2001 GMC Sierra Cruise Control

The cruise control dosn't work on my truck. I thought that it might be the switches on the steering colum at first so I disconnected the harness plug on the cruise control servo under the hood of the truck and took some voltage readings while pressing the various buttons and all of those are working properly, and I also checked the cable going from the servo to the throtle body and it appears to be good and connected. So the question is where do I go next/what else can I check myself before going into the dealership. The truck is a 1500 with 5.3 v8. Thanks