The Galaxy S3 GT-I9305 recently received a handful of official Jelly Bean firmware from Samsung. However, the LTE handset had not tasted any good custom ROM Jelly Bean updates until now. With due credit to the CyanogenMod team, the I9305 can now be updated to Android 4.2.2 Jelly Bean via the popular CyanogenMod 10.1 (CM10.1) ROM using this guide.

CM10.1 ROM brings the best custom features on the latest Android firmware for a bloatware free, and fast user experience. The built-in theme engine reportedly offers a striking, unique look to the phone's user interface (UI).

The latest Android 4.2.2 firmware harbours a host of intriguing features such as multi-user support, gesture typing, new quick settings option, lock-screen widget, new camera app, photo sphere, improved Google Now, new daydream feature and miracast display.

Some of the new, key features ported into the CM10.1 ROM are listed below:

  • Lockscreen Gestures
  • Phone Goggles
  • OpenVPN support
  • Incognito mode
  • Theme manager
  • DSP Equaliser
  • Custom led control
  • Lockscreen shortcuts
  • LockClock widget app
  • Full customised MMS app and more

Key Points to Note

  • CyanogenMod 10.1 ROM and the instructions given in this guide are meant for the international LTE variant Galaxy S3 GT-I9305 model only and will not work on any other device. Verify the device's model number by navigating to Settings > About Phone.
  • Verify that thecorrect USB drivers are installed for the phone on computer (download Samsung Galaxy S3 GT-I9305 USB drivers).
  • Back up important data and settings on phone using one of the recommended custom recovery tools such as ClockworkMod (CWM) or TWRP, as it creates a complete image of the existing phone setup.
  • Ensure that USB Debugging mode is enabled on the phone navigating to Settings > Developer Options (if the device is running on Android 4.0 or later) or Settings > Applications> Development (if the phone is running on Android 2.3 or earlier). Otherwise, if the device is running Android 4.2, then perform the following steps:
    • Go to Settings > About Phone
    • Scroll down to the bottom of the screen and select Build Number
    • Tap the phone's Build Number seven times to unlock or reveal the hidden Developer Options under Settings. Then select the checkbox to enable USB Debugging mode under Settings > Developer Options.
  • Make sure that the phone has at least 80 per cent battery charge to prevent unexpected device shutdown (due to battery drain) during firmware installation, as this may inadvertently brick or damage the device.
  • Double check to see that the device is factory unlocked (not locked to a specific carrier) and rooted with CWM recovery installed on it.
  • If the device is stuck at boot or facing boot loop issues, then perform Wipe Cache Partition and Wipe Dalvik Cache four to five more times before rebooting.
  • Allow the newly installed ROM to stabilise for five to ten minutes after first boot, before working on it.
  • If a Status 7 error appears on screen, then either the device being flashed is incompatible or an associated kernel needs to be installed prior to installing the ROM.
  • The phone will not be recognised by Samsung KIES after installing the ROM, as it is a custom release.

How to Install Android 4.2.2 Jelly Bean Update on Galaxy S3 GT-I9305 via CyanogenMod 10.1 ROM

Step 1: Download CM10.1 ROM for Galaxy S3 I9305 and Google Apps

Step 2: Connect and mount the phone's storage on computer using the USB cable.

Step 3: Without extracting, copy the downloaded ROM and Google Apps zip files to the root folder on the phone's SD card.

Step 4: After the file transfer process is complete, disconnect the phone's USB cable from computer and then turn off the phone.

Step 5: Boot the phone into Recovery Mode by pressing and holding Volume Up, Home and Power buttons together until the screen flashes, and then release all three buttons. Note: Use volume buttons to navigate between options and Power button to select an option in Recovery].

Step 6: Take a Nandroid backup of the existing ROM, so that it can be restored later if the new ROM fails to work or if you want to return to the original ROM. To do a Nandroid backup, choose Backup and Restore and then click Backup on next screen. Return to main recovery menu once backup is done.

Step 7: Perform a full data wipe to prevent conflicts between the new ROM and previous ROM. To do so, click wipe data/factory reset, then choose Yes on next screen to confirm. Wait for a few minutes until the data wiping process completes.

Step 8: Return to CWM recovery main menu. Hit wipe cache partition and once the process completes, choose Wipe Dalvik Cache under advance option. Wait until the data wipe process completes and then proceed to the next step.

Step 9: Choose Install Zip from SD card and then click Choose Zip from SD card. Now, browse and select the CM10.1 ROM zip file copied earlier to the phone in Step 3, and select it by tapping Power button. Confirm the ROM installation on next screen and soon the installation process will begin.

Step 10: Once the ROM installation is complete, repeat the step 9 but choose GApps zip file instead of ROM zip to install the Google apps package.

Step 11: After both the ROM and Google Apps are installed, return to the main recovery menu and hit Reboot System Now. The phone will now reboot automatically into the newly installed ROM. However, the first boot may take some time (usually about 5 minutes). So, leave it alone.

Restoring the Previous ROM: To return to the original ROM, boot into recovery, choose Backup and Restore and then restore your previous ROM by choosing it from the list.

Android 4.2.2 Jelly Bean based CM10.1 custom ROM update is now installed and running on the Galaxy S3 I9305. Go to Settings > About Phone to verify the firmware version installed.

[Source: Droid Noobs]