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What Is an Oxygen Sensor?

Published by: Jack
Date of Publish:

In a vehicle, the air-fuel ratio of the exhaust should be in optimal numbers for the catalytic converter and in turn the engine to work perfectly. But the car itself doesn’t know what the ratio of oxygen is in the exhaust to adjust it. So, there is a part in the vehicle, called the oxygen sensor, which ensures that the oxygen in your car’s engine or the air-fuel ratio is optimal.

Oxygen sensors are found in all automobiles today and they have more functions as well. If you have a car, you must be aware of this mechanical component in the vehicle and how it works, so you can handle the issues when they arise. Keep reading to know all the details about oxygen sensors in your car.

What is an Oxygen Sensor?

You can find an oxygen sensor in the exhaust system of your vehicle. It looks similar to a spark plug and is the same size. The oxygen sensor exists in two different settings concerning the converter. You can arrange it before the converter or after the converter. Setting it before the converter is called upstream, and setting it after the converter is called downstream.

Most vehicles today have four oxygen sensors. The exact number of sensors a car has depends on the model, make, and year of the car. In most cars, one of the sensors is arranged in an upstream setting where the oxygen sensor is arranged before the converter.

How Does an Oxygen Sensor Work?

If your car was manufactured after 1980, it will have an oxygen sensor. All cars after the time had this component embedded in the vehicle. The oxygen sensor can be found in the emission control system. Oxygen is added for seamless ignition while starting the car. The main purpose of this oxygen sensor is to keep a check on the amount of oxygen in the car.

The oxygen sensor gets its data and communicates within the system with the help of an electrical signal or a voltage signal. A well-functioning oxygen sensor ensures that your engine works properly and performs well. The oxygen sensor sends the data to the central computer located in the engine, and the computer ensures that the mixture of oxygen and fuel is in optimal amounts to keep the engine running in top condition.

The oxygen sensor keeps the car's emissions in check and prevents the vehicle from emitting excessive emissions.

Types Of Oxygen Sensors

The oxygen sensors have been categorized into two types of exhausts. These are called binary exhaust gas and universal exhaust gas oxygen sensor.

Binary Exhaust Gas Oxygen Sensor

A binary exhaust gas oxygen sensor measures the optimum amount of oxygen by checking the difference in oxygen concentration. The difference in oxygen content between the exhaust gas and the ambient air should be enough to ensure that the mixture of oxygen in the engine is at an optimal level for the proper functioning of the car.

Universal Exhaust Gas Oxygen Sensor

The universal exhaust gas oxygen sensor is precise in measuring the difference in the oxygen level in the fuel and air. It picks up the lack and excess oxygen very quickly and has a wider range.

Symptoms Of a Faulty Oxygen Sensor

If the oxygen sensor is at fault and not working properly, you may notice that your engine is not working properly as the exhaust is failing. Whenever you see signs of a failing oxygen sensor, you should get it checked and, if needed, replace it immediately to ensure proper working of the engine.

Some signs you should look out for when examining an oxygen sensor include the following:

  • Poor performance of the engine and car with the vehicle stopping midway or rough idling
  • The car's engine light is off.
  • The code checker will recognize the failure of the oxygen sensor
  • The fuel mileage of the car may decrease
  • The emissions of the car exceed the normal amount

These symptoms usually show that there might be something wrong with your oxygen sensor and that you should check it out. However, you might not be able to guess from these signs whether or not you should change the sensor completely and get a new one, or just a repair of the component would do.

When Should You Change Your Oxygen Sensor?

If you experience any of the above-mentioned signs with your car, it may not necessarily mean that you have to change the oxygen sensor. However, there could also be other signs when your oxygen sensor is in trouble, which could mean that the damage is serious and needs to be looked into immediately.

If the check engine light on your car is on, it could mean a serious issue with your sensor, or it could also be something minor as a hinged gas cap. But the check-engine light always means you must look into the matter.

There could also be several more signs, such as the spark plug of the vehicle misfiring, rough idling, noticing that there is an increase in the consumption of fuel, lack of power in the vehicle, stalling, or other such signs. All these signs don't necessarily mean an issue with the oxygen sensor. It could be another underlying problem, but according to stats, you can save up to 40% by installing a new oxygen sensor as it significantly improves fuel consumption. So, high gas or fuel consumption could definitely point to a faulty oxygen sensor.

Replacing an old oxygen sensor could cost you mid to high hundred dollars. You can expect to pay $100 to $400 to replace a faulty oxygen sensor. However, this cost does not include the amount of hiring the labor or the service provider. If you choose to hire someone and not do it yourself, the replacement process can cost you a lot, depending on the car you drive and other factors.  

How To Prevent The Malfunctioning Of An Oxygen Sensor?

The oxygen sensor is one of the parts of a vehicle that does not need to be replaced as often or tended to again and again. However, just like other components, it is a mechanical part of the car, which will deteriorate over time. The degradation of mechanical components is a natural phenomenon. So, after a certain time, you might have to replace the oxygen sensor to ensure the engine and the car are working fine.

Despite all the degradation, there are certain things you can do and steps you can take to prevent the oxygen sensor from deteriorating fast. Make sure to go to a mechanic who can deal with the issues about the model and make of your car. You should also ensure that the service provider you go to has the necessary parts for the replacement process and that the products are high-quality. Also, take your car to the mechanic or check it yourself as soon as you notice any signs and symptoms of damage to the oxygen. Do not delay the treatment process.

When Should You Replace Your Oxygen Sensors?

The oxygen sensors in your car are not such an item that they need to be replaced regularly without any issue. Unlike the air filters or the oil in your car, you only have to replace the oxygen sensors when they malfunction.

The oxygen sensor is a very critical part of your vehicle. It is responsible for ensuring the air to fuel ratio is optimal in your vehicle and not unadjusted so that your engine and car keep running smoothly.

If the oxygen sensor fails and does not work properly, the vehicle won't be able to correctly tell the ratio of air and fuel, which can also lead to excessive emissions from the vehicle. This failure to work seamlessly can also damage other components of your car, such as the catalytic converter.

No car has a signal to inform you that the oxygen sensor is not working properly. You have to rely on other signs and symptoms. The check engine light is the main signal, and you can also feel the issues with the engine while starting the car. Overconsumption of fuel is a big red flag in this regard as well as bad sensors can lead to the vehicle eating up more fuel.


The oxygen sensor is an integral part of the vehicle. It is used to ensure that the oxygen level in the car is optimal and at the correct level for the engine to keep functioning properly. If the oxygen sensor fails, the oxygen level in the exhaust will not be maintained, and you may suffer issues like backfiring, stalling, and more problems with starting the engine and the car.

There are several symptoms to know when there is an issue with the oxygen sensor. Follow the symptoms, look after them, and get them checked immediately. You can also take some precautionary steps to ensure that your oxygen sensor keeps working fine for a long time.

Keep your cars maintained. Don't leave them too long without a checkup and examination. Also, follow the maintenance plan set out by the vehicle's company.

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