ECT: The scan tool displays -39°C to +140°C (-38°F to +284°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 it 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.

Monitored Coolant Temp: The scan tool displays the coolant temperature data as provided to the instrument panel cluster (IPC) via the class 2 serial data link.