The contact owns a 2025 Buick Envista. The contact stated that while driving at an undisclosed speed downhill, the vehicle started to shake abnormally. The contact stated that the check engine warning light was illuminated. The local dealer was contacted, but the vehicle was not diagnosed or repaired. The contact stated that the vehicle remained with the local dealer. The manufacturer was not made aware of the failure. The failure mileage was approximately 400.