FREE REPAIR MANUALS & LABOR GUIDES 1982-2013 Vehicles
Courtesy of Operation CHARM: Car repair manuals for everyone.

GF80.20-P-0002LE Remote Trunk Closing, Function



GF80.20-P-0002LE Remote trunk closing, function
- with CODE (881) Remote trunk closing (RTC [HDFS])


Function requirements for remote trunk closing, general
^ Circuit 30
^ No overvoltage or undervoltage
^ System synchronized
^ Vehicle speed v = 0 km/h

Normalization of the remote trunk closing should only be performed after replacing a component or after adjustment work on the trunk lid.

Remote trunk closing function, general
The trunk lid can be opened or closed automatically with the remote trunk closing function.

Manual operation of the trunk lid is possible, but requires increased force, since the hydraulic system also has to be moved.

Information on vehicle speed is transmitted to the TLC control unit (N121) by the instrument cluster (A1) over the interior CAN. The TLC control unit actuates the TLC hydraulic pump (M51) according to the request. The trunk lid then can be opened or closed with the hydraulic cylinder or multiple-joint hinge.

If various requests are present at the same time, the opening/ closing procedure is interrupted immediately and continued only after a new request is continued.

The trunk lid remote closing function comprises the following partial functions:
^ Function sequence for closing trunk lid
^ Function sequence for opening trunk lid
^ Function sequence for opening angle limitation
^ Function sequence for lockup recognition

Additional function requirements for closing trunk lid
^ Trunk lid opened

Function sequence for closing trunk lid
Closing the trunk lid comprises the following subfunctions:
^ Function sequence for closing trunk lid via TLC button (S62/26)
^ Function sequence for closing trunk lid via trunk lid open/ close switch (S20/1s6)

Function sequence for closing trunk lid via TLC button
Closing the trunk lid is requested by actuating the TLC button. The TLC control unit reads in the status of the TLC button and actuates the TLC hydraulic pump. The trunk lid is then closed by the hydraulic cylinder and the multiple-joint hinge. As soon as the trunk lid reaches the trunk lid rotary tumbler microswitch (M14/7s3), the rear SAM control unit with fuse and relay module (N10/2) transmits a corresponding signal via the interior CAN to the TLC control unit, which then switches off the TLC hydraulic pump. Simultaneously the rear SAM control unit actuates the trunk lid CL motor (M14/7), whereby the trunk lid is closed completely by the power locking feature.

On vehicles with code (889) Keyless Go the central locking (CL) can be locked additionally according to the actuation of the TLC button.

Function sequence for closing trunk lid via trunk lid switch
Closing the trunk lid can be requested by actuating the trunk lid switch. The status of the trunk lid switch is read in by the left front door control unit (N69/1) (model 221) or left door control unit (N69/1) (model 216) via the front door LIN and is transmitted to the TLC control unit via the interior CAN. The TLC control unit actuates the TLC hydraulic pump. The trunk lid is then closed by the hydraulic cylinder and the multiple-joint hinge. As soon as the trunk lid reaches the trunk lid rotary tumbler microswitch, the rear SAM control unit transmits a corresponding signal via the interior CAN to the TLC control, which then switches off the TLC hydraulic pump. Simultaneously the rear SAM control unit actuates the trunk lid CL motor, whereby the trunk lid is closed completely by the power locking feature.

Additional function requirements for opening trunk lid
^ Trunk lid closed

Function sequence for opening trunk lid
Opening the trunk lid comprises the following partial functions:
^ Function sequence for opening trunk lid via trunk lid external operation switch (S88/8)
^ Function sequence for opening trunk lid via trunk lid switch
^ Function sequence for opening trunk lid via transmitter key (A8/1)

Function sequence for opening trunk lid via trunk lid external operation switch
Opening the trunk lid is requested by actuating the trunk lid external operation switch. The rear SAM control unit directly reads in the status of the trunk lid external operation switch and actuates the trunk lid CL motor to unlock the trunk lid.

Then the rear SAM control unit transmits the status "Trunk lid unlocked" via the interior CAN to the TLC control unit, which then actuates the TLC hydraulic pump. The hydraulic cylinder is charged with oil and opens the trunk lid with the multiple-joint hinge.
The TLC control unit monitors the hydraulic motion over the trunk lid position sensor (B24/16). As soon as the trunk lid position sensor recognizes the determined end switch-off angle, the TLC control unit switches off the TLC hydraulic pump.

Function sequence for opening trunk lid via trunk lid switch
Opening the trunk lid can be requested by actuating the trunk lid switch. The left door control unit or left front door control unit reads in the status of the trunk lid switch via the front door LIN and transmits it via the interior CAN to the rear SAM control unit, when then actuates the trunk lid CL motor to unlock the trunk lid.

Then the rear SAM control unit transmits the status "Trunk lid unlocked" via the interior CAN to the TLC control unit, which then actuates the TLC hydraulic pump. The hydraulic cylinder is charged with oil and opens the trunk lid with the multiple-joint hinge. The TLC control unit monitors the hydraulic motion via the trunk lid position sensor. As soon as the trunk lid position sensor recognizes the determined end switch-off angle, the TLC control unit switches off the TLC hydraulic pump.

Function sequence for opening trunk lid via transmitter key
Opening the trunk lid is requested by actuating the trunk lid button on the transmitter key for longer than t = 0,5 s. The request is transmitted by the transmitter key via radio to the rear antenna amplifier module (A2/12) and relayed to the rear SAM control unit. The rear SAM control unit transmits them to the interior CAN. The EIS control unit (N73) reads in the request and checks the authorization of the transmitter key.

When the transmitter key is valid, the EIS control unit transmits a corresponding signal to the interior CAN.
The rear SAM control unit receives this signal, actuates the trunk lid CL motor to unlock the trunk lid and transmits the status "Trunk lid unlocked"via the interior CAN to the TLC control unit.
The TLC control unit then actuates the TLC hydraulic pump. The hydraulic cylinder is charged with oil and opens the trunk lid with the multiple-joint hinge. The TLC control unit monitors the hydraulic motion via the trunk lid position sensor. As soon as the trunk lid position sensor recognizes the determined end switch-off angle, the TLC control unit switches off the TLC hydraulic pump.

By actuating the trunk lid emergency opening switch (S88/10) (with code (494) USA version) the trunk lid is opened regardless of the vehicle speed and the locking status.

Function sequence for opening angle limitation
The limitation function of the opening angle serves to determine a new end position of the trunk lid (garage position or maximum opening) to prevent damaging the rear-end door by hitting against extending transportation goods (ski box, surfboard, etc.).
The "Garage position" can be switched on/off in the menu in the COMAND control unit (A40/3) or defined as new end position. Operation is accomplished over the front central control unit (A40/9) and displayed by the COMAND display (A40/8).

Function sequence for lockup recognition
The TLC control unit senses the current status and any change of the vehicle speed during opening/closing by the signals from the trunk lid position sensor.

If blockage is detected during closing the trunk lid, the TLC hydraulic pump is reversed and the trunk lid is moved to the initial position.

If blockage is detected during closing, the TLC hydraulic pump switches off and the trunk lid remains in the momentary position.