I WAS HAVING A PROBLEM WHIT AN ENGINE SWAP I WAS WORKING WHIT,,
6.2L 6L80E E38 T43
The harness was made by me
This was the problem:: When i started the car and if there was this code present: P2534 the trans will stay on in 3rd gear in limp mode, if you delete the code it will work perfect again but on the next switch cycle the code will return and the limp mode will return

This is the solution i found::
I used the E38 BLACK CONECTOR pin number 59, this wire will output a ground signal to turn on a relay.. i used this wire to turn on one relay dedicated just for the trans ON switch signal wire, pink color. this did the trick, no more P2534 code and no more limp mode.. i dont know exactly why, but this worked for me.

I was frustated because of this so i wanted to share the solution in case someone else have the same problem

Thanks everyone and sorry for my english

Feel free to rewrite this to make it more understandable