2023 GMC Sierra 3500: check engine light

Filed Jun 1, 2025 · Transmission · WA

Formal Complaint Against General Motors and Dealership – Ongoing Warranty Issue and Vehicle Inoperability To Whom It May Concern, I am writing to formally escalate a serious and unresolved issue regarding my vehicle, and the lack of meaningful action taken by both General Motors (GM) and an authorized dealership. My case is not isolated, it mirrors the experience of thousands of other GM customers facing the same known mechanical defect, as widely documented in online forums and communities. On [XXX], I purchased a used 2023 GMC Sierra 3500 Denali with approximately 25,000 miles from a dealership. The vehicle included the original factory warranty, and I also purchased an extended warranty for additional coverage. On [XXX], at approximately 26,000 miles, the truck unexpectedly entered limp mode and the check engine light came on while I was driving with my children. Please note—this truck is equipped with the Allison Transmission, which is marketed as one of the most reliable transmissions available. I immediately took the vehicle to Blade Chevrolet in Mount Vernon WA, the nearest dealership, where it remained for nearly a week before a diagnostic was completed. I was informed by the lead mechanic, Jason Visten, that the issue was a failed valve body solenoid #1—a component he clearly identified as a known and widespread issue within GM’s system. Mr. Visten further stated that GM has not been responsive to the dealership's requests for this part, which is currently on national backorder with no estimated timeline for availability. I was even told this specific part is being built for new vehicle production and are being prioritized over parts needed for warranty repairs, leaving my truck unusable and indefinitely sidelined for up to a year per Blade Chevrolet. I contacted GM Customer Service directly and received the same generic response. Also worth mentioning I almost got rear ended cause of limp mode activation and transmission locked up. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA

Filed May 16, 2025 · Transmission · CO

Transmission issues 5/5/2025, bearly 15,000 miles on it, was excelerating from a stop heading down hill when rear tires locked up, engine downshifted, engine light and limp mode flashed across my screen. threw it into nutral and coasted to next signal and pulled into gas station back parking lot. No codes pulled. called dealer to share and they knew exactly what was wrong with transmition value body problem. but is my transmission ok? Towed to dealer, no fix in sight. 7th vehicle at dealer with same problem. Others been there for months waiting on same part. Thank God I wasn't towing anything, but now I have to pay for rental and they say they are waiting on parts??

Filed Apr 25, 2025 · Transmission · 33,800 miles · FL

The contact owns a 2023 GMC Sierra 3500. The contact stated that while hauling a trailer and driving approximately 40 MPH, the contact attempted to merge into traffic and the message "Restricted Power Mode" was displayed. During the failure the transmission failed to properly shift into a higher gear, and the vehicle failed to exceed 67 MPH. The contact stated that later while driving at an undisclosed speed, the check engine warning light illuminated. The vehicle was towed to the local dealer who diagnosed that the transmission valve body was faulty and needed to be replaced. The vehicle was not yet repaired. The manufacturer was notified of the failure. The failure mileage was 33,800.

Filed Jul 24, 2024 · Transmission · MN

Transmission had a hard shift which jolted the truck switching gears to a lower one unexpectedly. It caused my body to jerk back. It happened 3 times. 2 were mild but the 3rd time was extreme. Always while accelerating. Average speed was about 50 mph when this occurred. Dealer has confirmed a failure of the transmission valve body. If the transmission were to be put in park while traveling, it could cause major accident and injuries. After the 3rd time the engine warning light came on and the truck went into limp mode.

Filed Apr 8, 2024 · Transmission · NV

I received a p0747 and p0700 transmission codes on my GMC sierra 3500. It would not engage above 3rd gear and I almost was rear ended by a Semi truck because I was unable to speed up. The vehicle CEL turned on and "Engine power reduced" notification appeared on my cluster. Engine RPMS were at 2800 rpm and my speed limit would not go past ~40mph. I currently have my vehicle being inspected by the local dealership. The vehicle currently has ~19,300 miles