Crank or cam sensor???

[Toby Cashion]

Got a truck that the tach works for about 5 seconds then drops to zero. After about a minute of running truck kinda revs up on its own real rough and tach starts working for a second, I dont have my scanner here to read the codes. Does this sound like a Cam or Crank sensor? its a 98 24 valve.
Also the truck doesnt seem to be charging. What works off the cam sensor and what all works off the crank sensor? And were is the crank sensor located?

 

[Rob24vCTD]

Crank sensor is just above the starter, it also controls the tach and charging on 98.5-00 motors.

 

[ChrisNickerson]

I had the same problem. Crank sensor fixed mine. Good luck