I have just receive my new TT last Friday and realize when I hit the brake all the external lights comes on. The problem doesn't seem easy to trace. It looks like one wire is feeding into another. (pinch wire or wrong connection). Is there a diagram for the 21 FBS with the right color code. The one I have in my owner manual doesn't match the TT wiring existing colors. I have checked the wiring from my car with a trailer light tester (everything is OK) and the TT with another truck (same problem). Wire for STOP and TURN lights are not very accessible from under. There is a corrugated board under the trailer stuck in some places between the frame and the gas pipe or the dump valve that can be easily damage when move. Because it is a new TT I will bring it back to the dealer.