The first time was Nov.2014 when the check engine light came on solid along with the traction control light engine power was reduced and the engine vibrated and would not go over 20 mph.I left the truck parked for 3 days and when cranked the truck all lights were off and the truck ran fine.once in Dec. 2014 and once in Jan.2015 the solid check engine light came on but the truck ran fine and after a few days went off. The first week of Feb. 2015 the check engine and traction control light came on engine power was reduced and engine vibration. I was able to drive slowly only to an independent mechanic that I normally go to because he was closer than the dealership and I wanted it check immediately since the warning lights were on.his codes showed the throttle body with sensor needed to be replaced.he stated he left the codes in even though the warning lights went off because he thought this work was covered under warranty.I immediately called the dealership and they wanted to make an appointment for the following week and when I told them all the warning lights had went off they stated it would probably be a waste of time to check on their computer. I told the dealership service dept. About how you don't know when this will happen and when it does you are basically stranded because the vehicle will barely move. The next week Feb.11, 2015 it happened again and all 3 times I was lucky I was not in alot of traffic or traveling at high speeds or on a steep grade.if I would have been there may have been a accident. I had to leave the truck in a parking lot and the next day took it back to the independent mechanic.I called the dealership and again they wanted to make an appointment and they stated the work was not covered under warranty so my mechanic came up with the same codes and fixed the problem.called GM and explained the unsafe situation and got no customer service.

- Chatham, VA, USA

The windshield and the side windows of my new 2010 GMC Sierra 1500 wt, have an extreme tendency to fog over in temperatures near the freezing point. I have read, and observed, that the ac compressor becomes automatically disabled when the outside temperature gets near the freeze zone (I think the actual threshold is somewhere around 40 degrees F). With the ac disabled, the defrost mode cannot keep the windows clear. The problem is magnified when there are two or three individuals in the cab. At that point, it is exceedingly difficult to clear the side windows, even to the point that frost forms on the inside window surface! very recently, while traveling to work during my 40 mile commute, I was running the ac, with the temp control set to a comfortable level and the blower about the medium setting and flowing through the main vents. The outside temperature was, apparently, hovering near the point where the electronics disable the compressor. The windshield and both side windows fogged over suddenly. I noticed the ac light was out, so I switched to defrost mode and hi blower. The windshield did clear in about a minute or two, but all of that happened while driving down the turnpike at 70 mph. This seems to be a significant safety concern....at least for me and my family. If the ac compressor had stayed enabled, this would never have happened. It is very difficult to stop condensation buildup if you cannot run the ac to dry the cabin air. This design configuration seems to present an issue of safety. I am not sure if it is just this particular model. I suspect so, since it is the base model truck. We have a 2011 GMC terrain, which does not present this issue. I have contacted the dealer about this issue now for 3 years with no resolution. They act as though you are an idiot.

- Berea, KY, USA

The contact owns a 2010 GMC Sierra 1500. The contact stated that when the pistons were loose and struck the cylinder wall, it would loosen up the engine and caused an abnormal knocking from the engine. The dealer was notified of the failure who advised the contact that the failure was nothing to be concerned about and was not hurting the engine. The manufacturer was notified who stated to the contact that they would speak with the dealer to determine the remedy for the failure. There were no recalls for the failure. The failure mileage was 5,000 and the current mileage was 24,000. Updated 01/10/12

- Waynesville, NC, USA