2026 GMC TERRAIN Complaints

The system that failed was the brakes, The car is availble for inspection. My saftey and others was put at risk due to not having brakes to stop. The problem has been confirmed by a dealer as a master brake cylinder failer The vehicle has been inspected by the dealer. There were warning lamps, message and other symptoms of the problem prior to the failure. They first appearead on December 4 2025

I was driving (roughly about 30 MPH) when my automatic braking kicked on and caused my tires to squeal to a halt. There were no other cars around me (thankfully) - otherwise I would have been rear-ended. Right before it stopped, it flashed the warning lights for a quick second. I wanted to report this issue in case others are experiencing the same problem and to hopefully help prevent it from happening to someone else. Very scary and could cause a serious accident. I turned off all of my automatic brake settings after the incident, as I believe it is faulty and don't want to risk it happening again.

The vehicle has been taken to the dealership at least 4 times. Each time for the same reason: when driving at 65 or higher, it sounds like it's on a flat. My screen also glitches when foot is taken off the break after a stop. The service advisor told me that there was a shortage of mechanics and asked me to bring it back next week (this is the response I have gotten each time). I have asked for a loaner twice and was told that there were none available. Therefore, I had to pay $40 to uber to work. Today, I said that I couldn't come back because it's the same issue and I have to work next week. He then let me speak to a service manager. The service manager drove it (with me in the passenger seat) and heard the sound. He noticed that it was not all of the time and that my steering wheel was a little shifty. When it was finally "fixed" (tires being rotated and some steering update), I was told to come back if I hear it again. I left at about 2pm and heard the sound again, as well as my screen began to glitch when I get off the break after a complete stop. I took a video of the glitching and took it back for both issues. I was told that some bolts were tightened and some update was done to the screen, and if I hear it again come back. On my way home at 4:35pm, the issues were not resolved.

I have brand new GMC Terrain 2026, I leased dog on Aug 4th 2025. After one week into driving the vehicle, OnStar, GPS NAV stopped working and the Emergency calling is not working. All features related to locating the vehicle through OnStar or through google stopped working, in addition to SoS not working. I took it to the dealership they said the Telematics module needs replacement.

Master cylinder , less then 1000 miles was pulling out of a parking lot and the brakes went out