Coolant Temperature Sensor/Switch (For Computer): Description and Operation

Coolant Temperature Sensor:

The engine coolant temperature sensor is a thermistor that is located in the engine coolant flow. When the coolant temperature is low, the sensor produces a high resistance. When the coolant temperature is high, the sensor produces a low resistance.

The ECM/PCM sends a 5 volt signal to the coolant temperature sensor through a resistor in the computer and measures the voltage. The voltage will be high or low depending on coolant temperature. By varying the voltage the computer will sense engine coolant temperature.