GMC Sierra Complaints (2021)

671 consumer complaints on file.

#11774349October 29, 2026
ENGINE, UNKNOWN OR OTHER
I have repeatedly experienced a noticeable exhaust odor inside the cab while operating the vehicle\. The condition is particularly pronounced during cold weather when the vehicle is idling\. Under these circumstances, the exhaust smell inside the passenger compartment is distinct and concerning\. I have taken the vehicle to two separate General Motors dealerships in an effort to identify and resolve this issue\. On both occasions, I was advised that the vehicle was fine\. Despite these visits, the problem remains unresolved, and I continue to experience exhaust fumes inside the cab under the conditions described above\. My concern is that exhaust gases may be entering the passenger compartment, potentially exposing the driver and passengers to harmful emissions, including carbon monoxide\. Because carbon monoxide cannot be detected by smell, the presence of an exhaust odor does not establish whether carbon monoxide is present or at what concentration\. However, the recurring odor warrants a thorough investigation to determine its source and whether a potentially hazardous condition exists\. I am concerned that the issue may not be adequately identified during routine dealership inspections if the vehicle is not evaluated under the specific conditions in which the symptoms occur\. The fact that two dealerships have indicated that the vehicle is operating normally does not resolve my concern, particularly because the symptoms continue to occur\. I am requesting that the National Highway Traffic Safety Administration review this complaint and determine whether further investigation is warranted into the possibility of exhaust gases entering the passenger compartment of this vehicle\. I would appreciate consideration of whether this condition could represent a safety\-related defect that may affect other vehicles of the same make, model, or model year\. I have made reasonable efforts to address this matter through authorized GM service facilities.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11774225October 28, 2026
UNKNOWN OR OTHER
2021 GMC 3.0 Diesel have coolant control valve issues. GM has a special coverage for them under Special Coverage N252508341. That coverage covers my year make and model. I have an open case with GM under GMC Customer Assistance opened case 116070735. GM is refusing to cover it due to this cited email. "After reviewing the vehicle information, we determined that Special Coverage N252508341 does not apply because it is not associated with the vehicle identification number (VIN) on your vehicle." I had the dealership and GMC customer service confirm this. GMC told me to request goodwill assistance at the dealership which the service provider had never heard of before. I can provide all documentation needed. I had recurring P1098, followed by a reduced engine power warning and unusually loud radiator fans. I figured it may be the coolant control valve and found Special Coverage N252508341. I created an open case with GM and took it to the dealership. The dealership was ambiguous about the issue and quoted me over 2,000 dollars just for further diagnostics citing "Coolant" and "Valve" in the documentation. They also said once they find the issue it would be "more." I took it to a 3rd party mechanic for an actual understanding of the issue. The mechanic found that the issue was the coolant control valve, which I have in documentation, and recommend a clear understanding of the repair and quote for the repair.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11774276October 28, 2026
POWER TRAIN
I am experiencing hard gear shifting in the low gears. It is very noticeable and I have a 10-speed transmission.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11772830October 21, 2026
ENGINE
Engine locked up while driving down the road at highway speeds. Lost all power and had to pull to shoulder of road. Was towed to dealership and confirmed engine locked up and covered under special recall. Was looked at a few months back and passed the recall test on engine. No lights or signs of engine failure before failure.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11772486October 20, 2026
POWER TRAIN
The contact owns a 2021 GMC Sierra 1500. The contact stated that while driving at 55 MPH, the accelerator pedal was depressed; however, the vehicle failed to accelerate as intended. The contact became aware of an abnormal sound, and the check engine warning light was illuminated. The vehicle was driven to the shoulder of the road. The contact inspected the vehicle and connected a portable diagnostic tester to the vehicle. The contact retrieved a pressure fault code. The vehicle was taken to the dealer, where it was diagnosed with a torque converter shudder. Additionally, the solenoids were clogged with debris. The contact was informed that the transmission needed to be replaced. The manufacturer was contacted, and a case was filed. The failure mileage was approximately 106,554.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11772316October 20, 2026
ENGINE, FUEL/PROPULSION SYSTEM, POWER TRAIN
My 2021 GMC 1500 Sierra has the 6.2L motor that has significant known issues with catastrophic engine failure involving the camshaft and lifters. The engine in my truck has suffered the same failure but for some reason my VIN is not included in the recall of nearly 600,000 GMC trucks. I called GMC Customer Service and was told bluntly the recall was VIN specific and I would have to bear the 14,000 dollar repair. This is unacceptable since GMC is under federal investigation for knowingly and negligently manufacturing a flawed motor.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11772072October 19, 2026
ENGINE
My vehicle fits Special Coverage N252508341in every way, except the dealership tells me that my VIN is not covered. I drive a 2021 GMC Sierra 1500 with approximately 61,000 miles. This weekend a Check Engine Light illuminated with P1010 code. All the symptoms described in Special Coverage N252508341 were exhibited: the vehicle displayed 'Engine Power Reduced', and the electric cooling fans began operating at full output. I have taken the vehicle to Cronin GMC here in Perrysburg and it has been diagnosed with Coolant Control Valve failure that requires replacement. They state that my VIN is not covered by Special Coverage N252508341 and that I must pay full price for the replacement. I am writing to extend this coverage to my vehicle so I can either receive a no-charge repair or seek reimbursement after I pay for the service.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11771890October 18, 2026
ENGINE, SERVICE BRAKES
Service light came on because the brake petal would push back when I tried to start it. At times, I had to push down all the way almost to the floor and then it would start. If I eased up slightly or did not push all the way, the truck would hesitate to start. I brought it in to Courtesy GMC of [XXX]. They found metal debris in oil. The car warranty did not want to replace the entire engine as General Motors' bulletin had stated as a corrective solution. They only wanted to replace the camshaft and rocker arms because [XXX] did not tear down the engine to the point of failure. [XXX] stated that they did. After going back and forth with EasyCare (myself and [XXX]) I authorized the repairs EasyCare suggested. XXX, a Service Brake Assist message came on. I brought it to [XXX]. They rectified the issue. XXX,Truck stalled getting off XXX at light. Truck kept turning on and off. I put it in park and was able to turn in on. As I was driving the truck was rocking back and forth as I pressed the gas pedal. I was able to pull into the Super1 Foods parking lot. Trucked stalled halfway into parking lot. After two attempts to turn off and start truck I was able to pull it up all the way to ensure safety. Texted [XXX] at Courtesy. I called the number he sent and a tow truck from Cliff’s Towing and Recovery, LLC retrieved my truck and brought it to Courtesy GMC in [XXX] where it is currently residing. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11771969October 18, 2026
FUEL/PROPULSION SYSTEM
The vehicle failed to start. It started after 30 minutes and I was able to drive it home. Then it starts and stalls after multiple attempts. Receiving codes P1177 and UI8A2. Was told that a bulletin exists for this issue on GM vehicles, GM Bulletin 24-NA-139, but I found out that it don't cover my VIN number. This can cause the vehicle to stall or shut off while driving. GM should make this bulletin for all vehicles of certain years who carry this modules.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11771771October 17, 2026
ELECTRICAL SYSTEM, UNKNOWN OR OTHER
The infotainment system inadvertently shuts down and restarts which creates a unsafe situations while using the navigation system, backing up using the backup camera and while trailering. In a 30 mile drive it might do it 10 times and it might do it 30 times and eventually it doesnt restart until the vehicle is shut off. Each time it does it, it starts with the screen locking up which has resulted in me backing into my boat trailer 3 times while backing up to put the trailer on the hitch and numerous near misses with pedestrians and other vehicles in parking lots. Research on the internet indicates it is a known issue across several GMC platforms and has been since 2016. I took my truck to the dealer, they did a software update which was unsuccessful, then they did a global reset, charged me $240.00 and told me it was fixed. It shutdown 2 times before I got out of their parking lot.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11771806October 17, 2026
ENGINE
Loud engine knock, made it to dealer. Dealer confirmed engine failure as defined in the applicable recall. No idea when a replacement can be aquired. Unable to drive anywhere due to design and manufacturinf issues I did not cause.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11771467October 15, 2026
ENGINE
The contact owns a 2021 GMC Sierra. The contact stated that while driving at 60 MPH, a reduced power mode warning message unexpectedly illuminated, and the vehicle unexpectedly entered limp mode. The contact stated that the temperature gauge indicated a high temperature and the vehicle was overheating during the failure. The vehicle was taken to the dealer, where it was diagnosed that the control valve had failed and needed to be replaced. The vehicle was not repaired. The dealer informed the contact that this was a known failure and escalated the issue to the manufacturer for further assistance. The contact stated that the failure was associated with Technical Service Bulletin (TSB) N252508340 and believed the repair should have been covered under warranty. The manufacturer was made aware of the failure via telephone and website. The contact was also referred to NHTSA for further assistance. The approximate failure mileage was 110,900.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11771106October 14, 2026
ENGINE, FUEL/PROPULSION SYSTEM, UNKNOWN OR OTHER
1. What component or system failed or malfunctioned, and is it available for inspection upon request? The failure involves the NOx emissions control system, specifically NOx Sensor #2 and the associated NOx catalyst/DPF assembly. Diagnostic trouble codes P11D5, P14D4, P22A1, P2832, P2833, and P28AF confirm abnormal NOx readings caused by sensor breakdown and catalyst performance degradation. Yes, the components are available for inspection at the servicing GM dealership. 2. How was your safety or the safety of others put at risk? A malfunctioning NOx sensor and catalyst can cause the vehicle to enter reduced‑power or limp‑mode operation, which may limit acceleration or speed unexpectedly. This can create hazardous situations during highway merging, passing, towing, or maintaining speed in traffic. Additionally, improper emissions control can lead to engine performance irregularities that may affect vehicle responsiveness. 3. Has the problem been reproduced or confirmed by a dealer or independent service center? Yes. The issue has been confirmed by a GM dealership through diagnostic testing. The dealer verified all fault codes and confirmed the NOx sensor failure and abnormal catalyst readings. 4. Has the vehicle or component been inspected by the manufacturer, police, insurance representatives, or others? The vehicle has been inspected by GM‑certified dealership technicians. No inspections have been performed by police, insurance representatives, or other third parties. 5. Were there any warning lamps, messages, or other symptoms of the problem prior to the failure, and when did they first appear? Yes. The check engine light and emissions‑related warnings appeared around 80,000 miles, coinciding with the emissions warranty limit. Diagnostic trouble codes related to the NOx system were present, and the vehicle exhibited abnormal emissions readings consistent with sensor and catalyst malfunction.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11770868October 13, 2026
ENGINE, FUEL/PROPULSION SYSTEM, POWER TRAIN
2021 GMC with 6.2L motor. The engine begin to produce a clattering noise in the upper part of the engine. When the clattering happens the vehicle will shudder. I took the vehicle into a certified independent service center who diagnosed a catastrophic engine failure as a result of lifter and camshaft bearing failure. They further advised that this year of vehicle (2021) and engine (6.2L) was known to have this defect and might be subject to a safety recall. I contacted GM customer service who stated that my VIN was not included in the recall even though the year and engine matched the recall. I found that to be odd especially when I noted that nearly 600K vehicles matching my failed engine was recalled. She stated that I (owner) had to bear the cost of replacing the defective engine and labor. I had to have my vehicle transported from [XXX] to [XXX] at the cost of 1400 dollars. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11770585October 12, 2026
ENGINE
Vehicle is a 2021 GMC Sierra with 3.0 Diesel. Coolant control valve is bad. Vehicle has 108,000 miles. GM issued Bulletin N252508341 extending the warranty to 15 years or 150,000 miles for 2021-2022 GMC Sierra. Now they are saying my VIN # is not effected and they will not cover the replacement which costs about $2100. After researching this I'm finding many VINs are not covered and there are many trucks with failed parts that are not covered. GM should extend this to all VINs under those years. Its an obvious problem but their bulletin does not cover all the vehicles affected. They make it look like they are trying to make it right but in reality, its misleading.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11770706October 12, 2026
ENGINE
While towing a trailer on 6/26/26, the 6.2L L87 engine suffered a sudden drop in oil pressure, began knocking, and completely lost motive power on the roadway. Because the engine seized instantly, the vehicle experienced a sudden loss of power steering and power braking while managing the extreme weight of a trailer. This combination created a severe and immediate safety hazard, forcing me to maneuver a heavy, unpowered truck and trailer combination through active traffic to the shoulder without full steering or brake control, putting my life, my passengers' lives, and the safety of surrounding motorists at extreme risk. My dad read the codes before we took it to my mechanics and the only code I can remember is P0016. I took it and dropped it off at my local mechanics on 6/28/26. This is what my mechanic said: No Start-Truck came in not running. Had timing codes. I believe the crank bearing failed causing the engine to lose oil pressure. With the sudden loss of oil pressure, the timing chain tensioner slacked and caused the cam/crank to go out of time. Drained engine oil and found bearing material. We also cut oil filter open and found more bearing material. The timing cover was removed and verified the cam timing was off. In conclusion the engine has failed and will need full replacement. This is the exact failure mechanism under active NHTSA Investigation EA26005.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11770097October 9, 2026
ENGINE
Was just driving along and the car just died
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11769533October 7, 2026
ENGINE
Truck was in motion and the engine light started blinking then stopped. A couple miles down the road the truck jilted and the engine light came on again. The Service ESC and emergency parking brake light came on. The truck started shaking. We pulled over and parked. Turn off the truck and when we turned it back on it started shaking. When we drove we started hearing popping, knocking, loss in power of the vehicle. This could’ve caused serious damage to ourselves or other drivers if we could’ve have stopped. Vehicle is being inspected. Multiple same vehicles have had the same issues in my town. At least 5 that we know of. At one point all of the lights came on and now there is just a few lights. More than what I listed earlier.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11769653October 7, 2026
ENGINE
The contact owns a 2021 GMC Sierra 1500. The contact stated that while driving and towing a 5,000-pound load, the vehicle made an abnormally loud sputtering sound at 3,000 RPM. The contact stated that the failure was more noticeable while towing a load. The vehicle was taken to an independent mechanic, where an audible diagnostic test was performed and the contact was informed that the sound was related to the engine bearings. The vehicle was then taken to the dealer, where it was diagnosed with fifty-two engine misfires. The contact was informed that the misfires should have caused the check engine warning light to illuminate; however, the light was not illuminated. The dealer replaced the ignition coils and spark plugs; however, the failure recurred while driving. The manufacturer was notified of the failure. The failure mileage was approximately 110,000.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11769438October 6, 2026
ENGINE
Lifter collapsed at 31970 miles. It was fixed at GMC dealership. It just happened out of no where. No warning signs.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0

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