question on upgrading MKIII to IV
 

I searched but could not find the answer to this.

I just took the plunge and purchased a MKIV (6590 6 942 908-03)
from naviandbmwparts on ebay. This unit should be a plug and play replacement for the MKIII in my 02 X5, however do I need to disconnect the battery before exchanging the units.

Thanks.

Just swap the drives- no need to disconnect the battery, but do take the key out of the ignition!

It never hurts to remove the power, but to be honest with you I have removed mine more times then I can count and have never disconnected the battery first.

The MkIII is very finicky on this stuff, though, so be sure the drive is totally inactive before either removing the power or disconnecting the cables. It's best to wait about 20 minutes after any vehicle activity (including opening or closing a door) for the i-bus to go to sleep before doing so.

Thanks, I appreciate the info.