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

The coolant sensor is a thermistor mounted in the engine coolant flow. The ECM supplies a 5 volt signal to the coolant sensor through a resistor in the ECM and measures voltage. Voltage will be high when engine is cold and low when engine is hot. The sensor provides coolant temperature information to the ECM for ignition timing, fuel enrichment, canister purge control, EGR operation, EFE operation, air management, closed loop fuel control and idle speed control.