GMC Repair: ABS, personal experiance, speed sensors

Question
i have a 99 gmc sub, K2500 and recently the ABS has started acting up. (intermitenly) In the morning, it occassionaly kicks in even though the weather is sunny and warm and the roads are dry. after a few times, the ANS light will come on and stay on for a hour or so, then turn off again.
should i assume that one or both sensors on the rotor/bearing hub are shot and need to be replaced or could it be something else?

Answer
George, ABS gets complicated and takes specialized equipment to diagnose properly.  You will need to have the system scanned to see what the trouble codes are and start there. quessing can be costly, so be sure to scan the system. Now, from personal experiance, 90% of the time when an abs system kicks in for no reason, it is usually the front wheel speed sensors, but that's just a quess and no way a diagnosis of your problem. Good luck and please let me know how you make out.  MANNY