Bad Oxygen Sensor Symptoms  – Fixes and Prices

A sensor in our cars is a very important part. Especially in modern vehicles, lots of systems depend on the sensors. And if we have a problem with one sensor, you will feel some serious symptoms. Here we explain the general bad oxygen sensor symptoms that you need to know in general. And you will learn about the general fixes of the problems. And we try to give information about the general fixing prices for them.

Common Symptoms of Faulty Oxygen Sensor

Common Symptoms of Faulty Oxygen Sensor
Image Source: iStock

First of all, we need to understand the general duty of the oxygen sensor to understand the general symptoms. The main duty of the oxygen sensor is to provide the oxygen levels in the exhaust fumes to the ECM of the car. ECM or engine control module adjusts the required amount of fuel that goes to engine cylinders according to the oxygen level in exhaust gases.

The oxygen inside the exhaust gas indicates that there is no used fresh air inside the exhaust. So, with the increasing oxygen inside the exhaust fumes, the ECU system increases the total fuel that comes into the engine cylinder. For optimum burn of the exhaust gases inside the engine cylinders, the oxygen sensor must send the correct information to the ECM.

And if you have a problem with the oxygen sensor, the sensor can not send the correct information to the ECM. And ECM can not adjust the required amount of fuel to the engine cylinders. Also this will cause such problems and symptoms.

Engine Noise

The first and the most common symptom of bad oxygen sensors is the strange soıunds coming from the engine. Because the burn of the exhaust gases does not take place in the intended way.


Misfires are the non-common fire of the air-fuel mixture in the engine cylinders. In general, the burn of the air-fuel mixture inside the cylinders takes place when the cylinder is at the top dead center. Once the spark plug ignites the mixture, the burn takes place.

So, if the air-fuel mixture is not in the intended composition, the fires can take place at unintended times. And this will cause misfires which can harm the engine and the other components. The efficiency and performance of your car will decrease.

Rough Idling and Stalling

The common reason for the rough talking is the misfires. Because the fires do not take place at the intended times. And because of this reason, rough idling becomes a problem in general. You will hear strange and harsh sounds coming from the engine.

Stalling is the inability to fire the air-fuel mixture inside the engine. Because of this, the engine can eventually stop or stall. You will feel a very decreased performance abruptly.

Reduced Engine Performance

Bad Oxygen Sensor Symptoms

As you see above, not-optimum fires inside the engine cylinders take place because of the bad oxygen sensor. And this will reduce the engine performance in a very bad way. So, once you push the gas pedal, you will not take the same amount of power from the engine.

Black Exhaust Fumes

The exhaust fumes are also will change. Because the engine can expel an amount of unburned fuel with unused air from the exhaust. And this will cause bşlack exhaust fumes. This is a very important symptom that you generally see if you have a problem with your oxygen sensor.

Rotten Egg Smell from Exhaust

The catalytic converter will not work well as intended way because of the bad oxygen sensor. The main duty of the cataşlytic converter is to convert poisonous gases into less harmful gases. But this is valid for the even working conditions of the engine. The exhaust fumes will not be the same if there is a problem with the oxygen sensor. And catalytic cıonverter can not convert the bad gases to normal exhaust gases. This can cause very bad smells to come out of your exhaust.

Problems with Catalytic Converter

This is another important bad oxygen sensor symptom. As we stated above, the catalytic converter will not work properly. Because it is not receiving normal exhaust gases coming from the engine cylinders. And the catalytic converter would eventually fail because of the very bad exhaust fumes going through it.

The catalytic converter has very detailed and narrow channels that the exhaust fumes go through. And if there will be very bad exhaust fumes going through the converter like this, this cause very bad problems such as clogging of these channels.

Decreased Fuel Economy

As you understand that the oxygen sensor helps the ECM system to adjust the level of fuel inside the engine cylinders. So, the ECM system adjusts the optimum amount of fuel for optimum power. And if there is a problem with the oxygen sensor, the ECM system can not decide the optimum amount of fuel. So, you will face decreased fuel economy.

Check Engine Light On

One of the most common symptoms of a bad oxygen sensor is the check engşne light will be on on the dashboard. Because you have a problem with one of the most common parts of your engine system.


Do not forget that all the systems of your engine are designed to work with optimum air-fuel mixture and fire in your engine. And if there is a problem with the oxygen sensor, the air-fuel mixture will not be at the intended level. So, the cooling system is also designed for this optimal working condition. Misfires will take place and this can create increased heat inside the cylinders. And the capacity of the cooling system can not be sufficient for this situation. So, it is possible to see overheating problems with your engine.

Failing in Emissions Tests

As we stated above, the catalytic converter of your car will not work properly. You may fail emission tests. Because the ingredients of the exhaust gases will worsen because of the noın-functioning catalytic converter. And your car will fail emission tests and you can not get the certification for availability to traffic.

Where is the Oxygen Sensor Located?

Before applying the general fixings, you need to know the location of the oxygen sensor on your car. The location of the oxygen sensor is generally right after the catalytic converter. The place of the catalytşic converter is after the tailpipe under your car. You can see a bumpğy shape in the way of the exhaust line. And you can see the attached oxygen sensor after the catalytic converter.

In general, the oxygen sensor is attached to basic fasteners and straps. You need to detach these fasteners with a basic screwdriver set or a basic wrench set. And also you need to disconnect the cable connections carefully if you need to detach the oxygen sensor.

How to Fix Bad Oxygen Sensor?

Before starting to fix the bad oxygen sensor, we need to find the exact problem. The possible reasons that cause the bad oxygen sensor;

  • Problems with wiring: The oxygen sensor is connected to two systems with wiring applications. The first one is the connection with the battery to get electricity to work. And the sedoın wiring is the connection between the ECM and oxygen sensor to send data. So, if there is a problem with the electric wire, the oxygen sensor will simply not work. But also if there is a problem with the data cable, the ECM system can not receive the oxygen level data.
  • Filthy oxygen sensor: Also the oxygen sensor can get filthy over time. Because it is directly exposed to exhaust fumes coming through the exhaust system of your car. And carbon buildup can be a serious problem that prevents the reading of oxygen sensors.
  • Bad or faulty oxygen sensor: Or, directly there is a problem with the oxygen sensor. You just need to change it with a new one.

Check Cables

If you have a problem with the wiring, you need to check the connections first. Check the connections with the battery and sockets so that the oxygen sensor receives electricity. And also check if there is a problem with the data cable that can sensor send the oxygen işnformatioın to the ECM. If there is a problem with one of these connections, attach the plugs and sockets firmly. And also if there is a problem with the cable connections, you need to change the cables.

Clean the Oxygen Sensor

If there is a carbon build-up problem on your oxygen sensor, you need to clean it thoroughly. You should detach the oxygen sensor and check if there is a carbon buildup on the edge of the sensor. If the edge of the sensor is very black, you need to clean it. There are special solutions that ıu can use for oxygen sensor cleaning. You can find these solutions in the typical automobile markets. Just apply the user instructions on the package to apply the solutions.

Changing the Oxygen Sensor

Also, you can purchase a new oxygen sensor and change it with the old one. You just need to be sure that the sensor that you buy is made with the old one. And also you need to be sure that it is an OEM part, not an aftermarket part. Because your engine can have problems with the aftermarket parts.

What are the Prices of Fixing a Bad Oxygen Sensor?

The prices of the oxygen sensors can change according to the brand and model. Because the oxygen sensor of the Porsche 911 will not be the same as the Nissan Altima. But if you have an average passenger car such as Nissani Toyota or Ford, the total price of them generally changes between $50-$150. And if you are not familiar with the car mechanics and if you bring your car to service, the total cost of the replacement will cost around $250 including the inspection and expertise.

And also if the problem is on the wires, the total wire replacement including all costs can be around $100.

Conclusion on Bad Oxygen Sensor Symptoms

These are the general things that you need to know about the bad oxygen sensor symptoms. We have all the possible fixes and problems also. And we added the general prices that you may pay for faulty oxygen sensors.

If you have additional comments and questions, please leave them below.


What happens when the oxygen sensor goes bad?

The main duty of the oxygen sensor is to send the oxygen level information to the ECM system of your car. And the ECM system will adjust the level of fuel according to this feedback. And it will adjust the maximum level of fuel. But, if you have a problem with your oxygen sensor, the system can not adjust the optimum amount of fuel to burn. You may face misfires, strange sounds, performance loss, fuel efficiency decrease, etc.

Can you drive with a bad oxygen sensor?

Problems with oxygen sensors are generally considered an immediate problems to be solved. Because your engine will have a major problem if you continue to drive without the oxygen sensor. Yes, your car may run without that part. But if you ignore the problem, you may harm your vehicle in a much more bad way.

How do I know if I have a bad O2 sensor or catalytic converter?

A catalytic converter must convert the bad exhaust gases to less harmful gases to expel into the atmosphere. So, the catalytic converter has nothing to do with the combustion inside the engine cylinders. And if you have misfires, engine stalls, and very bad performance loss, probably the problem is the oxygen sensor. And if you are hearing strange sounds coming from your catalytic converter, the problem is generally with the catalytic converter.

Can the oxygen sensor be cleaned?

Yes, you can clean the oxygen sensor if you are familiar with the car mechanics. You should clean the carbon buildup on the top section of the oxygen sensor of your car. And the sensor will start to work much more properly.

What is the average life of an oxygen sensor?

It changes according to if you are using aftermarket parts or OEM parts. If you are using an OEM part, the general lifespan will be around 30.000-50.000 miles.

Uğur Uygun

Hello everyone, I am Uğur. I am a mechanical engineer who has experience in different R&D departments of HVAC companies. With my best friend, I decided to build this website to share out knowledge and experience. And also, I am interested in automotive. So, I am writing about automotive and automotive-related articles here. Sharing my knowledge and experiences on these topics is a very big pleasure for me. I am willing to answer all of the questions people have about these topics.

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