Pulling the fuse box to check the wires behind might be an easy job. Also pull the stereo and check wires behind. Not sure how all that's arranged in your TT but in our 23B all that came to pretty much the same location behind the stereo.
2013 F-350 CC SB 2WD 6.7PS
2013 Eagle Premier 351 RLTS
-SOLD- 2012 X23B
-SOLD- 2003 Ford Expedition 5.4, Bilstein shocks