[Nexus 5 General] bitdomo:
Only you are the responsible if you brick your device. I tried the whole method a few times and no problems so far, but random things could happen.

What is LG Flashtool?

LG Flashtool is used by LG to flash firmwares to phones.

What are the advantages of using LG Flashtool?

The flashing process is faster than the fastboot flashing process.

[*]You don't need unlocked bootloader to flash.

[*]It locks bootloader and resets tamper flag.

What are the disadvantages of using LG Flashtool?

Your battery level must be over 10%.

[*]It changes the device factory version. If your phone had KFS78N version of android initially and you flash a KRT16M firmware, then the device factory version is going to change from KFS78N to KRT16M.

[*]LGD821AT-00-V10a-NXS-XX-OCT-01-2013-KFS78N-USER-16G+0 ==> LGD821AT-00-V10b-NXS-XX-OCT-31-2013-KRT16M-USER-16G+0

[*]This info stored on the misc partition at the 0x00008800 offset. You can change it back to the original one if it bothers you.

[*]To get your original device factory version then just open the log file in the LOG folder which is created at the location of the DLL and TOT file and search for "device factory version" text.

[*]I made a flashable zip (mirror) which bacups the device factory version to /sdcard/version.txt. After the backup just copy the txt to your PC. Then here is the restore zip (mirror). Just place the version.txt to /sdcard and flash the zip to restore.

Preparation (you have to do it only for the first time)

Download LG drivers (mirror)and install it.

Download LG Flashtool (mirror)and install it.

Create a folder where you put the DLL and the Firmware file.

Download DLL: D820 (mirror) (North American version) D821 (mirror) (Global version). Place the DLL to the created folder.

Download firmware: D820 (mirror) (North American version) D821 (mirror) (Global version) Place the TOT file to the created folder.

Turn off the phone.

Hold down volume_up key then connect USB cable.

If you see these screens bellow then the phone is in Download Mode and you are on the right path:

Let windows to install the drivers for the new devices.

Change the port number to 41:

Open Device Manager.

Right click on LGE Mobile USB Serial Port (COMxx) (where xx is the port number).

Click on Properties.

Select Port Settings tab

Click on Advance...

Change COM Port Number to COM41

If you don't want to flash any firmware yet just hold down the power key for 10-15 secs then your phone turns on.

Flashing the firmware

Enter your phone to Download Mode.

Start LG flash tool.

If Model Config window does not start, then click on the sign with two cogwheels.

Place a tick next at Select Manual Mode

Click on "..." and select the DLL file for your device.

Click on Add to add the TOT file.

Click OK.

Click on the yellow arrow sign to start flashing.

If you see READY!!, then reconnect your phone. Then "Waiting for Connection" text will appear in the COM41 window.

At 80% the phone will shut off, don't be scared.

DONE! The LED on the phone is starts blinking green. Just remove the usb cable wait until the blinking stops then turn on your device.

Restore device factory version (optional)

Create a new txt file called "version.txt" and open it.

Paste your device factory version from the log file located in the LOG folder where the DLL and TOT file are. Search for "device factory version" text in the log file

Copy version.txt to the root of the sdcard (/sdcard).

Download the restore_device_factory_version.zip (mirror).

Flash restore_device_factory_version.zip in recovery.

Videos

LG Flashtool:

[YOUTUBE]rnD6WT1JHcs[/YOUTUBE]

Restore device factory version:

[YOUTUBE]LbhUzr5vHSg[/YOUTUBE]

Credits

All the guys from [REF] [TOT] Stock Firmware Collection for Nexus 5 (D820 & D821) thread.

In PDF ([URL="https://mega.co.nz/#!584SzYbC!hSiymZnhn1SVBqwjOY7qsXB4PvgPnYDwYRnMIid9pfE"].docx for translate[/URL]):
[URL="https://mega.co.nz/#!koRHkIYa!L6esc81aRvQ3PdbklRgdrQZTIu-vbhhbfC6mam4gIzo"]English-English_LGFlashtool.pdf[/URL]
[URL="https://mega.co.nz/#!lwZxhDLa!9L9HE0qjGZ3iIxi01m6nm1EYt23zllri8K9s__5Nmcw"]Magyar-Hungarian_LGFlashtool.pdf[/URL]