error 4013?

recently faced the problem with error 4013 got it checked at the service center they said for the complete change of mobile (exact words replace of mobile) as hardware is damaged..... phone is still functioning as it starts - no motherboard issue, it gets connect to pc/lappy - no port issues, display- no display issue(wanted to replace the screen), else i suppose might be working....

in all would like to learn the basic of this error.....