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

Engine Coolant Temperature Sensor:

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

OPERATION
The ECT is a thermistor that is located in the engine coolant flow mounted to the intake manifold. 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 control module sends a 5.0 volt signal to the ECT through a resistor in the computer and measures the voltage. The voltage will be high or low depending on coolant temperature. With the ECT varying its resistance, the control module can sense engine coolant temperature by reading the varying voltage.