Car Engine

Symptoms Of A Bad Oxygen Sensor And What To Do

Mike Cross
Updated Feb 12, 2022
Bad oxygen sensor symptoms

A car has all kinds of components. In order for it to run correctly, they all have to be working the way they are interned to work.

A lot of those components in a car are different sensors. Each sensors task on its own may seem small, but together the sensors in your car control a lot.

In this article, we will be looking at one of those sensors, and that is the oxygen sensor. We will look at the symptoms that happen when your O2 sensor starts to go bad.

Continue reading to learn everything you need to know about your oxygen sensor.

Bad oxygen sensor symptoms
Bad oxygen sensor symptoms


First, before getting into the possible symptoms of a failing O2 sensor, we will look at what the oxygen sensor actually does.

It is essential to understand what it does because then that might help you have an idea what to look for if it starts to go bad.

What the oxygen sensor does is it measures the amount of oxygen that is coming out of the exhaust. Your car's exhaust is the leftover gasses that exit the engine after each time it fires and causes combustion. These gasses go thru the catalytic converter and other parts of the car and then comes out at the end of the vehicle as exhaust out of the exhaust pipe.

The O2 sensor has a probe that is connected to it that hangs down inside the exhaust, and it measures the oxygen level in it. This is important because you want the proper amount of oxygen to make sure that the atmosphere and environment aren’t being damaged by too many CO2 gases coming out of your car.

If the oxygen sensor does not measure the proper amount of oxygen in the exhaust, then it sends a signal to the computer in the car which controls the engine and tells it to adjust the fuel ratio.

If the sensor is working correctly, then everything is good, and the car will continue to run smoothly as it is supposed too.

However, if the sensor is bad or failing, then when the computer changes the fuel mixture it might actually be causing more harm than good. That is why it is essential to be aware of the signs of a bad O2 sensor.


The first sign of a failing oxygen sensor is an obvious one, and that is a check engine light. If your car gets a check engine light, then you should hook a bluetooth OBD2 scanner up to your car and read the code as soon as possible, you can find a suitable one in here.

Once you have the code, you can look up what it means. If it is associated with the O2 sensor, then you know that it is bad. What if your oxygen sensor though is just dirty or not failing enough to trigger a check engine light in the computer of your car, well then there are some other signs of a failing O2 sensor.

The next sign of a failing oxygen sensor is rough driving and idling. If the engine is not running smoothly or efficiently, then that could be an indication that the oxygen sensor is going bad.

That is because an engine that is misfiring or not running efficiently is not getting the proper air and gas mixture. A lot of the car's sensors can cause the fuel mixture to be wrong, and one of those is the oxygen sensor. If you are having a rough ride, then you should check all the different sensors in the engine, and one or multiple of them being dirty or bad is most likely why the vehicle is not running right.

The oxygen sensor is one of them that needs to be checked. This is especially true if you have a rough engine, staling, or hesitation on acceleration mixed with some of the other symptoms.

One of the other symptoms of a bad oxygen sensor is a bad smell in your car. The scent would most likely be of sulfur or rotten eggs. This is because there is not enough oxygen in the exhaust and too much of the harmful gasses are coming out. If you have this smell, then there is a good chance that the O2 sensor is not working right. If the exhaust of your car smells bad, then the oxygen sensor probably needs clean or replaced.

Why Does Car Smell Like Rotten Eggs And What Can You Do About It

The next sign is increased exhaust emissions. If you notice that you have more smoke coming out of your exhaust, then that is a good indication of the oxygen sensor probably not working right. That is because most likely too much fuel is going into the engine causing more smoke and soot to come out.

All of the previously mentioned things can also lead to a loss of fuel economy. That is because you are losing fuel efficiency when you have a bad O2 sensor, so if you notice more fuel consumption than usual, then you should probably check out the oxygen sensor and your other sensors to make sure that they are working right.

What to do?

So, what should you do if you notice these symptoms or have a check engine light saying that your oxygen sensor is bad? Well, the first thing you should do is clean the sensor. This is because a dirty sensor could not be reading things correctly and cleaning it might fix the problem.

If cleaning the sensor does not fix the problem, then the next thing you should do is have the sensor replaced with a new one. Ordinarily, O2 sensors don’t cost too much to have replaced, and the damage that you prevent and the fuel you save will be worth the cost of a new oxygen sensor.


So, as you can see, there are a handful of signs that come with a failing or bad oxygen sensor. The main signs all focus on the engine not running smoothly and also lose of fuel efficiency. Other failing sensors can cause these problems as well though, so it might take time to figure out if it is the O2 sensor or a different one that is causing the issues.

However, if you have an egg or suffer smell, then the chance is good that it is the oxygen sensor. Also, if you have a check engine light, then be sure to check it because the code that it gives will tell you exactly which sensor is bad. Now you know the signs of a bad O2 sensor though, and even more importantly you know what the oxygen sensor does and what to do if yours goes bad.

Mike Cross
Life is too short to drive with stock audio

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One comment on “Symptoms Of A Bad Oxygen Sensor And What To Do”

  1. Hi Guys

    Thank you so much for a wonderful and easy to understand explanation! I was so worried since the auto place told me it should be replaced by the dealer. hmm!! Also, I did not know how serious it was and sounds like it could still drive it for local errands until my son gets back in a few more days. I'll be back!


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