Just thought I'd pass on the knowledge from my cars latest wobbler:
My 3.0 TDI had a little fit whilst out on the road, power was limited, glow plug light started flashing. Went home parked up and looked on the net for advice. Found no specific answers, some people said its a symptom of the turbo on the way out.... Went back to the car a day or two later and started off....holy sh1t, what a mess, wouldn't change gear automatically, only via paddles, ABS light came on, ESP light came on and when I stopped I couldnt get the key out!
Got an appointment with a superb indy Audi garage who reckoned these were all symptoms of fluctuating voltage due to a duff battery. he was right, replaced the battery, reset thousands of faults and away she went good as new..... phew, a relatively inexpensive outcome.