Engine Coolant Temperature (ECT) Sensor

ECT sensor is installed on thermostat housing. It provides a variable signal to PCM that is used to calculate injector pulse width and ignition timing. When engine is cold, PCM will operate engine in an open loop cycle, causing slightly richer air/fuel mixture and higher idle speeds. When normal operating temperatures are reached, PCM will operate engine in a closed loop cycle. See MODES OF OPERATION under FUEL CONTROL  .