The tutorial will walk you through the steps on how to properly root and install TWRP custom recovery on your Canadian Telus/Koodo LG G3 D852 (Also works for Bell/Rogers variants).
The common way to install TWRP on G3 is first to root the device and then use Autorec to install TWRP. This method is quick and dirty, but it can lead to problematic kernels which can break many functions (such as camera/phone not shutting down without battery pull) on your phone. This is why I strongly advise against using Autorec especially if you have the Telus/Koodo version of G3.
I will first explain the process behind rooting/bumping your phone, and why Autorec can cause potential problems. I will then walk you through the process of doing it properly.
I will not be responsible if you brick your phone. Use this tutorial at your own risk. Read the entire tutorial before proceeding.
There are many partitions on your android phone. For the purpose of this tutorial you need to learn the following partitions:
- aboot: bootloader (the thing that basically loads everything)
- laf: storing the program and files for download mode
- boot: loading the system, ramdisk, and kernel
- recovery: storing the recovery program
- system: storing the android OS (AKA ROM)
Our G3 bootloader is locked, this prevents us from installing unofficial images onto other partitions (phone stuck on boot logo). It does so by checking whether partitions are “signed” or not.
To circumvent this, developers have found a way to bypass the bootloader security check. This method is commonly refrerred to as “Bump” for our G3.
So how does bump work? It fake signs our custom/modified partition to trick the bootloader thinking that our modified partition is legit and allow it to load. These fake signed partitions/images/zips are referred to as bumped.
Logically, we don’t want to flash anything not bumped onto our G3. Most custom ROMs and recoveries are already bumped. However, before you do anything you need to get your boot partition bumped! Else your bumped ROM/Recoveries will not load. In order to bump our boot partition, we need to first gain root access.
We will use one application: “ImageprepGUI” to achieve all these steps.
- Return to stock Lollipop (this method only works with Lollipop or Kitkat). If you are on Marshmallow you can revert to Lollipop by following this tutorial on XDA.
- Extract and Install LG Mobile drivers: Download
- Extract Install ImageprepGUI: Download (Created by XDA:topet2k12001)
- Extract KitKat aboot and laf images (D852): Download
If you are flashing a non D852 G3, you need to download your own version of aboot and laf here
- Download Bumped TWRP recovery: Download
- Revert everything back to stock lollipop if you flashed a custom recovery or used Autorec(Autorec has the revert back to stock function).
- Enable USB Debugging on your phone
- Open device manager and make sure there is only LGE Mobile in COM port. Temporarily disable any other devices that is present.
Summary of Steps
The Imageprep program does the following thing for you:
First Step: Rooting the device
You can stop here if you just want root. However, you won’t be able to flash any custom images/zips (It will soft brick your phone).
Second Step: Make your phone vulnerable to Bump
Before bumping our boot partition, we need to make the phone vulnerable to the bump exploit. This is done by flashing KitKat versions of aboot and laf images. This needs to be done or else your bumped boot partition will not load. Don’t worry, KitKat aboot/laf will not interfere with your lollipop/marshmallow ROM. As long as you have the correct boot partition your ROM will run flawlessly.
Third Step: Bump our boot partition
In order to flash anything that’s bumped, we need to further prepare our phone by bumping the boot partition. This is where Autorec messed up. Autorec flashes a bumped boot image that contains a wrong kernel for our Telus/Koodo G3 (It uses the Rogers/Bell version kernel which is slightly different from ours)
ImageprepGUI does it correctly by first extracting the stock boot partition from our phone, bump it and flashes it back.
Fourth Step: Installing Bumped TWRP custom recovery
How to Use ImageprepGUI
- After installation, go to C:/ImageprepGUI. Run imageprepGUIv2.6.exe as administrator. Make sure you have all the necessary files as stated in the preparation section.
- Click through the introduction pages until you reach “Selection Option”
- Select “I have my own copies of KITKAT Image Files” and “I have my own copy of bump’d TWRP Custom Recovery”.
- In the next page select the second option if you only want to root. Select the fifth option if you want to root, bump your device, and install TWRP. Option 1 and 4 is only for KitKat stock ROMs. If you are already rooted, you can use option 3 to bump and install TWRP.
- The program will ask you to locate the aboot.img laf.img files and the TWRP image file you downloaded.
- After that just follow the program’s instructions. You will have to grant ADB connections and superuser permissions on your phones so make sure to keep an eye on both the phone and the computer as the program runs.
- Enjoy your bumped LG G3 D852 with correct stock kernel!
Once you finished running the program, ImageprepGUI stores copies of the un-bumped and bumped images on your SD-Card in a folder named ImageprepGUI. Save those img files as they can become useful later on.
If you want to use other Lollipop ROMs, it is recommended that after flashing the ROM you flash your own bumped boot.img again. Since most ROMs include kernel for the Roger/Bell version of D852.
Currently our Telus/Koodo version of G3 D852 doesn’t work well with other Marshmallow ROMS because Telus has not released MM yet so we don’t have a proper kernel. When Marshmallow comes at the end of the month we can do the same thing, then use our proper kernel with other MM ROMS like Fulmics.
Visit HERE to download the latest official Telus/Koodo Marshmallow ROM for D852.
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This tutorial is based on my research in the XDA forum. None of this would be possible without the developers who made the tools available.