While you can tap into the tail and brake lights, and you may not get any dashboard warnings, you do not get the benefits of disabling the rear PDC (you have to do it manuall). I don't think you get the trailer stability control feature activated either.

Some have had no trouble with wire taps for lights. Others have had lots of problems. My advice would be to go ahead and try it if you can't find the BMW part, but if you have warning signals be prepared to remove the wiring.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue