Press and hold Settings for 7 seconds, then enter 1105 .
If you can still access the standard user interface, this is the safest method: Lg Tv Service Menu Code To Factory Reset
To factory reset an LG TV, you can use the standard menu or advanced "Service Menu" codes. The service menu is primarily for technicians and should be used with caution, as incorrect changes can permanently damage the TV. Direct Service Menu Reset Press and hold Settings for 7 seconds, then enter 1105