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

Engine Coolant Temperature Sensor:

PURPOSE
The Engine Coolant Temperature sensor (ECT) is used to control:

^ Fuel delivery
^ Torque Converter Clutch (TCC)
^ Engine Spark Timing (EST)
^ Controlled Canister Purge (CCP)
^ Idle Air Control (IAC)
^ Cooling Fan
^ Temperature Gauge on Dash.

OPERATION
The ECT 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 ECM 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 ECM can sense engine coolant temperature by reading the varying voltage.

The ECT also contains a separate thermistor circuit that controls the temperature gauge in the dash.

LOCATION
Engine thermostat and coolant outlet.