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

Engine Coolant Temperature (ECT) sensor:

PURPOSE
The Engine Coolant Temperature Sensor (ECT) is one of the primary signals that the Engine Control Module (ECM) uses to determine proper fuel injector duration. By measuring the amount of resistance at the sensor, which is located in a cylinder head coolant passage, just below the distributor, the ECM can adjust the length of injector opening time (duration) required by the engine.

OPERATION
As water temperature increases, sensor resistance decreases. The ECM receives sensor information as return voltage at ECM terminal D22 (GRN/WHT).

CONSTRUCTION
The ECT is a temperature sensitive resistor (thermistor) which changes it's resistance as it's temperature changes.