[LG Optimus G (International)] Rockguy40:
If you can get in download mode, nothing is lost. You can still go back and restockify you LG Optimus G (stock rom ,locked bootloader ,no root).

Original Work by lucaarx@androidiani I have only translated it to English

Tested and working on LG-E975

Some tips before you start

As you will see is a fairly simple procedure, but not without risk. Take a quick read the entire guide before you begin: it will help you understand how to move.

The most important thing is to keep calm, do not panic and do not crush random keys. If you do not understand a passage, reread it. If you have not figured it out yet, reread it AGAIN or ASK here for help. No one runs behind you, so do not do things in a hurry.

I DO NOT TAKE ANY RESPONSIBILITY IF YOU BRICK YOUR PHONE.

Given that at end of the flash is recommended to do a hard reset, is a good idea to make a backup of all your personal data (photos, videos, etc etc), contacts , and if you want even applications.

DON'T FORGET TO BACK UP EFS PARTITION!

Prerequisites

1. Download the KDZ with this tool (credits kudos@xda) https://mega.co.nz/#!wxoHSayQ!AsUn6wfsc0rts87HIlOSwBd9dilot2229useWzrsH_g

2. Download and install the LG USB drivers LG USB Drivers

3. Download this file. It's a compressed file that contains everything you need NEW KDZ Updater

4. Download and install LG Mobile Support Tool http://csmg.lgmobile.com:9002/client/app/B2CAppSetup.exe

Let's start

1. Extract the "Flashtool" folder on the desktop, or where you want. Open the folder "Flashtool" and install msmxl.msi (if not already installed).

2. Turn off the phone and connect it to the PC with the USB cable while holding VOLUME- AND VOLUME +, until you see the download mode logo. The PC will install some drivers. There may be a kind of protection that prevents you enter this mode if there is too little current on the phone.

However, you must be able to get to the screen that's underneath.

4. Go back to Flashtool folder and run as administrator WindowsEnabler.exe. Go to the bar at the bottom right, and click once with the left mouse button over the icon of WindowsEnabler, so that appears the "On"message.

5. Now run as administrator UpTestEX.exe and do the following:

-Select the .KDZ file that you want to flash

-Set "3GQCT"

-Set PhoneMode "EMERGENCY"

Once done, click "Normal web upgrade test"

6. In the next window click "Upgrade Start"

7. Wait a few seconds an a new window will pop up.

- Click "Clear phone.."

- Select different country if you're not in Korea

- Select Language

- Click OK

After this the LG flashing tool should start analyzing your phone and flashing the .KDZ

Once done you can detatch the USB cable and see if the phone boots up. However it will probably bootloop. In this case follow the Hard Reset Procedure below.

Hard Reset Procedure

The phone has to be off. Hold Volume - AND Power , a message will show up confirming the factory reset. Press Power Button twice , than wait. It will auto reboot.

Thanks:

- lucaarx@androidiani For the realization of the guide

- Xerxin@xda For the big work regarding .KDZ files

- hyelton@xda Flashing 1 GB and greater .KDZ

Notes

- I have translated this guide because the one I found was little bit tricky unclear and didn't work for me, I hope I have done a good job. I'm anyway available to any modification. Just write below.

- Also I'm Italian so there may be some mistakes in the translation , report back i will correct them with pleasure.

Don't forget to report back if it worked!