P1253 - Boost Pressure Positioner Circuit open.
You can clear the code, but it's back before you had a change to reread the codes.
So, it's a hard fault. Either the "Positioner" or the wiring is disconnected.
I think this means a waste gate valve.

You would be better off reading BMW codes with a factory (or equivalent) tool.
There's not much to find on the internet about the BMW's specific codes.
Use a tool like this: http://www.bavariantechnic.com/