The cooling system in an internal combustion engine vehicle keeps the engine running at its ideal temperature and guards against overheating. The temperature of the liquid coolant is measured by an ECT, or engine coolant temperature sensor. A popular engine cooling temperature sensor is an NTC (Negative Temperature Coefficient) thermistor, meaning that as the temperature rises, it becomes less resistive electrically.coolant temperature sensor

The ECT sensor’s tip extends into a passageway of the cooling system and is submerged in coolant. Many automobiles feature multiple coolant temperature sensors. The primary ECT sensor (ECT sensor 1) is typically mounted on the thermostat housing, cylinder head, or block, which is close to the thermostat.

Well, in today’s car guide, we’ll be educating you on a car coolant temperature sensor. With that being said, the answers to the following question will be discussed:

So, let’s get down to it!


What is a coolant temperature sensor?

A coolant temperature sensor, also known as an engine coolant temperature sensor (ECT sensor), is a device used in vehicles to monitor the temperature of the engine coolant. in other words, the engine coolant temperature is measured by a resistor circuit through the coolant temperature sensor. This reading is then transmitted to the Engine Control Module (ECM) or Engine Control Unit (ECU), which serves as the vehicle’s “brain.”

It is usually seen on the cylinder head, engine block, or intake manifold. The engine control unit (ECU) or engine management system receives the information from the coolant temperature sensor, which detects the coolant’s temperature. Important choices about fuel injection, ignition timing, and other engine functions are made by the ECU using this information.


In order to keep the engine working at its ideal temperature, the coolant temperature sensor is essential. It aids in preventing the engine from overheating or operating too coldly, both of which can have an impact on output, fuel economy, and pollutants. The sensor helps in regulating the air-fuel mixture and chooses the right moment for ignition by keeping track of the coolant temperature.

The engine performance may be affected in a number of ways if the coolant temperature sensor is defective or malfunctioning. For instance, incorrect temperature measurements may result in faulty fuel delivery, which could reduce fuel efficiency or make it harder to start the engine. A malfunctioning sensor may also cause the engine to overheat or turn on the check engine light.


diagram of coolant temperature sensor

How does it work?

The coolant temperature sensor works similarly to an engine thermometer in your car. It measures the temperature of the engine coolant. It makes use of a unique component known as a thermistor, whose electrical resistance varies depending on the temperature. The engine control unit (ECU), which functions as the car’s “brain,” is connected to the sensor.

The coolant temperature is represented by an electrical signal that the thermistor gives to the ECU. This temperature data is used by the ECU to make critical choices regarding the engine’s operation. For instance, to maintain the engine operating properly, it modifies the fuel mixture and ignition timing dependent on the coolant temperature.

Problems may arise if the coolant temperature sensor is not functioning properly. It’s possible that the ECU is unaware of the actual temperature, which might cause problems like poor fuel economy or engine overheating. In general, the coolant temperature sensor aids the computer of the vehicle in maintaining the engine at the proper temperature for maximum effectiveness and efficiency.

Where is the coolant temperature sensor located?

coolant temperature sensor location

Depending on the make and model of the car, the location of the coolant temperature sensor may change. However, in most vehicles, the coolant temperature sensor is typically located near the engine’s thermostat housing or on the engine block itself. Usually, it’s located next to the radiator hose or in a coolant passage. To get a specific answer for your vehicle, it is recommended to consult the owner’s manual or a repair manual for your car. These resources often provide detailed information and diagrams to help locate the coolant temperature sensor accurately.

What are the symptoms of a bad coolant temperature sensor?

The following are common symptoms you’ll start to notice when your coolant temperature sensor is going bad:

Engine Overheats

An inaccurate “cold” signal may be sent to the ECU by a broken coolant temperature sensor, fooling it into thinking the engine isn’t hot enough. The engine will then continue to heat up and eventually overheat as a result of the ECU making adjustments to the fuel injection, ignition timing, and variable valve timing.

Trouble Starting Your Car

The ECU determines the necessary fuel-air mixture ratio when you cold-start your automobile by taking into account the coolant and outside temperatures. Lean fuel-air mixtures can make cold starts challenging and are sometimes caused by faulty coolant temperature sensors.

Exhaust Removes Black Smoke

The coolant temperature sensor in your automobile works with the ECU to select the right fuel-to-air ratio for combustion. A malfunctioning sensor might cause a rich fuel-air mixture, which would result in black smoke coming out of the exhaust pipe and poor fuel efficiency.

Check Engine Light is on

The ECU may turn on the Check Engine Light on your car’s dashboard as a result of a defective sensor. Additionally, it will record an error code that an OBD-2 scan tool may interpret.

Car Idles Roughly

The Engine Control Unit may deliver varying amounts of fuel into the engine as a result of a broken ECT sensor, causing the engine to idle unevenly.

Temperature Gauge Fluctuates

The coolant temperature sensor provides data to the engine temperature gauge on your car’s dashboard. It may fluctuate erratically while you’re driving if a sensor is broken.

Transmission Shifting Faults

The coolant temperature sensor reading is used by the Transmission Control Module (TCM) to prevent the automobile from going into overdrive while the engine is cold. Reduced engine performance and transmission issues can result from the sensor’s inaccurate data.

Problems With the Radiator Fan

Due to a malfunctioning coolant sensor, the Engine Control Unit of your car may activate the radiator fan even when the engine isn’t hot enough. The converse of this is also possible, which could cause the engine to overheat past its operating temperature and sustain damage.

How much does a coolant temperature sensor cost?

Depending on the car model and labor expenses, the cost to repair a coolant temperature sensor ranges from $50 to $250. In addition to the labor expense, a coolant temperature sensor can be purchased for $30 to $100. The coolant temperature sensor is often relatively affordable; a good one can be purchased for roughly $40. There are less expensive models available, but to avoid headaches, I strongly advise purchasing a high-quality model like Bosch.

Except that you might need to drain the entire engine’s coolant and refill it, the replacement is frequently relatively simple. Unfortunately, taking out the coolant also necessitates taking out all of the air in the coolant system, which can be challenging. However, if you replace the sensor quickly, you may avoid having to tap out the coolant, though doing so requires some ability.

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What happens when the coolant temperature sensor goes bad?

When a coolant temperature sensor goes bad, it can lead to symptoms such as inaccurate temperature readings, engine overheating, difficulty starting the engine, poor fuel efficiency, and problems with the cooling fan operation.

How do you know a coolant temp sensor is bad?

Signs of a bad coolant temperature sensor include inaccurate temperature readings, fluctuating temperature readings, engine overheating, poor fuel efficiency, difficulty starting the engine, and abnormal cooling fan operation.

What does a coolant temperature sensor do?

A coolant temperature sensor monitors the temperature of the engine coolant. It sends this information to the engine control unit (ECU) to make adjustments to fuel injection, ignition timing, and cooling system operation for optimal engine performance and to prevent overheating.

Do coolant temperature sensors prevent the engine from overheating?

Coolant temperature sensors contribute to preventing engine overheating. They provide temperature information to the ECU, which controls the cooling system to maintain the engine within the desired temperature range.

What causes a temperature sensor to fail?

Temperature sensor failure can be caused by electrical or wiring issues, exposure to extreme temperatures, contamination or build-up, corrosion or damage to the sensor, aging, or manufacturer defects.

Can a car run without a coolant sensor?

A car can technically run without a coolant sensor, but it is not advisable. Operating without a functioning coolant sensor can lead to engine damage, reduced fuel efficiency, and increased emissions.

Does the coolant temp sensor control the fan?

The coolant temperature sensor provides temperature information to the ECU, which controls the operation of the cooling fan based on the readings received.

Are there 2 coolant temperature sensors?

Some vehicles may have multiple coolant temperature sensors. The number of sensors can vary depending on the vehicle’s make, model, and engine configuration.

What can affect a temperature sensor?

Factors that can affect a temperature sensor include contamination, wiring or electrical issues, corrosion, vibration or physical damage, exposure to extreme temperatures, and aging or wear.

Is a temperature sensor and coolant sensor the same?

Yes, a temperature sensor and a coolant sensor are often used interchangeably. The coolant temperature sensor measures the temperature of the engine coolant to provide temperature data for the engine control system.

Well, that concludes this article, in which we talked about the coolant temperature sensor in a car. Nonetheless, the answers to the following questions were covered:

Hope you learn a lot from reading this post. If you do, kindly share it with others who will also benefit from it. Thanks for reading; see you around!