Hi I have a 2007 Audi A6 2.0 tdi

Just driving along and the oil pressure warning came on so I promptly stopped and checked the oil level which was fine. I drove off again and surprise surprise same problem when I hit 2k rpm. The car has now gone in to full limp mode and engine management light is shining bright. Now here's the strange thing! The brakes appear to have gone as if there is no hydronic pressure on them. Goes without saying I have not attempted to drive the vehicle any further and any help on what I can check would be greatly appreciated before I am forced into paying audi a lot for nothing.