Either one of them can cause a misfire condition. If it has the check engine light on, get it scanned. Even if its not on, It should show a history code or a hard code if it has misfired though. If you crank or cam sensor are intermittently not working, It may show a cam/crank correlation code. If I know a crank or cam sensor is out, I will go ahead and replace both. Just to be on the safe side.