In order to be able to check the operating temperature of the engine, there is the Coolant Temperature Sensor. The control unit can adapt the injection time and the ignition angle to the temperature of the engine. As the temperature increases, the internal resistance changes. Depending on whether the coolant temperature is rising or falling, the resistance of the temperature sensor will also vary. For example, if the temperature increases, then the resistance also decreases, which in turn reduces the voltage at the sensor. The controller is now able to read this.
This clearly shows how important such a coolant temperature sensor is. If there are defects in this component, they should be identified as quickly as possible and then rectified. An error detection on the control unit is designed to draw attention to indications of defects. But there are other symptoms that a driver will quickly notice and indicate problems with said component. Examples would be an increased idle speed and increased fuel consumption. But a difficult starting of the engine can also be a sign.
But there are also other situations in which problems with this sensor could become noticeable. If, for example, the AU is pending and increased CO2 values are measured, this should also be a warning.
What can you do to get to the bottom of the errors? So how is troubleshooting done at this point? We would like to go into more detail on these questions and some other information below.
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Why exactly is the coolant temperature sensor so important for the vehicle?
In order to keep the exhaust emissions as low as possible and the efficiency in the optimum range, it is important that the temperature of the engine is also within the normal range. The coolant temperature sensor is there to provide reliable values in this regard. The temperature of the cooling water is therefore constantly measured in order to be able to prevent the engine from overheating. Depending on the determined values, the injection quantity is then also adjusted precisely. In most cases, only one of these components is installed in each vehicle. But nowadays there are also vehicles that have two of these parts so that the second part can check the correctness of the values of the first part.
How exactly does the troubleshooting take place?
To be sure that something is wrong with the coolant temperature sensor, you should first troubleshoot it. How exactly do you do this? First you have to have the fault memory read out. In addition, the connections of the lines, as well as the sensor and the plug should be checked for a closed connection, as well as possible cracks or corrosion. The check must be carried out at this point with the multimeter. First the internal resistance should be determined. If the engine is cold, said resistance should show a high ohm value, if the engine is warm, the ohm value is in a low range. Now you have to carefully inspect the wiring to the control unit. Pay close attention to checking each line to the control unit connector for continuity. Finally, the supply voltage must be tested. You can do this with the voltmeter on the disconnected sensor connector. The ignition must be switched on at this point. Ensure that the correct voltage values are achieved. If this value cannot be reached, the voltage supply on the control unit must be checked according to the circuit diagram. The control unit may be defective if no errors are found in the power supply.
Can the coolant temperature sensor be replaced or repaired?
At this point, repairing the component is out of the question. So you should have the component replaced or dare to do the process yourself. In any case, make sure that you do not purchase any used components for replacement. Only high quality and new parts are recommended here. How complex the change ultimately turns out to be depends heavily on the car model and its construction. But all processes have in common that the bonnet has to be opened first. Depending on how said component has been installed, other units or components must still be removed. Once you can see and reach the coolant temperature sensor, the replacement is as good as done. However, you should only dare to do such DIY work if you have some basic knowledge and experience. If this is not the case, you should not perform the process yourself. Then it is better to turn to trained and competent specialists from a workshop. They will be happy to help you and you can rest assured that the work will be carried out professionally.
If you carry out the replacement yourself, you have to reckon with material costs of 30 to 70 euros. Be careful not to buy cheap brands. It is better to focus on well-known manufacturers such as Bosch, Hella and Valeo. However, if you have the change carried out in a workshop, you must of course also take into account the hourly wages of the specialist staff. Since the process takes about half an hour to an hour, you can expect total costs of up to 150 euros at most. At least that's what the average experience shows.
The conclusion and a tip from CarTipsandmore
Ultimately, it can be said that the coolant temperature sensor is one of the most important sensors in a car. The component in question is responsible for permanently recording the temperature of the cooling water and for sounding an alarm in the event of overheating. In addition, the values of said components are decisive for the injection quantity that will take place. Signs of a defect are usually increased fuel consumption and a poor start of the vehicle, as well as a failed main inspection due to excessively high exhaust gas values, an incorrect function of the automatic start-stop system, or the engine being switched off while driving. If any of these signs sound familiar, you should have the coolant temperature sensor inspected by competent professionals at a workshop as soon as possible. Replacing the defective part takes no more than an hour and doesn't cost much. If you have the necessary basic knowledge and some technical skills, you can even replace the component yourself and save a lot of money. The decision is yours. In some cases, however, the fault is not with the said sensor, but with a faulty thermostat.
In any case, CarTipsandmore strongly advises you at this point not to continue driving with a faulty coolant temperature sensor. Because this could result in expensive engine damage due to severe overheating of the engine.