Pins 4 and 7 are used for the MB TV system. The pukka MB drawing shows pin 8 to be grounded.
For information:
C1 Pin out:
Pin 1 - TV Red (to TV tuner 4)
Pin 2 - TV Green (to TV tuner 3)
Pin 3 - TV Blue (to TV tuner 2)
Pin 4 - To TV tuner 10
Pin 5 - 0v to CD changer pin 1
Pin 6 - 12v to CD changer pin 2
Pin 7 - To TV tuner 1
Pin 8,9,10 - Linked and grounded by TV harness
The TV tuner also uses connections from C2
C2 pins to TV Tuner
Pin 2 - TV tuner 18
Pin 3 - TV tuner 8
Pin 11 - TV tuner 9
Pin 12 - TV tuner 17
Pin 17 - TV tuner 15 (can bus link to tuner)
Pin 18 - TV tuner 6 (can bus link to tuner)
The MB drawing showing the full Comand wiring layout (including TV, CD, Antenna amps etc) is drawing number PE 82.85-P-2100-99NC. At least I think it is. That's the only number on the drawing that looks like it could be the correct one.
Hope this helps.
Paul G