Coolant Temperature Sensor
The engine coolant temperature sensor is used to detect the engine coolant temperature. The sensor modifies a voltage signal from the Engine Control Module (ECM). The modified signal returns to the ECM as the engine coolant temperature input. The sensor uses a thermistor that is sensitive to the change in temperature. On most temperature sensors, the electrical resistance of the thermistor decreases as temperature increases. Coolant temperature sensor resistance varies with the make and model of the vehicles.
A faulty coolant temperature sensor will send an improper signal to the ECM, which may cause the engine to overheat and/or trigger the engine light to come ON.