Thread: Guide Unlocking Garmin MapSource City Navigator maps

Hello all,
Following my collection of Garmin GPS I just acquired a 276c. Updated to 5.70
It came with City Navigator 2008 and 2009 non nt original cds.
In a windows xp sp3 32bit machine I installed them, original code and no chance of unlock.
After some hours on old posts and specially this, found the map ids, found my id, used jetmouse and used Mapsource patched and with protected garmin toolkit, all is unlocked and I see them on mapsource.

When I transfer to the 276c via usb using mapinstall (4.0.4 patched) it says on the device it can't unlockfile.
Any one from the old times that have a solution?
Keep in my I can't acess the contents of the datacard on the 276c, since I don't have the datacard reader. I can only send new map to it.

I know I can use osm and I also have been playing with it, but would love to check it how it was before, and this will serve for a garmin quest that is on the way also.

Have a great day

So i think you're saying you've sent an image file to the 276c but it's not unlocked on the device even though you've previously unlocked the install files for MS. You need to also unlock the IMG file for the device, to do that either use JM to generate an UNL code for the 276c's UID or just google search for and use "gimgunlock.exe" on the IMG file (you won't find it here, against our forum rules to supply it).

Of course such old maps from 08/09 are about as useful as a hip-pocket in your underpants now. GPSMAP 276c can use latest Garmin NT mapping (not NTU smoothly though). It's not limited to the Old Format (non-NT) maps. Or use the open source OSM as you said, no need to unlock them and they'll work fine.

Originally Posted by Neil

So i think you're saying you've sent an image file to the 276c but it's not unlocked on the device even though you've previously unlocked the install files for MS. You need to also unlock the IMG file for the device, to do that either use JM to generate an UNL code for the 276c's UID or just google search for and use "gimgunlock.exe" on the IMG file (you won't find it here, against our forum rules to supply it).

Of course such old maps from 08/09 are about as useful as a hip-pocket in your underpants now. GPSMAP 276c can use latest Garmin NT mapping (not NTU smoothly though). It's not limited to the Old Format (non-NT) maps. Or use the open source OSM as you said, no need to unlock them and they'll work fine.

Thanks for your fast answer Neil.I know well gimunlock, from fiddling with Garmin Etrex, but those have the memory that can be seen.
Here I don't see the img.
Regarding newer NT, yes even 2025.10 works fine, but they look super basic (guess 276c isn't rendering correctly), like a basemap but more complete.

You can transfer "maps" back to the PC with Mapsource along with Tracks, Waypoints and Routes.

Then you can unlock the map and transfer it back to the GPS unit.