I have a 2011 Regal Turbo and have been having a couple of issues dealing with an uncommanded braking.
It starts when I first put it into drive and start driving. When it happens (so far 3 times in the past month - the last time I called Onstar to do a diagnostics check - no codes) I can tell the car does not accelerate like it should (yes Id prefer the GS but I will not own a car with a black interior here in Texas) and when I take my foot off the accelerator there are 3 things that are noticeable -
1. The car does not coast but it starts slowing (noticeable difference).
2. The brake peddle feels a lot stiffer than normal when I do brake.
3. When I have the driver information center set up to show instantaneous fuel economy, its noticeably lower than what it would be both when coasting, cruising and accelerating.
When its happened, Ive stopped, turn the parking brake on then off, pressed hard on the brake peddle as well and put the car back into park. On the first time cycling the parking brake seemed to help fix it. But the other two it did not. The later two times it would go away after driving a few miles. I used to use the parking brake and thats when it started (yes Id turn it off prior to moving the car). Since it started, Ive stopped using the parking brake.
I only have 24K miles on it and it did not happen before I moved to Texas. I was in an area that did get warm, but not as hot as it does here in Texas so I dont know if its an issue with heat or not.
I have a Buick dealer looking at it and Im getting the impression that they are more concerned with finding codes (which are not there) (for pay purposes - the tech gets paid by the job not but how long it takes to trouble shoot the problem and then fixing it).