Engine Coolant Temperature (ECT) Sensor
WARNING: This page is about a different car, the 1995 Lincoln Mark VIII. However, it is still accessible from the selected car via links, so may be relevant.
ECT sensor inputs coolant temperature to the PCM. ECT sensor is threaded into heater outlet fitting or coolant passage. The ECT sensor changes resistance in response to coolant temperature. The ECT sensor resistance decreases as coolant temperature increases. On models with an electronic instrument cluster, an additional ECT is used as a coolant temperature indicator.