I am trying to diagnose a problem on my mates a4 2.8 quattro. When he is at very low speeds or slowing down and applying the brake, the ABS seems to operate when there is no loss of grip. It only seems to do it on the front. When I looked at the output for the wheel speed sensors, the front pair seemed to from to zero before the rears did. My suspicion is it's seeing the speed differential and kicking in. However there are no codes for the sensors or anything else. Is this a common problem? Any other suggestions appreciated as I don't want to start swapping bits due to the low value of the car.

Cheers Mike

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