That's also why you need the loom going to the rear on the nav cars. The signal that feeds the amp on nav cars comes out of the bm54 and goes to the amp so there are no speaker wires (source wires) going to the front of the car.

When you have a non nav aka business cd it has a set of wires going from the amp to the front of the car already because the radio is the in dash not in the back like it is on a nav equipped car.

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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
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Aftermarket E53 Radio Install