The main thing is its key switched to the accessory position. This means that turning the key one click on (accessory position) makes the radio and the ibus adapter come on when wired this way.

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Just BMW's - All cars and trucks was two pages long
1994 318is
1997 528i
2000 323i
2001 X5 3.0 auto
2005 X5 3.0 auto
2011 535xi auto
2013 X5 xdrive35 Turbo
More are at my website

Aftermarket E53 Radio Install