Engine Coolant Temperature Sensor
WARNING: This page is about a different car, the 2002 Mercury Villager. However, it is still accessible from the selected car via links, so may be relevant.
Sensor signals Engine Coolant Temperature (ECT) to PCM. The ECT sensor changes resistance in response to coolant temperature. The ECT sensor resistance decreases as coolant temperature increases. The PCM uses ECT sensor signal to adjust ignition timing, EGR flow, air/fuel ratio, idle speed, A/C and cooling fan operation.