GMC Sierra Complaints (2021)

671 consumer complaints on file.

#11746243June 24, 2026
ENGINE
My truck went into Reduced Power Mode while driving on the highway (Very Dangerous and life threatening) for a Coolant Control Valve Failure code (P1098), which has been confirmed by a GM dealership. GM already has extended the warranty for Special Coverage N252508341 for selective Vin numbers only and my Vin number is being excluded which isnt safe at all or fair. My truck is a 2021 Sierra Denali 3.0L lm2 duramax and has the same exact problem (coolant control valve failure code), and the same exact faulty part, and the same exact motor (LM2) which directly matches the perimeters for the N252508341 Special Coverage Program but my truck isnt being recalled or covered for repair due to them selectively choosing certain Vin numbers to recall only.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11745942June 23, 2026
ENGINE
While driving, the vehicle experienced a sudden and momentary loss of power, similar to briefly applying the brakes, after which power resumed. This was followed by a progressively louder squealing noise. I pulled over to investigate, at which point the engine shut off and a low oil pressure warning appeared on the dashboard. The vehicle would not restart. The vehicle was then towed to a dealership, where initial inspection suggested the issue may be related to the L87 recall involving the crankshaft bearing.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11745943June 23, 2026
POWER TRAIN
The contact owns a 2021 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the brake pedal was depressed, but the vehicle continued to move forward. There was no warning light illuminated. The vehicle was taken to the dealer and was diagnosed with transmission failure. The contact stated that the valve body and torque converter needed to be replaced. The dealer informed the contact that the transmission might need to be replaced. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 65,561. The VIN was unavailable.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11745952June 23, 2026
ENGINE
The AFM caused piston flapping and other major engine problems such as abnormal wear. The problem with the engine could have caused a catastrophic failure along the side of a highway. The problem has been diagnosed and the engine has been replaced at my expense. The repairs were made at a local mechanic shop. The engine would start make a loud ticking noise at 2000 RPM or above. The mechanic shop referred to this as piston flapping. This was caused by inadequate oil pressure at all cylinders due to the Active Fuel Management.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11745703June 22, 2026
ENGINE AND ENGINE COOLING
The contact owns a 2021 GMC Sierra. The contact stated that while driving at approximately 40-45, the engine warning light illuminated. There was an abnormal sound coming from the fan. The vehicle was taken to the local dealer, where it was diagnosed and determined that the coolant flow valve needed to be replaced. The vehicle was not included in a special coverage program. The vehicle was not repaired. The manufacturer was not contacted. The failure mileage was approximately 50,000.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11744992June 18, 2026
UNKNOWN OR OTHER
The problem is in the power-locking manual tailgate’s exterior release switch assembly. Water intrusion into the switch can cause a short circuit, leading the tailgate to unlatch while the truck is in Park. Once moving, momentum and air pressure can cause the tailgate to open further, potentially dumping cargo onto the road and creating a hazard.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11745145June 18, 2026
ENGINE
My vehicle began exhibiting symptoms consistent with a failed Engine Coolant Flow Control Valve. The check engine light illuminated, and diagnostic testing indicated a fault related to the coolant control valve system. In addition, I experienced abnormal cooling system operation, including the engine cooling fans continuing to run after the vehicle was shut off. Vehicle was tested few times in Auto Zone These symptoms affected the normal operation of the vehicle and are consistent with the condition described in Special Coverage N252508341. Based on the diagnostic findings and vehicle symptoms, I believe my vehicle qualifies for coverage under this program. I respectfully request that my vehicle be inspected and evaluated under Special Coverage N252508341 and that any eligible repairs be performed according to the terms of the coverage program.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11744736June 17, 2026
POWER TRAIN, ENGINE, FUEL/PROPULSION SYSTEM
While driving my vehicle, the engine and transmission lost power and the check engine light came on. The vehicle went into limp mode and engine propulsion was limited. Had I been traveling at a faster speed, this would have been very unsafe. After coming to a stop, placing the transmission in reverse did not move the vehicle and there was a grinding noise. I was able to savely move forward in limp mode, but the shifting was harsh. I was able to find an empty parking lot to safely park. The truck was towed to Jim Winter dealership in Jackson MI for inspection.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11744628June 16, 2026
POWER TRAIN, FUEL/PROPULSION SYSTEM, ELECTRICAL SYSTEM
So I made an appointment to have my truck recalled and the Wednesday before I took it, and it cranked no start and I called the dealership. Ask if they had any other those like this and they said that it could be the fuel injector module and so I got it to a mechanic shop to read the codes and it gave me a code p062b and I asked the dealership to look into it and they never figured out what we were not wrong. I just testing the battery. Well, then I got it back after the recall was done and new transmission valve body put in and about 30 miles down the road it started to shake violently and had a flashing engine light so I got it home called the dealership the next morning because they were closed set up another appointment got it to the dealership dealership said it had a couple misfires but since it wasn’t over 100 they weren’t concerned even though I’m pretty sure it is related to the fuel model going out because it has been cranking rapidly whenever I try to start it, but they won’t do anything to figure out what’s wrong?
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11744498June 16, 2026
ENGINE AND ENGINE COOLING
The contact owns a 2021 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the reduced power mode and Check Engine warning lights illuminated. The vehicle was taken to the dealer, where it was diagnosed with coolant control valve failure. The contact was informed that the coolant control valve needed to be replaced. The vehicle was not repaired. The contact was informed that the failure was like the failure description in Special Coverage Bulletin: N252508341. The manufacturer was made aware of the failure but provided no assistance. The contact was informed that the VIN was not associated with the Special Coverage. The failure mileage was approximately 58,500.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11744554June 16, 2026
POWER TRAIN
When pressing on the gas, especially when moderately accelerating, the truck experiences severe shaking, which interferes with acceleration, as well as causing the truck to "jump" when the transmission gear "catches", even while driving. When the truck is at a full stop and the engine is auto off, when it restarts, it does so frequently when it reengages that it causes a physical "jump" in the vehicle, causing the driver's foot to come off the brake pedal. This has been most noticeable since my vehicle hit about 70k miles. I currently have 84k miles. I engaged the dealer and was told the transmission is out of warranty. I see that other GMC Sierra models suffer similar problems and recalls have been issued to GMC that they must repair those vehicles. Despite that, my vehicle is not included in any current recall program.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11744321June 15, 2026
ENGINE
Engine Coolant Control Valve Position Sensor Minimum Stop Performance, and Chevy recalled this on this same motor and GMC needs to pays for this as it’s a major problem!
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11743882June 13, 2026
ENGINE, EXTERIOR LIGHTING, POWER TRAIN
While coasting down or under very light acceleration between 12-20 mph the vehicle has a shudder like driving over a highway rumble strip. While cruising on the highway at 65+ mph, the vehicle has a light shudder or vibration. Vehicle has been checked numerous times for wheel and tire inconsistencies. Brake pads and rotors have also been replaced with no change in issue. Headlights daytime running light changes color from bright white to purple during warm weather. The vehicle has been to 3 different GM dealerships and they acknowledge the issues but do not provide a resolve.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11743698June 12, 2026
SERVICE BRAKES
The contact filed the complaint on behalf of the owner of a 2021 GMC Sierra 3500. The contact stated that while the vehicle owner was driving at an undisclosed speed, the driver noticed that the rear wheels were attempting to lockup. The contact stated that the failure was noticeable while driving forward and while reversing. No warning light illuminated. The vehicle was taken to the independent mechanic, where it was diagnosed with detached rear brake pads and detached rear emergency brake shoes. In addition, the rear brake caliber had seized. The vehicle owner was informed that the rear brake pads and the rear emergency brake shoes needed to be replaced, and the rear brake caliber needed to be repaired. The vehicle was repaired. The dealer was made aware of the failure. The contact was advised to contact the NHTSA Hotline to report the failure. The manufacturer was not made aware of the failure. The failure mileage was approximately 140,606.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11742782June 8, 2026
ENGINE
While driving home, the engine began to run very rough with decreased acceleration, obvious overall loss of power and a significant amount of white smoke being emitted from exhausts. Several alarm indicators and codes started flashing on instrument panel including Check Engine, Service ESC, Steering Assist Reduced, and Service Parking Brake. Had truck towed to dealership. From Dealership Repair Invoice: Truck scanned with diagnostic codes 0300, 0302 present. Dealership removed right side valve cover and found rocker does not move when engine running. They removed the right side head and found cam and lifter damage. Camshaft, and all 16 lifters were replaced as per document 5659832 under warranty. Labor was 23.3 hours plus 1.2 hours to recover and recharge A/C system.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11741852June 3, 2026
ENGINE AND ENGINE COOLING
The contact owns a 2021 GMC Sierra 1500. The contact stated that while The vehicle while operating the vehicle a knocking noise was present coming from the engine and the check engine warning light had remained illuminated. The vehicle was examined by an independent mechanic who diagnosed that the engine valves had malfunctioned and engine needed to be repaired. The vehicle was not yet repaired. The manufacturer was notified of the failure but no assistance was offered. The manufacturer was notified of the failure. The contact was informed that the VIN was not included in the NHTSA Campaign Number: 25V274000(ENGINE AND ENGINE COOLING). The contact indicated that the vehicle had experienced that same failure listed in the recall. The failure mileage was 98,000.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11741938June 3, 2026
UNKNOWN OR OTHER
Vehicle will not consistently shut off. Shift to park error received upon trying to shut vehicle off. Concerns on if the vehicle is actually in park and if it is safe to exit vehicle. Concern that vehicle is not in park and electrical units aren’t being properly shut down (i.e. radio).
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11741189June 1, 2026
STEERING, ELECTRICAL SYSTEM, POWER TRAIN
power steering locked up while driving. multiple dash lights turned on, on its own after the issue, 4wd, emergency brake, abs, and other ones im not sure what they are. took it to the dealership for a recall and told them the issue that happened.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11741190June 1, 2026
STEERING, POWER TRAIN, ELECTRICAL SYSTEM
power steering locked up while driving. has been inspected and repaired by manufacturer. recall.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11741277June 1, 2026
ENGINE
Catastrophic engine failure the connecting rod went through the block. It is my understanding that Defective Components: Manufacturing defects in the connecting rods and crankshafts can reduce oil film strength, leading to severe wear, metal debris, and catastrophic engine could be the proiblem
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0

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