2024 GMC CANYON Power Train Problems

Truck began idling very rough. Went straight to the dealership. They shut the truck off and it would not restart. No CEL or messages on the dash. Tear down reveled a failed exhaust valve in cylinder #4. Truck has 10,000 miles. A replacement engine has been ordered under warranty. Luckily, we happened to only be a few miles from a dealership when the failure happened. There was no warning, no prior symptoms what so ever.

We were traveling not once, but twice at a high rate of speed (75/80mph the legal limit) the vehicle gave one message: Service power steering next message: reduced acceleration. The check engine light turned on, the truck itself jerked and we almost lost control of the vehicle (both times) on the highway. We were thankfully able to pull over and pull to a complete stop. The vehicle was still on, it still ran but I saw an autozone close by both times and received a code for the check engine light. The dashboard both times lit up like a Christmas tree on both occasions before spazzing out. We have taken the truck twice to a nearby dealership and they were able to service and “fix” the problem however they said that the first time, and here we are a second time. The dealerships we took the truck to are aware...

The valve body on GM's 8 speed transmission is a known fail point for many GM truck owners. I believe the NHTSA should investigate this for the extreme risk of an accident. My truck has been inoperable for a month awaiting a back ordered part. When driven, the truck displays erratic behavior and will downshift and decelerate rapidly and without warning. The risk of being rear-ended is very high.