Scan Tool Data Definitions

Scan Tool Data Definitions
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 Engine Control Module (ECM) or Powertrain Control Module (PCM) 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/PCM 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/PCM interprets the lower voltage as a warm engine.
Fan Control 1, Fan Control 2 Command: The cooling fan relay is commanded ON or OFF by the ECM/PCM.
Low Coolant Level, Switch Inputs: The scan tool displays YES or NO, determined by the state of the low coolant level switch.