Scan Tool Data Definitions

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Desired Fan Speed: This parameter indicates the desired cooling fan speed in RPM. This value is determined by engine load, temperature, and speed.
Displayed Coolant Temperature - Range: 32-127°C (89-260°F): This data is the coolant temperature the Instrument Cluster is attempting to display on the coolant temperature gauge. This data may differ from the monitored coolant temperature for a period of time due to filtering. The data may also differ from the monitored coolant temperature when coolant temperature is not in the range of 71-127°C (160-260°F) since the display is limited to these values. If a Class 2 communication failure occurs, this data will be at the minimum value of 32°C (89°F).
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: This parameter indicates the actual speed of the cooling fan in RPM.
IAT Sensor: The scan tool displays -40°C to 151°C (-40°F to 304°F). The PCM converts the signal of the IAT sensor into degrees. The PCM uses the IAT in order to adjust fuel delivery, spark timing, and cooling fan speed according to the incoming air temperature.
Monitored Coolant Temperature - Range: 40-215°C (40-419°F): This data is the clusters measurement of the engine coolant temperature as provided by the PCM on the Class 2 serial data line.