First try the rgn41 backup:

  • Prepare the usual stuff for SD NV backup but don't have ldr.bin in the Garmin\Updater\1138 folder, only the update.txt file in there. Insert the card into the nuvi with it fully OFF
  • Patch the boot.bin in hex by replacing bytes 0C 80 A0 E1 at the beginning of the boot.bin with 0C 80 A0 E3. Read this first: [Only registered and activated users can see links. ]
  • Open the patched boot.bin in RGN_Tool and press the RGN button to save it somewhere convenient on your PC [not on the SD] named 113801000300.rgn only
  • Drag the RGN onto Updater.exe, blah blah [you know the rest] and flash it
  • You'll have bin file backup of 41 on the card if it works.

I have no idea if that will work with a bricked unit with cure fw onboard which won't load ldr.bin normally. It can't hurt anything so you can be a guinea pig.

For packing fw_all.bin, see: [Only registered and activated users can see links. ]. If you're not happy using command prompt, make a file with Notepad using 'gfwpack.exe pack fw_all.bin' without the quotes and save it as pack.bat [not pack.txt.bat], or you can save it as pack.txt and then rename it pack.bat if you like. Put it in the same folder with gfwpack.exe and the zumo's fw_all.bin then run it by double clicking it.

Make another rgn file named 113801000300.rgn using the original unpatched boot.bin and the packed fw_all.bin and try to flash it in preboot. Dunno if it's been tried before in nuvi 5x0/zumo 2x0, kunix advised that nuvi 6xx and 24x4/25x5 are a no-go so it might fail regardless.

I hope that's detailed enough for you old Son, good luck!