If my 99 gmc x-cab is running in a parked position, my fuel guage will read empty until I rock back and forth or drive. Also my tow/haul stopped working. Is there a fuse? I looked but didn't see one.

let me know if you figure out what is wrong... mine is doing the same thing.

Hi! my dealer had my fuel guage today on the warranty. the problem was in the fuel tank. it's a bad work of the sensor. Now my fuel guage is OK!

Your [B] is not working properly, you have to drop the tank to remove it and its part of the fuel pump assembly. Unless your truck is under warranty it is not covered and can cost a pretty penny. :2cents:
-Jimmy

FUEL GAUGE SENDING UNIT,, sorry.. =)