Audi usa has engineering control and were contacted and present during repair. Under very icy conditions on straight road, during acceleration from very slow speed, vehicle pitched into oversteer condition. Not entirely unexpected, but after a difficult recovery, when all seemed ok, it oversteered again quite violently. This was again recovered, but it appeared that there was an ABS brake input, certainly not of my doing. The third cycle was more severe, and I left the road. Neither the brake nor throttle were touched during the whole cycle, but steering inputs were powerful as I attempted to save the day. The separateness of the cycles alerted me to the possibility that the wheel speed sensors had detected a differential speed and applied the brakes. Audi refuses to release any data on the operation of their ABS system, and the volatile computer data has gone..it is noteworthy that some of the control functions previously identified, electronic stability control, etc, are now embedded in the ABS. The S4 did not have a stability control mechanism, it now does. This is a very powerful vehicle system, and if it should fail, the consumer should be able to know the criteria under which it should, could operate and/or fail. A years worth of communication has produced zero data from Audi.

- Naples, FL, USA