5 bad oxygen sensor symptoms

Every car is equipped with an oxygen sensor. It is an important part that sends the collected data to the car’s computer. The barometric pressure and temperatures are also measured by this sensor, which tells the engine to operate with either a lean or rich mixture. 

As this part goes bad, the readings are no longer accurate, and the functionality of your entire car will have to suffer. The exhaust gas is no longer regulated, and the fuel injection levels are completely misplaced. As a result, your car will consume more fuel while also contributing to environmental pollution.  


The most common reason for oxygen sensors to go bad is lead, dirt, and debris. Symptoms of bad sensors are engine misfiring, catalytic converter failure, engine overheating, poor engine performance, and weird engine noises.

A temporary fix for it is removing the plug from the oxygen sensors and connecting a fake one.

The best scanner for testing the bad oxygen sensor is General Technologies Corp GTC ST05 Tester and Simulator.

Other topics covered in this article are :

  • How to tell which sensor needs to be replaced
  •  How to test it with a scanner
  •  How long does the oxygen sensor last
  •  Replacement cost

Continue reading this article to know the bad oxygen sensor symptoms. We will teach you how to tell if it’s bad and devise a temporary fix. 

A temporary fix

While a complete replacement of this part might be necessary, you can try a temporary fix to be able to drive your car. If the oxygen sensor is not working properly, you will have difficulty commuting to work or cruising down the highway. 

You can get under the car and remove the plug from the oxygen sensors. These should be located within the exhaust system. After you find the O2 sensor, rotate them until they are completely removed. Install a fake one while also connecting it to the power socket. 

Bad oxygen sensor symptoms

There are some specific symptoms you can look for when you suspect that this part needs to be replaced. With these indications, you will realize whether or not the problem comes from this particular sensor.

We’ll take a look at these symptoms of a bad oxygen sensor.

  • Engine misfiring
  • Catalytic converter failure
  • Engine overheating
  • Poor engine performance
  • Weird engine noises

1. The engine is misfiring or stalling.

oxygen sensor on a wooden background

When this component is in perfect working condition, effective combustion is guaranteed. The engine will work without interruptions, and you will not experience any stalling or rough idling. But when the oxygen sensor is failing, you will notice that the engine is often misfiring.

A power loss or complete stalling are common occurrences when the O2 sensor goes bad. These are good indications that you should replace this component, but you should check with a mechanic first.

Error codeExplanation
P0301Misfire in the first cylinder
P0302Misfire in the second cylinder
P0303Several different reasons
P0304A problem caused by the spark plugs and coil packs
P0305Related to the 5th cylinder.
P0306Issues with the air and fuel mix

2. Catalytic converter failure

Because catalytic converters are part of the exhaust system, they are directly related to the oxygen sensors. When they break down, the catalytic converter will also suffer. Fuel contamination and corrosion can also cause damage to this part.

3. Engine overheating

While it is not a common symptom, engine overheating can also be caused by a failing oxygen sensor. However, you should also consider problems with the electrical system. This symptom appears in the later stages when the owner disregards the first warning signs regarding a failing component. 

4. Poor engine performance

Your car will decline in performance as the fuel mixture is completely imbalanced due to the failing part. The loss of power is also caused by the engine misfires and repeated stalling. You should expect to experience these symptoms as your vehicle starts moving from a standing stop.

5. Engine noises

As this component goes bad, you will be able to notice odd and weird sounds coming from the engine bay. A lean mixture results from the lack of air and fuel mixture control. It will cause several noises to emerge as you accelerate your car. 

What is an oxygen sensor in a car?

oxygen sensor

The oxygen sensor is an important component in your vehicle. It measures the unburnt oxygen in the exhaust and communicates this level to the central computer. The computer can adjust the air-to-fuel ratio with this information to obtain the best performance.

Whether you drive a Ford F150 or a Chevy Silverado, every vehicle needs an oxygen sensor. This part has been mandatory since 1981, but newer vehicles can feature multiple oxygen sensors. As catalytic converters are required on every car, an extra oxygen sensor is used for monitoring this part. 

What happens when it goes bad?

When the oxygen sensor goes bad, you will easily notice the symptoms caused by this problem. Firstly, the check engine light will turn on. You can spot this light on your dashboard, and sometimes a specific trouble code will also be shown. Statistically, a bad oxygen sensor is the main reason for check engine lights turning on around the world. 

Another negative effect of a broken oxygen sensor is poor acceleration and higher fuel consumption. The engine cannot regulate the mixture itself without the help of this part which sends accurate data to the car’s computer. 

What does a bad O2 sensor look like?

When this component is failing, the dashboard will inform you by lighting up the check engine light. After you notice this warning sign, you should investigate further and try to identify the problem. Check the engine bay for anything suspicious.

You will most likely notice that the oxygen sensor looks different from a brand-new one. It can indicate that you should replace it with a new one. 

What causes it?

oxygen sensor for toyota

While the components of a vehicle are strong because they are manufactured from durable materials, they all have a limited lifespan. Eventually, these parts will go bad, and you will have to replace them. The oxygen sensor can get damaged by lead or other additives that are found in the fuel.

Oil and ash can also contribute to faster wear. Debris will interfere with the sensor, and inaccurate readings will be sent to the car’s computer, struggling to adjust the fuel mixture. 

How to test with a scanner

Usually, the symptoms that we listed above will tell you when this component goes bad. But suppose your sensor works well, and you want to conduct periodic maintenance. In that case, there is a specific tool that you can use to analyze and evaluate its state.

General Technologies Corp GTC ST05 Tester and Simulator

This high-quality scanner shows the signal output through a bar graph situated on the screen. Live data is provided in real-time, and it keeps you informed about the current state of your sensor.

A test button will allow you to simulate a snap-throttle acceleration of the engine to test the functionality of your O2 sensor. Two more buttons control the conditions based on the fuel mixture, which can be lean or rich. With this tool, you can test the sensor while it is still installed in the vehicle. 

NameGeneral Technologies Corp
AdvantageAbility to test sensor on or off a vehicle
FeatureReal-time output
Item Weight1.75 Pounds


  • We’ve used this kit, and it works really well.
  • It’s easy to attach the wires to the sensor.
  • It feels like good quality.
  • You’ll save a lot of time with this unit.


  • We had issues getting in touch with customer support.
  • The instructions included could be better.
  • It’s more expensive than your basic test kit.
General Technologies Corp GTC ST05
It is great for testing your car.

Is it a bad oxygen sensor or catalytic converter?

As their symptoms are somewhat similar, identifying the problem can be difficult when you don’t know whether the oxygen sensor or the catalytic converter is broken. Both of them will display the same P0420 trouble code, so this is not entirely helpful to you.

The best way to determine which part is broken is by checking them manually. Investigate under your car and take a look at the exhaust system. If you cannot do this yourself, ask a professional mechanic to help you. 

Can you drive regardless?

Bosch oxygen sensor

Because it is not a mandatory part like the muffler or catalytic converter, you can still drive your vehicle without an oxygen sensor. However, you will struggle a lot and notice a major decrease in performance. Your driving experience will no longer be smooth. 

The significant reduction in performance is not the only effect a bad component will have on your car. Several more problems can occur if you do not fix this issue as soon as possible. 

Replacement cost

While the most expensive part of your vehicle is the catalytic converter, an oxygen sensor can be quite pricy too. If it goes bad, replacing this part will cost you between $155 and $500. This price range does not include the labor costs, which you will have to pay separately if you seek help from a professional mechanic. 

If you have some basic skills in mechanics and engineering, you can replace this part yourself. The total cost will be lower since you are not spending any money on labor fees. 

Oxygen sensor replacement

How to pass emissions test despite not replacing it

While several workarounds are available for car problems, this one has no way of cheating. An emissions test is important, and the problems with your exhaust system will be easily detected.

If this part fails during an emissions inspection of your car, you will not pass the test. That is why the replacement of this broken component is something you should consider as soon as possible. 

How to tell which sensor needs to be replaced

When there is something wrong with this part, the symptoms that signal this problem will make you aware of it. You will notice that the engine is misfiring and has a rough idling. The check engine light will also appear on the dashboard, and you will know it’s time to see a mechanic.

They can spot the faulty oxygen sensor by using special tools such as the scanner we recommended above. This scanner tests the functionality of each sensor, and the bad ones can easily be spotted. 

Should I replace them all at once?

Bosch single wire oxygen sensor

When you want to replace all of your oxygen sensors, it is recommended to replace them in pairs. The models manufactured after 1996 will display an error code once a new component is detected. It is because the switching activity on the brand-new one is much faster than on the others. Usually, this code will go away within 30 days after the first replacement. 

Can it cause an engine to misfire?

While engine misfires can happen for several reasons, most are related to the fuel mixture or the fuel injectors. Your car’s engine requires a balanced mix of raw fuel and clean air. When the oxygen sensor is failing, this mixture will not be balanced.

As a result, the combustion process will be irregular, and your engine will often experience misfirings. The fuel economy is also negatively impacted, and several more problems can develop over time if you decide to ignore this situation. 

How long do they last?

While these are strong and durable parts, the oxygen sensors will last you a long time. On older vehicles, you can expect them to go bad after 30,000 to 50,000 miles or after 3 years. Because they are older, their lifespan is already limited.

But new vehicles manufactured today feature oxygen sensors equipped with an additional heated element. They are more durable and can last for up to 100,000 miles or 10 years before they need a complete replacement. 

Oxygen sensor for Honda cars 10$

Have you noticed any of these symptoms?

  • Catalytic converter failure
  • Engine overheating
  • Poor engine performance
  • Weird engine noises

We will be happy to hear your thoughts

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