For those who have a rooted Samsung Galaxy S3 (SGH-I747) from AT&T and basically having issues updating to the official Android 4.3 Jelly Bean that has been rolled out and comes with firmware build number I747UCUEMJB via OTA and or Kies, then this method is just created for you. Below is the original stock OTA update MJB that can be flashed through stock recovery and by installing thhis stock firmware this will restore your Galaxy S3 I747 to official AT&T firmware and will also upgrade to 4.3.
Warning: This will update your bootloader, so proceed at your own risk!!!
The update will also wipe all your data!
If your Galaxy S3 is currently runs on 4.1.2 I747UCDMG2 (no root or rooted)
1) Download the Stock OTA Update 4.3 I747UCUEMJB from here:
I747UCUEMJB Download – http://www.androidfilehost.com/?fid=23212708291680243
2) Copy it to your external SD card.
3) Reboot recovery, then navigate down and choose “install update from SD card”.
Press and hold Volume Up, Home and Power button. Use volume keys to select and Power or Home key to select the option. Then just wait until it completely finishes flashing.
If your Galaxy S3 currently runs with custom ROM and or with custom recovery.
(Use at your own risk I don’t know what ROM builds you have)
1) Restore or Odin back your Galaxy S3 to factory stock 4.1.1 I747UCDLK3. You may find the stock firmware there and also shows you the odin flashing guide.
2) Manually Install the stock OTA update 4.1.2 I747UCDMG2 via stock recovery (follow the guide above)
3) Then lastly install the 4.3 I747UCUEMJB same method above.
How to Root the MJB 4.3 update?
Root is still possible using CF-Auto Root, but be aware that the Android 4.3 update is now equipped with KNOX security suite. You can find this security application enforcing in the download mode (Press Volume Down+Home+Power keys) you will then see binary indicator that says “Warranty Bit: 0″. Once you install root this will compromised and tripped that counter and screwed your device service warranty. But if you don’t mind that much about warranty then its up to you.
Can I downgrade back to 4.1.2 to get rid of this KNOX?
KNOX is very useful on some cases for this apps protects users secured data and among other important stuff. But Nup!, Once you have upgraded to 4.3 Jelly Bean, there is no way returning back to 4.1.1 or 4.1.2. Doing so will just brick your device due to the new protected bootloader in Android 4.3. There are some devs at XDA-developers has been cooking a KNOX-free version on some devices like the Galaxy S4, so stay tuned if they can also do something similar for Galaxy S3.
UPDATE: Stock firmware I747UCUEMJB Odin flashable now available.
For those who prepare the Odin method, you can now grab the stock firmware from below source.
USB Driver – Samsung Android USB Driver
Use PC with Windows OS (Odin will not work on Mac and Linux)
Recharge your battery using external battery charger since you can’t charge the battery in the phone.
1. Run Odin on your PC desktop
2. Boot the Galaxy S3 into download mode screen for Odin.
Turn it off, once completely shut down hold down the ‘HOME’ + ‘VOLUME DOWN’ buttons and press the ‘POWER’ button for about 2 seconds until a WARNING! Screen appears. Press the ‘VOLUME UP’ button to continue or enter Download Mode.
3. Connect the phone to PC via USB. Then make sure you can see as phone “Added” in Odin log box or highlight the COM:ID once the device is detected,
4. In Odin window, DO Not tick ‘RE-Partition’ only Tick ‘Auto Reboot’ and ‘F. Reset Time’ and nothing else.
5. Now load the boot image and Odin on the PDA button.
6. Click on “Start” to flash the image.
7. The phone will then reboot to normal mode.
Credits to [upndwn4par] XDA highly recognized developer.