the job is done!

*If your Check Engine Light was on before this repair, it may go out by itself when your car's computer starts analyzing the new data. If it doesn't you can try disconnecting the battery overnight for reset, or take it to a shop and ask them to reset the light for you.