Thread: Nuvi 58LMT "can't unlock maps".

Good outcome! Thanks for unravelling this mystery GN.

I agree that we could have easily solved this problem as janch said by guiding Stevex in patching the firmware with big-bang's "Universal Firmware Patcher for Protected Garmin Devices" (cough cough....Masters' Zone - if you know you know) and then unlocking the UK/ROI map IMG provided thru GE by simply stripping out the need for both GMA and UNL files with "gimgunlock-v0.04.exe" (a simple google search will find that everywhere too - but not here). But where's the fun in that anyway? Here we have a rare case of a practically unknown version of a device with an unusual problem and an owner with the technical skill and innate curiosity to want to find out how and why the problem has actually occurred. Also, Garman_Nuvi has hit the nail on the head, got to the actual source and by having a similar Travel Edition so was able to replicate the anomaly - i think he's got many dozens of Garmin devices and all the boxes they came in too ...

BTW, we can chat all we like about that hacking stuff here, in general terms anyway. Garmin's already had its revenge by decimating this forum 8 yrs ago, but even then those cats were well out of the bag and what was started by this very forum in the West had already spread worldwide when we got 'hit'. It's only against the updated Rules in this Forum if we again start making patched fw kits for users or openly post the tools to do that - regardless those things are clearly against Garmin's EULAs for both fw and papping data use, they're now done on various other similar forums who didn't get penalised like us at the time.... Rant over ....

I agree with GN that Garmin's simply overlooked the case of UK/ROI and made an error when they changed regional EU entitlement to full EU for Travel Editions. That's evidenced seeing his Drive 50 Travel Edition has the same problem. It's also a UK market device going by the box's image. Certainly UK/ROI should have been an exception from the regional change to full as evidenced in Garmin's own announcement, i.e. That "Southern Europe" and "UK & Ireland" are still available as standalone entitlements.

@Garman_Nuvi
Are you able to confirm or refute the following please mate? My unsure memory is that the "Travel" models were NOT offered the option in GE of installing a GMAP folder to a computer so that smaller sections can be transferred to a qualifying device via MapInstall, in this case i'd like to see that tried with all or some of UK/ROI.

Anyway, i'm sure you have access to an unmolested GMAP for 2026.20 EU to try that out on your Drive 50 Travel Edition. Would you like to see if it correctly loads the proper GMA & UNL codes that way?

Nothing GN did was even vaguely against the rules or even Garmin's EULAs if what i think he did is correct.

I reckon he simply used your XML on an SD or thumb stick to download full EU with its associated files, including correct UNL and GMA files appropriate for your Nuvi 58. It's only when you try to dl solely UK/ROI that the codes are cooked. Please correct me if that's not right GN.

Originally Posted by stevex

Within the limitations of the forum rules I'm curious as to what precisely went wrong and how it was fixed.
I gather the Garmin server is sending back a bad unl file for certain models. Is that a recent thing and if not why did it work fine until a few days ago?
I can fill in some of the blanks as to one way GN might have diagnosed the problem using the GarminDevice.xml file.
The one question I'd really like to know the answer to (and which may not be answerable here) is what the fix was and how it worked. It certainly did something interesting.

Neil is right.
Once I had your garmindevice.xml I could have a play around to see if the unlock codes where valid, they where but Garmin's server did not pick up the Family ID to create the code for the 2 regional maps UK & ROI and Southern Europe. I check the error was repeated on a couple of other Traveler devices I have to prove it was not your specific device. All the other maps available received their correct unlock codes base on their FID as they were present.

I've not actually fixed the problem only Garmin can do that, all I did was identify and choose another download option I had checked would work for you , giving you Full Europe which includes coverage of UK & ROI.
It's quite possible that the working .unl & .gma files could be used to unlock UK & ROI as they share the Family ID, but why bother "if it ain't broke don't fix it"

Spoiler: Family ID

Well once it was working I of course backed everything up or thought I did...

Being a curious fellow and now knowing a little bit more about unlock codes I started playing around and something strange is now happening. The older (pre-fix) backup I tried is now working with no errors. Reinstalling the map with GE now works.

Presumably the device is caching the result of the previous unlock and doesn't think the map has changed so doesn't see that the .unl file is bad and needs something to trigger it to decide the cache is no longer valid and try to unlock (and fail) again.

It's not storing that cached unlock in the filesystem because I replaced the whole thing from the backup. What am I missing here?

What was the other download option that worked?

I'm just trying to work out exactly what is going on so (maybe) I can fix it myself in future and don't have to bother you all again

Oh and rather ironically when it wasn't working I did try changing the region to... Southern Europe. Anywhere else would've worked and I might've been able to save the lives of a few kittens (lovely image btw) when I contacted Garmin support.

Originally Posted by stevex

What was the other download option that worked?

I tried the smallest for speed
Australia & New Zealand 2026.20 (dropped yesterday)
Southern Africa
Full Europe as you know
Take a look at where Garmin Express downloads the files before installing and unlocking on your device.
C:\ProgramData\Garmin\CoreService\Downloads\Map\Map_Map.AUTOWW.2026.20

So you are now able to load UK & ROI on your device with Garmin Express without errors ?
If you are I would be interested in comparing the garmindevice.xml 's if you want to pop the latest one into my [Only registered and activated users can see links. ] like before.

I did send a PM yesterday.

Here's what I've observed so far which has led me to my confusion and caching theory...

Before your fix, errors I mentioned happened with everything I tried which included changing to Southern Eurpope maps (via GE change map option) then back to UK. I never tried any other region.

After your fix everything worked again and I backed up the whole thing or the whole filesystem anwyay.

Since I live my life by the rules of [Only registered and activated users can see links. ] I couldn't just leave it there.

I wipe the internal drive and copy the non-working backup from before the fix and it worked. No errors on startup. OK, weird. I try reinstalling the UK map with GE. Still no errors.

I then as an experiment use GE to change the map to Southern Europe and the errors are back. Change it to North America and all is fine again.
I change back to UK version and get the same errors.

I apply your fix and everything is fine again.

I was assuming that was expected behaviour and was due to some unlock cache somewhere? I notice that the first startup after region change is much longer as though it's doing some additional checks on the first boot.

Update: oh... only wiped the main drive and not the stuff in RWFS. That's presumably where it stores the additional information

I can't say for certain that any .unl code info is not stored somewhere in RWFS, but not as far as i know.

Garmin devices certainly store both critical and non-critical information in the non-vol region (154 for your device). Some of that is temporary (can be cleared via the device settings in the Diagnostic Page menu). Some other info, specifically that which is unique to the device cannot be "cleared" as before, but it can be fully erased and that may also include other info gathered by the device (we don't know for sure). The absolutely unique critical info is also stored elsewhere on the device and it gets rewritten somehow to rgn154 when the device next reboots however other info maybe does not. In fact erasing non-vol without a backup to restore can result in a permanently crippled device which has lost some functions programmed at the factory and that effectively turns a senior fully optioned device into a junior less-optioned model. I know little more about Garmin's non-vol memory other than it's encrypted with simple XOR but even when decrypted I don't know how to permanently re-write data to it - maybe someone outside Garmin does but if so they've kept quiet. Seeing you've cleared NV previously i can comfortably say that either the non-clearable data in rgn154 is poisoned or Garmin's stuffed up with UK/ROI and Southern Europe subregions for these devices. However, seeing GN has been able to replicate your problem my money's on Garmin have stuffed up.

The reason the older UNL works with a newer version of the UK/ROI map is the same as why the properly generated code for the full EU supplied by GN works. The file contains the correct UID of course but crucially the correct FID of 12956 instead of "1" as in the GE supplied file and isn't dependent on the map version as such. You can try yourself, use JM to generate another random code for your UID with FID 12956 and i bet it'll work for your 2026.20 UK/ROI image file. The link is in Post #16.

Well I got the impression that the unl file (by which I mean .System/gmapprom.unl) was only being accessed when the map was installed and whatever it did with that information was kept somewhere else until it decides to reload for some reason. Changing the map region or using GNs fix are the only things I know of so far that do it.

I did a simple test. I removed .System/gmapprom.unl entirely (after backing up) and the thing still starts no errors and displays the right map. Same thing happens if I remove .System/gmapprom.gma. I did try renaming .System/gmapprom.img and then I get a brief white screen and no map showing on startup but no error either. If I rename it back (with no .unl or .gma) then it starts up again and shows the right map.

I downloaded and played with JM and InfoUC as soon as they were mentioned of course.