Engine Coolant Temperature Sensor
WARNING: This page is about a different car, the 2009 Jeep Liberty. However, it is still accessible from the selected car via links, so may be relevant.
The Engine Coolant Temperature (ECT) sensor is used to sense engine coolant temperature. The sensor protrudes into an engine water jacket.
The ECT sensor is a two-wire Negative Thermal Coefficient (NTC) sensor. Meaning, as engine coolant temperature increases, resistance (voltage) in the sensor decreases. As temperature decreases, resistance (voltage) in the sensor increases.