Scan Tool Testing and Procedures

Scan Tool Data Definitions

Cooling Fan Command
- The percent of engine cooling fan requested from the ECM.

Desired Fan Speed
- Requested fan speed from the ECM.

ECT Sensor
- 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 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 and internal resistance is high, the PCM 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 interprets the lower voltage as a warm engine.

Fan Speed
- Actual fan speed.