What is the cause for a CAM POS diagnostic result for a 1997 Nissan Maxima SE with a 5-speed manual transmission?

cam sensor replaced dist' is found in timing chain housing, vehicle also has crank pos sensor down on crank and a speed sensor at top of transmission, all of which work with pcm/ecu, some are primary and secondary signals, cause is malfunction/intermiattent failure of sensor. try used part 1st if possible.