To do a factory setting to LG brand TVs (for all models) you have to enter its service mode option. To enter its service mode option; you should have a special type remote control, called the Service remote control. It has a special button 'Instart button". You should press that button to enter its service mode. The normal remote control supplied with LG sets, won't have this special button. This remote control can be purchased from the LG service centers only; and in most cases, they will refuse to sell it to you, and will ask you to give your set for service to them. This is a business trick, done by LG. The only thing you can do is a hard reset. If you can't rectify the fault, be rady to give LG service center a good amount of money. There are two methods to reset TVs. The first is simple to do; a Hard Reset. The other is somewhat skilled; is a Factory Reset (System Reset). To make it a hard reset, just unplug the TV from AC mains wall socket, and re-plug it back after 15 minutes or so. If you do this by overnight is better. This procedure will make it a hard reset. If you want to make it a system reset [Factory Reset]; you have to enter its service mode option, and select the factory reset option. If you wish to get some details; check the site linked here. Pull up older posts. http://electronicshelponline.blogspot.com/
Service mode entry, adjust and exit procedure to many popular brand TVs are given. Never forget to exit the service mode, after all adjustments have been done.