I was driving the vehicle on the highway and all of a sudden it slowed down to about 20 mph without any warning. I looked down and saw the traction control light and check engine light on. In the middle of the dashboard it said engine speed reduced. I backed down an entrance ramp to get onto a local road. After 1 hour the car was restarted and seemed ok. Not long after it happened again. I took it to the GMC dealer, they drove it 47 miles and could not get it to act up.I got the car back, drove it 70 miles home and the next morning it happened again, 3 miles from my house. I had it towed to the dealer. The dealer then replaced the throttle body assembly for $540. It has been fine for 2 weeks. In 2010, GMC decided not to cover this part under the engine warranty (as it did in previous years) and now assigns it to the emission system which is not covered. I have seen this problem listed all over the internet on many vehicles. It is a dangerous situation when the car slows down like this on the highway. Please add my complaint to the long list of people who have this problem. Thank you.

- Yonkers, NY, USA