Engine Cooling Fan Control Module

Each electric cooling fan is operated by a control module, integrated into their electric motor, which is controlled by the Powertrain Control Module (PCM).

The PCM determines when to operate the cooling fan from the Engine Coolant Temperature (ECT) sensors input and/or a cooling fan request from the Automatic Temperature Control Module (ATCM). The PCM also adjusts the fan speed to compensate for the ram effect of vehicle speed.

The control module of each electric cooling fan is provided with:

• A battery power supply from the Auxiliary Junction Box (AJB)
• An ignition signal from the PCM relay in the Engine Junction Box (EJB)
• A Pulse Width Modulation (PWM) signal from the PCM
• A ground.

The cooling fan control module monitors for over and under input voltage, a stalled motor and a partially stalled motor. If it detects any of these faults the cooling fan control module temporarily pulls the PWM signal to ground to notify the fault to the PCM. The length of time the PWM signal is pulled to ground varies between two and eight seconds, depending on the fault. The cooling fan control module repeats the notification process at five second intervals until the fault is cleared. If there is more than one fault, only the highest priority fault is notified to the PCM. Fault priorities, in descending order, are over voltage, under voltage, stalled motor and partially stalled motor. The PCM records a related Diagnostic Trouble Code (DTC) for faults notified by the fan control module and signals the Instrument Cluster (IC) on the High Speed (HS) Controller Area Network (CAN) comfort systems bus to display a warning message. For additional information, refer to: ENGINE COOLING