have 01 A4Q 2.8l with about 140km. Parked the vehicle for a week and noticed that the brakes were feeling very soft and behaving funny. had to pump the pedal to get an effective braking action where i felt some control; otherwise the pedal would sink with less than normal braking effect until it reached almost to the floor and then the ABS would kick-in and i would get the typical chattering but effective ABS braking. there were no warning lights on the dash. the OBD was not throwing any codes.
i took it to the shop where they bled the system and replaced the fluid; then replaced master cylindar. in both instances the problem persisted. on the test drive i pulled the fuse for the ABS and the braking returned to normal!

ON a hunch i replaced the left front speed sensor, no change. I took the car to a tech shop with VAG and they hooked up and monitored for about 45 minutes. no codes apparent from the control module but the readout on the wheel sensors indicated an intermitent low reading from the right rear wheel (-1 or -2km) I had the right rear sensor changed. the problem still persists.
I am suspecting the ABS control module but when hooked up to VAG the indications where that it was performing properly. Anyone ever experience a situation where the module has tested normal on the bench but was malfuncitoning on the vehicle?
anyone have any experience with a similar problem or any recommendations? it's driving me nuts and costing me money for nothing.

Part 2 of my problems; now the cruise control is intermittently dropping out. cruise operates normally otherwise. can the two issues be related?

Thanks

Sounds like you've ruled out just about everything else. Basically the speed sensor can't get a good reading and the ABS reacts. If you do some searching you'll find pics of the cracked ring. Seems like somewhat of a common problem with the B5 S4s.<ul><li><a href="http://forums.audiworld.com/s4/msgs/2709900.phtml">Similar issue here</a></li></ul>

Having the exact same issue on my 98.5Q. Including the cruise control not working. I'm not getting any codes on ABS, and my right rear readout on my vag is lower than the others. No break on my reluctance ring, and new speed sensor. Can anyone assist with this one? I'm going on 10months and it's frickin' driving me nuts...grrr!