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

Engine Coolant Temperature (ECT) Sensor:

PURPOSE
The Engine Coolant Temperature (ECT) sensor measures varying engine coolant operating temperatures, providing the information to the Powertrain Control Module (PCM). The ECT signal is used to modify ignition timing, EGR flow and air/fuel mixture.

OPERATION
The varying temperature, and thus varying resistance, affects the voltage drop across the sensor terminals, providing electrical signals to the PCM.

CONSTRUCTION
The ECT is a thermistor device in which resistance decreases as the temperature increases, and increases as the temperature decreases. Thermistor-type sensors are considered passive sensors. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in total current flow.