ECT

The scan tool range is -40°C to 120°C (-40°F to 250°F). The ECT sensor is a thermistor which changes internal resistance as the temperature changes. When the sensor is cold (internal resistance high), the PCM monitors a high signal voltage and interprets the voltage as a cold engine. As the sensor warms (internal resistance decreases), the voltage signal decreases and the PCM interprets the lower voltage as a warm engine.