Electric Cooling Fan

The PCM  determines when to operate the electric cooling fan from the engine coolant temperature sensor input and a electric cooling fan request from the HVAC Control Module. The PCM  also adjusts the electric cooling fan speed to compensate the ram effect of vehicle speed.

The PCM  varies the duty cycle of the Pulse Width Modulation (PWM) signal to the engine cooling fan control module between 0 and 100%. This operates the electric cooling fan motor in one of four modes:

• Off
• Minimum speed - 750 Revolutions Per Minute (RPM)
• Linear variable speed between minimum and maximum speeds
• Maximum speed - 2, 820 RPM  .

Under hot operating conditions, the electric cooling fan may continue to operate for up to five minutes after the engine has been switched off.

The engine cooling fan control module monitors for over and under input voltage, a stalled motor and a partially stalled motor. In case of any faults detected, the engine cooling fan control module temporarily pulls the PWM signal to ground. This notifies the PCM  about the fault. The length of time the PWM signal is pulled to ground varies between two and eight seconds, depending on the fault. The engine 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  .

The fault priorities in descending order are the following:

• Over voltage
• Under voltage
• Stalled motor
• Partially stalled motor.

The PCM  records a related Diagnostic Trouble Code(s) (DTC) for faults notified by the engine cooling fan control module and signals the BCM  /GWM  through the FlexRay bus. The BCM  /GWM  transmits the signal on the HS CAN  comfort systems bus to the IC to display a warning message.

The nominal operating voltage for the electric cooling fan is from 9 V to 16 V. If the input voltage is outside of these limits, the engine cooling fan control module stops operation of the electric cooling fan. In addition it notifies the PCM  of the fault. After an under or over voltage occurs, the electric cooling fan operation is resumed when the input voltage increases to 9.5 V, or decreases to 15.5 V, respectively.

Each time, two seconds after the power to start the electric cooling fan is supplied, the engine cooling fan control module checks the electric cooling fan motor speed. If the speed is zero, the engine cooling fan control module determines the electric cooling fan motor is stalled and tries a restart. For a restart, the engine cooling fan control module disconnects the power from the electric cooling fan motor then immediately reconnects it at an increased current level. The engine cooling fan control module will try up to six restarts of a stalled motor, increasing the output current each time. If the electric cooling fan motor remains stalled after the sixth restart, the engine cooling fan control module waits 40 seconds. Afterwards it notifies the PCM  of the fault and begins the start process again.

To check for a partially stalled motor, while the electric cooling fan is running the engine cooling fan control module monitors the current draw against electric cooling fan speed. If the current draw is over the limit for more than 10 seconds, the engine cooling fan control module disconnects the power from the electric cooling fan motor. Afterwards it notifies the PCM  of the fault. After 40 seconds, the engine cooling fan control module starts the motor again.

The engine cooling fan control module incorporates a temperature sensor to prevent damage caused by excessive heat at high ambient temperatures. Operation of the engine cooling fan control module is discontinued if the temperature reaches 135°C (275°F). Operation resumes when the temperature decreases to 120°C (248°F).

If a fault occurs with the ignition signal or the PWM signal, the engine cooling fan control module adopts the following fan speeds: