Gilly,
That is very cool the wires having all those numbers on them. I’ve surely never worked on a car that has that much information on wires. I do have Aldata DIY and I printed the page that tells how to interpret all those numbers, letters and the like.
I double checked the numbers and letters on the orange wires, as you said, and they are as follows:
1-orange wire coming from the green connector in my photo is #1600 - -NG28- 6->X58-7
2-orange wire coming from the black connector in my photo is #1600- -NG28-2->52-B-6
Both of these connectors go into the black convertor box which is NG28. Since X58 is the 10 pole trailer socket and the orange wire coming from the green connector says it goes from NG28 to X58
that’s the one to cut. The other orange wire (the one going to the black connector) goes to X52 which is the 16 pole connector that the trailer light harness connects to.
Here is the link to the wiring diagram for the brake controller. I copied this link from Wolfgang’s post above, and it’s also on Aldata DIY. It’s
http://www.whnet.com/4x4/pix/163_Brake_Controller_Wiring.pdf
Since the wiring diagram instructions say to run a wire to the front maybe the one up front by the dash will not work or doesn’t exist. It just seems odd the instructions do not say to tap in the orange wire in the dash. I will say that there is an orange wire going from NG28 to X52 and it must go somewhere but then even if it did connect to the brake controller it would still need to get back somehow to complete the circuit from the controller.
The other photo shows a connector with three wires, but I can not get to it enough to read any coded information on it and I don’t think it has to do with the trailer wire but who knows.