how to tell if your coolant temp sensor is bad

How to tell if your coolant temp sensor is bad? Well, there are a few primary symptoms that most of you can identify the issue.

Engine coolant temperature sensor is an essential component in all vehicles to optimum the driving capability. Its primary duty is to measure the temperature in the engine coolant. Then engine control module adjusts the rest of the relative activities at the optimum level. Because the air-fuel mixing depends on the temperature of the engine coolant.

What are the terrible coolant temperature sensor symptoms?

The most famous symptom is the check engine light. But engine light signal may occur due to several other reasons also. So, we thought to bring you exact symptoms on a bad coolant temp sensor.

01. Check engine light

As we discussed, this is the primary first system that you can see on the dashboard. Every vehicle obtains a computer unit related to all sensors in the engine. If there is any sensor circuit issue, this computer unit is able to inform you by illuminating the engine light. And the illuminated light will stay remain until the problem is repaired. Therefore, if you see this light, go for an experienced technician to fix the issue. Engine check light may depend on different other issues of the engine, including Oxygen sensor failures.

engine check light
Engine check light – Photo by Wikiuser100000, CC BY-SA 3.0, via Wikimedia Commons

02. Low fuel economy of the car

As you know, air-fuel mixing is related to the coolant temperature of the engine. But if the sensor could not inform the temperature of the coolant correctly, this air-fuel mixing will not proceed correctly. For example, suppose your engine coolant temperature sensor provides a piece of fault information like the engine is in cold condition. But actually, it is not. Then more fuel amount is going to be burned to heat the engine quickly. In reality, it is a waste, and the engine does not need such fuel burning to heat. Finally, you will experience an unexpected fuel loss in the car.

03. Inactivation of the electrical cooling fans

Only some vehicles have this ability. They are using an engine coolant temp sensor to control electrical cooling fans. So, once the sensor goes out of work, you cannot take advantage of activating the fans using the sensors.

04. Black smoke emission

All the time, black smoke emission from the exhaust pipe indicates engine trouble. That black smoke emits because of the improper fuel burning in the engine. As we discussed earlier if the sensor goes down engine cannot monitor the internal temperature. It causes improper fuel burning. So, you will experience black smoke coming from the exhaust pipe.

05. Difficulty in starting the engine

Because of the imperfect fuel burning, there can be fuel deficiencies in the engine. At those points, the vehicle starts, maybe not occurring. Finally, you will have difficulties when starting.

06. Overheat the vehicle

As mentioned earlier, in some vehicles, the fan control is on the hands of the coolant temperature sensor. At those times, if the sensor is down, the fans do not activate. It leads to overheating the vehicle’s engine. Because fans do not receive proper signals. Luckily some cars have a separate sensor for fans. But majority obtain the same sensor.

07. Lower Idling

Due to the fault signals of the coolant temperature sensor, there are frequent fuel-burning imbalances. So, at lower speeds, the engine will tend to stop immediately. Also, some power losses and strange behaviors on the road. Finally, you will experience non-steady driving frequently.

What does a coolant temperature sensor do?

The primary responsibility of the coolant temperature sensor is the maintaining of fuel management. For that, it gets information about the engine’s operating temperature. Depending on the report of the sensor, the engine computer control unit takes decisions.

The control unit adapts the fuel injection time and firing angles. When the temperature of the engine goes up, the control unit reduces the circuit resistance. Then voltage becomes increases. The control unit evaluates the changes of the voltage that are directly related to the temperature.

Depending on the voltage differences, it may change the signal. Then fuel burning will adjust accordingly.

Engine coolant temperature sensor location

This is an interesting point, especially for those who are new to car mechanisms. It is usually situated in the engine block or cylinder head. It usually installs on the plastic host at the inlet of the coolant. But the actual position depends on the car design. Different brands obtain different places for the sensor.

Some cars include more than one sensor. Then you will have separate sensors on signaling to the dashboard, control the cooling fan, and engine control unit.

Coolant temperature sensor testing

When you suspect your coolant temperature sensor goes wrong, you can test on it.

–         Locate the sensor: First, you need to locate the exact place. As mentioned previously, the area can be different from vehicle to vehicle. Basically, it is in the engine block.

–         Connect the ohmmeter: Testing the sensor is a quick process. According to the above text, the sensor may show different voltages. Ohmmeter provides the resistivity readings concerning the voltages. Connect it properly and set the reading to the range of 20K.

–         Take readings: Now turn on the vehicle’s engine. Let the engine run for a minimum of 2 minutes to heat the engine. Now you can see the changes in the reading with ohms. If you see a reading difference of 200ohms, you need to replace the sensor. Which means the sensor got damaged?

Coolant temp sensor changing is an easy process. But it would help if you considered a few facts before changing. Also, you will need a proper toolset. So, it is better to go for a technician to replace it.

Coolant temperature sensor price

This cost varies according to the brand of the vehicle. Usually, a new coolant temperature sensor costs $30 to $100. But you need to pay attention to the labor cost also. Labor costs may take approximately $20 to $150.

As the text mentions, you might wonder why this is so costly if the process is quick. The thing is, according to your vehicle and your choice of technician, it may take time and experience.

Finally, you may have an idea of how the sensor will affect the car’s driving capabilities. You cannot drive more with an issue with the sensor at all. Also, neglecting the problem will result in critical damages to the rest of the engine functions. Also, will cause substantial costly replacements. So, identify the issue at the initial point and replace the sensor if needed.


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