Two years ago my car wouldn't start after driving 300m or so. Audi first figured the fuel pump was no longer working. Turned out it was only a general purpose relay that was faulty, 4H0 951 253 A.
Could this cause your symptoms?
The relay is very inexpensive, I paid SEK 205 for the part.
On LHD cars, the relay box sits on the drivers side, opposite the ECU on the passenger side
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Johannes
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Audi S8 -99, Pearlescent, Alcantara/silk napa leather, Burr walnut insert, Alcantara roof lining upper pack
A8 32V engine
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Jeep Grand Cherokee -98