*Median odometer reading when the problem happened, where owners gave one. One complaint can name several problem areas.
Unknown or other
Transmission will not shift into high gears throws engine code
Jul 7, 2026Power train
VIN: [XXX] Make/Model/Year: 2020 Chevrolet Silverado 3500HD, Duramax L5P, Allison 10L1000 Recall: N242454440 / N242454441 (NHTSA 24V797) Description: Vehicle had N242454440 completed May 2026 (TCM software update for harsh shift / wheel lockup). On XXX at 103k miles, vehicle exhibited same defect: harsh downshift 8th-9th gear, CEL on. Diagnosed as TCM failure per N242454441. Vehicle at O'Reilly Chevrolet Tucson since XXX (18 days out of service as of XXX). Dealer states TCM on national backorder, SPAC ticket opened, no ETA. Dealer denied courtesy transportation stating out of warranty at 103k, despite recall being federal safety recall with 15yr/150k special coverage. This is failure of…
Jul 30, 2026Power train
Since buying the vehicle Iâve had issues with the truck going into limp mode with codes p0700 as well as p0747. I have taken it to the dealership twice now, when it has arrived the codes were no longer there. Every time the truck went into limp mode the transmission would get stuck into 5th gear stuck at 45 mph. The problem with the truck started at 48,000 miles, the truck currently has 60,000 miles and the problem has been more active. With the dealership not wanting to resolve the issue the truck was taken to another shop to try to fix the transmission.
Sep 1, 2025Fuel/propulsion system
The fuel pump driver module. I filled my truck up with diesel and it drove home fine. Later that afternoon left the house and got half mile down the road and the truck just shut off with no warning lamps or message. When this happened, you could not steer the truck and the brakes barley worked, now after the truck cut off a message came to shift in neutral. I was lucky no one was on the road at that time. Now had this happened the day before when I was coming home pulling a 40ft fifth wheel, this could have been catastrophic. When this fuel pump module goes out you have no warning the truck cuts off and you have no steering or brakes. This module needs to be recalled, and something else…
Jun 30, 2026Power train
The transmission, without warning, intermittently locks the rear wheels when towing a 13,500 lb 5th wheel RV. It occurs when going uphill and the transmission downshifts to maintain torque. The "D" on the gear indicator on the dashboard also flashes 3-5 times. This is a known issue with the Allison approved (but GM made) transmission from model year 2020 to 2022 (NHTSA 24V-797) and is to be under extended warranty. We brought it to a Chevy dealer who kept from March 24 to April 9, without any resolution as they could not replicate the error which only happens under load travelling uphill. I also openedd a case with Chevrtolet Customer Service, who apparently does not have any ability to…
Mar 24, 2026Power train
This is a supplemental update to complaint #XXX filed February 7, 2026, regarding my 2020 Chevrolet Silverado 3500HD Diesel (VIN: [XXX] ). The vehicle experienced a sudden and complete loss of propulsion on January 21, 2026, consistent with the defect mechanism described in Recall 24V797. Recall software was installed May 27, 2025. Failure occurred eight months later with no warning. GM's response has been as follows: A Field Technical Service Engineer made a remote determination that the failure did not match the recall without physically inspecting the transmission. GM Executive Resolution required teardown at customer expense with no reimbursement guarantee. The authorized dealership…
Jan 21, 2026Power train
The vehicle experienced a sudden loss of propulsion while driving at highway speed after normal operation. The transmission began slipping and then would no longer engage gears. The vehicle had to be pulled over and towed. This vehicle is subject to GM Recall N242454440 related to a known transmission control valve defect that can cause loss of propulsion. I was not notified of this recall by GM and discovered it independently. Once aware, I completed the recall software update. After the failure, the dealer documented pressure control fault codes (P0746 and P0798), burnt transmission fluid, and internal debris, and recommended full transmission replacement. I requested that GM evaluate…
Jan 21, 2026Power train
While driving at highway speed in my 2020 Chevrolet Silverado 3500 Duramax, the transmission suddenly failed and locked up without warning. This caused an immediate loss of vehicle function and created a dangerous situation while traveling in traffic. I had my two children in the vehicle at the time. I was able to safely maneuver the truck to the shoulder, but the vehicle was no longer operable and required towing. This failure occurred only a few months after a transmission replacement and follows prior transmission repairs, including a valve body replacement performed by a GM dealership. This is a repeat transmission failure and presented a serious safety risk due to the sudden nature of…
Jan 30, 2026
Owner complaints are submitted to NHTSA by the public and are not verified. Shown as filed (NHTSA removes personal details); long reports are shortened.