Engine Coolant Temperature (ECT) Sensor
WARNING: This page is about a different car, the 1995 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.
Threaded into coolant passage near thermostat housing, ECT sensor inputs coolant temperature to PCM. The signal from ECT affects air/fuel ratio, idle speed, EGR flow, purge flow, fuel pressure and ignition timing output signal from PCM.