I have this done on my 2005 E53 and my 2003 E39 and some cars it is the green while others are brown. In short, as long as you are using the tap, you are fine. Tap into the wire, it if does not work, try the other. I used the homelink in both cars. The E53 had the homelink while the E39 did not but still had the wires. Very simple project and clean results...check them our on my site.

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2011 550xi Carbon Black/Oyster, M-Sport, Premium Package, Technology Package, Electronic Damper Control, Dynamic Drive, Comfort Access, Active Seats, Surround Cameras

2013 X5 5.0 Space Grey/Black, M-Sport, Premium Package, Technology Package, Comfort Access, Surround Cameras