Virginia Auto Service

Understanding Coolant Temperature Sensor

Coolant Temperature Sensor

Car owners know that coolant is important to keep engines at optimal temperatures. A coolant temperature sensor helps us know when an engine is operating at the right temperature.

When you drive your vehicle the engine experiences continuous combustion which can make it very hot especially in warm weather.

The high temperature in the Valley can do some serious damage to your engine if you overlook the symptoms.

To keep your engine cool, different fluids and liquids are used to avoid overheating. Too much heat in your engine can cause failure or breakdown.

The water in your radiator is passed through pipes to keep temperatures from getting too high.

Engine oils are also designed to keep engine temperatures in the right range for peak performance.

A CTS or coolant temperature sensor is also known as an ECT or engine coolant temperature sensor is a device that measures the temperature of your coolant.

A faulty CTS can cause overheating and may impact your vehicle.

How Does an Engine Coolant Temperature Sensor Work

Most ECTs operate using electrical resistance to measure the temperature of the coolant.

The CTS is usually found near the engine thermostat. The coolant temperature sensor measures the temperature from the thermostat and of the coolant itself. The data is then sent to the ECU which then adjusts the engine functions accordingly.

These functions include the opening and closing of the cooling fan depending on the temperature reading. Onboard computers can also control exhaust gas recirculation and fuel combustion processes. This ensures that your engine is protected from overheating.

How hot your engine gets during operation plays a vital role in engine performance. Any issue with your CTS can give you headaches with your engine.

Why Engine Coolant Temperature is Important

Coolant temperature is an important thing to keep track of in your vehicle. Almost all cars sold in the U.S. have a temperature gauge installed to make sure you can see coolant temperatures as you drive.

The engine coolant temperature sensor can determine if the coolant is working properly in your car.

Advancement in technology allows tracking of coolant temperature and causes the ECU to respond when the temperature gets too high.

Most engines are designed to run between 160 to 200 degrees Fahrenheit. If engine temperatures are too cool you need a rich combustion mixture for your engine to operate smoothly. If it gets too hot, the coolant may start to boil and cause damage to the engine and its internal parts.

If you want your engine coolant temperature sensor to last a long time you need to give it proper maintenance by keeping your engine in good condition.

Many car owners make the mistake of filling their radiators with regular tap water. They don’t realize that tap water can cause corrosion and harm your engine in the long run. It is ideal to use a coolant that provides proper lubrication and prevents rust formation.

Coolant can also be lost through leaks in hoses or the radiator itself. Low coolant levels are the most common reason for engine overheating.

If you have a faulty CTS, you need to replace it at once. It will cost you around $100 to $220 which includes labor and parts.

When Do You Need A Coolant Temperature Sensor Replacement

It’s not unusual to see overheated vehicles on the side of the road in Phoenix AZ. If your coolant temperature sensor is showing symptoms of failure you should have it replaced immediately to avoid further damage to your engine.

One of the most common problems with the sensor is poor connections inside or in the wiring harness. This causes signal disruptions to the ECU. Symptoms of this issue show up as erratic readings in your temperature gauge. Your engine may run on fail-safe mode which means your air conditioner will stop working and you have your fans running non-stop.

Here are signs that you need to check your CTS.

Poor Mileage

If you notice frequent trips to the pump recently, you may have a problem with your coolant temperature sensor. A faulty CTS may send a wrong signal to your ECU resulting in an incorrect air-fuel mixture. 

If a signal is sent that the engine is cool but it is not, your onboard computer will instruct your car to use more fuel to heat up the engine to the right temperature. This causes poor fuel economy and lower engine performance. 


The cooling fan behind your radiator grill turns on to remove excess heat from your engine’s coolant. The fan operates when it receives an instruction from the onboard computer.

When your CTS sends a wrong signal, the fan might not turn on when needed causing your engine to overheat.

Engine overheating occurs when you are operating at a sustained temperature of over 240 degrees Fahrenheit.

An overheated engine can cause serious damage to pistons, valves, cylinders, and bearings. You should shut down your vehicle at the first signs of overheating.

Some models use a separate coolant temperature sensor for the fan but most cars use the same sensor.

If your engine has overheated, bring your car to the auto shop for reliable and high-quality auto repair services.

Black Smoke

If you have a faulty CTS, it may send the wrong signal to your ECU which results in a fuel mixture that is too rich. This is why you have black smoke coming out from your exhaust pipe.

Check Engine Light

Your check engine light will turn on if you have an issue with your coolant temperature sensor. If there is a circuit problem with your CTS, the system will detect it which means you need to bring your car in for inspection.

The check engine light will remain “on” until you fix the issue so you better head on to your auto repair shop at once.

Poor Idling

An ECT sensor that is not working properly will result in poor fuel mixture. You may notice that your engine vibrates or shakes at low speed which signifies poor idling.