[Galaxy S III Q&A, Help & Troubleshooting] TrinityTrip54:
Ok. So here's the deal:

My SGS3 I9300 exynos phone did the famous IMEI 0049 and SN null trick.

I cannot say what precipitated it but is simply stopped registering on the network, so no calling or data. All other functions operational.

After much searching and reading, I settled on flashing the stock 4.3 back. This succeeded only in doing absolutely nothing to alleviate this issue. I wiped the entire phone. Maybe I missed a critical section wipe, but since the stock ROM overwrites all? the CSC/BL/MODEM functions I thought it would set the default for EFS (which I believe is where these critical data live). I'm not a programmer so I cannot say diddly about the architecture and interrelationship of OS files, but I am technical and I know how SW and HW does what it does.

This phone is my own and I have all the rights to it.

I had loaded RRemix ROM a loong while ago and it was functioning fine. Probably a corruption of the EFS due to battery contact being loose. This is in my mind the most likely cause as the system may be accessing the EFS files, say making a call, or accessing data, and the power drops out and voila! Corruption. But again this is theoretical.

Needless to say I tried the usual hocus-pocus out there with no avail.

Getting to understand the system better it seems obvious that these critical identification numbers are hard-coded into the chips on the phone. Which explains the ability to 'fix' them with JTAG and other cable/box solutions and SW. However, I cannot see how the SW loses the ability to read the IMEI/SN that is hard-coded (fused?) into the main-board.

All my research pointed to the EFS files having something to do with this.

Way back when I loaded the custom ROM I did not come across the 'backup your EFS' as a necessary step, so I had nothing to go back on.

And loading the stock 4.3 ROM back on and not having that fix the issue, led me to believe something else was up.

Somewhere in the guts of this phone something is screwing up the layer between reading the registers where the numbers sit and the software layer that reports the numbers.

So, much searching led to the nv_data.bin file being a key component in all this fiasco.

Now, before I say any more, I believe that describing the next steps could be a big no-no here.

Now, understand, all I want to do is get MY personal device working again. I have the SN and IMEI numbers on the physical device.

Sure, I could have stolen it and am attempting to change these to avoid prosecution. Anyone can say anything online.

Therefore, before I can proceed, I need advice from moderators and VPP to either say 'Yes you may post this info' or 'No. Go away'.

Am I allowed to do the following:

1) Describe how I restored my IMEI (Not changed, overwritten, or subverted to my limited knowledge)

2) In the case of 1 not allowed, post the link to where I found the info to achieve this.

3) Submit the 'fix' to a moderator or developer to check whether this is indeed and restoration or a change.

If it's a restoration of existing functionality, I cannot see how this could be a problem. If its changing something, then it's a whole other sack of ferrets.

My reasons for posting are that xdadevelopers has given me years of joy with my SG devices. (Yes, I have the whole range exclusively) Many ROMS, customs, fixes, hints and saves deserves something back, and the difficulty in achieving this particular fix, warrants it.

But I don't want to break any rules, this being my first post.

So, please let me know what I can do to help others stuck in this position...

You can find it if you have the correct search parameters. Perhaps I can say that instead?

Thanks.

And thanks to all who have helped over the years.

T

[Edit] Just to clarify, the solution requires no special HW or 'boxes'. You do need root, however, and a hex editor. I had a reply explaining the use of Octoplus, which requires credits and registration. You will need none of those.