Yeah the "T" word here gets more adverse attention than a fox in a henhouse.
This is now seeming to be a more complex problem than a simple soft-bricking caused by a corrupt file which can't be loaded during the boot process.
The behavior you're seeing is worryingly indicative of physical flash damage affecting an essential firmware region, probably region 14 (0x0E) which is absolutely essential for not only normal operation of the device but is also needed to load essential files during bootup as well as executing the loader to start the boot process. Flash damage would explain why Cure3 fw can't be properly loaded too, because if firmware regions can't be overwritten during a flash then corrupt region data is permanent and cannot be corrected by 'soft-methods'. The fact that Windows is reading it in Device Manager as an unknown USB device isn't encouraging either, it should identify itself as GARMIN Device when connected to a PC in preboot.
Let's not give up just yet however. Sometimes severe corruption in one of the firmware regions can mimic flash damage although usually that's corrected by flashing an original fw RGN in preboot. One way to be sure is to use a ramoader (aka boot.bin/Ldr.bin) modified so that it doesn't rely at all on the firmware to initiate a flash. Seeing you have already looked into the modified boot.bin method you likely do understand the reason why we should try that. Please follow the following guide exactly:
- In a hex editor open boot.bin, find the first instance of 0C 80 A0 E1 and change E1 to E3 in that string. Save the change.
- Open the modified boot.bin in RGN_Tool and save it as an RGN file (use only safe naming of 194701000880.rgn), put it aside for now.
- Make a common text file with Notepad, you can copy and paste the text in the coded box below but make sure there are no additional spaces at line ends or carriage returns in it after you save it:
Code:
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- Save the file as update.txt.
- Open the firmware file "nuvi25x9C4_880.gcd" in RGN_Tool and save the last 3 sections as 7F.bin, 9E.bin and 0E.bin respectively, naming the BINs after their region hex names and taking care not to mix up the naming (and note "0" is zero). See image below for reference:
- Prepare a small microSD card, preferably no bigger than 8GB ensuring that it's freshly formatted FAT32 and make a root-folder named Garmin in it. In Garmin folder make a sub-folder named Updater and in Updater make another named 1947 (i.e. Garmin\Updater\1947).
- In the root of the card (with, not in, the Garmin folder) copy 7F.bin, 9E.bin and 0E.bin.
- Place update.txt file in the 1947 folder. There should be nothing else in that folder.
- Ensure the device is fully OFF, hold the power button down to force it off if necessary, then insert the microSD.
- Open 194701000880.rgn in Updater.exe, select the radio button for "USB Device" and position your mouse cursor over the OK button of the GUI.
- Connect a 'known-good' USB cable to the PC, plug in the device and place it in preboot watching the window next to "USB Device" and IMMEDIATELY it becomes populated click OK on the GUI or hit the Enter key on PC's keyboard to initiate the flash.
- Keep holding the screen firmly until you receive a popup message from Updater.exe, hopefully it shows that the flash completed successfully.
If that fails please post a copy of the text in "update.log" if it has been generated in 1947 folder.
An explanation of the text commands: The first one will delete a GCD file from the device if there's one present. The second will save a copy of the device's non-volatile memory as a BIN file into the root of the microSD card. The 3rd, 4th & 5th will attempt to write good data to the device's 3 firmware regions. Final one will attempt a reboot.
Good luck. Ask in advance if you're unsure of anything before doing this and be aware it's all at your entire risk although i've been as careful as possible in my instructions. It shouldn't make anything worse however. If the read/write command/s fail/s it will definitively show physical flash damage.
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