I have received and completed Serial Initerface B for a BMW '96 318ti and made the BMW modification. Everything works in INPA as OBD or ADS interface setting. Thank you.
I have a question please;
DTR (for BMW) is driven/inverted by a transistor T1. There is a spare, unused R2IN and R2OUT in IC1. Why use the extra transistor? Why did you not use the level translator (R2) for the L line?

Is this important?

Essential it operates...

btw:
This is your Thread...you can answer reply...
http://www.blafusel.de/phpbb/viewtopic.php?f=15&t=1427

Not important for operation. It works.
It is important for learning.