Hi Frank,
Could you please let us know which engine is in this A2? Your profile states that you've got a 1.4TDI, but that could be out of date or you could have 3 A2s! Also, what symptoms has the car got, please?
The only online references that I can find for P1601 relate to low battery voltage.
All VW/Audi fault codes are usually five numbers, such as 01844. Here is the Ross Tech definition for that fault code...
wiki.ross-tech.com
P1601 is a more generic, cross-brand fault code that's a little vague. Is your fault-code reader able to get the proper VW/Audi 5-digit code?
Cheers,
Tom