2015 Mustang Nav unlock help

It can't be done on the sync 2 systems, not how your thinking. The old sync 2 or My Ford Touch uses a software based nav that is stored on an EEPROM in the A.P.I.M. You can get an apim with nav loaded onto it and install it in your car, but the first time a dealer plugs in to check for updates it will load the as built data and wipe out the nav software putting you back to square 1. Your best option is to upgrade to sync 3, the nav software is hard coded into the apim and can not be erased. And the sync 3 system is a lot better and more stable than the old sync 2 setup ever was.