System functions

Functional networking using the example of F01

Fig 1: Automatic Trailer Tow Hitch - Circuit Diagram

Courtesy of BMW OF NORTH AMERICA, INC.

Functional networking using the example of F30

Fig 2: Automatic Trailer Tow Hitch - Circuit Diagram (F30)

Courtesy of BMW OF NORTH AMERICA, INC.

• Automatic inward and outward pivoting 
  • Vehicles up to model year 11/2011:

    Briefly pressing the button (for less than 1 second) pivots the ball head fully automatically from one end position to the other. Fully automatic pivoting out or in can be halted at any time by briefly pressing the button a further time. Fully automatic pivoting out or in can only then be started when the ball head is in one of the two end positions. Or the fully automatic pivoting out or in has been stopped by pressing a button. The operating function of the button is as follows (starting position: ball head pivoted in):

    • Short press on button: The ball head begins to pivot outwards
    • Next keystroke: Pivoting out of the ball head is halted immediately
    • Next keystroke: The ball head begins to pivot inwards
    • Next keystroke: Pivoting in of the ball head is halted immediately
    • Next keystroke: The ball head begins to pivot outwards
  • Vehicles as of model year 11/2011:

    Briefly pressing the button (for less than 1 second) pivots the ball head fully automatically from one end position to the other. Fully automatic pivoting out or in cannot be halted by briefly pressing the button a further time. Fully automatic pivoting out or in can only then be started when the ball head is in one of the two end positions.

• Reversing the pivoting movement 

  If during fully automatic pivoting out or in the permitted DC motor power consumption is exceeded (e.g. due to an obstruction or stiff movement at low ambient temperature): The control unit initiates reversing for the fully automatic trailer tow hitch. The ball head's swivel motion is halted. The ball head is pivoted back a short way in the opposite direction (reversed). It can now only be moved by continuous operation of the button (manual operation). Reversing is suppressed close to either end position and a higher current consumption is permitted. This allows the ball head to be pivoted out of each end position with more force (e.g. to release the ball head if stuck).

• Pivoting out or in by continuous operation of button 
  • Vehicles up to model year 11/2011:

    This mode is initiated by operating the button for the fully automatic trailer hitch for longer than 1 second. The ball head only pivots for as long as the button is pressed. If the button is pressed again, the ball head is pivoted in the opposite direction to its previous pivoting. The ball head's pivoting movement stops when the button is released. A further swivel motion can only be performed in this mode. Increased current consumption by the DC motor is permissible in the continuous button-operated mode. If the current consumption permissible in this mode is exceeded, the ball head's pivoting movement stops. The ball head does not pivot in the opposite direction to its previous pivoting (no reversing in this mode). Only if an end position is reached in this mode is automatic pivoting out or in possible again.

• Initialization 

  When initializing, the entire swivel angle and both end positions of the ball head are tracked in the control unit for the fully automatic trailer hitch. The limit positions are stored in the control unit.

  If the initialization of the fully automatic trailer tow hitch is lost, the red LED in the button for the fully automatic trailer tow hitch will flash or light up.

  • Sequence for manual initialization: 

    Press the button and hold it until the trailer tow hitch has completely moved in the direction of the work position and back to the rest position.

    NOTE: If the trailer tow hitch stops in an end position, but the LED does not light up green, the button must be released briefly. Next, press the button again until the other end position is reached.

    The LED will continue to flash until the initialization is finished. Next, it will light up green continuously.

    If the initialization was unsuccessful, repeat the procedure or run the initialization with the diagnosis 

  During the initialization process, the maximum current of the drive motor is permitted and reversing of the ball head is suppressed.

• Signalling via the indicator light in the button for the fully automatic trailer tow hitch 

  The indicator light in the button for the fully automatic trailer hitch is a 2-colored LED (red and green). The indicator light is activated directly by the control unit for the fully automatic trailer hitch.

  The indicator light shows the system status. Example:

  • Indicator light off:
    • Conditions required for switch-on not met
    • System not operational, e.g. due to blown fuse or broken lead
  • Indicator light lights up green:
    • Ball head locked in one of the 2 end positions and conditions required for switch-on met
  • The indicator light flashes or lights up red continuously: Fault
• Adjusting the trailer hitch 

  To ensure that the trailer tow hitch remains pivoted in the end position, the DC motor is energized briefly in the direction of the limit stop every 60 seconds. The control unit for the fully automatic trailer tow hitch activates adjustment in the following conditions: Terminal 15 on and pivoted ball head in end position.

• Emergency function 

  Cyclical readjustment of the pivoted-out ball head can result in the ball head becoming mechanically jammed. In this event, the ball head can be freed from the limit stop by the emergency function. A defined swivel motion must be achieved in the initial phase for pivoting the ball head out or in. This pivoting movement corresponds to a defined number of Hall impulses by the DC motor. The Hall pulses are picked up by the Hall effect sensor on the DC motor. If a defined number of Hall pulses is not  reached, the control unit activates the emergency function. In the emergency function, the DC motor is energized five times cyclically (each cycle comprises energizing for 300 ms followed by a pause of 200 ms). If the minimum number of hall signals are not achieved, the ball head can then only be pivoted in or out by continuous operation of the button for the electrically pivoted trailer tow hitch.

• Emergency operation 

  If the voltage supply is interrupted during operation, various signal statuses could be lost. When power is available again, the button must be pressed and held for 5 seconds. This will switch the powertrain on (emergency operation).

• Undervoltage and overvoltage 

  The fully automatic trailer two hitch control unit detects undervoltage and overvoltage. Undervoltage: Vehicle voltage less than 9 V. Overvoltage: Vehicle voltage greater than 16 V. If overvoltage or undervoltage is detected during pivoting in or out of the ball head, the ball head still pivots as far as the end position. The fault is then indicated via the LED in the button. If an overvoltage or undervoltage is detected during continuous operation of the button for the fully automatic trailer hitch, the ball head can still be pivoted into the end position. The ball head's pivoting movement stops when the button is released. The DC motor can then no longer be energized while the overvoltage or undervoltage persists.

In the event of a fault, the electric motor of the fully automatic trailer tow hitch can be replaced separately.

We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.