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ECT Sensor – What Is It And How Does It Work?

ECT Sensor

Your ECT sensor is an important part of your vehicle that can help you with the inner workings of your car’s engine. In a car with an internal combustion engine, the cooling system is in charge of maintaining the temperature. This is done in order to prevent the engine from overheating. 

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The engine coolant temperature sensor, also known as the ECT sensor, is a negative temperature coefficient thermistor – meaning, the electrical resistance goes down, while the temperature rises. When a signal from the ECT sensor is missing or it is outside of the expected range, the powertrain control module turns on the check engine light. The ECT can be known as a thermistor that changes resistance depending on the temperature. 


What Is The ECT Sensor?


Since we know that the temperature sensor is a negative temperature coefficient thermistor, we know that the electrical resistance decreases when the temperature increases. The end of the ECT sensor enters into one of the cooling system passages, where it is covered in coolant.


Many cars contain more than one coolant temperature sensor. If there is an issue with the coolant temperature sensor, the coolant temperature light might turn on. In most vehicles, the main ECT sensor is called the primary ECT sensor, or ECT sensor one. This is installed near the thermostat within the cylinder head or block. The cylinder head sits above the cylinders on top of the cylinder block in an internal combustion engine. The cylinder head is in charge of closing the top of the cylinder to form the combustion chamber. 


A second coolant temperature sensor is generally installed in another part of the engine or in the radiator. It is important to keep the radiator in working condition, since this is the most common source of antifreeze leaks. This ECT sensor works together with the ECT sensor one.


Some cars use a cylinder head temperature or a CHT sensor in addition to the ECT sensor. The CHT sensor works similar to the ECt sensor, but it measures the cylinder head metal temperature. This allows the CHT sensor to measure the engine temperature correctly, even if the coolant is leaking. 


The ECT sensor is connected to the main computer, also known as the powertrain control module. The PCM provides a reference voltage and monitors the ECT sensor signal. Depending on this signa, the PCM changes the engine performance and radiator fans when the temperature hits a certain level.


If the ECT sensor is missing, or is not in the proper range, the PCM turns on the check engine light and can store the trouble code for later problems.


ECT Sensor Problems


With any part of the car, the ECT sensor can have problems that need repairing and fixing. Keeping your parts in working order can ensure that you gain top dollar for them if you decide to sell your car later on. First, one of the most common ECT sensor problems is when the sensor contains a poor connection, or has a problem with the wiring harness. A wiring problem can cause the engine to stall. A disruption in the ECT sensor connection can interrupt the signal to the PCM, causing the PCM to set a fault. In some vehicles, the signs of this issue will show themselves as strange and erratic readings in the temperature gauge. This may cause the engine to run in fail-safe mode, causing the fans to run constantly and the air conditioner to shut off.


In addition to the connection issues, corrosion at sensor terminals can cause ECT sensor problems. Depending on the severity of the situation, the corrosion may have done extreme damage to the connector and CHT sensor. This may cause the connector and CHT sensor to be replaced. 


The last ECT sensor problem that is quite common is that the ECT sensor could be reading a bad thermostat or dealing with cooling system issues. The leaking head gasket could be a sign of ECT sensor problems. Since the ECT sensor is not an expensive part, a replacement is the best solution. 


Ways To Test The ECT Sensor


Now that we know what an ECT sensor is and the important function that it performs, we need to know how to test the ECT sensor if we think that it is faulty. Since the tip of the sensor has to be placed in coolant, the low coolant level inside the system can cause the ECT sensor signal to be faulty. The ECT sensor connector should be checked for damaged pins or corrosion. We will go over a few ways to test the ECT sensor.


Method 1 – Measure Resistance


One way to measure the ECT sensor resistance is to test the sensor at different temperatures and compare the readings to the base-line levels set forth in the service manual. The resistance of the sensor can only be measured when the sensor is properly removed from the circuit. If you measure the resistance of any component still within the electrical circuit, then the measurement won’t be correct. 


Method 2 – Checking the ECT sensor Voltage


A second way to test the ECT sensor is to measure the voltage across the sensor terminals while the ignition is turned on. The ECT sensor is connected to the powertrain control module. The PCM can supply the reference voltage, while another wire is the sensor ground. The reference voltage and the ground wire must be checked. When the resistance of the ECT lowers as the engine warms, the voltage drops as well. Comparing the ECT sensor resistance to the voltage is a way to determine if the ECT sensor is working correctly.


Method 3 – Compare The ECT Sensor Readings


Another way to measure the ECT sensor and see if it is working correctly is to measure the readings against other temperature sensors. You can use the intake air temperature sensor to perform the calculation and reading. If You perform this reading on a car that has been parked somewhere overnight, the temperature of hte engine, by utilizing the ECT sensor, and the temperature of the IAT sensor should be very similar. However, if the difference is much greater, then it would mean that one of the ECT sensors is faulty and incorrect.


Method 4 – Diagnose Temperature Sensor Problems


If you have found that there is an intermittent problem with the ECT sensor, then you will need to use a scanning tool to diagnose the issue. Mechanics usually have this at their shop, and will know how to properly use the tool. With the scan tool connected, a mechanic can monitor the ECT sensor voltage while moving the harness connector. If there is a change in voltage, then this indicates a problem area. 


A second way to do this is with the ECT temperature. You could monitor the coolant temperature, and take note of hte temperature level. You can simulate an intermittent poor connection by disconnecting and quickly reconnecting the ECT sensor. If the temperature comes back up, this is a good sign regarding the accuracy of the ECT sensor. 


Another portion to notice with the temperature reading of the ECT sensor is that when it is disconnected, the temperature reading might not read correctly. This can show trouble codes relating to the ECT sensor. If the PCM sets a trouble code, it then stores a snapshot of parameters at the time the issue arose. This could show a problem with the ECT sensor or the wiring harness, which could cause your engine to stall.


ECT Sensor Replacement


In many cars, replacing the ECT sensor is a harmless and pain-free task. The sensor is generally held by a clip. In some cars, a deep socket might be needed, although this is rare. Replacing the ECT sensor in a repair shop generally runs from $59-$129 for an average car. The ECT part itself is not very expensive, so you can use a refurbished part if you choose.


After the ECT sensor is replaced, the cooling system will need to be checked to ensure that there are no air pockets within the system, affecting the coolant inside. When you are replacing the ECT sensor, it is imperative to change the new sensor to the personalized specifications. 


How To Avoid Problems With The ECT Sensor


Although this part of the vehicle was designed to last forever, there are many instances when this is not the case. As with all cars, problems can occur if you do not properly maintain the parts. Some owners get lazy, and others don’t want to think about the financial strain that it may cost to pay for some repairs. However, repairing and maintaining the ECT sensors so they work at an optimal level is crucial to the lifespan of your car. 


Here we will go over how to avoid some problems with the ECT sensor. By following these steps, you will hopefully avoid running into any issues that spring up from not maintaining the ECT sensor and the coolant system.


Never Use Tap Water


First, you should never use tap water to refill the radiator. Also, avoid using tap water to fill the coolant reservoir. Filling the reservoir with tap water can cause a coolant leak. Most tap water contains particles of rust and other detrimental minerals that can be harmful in the long run and the lifespan of your car. This can become especially prevalent if the water boils, since this will cause it to evaporate within the radiator. A leaking radiator is a very common car problem.


If you use proper coolant, this prevents the water from boiling, and does a better job at lubricating. The coolant can lubricate the engine block and the radiator, which doesn’t allow rust to form on the inner parts of the car. Using the correct ratio and mix of water and coolant in your vehicle can prevent rust from forming and increase the longevity of your car.


Fix Oil Leaks As Soon As Possible


Second, you should try to fix oil leaks and gasket leaks as soon as they occur. The majority of oil leaks are due to damaged engine gaskets, oil pan leaks, or poor connections. If oil enters the engine block, the coolant will then be contaminated with the oil. If the coolant is damaged, then this will reduce the service life of the temperature sensor. The mixture of coolant and oil will harm the ECT sensor and change the lifespan. In addition to the oil leak, high oil consumption can be a sign of a serious problem and corrosion in your engine. 


Fix Coolant Leaks As Soon As Possible


Third, you need to fix the coolant leaks immediately and quickly. The cooling system in your car is a sealed-type system, which means it is rare that you need to constantly fill the reservoir with water. If antifreeze is leaking, this can occur at your reservoir along with the coolant. If there isn’t enough coolant in the system, the ECT sensor might obtain false readings, which can negatively affect engine performance and the engine lifespan.


Cost Of Fixing The ECT Sensor


If you have found that your ECT sensor is providing bad readings and you care concerned about the lifespan of this mechanism, then you will need to get it fixed. The average cost for an engine coolant temperature sensor replacement generally runs between $203-$255. Labor costs are typically between $146 and $185 on average. The parts themselves are usually only $57-$70. 


What If My ECT Sensor Isn’t Working Properly and I Don’t Want To Fix It?


If you found that you need to fix your ECT sensor and you are worried about the funds for paying for hte repair, then you might want to look into other options. It is important to check on the other parts of your vehicle to see if they are in working order. If your car isn’t running well and it is old, you might consider selling your car for junk at a proper location.


Head to CashCarsBuyer for a fair quote, reputable service, and some money towards your new vehicle. By trading in your junk car, you can make some quick cash at a trustworthy spot. Remove all non-metal components from your car and sell them before bringing your car to CashCars. After you are done with the entire process, you will have plenty of money to save for your new, safe, and working vehicle!


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