This post begins with BMW M6 F13 Gearbox problem description, and then followed with solution. Hope it helps if you had the exact same problem.
Car model and year:
BMW M6 F13
We change the Gearbox, because the old one is broken.
The new Gearbox is used. Its not a virgin Gearbox from BMW.
We buy it from UK. The seller says the gearbox is ok, he get this out from a running car.
We teach it with BMW ISTA, but nothing happens.
The Car starts fine, but the Gearbox is locked on P.
No error codes or something like that.
There is immobilizer in the gearbox mechatronic. If ISN mismatch you cannot engage gears… The ISN is only one-time programmable, so if your original gearbox mechatronic is not broken then just swap it in the second-hand gearbox and everything will work. If your old mechatronic is broken than well… buy a new one, ca.1000 euro
100% working solution:
The only known to me solution is swapping the electronic part of the mechatronics from one gearbox to another. Of course only if it’s not damaged and the reason for the malfunction of the gearbox. The late 6HP from E-Series (E70 and E71) also have immo but ISN is decryptable from RAM memory of mechatronics and you can virginize it via OBD. 6HP and 8HP from F-series, sorry but i don’t know any solution to read eeprom from the mechatronics (the ecu is welded inside metal container, see attached picture).
P.S.: you can solve it the other way round, get the CAS from gearbox donor car, read original ISN and change it in your cars CAS and DME/DDE
We solved the problem.
We swapped the electronic part of the mechatronic.
Now the car drives like a charm.
Everything works perfect.