Part II

Automatic Luggage Compartment Lid ('Tailgate') Actuation

ID transmitter
With the ID transmitter, the following functions can be performed by the tailgates:
- Unlocking the small tailgate
- Opening the large tailgate
- Closing the large tailgate (not national-market version for US and Canada)

In the UK national-market version, the following functions are not possible until the vehicle has been unlocked:
- Unlocking the small tailgate
- Opening the large tailgate







The radio signal of the identification sensor is received via the rear window aerial. The remote control receiver integrated into the aerial diversity module forwards the signal to the Car Access System (CAS). The Car Access System (CAS) initiates the required operations.
The opened large tailgate can be closed with the ID transmitter (not the national-market versions for the US and Canada). The closing movement is continued until such time as the button is released, or until the large tailgate is completely closed.

External tailgate buttons
Two tailgate buttons are available for operation of the tailgates. These tailgate buttons switch to earth when activated. The signal for the tailgate buttons is detected by the junction box electronics (JBE). The junction box electronics (JBE) transmit the status of the external tailgate buttons via the K-CAN.
Both tailgates can be opened actively or passively.
- Active: The vehicle is unlocked by pressing the button on the identification sensor or by using the mechanical key on the driver's door lock. If the vehicle is unlocked, the tailgates can be opened by pressing the corresponding external tailgate button.

Passive opening of both tailgates requires the Comfort Access optional equipment.
Prerequisite: The ID transmitter is located near the tailgate.
- Passive: Even if the vehicle is locked, the tailgates can be unlocked and opened by pressing the corresponding external tailgate button.







The external central tailgate button enables the small tailgate to be opened.
The external right-hand tailgate button enables the large tailgate to the opened or closed electrically using the automatic luggage compartment lid actuation function.

Internal tailgate buttons
To operate the automatic luggage compartment lid actuation, up to 3 internal tailgate buttons may be available, depending on equipment status.







1. By pressing the internal tailgate button "Close tailgate", the large tailgate can be closed electrically.
2. By pressing the internal tailgate button "Open tailgate further", the opening height of the tailgate, not yet fully open, can be increased. This involves moving the large tailgate while the internal tailgate button "Open tailgate further" continues being pressed, or until the maximum opening height (highest contour on tailgate approx. 2290 millimeters) is reached.
Observe the opening height of the large tailgate and ensure enough clearance is available.

3. By pressing the internal tailgate button for deadlocking, all doors are locked and centrally deadlocked.
Prerequisite for deadlocking: front doors must be closed. When the large tailgate is open, it is also closed and deadlocked.

Tailgate button in passenger compartment
The interior tailgate button is connected via a line directly to the Car Access System (CAS).
The small tailgate can be unlocked using the interior tailgate button. The button is installed on the A-pillar and switches to earth when pressed. The Car Access System (CAS) evaluates the status and forwards the signal to the junction box electronics (JBE). The junction box electronics (JBE) evaluate the message and control the release drive in the tailgate lock of the small tailgate. Then the small tailgate can be opened manually.
Whenever the interior tailgate button is pressed during a movement by the large tailgate, that tailgate movement is stopped.







system overview

The following graphic illustrates the system network for the automatic luggage compartment lid actuation.







System functions

The following system functions are described for the automatic luggage compartment lid actuation:
- Electrical opening and closing of the large tailgate
- Manual opening and closing of the large tailgate
- Safety functions

Electrical opening and closing of the large tailgate
By operating the external right-hand tailgate button or the button on the ID transmitter, the large tailgate is opened or closed electrically.
In vehicles with Comfort Access, the large tailgate can even be opened when the vehicle is locked. An appropriate ID transmitter for the vehicle must be located near the tailgate.
The Car Access System (CAS) issues the release. The junction box electronics (JBE) carry out the unlocking of the large tailgate.
The tailgate contact switch changes from 'closed' to 'open'. Then the control unit on the automatic luggage compartment lid actuation (HKL) monitors the power consumption levels of both spindle drives.
The large tailgate is opened or completely closed to the preset opening height. If one of the blocking conditions is enabled during a tailgate movement, that tailgate movement is stopped. A short press on one of the tailgate buttons also stops the tailgate movement.
In the control unit on the automatic luggage compartment lid actuation (HKL), the 'Soft open' and 'Soft close' functions are integrated. Shortly before the tailgate reaches its end position, its opening speed is reduced, guiding it gently into its end position. This reduction in speed is accomplished using pulse width modulation of the activation voltage. If the end position is not reached, the large tailgate can be opened further using the internal tailgate button, 'Open tailgate further'.

Manual opening and closing of the large tailgate
When open, the large tailgate can be moved manually in the direction 'open' or 'closed'. Manual opening or closing is possible at any time. Operate the large tailgate manually, slowly and without any sudden movements. A distinction is made between the following statuses relating to the manual opening and closing of the large tailgate:
- automatic luggage compartment lid actuation control unit (HKL) enabled
- automatic luggage compartment lid actuation control unit (HKL) in rest state
- automatic luggage compartment lid actuation control unit (HKL) at "Terminal 30B off"

Automatic luggage compartment lid actuation enabled
While terminal 30B is switched on, manual tailgate movement is detected. The control unit on the automatic luggage compartment lid actuation (HKL) detects tailgate movement from the Hall sensors located in both spindle drives. The control unit on the automatic luggage compartment lid actuation (HKL) evaluates these Hall sensor signals and saves the current position of the large tailgate. For the next tailgate movement, this position is used as the starting point.

Automatic luggage compartment lid actuation in rest state
The current position of the large tailgate is saved in the control unit on the automatic luggage compartment lid actuation (HKL) before the vehicle goes into rest state.
In rest state, there is no monitoring of the position of the large tailgate.
Once the vehicle quits its rest state and the large tailgate has been opened, the current position is then not recognized. At the next operational request, the large tailgate is always first closed. The lower end position is detected by the control unit on the automatic luggage compartment lid actuation (HKL) from the status of the tailgate contact switch. This enables the position of the large tailgate to be compared against the start position saved in memory. The position of the large tailgate is then referenced again.
Whenever the tailgate movement is stopped before it reaches its bottom end position, the large tailgate is opened at the next operational request. Due to the fact that the position of the large tailgate has not yet been referenced, the large tailgate is only opened to the distance travelled when it was previously being closed. The tailgate movement takes place without any 'Soft start'.

Automatic luggage compartment lid actuation at "Terminal 30B off"
After shutting down terminal 30B, power supply to the spindle drives is switched off. This means that voltage supply to the Hall sensors is switched off. Manual tailgate movement cannot be detected. Whenever the position of the large tailgate is changed manually, the saved value no longer matches the current value. At the next operational request, the large tailgate is always first closed. The lower end position is detected by the control unit on the automatic luggage compartment lid actuation (HKL) from the status of the tailgate contact switch. This enables the position of the large tailgate to be compared against the start position saved in memory. The position of the large tailgate is then referenced again.
Whenever the tailgate movement is stopped before it reaches its bottom end position, the large tailgate is opened at the next operational request. Due to the fact that the position of the large tailgate has not yet been referenced, the large tailgate is only opened to the distance travelled when it was previously being closed. The tailgate movement takes place without any 'Soft start'.

Safety functions
The automatic luggage compartment lid actuation control unit performs the following functions:
- Evaluation of the CAN messages and operating requirements
- Puts the CAN messages into the desired position
- Activation of the spindle drives
- Monitoring of the spindle drives

Multiple requests
The control unit on the automatic luggage compartment lid actuation (HKL) evaluates the operating points for prioritization of multiple requests. If there is simultaneous operation at several operating points, the following priorities apply:
1. Internal tailgate button and external right-hand tailgate button (highest priority)
2. Tailgate button ID transmitter (lowest priority)

During continuous request of an operating point, this can be interrupted by an operating point with a higher priority. To make a new request using the operating point with the lower priority, this button needs to be pressed again.

Position detection
An electric motor is integrated in each of the spindle drives. Two laterally offset Hall sensors are installed in the spindle drive. This enables the direction of rotation of the spindle drives to be detected. Furthermore, the distance and thus the opening angle of the tailgate is detected on the basis of the Hall sensors. The Hall sensor signals can, for example, be used to set the opening height via the central information display (CID).

Blocking detection
Locking detection causes the tailgate movement to stop during an opening or closing sequence. If tailgate movement is locked while closing, the spindle drives are reversed briefly by the control unit on the automatic luggage compartment lid actuation (HKL). If movement of the large tailgate remains locked during the next operational request, the spindle drives stop being activated.
Locking is detected by the Hall sensor signals stopping, and by a rise in the power consumption of the spindle drives.

Repeat interlock
To prevent the spindle drives from overheating, a repeat interlock is integrated into the automatic luggage compartment lid control unit (HKL). The drive unit running time is added up for the repeat interlock. If the total exceeds an entire running time of 2 minutes, new operation is not accepted. Any initiated action is always run to the end. After a cooling-down period of 6 minute, it is then possible to run the drive units for 2 minutes.

Block conditions
To prevent vehicle damage, the large tailgate must not be opened in various situations. In these situations, movement of the large tailgate is inhibited.
The following blocking conditions are integrated in the control unit for the automatic luggage compartment lid actuation (HKL):
- Small tailgate not closed
- Driving speed exceeds 3 kilometres per hour
Exception: Locking command is completed.

- Ambient temperature below -30 degrees Celsius or above 80 degrees Celsius
Ambient temperature of instrument panel (KOMBI) via K-CAN.

- Vehicle voltage below 9 V or above 16 V
- Engine start
"Terminal 50 on" from Car Access System (CAS) via K-CAN or automatic engine start-stop function.

Power shutdown or reset with large tailgate opened
If the control unit on the automatic luggage compartment lid actuation (HKL) does not know the current position when the tailgate is open, in the first instance, the large tailgate can then only be closed. This prevents the tailgate from moving in 'open' direction towards its top limit position.
Procedure:
1. At the first operating request, the large tailgate starts to close.
2. In response to another operating request, the tailgate movement stops.
3. If the operating request is made again, the large tailgate opens to the initial position.

This function remains enabled until the tailgate position has been synchronized using the 'closed' tailgate contact switch.

Limp-home operating mode
If the automatic luggage compartment lid (HKL) control unit detects a fault it switches to emergency operation interval stage 1 or 2:
- Emergency operation stage 1:
Activation condition: Hall sensor prompts an active fault entry
The automatic luggage compartment lid function is partially deactivated. Direct activation is now only possible via the external tailgate button and the internal tailgate buttons. The large tailgate can now only be closed electrically.

- Emergency operation stage 2:
Activation condition: Spindle drive prompts an active fault entry
The automatic luggage compartment lid function is completely deactivated. Electrical movement of the large tailgate is no longer permitted. The spindle drives are not activated.

- Transition from emergency operation back into normal operation:
The transition to normal operation is reached using reset or by switching off terminal 30. The fault entries are rechecked.

Notes for Service department

NOTE: Observe repair instruction.

The service instructions do not replace the current information for service, nor the repair instructions. During repairs to components on the automatic luggage compartment lid actuation function, always follow the repair instructions. Only ever replace faulty spindle drives as complete units.

Replacing control unit on automatic luggage compartment lid (HKL)

NOTE: Observe the opening height.

Read off saved opening height before replacing the control unit on the automatic luggage compartment lid (HKL) at the central information display (CID) and transfer data to the new automatic luggage compartment lid (HKL) control unit.
When replacing the control unit on the automatic luggage compartment lid (HKL), disconnect the plug connections. To protect the control unit on the automatic luggage compartment lid (HKL) and the spindle drives, switch off terminal 30B.
Due to the activation conditions for emergency operation during start-up of the control unit on the automatic luggage compartment lid (HKL), always follow this sequence strictly:
1. Connect plug connections to the spindle drives
2. Attach plug connection for connection to the vehicle electrical system

After replacement of the control unit on the automatic luggage compartment lid (HKL), it is essential to initialize the top end position of the large tailgate. To do so, the large tailgate is moved when first opened to the top end position. Blocking action (inhibition of the Hall sensor signals) marks the point of maximum opening height for the large tailgate. A value of approx. 5 % of the total Hall sensor signals is subtracted from this point. This calculated point equates to the maximum selectable opening height of the large tailgate, i.e. approx. 2290 millimeters (highest contour on tailgate). This opening height is referred to as the "Soft Stop". Softstop prevents the large tailgate from opening up to the end position, which could damage it.
The lower end position is determined by the change of the tailgate contact switch of the tailgate lock from opened to closed. The junction box electronics (JBE) send the status of the tailgate contact switch via K-CAN2.
A corresponding service function needs to be performed for initialization purposes.

Replacing the spindle drives
To replace the spindle drives, the plug connections need first to be disconnected. To protect the control unit on the automatic luggage compartment lid (HKL) and the spindle drives, switch off terminal 30B.
Follow this sequence, dictated by the activation conditions for emergency operation:
1. Disconnect the plug connection for connection to the vehicle electrical system
2. Disconnect plug connections to the spindle drives
3. Replacing the spindle drives
4. Connect plug connections to the spindle drives
5. Attach plug connection for connection to the vehicle electrical system

Whenever the control unit on the automatic luggage compartment lid (HKL) is woken up, it checks to ensure that the spindle drives are attached. If the spindle drives are not yet connected, the control unit on the automatic luggage compartment lid (HKL) generates a fault entry. Due to the fault entry, the control unit on the automatic luggage compartment lid (HKL) inhibits activation of the spindle drives. The automatic luggage compartment lid actuation function does not respond, even if the spindle drives have been connected up. The control unit on the automatic luggage compartment lid (HKL) needs to be returned to its rest state and terminal 30B needs to be switched off. The spindle drives are checked again when they are next woken up. After a successful check, the automatic luggage compartment lid actuation function is enabled again.
Once a spindle drive has been replaced, the opening and closing action of the large tailgate needs to be adapted to reflect vehicle parameters. When new spindle drives are installed, the control unit on the automatic luggage compartment lid (HKL) is not aware of the position of the large tailgate. To enable the position of the large tailgate to be detected, the spindle drives need to be 'taught' to the vehicle. A corresponding test module needs to be performed for initialization purposes.

Failure of the control unit on the automatic luggage compartment lid (HKL)
If communication to the control unit on the automatic luggage compartment lid (HKL) fails, run the standard tests.
If there is an internal fault in the control unit on the automatic luggage compartment lid (HKL), the following response characteristics can be expected:
- Fault entry in automatic luggage compartment lid control module

National-market versions

National-market version for the USA and Canada

It is not possible to close the large tailgate using the ID transmitter.
The luggage compartment lid movement only starts after the tailgate button has been released.
1. Press the tailgate button and hold down for 500 milliseconds
2. Release the tailgate button

The ID transmitter sends a message through release of the tailgate button. Pressing of the tailgate button is detected from this message. The large tailgate is opened.
No liability can be accepted for printing or other faults. Subject to changes of a technical nature.

National-market version for the UK
In the UK national-market version, the following ID transmitter functions are not possible until the vehicle has been unlocked:
- Unlocking the small tailgate
- Opening the large tailgate