Theory Of Operation
WARNING: This page is about a different car, the 2014 Dodge Journey. However, it is still accessible from the selected car via links, so may be relevant.
The Engine Coolant Temperature (ECT) Sensor is a variable resistor that measures the temperature of the engine coolant. The Powertrain Control Module (PCM) supplies 5 Volts to the ECT Signal circuit and supplies a ground to the low reference circuit.