Hi,
I have a nuvi 57lmt garmin gps just like felipehokama. I tried to click the link for patched Gupdate.gcd you gave him but the file is not available anymore https://files.fm/u/xpkkyh3v. I am kinda newbie here and would be glad if you could help me upload unlocked maps to my garmin gps. Please help! It always gives me "cannot unlock maps errors" and "maps are corrupt and cannot be used" when I tried to open it with my micro sd with maps images installed.

There is a danger to use a firmware that is not the proper for your device. Please patch your own Gupdate.gcd should exist usally in .\system hidden directory.

how can i access.\system directory of nuvi 57lmt?

You put your device in mass storage mode then change your windows settings to show hidden files and connect your device with a USB you will see .system directory

I was able to change to mass storage mode and click hidden files settings on my file explorer but still couldn't find .system directory. I however open xml file and this is the info..
<PartNumber>006-B2087-00</PartNumber>
<SoftwareVersion>440</SoftwareVersion>
<Description>nüvi 57</Description>
</Model>
<Id>3929739126</Id>

In my back up file I was able to access system file and this is what I got data base file D4955120A inside SQlite folder. Thanks!

So finally you discovered or not the Gupdate.fcd file? If does not exist re-update your firmware with Garmin Express and the file will appear on your device!

I re-updated and still could not find the gupdate file.

Based on these device info <PartNumber>006-B2087-00</PartNumber>
<SoftwareVersion>440</SoftwareVersion>
<Description>nüvi 57</Description>
</Model> will you able to give me a patched gupdate.gcd. I really couldn't find one in my device. Thanks!

I will send you PM in few miniutes

PLEASE HELP! UPDATER ERROR INFO:

App: Updater
At: 4/3/2017 1:14:03 AM (UTC)
OS: WIN32 Windows Platform, Major Version: 6, Minor Version: 2
Processor: Pentium Pro or Pentium II, RAM: 2097151 KB
XFERTHREAD.CPP-1101-2.8

Please explain when this happens!

i'm having a similar problem. I have not updated any maps on mine since late last year. finally did it and now all of a sudden i'm getting "cannot unlock maps" on it....but only sometimes. i did not update any firmware so i suspect something else is going on. The wierd part of the "sometimes" is i can't figure out a pattern with it. AT first i thought i didn't unlock the map. It's an older one without gma so i just ran the same img unlock on it. put it in and error. I combine a whole bunch of different products and max out the 4G limit. so then i thought my sdcard crapped out and bought 2 more. same problem. I've built many many map files so it's not 1 bad img. Then I tried to narrow it down to which map product was giving me the error (I don't know because i combine about 10 different map types, all older, all have worked up to this point) The weird part is i built an entire map for the latest cnna which i suspected first since it's the only new one i've never used before. sure enough, the whole map works. It's when i combine maps that it suddenly starts to craps out with unlock messages. very strange. I started building random groups of map products and some work, some dont...i just can't seem to narrow it down to which one is causing the error, or maybe it's something else.

Oh, and the real kicker is now when i put the previous img file back in, it no longer works and i get the unlock error. go figure that one. Other than this, strange behaviour, the gps works just fine when it has a map in it that it didn't report an unlock error with

Sorry but all this that you describe is too complicated to understand! First you should upgrade in the last firmware to be sure that it support big files and SD cards after i will propose to you to patch the firmware but you do not mention not even your HWID
Finally when you use gmaptool to create combined maps sometimes the result is not the proper one i propose to avoid to do it.
Details i am sending on PM to you