Engine Coolant Temp Sensor: Description
WARNING: This page is about a different car, the 2004 Dodge Sprinter. However, it is still accessible from the selected car via links, so may be relevant.
The ECM determines the operating temperature of the engine by using the signal from the coolant temperature sensor. The coolant temperature sensor has a negative temperature coefficient (NTC) resistor contained in the plastic housing. NTC means; the higher the temperature, then the lower the resistance. The ECM also uses the coolant temperature sensor signal to calculate glow plug relay triggering. If the coolant temperature sensor fails during operation, the ECM will switch on the cooling fan to prevent engine overheating (A/C models only).