Any controls that are on the steering wheel must maintain contact through slip rings when the steering wheel is turned from side to side and it is this cable that frequently fails on any car with steering wheel mounted controls. A wiring diagram is needed to make sure you are properly checking continuity of the proper wires. The switches and actuators for the cruise control can be checked at the cruise control module but again proper wiring diagram is needed. There is a company that independent auto repair shops "buy" their information from that offer a very reasonable service to do it yourselvers. You get a one year subscription to year make and model specific repair procedures, service bulletins, component locations, wiring diagrams ect.... great quality information same as the professionals have ,much better than generic workshop manuals from parts stores, much cheaper than the factory manual. http://www.alldatadiy.com/
Another solution to this problem is a bad multifunction switch. This is a common problem and the multifunction switch has a tendency to go bad, which directly effects your cruise control. A good indicator of your multifunction switch being bad is a your cruise control does not work and your air bag indicator light is on. These are generally good indicators that your MFS for short is bad.