Electric Cooling Fan

The Powertrain Control Module (PCM) receive signals from the engine coolant temperature sensor and the HVAC control module (HVAC). Then the PCM determines when to operate the electric cooling fan. The PCM also adjusts the electric cooling fan demand to compensate for 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%. The logic from PCM operates the electric cooling fan motor in 1 of 4 modes:

• Off.
• Minimum speed.
• Linear variable speed between minimum and maximum speeds.
• Maximum speed.

In hot operating conditions, the electric cooling fan may continue to operate for up to 5 minutes after the engine has been switched off.

The electric 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 electric cooling fan control module temporarily connects the PWM signal to ground. The length of time the PWM signal connected to ground varies between 2 and 8 seconds, depending on the fault. The electric cooling fan control module repeats the notification process at 5 second intervals until the fault is cleared. When there is more than 1 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 (DTC) for faults notified by the engine cooling fan control module. The PCM signals the BCM  through the Flexray. The BCM/GWM transmits the signal to the Instrument Panel Cluster (IPC) to display a warning message.

The signal goes through the HS CAN  Human Machine Interface (HMI) systems bus.

The nominal operating voltage for the electric cooling fan is from 9V to 16V. When the input voltage is outside of the limits, the engine cooling fan control module stops operation of the electric cooling fan. In addition the electric cooling fan control module notifies the PCM of the fault. The electric cooling fan operation resumes when the input voltage increases to 9.5V, or decreases to 15.5V, respectively.

The electric cooling fan control module checks the electric cooling fan motor speed in each 2 seconds after the fan is energized. If the speed is 0, the electric 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 the engine cooling fan control module immediately reconnects the power at an increased current level.

The electric cooling fan control module tries up to 6 restarts of a stalled motor, increasing the output current each time. If the electric cooling fan motor remains stalled after the sixth restart, the electric cooling fan control module waits 40 seconds. Afterwards the electric cooling fan control module notifies the PCM of the fault and begins the start process again.

The electric cooling fan control module incorporates 2 temperature sensors. Sensor 1 is used to calculate the temperature of the micro-controller. Sensor 2 is used to compensate for the self-heating of the inductor. Sensor 2 aims to reduce the power if the temperature is too high and to stop the motor in case of an over-temperature condition.

The system behaves according the following table depending on the sensor's temperature measurements.

If the temperature goes above TH2, the system stops the motor immediately. After a delay of 120 seconds the diagnostic feedback is sent back. The fan is switched on again if the temperature goes below TH1.

When a fault occurs with the ignition signal or the PWM signal, these are the electric cooling fan speeds set by the electric cooling fan module: