WARNING! : This is only for the GT i9300 (international version) , Check your device before proceeding. Also you might lose all your data. So backup! i am not responsible if you brick your phone(although very unlikely) by not following the guide properly
Also you will lose your custom recovery, Custom ROM and will not longer have root
Ok lets begin!
1. Make sure you have the samsung drivers installed on your pc (http://bit.ly/SDaIIE)
2. Your device should have at least 80% battery left
3. Enable USB Debugging by going to Settings>Developer Options>Tick the Usb debugging tick box!
Files needed :
1. Android 4.1.2 I9300XXEMC3 for Galaxy S3 I9300 - http://www.hotfile.com/dl/202240205/...1_NEE.zip.html
2. Odin 3.07 - http://bit.ly/16aRzF4
Extract The firmware Zip file until you get a file with a .tar extension and some other files. Do not extract furthur
Extract odin zip file till you get Odin3 v3.07.exe
Now here comes the actual flashing part
1. Power off your smartphone. Wait 5-6 seconds for vibration to confirm complete switch off.
2. Now, get into Download Mode by pressing and holding Volume Down, Home and Power button simultaneously until Samsung Galaxy logo appears in phone screen. Wait few seconds and your phone will be in download mode.
3.Open odin as administrator and connect your s3 to your computer with usb cable
4. You will get a message "Added" in the message box in odin and You should also see COM port with a number in Yellow if you successfully added your device.
if you don't get this , try another usb port.. if it still doesn't come , reinstall drivers.
5. Select these files from I9300XXEMC3 folder in Odin at respective buttons:
Click the PDA Button, and select the .tar.md5 file here with *code* appearing in its name
Click the Phone Button, and select file with *modem* in its name (leave if there is no such file)
Click the CSC Button, and select file with *csc* in its name (leave if there is no such file)
Click the PIT Button, and select the .pit file. Use only if you got it while extracting , otherwise ignore it.
6. make sure Auto Reboot and F. Reset Time checkboxes are selected. Also, make sure that Re-Partition checkbox is selected, only if you are using a .pit file
7. Double check everything above and hit start!
8. once flashing is complete the phone will reboot automatically and soon you will see a PASS message with green background in the left-most box at the very top of the Odin. You can then unplug the USB cable to disconnect your device from computer.
After completing these steps, Make sure to wipe the cache and do a factory reset in clockworkmod recovery if you do happen to find yourself in a bootloop (phone rebooting continuously) Or just do it anyways to prevent a bootloop from occurring.
congrats! , you have just restored your i9300!
If this has helped you make sure to hit the thanks button!