Trunk Lid Module

Automatic opening and closing of trunk lid/tailgate

Function

Automatic opening and closing of the trunk lid/tailgate is controlled by the trunk lid/tailgate module and the general module of the ZKE III.

The trunk lid/tailgate is opened and closed by means of a hydraulic system, consisting of a hydraulic pump and two hydraulic cylinders. The hydraulic system is controlled by the trunk lid/tailgate module.

In addition to the hydraulic system, an automatic soft-close facility (fitted as standard on E38) and an electrical rear lid release (fitted as standard on E39) are also fitted on the rear lid. These components are controlled by the general module of the ZKE III.

The general module and trunk lid/tailgate module are interlinked via the K-bus.

Trunk lid opening procedure

• Release button is pressed.
  
• The ZKE III general module receives the instruction to open the trunk lid/tailgate. It activates the drive for the automatic soft-close facility and the drive for the rear lid release. The rotary latch of the trunk lid/tailgate is opened and the lock striker is turned upward.
  
• The rear lid contact signals "trunk lid/tailgate open" to the general module. This signal is routed via the K-bus to the trunk lid/tailgate module.
  
• The trunk lid/tailgate module powers the hydraulic valve and the hydraulic pump. The trunk lid/tailgate is opened by means of the hydraulic cylinders.
  
• With the aid of a tilt switch on the trunk lid/tailgate, the trunk lid/tailgate module detects when the trunk lid/tailgate is fully open and switches off the hydraulic pump after an run-on time of approx. 1 second.
  

Trunk lid closing procedure

• Release button is pressed.
  
• The trunk lid/tailgate module powers the hydraulic valve and the hydraulic pump. The trunk lid/tailgate is closed by means of the hydraulic cylinders.
  
• When the trunk lid/tailgate is closed the trunk lid/tailgate contact signals "trunk lid/tailgate closed" to the central body electronics control module in the ZKE III. Its signal is routed via the K-bus to the trunk lid/tailgate module. The hydraulic pump is switched off.
  
• The general module activates the drive for the automatic soft-close facility. The lock striker of the trunk lid/tailgate is turned down thus pulling the rear lid closed.
  

Operating buttons

The trunk lid/tailgate opening and closing functions are operated by means of three pushbuttons.

• Operating button for trunk lid/tailgate closing cylinder
  The trunk lid/tailgate can be opened and closed by pressing the lock cylinder in the trunk lid/tailgate.
  The pushbutton is connected both to the trunk lid/tailgate module as well as to the general module in the ZKE III.
  
• Operating button for trunk lid/tailgate, inside
  The trunk lid/tailgate can be opened and closed by pressing this pushbutton.
  The button is only connected to the trunk lid/tailgate module. A closed trunk lid/tailgate cannot be opened by means of this button as the signal from this button is not sent to the general module in the ZKE III, consequently the rotary latch is not released.
  
• Operating button, vehicle interior
  The trunk lid/tailgate can be released and opened by pressing this button (located in A-pillar on driver's side). The trunk lid/tailgate cannot be closed with this button.
  The pushbutton is only connected to the general module in the ZKE III. Its signal is routed via the K-bus to the trunk lid/tailgate module.
  

All operating buttons switch to ground.

If the buttons are struck briefly the trunk lid/tailgate is fully opened (all pushbuttons) or closed (only buttons in trunk lid/tailgate).

If the trunk lid/tailgate is moving, it is stopped when a button is pressed once more.

Radio remote control

The trunk lid/tailgate can also be opened and closed by means of the radio remote control.

The trunk lid/tailgate is opened by pressing the key button with the trunk lid/tailgate symbol. If the trunk lid/tailgate is moving, it is stopped when a button is pressed once more.

The button on the key-chain transmitter must be pressed and held in order to close the trunk lid/tailgate.

Tilt switches

A tilt switch is fitted in the trunk lid/tailgate in order to detect its position. The switch is active when the tailgate has reached the upper stop (tailgate open). The tailgate module then switches off the hydraulic pump after an run-on period of 1 second.

Hydraulic system

Components

The hydraulic system consists of the following components:

• Hydraulic unit
  contains the hydraulic pump and the pressure relief valves
  
• Hydraulic lines
  Connections between the hydraulic unit and hydraulic cylinders
  
• Hydraulic cylinders
  Mounted on left and right of trunk lid/tailgate
  

The system is operated with a maximum pressure of 100 bar.

The hydraulic system is maintenance-free and self-venting.

Note

The procedures described in the repair instructions must be followed when working on the hydraulic system.

Hydraulic pump

The hydraulic pump is controlled by the trunk lid/tailgate module in the directions of rotation "open trunk lid/tailgate" and "close trunk lid/tailgate".

Power is supplied by means of two relays integrated in the trunk lid/tailgate module.

A repeat lock facility prevents the hydraulic pump overheating. The pump is switched off for approx. 6 minutes if it was in operation for longer than 2 minutes within a short space of time.

Pressure relief valves

The pressure relief valves are integrated in the hydraulic unit and limit the maximum possible pressure in the hydraulic cylinders.

The pressure is limited to maximum 100 bar to open the trunk lid/tailgate and to maximum 60 bar to close the trunk lid/tailgate.

Emergency mode

In the event of system failure, the trunk lid/tailgate can be opened and closed manually by exerting little pressure.

An emergency valve is additionally integrated in the hydraulic unit which, in the event of system failure, maintains a system pressure of 40 bar thus ensuring the trunk lid/tailgate movement is dampened.