I recently installed a towbar on my X5 (2004 E53 3.0d). I then bought and fitted the tow control module that fits under the spare wheel. I made my own wiring loom from the socket located at the rear near the tailgate in the spare wheel well (by hooking up the indicator, brake, earth and tail light wires.) The trailer has led lights which "twinkled" when I hooked up the trailer, so I have now wired small clearance lights (incandecent) in parallel. When I plug the trailer in now The lights all come on.

Is there something I am missing? I have checked my wiring. Is there something special about the original wiring harness from the plug/socket inside the car to the trailer socket. If there is mine is just straight cable.

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2004 E53 diesel.
Titan silver on black
Sports package