ABV came on. SCR alerted I needed service. On a 25 mph road I no longer could brake randomly

The contact owns a 2026 GMC Terrain. While driving at 28 MPH, the RPM became elevated to over 3,000 RPM. There was no warning light illuminated. The contact immediately pulled over and then resumed normal operation after the failure. The vehicle was taken to the dealer to be diagnosed; however, no cause for the failure was found. The contact was advised to bring the vehicle back to the dealer if the failure reoccurred. Approximately one week after the initial failure, while driving approximately 30 MPH, the transmission unexpectedly downshifted to L2. There was no warning light illuminated. The contact pulled over and restarted the vehicle, and the vehicle was taken back to the dealer. A diagnostic test was performed, and the contact was informed that the transmission needed to be rebuilt. The manufacturer was notified of the failure and was provided a case number. The vehicle remained with the dealer unrepaired. The failure mileage was approximately 1,300.

The contact owns a 2026 GMC Terrain. The contact stated that there was an abnormal clunking sound coming from the front driver’s side suspension while driving over bumps in the roadway, and while braking and turning the steering wheel. No warning lights were illuminated. The vehicle was taken to a local dealer, where a test drive was performed; however, the dealer was unable to determine the cause of the failure. The vehicle was not diagnosed or repaired. The manufacturer was not notified of the failure. The approximate failure mileage was 14.

Purchased NEW 2026 GMC Terrain Elevation, and it came with NO User Manual. I was told by the dealership (Al Serra GMC in Grand Blanc Michigan that i could either purchase one for $50.00+ dollars, PLUS TAX & $25.00 SHIPPING, or d/l it via the infotainment system in the car, WHICH DID NOT WORK! Talk about [XXX] A VIETNAM VET!!! We are both [XXX] old & need a manual, so bought a reproduction of the original via eBay for $50.00. At least GM could reimburse the cost of the manual… INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

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