I installed the MB Ipod integration kit. The steering wheel volume control no longer works. All conection made as per MB shop manual.

Additionally, connected the brown/red wire from the interface into the spare opening of the Main Control Unit connector "spare" opening.
The unit will not power up if I replace the brown wire with the brown wire from the interface module. Spliced the brown wire from the interface to the brown wire from the MCU..system works however, no volume control from the steering wheel.

Also, the unit will power up and remain on when the key is removed.

 

You have to perform version coding to the audio system and if I remember correctly, the instrument cluster too. Must be performed using Mercedes SDS scan tool