How To Unlock Bootloader On LG G5 SE H840 European Variant

LG officially supports unlocking the bootloader on the LG G5 SE H840, the European variant, through its developer program. This guide walks through the whole process using fastboot and LG’s official unlock site.

Unlocking the bootloader voids the warranty, so if your phone is still under warranty, it is worth waiting until that runs out. You can always re-lock the bootloader later if you need to.

This only works on the LG G5 SE H840 European variant. Do not try it on any other model. Follow the steps carefully.

What is a bootloader?

The bootloader is the code that runs when you turn on the phone. It starts up the hardware and then loads the kernel to boot Android. Manufacturers ship phones with a locked bootloader, which stops you from flashing anything other than the stock software. Unlocking it lets you flash TWRP, root the phone, and install custom ROMs, but it voids the warranty, which is why manufacturers lock it in the first place.

Pre-requisites

1. Charge the phone to at least 70-80%.
2. Unlocking the bootloader voids the warranty.
3. It wipes all your data, so back up the phone first.
4. Follow every step carefully. We are not responsible for any damage to your phone.

What you need

• Install ADB and Fastboot on your PC (Windows or Mac).

How to unlock the bootloader on the LG G5 SE H840

1. Enable Developer Options: go to Settings > About phone and tap the Build Number seven or eight times until you see “Developer option enabled”.
2. In Settings > Developer Options, enable OEM Unlock.
3. Note down your IMEI by dialing *#06#.
4. Open a command prompt in the ADB and Fastboot folder (hold Shift and right-click in the folder, then choose the command window option).
5. Connect the phone to the PC with a USB cable, then boot into bootloader mode. Either power off and hold Power + Volume Up, or, with the phone on and connected, run:

   adb reboot bootloader

6. Confirm the phone is detected in fastboot:

   fastboot devices

   If your serial number shows up, you are good to go. If nothing is listed, your drivers or cable are not set up correctly, so fix that first.

7. Get the device ID (this step wipes the phone, so make sure you backed up):

   fastboot oem device-id

8. This returns a character string across two lines. Paste the two lines together into one continuous string, without “(bootloader)” or any spaces.
   

   Example output: (bootloader)—————————————————————– (bootloader) Device-ID (bootloader) CD58B679A38D6B613ED518F37A05E013 (bootloader) F93190BD558261DBBC5584E8EF8789B1 (bootloader)—————————————————————–

   In this example, the combined Device ID is:

   CD58B679A38D6B613ED518F37A05E013F93190BD558261DBBC5584E8EF8789B1

9. Open LG’s official bootloader unlock site: LG Developer bootloader unlock.
10. Click Start Unlocking the Bootloader and sign in (register first if you do not have an account).
11. Enter your IMEI and paste the Device ID string from step 8.
12. Click Confirm. If the IMEI and Device ID are valid, LG emails you the unlock key.
13. Open the email from LG and download the unlock.bin attachment, then move it into the ADB and Fastboot folder.
14. With the phone still in fastboot mode, flash the key:

    fastboot flash unlock unlock.bin

15. Reboot the phone:

    fastboot reboot

16. To confirm the unlock, boot back into fastboot and run:

    fastboot getvar unlocked

    A response of unlocked: yes means it worked.

That is it. The bootloader on your LG G5 SE H840 is now unlocked, and you can go on to flash TWRP, root, or install a custom ROM.

FAQ

Does unlocking the bootloader erase my data?

Yes, it wipes the phone completely, so back up everything you want to keep first.

Can I re-lock the bootloader later?

Yes. You can re-lock it at any time, which is useful if you want to return the phone to stock.

Will this work on other LG G5 models?

No. This method is only for the LG G5 SE H840 European variant. Other models use their own unlock methods.

If you run into any trouble, leave a comment below.