My Audi A8 4.2 Quattro is giving me headaches. I have a constant ABS warning on the dash, a heavy shatter when reaching 40 - 45 km. Checked all abs sensors, no prob. Took it to Audi, they could not get into the Computer to check for a fault. They suggested I check the ABS Pump. Does anyone have an idea what it could be. Pleeeeeeeeeeeeese help?