Update: Some 2013+ radios seem to need unlocked maps. Since you cannot manually enter an unlock key like the 2011-12 radios, I suggest unlocking the maps (gmapprom.img & gmap3D.img) using FastImg Unlock or similar before installing. It only takes a few minutes to unlock a map, but it sucks to spend an hour or more babysitting an install only to get a "Maps Cannot Be Unlocked" error at the end.
There are also some folks who have reported troubles updating. I cannot stress enough how difficult it can be to find a compatible USB stick. For some reason, it is very difficult to find one that is 100% successful. This method DOES work, but you may waste a lot of time finding that magic USB stick. Just because it can copy 50% of the update does NOT mean it will be able to finish and it's best to just try another one.
And, really important now, do NOT let your car turn off when performing the update!!!
I'm posting this method, even though it is technically probably against the Terms of Service for the Garmin maps. I personally feel that it's a gray issue, since I don't actually use my nuvi for anything but map harvesting, and also because the maps that we're provided with via the official channel are not current. The update disk just released is already 6 months old, and the version that comes in the new cars is more than 1.5 years old.
If we were able to purchase a lifetime subscription for the maps, I'd jump on it.
Install Garmin Express and let the program update your nuvi to the latest version for everything, including maps. Just skip the registration for now.
After it's done, go into the nuvi and enable the USB Mass storage mode by:
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* This is on the nuvi, not the car *
1) Go to the main screen with the "Where To?" icon and tap the "Volume" icon.
2) Press the upper-right corner for about 7 seconds, and the "Diagnostics Page" will open.
3) Scroll down to the "MTP Settings" and select the "Mass Storage" bubble, then tap the "Save" button.
4) After this is done, the nuvi will show up on your computer like a USB drive, and you can select all of the files and back them up to your computer. Otherwise, it will function exactly like normal. You will not have to go into this menu again. For good measure, select everything and copy it all to someplace safe on your computer.
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Installing maps to the USB stick:
1) Get a blank USB stick that is at least 8GB, and create a folder on it named "Garmin".
2) Go into the "Garmin" folder on the nuvi or on your computer (if you've backed them up) and copy the "GarminDevice.xml" file, then paste it into the "Garmin" folder that you created in step 1.
3) Disconnect your nuvi - you're done with it. Use it, or put it in a drawer until the next map update.
3) Make sure that Garmin Express is closed. There may be an icon in your Notification Area by the clock on the bottom-right of your PC screen. Right-click the icon and select "Exit".
4) Remove the USB stick.
5) Open Garmin Express, then plug your USB stick back in.
6) Garmin Express should recognize the USB stick and treat it as if it were a nuvi, which will allow you to reinstall the maps. This will not take as long as the first time, since the files were already downloaded onto your computer. This time, the maps will be installed directly onto the USB stick.
7) Make sure you have "Show Hidden Files" and "Show System Files" enabled on your computer.
8) After Garmin Express has finished installing the maps onto the USB stick, delete the "GarminDevice.xml" file from the "Garmin" folder.
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Preparation for loading the maps into your car:
*2011-2012 method*
1) Make sure that the "Garmin" folder on the USB stick is empty.
2) Browse to the ".System" folder on the USB stick and move the following files to the empty "Garmin" folder:
gmapprom.img
gmaptz.img
ASR folder (should contain 4 .asr files and 1 .srx file.)
JCV folder (if you want JunctionView added) (should be 1 .jcv file)
Do NOT add any other files to the Garmin folder!!!
*2013+ method*
1) Make sure that the "Garmin" folder on the USB stick is empty.
2) Browse to the ".System" folder on the USB stick and move the following files to the empty "Garmin" folder:
gmapprom.img
gmaptz.img
gmap3d.img
ASR folder (should contain 4 .asr files and 1 .srx file.)
JCV folder (should be 1 .jcv file)
SID folder (should contain 4 .sid files)
SQLite folder (should contain 1 .db file)
Do NOT add any other files to the Garmin folder!!!
3) Delete the ".System" folder along with any extra files that it contains.
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Loading maps onto your car:
*2011-2012 Method*
1) In the Navigation settings in the car, find the Device ID for the Garmin module. It's probably in the "About" screen somewhere. It will be a 10-digit code - write it down.
2) Install a program called "GMapTool" onto your computer - easily found via Google.
3) Open GMapTool, then drag the "gmapprom.img" file in the "Garmin" folder on the USB stick into the empty box in GMapTool under the "File name" header.
4) Click the "Info" button in GMapTool.
5) Just above the "End." line at the bottom of the information window, there is another line that starts with "F:" in that line, there is a 4-digit number after "FID". Write it down.
*This number is unique to each new map update. For simplicity sake, I'll just tell you what it is for 2014.40 North America maps - "3187".
6) Via Google, find a program called "Garmin Keygen v1.5 + CF" by Jetmouse.
7) Run that program, then enter your 10-digit Unit ID in the top box.
8) Under the "Select Map Product:" pull-down menu, select "<custom mapset>"
9) In the new window that pops up, enter the 4-digit FID number that you wrote down, then click "OK".
10) Click the "Generate" button in the bottom-right corner. This will generate the 25-digit unlock code that you will need to key into your car. Write it down.
*2013+ Method*
No unlock code necessary.
11) Turn the car on. The engine does not have to be running; you can install the update in the "ACC" or "RUN" position. Note that you cannot simply start the update and walk away. It may take up to an hour, and your car will turn itself off after a period of time. Cycling the start button around the different modes is fine, but make sure that your doors are closed so that the radio doesn't turn off!
12) Select the Navigation screen, then plug in the USB stick into the jack in the center console.
13) The validation process will begin. The files on the USB stick can take up to 20 minutes to validate.
*At this point, it is common to get an error the first time you do this. It is almost always due to an incompatible USB stick. It sounds bad, but the system is VERY picky regarding USB sticks for the updates. It might take you a few tries to find one that works. When you find one, put it somewhere safe and just use if for map updates.
14) After validation is completed and everything checks out, a window will pop up to notify you that it has detected new maps. Choose to install the update.
15) *2011-2012 systems only: Another window will pop up and display the Device ID button and prompt you to enter some codes online to get your unlock key. You've already generated it, so continue to the next step.
16) *2011-2012 systems only: Enter the 25-digit code that you wrote down earlier, then continue
17) You will be notified that it may take up to two hours to install the update. Proceed with the update.
18) The system will reboot, then the map update will start copying over onto the system. Make sure that the car does not turn off, or you will have to start over!
***Occasionally, the system will not complete the reboot process. If it does not reboot within a couple of minutes, you will need to pull the radio fuse in the trunk to turn it off. It rarely happens, and after you put the fuse back in, you can simply start over.***
19) Allow the system to complete the update. When the progress bar reaches 100%, it will remain there for a few minutes. After that, the radio will reboot again.
20) On 2011-2012 systems, you may get a prompt that tells you that the maps were installed successfully. On 2013+ systems, I've ALWAYS terminated with a "30A1" error. Do not worry, the maps were successfully installed regardless of what the system tells you.
20a) It is common that you will get a screen that says that the maps were not updated successfully and go to a dealership. It shows up on some radios and does not on others. I blame the uConnect software. Do not worry, if you've gotten this far, your update was indeed successful.
21) When the system reboots, the Nav screen may be black. Simply tap another icon on the bottom of the screen, then return to the Nav. It will then display properly, and you can check your map version in the settings to verify that it was updated.
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Troubleshooting tips:
*If you're having trouble finding a USB stick that works, you can install an abbreviated mapset to speed the process up until you find a good match. You can update just the map by itself by only having the "gmapprom.img" file in the "Garmin" folder. This will make the validation process and map loading much faster. Once you can successfully load that file by itself, copy the rest of the files over and start over with the full set.
*An alternate method of putting the maps on the USB stick is to simply copy them from the updated nuvi's ".System" folder. This may be easier than letting Garmin Express install the maps to the USB stick. Use the method that you prefer.