G:\.System\
This Folder: Size: 1.1 GB

G:\.System\
JCV
D4385180A.jcv

SID
D3409230A.sid
D3410230A.sid

SQLite
D3408230A.db

gmap3d.img
gmapdem.img
gmapprom.img

Tools required:
Garmin Nuvi LMT with ASR for CTP2012/2012.5 (3490/3590LMT/3597LMT guaranteed to work - 3580LMT reported to work)
Garmin Nuvi 3490LMT/3590LMT/3597LMT for CTP2012/2012.5/CTP13 (3580LMT reported to work)
gimgunlock
JetMouse
Garmin Express
8GB+ USB Stick (the systems are very picky about the USB drives... if one does not work try a different one... slower drives works best)
Reported working drives:
SanDisk Cruzer 8GB (CTP2012)
Lexar S50 8GB (CTP2012)
Kingston Digital 16GB DataTraveler 101 G2 (CTP13)


CTP2012 / 2012.5


1-Copy the Garmindevice.xml from the nuvi onto your USB stick to the folder Garmin/
2-Run Garmin Express
3-Download CN NT 2015.20 NA update
4-Garmin Express will download the files to the USB stick in folder .system/, keep only the following files/folders:
.system/ASR (folder+contents): *******0.SRX to *******3.ASR (only the first 4 sequential files)
.system/gmapprom.img
.system/GMAPTZ.IMG
5-Rename .system/ to Garmin/
6-Create Garmin/JCV (folder)
7-Download: 2015.20 Full Size JCV [Please Register or Login to download file] and put it in JCV folder (this download is not required if your Nuvi version downloads the Full Screen JCV by default)
8-Put car in run mode (with engine on or not)
9-Turn all unnecessary features off (i.e. A/C)
10-Leave your radio on (needed to recognize a USB is plugged in)
11-Goto the Navigation screen
12-Plug USB stick into vehicle, it will start Validating the USB stick
13-When the update prompts, follow the menus, when it askes for an unlock code, use JetMouse (usage not explained here)
14-Let the system update (1-1.5hr process, if engine is not on, the car will shutdown half way through the process, you will need to put it back in run mode immediately, so ensure you stay with the car if you do not have the engine on)
15-Once it reaches 100%/full completion bar: It will either give a maps updated successfully message or reflash failed message. Just verify that the maps loaded fine, but you should be GTG.



CTP13

1-Copy the Garmindevice.xml from the nuvi onto your USB stick to the folder Garmin/
2-Run Garmin Express
3-Download CN NT 2015.20 NA update
4-Garmin Express will download the files to the USB stick in folder .system/, keep only the following files/folders:
.system/ASR (folder+contents): *******0.SRX to *******3.ASR (only the first 4 sequential files)
.system/SID (folder+contents): *********.sid (1st, 4th file only)
.system/SQLite (folder+contents)
.system/GMAP3D.IMG
.system/gmapprom.img
.system/GMAPTZ.IMG
5-Rename .system/ to Garmin/
6-Run gimgunlock on GMAP3D.IMG and GMAPPROM.img (usage not explained here)
7-Create text files GMAP3D.unl and GMAPPROM.unl and paste unlock code from JetMouse (usage not explained here, most state to exclude this step, but it had no negative effect on my system leaving it in the Garmin/ folder)
8-Put car in run mode (with engine on or not)
9-Turn all unnecessary features off (i.e. A/C)
10-Leave your radio on (needed to recognize a USB is plugged in)
11-Goto the Navigation screen
12-Plug USB stick into vehicle, it will start Validating the USB stick
13-When the update prompts, follow the menus
14-Let the system update (1-1.5hr process, if engine is not on, the car will shutdown half way through the process, you will need to put it back in run mode immediately, so ensure you stay with the car if you do not have the engine on)
15-Once it reaches 100%/full completion bar: It should more than likely give a reflash failed message vice maps updated successfully message. Just verify that the maps loaded fine, but you should be GTG.