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Engine Coolant Temperature Sensor: What Is It and What Can Go Wrong?

Engine Coolant Temperature Sensor: What Is It and What Can Go Wrong?

The engine coolant temperature sensor monitors the coolant temperature and informs the vehicle's computer about when to perform important functions like fuel mixing, fuel injection timing, etc.

Your vehicle's engine needs to operate within a certain range of temperature. It is important that your engine does not exceed the maximum threshold and get into situations with engine overheating that could damage the entire engine. It is also important that your engine reaches the minimum threshold to operate properly and generate the required energy.

Auto Repairs Are EXPENSIVE

The engine coolant temperature sensor is the main component in your car responsible for communicating with your vehicle's computer and sending information about the current engine temperature. In addition, this sensor plays a major role in many other functions, including fuel mixing, fuel injection, injection timing, etc.

This article walks you through the main purpose of the engine coolant temperature sensor, and it also highlights these symptoms of a bad coolant temperature sensor. Therefore, you can know when this sensor needs to be replaced and prevent dealing with undesirable situations that could cost you thousands of dollars to get fixed.

What is the engine coolant temperature sensor, and what does it do?

The engine coolant temperature sensor is a minor component of your vehicle's cooling system. However, it plays a major role in maintaining a perfectly running cooling system and preventing engine overheating that could cause significant damage.

This sensor is sometimes referred to as the CTS, or your mechanic might call it the ECT and sometimes the ECT S. Whatever the term, it refers to the same sensor that is responsible for measuring the coolant temperature and sending a signal to your vehicle's computer to determine and function other processes.

Depending on the coolant temperature, your vehicle knows how hot the engine is and when to start important functions like the ignition timing, fuel mix, fuel injection, etc. In some scenarios, depending on the temperature of the coolant, your vehicle decides on turning on the electric fan, which withdraws air from the radiator to help cool down the engine faster.

Where is the engine coolant temperature sensor located?

The engine coolant temperature sensor typically is located somewhere close to the thermostat, if not inside it. If you want accurate guidance about where to locate the engine coolant temperature sensor, you can always refer to your vehicle's owner’s manual to discuss with your mechanic.

What are the main symptoms of a bad engine coolant temperature sensor?

With this critical role of the engine coolant temperature sensor, it can be extremely hard for your vehicle to operate properly with a bad coolant temperature sensor. Therefore, one of the first things that you need to familiarize yourself with as a driver is the main symptoms of a bad engine cooling temperature sensor.

By learning about these symptoms, you can detect the problem early and help resolve it without needing to spend a lot of money. Most vehicles problems can be resolved cheaper if you detect them early, and if you leave them, they could lead to significant damages that could cost you thousands of dollars down the road if not the entire vehicle.

Here are some of the common symptoms of a bad engine coolant temperature sensor:

1.    Significant reduction in the fuel economy

One of the first and most common symptoms of a bad engine coolant temperature sensor is significantly reducing your vehicle's fuel economy. Since this sensor is responsible for sending enough information to your car's computer to determine the fuel injection timing, your vehicle's computer might think that your engine is continuously cold and keeps sending additional fuel to get it hotter.

The more fuel your vehicle sends to the engine, the richer the air-fuel mixture and the more fuel your car consumes to produce minimum power. Therefore, if you notice that you need to visit the gas station more frequently than often, it might be a problem with the engine coolant temperature sensor.

2.    Weird black smoke coming from the engine

Typically, your vehicle should not produce clear clouds of smoke out of the exhaust pipe. However, when the coolant temperature sensor goes bad, it is very common to see clouds of black smoke coming out of the exhaust tailpipe.

What happens, in this case, is that your vehicle's engine is burning more fuel the needed. As a result, at the end of the combustion

Remember that black smoke coming out of the tailpipe should not necessarily indicate a bad engine coolant temperature sensor because it might be linked to another component that is not working properly. Therefore, it is your mechanic's job to confirm the real culprit and determine what needs to be replaced.

3.    Engine overheating

Unsurprisingly, when the coolant temperature sensor does not work properly, your vehicle's computer won't get an idea about how hot the engine is. Therefore, the engine might keep getting hotter and hotter without any help from the cooling system to cool down.

Engine overheating is one of the worst problems that your engine might face, which could cost you thousands of dollars to be repaired. In addition, some engine overheating problems might cause significant damage to the engine and require a new engine to be resolved.

4.    Check engine warning light

Your vehicles check engine lights is a very important element that you need to keep an eye for. When the check engine lights illuminate, your vehicle is trying to communicate with you and bring your attention to things that are not going well inside the vehicle. Therefore, it is important that whenever you see the check engine light triggered, you take the issue seriously and reach out to your mechanic and have him inspect the problem before things get more complicated.

5.    Problem functioning the electric cooling fan

Depending on your vehicle type, your car might have an electric cooling fan responsible for withdrawing air to help cool the engine faster. When the coolant temperature sensor does not work properly, it impacts the functionality of the electric cooling fan. In some scenarios, you might notice that this fan did not trigger at the right time as the engine temperatures exceeded the maximum threshold.

6.    Issues with starting the vehicle

The engine coolant temperature sensor is also responsible for the ignition timing and the air-fuel mixture. Therefore, in some scenarios with a bad sensor, you might deal with difficulty starting your vehicle.

Difficulty starting is a broad topic related to a long list of faulty components like the battery, alternator, starter motor, etc. Therefore, have a conversation with your mechanic and let him perform a thorough inspection to confirm what's going on wrong and detect whether it's about the temperature coolant sensor or not.

7.    Issues with idling

With a bad air-fuel mixture, your vehicle might have trouble during idling time, and you'll notice that the car is either shaking or vibrating, especially if you're driving at a very low speed. In some scenarios, any coolant temperature sensor might result in complete power loss, which is a significant situation that might lead to some safety issues.

8.    Reduction in your engine's performance

With a bad air-fuel mixture, your engine will consume more fuel than it needs, and therefore, it won't produce the required amount of power for fuel consumed. Therefore, you'll notice that the engine does not perform as it should, and its power drops significantly.

How much does it cost to replace a bad engine coolant temperature sensor?

Engine coolant temperature sensor replacement costs range from $150 and $193 depending on your vehicle's type and location where you get the job done. Parts should not cost you more than $88, while labor is the biggest component that might cost you up to 105 dollars.

You must be mindful about where to get the coolant temperature sensor replacement job done. Since it deals with one of the core components, the engine, you must have an experienced mechanic do the job rather than you experiencing with your vehicle and causing significant damage is.

Going to an independent shop will be much cheaper, but you want to confirm that they have the right level of skill sets. However, if you have an expensive vehicle, it might be worth investing and having a mechanic at the dealership to get the job done to prevent dealing with problems that mistakes could introduce.

Can I replace my coolant temperature sensor?

Yes! According to automotive experts, engine coolant temperature sensor replacement is not a complicated job and does not require advanced mechanical skill sets. Therefore, it would be great that you learned how to replace the sensor by yourself.

Obviously, you must go through all available tutorials and YouTube videos to help do the job right, so you don't introduce damages to the sensor or the engine. However, unless you're 100% comfortable that you can do the job, it's better that you leave it to professionals.

What important pro tip here is that you never want to change the engine coolant temperature sensor when the engine is hot. You must allow your engine to cool down for at least one hour so you don't deal with risk situations that might impact your life.

How long does a coolant temperature sensor last?

Typically, the engine coolant temperature sensor should last up to 100,000 miles. After that, you need to perform all necessary maintenance to prevent damaging the sensor prematurely. Of course, this threshold does not mean that every vehicle will not suffer from coolant temperature sensors before the 100,000 miles threshold, but it can happen with good care of your car.

Do you need to drain the coolant before replacing the coolant temperature sensor?

Yes. To get to the coolant sensor, you need to drain out at least two to three quarts of coolant because the sensor is located below the maximum coolant level. However, once you drain the proper amount of coolant and see the sensor, you can go ahead and replace it without needing to drain more coolant.

Remember that after installing the new coolant temperature sensor, you need to top off the coolant back and ensure that your vehicle does not run at a local. This can introduce significant problems, especially with engine overheating.


The engine coolant temperature sensor is a significant component in your vehicle responsible for communicating with your vehicle's computer and sending information about the current engine temperature. This way, the computer decides when to send fuel and how often the combustion process should go.

You must keep an eye on the coolant temperature sensor and monitor for any symptoms of a bad sensor, informing you when to install a new sensor to prevent dealing with major issues that could cost you a lot of money to get fixed.

If your car got significant damages in the engine or the transmission, it might not be worth your money investing in installing a new coolant temperature sensor because the problems are beyond repair. In that case, you might want to think about the perfect timing for selling your vehicle and using its value as a down payment towards a better car that doesn't have any major problems.

The good news is that Cash Cars Buyer is willing to remove your vehicle within one to three days only! Cash Cars Buyer is one of the top-rated car removal companies in the nation that guarantees to pay you the top dollars and provide you with free towing despite your living location around the United States.

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