ECT

Scan tool displays -40°C - +151°C (-40°F - +304°F). The Engine Coolant Temperature (ECT) sensor is mounted in the coolant stream. The PCM applies 5 volts to the ECT sensor circuit. The sensor is a thermistor which changes the internal resistance as the temperature changes. When the sensor is cold and the internal resistance is high, the PCM monitors a high signal voltage and interprets it as a cold engine. As the sensor warms and the internal resistance decreases, the voltage signal decreases and the PCM interprets the lower voltage as a warm engine.