I am so happy that I wanted to share this with you. As I still have headache from googling how to flash back your stock rom (which didn't work out because the flash tool gave an error every time at 15%), I can save you a lot of headache with this very very simple fix.
For some people the tool works just fine, but when you have some google bootloader or a newer freegee unlocked one and you want back to stock, lots of people cant follow this thread because of the error at 15%.
The fix is EASY and I found it on the Optimus L9 section, thanks to that guy on XDA.
Follow exactly Davevinci's great thread except for one thing:
Step 4 is now:
4.GO TO DOWNLOAD MODE POW+BOTH VOL BUTTON PRESSED+CONNECT USB
But step 4 should be:
- Boot up your phone in any stock based rom, for example SAVVY Rom V5
- Enable USB debugging and connect your phone through USB using the LG PC Suite option (make sure to kill PC suite in tast manager).
Now you should see the driver installation of LGE Android MTP device as usual and then just run the flash tool from the guide. Also de mode DIAG is now the right one. The flashtool will reboot your phone to download mode automatically when it's needed.
Still an error? Don't worry, disable virus scanner and firewall and just reconnect your phone. I got an error one time, during flashing, but I followed the steps the flashtool suggested me and now everything went fine.