I'm posting this in the B6 S4 discussion section but I'll bet it applies more generally to multiple models and years.

The wipers, washer and horn on my B6 S4 (2005) stopped working. It seemed odd that 2 unrelated systems stopped working at the same time, but in the end that helped figure out the problem. After a lot of reading in this and other Audi user sites I did the following:

I replaced the ignition switch (new OEM), the steering Control module (OEM - 8E0 953 549 N) and the clock spring/slip ring (8E0 953 541 E). Also replaced the wiper motor (again, OEM). No joy. Wipers, washer and horn still non-functional. All fuses were good and VCDS Lite (registered) reads in the wiper/washer measuring blocks that they were activating normally when I activated from the wiper/washer stalk. Measuring block for horn also shows activated when I depress the horn. Turn signals, high-beams, and cruise control were all working.

I have done the following after replacing the above parts:
1. Recoded the ABS Control Module (recode is stable)
2. Performed a Steering Angle Sensor (G85) Calibration (functions normal)

I was still showing only 2 error codes:

Address 09: Cent. Elect. Labels: 8E0-907-279-8E2.LBL
Controller: 8E0 907 279 F
Component: int. Lastmodul USA 0517
Coding: 01013
Shop #: WSC 63351
VCID: 351D47711C59
2 Faults Found:
01753 - Windshield Wiper Motor (V) Stage 1
31-00 - Open or Short to Ground
01754 - Windshield Wiper Motor (V) Stage 2
31-10 - Open or Short to Ground - Intermittent

It bears repeating that that none of the steering wheel modules were faulty. The local Audi dealer (Hoehn, Carlsbad) ran a diagnostic and would have replaced the clock wheel/steering angle sensor and the wiper motor. Neither was at fault (I now have some parts for sale on Panjo). They would have dinged me $2400 for parts and labor. Caveat emptor. Using VCDS Lite I tested all the measuring blocks for the ABS, Central Electronics and steering angle modules - all good. Activating the wipers, washer and horn all showed "activated" in the measuring blocks.

After checking all the wiring and relays, I replaced the J519 Central Electronics Control Module. That did it. Plug and play, no coding needed. Wipers, washer and horn all work now. Replacing the J519 was straightforward, and involved removing the fuse carrier (2 x 8mm bolts), lower driver's side dash trim (3 x 8mm bolts) and the J519 itself (2 x 10mm nuts).