Radiator Cooling Fan Control Module: Description and Operation

ENGINE CONTROL COMPONENTS

Cooling Fan Control
The PCM monitors certain parameters (such as engine coolant temperature, vehicle speed, A/C ON/OFF status, A/C pressure) to determine engine cooling fan needs.

For variable speed electric fan(s):

The PCM controls the fan speed and operation using a duty cycle output on the fan control variable (FCV) circuit. The fan controller (located at or integral to the engine cooling fan assembly) receives the FCV command and operates the cooling fan at the speed requested (by varying the power applied to the fan motor).

The fan controller has the capability to detect certain failure modes within the fan motors. Under certain failure modes, such as a motor that is drawing excessive current, the fan controller shuts OFF the fans. Fan motor concerns may not set a specific DTC. With the fan motor disconnected from the fan controller, voltage may not be present at the fan controller.






For relay controlled fans:

The PCM controls the fan operation through the fan control (FC), (single speed fan applications), low fan control (LFC) and high fan control (HFC) outputs. Some applications have the xFC circuit wired to 2 separate relays.

For 2-speed fans, although the PCM output circuits are called low and high fan control, cooling fan speed is controlled by a combination of these outputs. Refer to the following tables.