I was on my way back from a beach vacation Saturday along with two other vehicles driven by other family members. I drive a 2016 Sierra 1500 SLT with 30,000 miles on it. After driving for 1 1/2 hours with many opportunities to use my brakes, our convoy needed to make a stop to turn left. To my great surprise the power assist was not working. At first I thought I had no brakes at all. I pressed hard with both feet and stopped the truck before I rear ended my son in law and his family. Scared me to death!! I phoned ahead to our lead car and told them I had serious vehicle problems. There’s no way I could drive 400 miles with heavy traffic safely. We searched for the nearest GM dealer and selected J. M.Jackson in Andalusia, Al. Even though it was a Saturday, the sales people called the service manager who came in along with a service tech. Shorty I had a new vacuum pump installed and there was no charge since GM had issued a service bulletin. Outstanding service from this dealership. They were wonderful to deal with. But now I’m worried about another failure. I barely avoided an accident this time. There was absolutely no warning. After the initial failure to brake properly, I got a service brake assist message. I wonder what if anything GM plans for the long term? I can’t drive this truck or let my wife and grandkids drive it wondering when this will happen again.