Remove screws holding the CD changer in place (if equipped)
Disconnect BMW CD changer 3 pin power plug and 6 pin audio plug from CD changer.
Connect MP3 Player to original CD changer connectors
If using the 3 and 6 Pin connector version MP3 player, you will need to connect the unit to a switched power source in order to retain its last song played memory function.
A good connection for BMWs built after Jan, 2000 production is the SES wiring plug, which is no longer used in cars that are equipped with the BMW Bluetooth system
Switched power is located on pin 24 Violet/White (or Violet/Red see image.
If you are also installing the DSP adapter module with your MP3 player you can connect the DSP module adapter to this pin in addition to using pin 14 brown/black for ground.