The official XenonHD build based on the Android 5.1.1 Lollipop AOSP is now live for all the LG G3 AT&T users. Check the instructions listed in this post in order to learn how to successfully install the new custom ROM for your device.

The XenonHD Android 5.1 offers a much better and smoother Lollipop experience then the stock LG software you can find on all the LG G3 devices. This ROM is based on AOSP Android 5.1.1 and it features all the stock Lollipop functions with no extra bloatware.

Note that the only think that is not so great in this ROM is the camera. LG has the camera software source code locked and developers haven't been able to port it for custom ROMs yet. Check the XDA thread here for more info on this release.

Before starting the installation process you should read the preparation info below:

  • use this post only if you own an AT&T LG G3 device.
    - the model number of your phone has to be D850.
    - check the version of your device under Settings> About Phone menu.
  • do not try to update any other devices with the files that you will find in this post.
  • your device needs to be on a rooted firmware and a custom Recovery has to be installed on it.
    - both Philz Touch (CWM-based) and TWRP Recovery versions are working with this post.
    - the installed custom Recovery needs to be running its latest version, so that it will support the installation of a brand new Android 5.1.1-based custom ROM.
  • in the tutorial you will find two extra preparation steps such as NANDROID ROM Backup and Factory Reset.
    - do not skip these steps.
    - the NANDROID Backup creates a full restore point for your device, one that you can use in case the new XenonHD Lollipop 5.1.1 ROM doesn't boot successfully after installation.
    - the 'factory reset' process has to be applied in order to remove the old ROM from your device and make room for a brand new custom ROM.
    - factory resetting the device means that you will wipe the system memory partition.
    - the internal and external storage partitions are not going to be affected by the 'factory reset' process.
    - note that all installed applications will be gone from your device after the custom ROM flashing process is done.
  • if you want to save data from installed applications, then you can use the Helium tool.
    - Contacts info can be synced with your default Gmail account.
  • this is a guide for advanced users, we cannot be blamed in case you brick your device nor in case you lose any data in the process.
  • read the whole guide and do not skip any steps.
  • we cannot be blamed in case you lose any data nor in case you brick the phone.

Now that you know all that you can continue to the next part of this post and learn how to flash a brand new custom ROM.

How to install XenonHD Android 5.1.1 AOSP ROM for AT&T LG G3 D850:

  1. Download the d850 XenonHD ROM file from here.
  2. Download Gapps for this ROM from here.
  3. Move both zip files to your phone's internal storage.
    - after the transfer is done you can disconnect the file from PC.
    - do not unzip the archived contents.
  4. Power off the device.
  5. Boot it in Custom Recovery Mode.
  6. Set the NANDROID Backup for the installed ROM:
    - Philz CWM: open the 'backup and restore' menu.
    - for TWRP use the 'backup' options.
    - set a name and storage location for the backup and confirm process.
  7. Factory Reset the device before installing the ROM:
    - Philz CWM: select 'wipe data/ factory reset'.
    - for TWRP use 'Wipe' menu.
    - confirm factory reset and continue to the next step when done.
  8. Now you can initiate the XenonHD Android 5.1.1 installation:
    - Philz CWM: select 'install zip from sdcard'.
    - for TWRP open 'Install' options.
  9. Locate the XenonHD zip file and confirm its installation.
    - do not press any buttons until all files are installed.
  10. After the ROM is flashed you can install the Gapps zip in the same way.
  11. Reboot your AT&T LG G3 in normal mode after all the new files are successfully installed on your device.
    - the first boot process of this new ROM is going to take a while before it loads all the new files.
    - don't press any buttons until the XenonHD welcome screen loads.
  12. Use your default Google account in order to regain complete control over your device once again.

These were all the steps that you had to take in order to install the latest XenonHD Android 5.1.1 ROM on your device.

In case the first boot of this new  ROM takes more than 30 minutes to complete or the device enters in a boot loop, then you will be forced to try and repeat the whole guide more than once.

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