I’ve got the MMI blues. For the last 2 months, I’ve been cruelly taunted by the MMI startup/welcome screen when I start the car–only to see it completely shutdown after a few seconds. Nothing connected to the MMI system works. Even worse, I can’t even use the MMI controller to change the time on the dash clock. Furthermore, if I sit in the car for a few minutes with the car on/engine off, I am again taunted by a short burst of radio music–probably caused by a MOST heartbeat that can’t find a satisfactory answer. Then silence. It’s maddening to know many individual components are working, but the whole system is dead.
All because I somehow got 1/2 inch of rainwater into the front passenger/right footwell (for a brief history, see: http://audirevolution.net/forum/index.php?topic=4681.0). It may have come from the sunroof because i notice the leather shift boot is dry and cracked as if it suffered from water damage.
As it stands, I get a flash of a welcome screen on engine start, and an occasional burst of radio music with the car on/engine off. But no MMI buttons or controller knob.
I read online that this behavior seems to suggest a break in the MOST component ring.
From SSP286 p36, http://www.volkspage.net/technik/ssp/ssp/SSP_286_d1.pdf
"System start (wake-up)
If the MOST bus is in sleep mode, the wakeup process initially switches the system to
standby mode. If one of the control units, with the exception of the system manager, wakes the MOST bus,
it transmits specially modulated light – slave light – to the next control unit. By way of the photodiode which is active in sleep mode, the next control unit in the ring receives the slave light and passes it on.
This process continues right through to the system manager. In the incoming slave light the manager recognises the prompt for system starting. The system manager then transmits another specially modulated light – master light – to the next control unit. This master light is relayed by all control units. Reception of the master light in its FOT informs the system manager that the ring is complete and frame transmission commences."
4F S6 MOST component sequence for 2007 S6
- J523/control unit
- J525/DSP amp w/BOSE
- J533/OBD2 diagnosis interface
- R41/CD Changer
- R36/BT module, Telephone transmitter
- (not installed???) J526 Telephone/Handset
- R/Radio + J507 Voice input
- J401/Nav w CD drive
I also read that you can do a diagnostic scan of the MOST components to identify a component failure. Has anyone ever done this?
Also, my driver “memory seat” isn’t working like it used to–front/back adjustments ok, but not up/down. Same with steering wheel adjustment. However, the diagrams don’t suggest this has anything to do with the MOST ring. But water damage?
Driver Seat controller diagram
- E97/memory switch for driver seat
- J386/door control unit for driver side
- J136/control unit for seat + steering column adjustment
Best case scenario, I find someone to do a MOST diagnostic scan and discover a failed component. I already checked the BT module under the driver seat, but replacing that with a loopback connector did not solve my problem. My next guess is the MMI Interface Controller (J523/PN 4E0 035 729A).
https://www.ebay.com/p/2007-2008-AUDI-S6-MMI-Interface-Control-Module-4e0-035-729a/2272613008
But before I start blindly buying an replacing components, I thought I’d ask here.
Any suggestions?