This video is going to be about the engine temperature sensor or engine coolant sensors. They are also called NTC sensors (Negative Temperature Coefficient Thermistor)
Im going to show you how to check this sensor in a simple way to avoid replacing it without being sure if he was really faulty

On the first part of this video I will perform a simple experiment to show you how a temperature sensor works: The concept is simple:
Put the sensor in water and track its resistance change as the temperature of the water raises.
The last part will be an exemple in how to check this sensor in a car.


Some facts about the NTC sensors:
- Used to track the temperature of the engine. its is a semi conductor which its resistance changes depending on the temperature.
- NTC resistors are also called thermistors, because their conductivity increases with increasing temperature and their resistance decreases respectively.
- For Petrol engines, the temperature of the engine is important to control the fuel injection and spark timing. Also it is very common that the ECU uses this sensor to control the cooling fan
That's why in some cases when this sensor is faulty the fan will run continuously as a protection routine launched by the ECU.
- For Diesel engine the signal of these sensors is important to control the heating time of the glowplugs, the injection system control and the exhaust gases recirculation. When the temperature sensor fails
it is possible that the ECU will use some saved values or uses the signal of the diesel temperature sensor.

The main known symptoms of a bad engine temperature sensors are:
- Engine wont start or starts very hard
- Bad fuel economy
- Poor engine performance
- Engine overheating
- Irregular Temperature Readings
- Emission control fail
- and of course the famous Check engine light

The linked faulty codes of a bad Temperature sensor:

P0115
P0116
P0117
P0118
P0119

It is not necessary to measure the temperature of the coolant or to remove the sensor to test it, all you need to do is to check its when the engine is still cold and another time when the engine has reached its working temperature.

Typical values of the resistance for a corresponding coolant temperature:
7000 - 12000 Ohms at -10°C
2000 - 3000 Ohms at 20°C
700 - 1000 Ohms at 50°C
240 - 450 Ohms at 80°C
Before measuring the resistance of the sensor, check if the sensor is getting the 5V supply from the ECU.
In this video this particular temperature sensor is installed on a 2004 BMW e46 320i

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