Central Locking Coding (V94 Pump)
 

I think the Ross-Tech guidelines for V94 coding are missing a few things. The coding on my car was originally 16140. If I add up all the possible options listed by Ross-Tech, they don't add up to 16140. At most, I end up with 15215. This is the list provided by Ross-Tech:

+00001 - Rear Lid Opening via Rear Lid Lock
+00002 - Anti-Theft Confirmation via Blink
+00004 - Selective Locking
+00008 - Anti-Theft-System
+00032 - Locking via Speed
+00064 - Comfort Closing via Remote Control
+00256 - Rear Lid Logic
+00512 - Remote Control "Close" Confirmation (1x Blink)
+02048 - Door/Window Logic (USA)
+04096 - Remote Control "Open" Confirmation (2x Blink)
+08192 - Remote Control

Near as I can figure, there's definitely something missing at +01024, and possibly also at +00128. The +01024 thing is something that was enabled on my car by default, but I haven't noticed anything missing since I disabled it, so I really have no clue what it could be. As for +00128, if that does anything at all, it's also a complete mystery.

Anyone know what those things could be?

P.S. My car used to beep when I locked the doors, but hasn't done so in months. I assume the alarm module's battery is dead. It's possible that that's what +01024 is, which would explain why I don't notice any difference now.

so... no-one knows? It's a complete mystery?

In the absence of any useful information, I just spent a bunch of time trying things randomly and looking for differences. The differences can be so minor as to be nearly invisible, but with a bit of luck, I was able to solve at least some of the mystery.

As I mentioned in my OP, my car was originally coded with 16140. This turns out to be the following options:

+08192 - Remote Control
+04096 - Remote Control "Open" Confirmation (2x Blink)
+02048 - Door/Window Logic (USA)
+01024 - (unknown)
+00512 - Remote Control "Close" Confirmation (1x Blink)
+00256 - Rear Lid Logic
+00008 - Anti-Theft-System
+00004 - Selective Locking

I should point out that on my car, Remote Control "Close" Confirmation does not appear to work at all. No lights blink and no horn sounds when I lock the car using the remote. So it's hard to confirm.

Near as I can tell, it's impossible to code out the Anti-Theft-System. The system always adds 8 back to the coding if you attempt to remove it.

Now onto my discoveries:

+00016 does something really weird... it reverses the buttons on the remote. So pressing the unlock button locks the car and pressing the lock button unlocks it. I can't see much use for that feature, but that's definitely what it does. The trunk release button still works as expected in either case.

+00128 disables the constant blinking of the alarm LED by the lock knobs of the front doors. So when you lock the doors and arm the system, those LEDs will not blink continuously. This makes sense with +00002 - Anti-Theft Confirmation via Blink. If you have +00128 and +00002 enabled at the same time, then the alarm LED will blink once when you lock the doors to confirm that the system is armed. If you DON'T have +00128 enabled, then +00002 becomes mostly meaningless because the light will be blinking as soon as you arm the system anyways. This is probably why most cars don't have +00002 enabled from the factory.

After all that, I still can't figure out what +01024 does. All I know is it was enabled on my car from the factory, and I have no clue what its purpose was. I just disabled it and will leave it that way for a while... maybe some difference will become evident eventually.

Looking at other Audi models, it appears that +01024 is usually Confirmation Anti-Theft Warning System Horn Activation. This is the case on B6 A4's and some (all?) A8's. So there's a very good chance that it applies to the B5 A4 as well. That would provide an explanation for every single possible coding option then. Here's a final list that's more complete than Ross-Tech's:

+00001 - Rear Lid Opening via Rear Lid Lock
+00002 - Anti-Theft Confirmation via Blink
+00004 - Selective Locking
+00008 - Anti-Theft-System
+00016 - Reverse Lock And Unlock Functions On Remote
+00032 - Locking via Speed (15mph)
+00064 - Comfort Closing via Remote Control
+00128 - Turn Off Continuous Blinking Of Alarm LED When Anti-Theft Armed
+00256 - Rear Lid Logic
+00512 - Remote Control "Close" Confirmation (1x Blink)
+01024 - Confirmation Anti-Theft Warning System Horn Activation
+02048 - Door/Window Logic (USA)
+04096 - Remote Control "Open" Confirmation (2x Blink)
+08192 - Remote Control

Just for clarification, +00032 also unlocks the doors automatically when the car is stopped and the engine is turned off.

Now... I still can't figure out why +00512 and +01024 stopped functioning on my car in recent months :(

I guess that concludes this single-person discussion. Thanks for your help, GoremanX! You're welcome.