Smog guy says I need a new engine computer?

Both sensers are good he said just seems if there's a faulty wire going to the os it would throw the computer off making it seem bad shouldn't he replace the wire first the cheaper fix instead of just saying I need a new computer he said he checked the wires and they were fine but one is not fine its metal on metal rubbing all frayed that can't be good he's going to replace computer and seem like the wiring will burn it out in a short amount of time. Thank you for your time and help.