[LG Optimus L9 P760, P765, P768, P769] leereyzhe:
This tutorial is for us P769/MS769 owners with phones manufactured after mid 2013, who have trouble unlocking our bootloaders using this method, because the bootloader seems to be encrypted.

The solution is to flash using a special LG Flash Cable with a 910k resistor. In this tutorial I will show you how I did it and how you can do it too.

You will need:

A reasonably modern PC running Windows 7. XP or Vista most likely will work also, but I've heard Windows 8 has problems.

Your LG P769/MS769

SIM card with a valid cellular connection (you need a cellular data plan for this to work).

A micro SD card, at least 1GB free space recommended.

A standard Micro USB cable

A 910k resistor cable

LG United Mobile Drivers. You can download these from the official LG website, but I also included it in the files.

Toolkit of all the stuff you need

7zip or other to extract the toolkit

ROM you want to install (gapps also, if you want)

Optional: KDZ of V20H. Only needed if you want to flash back to stock before flashing your ROM. I didn't include this in the toolkit to save space.

---Obtaining 910k Cable---

You can buy this from various sites on the internet

GSM Support and Alibaba have them. There are some on Ebay as well. If you want others just Google it. ;)

Or, if you are comfortable with soldering you can make your own.

You will need a 910k resistor, a micro usb male head, and a spare usb cable.

Here are some helpful diagrams:

Note: If it doesn't work, then try reversing the order of the wires. For some reason, the heads i bought had the pins in reverse order.

You can also test which wire corresponds to which with a multimeter, wrap a resistor around one lead and touch a pin in the microusb head, the other lead the corresponding pin on the regular usb head.

---Preparation---

First, backup all your data of course.

Download the toolkit, and extract it.

Install the LG United Mobile Drivers.

Navigate to the folder SD Card. Copy the files to your micro SD card. I recommend in the root directory, it could save you a lot of time and frustration later.

Also copy your ROM (and gapps) to the SD card.

Navigate to the folder Flash V10G. Copy RootFlash and shttps to the root directory of your hard drive (C:\). It must be in the root, or else it simply won't work.

Turn on USB debugging.

---Flashing V10G---

Use the normal Micro USB cable to connect your phone to PC.

Put the phone to Software Mode. Autorun should pop up, go ahead and run it. A popup will appear, just close it.

Follow this tutorial (thanks cmahendra) to flash V10G_00.kdz. (Note: No need to download the tools again from that tutorial, you already have them ;))

After the flash is complete, you can unplug the micro usb cable.

Phone should reboot, and get stuck at the bootscreen.

Just pull the battery for a few seconds, and replace.

Hold Volume Up, Home, and Power buttons simultaneously. This will factory reset your phone.

When the phone powers on, release Power but hold on to Volume Up and Home until the Android appears.

Your phone should reboot into the setup. Just go through it real quick, and let the apps install.

Now go to Settings:

Go to Apps and disable: Lookout Security

Go to Security and check: Install from Unknown Sources

Go to Developer Options and check: USB Debugging, Show Touches

Power off your phone.

---Flashing V20B---

Navigate to folder Flash V20B > LGFlashTool. Run LGFlashTool.exe.

A prompt will appear.

For DLL: selectLGP760_20120911_LGFLASHv1350.dll

For S/W: select LGP760_AP.bin

It should look like this:

But don't click OK yet!

On your phone, hold Volume Up (or down?) and plug in 910k cable. S/W mode should appear.

Find: Device Manager > Ports (COM & LPT) > LGE Mobile USB Serial Port (COM#) > Properties. > Port Settings tab > Advanced.

Change COM Port Number to COM41. You can exit Device Manager now.

Now go back and click OK.

Click this:

And change it to look like this:

Press OK.

Click this:

A ready sign should pop up in the first box. Now just unplug the 910k cable, wait a few seconds, and replug.

Now it should flash, just wait for it to finish.

(thanks to sammyz for the original tutorial)

---Enabling Radio---

Your phone should reboot into a blue LG logo. You can unplug the 910k cable now.

When it loads, the screen and colors is inverted. A mirror may be helpful for reading the inverted font.

The touchscreen is also completely whack. Enabling Show Touches helps immensely here.

The top half is normal but shifted down slightly. The bottom half is completely upside down. This is very frustrating to navigate. Just have patience, and think of the joys of an unlocked bootloader. :laugh:

Note: If for some reason the phone factory reset, then you have to enable USB Debugging, Unknown Sources, and Show Touches again. Otherwise continue on.

Insert the SD card.

Open up File Explorer and navigate to external_SD. install LGPwn, SuperSU, Busybox, LG Recovery Installer APKs you put there earlier.

Open LGPwn, and go through until the LG Backup options appears.

Click Restore > Internal Storage > Lgpwn.

When it finishes, press the button and it will reboot the phone.

Now open SuperSU, and install the binary in Normal mode.

Open Busybox Installer and just press the install button on the bottom.

Open LG Recovery Installer (thanks artas). It should say Status: Not Installed.

Click the install button, and install the stable version. After it completes, it will ask if you want to reboot to recovery. Reboot into recovery.

Note: You can press the button that reboots, or you can restart the phone and hold Volume Down when the key lights flash.

You should now be in a backwards CWM screen.

Go to install from zip > install zip from external sd

Select radio.zip. Wait for it to finish, then navigate to the main menu and restart the phone.

---Unlocking Bootloader---

Now you should have data enabled. Note: If you have T-Mobile 4G, it will probably show as H+ instead of 4G.

Open up the YouTube app, and play something long. This is to keep the connection active.

Wait 35-45 minutes. Most people get the unlock token at around 35 minutes, but I personally waited 45 minutes.

After that, plug in the normal USB cable.

On your PC, open up Command Prompt and navigate to Unlock BL. I have also made corresponding batch scripts for these commands as well, you can just run those.

Note: You can also open the folder in Explorer, hold shift, right click in the window, and there will be an option to open command prompt there.

Type this magic command: adb reboot oem-unlock

Your phone should reboot into a fastboot screen, with very small font.

Basically, just press Volume Up to unlock bootloader. Don't exit fastboot.

Type this to flash a newer ClockWorkMod: fastboot flash recovery CWM.img

Note: If you want to do the optional step below, you can exit without flashing CWM.

Power off your phone and remove the SD card.

---Optional: Reverting Back to Stock---

For whatever reason, you might want to flash back stock before flashing Cynogen, just to make sure you have latest firmware, radio, etc.

I can't prove that there's any difference, so it's up to you.

Just flash V10G, then flash V20H, both with the tool from the first flash.

The touchscreen will still be whack, but you're probably used to it by now. :D

Then once you get to V20H, install LGPwn, SuperSU, Busybox, and Flashify

Boot into recovery and install cwm_ts_fix_p769.zip.

Reboot and your touchscreen should be back to normal.

Now open Flashify, install recovery, and select recovery-6.0.4.9-p769.img

This will install the latest CWM, now you are ready to flash the ROM.

Note: if you enjoy stock ROM you can stop here. :D

---Installing Cynogen---

There are many different versions of Cynogenmod and other ROMs for our phone.

A whole list can be found here. I recommend KANG CM11, as it seems to be the most frequently updated.

but there are other CM11 by AntonX and BobZhorne.

Power on your phone, boot into CWM the same way by pressing Vol Down when the lights flash.

Flash the zips of your ROM and gapps if desired.

Have fun! :laugh:

I hoped my tutorial helped you guys.

Please, comment if you need help, have questions, or notice I forgot something!

Thanks to cmahendra, sammyz, kuma82, lelus, CygnusBlack, carloswii, and anyone else for their wonderful tutorials and tools!

Thanks to mven45, DarryDoo, anstoss, and anyone else for the valuable information about 910k cables!

Couldn't have done it without them.