[G2 General] OfficialPerson:
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After installing a KK beta build rom I noticed my cell service was disabled so I checked the settings/status and everything showed up

as unknown including imei. Here's the full process I went through until finally fixing/restoring service on my phone.

NOTE: all of this was possible because I still had two very important files called

modemst1.img

and

modemst2.img

these are what hold the important info about the phone including imei and such. Luckily [MENTION=2684188]autoprime[/MENTION] has a script in ioroot that'll backup

these files if you're on JB but if you're on KK you have to MANUALLY back them up. With that being said if you don't have these files

then this guide isn't for you.

So the first thing I tried (after restoring my nandroid backup which I found out didnt backup those modemst files) was take the two modemst files from my ioroot folder on my computer and putting them on the internal storage of the phone in a folder called EFS_Backup. I renamed the two files to efs1.img and efs2.img (if you don't have the option to show the files extension in the name enabled then you would just type in efs1 and efs2 or else the filename would end up efs1.img.img etc.) After that I put the phone into recovery (twrp) and plugged the usb cable. Then I ran cmd as administrator and typed these commands:

adb shell

su

dd if=/sdcard/EFS_Backup/efs1.img of=/dev/block/platform/msm_sdcc.1/by-name/modemst1

dd if=/sdcard/EFS_Backup/efs2.img of=/dev/block/platform/msm_sdcc.1/by-name/modemst2

It said that it copied them however I checked the folder with root browser and it still showed the empty modemst files (my backup ones were 3mb). So I tried the commands while the phone was booted up I granted root access and it said it copied again but still nothing. Around this time I got into a bootloop and was getting stuck so I flashed a KK baseband which helped me at first. At this point [MENTION=5232783]dr87[/MENTION] gave me a flashable efs zip file to use which I'm going to attach to this post. To use it you have to drag your two modemst backups into it name then efs1 and efs2 then flash the zip in recovery.

Like the other steps though that didnt seem to replace the modemst files and I was stuck without service. I then got a bootloop again and tried flashing my nandroid backup with the KK baseband but this time it wouldn't work so I went back to the KK beta build so I could boot up again. I tried running the dd commands again this time with the efs files on the root directory on the internal storage of the phone. The command I used for that was this:

dd if=/sdcard/efs1.img of=/dev/block/platform/msm_sdcc.1/by-name/modemst1

I got the same results as before. However another member said something about running the dd commands in stock recovery so I decided to do a zvc tot and try running the dd commands in the stock recovery. I downloaded the zvc tot from here: http://downloads.codefi.re/autoprime/LG/LG_G2/LS980/Stock_Firmware

I extracted the tot from the zip file and put it on my desktop and then I followed the sprint version of this guide:

http://xdaforums.com/showthread.php?t=2432476

Scroll down to the part where it says RETURN TO STOCK TOT Method! AT&T & Sprint Verzion & The Few International TOTs I have available

Follow those instructions there however after step number 10 where you set your G2's port to COM 41 turn off and unplug your phone then after 13 where you click the yellow arrow in LG Flash Tool put your G2 back into download mode and the Flash Tool will then connect to your device and start the process. Once that was finished I went through the setup and was about to reboot to get to stock recovery when I noticed something.......MY CELL SERVICE WAS BACK!!!! Apparently with the custom roms replacing the modemst files didn't stick but after moving to stock zvc it seemed to replace it and I'm now back up and running. If you have any questions let me know and I'll get back to you as soon as I can. Wish you all the best.

P.S. I would like to give a very big thanks to [MENTION=5543157]GizmoKaca[/MENTION] he really helped me alot through this whole process.