I STARTED OUT DRIVING ON HIGHWAY ROAD AT APPROXIMATELY 5:45PM TRAFFIC WAS MODERATE, MY SPEED WAS ABOUT 30-35 MPH. ALL OF A SUDDEN I HEARD A CLUNK AND THEN ALARM DING FROM THE DASH AS WELL AS MESSAGE "SERVICE STABILTRAK" THEN "REDUCED ENGINE POWER". I WAS UNABLE TO GO ANY FASTER THAN 25MPH. I DROVE IN THIS MODE FOR ABOUT 2 MILES IN TRAFFIC, WHEN REACHING OPEN HIGHWAY (NO TRAFFIC) THE VEHICLE WOULD NOT SHIFT BY ITSELF. I HAD TO ACCELERATE THEN LET OFF THE GAS, TAP PEDAL THEN THE VEHICLE WOULD SHIFT. I WAS ABLE TO DO THIS MULTIPLE TIMES UNTIL REACHING ABOUT 45MPH. I PULLED OFF INTO A NEIGHBORHOOD, SHUT VEHICLE OFF TO SEE IF THIS WOULD RESET SOMETHING, IT DID NOT. THE VEHICLE WAS IN THIS STATE WHEN I ARRIVED AT THE DEALERSHIP SERVICE DEPARTMENT AT APPROXIMATELY 6:05PM. DEALERSHIP LOGGED FOLLOWING ON SERVICE REQUEST: 5043 FOUND CODE P228C RAN DIAG COULD NOT DUPLICATE PROBLEM FUEL PSI AT SPEC RAISES TO SPEC TEST DROVE ON HIGHWAY DID NOT DUPLICATE CONDITION FOUND NO BULL ON CONDITION TEST DRIVE NUMEROUS TIME, COULD NOT DUPLICATE CONCERN. MILES OUT 5067. *TR
2013
UNKNOWN OR OTHER
WHILE DECELERATING FROM ABOUT 35 OR 40 MPH WHEN YOU APPLY THE BRAKES THEN COME TO COMPLETE STOP THE VEHICLE ON THE REAR END WILL START TO LOUDLY THUMP, IT STARTS OUT SLOWLY THUMPING AND BEGINS TO SPEED UP AND WHEN YOU START TO RELEASE THE BRAKE IT BEGINS TO SLOW DOWN AND STOP ONCE ONE BEGINS TO ACCELERATE. WE HAVE HAD THE ISSUE ONGOING FOR ABOUT 3 MONTHS NOW, IT STARTED ABOUT 2 OR 3 WEEKS AFTER WE GOT THE VEHICLE AND IT HAS BEEN IN THE SHOP ABOUT 6 TIMES. THE VEHICLE HAD ABOUT 2200 MILES ON IT AND THE DEALER SAID IT WAS A 'LIKE NEW' LOANER VEHICLE. THE MECHANICS SAID THEY THOUGHT IT WAS A EXHAUST, SOMETHING WITH THE REAR BRAKES, OR MAYBE A PANEL IN THE BACK OF THE VEHICLE, THEY HAVE TIGHTENED, AND REPLACED ALMOST THE ENTIRE REAR OF THE VEHICLE AND THE PROBLEM STILL PERSISTS. THEY CANNOT FIGURE OUT THE PROBLEM AND I AM AFRAID IT MIGHT BECOME A SAFETY HAZARD. THE DEALER HAS CALLED GMC AND THE DEALER SAID GMC WILL NOT DO ANYTHING FOR US. *JB