Thread: Nuvi 66LM firmware rollback

Generic general guide for rollback to a previous fw version:

• Connect your device to computer with , look in ".System" folder, delete the file GUPDATE.GCD if present [in older devices without .System it's in the Garmin folder]. It's not always present for instance if device as been previously updated in preboot with Updater.exe and particularly if device still has its factory loaded firmware, i.e. it hasn't been updated since. [See below*].
• Download your preferred fw version from [Only registered and activated users can see links. ], or if your required version is not there look at perry site:
  Code:

  Please Login or Register to see the links

• Usually the firmware will be a *.gcd file. Open it in [Only registered and activated users can see links. ]and press the 'RGN' button to save it in this format: XXXX01000xxx.rgn where XXXX is your unit's HWID [look in Garmin folder for GarminDevice.xml to find "<PartNumber>006-BXXXX-00</PartNumber>" e.g. 1749] and xxx is the version [e.g. if it's V3.20 use '320']. 174901000320.RGN for example.
• Open the rgn file in [Only registered and activated users can see links. ] and leave the GUI open and visible on your desktop, with the radio button beside 'USB Device' selected.
• Connect your device in preboot mode, see [Only registered and activated users can see links. ]. Watch for the device details to be displayed in the window adjacent to 'USB Device' and immediately press 'OK' or hit Enter key on your kb. If you've entered preboot by holding the screen, keep holding at least until 'Loader' appears. Allow the process to complete fully and reboot. Check the software version has been downgraded via it's 'About' screen or in GarminDevice.xml after reboot.

IMPORTANT: Before upgrading or downgrading fw, always backup the unit's internal file system [or if you have an earlier recent backup at least your favourtes to restore later if required] and it's [Only registered and activated users can see links. ], and both before and after you should [Only registered and activated users can see links. ] or at least [Only registered and activated users can see links. ].

*Some modern devices need to be set to Mass Storage Mode and Windows folder options need be changed to see hidden files and folders, read this: [Only registered and activated users can see links. ]. If your device has original version fw as OEM which is also the latest version then it's not possible to roll back, nor is it possible to roll back to the earliest OEM if a copy of it isn't available as a final [Only registered and activated users can see links. ].

"<PartNumber>006-BXXXX-00</PartNumber>"
XXXX part only is HWID

[Only registered and activated users can see links. ]

Originally Posted by tattooman

quick question in GarminDevice.xml is version number <SoftwareVersion>430</SoftwareVersion> .........

Yes, it's the Unit Software [aka firmware] Version number without the decimal point. "<SoftwareVersion>430</SoftwareVersion>" displayed in GarminDevice.xml means that the device is currently running V4.30 firmware.

do i need add it to rgn name or version number of Nuvi65&66_220.gcd firmware file example 174901000220.rgn? ......

You should name the rgn file exactly as explained in Post #2. The last 3 numbers are not so crucial but are helpful in identifying the content of the file. If the first 4 numbers do not coincide with the unit's actual HWID, Updater.exe will return a message saying there are no updates for your unit as protection against flashing firmware which isn't suitable for the unit. The middle '01000' determines if the HWID identification occurs, it it is absent or even lacks 1 of those 5 numerals the flash will occur without regard to compare of actual unit HWID to the HWID in the intended firmware so it's crucial that the naming convention be respected. For example, naming of OUT.rgn is commonly used for purposes of cross-flashing by advanced users to easily identify such a 'non-complying' rgn file resulting in the HWID of the recipient unit being changed [rather than naming of XXXX0100xxx for instance, as the lack of a zero might be easily missed]. Unless you know exactly what you're doing you should never use any other naming convention than XXXX01000xxx.rgn as per Post #2.

Also do i need change software version value in xml also?
........

Absolutely not. The xml is rewritten by the device upon every reboot anyway. Any change you make would be temporary therefore. These are other reasons to do it however which are totally unrelated to the specific matters here.

@tattooman
Reportedly according to [Only registered and activated users can see links. ] if you have V3.40 or earlier there is no problem with map sig when maps are unlocked with the latest gimunlock [0.03+MapSigPatch]. Try downgrading to v3.20 but first check in the current GarminDevice.xml that the previous attempt was in fact successful and it's now showing "SoftwareVersion>340</SoftwareVersion>" not "SoftwareVersion>430</SoftwareVersion>".

To downgrade firmware easy method:
Plug nuvi USB, look for garmindevice.xml, change <SoftwareVersion>430</SoftwareVersion> to<SoftwareVersion>280</SoftwareVersion>. Save
Don't unplug nuvi from pc.
Having Garmin Webupdater on pc desktop, drag&drop in it [Only registered and activated users can see links. ] flash firmware.

I personally dislike that method because i've bricked the odd unit here and there [no problem to cure them, but it's a hassle for new users]. I've never bricked a unit using Updater.exe and correct XXX.01000.xxx.rgn naming however. Maybe tattooman forgot to remove an existing GUPDATE.GCD file from .System [as said in Point 1 of P#2] which would flash it back to V4.30 on reboot. At least the WU method with doctored XML file overcomes that potential trap and admittedly there's really little chance of bricking with using gupdate.gcd file anyway.... [but it's there regardless ].