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

Engine Coolant Temperature Sensor:

The engine Coolant Temperature Sensor (CTS) is a thermistor with a negative temperature coefficient (change in resistance is inversely proportional to the change in temperature.) When the coolant temperature is low, the sensor resistance is high. When the coolant temperature is high, the sensor resistance is low. Each resistance value correlates to a specific engine coolant temperature. The ECM/PCM measures the resistance and calculates the engine temperature.