Fully automatic trailer tow hitchE70

The fully automatic trailer tow hitch is an element of the optional extra 'trailer tow hitch with articulated ball head'. This optional extra has been offered for the E70 since 09/2009. The fully automatic trailer tow hitch is operated using a button in the luggage compartment.

NOTE: During the automatic swivel motion of the ball head, no mechanical forces must be exerted on the ball head.

Ensure that the movement range of the ball head is free of obstructions.
There must be no impact (e.g. blows, kicks) on the ball head during the unlocking and locking procedures and while swivelling.

The control unit for the fully automatic trailer hitch uses the signal states to check whether the pivoting movement can be started. If the switch-on conditions are met, the following procedures can be performed by pressing the button for the fully automatic trailer tow hitch, depending on the version:

for vehicle up to version 11/2011
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.
- Automatic pivoting out or in (single brief press of button)
  Briefly pressing the button (for less than 1 second) pivots the ball head fully automatically from one end position to the other. During the first few seconds, the system unlocks the ball head. During this period, no movement of the ball head is visible. The ball head then moves to its end position and is locked again. Fully automatic pivoting out or in can be halted at any time by briefly pressing the button a further time.
  
  The operating function of the button is as follows (starting position: ball head pivoted in):
  - Short keystroke:
    The ball head pivots out.
  - Next keystroke:
    Pivoting of the ball head is halted immediately.
  - Next keystroke:
    The ball head pivots in.
  - Next keystroke:
    Pivoting of the ball head is halted immediately.
  - Next keystroke:
    The ball head pivots out.
  - etc.
- Pivoting out or in by continuous operation of button
  This mode is initiated by operating the button for the fully automatic trailer tow hitch for longer than 1 second. The ball head only pivots for as long as the button is pressed. If the button is held pressed, the ball head is pivoted in the opposite of its previous direction of 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 direction of pivoting (no reversing in this mode). Only if an end position is reached in this mode is automatic pivoting out or in possible again.
- Indicator light in button for fully automatic trailer tow hitch
  The indicator light in the button for the fully automatic trailer tow hitch shows the system status via 2 LEDs (red and green).
  
  The following signalling is possible:
  - The LED lights up green :
    Ball head locked in one of the 2 end positions and conditions required for switch-on met
  - The LED flashes slowly green (2 Hz):
    The ball head is in the locked end position ("pivoted out") and the trailer connector or an adapter is in the trailer socket.
  - The LED lights up red :
    There is undervoltage or overvoltage at the control unit for the fully automatic trailer tow hitch
  - The LED flashes slowly red (2 Hz):
    Ball head in motion or not in a locked end position
  - The LED flashes quickly red (4 Hz):
    - Control unit for the fully automatic trailer hitch is not initialized
    - Maximum current for activation has been exceeded. (obstacle or stiff movement in the mechanism)
    - Control unit for the fully automatic trailer tow hitch is faulty
  - The light-emitting diode is OFF:
    - Conditions required for switch-on not met
    - System not operational, e.g. due to blown fuse or broken lead
- Reversing the pivoting movement
  If the permissible power consumption of the direct current motor is exceeded during fully automatic pivoting out or in (e.g. as a result of an obstruction, stiff movement at low ambient temperatures), the control unit for the fully automatic trailer tow hitch triggers reversing. The ball head's swivel motion is halted. The ball head is pivoted back a short way in the opposite direction (reversed). 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).
Vehicles from version 11/2011
Fully automatic pivoting out or in can only then be started when the ball head is in one of the two end positions.
- Automatic pivoting out or in (single brief press of button)
  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.
- Indicator light in button for fully automatic trailer tow hitch
  The following signalling is possible:
  - 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 2 end positions (rest position or operating position) and switch-on conditions fulfilled
  - Indicator light flashes green:
    - Ball head is moving (ball head pivoting out or in)
  - Indicator light lights up red:
    - Ball head in intermediate setting (not in rest position or operating position)
    - Trailer module (AHM) not initialized
- Reversing the pivoting movement
  If the permissible power consumption of the direct current motor is exceeded during fully automatic pivoting out or in (e.g. as a result of an obstruction, stiff movement at low ambient temperatures), the control unit for the fully automatic trailer tow hitch triggers reversing. The ball head's swivel motion is halted. The ball head then swivels in the opposite direction into the end position.
  
  If the ball head blocks again before the end position is reached, the swivel motion stops immediately.
  
  The following example shows the sequence during reversing when the swivel motion is blocked in both directions (initial setting: rest position of the hitch):
  1. Brief press on the button for the fully automatic trailer tow hitch
  2. Hitch swivels from the rest position to the work position
  3. Hitch blocks during the swivel motion
  4. Hitch swivels in the opposite direction (into rest position)
  5. Hitch blocks again
  6. Swivel motion is immediately interrupted
  7. Indicator light in the button lights up red
  8. Continuous pressing of the button causes the ball head to move in the opposite direction (into work position). 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).

For the fully automatic trailer tow hitch to pivot out and in, the following switch-on conditions must be met:

Terminal 30B ON
Tailgate open
Range close to stationary
Valid speed signal
Trailer connector not plugged into the trailer socket (only with ball head articulated outwards)
No overvoltage or undervoltage in the vehicle voltage

If the ignition is switched off , the system is deactivated after some time . (LED goes out). In order to reactivate the system either:

Close and then reopen tailgate or door
Switch on ignition.
press the 'Open central locking' button on the master key