how do you test a crank shaft position sensor
 

I have a history fault code, "P0335B crank shaft position sensor A circuit performance".How can I test the sensor and it's circuit? Would a GM dealership code reader give me more info? Car is stalling but will restart. No fault light comes on. May happen once or twice a week or run fine for a month before stalling.Any help will be greatly appreciated. Car is a 2001 DHS.Stinger