Visctronic Drive Fan (VDF)
WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 2004 Ford RV Cutaway, 2004 Ford Pickup, 2004 Ford F550 Super Duty, 2004 Ford F450 Super Duty, and 2004 Ford Excursion. However, it is still accessible from the selected car via links, so may be relevant.
The cooling fan electronic clutch is controlled by the PCM. The PCM monitors engine oil temperature (EOT) and engine coolant temperature (ECT) and sends a duty cycle command to the fan clutch to achieve adequate cooling. When a circuit fault is detected the PCM will set a DTC.