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

Engine Coolant Temperature Sensor:

PURPOSE
The Engine Coolant Temperature (ECT) Sensor is used to control:
^ Fuel delivery
^ Engine Spark Timing (IC)
^ Idle Air Control (IAC)
^ Cooling Fan
^ Controlled Canister Purge (CCP)
^ Torque Converter Clutch (TCC)

LOCATION
Engine thermostat and coolant outlet.

OPERATION
The ECT 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 PCM sends a 5.0 volt signal to the ECT 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.