Tutorial how repair boot Optimus 3D by USB!!
No need to explain much, the steps are the same as I9250 to repair boot..

1. Connect phone without battery,phone detect OMAP4430
2. Install driver omap "inside folder have drivers"(omap4boot-for_optimus-v1.22 modified by XcachorroX®\usb_drv_windows)
3. Run file start_fastboot.bat and follow the instructions,after this you see logo LG in phone,
4. now enter downlaod mode "connect phone without battery press volumen+ and connect cable,now enter download mode,run SmartFlashTool_External.exe and open folder BOOTV21E select BOOTV21E_AP.bin & BOOTV21E_CP.fls after press Start Button.
5. After all this steps you can write any firmware to phone,enter download mode " connect phone without battery press volumen+ and connect cable,open LGtool select model and select firmware......and rest you know all there is no need to explain

PS: Original Solution is from wkpark but not have in list P925G "roger version" i edit soft and add on list this model and work with same loader/u_boot P920 and correct some errors in the procedure to repair.

/images of the procedure/




SmartFlashTool_External+BOOTV21E files.rar
omap4boot-for_optimus-v1.22 modified by XcachorroX®.rar