What is an ECT Sensor? 

When an internal engine combustion runs, thousands of tiny explosions happen every minute inside. It’s no stretch of the imagination that it generates immense amounts of heat that could destroy an engine in a very short time. That’s why cooling systems exist, and the engine coolant temperature sensor helps keep it in an efficient operating range.

An engine coolant temperature sensor, or ECT sensor, is used to determine how hot the engine coolant is. It’s rudimentary in the way it works compared to many other sensors in a vehicle in that it typically has two wires and a threaded section that screws into a port in the cooling system. And depending on your car’s design, a coolant temperature sensor can range from $3 to more than $500.

In most situations, the sensor is a thermistor that has decreasing electrical resistance as the temperature goes up. One wire offers supply voltage for reference, and the change in voltage on the second wire is measured by the ECU to approximate the coolant temperature.  

Today, many vehicles have more than one engine temperature sensor installed. This way, the car’s computer can detect whether the thermostat is open or closed. 

However, it’s more than just monitoring temperature for the dash gauge. The ECT sensor’s signal is used by the engine control module to adjust the car’s performance and to initiate the cooling fans. If it stops working, you’ll not only be unable to see the engine temperature on the cluster but your engine could be vulnerable to overheating. 

Symptoms of a Failed ECT Sensor 

The ECT sensor is a critical part of your engine’s cooling system, and it plays a critical role in engine performance too. It monitors the temperature of the coolant and relays that information to the engine control unit. If the ECT sensor fails, it can cause a number of problems.  

The most common symptom is an overheating engine. The ECT sensor is responsible for triggering the fan when the engine gets too hot, so if it fails, the fan will not turn on. As a result, the engine will continue to heat up until it seizes.  

Other symptoms of a failed ECT sensor include: 

  • Poor fuel economy 
  • A check engine light 
  • Engine knock or ping from improper timing adjustment 
  • Rough idle 
  • And an incorrect temperature reading on the dash. 

If your ECT sensor fails, it’s important to have it replaced as soon as possible. Otherwise, you could be facing major engine damage. 

Where the ECT Sensor is Located 

The ECT sensor is often located on the engine block, usually near the thermostat housing. On some engines, it may be located on the intake manifold. The sensor measures the temperature of the coolant and sends a signal to the computer. The computer uses this information to adjust the ignition timing and fuel mixture.  

However, the location isn’t always the same, so pulling up a repair procedure online is a great idea before you start taking things apart. 

How to Change an ECT Sensor

Fortunately, changing an ECT sensor is a relatively easy job that anyone can do with a few tools and some basic knowledge. Here’s how to do it:

1. Let the engine cool

Hot coolant can scald you, causing serious burns. Always let the engine cool completely before working on the cooling system.

2. Find the sensor

First, you’ll need to locate the ECT sensor. It’s usually located on the thermostat housing or on the water pump. Once you’ve found it, disconnect the electrical connector.

3. Drain the coolant if necessary

Most ECT sensors are mounted high on the engine, so there will be minimal coolant loss when the sensor is removed. If yours is not at the top, it might be necessary to drain the engine coolant first. It’s a good time to refill it with new coolant, if that’s the case.

4. Remove the sensor

Unscrew the sensor from its mounting bracket. A box end wrench that fits well is your best choice here.

5. Install the new sensor

Next, take the new ECT sensor and screw it into place. Be sure not to overtighten it, as this can damage the threads.

6. Top up the coolant

If you had to drain coolant for your ECTS replacement, now’s the time to fill the engine coolant system.

7. Finish assembly

Reconnect the electrical connector, start up your car, and check to make sure that the engine temperature is reading correctly. If it is, then you’re done! Changing an ECT sensor is a simple process that any DIYer can do. Just be sure to follow these steps carefully and you’ll be back on the road in no time.

What Does It Cost to Replace an ECT Sensor? 

If your ECT sensor needs to be replaced, it will typically cost between $200 and $400. This includes the cost of labor, which is usually between $100 and $150, and the cost of parts, which is usually between $5 and $250. The exact cost will depend on the make and model of your vehicle and where you have the work done.  

If you have a luxury vehicle, or if you need to have the work done by a dealership, you can expect to pay on the higher end of this range. However, if you have a more affordable vehicle and you’re able to do the work yourself, you can expect to pay on the lower end of this range. Either way, it’s important to budget for this repair so that you’re not caught off guard by the cost. 

Buy your ECT sensor at AutoZone with options for virtually every make and model. If you decide that it’s too big a job to tackle on your own, let AutoZone help you find qualified professional mechanics through our Shop Referral Program.  

FAQ/People Also Ask 

What does a faulty ECT sensor do? 

You’ll notice symptoms like excessive fuel consumption, decreased performance, rough idle, and a Check Engine Light on. 

Where is the ECT sensor located? 

For most vehicles, the ECT sensor is near the thermostat housing or water pump. However, it varies by model, so check a repair manual for the location on your car. 

What happens when the coolant temperature sensor goes out? 

Your coolant indicator on the dash won’t work, and your car’s performance and fuel efficiency will suffer if the engine temperature sensor fails. 

How do I know my ECT sensor is bad? 

You can test the resistance in the ECT sensor with a multimeter to determine if it’s working properly. 

How much does it cost to replace ECT sensor? 

On average, you’ll pay between $200 and $400 if you have a new ECT sensor installed at a repair shop. If you do it yourself, parts are a fraction of that price. 

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