What’s The Purpose Of A Coolant Temperature Sensor?

car overtheating collant temperature sensor

The purpose of a coolant temperature sensor is to help the engine computer regulate the engine cooling system.

The sensor measures the temperature of the coolant and sends a signal to the computer. The computer then uses this information to control the fan speed and activate the radiator cooling fans.

By regulating the engine cooling system, the computer can help keep the engine operating at its optimal temperature.

This, in turn, helps improve fuel economy and reduces emissions. So, while you may not give much thought to your coolant temperature sensor, it’s actually performing an important function.

What Happens When The Coolant Temperature Sensor Goes Out?

If the sensor goes out, the fan will not turn on, and the engine will overheat. This can lead to serious damage to the engine, as well as potentially dangerous situations if the vehicle is driven while overheating.

In some cases, a faulty coolant temperature sensor can also cause the engine to run too cold, which can result in decreased fuel efficiency and engine performance. For these reasons, it is important to have a working coolant temperature sensor in your vehicle.

How Many Coolant Temperature Sensors Are In A Car?

Most cars have only one coolant temperature sensor. However, some luxury vehicles and performance cars may have two or more sensors. The additional sensors may be located in the engine block or the cylinder head. The coolant temperature sensor is responsible for monitoring the temperature of the engine coolant.

The sensor is usually located near the thermostat housing. The sensor works by measuring the voltage output of the thermostat. When the engine is cold, the thermostat is closed and the voltage is low.

As the engine warms up, the thermostat opens and the voltage increases. The coolant temperature sensor uses this information to regulate the flow of coolant through the engine. By monitoring the coolant temperature, the sensor helps to ensure that the engine operates at peak efficiency.

How To Test A Coolant Temperature Sensor?

Here is a simple test you can do:

Remove the sensor from your car. For this test, you’re going to use a multimeter. 

Connect the multimeter to the sensor. There are 3 pins. You’re not going to use the one in the middle pin. You will only use the pins on the outside. 

Plug the red wire of the multimeter into one of the pins outside. Plug the black wire into the other pin on the outside.

Select DC on your multimeter. Your multimeter is going to indicate a reading at ambient temperature. It should be between 0 and 5V.

Now put the sensor into freezing water (water with ice cubes). The multimeter is going to read something close to 5V.

Then put the sensor into boiling water. It will read something close to 0V.

That’s how you know your temperature sensor is working. If when changing temperature, the value on the multimeter is not changing. It simply means that your sensor is bad and needs to be replaced.

How Much Does It Cost To Replace A Coolant Temperature Sensor?

The cost of replacing a coolant temperature sensor will vary depending on the make and model of your vehicle. In most cases, you can expect to pay between $50 and $100 for the sensor itself. Labor costs will vary depending on the shop you take your vehicle to, but you can typically expect to pay between $50 and $100 for labor as well. In total, then, the cost of replacing a coolant temperature sensor will usually fall somewhere between $100 and $200. Of course, it’s always best to check with your mechanic or dealer beforehand to get a more accurate estimate of the cost of this repair.

Can A Coolant Temperature Sensor Cause Start Problems?

If the CTS fails, it can cause a variety of start problems. For example, if the engine coolant is too cold, the CTS will signal the engine computer to delay fuel injection. This can cause a hard start or no start condition. In addition, a failed CTS can also cause the engine to run too hot or too cold. As a result, it is important to have a functioning CTS in order to maintain optimal engine performance.

Can A Bad Coolant Temperature Sensor Cause A Misfire?

The CTS monitors the temperature of the coolant and relays this information to the engine control unit (ECU). The ECU uses this data to adjust the fuel mixture, ignition timing, and other engine parameters. If the CTS is not working properly, it can cause a misfire. A misfire is when one or more of the cylinders in the engine does not fire correctly. This can cause a loss of power and decreased fuel efficiency. In extreme cases, it can also damage the catalytic converter. While a faulty CTS could be the cause of a misfire, there are other potential causes as well. Therefore, it is important to have your vehicle diagnosed by a qualified technician to determine the root cause of the problem.

Does The Coolant Temperature Sensor Affect The Transmission?

The coolant temperature sensor sends a signal to the computer, which then adjusts the transmission shift points based on the temperature of the engine coolant.

In other words, if the engine is cold, the transmission will shift sooner to prevent damage to the engine. The opposite is also true – if the engine is hot, the transmission will shift later to prevent damage to the transmission.

As a result, the coolant temperature sensor does have an effect on the transmission. However, it is important to note that other factors, such as vehicle speed and load, also play a role in determining when the transmission shifts.


A coolant temperature sensor is an important part of a vehicle’s cooling system. It helps to regulate the engine temperature, which can improve fuel economy and reduce emissions. If the sensor goes out, it can cause the engine to overheat or run too cold. For these reasons, it is important to have a working coolant temperature sensor in your vehicle.

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