Hi!
To start you engine you have to:
1.Swap EWS chip from donor key to your car key (important-put it inside key)
2.Swap EWS II box (if you car don't have it I can send you instr. how to connect it, it's simple, but you'll need EWS antenna and donor EWS of course)
3.OBC makes no difference, I swaped mine form 323 since milleage misreading on 4cyl OBC. BUT YOU DON'T HAVE TO DO IT TO START CAR
4.Connect + and - from DME it's in wiring loom (that was my problem, since I connected + to car ground and (fortunetly) - to
REALOEM DIST. BOX nr 14. It has 2 different circuits so there was no power. After connecting - to ground and + to one circuit with accu, everything works fine. - BUT WITH THIS NOT CONNECTED CAR STILL WILL CRANK, NO FUEL AND SPARK THOUGH.
5.In X20 I made no changes (except connecting MPG to R6 cluster - no needed to start car)
6.Of course all engine wiring loom with DME (car computer), 2 relays (fuel pump and DME relay) is from 328i then it connects through X20 (round connector) to my car wiring.
No changes in OBC, OBD are needed to start car!
Check this and let me know.
Here you have photo of DME (- ground) 1st one and fuse box (+ positive) second one, they have to be connected also, and this black box is nr.14 on realoem diagram above, I have main + and DME + connected there(remember to connect them together with DME + connected throu fuse!). Also on 1st photo you can see round OBD connector from 328i
CONNECTIONS