It Really works for me.
How to instal LG Firmware using KDZ Updater
1. Download and Install USB driver for Lg L3 e400 from LG website or here
2.Download and install MSXML 4.0 SP3. here.
3.Download KDZ Updater here then extract it to your computer.
4. Download KDZ file according to your country or any compatible KDZ file. Download here
How to use KDZ:
1. Detach your external SD from your phone.
2. Remove your phone battery and wait for a few seconds.
3. Put your battery back to the phone.
4. Press volume - and + (or just in the middle of volume button) and power button at the same time.
5. wait till the phone screen turns to yellow (emergency mode) then release all the buttons.
6. Connect your phone to PC by using USB cable (your LG cable).
7. Stop or disable your antivirus or antimalware.
8. Run KDZ Updater as administrator.
9. Choose the following options in KDZ Updater:
Phone Mode: DIAG
and browse KDZ file is the one you downloaded, browse where you put this file and then select.
9. Click on “Launch Software Update”
10. If everything goes well, you will see “Finished” on KDZ Updater screen. Your phone will restart itself. You'll see the opening screen.
If something wrong happen it's usually because of the wrong download of KDZ file, broken KDZ Updater, or your antivirus.
I hope this could unbrik your LG L3 phone.
How to Root it.
After doing all the above now you can root your device again with this. Extract the file you just downloaded to your root of your computer.
Connect your device to the computer, then double click run.bat and wait till the device restart.
Now your device is rooted again
How to get CWM
Download from Google Play Rom Manager and download your CWM with this apk while online.