Porsche Repair: Porsche Cayenne Turbo, porsche cayenne, lucky that way

Question
After replacement of accumulator navigation on PCM has ceased to work. How it to start?

Answer
Doctor,

I'm sorry, my expertise is in much older Porsches, like 50 years old...sometimes it's easy to relate problems on newer models to functions that have been on cars for a long time.  Usually I'm quite lucky that way.  In this case I believe I know what an accumulator is but I have no clue how it would relate to navigation or what a PCM even is.  Sorry.  If you could explain it in different terms I'd be happy to try again.

Dave