My 2001 audi a6 quattro didn't start until several attempts. I had no problems with the car for several months. I drove 30 miles to work 80 mph and the car ran great. There was no check engine

SOURCE: Audi Fuel Pump

is it fitted correctly? If it is not fitted correctly it will do this. Have you checked the relay?

SOURCE: Check engine light/2004 Audi A6 Quattro/3.0L

hi, if you still have time to take it back to the dealer. take it to them.

SOURCE: ESC light came on when driving - then check engine light

Likley there is a misfire in one of the cylinders. Usually due to worn out sparkplugs or wires. A check by the local mechanic, using his/her computor will pinpoint the problem. Or go to your local auto supply store & purchase the little computor to connect to your car computor (under dash at steering wheel). This will allow you to turn off the light. Cost is about $170.00 (Can.)
Hope this helps!
JDR

SOURCE: I have a 1999 Audi A6 quattro, have just changed original fuel

You have to bleed the system, most likely air, or you blew the fuel pump fuse !

SOURCE: Audi A6 3.0 tdi Quattro 2005, glow plug light comes on, limp mode

16619 -Engine boost condition - Limit not reached. Check intake hoses/ connections for leaks. Check Turbo charger waste gate regulating valve/ waste gate working correctly. Must move freely when accelerating, won't achieve full boost if waste gate sticking open. Check Turbo impeller turning freely, oil feed pipe for turbo can get blocked causing impeller to seize. Engine compact, not easy to access these components.