ECT: The scan tool displays -40 to +151°C (-40 to +304°F). The engine coolant temperature (ECT) sensor is mounted in the coolant stream. The powertrain control module (PCM) or engine control module (ECM) 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 or ECM monitors a high signal voltage and interprets it as a cold engine. As the sensor warms and internal resistance decreases, the voltage signal decreases and the PCM or ECM interprets the lower voltage as a warm engine.

Engine Coolant Fan: The scan tool displays OFF and ON. When the scan tool displays FC Relay 1 Commanded, the PCM or ECM is commanding the cool fan 1 relay ON. When the PCM or ECM commands the cool fan 1 relay ON, the left cooling fan is enabled in low speed. When the scan tool displays FC Relay 2 and 3 Commanded, the PCM or ECM is commanding the cool fan 1, cool fan 2, and S/P fan relays ON. When the cool fan 1, cool fan 2, and S/P fan relays are ON, the left and right cooling fans are enabled in high speed. When all fan relays are activated, the left and right cooling fans are enabled in high speed.