ECT Sensor Function, Symptoms, And Diagnostics!
June 1, 2023Are you experiencing some bad ECT sensor symptoms and you are trying to learn the ECT sensor function? Well, if that is the case, you are at the right place because this article will be covering this topic and understand more about this sensor.
Doing your own research before you take your car to a shop to get it diagnosed is the way to go. Namely, in some cases, problems might be really simple such as this ECT sensor. And with a little bit of ingenuity and research, you can diagnose it in a matter of minutes.
And not only diagnosing it but replacing this sensor is also a breeze as we will find out later on in the article. The important thing for you right now is to make sure that you understand the function of the component first. And this article will try to focus primarily on this aspect and we will give our best to deliver you the best information possible.
First, we are going to learn what is the ECT sensor, then we will cover the ECT sensor location. Once we learn more about the location, we will learn the ECT sensor function. We will understand how this sensor works and what it does. Then we will cover some of the bad ECT sensor symptoms and learn more about how to diagnose and replace this component on your car. So, if you want to learn more, follow along.
What Is An ECT Sensor?
Now before we dive into the ECT sensor and its function as well as the symptoms that this component creates, let’s take a look at what is this sensor in general. A lot of people are here because of similar issues and are quite confused about this sensor. So, let’s elaborate really quickly.
So, what is an ECT sensor? Well, an ECT sensor is simply an engine coolant temperature sensor. Every car as you probably know has an engine and the engine has its own cooling system that consists of the radiator, thermostat, water pump, and upper and lower radiator hoses.
But the engine computer needs something to give it input on the temperatures inside of the block. So, this is why the ECT sensor exists. More on this, we are going to elaborate in the following chapters, where we will explain the ECT sensor function in great detail. Now let’s take a look at the location of this sensor and see where the ECT sensor is mounted.
ECT Sensor Location
So, we learned the basics when it comes to the ECT sensor and learned that this is an engine coolant temperature sensor. Now let’s take a look at where this sensor is mounted and learn how to find it on the engine.
As you probably know, there are a lot of carmakers out there and each of these carmakers decides to take things into their own hands and they often place some components in illogical places.
This is why when it comes to the ECT sensor, there is not a precise location that is fixed for every engine out there.
But usually, these sensors are mounted somewhere close to the upper radiator hose attach location like the intake manifold, or the engine block. But this is usually near the thermostat housing.
You will notice it because this component is practically bolted onto the engine from one side and from the other the sensor is connected to the PCM through the wiring harness. You just cannot miss it. In the video above, you can see where this sensor is mounted on a 2002 Ford Explorer. But what is the ECT sensor function? Well, that is a good question, and more on that, we are going to elaborate in the next chapter.
What is also worth noting is that there is a CHT sensor, also known as a cylinder head temperature sensor. And this sensor is usually mounted on the cylinder head. But looks the same and also functions in the same manner. More on the ECT sensor function, we are going to learn next.
ECT Sensor Function
We covered the ECT sensor location and learned how to find it on the engine. Now let’s take a look at its function and understand more about what this sensor does in reality.
What is important to note is that this sensor primarily serves the purpose of starting the engine. As you probably know, when a car is started on a cold morning, it usually runs a little bit rich until it warms up.
This type of work is quite necessary because you need that extra gas in the system. Because if the air-to-fuel mixture is too lean, the engine will stall. So, what the ECT sensor does is tell the computer to dump more fuel in the mix when it notices that the coolant is cold.
Once the coolant starts to warm up, this sensor will tell the computer to reduce the flow of gas and the air-to-fuel mixture will come close to the ideal number of 14.7:1. Which is 14.7 parts of air per 1 part of fuel.
Another component that is controlled by this sensor is the radiator fan. So, if the ECT sensor is stuck in a permanent hot or cold position, the radiator fan might start to work constantly, or not even kick in if is stuck in a cold setting. And the engine could potentially overheat because of this.
So, you get an idea of the ECT sensor function and why this sensor is really important for you. Now let’s move on and learn about the diagram.
ECT Sensor Diagram
So, we have covered the basics when it comes to the ECT sensor and we learned about the ECT sensor function. We think that now it is time to learn a little bit about the diagram of this sensor.
So, what is a diagram? Well, every electronic device has an electrical circuit. And so is the case with the ECT sensor. This sensor has wires that go to the sensor from the harness. And we need to learn more about these wires and what they mean. So, let’s take a look.
Usually, these sensors are either 2-pin or 4-pin. 2-pin sensors are the basic. While 4-pin sensors usually have 2 extra pins to send the temperature data to your dash, so you can visually see.
Nevertheless, these sensors work in a very simple fashion. They just report resistance. A cold sensor will report more resistance, for example, 3000 ohms, while a hot sensor will report little or no resistance. For example, 200 ohms. So, you get the idea.
Most of these sensors have 2 wires, one of them is the ground, while the other is the 5v signal wire. There is not much to it.
The important thing that you should know is the right resistance that your coolant temperature sensor should create. Not all sensors are rated the same. So, when it comes to diagnosing stuff, you should learn the right resistance for your specific make and model. But more on this later on in the article. Now as we cleared the ECT sensor function, let’s move on to other topics.
ECT Sensor Code
Now as we covered the ECT sensor function and we learned that this sensor has a task to check the coolant level temperature and help the engine adjust the A/F ratio, as well as to turn on the radiator fans. Let’s now move on and learn about this sensor and the codes that are associated with it.
The first code that is quite common with this sensor is the P0117 code which indicates a low circuit. Which most likely means that the sensor is stuck in a hot state.
The second code is more common and this is the P0118 code. This code is completely the opposite, meaning that the sensor reports rather high input. High resistance as you probably know is when the sensor records a cold reading of -40 degrees.
But what about the symptoms that are associated with this problem? Let’s elaborate more on them in the following chapters.
ECT Sensor Symptoms
Now as we covered the ECT sensor function, we can slowly move on and learn a bit about the symptoms that this sensor makes when it fails.
Symptoms may vary whether the sensor is stuck in a permanent hot or permanent cold state. So, let’s cover them really quickly before we learn more about how you can diagnose this component.
1. Check Engine Light
The first symptom on our list is the check engine light. We mentioned that the ECT sensor function is to inform the PCM about the temperature of the coolant.
So, if this sensor does not communicate in an expected manner with the PCM, you will get the check engine light.
The two most common codes concerning this symptom are codes P0117 and P0118. We elaborated more on them in the previous chapter. Now let’s move on to the next symptom.
2. Engine Overheating
So, we know the ECT sensor function, now let’s take a look at the second symptom that this sensor produces.
And this is the situation when your engine is overheating. So, why is this the case? Well, this is the case because, on long journeys, your fans will not kick in if your sensor has failed.
If the sensor is faulty, the fans will stay off. And if you go uphill, the engine could overheat because it does not have that extra cool air that the radiator fans are giving. So, you understand why the ECT sensor function is so important. Now let’s move on to the next symptom.
3. Temperature Gauge Faulty
The next symptom in our list since we covered the ECT sensor function is the malfunctioning of the temperature gauge.
As we noted, on some cars that have 4 pins, the temperature gauge really depends on this sensor. So, if the sensor is not working, the temperature gauge will stop working as well. So, it is really important that if you notice how the gauge isn’t working well, to test the sensor, just in case.
4. Trouble Starting
The next symptom on our list of bad ECT sensor symptoms is the situation when you have trouble starting the engine. So, why is this the case?
Well, this is the case because if the sensor’s resistance is too low and produces a constantly low signal. This means that it detects hot coolant and actually the coolant is really cold.
So, the computer will not know how much gas to put into the mix and in most cases, there will be very little gas. So, the engine could start and stall immediately or not even start at all. This is why this problem with starting the engine could mean that there is a problem with the ECT sensor. Learn the ECT sensor function and how to diagnose this component. And more on that, we are going to elaborate next.
5. Black Smoke From Exhaust
Now as we covered the first three symptoms and we learned the ECT sensor function, we can move on and learn more about the fourth most common symptom that this sensor produces.
This symptom is the black smoke from the exhaust. So, why this is the case? Why there is black smoke from the exhaust and a strong gas smell?
Well, this is the case because the sensor is helping the computer to adjust the air-to-fuel ratio. At each cold start, the sensor tells the computer that the coolant is cold and then the computer directs the injectors to dump more gas.
Once the coolant temperature is in the recommended range, the sensor resistance decreases to 200 ohms and goes into a hot state. In this case, the computer will reduce the fuel injected.
So, if the sensor is in a permanent cold condition, you will basically have an endless cycle of rich air to fuel mixture and the car will run poorly and will produce black smoke and gas odor constantly.
This could foul the spark plugs as well as the O2 sensor and the catalytic converter. So, you understand why the ECT sensor function is really important.
6. Poor Fuel Economy
And the last symptom in our list of symptoms of a bad ECT sensor is poor fuel economy. So, why is this the case, why poor fuel economy can mean that there is a problem with the ECT sensor?
Well, as we noted previously when this sensor fails in a cold state, the sensor will tell the computer to dump more fuel all the time and this will make the car run extremely rich.
So, consequently to this, the car will consume a lot more fuel than necessary. And the car will waste a ton of fuel more than needed. Your gas mileage could drop quite significantly because of this situation and you could end up in a serious problem. But how you can diagnose this problem? Let’s elaborate more on that next.
ECT Sensor Diagnosis
We learned the ECT sensor function and how this sensor works. Now let’s learn a little bit about the diagnosis and how you can diagnose this sensor.
For this purpose, you will need to grab a multimeter, a glass of water at ambient temperature, and a glass of boiling hot water.
Then you will tweak the multimeter to measure resistance. Then place the sensor in the ambient temperature water and wait for a few seconds. In this case, the resistance should be between 2000 and 3000 Ohms.
Next, place the sensor in boiling hot water. In this situation, the sensor output should drop to 200 to 300 ohms. So, you get an idea of how it is done, more on the process, you can check in the video that we attached.
ECT Sensor Replacement Cost
We learned the ECT sensor function and covered the symptoms that this sensor produces when it fails. Now let’s take a look at the costs that are involved in replacing this component.
The part is rather cheap and can be found for a price of $20 to $80 depending on the make and model.
The labor will cost you anywhere between $120 and $200. The labor is expensive because in most cases, you will have to diagnose the component with a multimeter. So, this diagnostics process is rather costly.
You can also replace it on your own in our garage. You only need one deep socket wrench or a ring spanner.
Conclusion
In this article, we covered quite a bit when it comes to the ECT sensor. First, we learned what this sensor is and what is the ECT sensor function.
Then we learned the symptoms of a bad coolant temperature sensor and learned more about what are the consequences of having a sensor in this condition. We noted the smoke of gasoline and increased fuel economy as one of the most common ones. Lastly, we learned how you can replace this component on your car and also at what cost is this possible.
