There are loads of different diagrams based on model year and which audio system you have and different diagrams for different bits.
What model year, What system (Audio-20-Cassette, Audio-20-CD, Audio-50, COMAND)
BUT, there is no ignition power to any of it. All communication with the car is done over CANbus (car's network) to the AGW (amp/tuner/diagnostic-gateway) - which in itself is either in the boot on the left or part of the stereo.
