the manual only points to cpu pcb. On several machines all I had to do was to disconect the pc boards, clean the connectors and reseat them. only once did I have a bad cpu board.
I'm with OneTek on this one. In times past, when I'd have that code, it was almost always due to the boards being in need of a good cleaning. I'd pull each out seperately, dust and clean contacts really well. Should work for ya. Good Luck...