Engine coolant Temperature Sensor — What is an engine coolant temperature sensor? (Best solution)

A coolant temperature sensor (CTS) (also known as an ECT sensor or ECTS (engine coolant temperature sensor) is used to measure the temperature of the coolant/antifreeze mix in the cooling system, giving an indication of how much heat the engine is giving off.

  • The engine coolant temperature sensor is temperature-variable resistor, which usually has a negative temperature coefficient. It is a two-wire thermistor immersed in coolant and measures its temperature. The onboard computer uses the signal of ECT as the main correction factor when calculating the ignition advance and the injection duration.

What happens when the coolant temperature sensor goes bad?

Poor Mileage A faulty ECT sensor can send a false signal to the onboard computer, resulting in an incorrect air-fuel mixture. For example, a faulty sensor can send a signal indicating the engine is cold when it is not, and more fuel will heat the engine quickly.

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

The average price for an engine temperature sensor replacement is between $150 and $193. Labor costs are between $82 and $105 while parts are between $66 and $88.

Can you drive with a bad coolant temp sensor?

It is possible to drive a vehicle with a faulty coolant temperature sensor as the management system defaults to a static reading. A vehicle’s coolant sensor is a critical component used by the engine management system. It directly affects, cooling and fueling of the engine and therefore affects how the engine performs.

Can a temp sensor affect engine starting?

The sensor will not cause a no start. It could cause a hard start and a rich or lean condition only.

Is used for testing of engine coolant temperature sensor?

Testing the coolant temperature sensor is a very quick process. With the use of a digital volt-ohm meter you can easily tell if the sensor is faulty or not.

Where is coolant temperature sensor?

The Engine Coolant Temperature Sensor can be located in a few places, depending on the vehicle and its manufacturer. It is most often located close to the thermostat of the cooling system or inside of it. The cooling system is located beneath the air intake pipe and behind the right cylinder.

Why is my engine coolant temperature light on?

When the coolant temperature warning light goes on, the engine is seriously overheated, which can be caused by overheating, lack of cooling water or a cooling system that is having trouble. At this point, you need to park your car in a safe area with shade (if it’s summer) to open the bonnet.

How long does it take to replace a coolant temperature sensor?

The actual process of replacing the coolant temperature sensor is extremely simple. However, the difficult work comes in the preparation of the cooling system – both before and after. Tip: This job should only be completed when the engine is cold and has not been running for a minimum of one hour.

How long does it take to replace temperature sensor?

Remember that most mechanics will charge around $80 to $110 per hour for their services. The thermostat replacement job should take a mechanic about 1 to 2 hours to complete it. Therefore, you end up paying more money for the labor than you do for the actual thermostat part.

Engine coolant temperature sensor: how it works, symptoms, problems, testing

P0308 is a serious problem that, if left unattended, might leave you stranded or render your car nearly undriveable. If you can identify the problem that is causing the code to be generated, you may save both time and money by preventing your Ford F150 from breaking down. Your catalytic converter may also be saved if you take action quickly. Good luck in figuring out what’s wrong with your computer! If you have anything to contribute, please leave a remark in the section below this paragraph.

ECT/CHT sensor problems

One of the most typical issues is when the sensor has a bad connection either inside the sensor itself, or inside the connector or the wire harness. This results in interruptions in the signal to the PCM, and the PCM sets the fault as a result of this disruption. When this problem occurs in a vehicle, the temperature gauge may display irregular readings, which might be indicative of the problem. It is possible that the engine will operate in fail-safe mode, causing the air conditioner to cease operating and the radiator fans to run continuously.

The problem with the wire harness rubbing on the front right side of the transmission is described in detail in the General Motors service bulletin PI0631F for the 2012-2013 Chevrolet Impala.

It is necessary to fix the harness in order to resolve the issue.

For example, the Ford service bulletin TSB 11-10-5 describes a problem that affects the 2.5L engines in the 2010-2012 Fusion, Escape, Transit Connect, as well as Mercury and Lincoln branded vehicles: water contamination in the sensor connector can result in the codes P1285, P1299, and/or P0128 being displayed on the instrument panel.

This problem is described in detail in the advisory SI M17 06 12, which applies to some R55, R56, R57, and R58 MINI Cooper/CoooperS cars.

A new sensor and a few other associated parts must be installed in order for this repair to be completed.

It is necessary to do a thorough investigation of the matter. Of course, given the fact that the ECT sensor is a very inexpensive component, it is frequently advised that it be replaced if it is suspected of malfunctioning.

Ways to test the engine coolant temperature sensor

Because the sensor’s tip must be submerged in coolant to function properly, a low coolant level or air pockets inside the cooling system might result in an inaccurate signal from the sensor. When dealing with cooling system issues, the first thing that needs to be done is to check the fluid level. A visual inspection of the ECT sensor connection is required to look for broken pins or corrosion. There are numerous methods for testing the ECT sensor, and the service handbook will outline the proper method to use.

  1. The resistance of the Engine coolant temperature (ECT) sensor is being measured at this time.
  2. Resistance measurements can only be made on a sensor if the sensor is isolated from the circuit being measured.
  3. When the engine was completely cool, the resistance measured 2,953 Ohm.
  4. This sensor meets or exceeds requirements.
  5. Checking the ECT/CHT sensor’s performance Voltage: An other approach to test the sensor is to measure the voltage across the sensor terminals while the engine is running at full throttle.
  6. The sensor is wired into the engine’s computer system (PCM).
  7. It is necessary to check both the reference voltage and the ground before proceeding.

We’ve backprobed the ECT sensor in this shot to ensure that it remains attached to the circuit.

When the engine was fully warmed up, the voltage decreased to 0.988 Volt.

It is safe to assume that the circuit is either open or shorted to ground if there is no voltage present.

Compare the readings from the ECT or CHT sensor to those from other temperature sensors: The intake air temperature (IAT) sensor is an example of a sensor that measures temperature in addition to the ambient temperature sensor.

It is recommended that if the car has been left parked overnight, the engine temperature (ECT or CHT) and the temperature of the IAT sensor located in the intake be very close to one another.

Using the photo, you can see that the IAT sensor measures 32°F inside the intake, whereas the ECT sensor measures 30.2°F inside the intake.

If the difference is significantly greater, it is likely that one of the temperature sensors is measuring the temperature incorrectly, as in this case.

A fault in the ECT circuit that occurs intermittently.

A change in voltage indicates the problem area.

To demonstrate, we monitored the coolant temperature with the Torque app, see the photo.

As you can see the temperature momentarily drops and then comes back up.

Why does the ECT sensor show -40°F (-40°C)?: When the ECT sensor is disconnected, the scan tool will show -40 degrees (-40° Fahrenheit equals-40° Celsius).

When the PCM sets the trouble code, it also stores the freeze frame which is a snapshot of major parameters at the time of the fault.

If the freeze frame shows the ECT at -40 degrees, it means that the ECT sensor circuit was open at the time of the fault. It could be a problem with the sensor itself, connector or the wiring harness.

Engine temperaturesensor replacement

In most autos, changing the ECT or CHT sensor is a straightforward process. In many automobiles, the sensor is kept in place by a clip. It is possible that a special deep socket will be required in some vehicles. If you take your automobile to a repair shop, replacing the engine temperature sensor will cost you between $59 and $129 (labor). The sensor (component) is not very expensive; nonetheless, it is recommended that you choose an OEM part. Following the replacement of the ECT sensor, the cooling system must be replenished and drained of any trapped air pockets.

  • If you opt to replace the ECT sensor as a do-it-yourself repair, be sure to read the service manual for detailed instructions and safety considerations.
  • In this article, we provided numerous links to websites where you may subscribe to a service manual in exchange for a little charge.
  • No, that isn’t essential at all.
  • It is customary in this situation to replace both at the same time.

How Does an Engine Coolant Temperature Sensor Work? – Meineke

Published on Thursday, January 26th, 2017. During a typical drive, how hot does the engine of your car get? You might not be aware of it, but your vehicle’s coolant temperature sensor most likely is. The sensor monitors the vehicle’s operating temperature and notifies the vehicle’s on-board computer when there is a possible issue. But, exactly, how does this automotive temperature sensor function, and what is its intended use?

How the Temperature Sensor Works

The coolant temperature sensor (CTS) is usually located close to the engine thermostat, which allows it to operate at peak performance in most automobiles. The CTS’s tip is most likely situated very adjacent to the engine’s coolant supply line. The sensor operates by sensing the temperature that is being emitted by the thermostat and/or the coolant itself, and then storing that information. The temperature reading is subsequently delivered to the on-board control system for further processing.

As soon as the control system receives the temperature reading from the CTS, it may decide whether or not to switch on or turn off the cooling fan.

When the Car Temperature Sensor Goes Bad

Similarly to any other component in your vehicle, the sensor might become faulty over time and become out of commission. This can result in a variety of issues, including the engine being overheated. It is possible to visually check the engine sensor if you know where it is located and what it looks like. This will allow you to determine whether or not it has developed any cracks or fissures. While this visual check might be beneficial, it will not assist you in diagnosing every conceivable problem because certain sensor faults can manifest themselves without the presence of visual proof.

Generally speaking, if your sensor is not functioning properly, it will transmit a signal to the computer, resulting in the illumination of your Check Engine light. If you notice the Check Engine light illuminate, take your vehicle to a skilled mechanic as soon as possible.

Replacing the Car Temperature Sensor

After a period of time, the sensor will need to be completely replaced. If the engine has been subjected to any type of stress or damage, sensor replacement is always suggested since you don’t want to take the chance of driving the car with a defective sensor. Even regular wear and tear can cause the sensor to deteriorate over time, as can abrasion and corrosion. You may always get your CTS replaced by a specialist in the automotive industry. You will undoubtedly save time and money in the long run if you pay attention to this component of preventative maintenance.

Engine Coolant Temperature Sensor (ECT)

A general explanation of the engine coolant temperature sensor (ECT) is as follows: The engine coolant temperature sensor is a temperature-variable resistor with a negative temperature coefficient, which is typical for this type of sensor. It consists of a two-wire thermistor that is immersed in coolant and monitors the temperature of the coolant When calculating the ignition advance and injection length, the onboard computer makes use of the signal from the ECT as the primary correction factor, according to the manufacturer.


1: A diagram of the human body The ECT sensor’s operation is based on the following principle: The ECT sensor is linked in a circuit that is normally supplied with a reference voltage of +5V in order to convert the ECT resistance variation to voltage variation, which may then be further processed by the ECU, in order to convert the ECT resistance variation to voltage variation.

After the engine is started, the temperature of the coolant begins to rise.

When heated to 90 degrees Celsius, its resistance is in the region of 200 to 300 ohms.

ECT sensors are available in a variety of designs.

  • In the presence of a negative temperature coefficient. These are the most often seen sensors in automobiles. Their resistance lowers as the temperature rises
  • When the temperature coefficient is positive, their resistance falls. Some older systems, such as Renix, make use of this term. Here, when the temperature rises, the voltage and resistance both rise in proportion to it.

Procedure for testing the functionality of the ECT sensor: Use a sensor with a negative temperature coefficient and a voltmeter.

  • Disconnect the connection of the cooling system temperature sensor from the power supply by removing the protective rubber cap. Connect the negative wire of the voltmeter to the chassis ground to complete the connection. Determine which terminals are used for the signal and which are used for ground. Connection of the positive wire of the voltmeter to the ECT signal terminal is required. Starting the engine from a cold condition is recommended. The voltage measurements should be in the range of 2V to 3V, depending on the temperature being measured. Table-1 depicts the link between voltage and temperature
  • It also includes the relationship between voltage and pressure. Ascertain if the ECT voltage signal is in accordance with the current temperature. In order to complete this task, you will require a thermometer. Start the engine and allow it to warm up to operating temperature before continuing. It is recommended that the voltage decreases during engine warmup in accordance with the values shown in Table-1. A common problem is that the output resistance (and voltage) varies in an improper manner outside of their typical operating range. When the engine is cold, the usual value of the ECT sensor voltage is 2V, and when the engine is heated, the normal value is 0.5V. It is possible that an incorrectly functioning sensor would display a voltage of 1.5V when the engine is cold and 1.25V when the engine is warm, resulting in difficulty starting a cold engine and the existence of a rich fuel mixture when the engine is warm. This will not result in any error codes being generated (if the onboard controller is not set to detect voltage changes), since the sensor will continue to function within its design specifications throughout this period. ECT sensors must be changed if they are discovered to have a fault. The ECT voltage signal should be 0V (indicating a lack of power supply or a short circuit to the ground), or 5.0V if there is an open circuit
  • Otherwise, the ECT voltage signal should be 0V.
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Temperature, ºС Resistance, Ω Voltage, V
4800 – 6600 4.00 – 4.50
10 4000 3.75 – 4.00
20 2200 – 2800 3.00 – 3.50
30 1300 3.25
40 1000 – 1200 2.50 – 3.00
50 1000 2.50
60 800 2.00 – 2.50
80 270 – 380 1.00 – 1.30
110 0.50
Broken circuit 5.0 ± 0.1
short circuit to the ground

IMPORTANT NOTE: Although this is a common example, it does not imply that the numbers provided above are accurate and must be achieved through the verification of a particular system. Sensor failures that might occur include: -The voltage across the ECT signal terminal is the same as zero volts.

  • Check for short circuits to ground at the sensor terminals. Examine the signal cables that connect the sensor to the onboard controller to ensure that they are not damaged. Ensure that all power supply and ground connections of the onboard controller are properly connected if all wires are connected correctly but there is no output voltage from the onboard controller. While it is true that the supply voltages and grounds are OK, the onboard controller itself is suspect.

-The voltage across the ECT signal terminal is the same as 5.0V. When an open circuit is present, the voltage has this value, which may be obtained under any of the following conditions:

  • Because the signal terminal of the ECT sensor does not give connection to the sensor
  • The sensor’s circuit is open
  • And the sensor’s ground circuit is open, the sensor cannot function.

-The voltage signal, also known as the reference voltage, is equivalent to the voltage of the automobile battery.

Short circuits in the wires that are linked to the positive terminal of your automobile battery or your power source should be checked for any signs of damage. A negative temperature coefficient sensor is required. An ohmmeter should be used with an ECT sensor that has been removed from the vehicle.

  • Place the sensor in a suitable water container and take the temperature of the water using the sensor. Measuring resistance of the sensor and comparing it to the numbers in Table-1, which shows the relationship between the resistance and the temperature, is recommended. Heat the water and take frequent readings of it, as well as the resistance of the sensor, to determine its temperature. Take a look at the results in comparison to those in table 1.

—A temperature sensor having a negative coefficient of temperature —The use of an oscilloscope to measure voltage

  • Assign the active end of the oscilloscope probe to the signal terminal of the sensor, and the ground end of the probe to the chassis ground. Make sure that the oscilloscope’s trigger sweep is set to continuous measurement mode (registration of slowly changing signals)
  • Place the sensor in a container of warm water that is appropriate for the situation. After a few minutes of measurement, and while the water is heating, the voltage change curve of the sensor will be displayed on the oscilloscope screen (Fig. 2). Precautions should be taken to ensure that the measurement time is not exceeded – about 10 minutes
  • It is recommended to regularly monitor the temperature of the heated water using a thermometer and compare it to the values indicated in table 1
  • And

Sensor having a positive temperature coefficient, as shown in Fig. 2. A thermistor with a positive temperature coefficient of resistance is an ECT sensor with a positive temperature coefficient of resistance because its resistance increases as the temperature rises. It is only utilized in a small number of systems at this time (mainly in Renault cars). The general technique of verification is identical to the approach described above for verifying a sensor with a negative temperature coefficient in terms of its overall structure and operation.

Temperature, ºС Resistance, Ω Voltage, V
254 – 266
20 283 – 297 0.6 – 0.8
80 383 – 397 1.0 – 1.2
open circuit 5.0 ± 0.1
short circuit to ground

AAMCO Keller Blog

The Engine Coolant Temperature Sensor in your automobile is critical in keeping your car’s engine operating within its ideal heat range and in preventing your car from operating over the alert level without telling the driver via the instrument panel of a potential problem. The heat in Texas in the summer is no joke, and the team of locally trusted specialists at Aamco of Keller is here to ensure that you and your car remain safe on the road during the summer months. Maintaining a regular schedule of automobile tune-ups and preventative maintenance can assist in identifying possible problems before they become costly repairs.

The sensor monitors the operating temperature and sends an alarm to the on-board computer if there is a possible problem with the system.

How the does the Engine Coolant Temperature Sensor Work?

When the coolant temperaturesensor (CTS) is located in close proximity to the engine thermostat, it has the best chance of performing properly. The CTS’s tip is most likely situated very adjacent to the engine’s coolant supply line. The sensor operates by sensing the temperature that is being emitted by the thermostat and/or the coolant itself, and then storing that information. The temperature reading is subsequently delivered to the on-board control system for further processing. This information is then used by the computer in your car to determine whether to continue functioning or change certain engine operations, with the goal of maintaining an optimal engine temperature at all times.

Besides that, it may indicate the requirement for a richer fuel mixture or the necessity to open the exhaust gas recirculation system.

What happens when a Car’s Engine Coolant Temperature System begins to fail?

Similarly to any other component in your vehicle, the sensor might become faulty over time and become out of commission. This can result in a variety of issues, including the engine being overheated. It is possible to visually check the engine sensor if you know where it is located and what it looks like. This will allow you to determine whether or not it has developed any cracks or fissures. While this visual check might be beneficial, it will not assist you in diagnosing every conceivable problem because certain sensor faults can manifest themselves without the presence of visual proof.

If your sensor is not functioning properly, it will transmit a signal to the computer, resulting in the illumination of your Check Engine light. If you notice the Check Engine light illuminate, take your vehicle to a skilled mechanic as soon as possible.

Replacing the Car Engine Coolant Temperature Sensor

The sensor, like any other component in your vehicle, might become faulty over time and become unusable. In addition to overheating the engine, this can result in a variety of other issues. It is possible to visually check the engine sensor if you know where it is located and what it looks like. This will allow you to determine whether or not it has cracked or fractured. This visual examination, while useful, will not always assist you in diagnosing every conceivable problem because some sensor faults might manifest themselves without the presence of visible signs.

As soon as you notice the Check Engine light illuminate, bring your vehicle in for expert service.

Aamco of Keller Your Car’s Engine Coolant Temperature System Experts

The safety of you and your family on the road is extremely important to us here at AAMCO Keller. If you feel you may be experiencing problems with your vehicle’s engine coolant temperature system, contact AAMCO Keller to have one of our skilled technicians accurately assess your vehicle’s problem. Call or stop by our store, which is located at 1485 South Main St., Keller, TX 76248, to schedule an appointment today. Have your engine coolant temperature system tested by the specialists at AAMCO of Keller, who are well-known in the community.

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As a result, AAMCO Transmissions of Keller employs the best-trained specialists in the business, who have not just 20 years of expertise working on new automobiles, but also more than 50 years of combined industry experience. Not only do we want to deliver the greatest product in the market, but we also want to provide the best customer service possible. Following the completion of a recent survey, it was discovered that more than 95 percent of automobiles serviced at AAMCO with substantial repairs are still in service, with many having reached the 100,000-mile mark without failure.

  1. As a result, all of our services are backed by a minimum of a one-year warranty, rather than the normal 90-day warranty given by most repair facilities.
  2. AAMCO of Keller is a full-service vehicle repair and preventative maintenance facility.
  3. We are experienced in both automatic and manual transmissions.
  4. If you require servicing or maintenance, we are conveniently positioned for you.
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Toss in your automobile (car, SUV, or truck) today and let us to give you with outstanding service. We look forward to taking care of your automobile. AAMCO Auto Repair | Auto Repair | Engine Repair | Engine Coolant | AAMCO Auto Repair | AAMCO Auto Repair

What does a Coolant Temperature Sensor do for your vehicle?

Sensor for measuring temperature – gauge ” data-medium-file=” data-large-file=” data-small-file=” loading=”lazy” id=”longdesc-return-38005″ tabindex=”-1″ src=” alt=”Temperature Sensor – Gauge” tabindex=”-1″ src=” alt=”Temperature Sensor – Gauge” width: 300px; height: 170px; longdesc=” referrer=38001″ referrer=38001 data-lazy-src=” srcset=”data:image/gif;base64,R0lGODlhAQABAIAAAAAP/yH5BAEAAAAALAAAAAABAAEAAAIBRAA7″ data-lazy-src=” srcset=”data:image/gif;base64,R0lGODlhAQABAIAAAAAP/yH5BAEAAAAALAAAAAABAAEAA The resistance of the Coolant Temperature sensor fluctuates in response to temperature.

It is essential for numerous PCM tasks, including fuel injection, ignition timing, variable valve timing, transmission shifting, and transmission shifting, if the Coolant Temperature sensor is operational.

Where are these sensors located?

Typically, theCoolant Temperature sensor is situated in a coolant tube in the engine, close to the thermostat, but not always.

Will a malfunctioning Coolant Temp Sensor illuminate the check engine light or affect vehicle operation?

Yes, a failed sensor can cause the MIL to illuminate, resulting in the engine running rich or lean depending on the situation. It is possible that the transmission may shift wrongly or that the torque converter will not lock up.

What are the common causes of failure?

This type of sensor fails most frequently as a result of corrosion within the cooling system. It is also possible that coolant will leak via the wire link.

How to determine if these sensors are malfunctioning?

If an aberrant reading is detected, a DTC will be set, with the P0116 code indicating sensor performance, the P0117 code indicating low input, and the P0118 code indicating high input. If the engine has not been operated for more than an hour, the temperature measurement from the Coolant Temperature sensor should be very similar to the temperature reading from the air charge/manifold on a scan tool. A voltmeter may be used to verify that the sensor circuit is operating at the right voltage. Take a look at all of the NAPA Online products available, or visit one of our 17,000 NAPA AutoCare stores for regular maintenance and repairs.

The image is courtesy of Pixabay.

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Symptoms Of Bad Coolant Temperature Sensors

It is part of the coolant temperature sensor’s responsibility to precisely indicate the coolant temperature of your car’s coolant that it ensures the correct blend of gasoline is utilized. Because a greater fuel-to-air ratio is required when the engine’s temperature is cooler, if your ECT reports a cold temperature when your engine is actually warm or hot, more fuel will be consumed than is required.

A faulty coolant temperature sensor may frequently show a lower temperature than the actual temperature of the coolant.

Irregular Temperature Readings

It’s possible that the engine coolant temperature sensor is malfunctioning if you observe greater variation in your engine temperature or if it appears higher or lower than normal when you’re driving. In particular, if your engine does not appear to be warming up as quickly as it should, you should have a professional examine your cooling system. While it is possible that the temperatures outdoors are cooler, it is also possible that the temperature being recorded is erroneous and is lower than the real temperature.

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Black Smoke from Your Exhaust

In addition to the fuel ratio being controlled by the coolant temperature sensor, if there is an excessive amount of surplus fuel being utilized, it may not be able to burn off in the combustion chamber properly. As a result, you may detect black smoke pouring from your exhaust, which indicates that the leftover gasoline is being burnt there instead of in the engine compartment. While a little amount of black smoke will not render your vehicle undriveable, it is a warning that you should avoid driving your vehicle and instead take it to a competent technician for cooling system repair.

Your Engine is Overheating

In addition to sending a permanent cold signal when the engine coolant temperaturesensor is malfunctioning, it can also malfunction in such a manner that it provides a hot signal when your engine temperature is safe. In this instance, your car may inform you that your engine is overheating when it is not. As a result, you will most likely see a dashboard warning light illuminated and your car may not function correctly.

Your Check Engine Light is On

In addition to receiving a warning that your engine is overheating, you may notice that your check engine light is illuminated if your coolant temperature sensor is malfunctioning or has malfunctioned. If the computer in your automobile detects a problem with the signal your sensor is delivering, the check engine light may illuminate. However, if your check engine light comes on, it is a solid indicator that you should take your automobile to an experienced repair.

Engine Coolant Temperature (ECT) Sensor

ECT sensors, also known as engine coolant temperature sensors, are variable resistors that modify the resistance of a 5-volt reference signal from the PCM to measure the temperature of the engine coolant. The signal from the sensor fluctuates in response to the temperature of the engine’s coolant. It is a critical component in maintaining the proper operating temperature of an engine. The thermostat housing is frequently found in the coolant stream, on or near the thermostat housing. It measures the temperature of the engine’s coolant.

They are referred to as (NTC) thermistors, which stands for negative temperature coefficient.

This sensor drops more voltage when it’s cold than when it’s hot, thus it’s better to keep it cool.

In addition to an excessively rich air-to-fuel ratio and low fuel mileage, a defective ECT sensor can also cause an inoperative torque converter clutch.

(ECT) Engine Coolant Temperature Sensor – What Can Go Wrong

When It Comes to Engine Coolant Temperature Sensors (ECT), there are several things that can go wrong.

The (ECT) sensor, is an engine management system sensor; that is used to monitor, the temperature of the engine’s coolant.

A thermistor with a Negative Temperature Coefficient (NTC) is a common example of an ECT sensor. This is due to the fact that its electrical resistance diminishes as the temperature rises. This signal is subsequently delivered to the engine’s computer, where it is processed. It is possible to alter the engine’s timing and fuel calculations in order to get optimal performance. The result is that engines consume more gasoline while they are cold and less fuel after they have reached maximum operating temperature.

The computer will also scale back engine performance settings; if it detects that the engine temperature is too high.

As a result, it has the potential to safeguard the engine from harm caused by overheating. The temperature of the engine is quite important in the calculations of engine performance. As a result, any fault with the coolant temperature sensor might soon manifest itself as a decrease in engine performance.

How Does It Work

An (ECT) sensor is attached to the main computer (powertrain control module or other similar device) (PCM). This module generates a reference voltage (usually 5 Volts) and continuously analyzes the sensor signal from the (ECT). The (PCM) makes adjustments to the engine’s performance based on this signal. The electric radiator fans are also operated when the temperature reaches a specified level, according to the program. Sensor with O-Ring kind of mounting for (ECT) applications. If the signal from the sensor is not there, or if it is outside of the predicted range, the (PCM) illuminates the Check Engine light and records the issue code associated with it in its memory, respectively.

What Can Go Wrong

One of the most prevalent issues is when the sensor has a bad connection either inside or outside the connector, which is typical. Interruptions in the signal are caused by this, and the (PCM) is responsible for establishing the problem. It has been observed that the temperature gauge in certain automobiles displays irregular readings as a result of this problem.

The engine may run in fail-safe mode:

  • It is possible that the air conditioner will quit operating. It is possible that radiator fans will operate continuously.

Numerous Check Engine light codes associated with the (ECT) sensor might be triggered by a variety of different factors. For example, a faulty thermostat or problems with the cooling system, or even a leaky head gasket, are all possibilities. As a result, the problem must be thoroughly identified and diagnosed.

So, the tip of the sensor, has to be immersed in coolant. As a result, a low coolant level inside the cooling system; can cause the signal from the sensor to be incorrect.

When dealing with cooling system issues, it is always necessary to check the coolant level first and foremost. If there are any broken pins or rust on the (ECT) sensor connector, it must be replaced. There are numerous methods for testing the (ECT) sensor, and the service handbook will outline the proper method to use. Coolant Temperature Sensor is being tested (ECT) As the temperature of the engine rises, the efficiency, power, and fuel economy of the engine all improve.

In an ideal situation, the engine will run as hot as possible without boiling its coolant or causing damage to any of its internal components. A defective engine coolant temperature (ECT) sensor, on the other hand, might have catastrophic consequences for an engine or its associated components.

Common Failure Symptoms

  • Excessive fuel consumption, black smoke coming from the exhaust, engine overheating, illuminated Check Engine Light, poor engine performance or stalling, increased emissions

Poor Fuel Economy

Excessive fuel consumption, black smoke coming from the exhaust, engine overheating, illuminated Check Engine light, poor engine performance or stalling, increased emissions

Black Smoke From Exhaust

Another sign of a probable problem with the (ECT) sensor is the presence of black smoke coming from the vehicle’s exhaust. A faulty sensor might potentially deliver a chilly signal to the computer, which can cause it to malfunction. Tailpipe Smoke in the Dark Because of this, the computer becomes confused, and the engine’s fuel mixture is artificially enriched as a result. Because of this, if the fuel mixture gets extremely rich, the fuel will not be able to burn completely in the combustion chamber.

Engine Overheating

In addition to overheating, an issue with the coolant temperature sensor might manifest itself as a stalling engine. It is also possible for the coolant temperature sensor to malfunction in such a way that it sends a signal that is persistently heated. As a result, the computer improperly compensates for a weak signal as a result of this error. Overheating of the engine All of these factors can contribute to overheating, as well as misfires and engine pinging. Additionally, it may fail to slow down the ignition timing and switch on the cooling fans when they are required.

Illuminated Check Engine Light

Another indicator of a probable issue with the (ECT) sensor is the illumination of the Check Engine Light (CHEV). The computer in many, but not all, automobiles has the ability to activate the Check Engine Light. The Check Engine Light is illuminated. When it identifies an issue with the sensor’s signal or circuit, it will usually alert the user.

Poor Engine Performance Or Stalling

While your engine is initially started when it is cold, it consumes more gasoline than usual. However, if the engine does not receive enough gasoline, it will not idle smoothly. When the engine’s computer receives a signal from the (ECT) sensor, it knows when to inject more fuel during a cold start. A defective sensor might cause the computer to become confused, preventing it from supplying adequate gasoline. This causes the engine to jerk, stall, misfire, or have poor engine performance as a result of the problem.

Increased Emissions

It is possible that the sensor will provide an erroneous “cold” reading, causing the engine to run rich. As a result, carbon monoxide emissions will rise, and it is possible that hydrocarbon emissions may rise as well. The opposite is true: if the sensor provides an incorrect “hot” reading, the engine may misfire and run rough, which increases hydrocarbon emissions.

How To Take Care Of Your (ECT)

If you need to replace the radiator or the coolant reservoir, do not use tap water:

  • Rust and other minerals are present in tap water, and these components may be detrimental in the long term. When water boils and evaporates within the radiator, coolant is very important because it stops the water from boiling. Additionally, it lubricates the engine block and radiator, which helps to avoid rust development.

Maintain Constant Surveillance for Leaks:

  • Repair any oil leaks or gasket leaks as soon as possible. If oil is allowed to penetrate the engine block, it will pollute the coolant. A consequence of this is that the service life of the coolant temperature sensor is reduced

Low level of coolant

  • Relatively low coolant level


The engine control temperature sensor (ECT) is one of the most significant engine management sensors.

Because the coolant temperature sensoris a critical component in ensuring that your engine operates at peak performance, it must be installed correctly. As a result, if you believe that your coolant temperature (ECT) sensor is malfunctioning, you should replace it immediately. Thank you very much!

4 Signs Your Coolant Temperature Sensor is Faulty

The coolant temperature sensor is in charge of keeping track of the temperature of the coolant in your car’s engine at all times. It is vital to keep an eye on the engine coolant since the engine’s fuel requirements are higher when the engine is cold and lower when the engine is warm. When the sensor detects a rise in coolant temperature, it sends a signal to the vehicle’s onboard computer. Using this signal, the engine timing and fuel injection may be adjusted, as well as other parameters. This enables for the most efficient engine performance possible.

Faulty Coolant Temperature Sensor – 4 Symptoms to Look Out For It is critical to understand that if the coolant temperature sensor in your automobile fails, it has the potential to cause harm to your car’s engine.

When you observe a decrease in your fuel economy, this is one of the first signs that you may have a defective coolant temperature sensor in your vehicle.

  • In your automobile engine, the coolant temperature sensor is in charge of keeping track of how hot the coolant is becoming. Engine coolant monitoring is required since the fuel needs of the engine are higher when the engine is cold and lower when the engine is warm. The sensor sends a signal to the car’s computer when it detects a rise in coolant temperature. This signal is then utilized to alter the engine timing as well as the fuel injection timing, among other things. This enables the engine to operate at peak capacity. If the computer determines that the engine is overheating, the performance parameters will be reduced in order to prevent overheating from happening. 4 Typical Symptoms of a Faulty Coolant Temperature Sensor You should be aware that if the coolant temperature sensor in your automobile fails, it has the potential to cause serious engine damage. The following warning indications should not be ignored: Increase in the amount of fuel consumed. When you observe a decrease in your fuel economy, this is one of the first signs that you may have a defective coolant temperature sensor in your car. As a result of the following, something occurs:

The Check Engine Light Begins to Flash If your check engine light begins to flicker, it might also be a sign that your coolant temperature sensor is malfunctioning. When this warning light illuminates, we recommend that car owners have it checked out as soon as possible to avoid any engine problems. If you are unable to determine what is causing the “check engine light” to illuminate, you should seek the assistance of a professional technician immediately. Overheating of the engine A malfunctioning coolant temperature sensor might result in your car’s engine overheating, which would be dangerous.

The computer will make another erroneous calculation of the signal, causing the engine to heat up instead of cool down.

Exhaust smoke is a dark gray color.

What occurs is as follows:

  • It is possible that incorrect readings from the coolant temperature sensor will cause the engine to miscalculate the air-fuel mix in the engine. The fuel will not be able to burn within the combustion chamber if the air-fuel mix ratio is not in proportion, and if the fuel mixture becomes too rich. A consequence of this is that the gasoline will be burned up in the car’s exhaust pipes, resulting in the discharge of black smoke from the exhaust. To avoid driving a car if there is an excessive quantity of black smoke coming from the exhaust pipe, turn off the engine. Get your automobile checked out by a professional as soon as possible if you observe this with your vehicle.
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Warning Signs Should Not Be Ignored Keeping your engine operating at peak performance requires the proper operation of the coolant temperature sensor. This is accomplished by the automobile computer calculating engine timing and fuel injection depending on information provided by the sensor. If the signal is incorrect, the outcome of this critical computation will be incorrect. If you see any of the indicators listed above, take your automobile to a mechanic right away to avoid serious engine problems.

If you feel that you have a problem with your coolant temperature sensor, come to Virginia Auto Service for a quick diagnostic and resolution of the problem.

We can assist you if you require any additional auto repair services or even if you are seeking for normal maintenance. Give us a call at 602-266-0200 right now, or arrange an appointment with us online whenever it is most convenient for you.

How to Check & Replace an Engine Coolant Sensor

Automobile Repair Library, Auto Parts, Accessories, Tools, Manuals and Books, Car BLOG, Links and Index are some of the resources available on this website. 2021 AA1Car.com is a trademark of Larry Carley. A very basic sensor that measures the internal temperature of the engine, the engine coolant temperature (ECT) sensor measures the temperature of the engine coolant. When the engine is operating, the coolant inside the engine block and cylinder head(s) absorbs the heat generated by the cylinders.

This sensor is particularly significant since the data it sends to the PCM has an impact on the operating strategy of the whole engine management system, making it a critical component.

The operating temperature of the engine has an impact on a number of the PCM’s operations, including fueling, ignition, emissions, and drivetrain operation.

Cold driveability, idling quality, and emissions are all improved as a result of this.


Depending on how the coolant sensor is configured, it may be utilized by the PCM for any or all of the following functions: * On fuel-injected engines, turn on the fuel enrichment system. A cold signal from the coolant sensor causes the PCM to increase injector pulse width (on time), resulting in a richer fuel mixture being produced by the injectors. This increases the quality of the idle and helps to reduce hesitation while the cold engine is becoming warm. During normal operating temperature, the PCM leans out the fuel mixture to minimize emissions and fuel consumption as the engine reaches its usual operating temperature.

It is possible that a coolant sensor that constantly reads hot can create cold driveability issues such as stalling, hesitancy, and rough idling.

Until the engine achieves normal operating temperature, it is common practice to reduce spark advance for emission control purposes.

* The use of exhaust gas recirculation (EGR) during the warm-up period.

It is possible that allowing EGR while the engine is still cold can result in a rough idle, stalling, and/or hesitation.* Evaporative emissions control canister purge Fuel vapors contained in the charcoal canister are not expelled until the engine has reached operating temperature in order to avoid driveability issues.

  1. When the coolant reaches a specific temperature, the PCM may ignore the rich/lean feedback signal generated by the oxygen sensor.
  2. Once the engine has reached operating temperature, if the PCM fails to enter “closed loop,” the fuel mixture will be overly rich, causing the engine to pollute and emit waste gas.
  3. * Idle speed throughout the warm-up period; When a cold engine is initially started, the PCM will often boost the idle speed to prevent stalling and improve the quality of the initial idle.
  4. If the PCM decides to delay locking up the torque converter until the engine has warmed up, cold driveability will be improved.

This job is quite vital in order to avoid the engine from being overheated. Note: On some cars, a separate coolant sensor or fan switch may be installed only for the purpose of controlling the cooling fan circuit.


The majority of coolant sensors are “thermistors,” which alter resistance in response to variations in the temperature of the coolant. The majority of them are of the “NTC” (Negative Temperature Coefficient) variety, which means that resistance decreases as the temperature rises. When the engine is cold, the resistance of this sort of sensor is quite high. Because of the internal resistance of the sensor, it decreases as the engine heats up, eventually reaching its smallest value when the engine is operating at its usual operating temperature.

  • At 32 degrees, a Ford coolant sensor may register 95,000 ohms and plummet to 2,300 ohms at 200 degrees, according to the manufacturer’s specifications.
  • The coolant sensors are connected by two cables (input and return).
  • The amount of resistance present in the sensor decreases the voltage signal that is subsequently sent to the PCM for processing.
  • It is possible to see this number shown on a scan tool, and it may also be used by the instrument panel cluster or driver information center to indicate the coolant’s temperature.
  • A temperature threshold is reached by the coolant and the PCM alters the reference voltage applied to the sensor in order to obtain a more accurate reading of the coolant temperature (higher resolution).
  • Some of them are basically on/off switches that are activated or deactivated when a preset temperature is reached.
  • These earlier coolant sensors are often single wire sensors, as is the case with this model.
  • Rather than temperature sensors, these are more commonly referred to as temperature “senders.”


In most cases, the coolant sensor is situated near the thermostat housing in the intake manifold of the vehicle. Occasionally, the coolant sensor may be housed within the cylinder head, or there may be two coolant sensors (one for each cylinder bank in a V6, or one for each cylinder bank in a V8 engine), or one for the PCM and a second for the cooling fan on some cars.

The sensor is placed in such a way that the tip of the sensor will come into direct contact with the coolant. This is necessary in order to provide a dependable signal. If the coolant level is too low, the coolant sensor may not be able to measure the temperature properly.


Because the coolant sensor plays such a critical part in the activation of so many engine systems, a defective sensor (or sensor circuit) will frequently result in poor cold driveability and emission issues in the vehicle. Furthermore, a malfunctioning coolant sensor might result in a visible increase in fuel consumption, as well as the failure of an emissions test if it stops the engine management system from entering closed loop. Maintaining the proper perspective, many coolant sensor problems are caused more often by wiring errors and loose or corroded connections than they are by the sensor itself.

If the thermostat is jammed open, the engine will take a long time to warm up and the coolant sensor will indicate that the coolant level is low.

When the engine becomes hot, a defective coolant sensor may potentially cause the engine to overheat if it fails to activate the cooling fan relay when the engine becomes hot.


It is possible that a defective coolant sensor will prohibit some of the system monitors from working on cars built after 1996 and equipped with OBD II onboard diagnostic equipment. As a result, the vehicle will be unable to pass an OBD II emissions test since the test cannot be performed until all of the mandatory system monitors have been performed and passed. The defect should be detected by the OBD II system, which should illuminate the Check Engine Light (CEL) or Malfunction Indicator Lamp (MIL) and set one of the diagnostic trouble codes listed below: P0115.Engine Coolant Temperature Circuit P0116.Engine Coolant Temperature Circuit Range/Performance P0117.Engine Coolant Temperature Circuit Range/Performance P0118.Engine Coolant Temperature Circuit P0119.Engine Coolant Temperature Circuit Range/Performance The engine coolant temperature circuit has a low input voltage (P0117).

P0118.High Input Engine Coolant Temperature Circuit (P0118).

When the coolant sensor is shorted, open, or reading outside of its range, the Check Engine light may illuminate on older vehicles that were built before OBD II.


Connecting a scan tool to the OBD diagnostic connector on your engine is a quick and easy approach to check the accuracy of your engine’s coolant sensor. When the engine is COLD, open the sensor data menu and compare the coolant sensor temperature value with the air temperature sensor reading to see which is higher. Both sensors should have readings that are within a degree or two of one another. If the readings from the two sensors are considerably divergent, one of the sensors is defective.

  1. Temperature readings from the ambient air temperature sensor should stay consistent, while the coolant temperature sensor should indicate a progressive increase in coolant temperature.
  2. Your scan tool should be able to display the output of the coolant sensor in degrees Centigrade (C) or Fahrenheit (F) for 1996 and newer vehicles equipped with OBD II (F).
  3. This indicates a malfunctioning sensor or a wiring problem if there is no change in the reading or if the reading clearly does not match the engine temperature measurement.
  4. If the sensor is open, shorted, or reads outside of its operating range, it must be repaired or replaced immediately.
  5. Before any parts are changed, more diagnostics will be required to determine the source of the problem.
  6. If the wire continuity is excellent, but the PCM does not enter closed loop when you feed it a “hot coolant” signal, the fault is with the PCM itself, not with the wiring.

It is also necessary to do a visual inspection of the coolant sensor to look for issues such as significant corrosion around the terminal, damaged or loose wires, a break in the sensor, or coolant leaks around its perimeter base.


The output of the sensor can also be checked using an instrument like a voltmeter or a digital storage oscilloscope (DSO). Specifications vary, but in general, a cold coolant sensor will read something in the neighborhood of 3 volts. With time, and as the engine warms up and achieves operating temperature, the voltage loss should steadily reduce until it is around 1.2 to 0.5 volts or less. The voltage signal should be shown on a scope, and you should see a line that progressively slopes from 3 volts down to 1.2 to 0.5 voltages in three to five minutes if you’re using a scope (or however long it normally takes the engine to reach normal operating temperature).

  • It is possible that the sensor has been shorted or that it has lost its reference voltage if the voltage is near to 0.
  • This is typical and is caused by a 1000 ohm resistor that is activated when the sensor’s voltage dips to around 1.25 volts and switches into the coolant sensor circuit.
  • It is possible for a coolant sensor to abruptly open or short when the temperature exceeds a specific threshold.
  • The appearance of a short while observing the voltage pattern on a scope is that of a quick decrease or dip in the trace to zero volts.
  • If the coolant sensor reads normally while it is cold (high resistance and 3 or more volts), but never appears to reach normal temperature, it is possible that it is telling the whole truth.


The vast majority of coolant sensors are not changed unless they have failed completely. It is evident that a coolant sensor that is shorted, open, or reading outside of its temperature range cannot produce a reliable temperature signal and must be replaced in order for the engine management system to work correctly. Many experts, however, advise changing the coolant sensor if you are repairing or rebuilding an engine as part of the process. Why? Because coolant sensors can degrade with time and may not read as precisely as they did when they were first installed, it is important to replace them every few years.

  1. If the engine has overheated to a dangerous level, it is also a good idea to replace the coolant sensor and the thermostat.
  2. It is necessary to remove part of the coolant from the cooling system in order to replace a coolant sensor.
  3. Simply open the drain valve and drain enough coolant from the engine to bring the coolant level in the engine down to below the sensor.
  4. If the coolant shows any symptoms of pollution, it would also be a good idea to change the coolant and cleanse the system.
  5. To avoid damage to the sensor, tighten it slowly and gently.

The cooling system can be re-filled after the replacement sensor has been placed and tested. Check to see that all of the air has been sucked out of the cooling system. The presence of trapped air behind the thermostat may cause the engine to overheat or the coolant sensor to fail to read properly.

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More Information on Sensor Guide may be found by clicking here. A short reference guide to the operation and testing of fundamental sensor components.

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