Originally Posted by 
Nod
				 
			Just to be clear... you cut the brown wire away from the black at the splice (SJ571) in the rear passenger side cubby?
The brown is then soley connected to the blue from the brake controller.
(Not causing this issue...) Did you insert the diode in the red... from the ECU?  Before the wire from the brake controller & the Red to 12N socket Pin 6.
If the above is correct... with a multimeter check at the 12N socket (black) Pin 5 (service brakes) for +12V to ground (or Pin 3) when braking.
If this is correct... then there is a problem in the wiring between the 12N socket and the trailer/van.  Is this an OEM unit?