AT & T LG G3 D850 just got a new custom ROM CyanogenMod's CM13 to update the device to latest Android 6.0.1 Marshmallow. Flashing this CM13 ROM will give you access to many advanced features which can not be found in the stock ROM.LG G3 Phone

So, the users who own a AT & T LG G3 D850 can download and flash the ROM on their device. As this is custom ROM it is necessary that you have root access on your device and also have custom recovery like TWRP or CWM installed on your device.

Users who are anxious of Updating their AT&T LG G3 D850 to Android Marshmallow, then here is an unofficial way of doing that.The CM13  is unofficial ROM having all the features of Android Marshmallow official update.This CM13 work well but it might have few bugs which may cause the ROM functions to not work properly up to the mark.

Let us now move ahead and have look at the procedure for how you can flash this custom ROM on your AT&T LG G3 device.

Preparing your Phone

  • This instructions are strictly for AT&T LG G3 D850 phone, so do not try it on any other device or you may brick your device.
  • Device should be fully charged up to 100%.
  • Install LG G3 D850 USB drivers on your computer.
  • Back up all the required data to some safe storage.
  • Make a Nandroid back up of the current ROM so that you can restore it when required.
  • Make sure the device bootloader is unlocked.
  • Root your device and install custom recovery on it if not done already.
  • Enable USB debugging mode of your device. Go to Settings > Developer options > USB debugging mode.USB Debugging

Install Android Marshmallow based CM13 Custom ROM

  1. Download the Android Marshmallow CM13 Custom ROM from here.
  2. Download the Google App's for Android Marshmallow from here.
  3. Transfer both files to your device storage by connecting the device to PC.
  4. Disconnect the device and turn it off completely.
  5. Reboot the device into recovery mode, press and hold Volume Down + Power key for few seconds.
  6. When in recovery mode tap on Wipe tab and select the options Cache, Dalvik Cache, Data, EFS Data
  7. Now, confirm the wipe action by swiping the button at the bottom of the screen.
  8. Now, return to main menu and tap on Install tab.
  9. Navigate to the ROM file stored on you device storage and select it.
  10. Swipe the button at the bottom to flash the ROM file on your device.
  11. In the same way flash the Google App's on your device (step 9-11).
  12. Return to main menu and tap on Reboot.
  13. System will now reboot in normal mode.

That's all you can now check the device Android version in Settings > About device > Android version.