Update AT&T LG G3 with CM 12 Nightlies Custom ROM

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Android stock Lollipop OS is great, though if we are talking about a carrier branded device, like the AT&T LG G3, things aren’t that perfect. Why? Well because stock firmware comes pre installed with various in built apps: bloatware. The bloatware are slowing down your phone, not to mention that most of the apps aren’t useful at all. Therefore, would you agree to change the stock Android 5.0 OS with a custom and pure Lollipop system that can be anytime customized and optimized?

If you are, then I have something really good for you: CM 12 Nightlies. Yes, that’s right, CyanogenMod officially released its CM 12 Nightlies built for your AT&T LG G3, which means that you can now safely and easily update your phone with this new CM ROM. Of course, Android 5.0 Lollipop is still there as CM12 is powered by the latest Android OS.

So, your AT&T LG G3 is now ready for one of the best custom ROMs out there; as we all know CM 12, AOKP and ParanoidAndroid are the most popular and the most important Android featured updates available on the Android market.

Since we are dealing with the Nightlies built of CM 12, you should know that the Lollipop firmware is stable enough for a daily use. In fact, there are no bugs or other software related issues included on this update, thus CM12 will smoothly run on your AT&T LG G3. Anyway, do note that this tutorial is only compatible with the AT&T model of LG G3 – don’t use the guidelines from below for similar devices as you can end up in bricking your phones; you can use our how to section for learning how to install CM 12 Nightlies on International LG G3, T-Mobile G3 or on the Canadian version of LG G3.

Good; now, as you might already know, root access must be ensured on your smartphone if you want to complete this tutorial. Therefore, go and root your AT&T LG G3 and then return here and resume the next lines. Moreover, after ensuring the root access you must install a custom recovery image on your phone – I recommend you to use CWM or TWRP recovery. You will have to use the custom recovery image because the CM update comes as a .zip file.

All these are unofficial operations – including the present update process. Thus, unfortunately, by completing all these procedures, you will lose your LG warranty – you will no longer be able to reclaim the warranty of your AT&T G3, so you might have to learn how to manually fix a bricked Android based device, as who knows when you will have to apply some troubleshoot solutions.

Good; now, before heading towards the flashing process from below, backup your AT&T LG G3. As you will notice, installing Android 5.0 Lollipop via CM 12 Nightlies will imply in making a wipe – thus, all of your data will be now erased. Therefore, don’t hesitate and temporarily save everything that’s personal and everything that you might use afterwards. Moreover, use the custom recovery image you have just installed and make a Nandroid backup for saving the current ROM that runs on your device too.

In the end, check this tutorial and learn how to prepare things up for the update process that will shortly follow.

How to Install CM12 Nightlies on AT&T LG G3 and Update to Android 5.0 Lollipop

  1. The first thing to do is to download the update package from here – you will find the CyanogenMod firmware for the AT&T LG G3 listed there.
  2. Place the file on your computer but don’t unzip it.
  3. Then, connect your device with your computer and place the update file on your phone’s SD card.
  4. Disconnect the devices and then boot recovery mode on your LG G3.
  5. From recovery select “wipe data factory reset”. Then, choose “wipe cache partition”. Finally choose “advance” and pick “wipe dalvik cache”.
  6. Up next, from main menu of recovery select “install zip from SD card” and “choose zip from SD card”.
  7. Select the CM 12 Nightlies file and install Android 5.0 Lollipop on your AT&T LG G3.
  8. That’s it; when done, return to main menu of recovery and select “reboot system now”.
  9. Enjoy and let us know how things worked for you.
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Andy Stevenson

Andy is a senior editor here on Android Flagship and you can surely rely on its experience as the Android subject is more than a hobby to him. Andy is currently focusing on developing dedicated and detailed tutorials, tips and tricks, so you will be able to find its work through the “how to” section of our website. Also, don’t hesitate and contact Andy if you have questions or if you want to hear a second opinion about anything that’s related to the Android OS.