T-Mobile LG G3 D851 can now be updated to latest Android 6.0.1 Marshmallow via Temasek V1.9 CyanogenMod’s CM13 custom ROM. This ROM is still in the initial stage of development so it might have some bugs which may not allow all the functions of the ROM to work correctly. If you have got AT&T LG G3, then update over here whereas here is the Verizon LG G3 Marshmallow update via Custom ROM.LG G3 Emoji

So, make sure if you are looking to flash this ROM on your T-Mobile LG G3 device then it must be only for the experience purpose. To know how the Android 6.0.1 Marshmallow works on your device. But if you are looking to flash the ROM for daily use then we advise you to wait till you get some better and stable custom ROM for your device.

Also it is necessary that you must have root access on your device and along with it you must also haveĀ  custom recovery installed on your device. So, if you have all the requisites then you can go ahead and flash the ROM and experience the new Android on your device.

Follow the preparation steps and the steps for installing the ROM carefully so that you may prevent your device from bricking.

Preparing your Device

  • This instructions are only for T-Mobile LG G3 D851 device, an attempt to try it on other device may brick the device completely.
  • Charge your device to 100%.
  • Back up all important data to external storage, so that you can restore it later.
  • Make a Nandroid Back up of present ROM to restore it in case the Custom ROM does not work properly.
  • Install USB drivers for LG G3 on your PC if not done already.
  • Install TWRP recovery on your device.
  • Device should be rooted and its bootloader must be unlocked.
  • Enable USB debugging mode on the device. Go to Settings> Developers options > USB debugging mode.USB Debugging

Install Android Marshmallow Custom ROM

  1. Download the Android 6.0.1 Marshmallow CM13 custom ROM from here.
  2. Download Open Google Apps for Android Marshmallow from here.
  3. Transfer the file to device internal or external storage memory.
  4. Now, turn off the device and reboot it into Recovery mode by pressing holding appropriate hardware buttons.
  5. In the recovery mode select Back up option and make a backup of all required data.
  6. Now, select Wipe and the check Data, Cache, Dalvik Cache.
  7. Swipe the button at the bottom of the screen to confirm the Wipe action.
  8. Now, return to main menu and select Install.twrp
  9. Navigate to the ROM file downloaded in step 1 and flash it (Swipe the button at bottom to flash the ROM file).
  10. Now tap on Reboot in main menu.

Device will now boot up in normal mode, updated to Android 6.0 Marshmallow. To check the version go to Settings > About Device.