2025 GMC SIERRA 2500 Engine Problems

Component / System Failure The exhaust system, specifically the exhaust manifolds and previously the EGR system components, appear to have failed or malfunctioned, allowing exhaust gases to enter the passenger cabin. The dealer initially replaced the EGR cooler diverter on December 23, 2025. However, the condition persisted. On February 3, 2026, cracked exhaust manifolds were identified by the dealership, and a major front-end teardown was advised to complete the repair. The vehicle is currently available for inspection upon request. ⸻ How Safety Was Put at Risk The malfunction allowed exhaust gases, including carbon monoxide, to enter the passenger cabin during vehicle operation. Carbon monoxide readings inside the cabin reached up to 50 parts per million (ppm) while driving. Carbon monoxide is a toxic gas that can cause: •Headaches •Dizziness •Impaired concentration •Nausea •Vision disturbances Because carbon monoxide is odorless and colorless, this presents a significant safety risk, particularly at highway...

Burning an unusual amount of oil. Have seen several instances of blue smoke in the exhaust. Have had to add over a quart of oil twice in less than 6500 miles.

We were towing a fifth wheel camper with our truck on an interstate highway in Pennsylvania when our serpentine belt burst suddenly and without warning. Our truck is a 2025 model with only 10,000 miles driven. We lost all power steering and power brakes of both the truck and the camper and the motor shut off while we were driving at 65 mph. My husband struggled to gain control of the truck and camper which was severely fishtailing and was eventually able to get over to the shoulder and stop the vehicles. We were towed to a GMC dealership where a factory technician happened to be on site providing an in-service for the dealership's service team. He inspected our truck and we were told that he said that GMC is aware of catastrophic failures in these serpentine belts. We were also told that he took photos and was sending a...

The contact owns a 2025 GMC Sierra 2500. The contact stated that while driving at an undisclosed speed, the vehicle failed to accelerate as intended while depressing the accelerator pedal. The check engine warning light was illuminated. In addition, the contact stated that the RPM was fluctuating while driving. The vehicle was towed to a local dealer however, the vehicle was not diagnosed or repaired due to the warranty. The manufacturer was made aware of the failure. The failure mileage was approximately 600.