ECT

Scan Tool Displays -40°C to 151°C (-40°F to 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 Internal resistance as temperature changes. When the sensor is cold (Internal resistance high), the PCM monitors a high signal voltage and Interprets the data 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.