Default nfc is not turning on.. plzzzzzz help

i recently bought an lg e975(intl) . everything was working well till today. . I don't know why but the nfc wont turn on , sometimes its greyed out. . sometimes the android beam is greyed out .. Sometimes when they're not greyed out the NFC ON/OFF switch returns to off if switched on..
um using stock JB 4.1.2 Rooted.. now unrooted (for warranty)..
i tried the lg hidden menu 3845#*975# NFC Test., it always fails...
plZzz help me ..
i already factory resetted the phone and flashed stock kdz but nfc still wont turn on..