This is misleading and should have been "CTP13 firmware makes it easier to feed your unit with the map data with virtually no checks".
The reason why I'm saying this is that I update Maps on my CTP16 unit with no downgrades. In CTP14+ Garmin rolled out their GMA protection of the maps, where GMA (as far as I understand) stands for Garmin Map Authentication and this mechanism replaces the unlock files.
To easily create an update USB stick for such a system the following prerequisites should be met:
- a compatible Nuvi device with current Map subscription (or its GarminDevice.xml)
- GarminExpress installed
- Basecamp installed
- MapInstall installed
- a spare USB (preferably USB 2.0, but not USB 3.0 compatible) of the comparable size to your map data (in Australia it's enough to have just a 1GB stick, but for the US it will be 8GB or more)
Now, launch GarminExpress and select Map updates, but choose to install to your computer instead of the device. This will result in Maps being unpacked and unlocked in Basecamp.
Go to Basecamp and under the Maps menu verify that the map is indeed there and has the "unlocked" status.
Insert your spare USB stick and launch MapInstall. Confirm that you want to install the map to the USB stick.
MapInstall will package the map back into the Garmin\gmapsupp.img on your USB stick, but will also put a GMA file next to the image file (the name of that GMA file looks like a GUID).
Eject the stick, and go to your car. When you insert the stick into your car it will go through the validation procedure (the bigger the map the longer the validation it seems) and once it's done you will be prompted to apply the update.
So far, this was the easiest way for me to keep my map up to date with no downgrades or whatever
Thanks mate - very helpful steps.
Initially I found the GPS/Nav in my 2012 (2013 compliance date) Chrysler 300 to be bit buggy so I told the dealer and they upgraded to CTP16 which solved the issue.
The problem then was I couldn't upgrade using the easy method any more but I worked out a solution in renaming gmapprom.img to gmapsupp.img which worked - but it didn't update the Junction View maps, in fact I lost Junction View functionality completely.
I've now followed your steps and I'm upgrading to the latest 2018.30 maps but I've noticed it dumps two GMA files to the USB and gmapsupp.img - that's it, no other files. So basically it's not upgrading Junction View etc, just the maps. At first it said the maps were incorrect when I plugged the usb into my car and then I worked out it was because I only copied the Australian maps, not New Zealand as well. Upon doing this, it's installed correct.
So I suspect the only way to upgrade everything, is to downgrade from CTP16 (and above) to CTP13.