Well, I just put in a mk4 DVD and the problem went away. SO it is obviously a problem with the CD/nav unit. has anyone ever taken one of these apart? I wonder if the memory is obvious and replaceable.

The flash memory is solderd on the pcb. You could replace it but you need to e.g. read out your old ones and flash the new ones with this data to keep the system alive. Otherwise you will end up with a repaired brick without SW.

I know I'm digging up an old post here, but I have the exact same problem with TWO mk3's. I find it hard to believe that I ended up with 2 failed units from ebay (although that could be why they were on ebay - both described as working fine).

I find it curious that you're seeing it with OS 3-1/41 as both of mine have that same OS. I couldn't get mine to update with burned copies, though.

Too bad to hear about your eBay experience.

I couldn't get mine to update the OS either. I used an OS CD that updated my DVD NAV just fine so I think I eliminated a possible bad OS CD as the problem.

I went so far as to take apart my Mk3 to see if I could replace the memory, but it wasn't obvious to me which chip was the memory. I'd have to look up a bunch of part numbers. I was hoping to get a bad unit from somebody to try some parts swaps (along with research on part numbers.) no response to that request yet.

I'm still hopeful this is a s/w problem. I don't think it's the memory chips because it's not resetting to a blank/default state. The prior owner's info (VIN, last destination, etc.) shows back up after a power cycle. That's got to be stored somewhere in the unit.

Also, every single time I've seen this problem, the units were running 3-1/41 version of the OS.

Have you ever tried updating (or downgrading) from an original BMW OS disc rather than a burned copy? That's what I'd like to try next.

No, I just have tried a burned disk, not a BMW original, but I doubt it will make a difference. I have tried to access the Mk3 via the Ibus to see if I could do something with NavCoder, but found nothing.

I tried to change the second language with NavCoder and the OS CD, but it didn't take. It just doesn't seem to want to read the OS disk.. It reads the maps just fine.

I've recoded mine with DIS. After coding, I can go into the secret menu and see that my VIN has made it over to the unit. It, too, reverts back to the PO's VIN upon restart, and that's what's puzzling me. I think it's a software glitch that's failing to write everything to non-volatile ram upon shut down. The nvram is there and has info stored, it's just not being replaced.

I've also read something in a BMW tech bulletin about MK3's needing a configuration signal from DIS in order to load an OS, but that only seems to apply to a brand new unit without any exisiting coding info present.

I'm hesitant to "break the seal" on mine until I've exhausted the last potential software fixes (try upgrade/downgrade with original BMW disc).

The info is stored in a nvram inside the nav unit.

The memory is located on the main board beside the carin processor chip, and inside the metal shield. Remove the nav lid, then remove the DVD drive, then remove the metal shield to see the memory chips. They are SMD (surface mount) and very hard to remove without the right tools. If you haven't got tools to desolder every pin at the same time, and at the right temperature, then do not try it! You'll damage the circuit board.

There is a diagnostic command to write settings to flash ram, my NavCoder issues the command once it has finished changing the settings.

However, if the flash ram (nvram) is loosing its memory when powered down, then the flash ram is faulty. It is not retaining it's memory contents.

This is a common problem with old flash ram - it happens. And the only way to fix it is to replace the flash ram chip.

Siemens VDO will most likely be able to replace the flash ram for you, send to Siemens VDO in Wetzler Germany.