I used a program called gimgunlock.v0.03 which I found with a google search.. ... I backed up the card and used gimgunlock to unlock the 2016.20 maps I have from my Garmin GPS with lifetime ... Found an image file, thanks.

Step 2: The gmapprom.img and gmap3d.img files should be manually unlocked before they go into the car using gimgunlock.exe. (See links at bottom for garmin image tools) To unlock the two files, simply drag-and-drop them one at a time onto the "gimgunlock.exe" file using your file explorer. It will only take a couple of seconds to unlock both files. A command window will flash by, so fast you may miss it if you blink.

Gimgunlock V 003