Trunk lid control, function - GF80.20-P-0012FL

MODEL 212.0 with CODE 881 (Remote trunk closing (RTC [HDFS])) 

MODEL 212.1 with CODE 881 (Remote trunk closing (RTC [HDFS])) 

Fig 1: Trunk Lid Control Function Diagram - Model 212.0

Courtesy of MERCEDES-BENZ USA

Function requirements, general 

• Trunk lid opened
• Speed v = 0 km/h
• Transport mode not activated (as of 1.6.12)

The speed signal is transmitted by the instrument cluster to the liftgate control unit via the interior CAN.

Detailed information on the operating state of the transport mode is given in the separate function description for energy management.

Trunk lid control, general 

The trunk lid can be closed automatically with the trunk lid control. The trunk lid control comprises the following partial functions:

• Function sequence for requesting trunk lid closing 
• Function sequence for closing trunk lid 
• Function sequence for position recognition 
• Function sequence for antilock device 

Function sequence for requesting trunk lid closing 

The trunk lid can be closed from the following control points:

• Driver trunk lid/liftgate control button 
• Trunk lid control button 
• Rear switching module (with code (871) Sensors for trunk lid/opening/closing) 

The trunk lid control unit reads in the control request via the interior CAN.

Driver trunk lid/liftgate control button 

The left front door control unit directly reads in the status of the driver trunk lid/liftgate control button and transmits this to the trunk lid control unit via the interior CAN.

Trunk lid control button 

The rear SAM control unit directly reads in the status of the trunk lid control button and transmits it to the trunk lid control unit via the interior CAN.

On vehicles with code (889) Keyless Go:

On vehicles with code (889) KEYLESS-GO, the central locking can also be locked with the trunk lid control button ("Lock" symbol). Detailed information is given in the function description "KEYLESS-GO".

Rear switching module (with code (871) Sensors for trunk lid/opening/closing) 

The rear switching module can be opened and closed without touching using the rear switching module. The function is actuated by foot motion ("kick motion") in the rear of the rear switching module below the bumper. For this purpose a transmitter key must be located in the vicinity.

The rear switching module directly reads in the signals from rear switching module sensors, evaluates them and transmits the corresponding request to the KEYLESS-GO control unit via the KEYLESS-GO LIN. The KEYLESS-GO control transmits these signals to the liftgate control unit via the interior CAN.

Function sequence for closing trunk lid 

The trunk lid control unit reads in the "Close trunk lid" request via interior CAN. Then the trunk lid control unit actuates the trunk lid control electric motor in the close direction until the rear SAM control unit recognizes that the trunk lid engages in the trunk lid rotary tumbler via the status of the trunk lid rotary tumbler switch. Then the rear SAM control unit actuates the trunk lid lock element (power closing). The trunk lid is now fully closed. The trunk lid control unit actuates the trunk lid control warning buzzer during actuation of the trunk lid control electric motor due to the request from the rear switching module (with code (871) Sensors for trunk lid opening/closing).

It is only possible to close the trunk lid manually with the driver trunk lid/liftgate control button. This means that the trunk lid is closed only as long as the driver trunk lid/liftgate control button is actuated.

Function sequence for position recognition 

If the trunk lid is closed with the trunk lid control electric motor, the current position of the trunk lid is recognized by the trunk lid position sensor and transferred to the trunk lid control unit.

Function sequence for antilock device 

If an obstacle is recognized by the trunk lid control unit when closing the trunk lid with the trunk lid position sensor, the closing operation is interrupted immediately and the trunk lid control unit electric motor drive is reversed.

When the trunk lid control electric motor drive reverses, the trunk lid is opened mechanically by spring force, not electrically The trunk lid control electric motor is moved back to the starting position.

If the trunk lid control unit, the trunk lid control electric motor or trunk lid position sensor is replaced, it is necessary to renormalize the trunk lid remote closing system with the diagnostic tester.