MP4.2+6.0

I don't know the system at that kind of level, but in the older C5/D2 type system that suggests a faulty speed input (same as the "GALA" wire in those older systems, which would be like "AudioPilot" in the BOSE world). If similar, not hearing the sound amplification go up at speed (or more likely, drop as you stop quickly) if you have that enabled in the Sound settings would be another indirect clue, assuming it gets the speed signal from the same place.

Thus, you might look at a Bentley type manual and see where that signal originates and then how it connects to the Nav system.

MP4.2+6.0

1. Per your other e mail, the radio related fault seems a bit odd. You might try to clear that, and look at the VAG COM screens for the coding to be sure it is right.

2. Your MMI console controller board experience seems like a definite clue. You are getting to the point where it may be trial and error (and that board is expensive). But since it did improve when you cleaned it, that seems like a leading clue. I see those things sold on e bay occasionally, though hard to know the quality.

Kebabian

The only thing I found related to the DTC with the sound system is referenced in TSB 91-05-15. I've attached it. I don't really understand a whole lot of it. If you have time, have a read.

As far as the MMI unit itself. I gave it another clean, still no change. I found a new one for $450, so I'll keep that as a last resort.

You did mentioning the microphone system. Not sure if that is used in the NAV system, but one thing I did notice was that I get erratic behaviour with the Audio Pilot on. The exact symptoms are referenced in TSB 91-05-11. Also attached.

I'll head to the dealer to see if they can help with the TSBs.

MP4.2+6.0

No idea on the old V60 phone stuff. I moved away from Audi phones after the C5 analog.

On the AudioPilot, again the overlap I was thinking about was the speed sensor coupling that is likely one of the inputs to the system that regulates sound volume. Don't recall if it uses a microphone pick up too or in lieu of the speed sensor approach. On that TSB my casual read is it is talking about incompatibilities introduced by changing some components without the right updates. You might check all those rev levels it discusses. It refers to an update CD at one point too if you want to bother and find an incompatibility from what they are mentioning.

I went back to your earlier answer about upgrading the MMI s/w. You say you went from 0600 to 4140. Did you pass through 3360 on the way (and maybe other earlier updates), or go straight to 4140? If you went straight to 4140 without passing through 3360, that's a likely very big problem from prior posts--two reports of melted down MMI's. And, when you did 4140 even if you passed though 3360, did you do it using Audi's instructions where you have to check some configuration settings. If not, you should check that using the 4140 instructions.

By the way, if you have a friendly dealer who would run out the whole service history on the car, you might learn something, like history of replacing that MMI board or antenna components or something.

Last question: I forget if you said it was heat dependent. If so, that could eliminate all the s/w type issues and narrow it to a connection, the antenna or a control unit.

Final idea: Search the archives for both the C6 A6 and the Q7. Both use MMI and are much higher volume than the D3. Maybe you will find posts there dealing w/ your symptoms.

Kebabian

Even the dealer has no clue what it is.