GMC Envoy XL - 2006 has powered down three times while driving on a major interstate at approximately 65 mph during rush hour traffic. No warning lights prior to the power down. The vehicle slows to 15 within about 60 seconds. The first time, in approximately 2008, I was able to pull over two lanes to the breakdown lane and the power came back on while I was still coasting. I was told by GMC that without the light on they couldn't do anything. The second time in early 2012, the same thing happened during rush hour - there was no breakdown lane. When I went to GMC the light went off. I was told that I had a useful life of the car and it was getting old (135,000) miles and I should replace it. They said they could not do anything. It happened again last week on the interstate. I brought my car to my regular mechanic, non GMC, who coordinated with another GMC dealer for me. They fixed some codes they said were a problem. It happened again after having the car for 2 days. They fixed it again. We don't know if it's really fixed. This is a huge problem. GMC has no idea what they need to do to fix this. I have not seen service bulletins that relate to this. Powering down to a speed below minimum speed on a major highway is very dangerous. I do not trust this vehicle and feel very unsafe in it. Somebody needs to do something about this.

- North Andover, MA, USA