THE CHECK ENGINE LIGHT KEPT COMING ON AND I TOOK IT TO THE DEALER FOR REPAIR AND WAS TOLD "IT'S OK. FORGET IT." ON 01-09-2009 WHILE TRAVELING ON TEXAS HIGHWAY 60, I HAD THE CRUISE CONTROL SET FOR 70 MPH. TRAFFIC WAS NORMAL BUT CONTINUALLY PASSED ME AS IF I WAS GOING SLOWER. I PULLED OVER AT A CONVENIENCE STORE AND PARKED THE VEHICLE. THE SPEEDOMETER REGISTERED 45 MPH IN PARK. I CONTINUED HOME GAUGING SPEED BY THE OTHER TRAFFIC. THE VEHICLE WAS PARKED. ON 01-14-2009, MY WIFE AND DAUGHTER WERE IN THE VEHICLE RETURNING FROM SCHOOL. THE SPEEDOMETER APPEARED TO BE WORKING. AT APPROXIMATELY 3:00 PM WHILE DRIVING HOME, THE ELECTRIC DOOR LOCKS BEGAN TO LOCK AND UNLOCK THEMSELVES. AT THE SAME TIME, THE A/C WENT TO MAXIMUM HEAT AND HIGH BLOWER. MY WIFE STOPPED THE VEHICLE AND PUT IT IN PARK. THE SIDE CURTAIN AIR BAGS DEPLOYED, STRIKING MY DAUGHTER IN THE LEFT TEMPLE RESULTING IN A MILD CONCUSSION. ONSTAR NOTIFIED THE POLICE OF A COLLISION. I CONTACTED THE DEALER WHO REFERRED ME TO GMC CUSTOMER ASSISTANCE. THE AGENT TOLD ME THAT THIS KIND OF THING HAPPENS WHEN TRAVELING TOO FAST AND TURNING TOO SHARP. AN INVESTIGATOR WAS DISPATCHED TO GATHER COMPUTER INFORMATION AND DETERMINE IF THERE HAD BEEN A COLLISION. HIS RESULTS WERE THERE WAS NO COLLISION AND THE BAGS DEPLOYED PER COMMAND FROM THE VEHICLE CONTROL SYSTEM BASED ON THE VEHICLE TRAVELING 20 MPH AND TURNING TOO SHARP. THE VEHICLE WAS ACTUALLY TRAVELING 20 MPH ON A RESIDENTIAL STREET IN A STRAIGHT LINE. TURNING RIGHT WO