Because the eeprom in the ecu was faulty I couldn’t read the data from it so I replaced the eeprom with data from an identical ecu. It should have been possible to code this to the car, same as coding a used ecu, but the coding failed.
It would have been interesting to look into this further but time was against me so I re wrote the new eeprom with a free running file and let the car out without an immo.