LVP, my impression is that the RF version of the Prodigy does not require any additional wiring to stock - primarily from the owner reviews. The key is getting the two units [a sending unit, portable, in the cabin, and the receiver, mounted on the trailer] to synch, and it appears the best method is to do it on a domestic US vehicle, then move the sending unit to your X5. I plan to get one to mount on the next horse trailer and move the sending unit between the X5 and the CEO's Benz diesel SUV.

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2006 X5 3.0 6-spd w/Evo UUC ssk
sport/premium pkgs
born Valentine's Day, 2006.