Nikki S

I have the 2019 GMC AT4 also. They told me it was a faulty master cylinder

I had the same issue yesterday. Went to pull out of the gas station and I had to push my foot as hard as I could to come to a stop. Hardly any brakes. I had the same error messages shown in the pictures in this forum. My truck is at the dealership. They called and told me it was a faulty master cylinder. I've only had the truck a few months. Brand new 2019 GMC AT4. They said the part is on backorder and they have no idea when they will get it in. They said with the strike there are a lot of parts on backorder. I called GM Headquarters to report the issue. It is important to get this issue documented to have a recall put in motion! I urge everyone to call GM headquarters to report the issue! I also urge everyone to file a report on www.safercar.gov because they will investigate and if they have enough complaints they can make the recall happen. 11/8/19 - I picked up my truck today. Everything has been fixed. There was a delay getting the replacement part which I believe to be due to the strike. I'm sure this is issue is going to end up being a recall. It all depends upon how many people call and report it. If you have to wait for your truck longer than a month, you definitely should call GM Headquarters and have them open a case. When your truck is finally fixed, they can offer you compensation for your loss.