Dont qoute me as i dont have nav but been reading as much as i can on this since sooner or later im a retrofit it.. I thought the only reason you would need coding regarding the navigation is for DSP. Thats only the dsp amp to be coded to the car. Everywhere else I read that the unit from mk3 to mk4 is plug and play. Is the nav dvd you using scratched or non-oem/ Maybe the drive on that unit is going bad. Or maybe like you said it needs to be coded for your car. I just never heard of that though.

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E53 06 3.0i

wishlist
Comfort Seats
speckdock 2.5

Mods
Air suspension - wip
skid plate replica - in box
OEM sunroof deflector
OEM bluetooth streaming
navi,dsp,tv retrofit - wip
Low prof roof racks
2 directtv satelite tuners
Grom audio usb2
quarter and back window sunshades
2 10"subs- boxes opposite sides/Alp MRP-M850
rear heated seats retrofit
rear footwell lights retrofit
remote window roll up