This is a friends phone. It was given to him and I do not know the history of it. I pulled the phone apart and reseated all of the cables, still stuck on the white screen and same errors. I replaced the LCD thinking that could be the problem, same thing. When I flip the silent switch, the phone does not vibrate, indicating its not powered on. When I plug the phone in, iTunes will detect it, but says it needs to be restored, so I select "restore and update", it starts the restore then gives me error 21. The phone will not turn on otherwise. I even went as far as replacing the battery. I can put it in DFU mode, but the backlight doesn't come on. I've tried all four USB ports and still have the same issue.