[G4 Q&A, Help & Troubleshooting] gregor.eesmaa:
Hello!

I attempted to modify some system files (overwriting mine with LG v10 ones supplied in this thread: http://xdaforums.com/g4/themes-apps/help-bringing-lg-v10s-camera-to-g4-t3223371) and my device ended up not going past the first boot screen (where the "Bootloader unlocked!" message appears).

Some facts:

- I have the H815 variant

- I have tried the drivers that come with LG Bridge and some others found on this forum.

- I have (officially) unlocked my bootloader, voiding my warranty

- The device gets stuck on the first boot screen (the one with text "Bootloader unlocked!"), led starts pulsing blue a second later.

- Logcat from boot is located at: pasteb in.com/64RZ3SgJ

- I have TWRP, but the press combination ( vol-down + power-button key, release for 1 sec, press them again) to boot into it doesn't work.

- I had Android 6.0 installed using the zip flashing method from recovery - with root.

- It does get past the first boot screen when I connect the micro-usb cable and it figures it has enough juice to turn on itself, but doesn't get past the boot animation then.

- I can access Download mode

- I tried flashing H81520A_00.kdz with LG Flash Tool 2014 (both normal and CSE mode), but it says: "Required info cannot be found. Contact the system administrator". Device doesn't react.

- I tried flashing older Europe Open H81510D.kdz with LG Flash Tool 2014, but it says: "Upgrade stopped due to an error." and wants me to try again (which didn't help). This message comes after a few seconds of attempting an upgrade to which my phone actually reacts - some text changes in download mode log box.

- (I did use LG Flash Tool 2014 in CDMA - DIAG mode)

- I tried using LG Update Recovery tool in LG Bridge. A similar error appeared making me retry the process, which doesn't work as well.

- Running any fastboot command yields in message: "< waiting for device >"

Please provide me with assistance as I've found other people with similar errors as well (even though their devices aren't bricked yet) :)

Edit 1: I discovered I had a short time window of ADB access after booting. I used the command "adb reboot recovery" and got into recovery mode. Will try to reflash system files.

Edit 2: Problem solved. Android booted up normally after reflashing the files. Gosh this was nerve-racking. Somebody should make a tutorial out of this.

Edit 3:

I was asked to write a more clear procedure, so here's my attempt. It is better than nothing. Again I suggest someone try to write a better explanation and verify that it works on other devices as well.

1. Have adb installed on your computer

2. Have the necessary drivers installed on your computer. I think I used these: http://tool.xcdn.gdms.lge.com/dn/downloader.dev?fileKey=UW00120120425

3. Have your phone turned completely off.

4. Test if adb works from the console, using the following command: "adb version"; if it doesn't google for how to add adb to system environment path.

5. Connect the computer and the device using a micro-usb cable. The device should detect that it is being charged and turn itself on, thinking that it has enough battery to do so. If it doesn't, do so yourself.

6. While the device is booting, you have (at least I had) a short time period while your device listens for commands. In console type the following command: "adb reboot recovery" (try this from immediately after the device starts booting until it works, if it doesn't try again). This should reboot your into recovery mode.

7. If you do not have system flashables on your device, google how to sideload zip files. Get them here: http://xdaforums.com/g4/development/stock-h815-20a-stock-images-kdz-t3232282. Flash them (I flashed all, just in case, but system might be enough).

8. After flashing, you (if coming from any other rom) should clear data and cache as well.

9. Reboot the device and it should be working.