Coolant temperature sensors are used by the fuel management system to detect the engine's operating temperature. Depending on the sensor information, the control unit adapts the injection time and firing angle to the operating conditions. The sensor is a temperature sensor with a negative temperature coefficient. This means that the internal resistance reduces as the temperature increases.
The resistance of the temperature sensor changes depending on coolant temperature. As the temperature increases, the resistance is reduced, which reduces the voltage at the sensor. The control unit evaluates these voltage values, since they are directly related to the coolant temperature (low temperatures result in high voltage values at the sensor, and high temperatures result in low voltage values).