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

Coolant Temperature Sensor:

The coolant sensor is a thermistor (a resistor which varies its resistance value based on temperature) mounted in the engine coolant stream. The coolant sensor is a two wire component which receives a reference voltage signal from the ECM. Low coolant temperature produces a high resistance, while a high temperature produces low resistance. The ECM supplies a voltage signal to the coolant sensor through a resistor in the ECM and measures the signal voltage output. The voltage will be high when the engine is cold, and the voltage will be low when the engine is hot.



The sensor provides coolant temperature information to the ECM for fuel enrichment, ignition timing, EGR operation, canister purge control, air management, idle speed control, and closed loop fuel control. A failure in the coolant sensor circuit should set either a code E014 or code E015.