I was driving my new 07 Burb the other day and crossed a manhole cover in the street. The service traction control light came on---went to the dealer and they couldn't find anything--managed to reset the tire pressure sensor and somehow that took care of the traction system light. Now the cruise control works just some of the time. The power indicator shows on the switch by the steering wheel, but the cruise won't engage and no light on the dash. What gives???