ECT

The scan tool range is -40°C to 120°C (-40°F to 250°F): The ECT sensor is a thermistor. The PCM monitors the voltage on the ECT sensor signal circuit. When the ECT sensor is cold (internal resistance high), the PCM sees a high signal voltage. The signal voltage and the internal resistance of the sensor decrease as the engine becomes warm. The scan tool displays default values of -40°C or -40°F when there is an open in the ECT sensor signal circuit.