common 4 wire oxygen sensor

Before you replace the oxygen sensor on your vehicle let me make an opening statement. In my own personal opinion this is one of the most often replaced sensors. To make matters worse way too often it doesn’t fix the problem with the car or truck.

In most cases this sensor is not a returnable item at your local parts store because it is considered an electronic component. This is to avoid the try it out before you buy it out driveway warrior. Another problem with replacing the oxygen sensor is deciding which one to replace.

Most vehicles have at least 2 of them installed and four sensor systems are even more common. They are installed in the exhaust stream to sample the exhaust gas.

A check engine light diagnostic trouble code can be set if the part is bad or if the exhaust gas itself is out of balance from a fuel system problem. So how do you determine which oxygen sensor is bad if any. First let’s learn about what an oxygen sensor does and why.

What does an o2 sensor do?

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Testing oxygen sensors

Heated oxygen sensor

Testing oxygen sensors before replacing them is a good idea. This might not be the most common check engine light code but it is very high on the list of would be codes set in the computer’s memory. There are also many different types of oxygen sensor problems.

Often when a mechanic pulls one of these codes his first reaction may be to just go ahead and replace the sensor. There are more than 30 different codes that relate to the oxygen sensor circuit.

Some of these codes are dedicated to the heating circuit and some are dedicated to the power supply. But I believe by far the most common codes relate to the activity and efficiency of the sensor itself.

Not only can there be a wide variety of problems with the circuit that will throw a code for this exhaust stream sensor but vehicle problems can cause the code to set as well. One of the most common problems would be a vacuum leak that throws off the air fuel mixture providing a lean condition that can eventually set a code for lean exhaust.

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