How to Tell If Your Coolant Temp Sensor Is Bad

How to Tell If Your Coolant Temp Sensor Is Bad?

The CTS is an essential sensor of your vehicle. Without it, the coolant level will not be balanced, neither will you be able to properly monitor the flow and temperature of the antifreeze.

However, one of our vehicles was behaving abnormally. The engine was not adjusting the air-fuel mixture properly, which ended up in poor overall performance. So, we wondered if the sensor had failed or not.

After that, we looked up how to tell if your coolant temp sensor is bad or not. But we could not really get that much info out of the internet. Eventually, we had to visit a professional mechanic in the end. And through this article, we aim to ensure that you do not have to go through the same hassle as us.

What Does Coolant Temp Sensor Do?

Before we describe the telltale signs that give away that the sensor has gone bad, we would like to ensure you know all about what it does. As we have mentioned above, it monitors the overall temperature of the coolant circulating through the engine. As a result, you will get an idea of how hot the engine is getting.

When the engine overheats or the coolant is not properly regulating the temperature, it will pick up the information and show it on the dashboard. There is a light that connects directly to the sensor. And that light will glow up when it picks up overheating information.

Some of the modern vehicles will automatically shut off the engine by relying on the information picked up by the coolant temp sensor. They do that when the engine has reached a specific temperature, at which there can be excessive damage to the engine.

That being said, when the temp sensor is not doing a proper job, the engine will not be able to communicate with it properly, which will end up with the engine overheating and getting damaged. The overall performance can even degrade if the temp is not monitoring the air-fuel mixture properly.

Signs of a Bad Coolant Temperature Sensor

Now that you have a fair idea regarding what a temp sensor does and its importance in optimizing the engine’s overall operation let us get back to the topic you are mainly here for. So, these are the telltale signs that state that the coolant temp sensor has gone bad:

Check Engine Light

One of the most common signs of a bad coolant temp sensor is the check engine light will show up randomly on your dashboard. This indicator basically states that there is something wrong with the engine or the coolant. And it makes you aware that the car needs an inspection.

Poor Mileage

A faulty CTS can send false information to the onboard computer, which will result in an improper amount of air-fuel mixture. For example, it can send a signal that will indicate that the engine is cold when it is not. That will make the engine use more fuel to heat things up, which will degrade the overall performance.

Electrical Fans Not Turning on

When the CTS has gone bad, the electrical cooling fans might not turn on. The sensor will not send the signal to the onboard computer that the fans need to turn on. However, not all of the vehicles will have a direct connection of the fans with the coolant temperature sensor. Some of them might rely on other temp sensors.

Black Smoke From the Exhaust

If the sensor is not picking up the temperature properly, the ECU might enrich the fuel mixture to a point where the whole combustion process will become difficult for the engine. And when an excessive amount of fuel burns inside, the exhaust will output thick black smoke.

Difficulty in terms of Starting

When you start the engine, a proper amount of fuel needs to be injected inside the engine. And the CTS plays a vital role in this case. It will be difficult to start the engine if the sensor does not signal the other components to mix air and fuel properly. Also, engine knocking and cold start issues will be prevalent too.

Engine Overheats

The cooling fans that are behind the radiator grille usually remove most of the heat from the coolant. And as you know, if the CTS sensor is not working properly, it will not turn the fans on. As a result, the coolant will not adequately be cooled. Also, that would mean that the engine will overheat during extreme loads.

In some cases, when the CTS is not working at all, you might notice some smoke coming out of the engine. And even when the smoke is coming out, the fans will turn on. Yes, that is how bad things can get when the coolant temp sensor is not working adequately.

Poor Idling

If the sensor is faulty, the fuel mixture will not be capable of adjusting properly. That will cause the engine to shake or vibrate when the vehicle is at a low speed. These strange shaking can lead to power loss, and at a point, the engine might exhibit some other strange behaviors as well.

Poor Engine Performance

Last but not least, you will notice a significant drop in terms of performance. When the engine is not getting cooled due to the faulty sensor, the onboard computer will lower the power draw and make the engine output less amount of performance to compensate for the heat.

Furthermore, you might even notice that it is getting a bit hard for you to maintain a high speed when the CTS has gone bad. And it will throttle a lot during the higher loads.

Final Words

As you can see, a faulty CTS can lead to loads of severe problems. And now that you know how to tell if your coolant temp sensor is bad or not opt for an immediate checkup whenever you notice any of the signs.

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