Scan Tool Data Definitions

Scan Tool Data Definitions
ECT: The 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 Engine Control Module (ECM) applies 5 volts to the ECT sensor signal circuit. The sensor is a thermistor which changes internal resistance as temperature changes. When the sensor is cold and the internal resistance is high, the ECM monitors a high signal voltage and interprets it as a cold engine. As the sensor warms and the internal resistance decreases, the voltage signal decreases and the ECM interprets the lower voltage as a warm engine.
Cooling Fan Relay Command: The cooling fan relay is commanded ON or OFF by the ECM.
Low Coolant Level: The scan tool displays YES or NO, determined by the state of the low coolant level switch.