2.0L/2.4L Engine
WARNING: This page is about a different car, the 2005 Dodge Stratus and 2005 Chrysler Sebring. However, it is still accessible from the selected car via links, so may be relevant.
The Engine Coolant Temperature (ECT) Sensor threads into the thermostat housing just below the coolant outlet connector. See Figure. The ECT Sensor is a negative thermal coefficient sensor.