Damage to the temperature sensor – how to handle it?

The ECU engine operating computer needs a number of data, taken from the sensors. One of them is the coolant temperature sensor, also known as the engine temperature sensor. What are the symptoms of its failure? How should I remove the car engine temperature sensor that malfunction?

In older cars, the engine temperature sensor was also mounted or, if you prefer, a coolant temperature sensor. The sensor has a warning function. When the water or coolant circulating in the system start to boil, the sensor caused the red indicator light on the dashboard (instrument cluster). It happened so often if there was very little liquid (water) in the system or if it leaked.

The sensor is mounted in the engine head or on one of the refrigerant lines.

In modern constructions, the role of the engine temperature sensor is much higher. Data from the sensor, which constantly monitors the temperature of the coolant, is sent to the computer controlling the operation of the drive unit on an ongoing basis. They are needed for calculations related to the duration of fuel injection, the moment of ignition or setting the engine speed at idle. The injection time with a cold engine is different (it time to worm up and require more fuel, and the other with the engine warmed up, working at the operating temperature (requires lower fuel). Data on the engine temperature (and more precisely on the temperature of the coolant) are also necessary for setting the throttle. A proper working engine temperature sensor allows optimal selection of fuel-air mixture,

That’s why the failure of the engine temperature sensor causes a number of problems with the daily operation of the car.

What does the engine temperature sensor look like?

This is a small device with a height of a few centimeters. The lower part contains a sensor that is immersed in the coolant. Above there is a thread that allows the sensor to be attached. At the very end, there is a socket to which the cable leading to the ECU computer is connected.

How does the engine temperature sensor work?

There are two types of engine temperature sensors – NTC and PTC. How does the NTC (negative temperature coefficient) sensor work? The higher the temperature of the coolant, the lower the resistance of the sensor and the smaller the voltage drop. In the PTC (positive temperature coefficient) sensor, the opposite is true – the higher the temperature of the refrigerant fluid, the higher the resistance of the sensor and the greater the voltage drop. The voltage value on the sensor allows the ECU computer to calculate the coolant temperature.

What are the symptoms of a vehicle temperature sensor failure?

If the engine temperature sensor fails, you can expect many problems that will significantly hinder the daily operation of the car.

The sensor may be subject to wear, as well as mechanical damage during repair. But there are also situations where the sensor itself is functional, but the power supply to the sensor is interrupted. The plug that supplies electricity to the sensor may also be damaged, and its contacts may have been damaged. There may also be a short circuit in the sensor.

The computer controlling the operation of the drive unit does not receive data from the sensor, therefore the control of the engine operation takes place in the emergency mode, using replacement data.

What are the symptoms of sensor failure? These are difficulties with starting a warm engine, clearly higher fuel consumption, uneven operation of the drive unit, as well as its extinguishing (stop working) while driving. At idling speed, the engine has significantly higher revolutions. The car also emits more carbon monoxide because the lambda probe is not able to properly adjust the composition of the fuel-air mixture.

The symptom of the sensor failure is also improper operation or complete lack of operation of the engine temperature indicator on the dashboard.

How to make sure (diagnose) that the engine temperature sensor has failed?

In the first phase, read any errors stored in the ECU computer’s memory using car diagnostic equipment.

First of all, you need to carefully check the condition of the wires leading to the temperature sensor for damage to insulation, cracks, and interruptions – for this purpose a standard universal meter is suitable. Check the status of the plug. You also need to check whether there is no corrosion on the plug and the sensor itself.

Repair of a damaged engine temperature sensor

The engine temperature sensor (coolant temperature sensor) is a non-removable and non-recoverable part. Repair (insulate or replace with a new one) only the electric wire that supplies power to the sensor.

When replacing the engine temperature sensor, it will be necessary to refill the refrigerant (radiator) fluid, as some of it will spill out of the system. Thus, you can immediately connect the sensor exchange with a new refrigerant (radiator) fluid.

If the sensor is mounted on the refrigerant line, it is worth checking its condition. Any signs of aging rubber (tarnished, cracked) should induce the car owner to purchase new refrigeration hoses and replace them.

In most cases, the engine temperature sensor is mounted using a gasket. When installing a new sensor it is necessary to replace it with a new one.

Of course, the repairs are done with a cold engine. First, disconnect the plug from the wire that connects the sensor to the ECU computer. Then, using the appropriate key (tools), unscrew the sensor. After removing the sensor from the system, a large amount of coolant will flow out. After installing the new sensor and possibly its new seal, the fluid level must be topped up (or replaced completely) and the cooling system vented.

It is worth remembering that driving with a damaged engine temperature sensor is dangerous. It’s not just problems with everyday car operation. It is also the risk of overheating the engine in case of failure of the refrigeration system components (cable breaks, fluid leakage from the radiator, too little fluid, fan failure while standing in the traffic jam). Overheating can lead to the galling and complete destruction of the drive unit.

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