Hi Darren,
From what I can see your wiring looks correct and the diode is in the correct place and orientation. The diode isn’t the problem and it is required, it is simply a safety device to stop erroneous signals from the electronic trailer brake unit feeding back to the central junction box.
It appears you ran red cables for both the sense wire (red) and feed wire (blue), any chance you accidentally connected them the wrong way around at the Tow pro unit?
The wires should be connected as follows.
Cheers
Dean
Bookmarks