How to Root Gingerbread Upgraded LG Optimus One - By Downgrading to Froyo

Rooting is only applicable for those devices with Froyo version as of now. So if you had flashed the Official Gingerbread to your Optimus One, what we have to do is to downgrade your firmware back to Froyo firmware. By the way I reverted back to Cyanogen because tweaks were absent.

So here are the procedures:

1.      1.  Download the Froyo KDZ version from here.

2.       2. Download LG’s firmware updater application appropriate at your PC’s OS KDZ_firmware_updater. Extract it to folder and install msxml.

3.       3. Connect  your LG Optimus One and run KDZ_FW_UPD.exe Don’t turn USB Storage on your phone.

4.      4. In the software window, choose TYPE as 3GQCT and DIAG for the PhoneMode

5.      5. In the KDZ File, click on the folder button and look for the firmware you’ve downloaded in Step no. 1

6.      6. Last step Click on the Launch software update button, wait for it till it finish its job. Don’t worry if your phone flashes “Emergency mode”. Reboot. Don’t unplug USB cable till it totally boots up.

If you’re stuck on android logo screen during the first boot (which I know you will), turn off first the phone by removing the battery. Do a hard reset by holding the Volume Down+Home+Power buttons.


Then you can now root your device with Gingerbreak or z4root. Want to try Cyanogen? Follow the instructions here.

Update:


I remember what I did. You have to Disabled the LGE Virtal Modem in your PC (control panel/system properties/Hardware/Device manager/LGE Virtual Modem)

If it still doesn't work, uninstalled the ms visual c++ redistributable software coz it might interfere in the updating process and detached all other USB devices
You should enable USB Debug (it is a must).