[tshirt]

I did this a few months ago for my manual swapped 06. I hooked the manual harness to the old SMG harness. Required 1 re-pin on the SMG harness side, as one of the pins to hook to the manual was blank.

Then, I traced all the wires in the SMG harness I was using back to the DME box, using a continuity tester (negative clipped to SMG harness under the car via a jumper, positive in the DME box - where I found the wire in the old SMG harness.)

Once I had all the wires traced down to the DME box, I repinned / spliced into the DME harness (as described in e39source video). Then I spliced one wire (reverse sensor) into an abandoned SMG wire into the cabin (previously used for the DME shifter). That wire (now reverse sensor inside center console) was un-pinned from the SMG shifter harness and spliced under the dash to the LMA (lighting module). In the LMA, you pin the wire for reverse sensing via switch (as opposed to via CAN-BUS as it is for SMG). This is needed to get reverse lights working for the manual.

I also made my own wiring harness diagram based on my re-pinning and testing. If I had to do it all over again, I would note what wires are in the SMG harness and re-pin the manual harness to the easiest wires to deal with in the DME box. Someone could do a diagram and instructions for replicating this process, and the re-pinning. Would be nice to have on paper.

One last thing - you cannot easily buy the manual --> DME harness to simplify this process. It is part of the main engine harness. I think it is easier to just use the abandoned SMG plug and trace it down in the DME box under the hood.
e39source's video on this is the best resource - just go slow and verify everything he says. Especially the correct pin shape for the DME harness on the one new pin you have to insert!!

Happy to try and answer anywhere you get stuck or have questions!

@jbash87 here's another post I wrote (closer to the time when I did the wiring!!) https://www.m5board.com/threads/my-smg-→-6-speed-manual-conversion.614913/post-7704263

one other thought - there are several wires which trace back to the SMG harness in the DME box, but are bundled together (I think to ground). I separated those from other wires they were connected to, and spliced on jumpers to get them over to the DME harness..

That's the last of what I remember from the wiring!! 🤣