2021 GMC Sierra 2500HD

What owners should know

Covers 2020–2026 · 6.6L Duramax L5P diesel and 6.6L V8 gas · Updated 2026-10-01

Researched from owner forums and NHTSA complaints and written by Know Your Truck. These are patterns in what owners report, not a guarantee about any particular truck.

Common failures & how to fix them

Parts and video buttons search for your 2021 GMC Sierra 2500HD. Always confirm a part fits using your VIN. Brakes, steering, fuel and airbag work affects your safety, so if you're not sure, have a qualified mechanic do it.

• 10-speed transmission valve body failure

  Dealer (recall)

  Signs: Sudden hard downshifts, limp mode, or rear wheel lock-up on diesels.

  Fix: Covered by GM recalls on 2020–2022 diesels. Other repairs are usually under warranty on newer trucks. Ask a dealer for all open recalls and bulletins.

  May be covered free by recall 24V797000 / 26V083000. Check the VIN at nhtsa.gov/recalls.

• Trailer brake controller warnings

  Easy DIY

  Signs: 'Check trailer wiring' or 'Trailer brakes disconnected' messages that cut the trailer brakes.

  Fix: Clean and inspect the 7-pin trailer connector and the trailer's wiring first. If it continues, have a dealer check for bulletins and module updates.

  Shop: 7 pin trailer connector▶ How-to videos

• Power tailgate opens unexpectedly

  Dealer (recall)

  Signs: The tailgate unlatches by itself, often after water gets in.

  Fix: Covered by GM recalls on 2020–2024 trucks with power-unlatching tailgates.

  May be covered free by recall 24V060000 / 24V894000. Check the VIN at nhtsa.gov/recalls.

• Steering gear shaft can break (2024)

  Dealer (recall)

  Signs: Loose steering or a clunk. In rare cases loss of steering.

  Fix: Covered by a GM recall on some 2024 trucks.

  May be covered free by recall 23V549000. Check the VIN at nhtsa.gov/recalls.

Recalls

A recall doesn't mean a truck still has the problem. Enter the truck's VIN at nhtsa.gov/recalls or ask a dealer to see whether the repair was done.

• Power Train:Automatic Transmission:Control Module:Software

  Oct 2024 · #24V797000

  General Motors, LLC (GM) is recalling certain 2020-2022 Chevrolet Silverado 1500, 2500, 3500, GMC Sierra 1500, 2500, 3500, 2021 Cadillac Escalade, Escalade ESV, Chevrolet Tahoe, Suburban, GMC Yukon, and Yukon XL vehicles equipped with diesel engines. The transmission control valve may fail and cause the rear wheels to lock-up.

  Risk and fix

  Risk: Rear wheel lock-up can increase the risk of a crash.

  Fix: Dealers will install new transmission control module software, free of charge. GM will provide a special coverage program to cover the repair of transmissions that are identified by the remedy software as containing a defective control valve. Owner notification letters were mailed December 12, 2024. Owners may contact GM customer service at 1-888-988-7267, Cadillac customer service at 1-800-458-8006, GMC customer service at GMC 1-800-462-8782 or Chevrolet customer service at 1-800-222-1020. GM's number for this recall is N242454440.

• Latches/Locks/Linkages:Tailgate:Latch

  Feb 2024 · #24V060000

  General Motors, LLC (GM) is recalling certain 2020-2024 Chevrolet Silverado 2500, 3500, GMC Sierra 2500 and 3500 vehicles equipped with power-unlatching tailgates. The tailgate's electronic gate-release switch may short circuit due to water intrusion, which can result in the tailgate inadvertently unlatching while the vehicle is in park.

  Risk and fix

  Risk: An unlatched tailgate may open while driving and result in a loss of unsecured cargo, creating a road hazard and increasing the risk of a crash.

  Fix: Owners are advised to check that the tailgate is closed and latched before driving. Dealers will replace the exterior touchpad switch assemblies, free of charge. Owner notification letters were mailed May 17, 2024. Owners may contact Chevrolet customer service at 1-800-222-1020 or GMC customer service at 1-800-462-8782. GM's number for this recall is N232426400.

• Service Brakes, Hydraulic:Power Assist:Electric:Control Module

  Sep 2021 · #21V758000

  NHTSA warning: park outside and away from buildings until fixed.

  General Motors, LLC (GM) is recalling certain 2021-2022 Chevrolet Silverado 2500, Silverado 3500, GMC Sierra 2500, and Sierra 3500 vehicles with electronic brake control modules (EBCM) replaced during vehicle assembly. The bolts that attach the brake pressure modulator valve (BPMV) assembly may not be properly tightened, which could fail to seal the two sub-assemblies and allow water intrusion.

  Risk and fix

  Risk: Water in the BPMV may cause an electrical short circuit and increase the risk of fire.

  Fix: Owners are advised to park outside and away from other structures until the recall repair is completed. Dealers will replace the BPMV assembly, free of charge. Owner notification letters were mailed on October 20, 2021. Owners may contact Chevrolet customer service at 1-800-222-1020 or GMC customer service at 1-800-462-8782. GM's number for this recall is N212349181.

• Tires:Temporary/Emergency Spare Tire

  Jul 2021 · #21V578000

  General Motors, LLC. (GM) is recalling certain 2020-2021 Chevrolet Silverado 2500 and GMC Sierra 2500 vehicles equipped with a 17" spare tire (RPO ZHQ or ZXT) and either the 20" accessory road tire (RPO REM) or the 18" accessory road tire (RPO Q2V). Operating the spare tire with other 20" or 18" tires can prevent the Anti-Lock Braking System (ABS) from engaging.

  Risk and fix

  Risk: An ABS system that cannot control the rear wheels independently increases the risk of a crash.

  Fix: Dealers will provide the appropriate spare tire and apply a new spare tire information label, free of charge. Owner notification letters were mailed on October 18, 2021. Owners may contact Chevrolet customer service at 1-800-222-1020; GMC customer service at 1-800-462-8782. GM's number for this recall is N212329780.

• Seat Belts

  Dec 2020 · #20V811000

  General Motors, LLC (GM) is recalling certain 2020 Chevrolet Bolt EV and 2021 GMC Canyon and Sierra 1500, 2500 and 3500, Yukon, Yukon XL, Cadillac Escalade and Escalade ESV and Chevrolet Blazer, Camaro, Colorado, Equinox, Silverado 1500, 2500 and 3500, Suburban and Tahoe vehicles. Incorrect bolts may have been used at one or more fastening locations to secure the seat belts to the vehicle. If an incorrect bolt was used, the seat belt may not be properly attached to the vehicle.

  Risk and fix

  Risk: If a seat belt assembly is not properly attached to the vehicle, the seat belt may not properly restrain an occupant in the event of a crash, increasing the risk of injury.

  Fix: GM will notify owners, and dealers will replace the suspect bolts, free of charge. The recall began January 29, 2021. Owners may contact GMC customer service at 1-800-462-8785, Cadillac customer service at 1-800-458-8006, or Chevrolet customer service at 1-800-222-1020. GM's number for this recall is N202322230.

• Seat Belts

  Dec 2020 · #20V792000

  General Motors, LLC (GM) is recalling certain 2019-2021 Chevrolet Silverado 1500 and GMC Sierra 1500, 2021 Chevrolet Suburban and Tahoe and GMC Yukon XL and 2020-2021 Chevrolet Silverado 2500 and 3500 and GMC Sierra 2500 and 3500 vehicles. The seat belt brackets may not be secured to the seat frame in the front-row center seating position.

  Risk and fix

  Risk: If a seat-belt bracket is not secured, the seat belt may not properly restrain an occupant in the front-row center seat position, increasing the risk of injury in a crash.

  Fix: GM will notify owners, and dealers will inspect left-side and right-side front-row center seat-belt bracket attachments and reassemble it correctly as necessary, free of charge. The recall began January 26, 2021. Owners may contact GMC customer service at 1-800-462-8782, Chevrolet customer service at 1-800-222-1020. GM's number for this recall is N202314670.

Owner complaints by area

Reports owners filed with NHTSA. They aren't verified, and one complaint can mention more than one area. Tap an area to read the most recent ones.

• Power Train12

  1 involved a crash

  • Filed Jun 2026

    I am reporting repeated failures involving both the transmission and diesel emissions (DEF) system on my 2021 GMC Sierra 2500HD Denali equipped with the 6.6L Duramax diesel engine and Allison 10-speed automatic transmission. While under warranty, the truck required replacement of the aftertreatment fuel injector and later the Reductant Control Module due to DEF/emissions system failures. General Motors also completed recall-related transmission software updates on the vehicle. At approximately 154,833 miles, the transmission began shifting improperly, set transmission fault codes, and required complete replacement at my expense. Less than 5,000 miles later, the vehicle again experienced a "Service DEF System" warning with multiple diagnostic trouble codes. Repairs required replacement of the DEF tank, DEF heater assembly, and NOx sensor. These repeated failures involve major drivetrain and emissions components on a heavy-duty truck. DEF system failures can place the vehicle into reduced-power (derate) mode, limiting vehicle performance and creating potential safety concerns while driving or towing. I am submitting this complaint so these failures can be documented as part of NHTSA's evaluation of similar vehicles.

  • Filed Jun 2026

    We keep getting an error message that shows we need to service DEF SYSTEM, it also started to limit my MPH and is now locked at 55 MPH. initial check of the DEF SYSTEM shows a malfunctioning module. it has been happening over the last year to 18 months. they would reset it or it would sometimes go away on its own after having to drive it in order for the error to clear.

  • Filed Mar 2026

    While driving on the highway at normal speed, my vehicle was operating completely normally with no warning lights, messages, or prior issues. Without any warning, the vehicle suddenly lost the ability to accelerate and felt as if it had been shifted into neutral. I immediately had to pull over to the side of the highway, as this created a dangerous situation with surrounding traffic. The vehicle had to be towed to a mechanic. Upon inspection, I was informed that a coolant line connected to the transmission had completely blew off, causing a rapid loss of transmission fluid and resulting in total transmission failure. I was told this was not due to a rusted or deteriorated clamp, but rather a sudden component failure. This vehicle has been meticulously maintained and I have owned it for less than one year. There were no prior symptoms, leaks, or warning signs leading up to this incident. This appears to be a sudden and unexpected mechanical failure, not caused by neglect or misuse. The loss of power while driving at highway speed posed a serious safety risk to myself and others on the road.

  • Filed Dec 2025

    Pulling into a driveway and the truck made a loud clunk and the check engine light, traction control light, and a reduced engine power light came on and the truck came to an abrupt stop. When the gear shift was put into reverse or any forward gear the truck would rev up without touching the gas pedal. The left rear wheel locked up. After paying over $700 in tow bills to get the truck towed to our house and then to the dealer we were told that the transmission had a catastrophic internal failure. This truck only has 82,000 miles on it and is a 2021!

  • Filed Oct 2025

    The contact owns a 2021 GMC Sierra 2500. The contact stated that while driving at 50 MPH, the contact was pulling a trailer that he had loaded, and he drove around a curve, the gear shifted down independently, and the trailer pushed the vehicle off the right side, causing him to crash into a post and embankment. The contact mentioned he was able to shift the gear into Four Wheel Drive to get back on the road. The contact mentioned he pulled over to the right side of the road, exited the vehicle to inspect, and noticed damage to the vehicle and the trailer. The contact stated no air bag deployed. The contact stated that he sustained injuries left arm and neck, causing his muscles to tighten. No medical attention was required. The contact stated no police report was filed. The contact mentioned that the vehicle was previously repaired for a manufacturer's recall with the transmission, but failed to prevent the failure. The contact was relating the failure to NHTSA Campaign Number: 24V797000 (POWER TRAIN). The vehicle was serviced by the dealer, but the remedy failed to repair the vehicle. The contact stated that the failure was not diagnosed by a dealer or independent mechanic. The manufacturer was not notified of the failure. The approximate failure mileage was 78,000.

  • Showing the 5 most recent of 12.
• Exterior Lighting9

  • Filed Jan 2026

    My right headlamp/ turn signal assembly began flashing at random intervals. The high beam would come on and off randomly. The entire assembly would randomly flash along with the turn signal. The headlamp would go on and off randomly. This included switching between setting. High beam, low beam, daytime running light, and completely off with no warning. This causes blinding conditions for oncoming drivers, loss of visibility for driver, and loss of visibility during inclement weather due to high beam coming on and off, then entire unit turning off. As of right now, the vehicle is undrivable due to incorrect lighting, and flashing lights.

  • Filed Feb 2025

    Known issue and has been attributed to a manufacturing defct, but no recall- Leaking headlight caused damage to headlight- now turn signal and headlight do not work. Entire assembly needs to be replaced, GM / Extended Warranty Company will not cover, this safety part. Head light and turn signal were working on the way to the dealer, 1 month later when we picked it up - Right turn signal malfuction reading appeared on dash, headlight blinking and will not work. Picked up on Friday 1/30/25, and made an appointment for the following Wednesday to take it back in. Was told by dealer today that the replacement will not be covered and will cost $2100.00 to replace. This is a safety part and the truck can not be driven legally or safely without both headlights working.

  • Filed Feb 2025

    Headlight vent failed. Hid control board filled up with moisture. Headlight is flashing like emergency vehicle if it turns on at all.

  • Filed Jan 2025

    The front left headlamp assembly low beam light unexpectedly began to flicker repetitively until the vehicle was turned off. In addition, the left front turn signal was failed, but an indication of the failed turn signal was not always present. The headlamp assembly was taken in for replacement at a local GMC dealership promptly due to safety concerns of operating the vehicle on public roadways with this condition. The safety of others was at risk due to the strobing effect of the flickering lights and not being able to drive the vehicle during conditions where headlights are necessary. The flickering/strobing condition of the headlamp was highly distractive and puts other drivers are risk. In addition, due to the natural height of the vehicle the cast of the beam is closer to the rear view mirror height of the majority of vehicles. The problem was confirmed by a local GMC dealership and was identified as a faulty headlamp assembly. The vehicle was not inspected by any other party besides the dealer who performed the diagnosis and repair. There were no symptoms of warning messages prior to the failure.

  • Filed Jan 2025

    Headlights and turn signals failed. Flickering of various lights (Daytime running lamp, low beam, high beam, turn signals) followed by total failure. 3700 dollar repair at dealer to replace both headlamp assemblies. Barely over miles of warranty, but still in the 3 year warranty time period. Not having forward lighting is of course a major safety issue. Vehicle should be recalled. Many others are having the issue.

  • Showing the 5 most recent of 9.
• Engine8

  • Filed Jun 2026

    I am reporting repeated failures involving both the transmission and diesel emissions (DEF) system on my 2021 GMC Sierra 2500HD Denali equipped with the 6.6L Duramax diesel engine and Allison 10-speed automatic transmission. While under warranty, the truck required replacement of the aftertreatment fuel injector and later the Reductant Control Module due to DEF/emissions system failures. General Motors also completed recall-related transmission software updates on the vehicle. At approximately 154,833 miles, the transmission began shifting improperly, set transmission fault codes, and required complete replacement at my expense. Less than 5,000 miles later, the vehicle again experienced a "Service DEF System" warning with multiple diagnostic trouble codes. Repairs required replacement of the DEF tank, DEF heater assembly, and NOx sensor. These repeated failures involve major drivetrain and emissions components on a heavy-duty truck. DEF system failures can place the vehicle into reduced-power (derate) mode, limiting vehicle performance and creating potential safety concerns while driving or towing. I am submitting this complaint so these failures can be documented as part of NHTSA's evaluation of similar vehicles.

  • Filed Apr 2026

    The contact owns a 2021 GMC Sierra 2500. The contact stated that while driving at 55 MPH, the vehicle stalled unexpectedly. There were no warning lights illuminated. The vehicle was taken to the local dealer, where it was diagnosed, and determined that the engine needed to be replaced. The engine was replaced; however, the failure recurred. While at a stop and attempting to drive around a curve, the vehicle stalled. No warning lights were illuminated. The vehicle was taken to the local dealer, where it was diagnosed with engine failure. The vehicle was not repaired. The failure mileage was approximately 77,000. The VIN was not available.

  • Filed Feb 2026

    80,000 Miles, complete engine break down. 12,000 to repair

  • Filed Dec 2024

    The contact owns a 2021 GMC Sierra 2500. The contact stated while driving 40-55 MPH, the vehicle started losing motive power. The contact stated while pulling into a nearby independent mechanic shop, the vehicle started jerking significantly and stalled midway. The check engine warning light was illuminated. The mechanic diagnosed the vehicle with transmission failure. The vehicle was towed to the residence. The local dealer and several unknown dealers were notified of the failure and informed the contact that the transmission assembly was not available and could not be ordered. The vehicle was towed to CJ's Transmission, where the transmission was taken apart. The mechanic determined that the transmission needed to be replaced. The vehicle was being repaired with a rebuilt transmission. The contact received notification of NHTSA Campaign Number: 24V797000 (Power Train); however, the part to do the recall repair was not yet available. The local dealer was contacted. The contact stated that the manufacturer had exceeded a reasonable amount of time for the recall repair. The manufacturer was made aware of the failure and offered a modest monetary compensation for the repair. The failure mileage was approximately 134,000. Parts distribution disconnect.

  • Filed Aug 2024

    Smog system check and Engan warning light keeps come on.

  • Showing the 5 most recent of 8.
• Service Brakes6

  • Filed Aug 2026

    The left rear internal "top-hat" parking brake shoes suffered a total manufacturing bonding failure, causing the friction lining to completely delaminate and detach from the metal backing plates inside the rotor hub. This triggered Diagnostic Trouble Code (DTC) C060B (Left Park Brake Actuator Circuit). The failed components were replaced by the servicing facility and are unavailable, but the official dealer diagnostic scan sheet and itemized repair invoice are preserved and available for inspection upon request. Safety was compromised in two ways. First, the mechanical failure completely disabled the electronic parking brake system, forcing a heavy-duty truck to rely exclusively on the transmission's parking pawl to remain stationary. This creates a severe rolling vehicle hazard, especially on inclines or when hauling/towing heavy loads. Second, when these shoes disintegrate, the loose friction debris trapped inside the enclosed drum can shift, wedge, and cause a sudden mechanical wheel lockup or severe brake dragging at highway speeds, threatening vehicle control. The problem was officially confirmed and diagnosed by an authorized General Motors dealership service center. The technician scanned the vehicle, retrieved DTC code C060B, and confirmed upon inspection that the internal parking brake shoes had completely disintegrated. There were absolutely no physical symptoms, abnormal noises, dragging sensations, or brake pedal changes prior to the failure, as the parking brake shoes sit isolated inside the rotor hub. The issue appeared suddenly on May 23, 2026, when the vehicle immediately displayed a parking brake malfunction warning lamp on the instrument cluster dashboard and completely refused to engage the electronic parking brake.

  • Filed Oct 2025

    2021 GMC Sierra 2500HD 6.6L gas 6 speed automatic transmission W/4wd After a brake service job the vehicle will randomly kick on the traction control/ABS and the right front brake will lock up. The steering wheel jerk is violent enough to remove the wheel from the drivers hands. No Traction control or ABS lights flash on the dash when this occurs and it has caused the vehicle to veer into oncoming traffic and also off the road. The dealer was unable to recreate the issue nor are there any stored codes/issues found when having the truck diagnosed. ABS and speed sensor wires have been reviewed and none were damaged during the brake job. All wheel speed sensors are functional and reading when the issue happens. This issue happens during dry or wet conditions and is random without warning.

  • Filed May 2025

    Parking brake locking up. There is recall on the brake module for my year make and model but my vehicle isn't on the list and I feel it should be. I'm having the same issues as they are. I can't drive it until it is fixed. Very dangerous.

  • Filed Dec 2024

    Seems to be a known problem according to a google search but brake fluid leaking from brake pedal onto drivers floor mat. Seems to be a bad brake booster according to google and happening for some at a few weeks to a couple months old in the newer ones. I noticed first on my truck around 58,000 miles.

  • Filed Nov 2022

    The contact owns a 2021 GMC Sierra 2500. The contact stated while approaching a stop sign and depressing the brake pedal, the brakes were squeaking. The vehicle was taken to the dealer and the contact was informed that the brake pads needed to be replaced. The brakes on the vehicle were replaced but the failure reoccurred. The vehicle was taken to another dealer and the caliper on the front driver’s side was replaced and the failure reoccurred. The vehicle was taken to another dealer who was aware of the issue however, there was no recall for the failure. The manufacturer was not contacted. The failure mileage was 800.

  • Showing the 5 most recent of 6.
• Electrical System6

  1 involved a crash

  • Filed Sep 2025

    When I’m in reverse the up the cameras turn off. On one incident I was backing up and the camera turned off causing me to back up into the wall of my house

  • Filed Jan 2025

    Headlights and turn signals failed. Flickering of various lights (Daytime running lamp, low beam, high beam, turn signals) followed by total failure. 3700 dollar repair at dealer to replace both headlamp assemblies. Barely over miles of warranty, but still in the 3 year warranty time period. Not having forward lighting is of course a major safety issue. Vehicle should be recalled. Many others are having the issue.

  • Filed Nov 2024

    On 11/21/24 noticed passenger headlight day light running light flickering. On 11/22/24 right turn indicator intermittent fast blink, dash message stated turn indicator failure. Once home, inspected passenger headlight assembly. Found DRL, turn signal, and low and high beam head lights were inoperative. On 11/25/24 went to GMC dealer/service. Staff seemed aware of issues and stated they are common, that they carry the $1,400 sealed assebly in stock. Vehicle is 4 months over warranty, but only has 29,000 miles. There is no visible damage to the assembly, but there is visible condensation inside the lens. GM has a published service bulletin, 01-08-42-001P, that specifically addresses this issue for my vehicle. The earliest date the issue could be diagnosed/service date is 12/10/24. A complete failure of this non-servicable headlight assembly is an absolute safety issue. Decreased daytime visability with the loss of one of two Daytime Running Lights, the lose of the front turn indicator to alert other drivers of my intentions, the lose of a set of low and high beam headlights. As mentioned, there assembies are a sealed LED light assembly. If any one of these lights fail, the only remedy is the replacement of the entire unit with a $1,400 part. GM has had multiple recalls of this same issue among their vehicle, but continues to produce the same failing pieces.

  • Filed Aug 2024

    Smog system check and Engan warning light keeps come on.

  • Filed Mar 2024

    The harness that hooks to bumper plug for trailer lighting is not completely water tight. Allows water in and creates buildup that weakens the connection as well as allows the plug wire connection to snap out and push out from the pin. Further inspection it was causing a short in the system. I attempted to clean and put some-electric grease on the plug to help clean it but then relaized 3 pins were broken and pushed back.

  • Showing the 5 most recent of 6.
• Structure5

  1 involved a crash · 1 involved a fire

  • Filed Apr 2026

    The contact owns a 2021 GMC Sierra 2500. The contact stated that on several occasions, the automatic power side-out step failed to extend as designed. The vehicle was not diagnosed or repaired. The manufacturer was notified of the failure. The failure mileage was 93,726.

  • Filed Mar 2024

    My tailgate unexpectedly open as I was driving down the road. (2021 GMC 2500 Denali Sierra) This was the second time this has happened and lost things driving down the road. (3 propane tanks and a small grill the first and then an air compressor the second time) Both times it happened I opened and closed the tailgate with the vehicle running. Both times I was unaware of tailgate opening and did not notice until I got home. The first time it happened I thought it was operator error but after this weekend, I looked into this and see there was a recall on it this month. I still felt it was necessary to report incidents.

  • Filed Jan 2024

    The tailgate latch is not waterproof, and opens on its own sometimes. this can allow things to fall out of your truck.

  • Filed Aug 2022

    Hit in the driver side tire, air bags didn’t release. Truck then went up in flames.

  • Filed Aug 2022

    when driving down the rode the center hood scoop blew off 0

• Latches/Locks/Linkages4

  • Filed Aug 2025

    The contact owns a 2021 GMC Sierra 2500. The contact received Manufacturer's Recall Number: N232426400, for water intrusion into the electronic gate-release switch. The vehicle was repaired. The contact stated that six months after the vehicle was repaired, the tailgate failed to operate as intended. While at the residence, the taillights and headlights were flashing. The contact also became aware that the tailgate had unlatched independently while the vehicle was parked. The message "Integrated Tailgate Open or Integrated Tailgate not Latched" was displayed. The contact stated that there was an abnormal clicking sound coming from the actuator when the tailgate opened independently. The vehicle was taken to the dealer, where it was diagnosed that there was water in the switch. The dealer informed the contact that the repairs were already made and, due to the water intrusion into the switch, the dealer refused to redo the repair under the previous recall. The vehicle was repaired. The manufacturer was notified of the failure, and denied assistance since the recall repair was already performed. The failure mileage was approximately 53,000.

  • Filed Apr 2025

    The contact owns a 2021 GMC Sierra 2500. The contact stated that the VIN was included in NHTSA Campaign Number: 24V060000 (Latches/Locks/Linkages) and the main exterior touchpad switch assembly was replaced. The contact stated that after the recall repair the second exterior touchpad switch assembly suddenly short circuited and caused the trunk to open unintendedly. The vehicle was returned to the dealer who stated that that only one exterior touchpad switch assembly was replaced, despite the remedy stating that the exterior touchpad switch assemblies would be replaced. The vehicle was not repaired. The manufacturer was informed of the failure and opened a case. The manufacturer referred the contact to the NHTSA Hotline to report the failure. The failure mileage was 55,700.

  • Filed Nov 2024

    The contact owns a 2021 GMC Sierra 2500. The contact stated that no visible tailgate was attached, and the contact was unaware if the vehicle had been repaired under NHTSA Campaign Number: 24V060000 (Latches/Locks/Linkages); however, the recall had been marked as completed under the VIN. The vehicle was taken to a local dealer where they advised the contact that the recall repair was completed. The vehicle was taken to another local dealer, Littleton Chevy (851 Meadow St Littleton, NH 03561); for a second opinion and was informed that the recall repairs had not been performed. In addition, the contact stated that the tailgate was replaced with an after-market part due to backorder issues. The contact stated that there was no failure experienced with the original part. The manufacturer was made aware of the issue. The contact had not experienced a failure. The failure mileage was 125,000.

  • Filed Jul 2024

    The contact owns a 2021 GMC Sierra 2500. The contact stated while driving approximately 25–35 MPH, the tailgate unlatched and opened unexpectedly. The contact stated that while the vehicle was parked, the tailgate opened independently. The contact stated that the tailgate down message was displayed after the failure. The vehicle was taken to an independent mechanic at a body shop, who determined that the failure was due to the touchpad. The vehicle was repaired. The vehicle was taken to a body shop, where it was replaced. The contact received notification of NHTSA Campaign Number: 24V060000 (Latches/Locks/Linkages); however, the part to do the recall repair was not yet available. The local dealer was not contacted. The contact stated that the manufacturer had exceeded a reasonable amount of time for the recall repair. The manufacturer was made aware of the issue. The failure mileage was approximately 49,000. Parts distribution disconnect.

• Unknown or Other3

  1 involved a crash · 1 involved a fire

  • Filed Apr 2026

    XXX Power Assist Step Reversing I have a 2021 GMC Sierra 2500HD that the local dealership (Ozark MO 65714) is stating has expired and not covered by the warranty. I researched online and as I understand this recall falls under SAFTEY recalls and is to be fixed and doesn't expire? It requires no parts but the reprogramming of the K4 Assist Step Control Module. What is my next step or recourse?

  • Filed Jan 2024

    The tailgate latch is not waterproof, and opens on its own sometimes. this can allow things to fall out of your truck.

  • Filed Aug 2022

    Hit in the driver side tire, air bags didn’t release. Truck then went up in flames.

• Forward Collision Avoidance3

  1 involved a crash

  • Filed Nov 2024

    I purchased a 2021 GMC Denali 2500 in December 2023. A couple days after purchasing the vehicle I received a message on the dash saying the front camera was not working. I took the vehicle into the dealership where they said they reset the computer and nothing was wrong with the vehicle. One month later I was involved in a collision where a vehicle turned in front of my vehicle and the Automatic Emergency Braking failed to activate. I applied the brakes but due to my delayed reaction time 1.5 seconds, I broadsided the small vehicle with my large truck. Luckily the speed was only 20 mph and no one was hurt or killed. At this time I did not know my vehicle was equipped with AEB. In October I discovered through GM and a different dealership that my vehicle was equipped with Automatic Emergency Braking. I have had several occasions when the AEB including the crash where the AEB should have activated but never did. In 11 months I have never had the AEB activate. I took the vehicle into the dealership where I bought the vehicle and they said their computer said everything was operating correctly. The tech never drove the vehicle where the AEB should have activated. I have driven many cars and even the same model vehicle as mine, so I know what the AEB feels like and my vehicle the AEB is not working. The dealership told me to take the vehicle they checked everything GM told them to check. When I talked to GM they told me to immediately take the truck to the dealership and the dealership did nothing.

  • Filed Aug 2024

    Smog system check and Engan warning light keeps come on.

  • Filed Feb 2021

    THE TRUCK IS PARKED AT DEALERSHIP

• Fuel/Propulsion System2

  • Filed Jul 2026

    After finishing a long drive south, I shut the engine off and a yellow engine code popped on. I connected my computer to it and revealed a P129F code (fuel pump control module). I have noticed that other GMC models have been included in a recall concerning this problem. The 2021 GMC 2500 Denali should be also since it is the same problem. This needs to be covered by the manufacturer since it is a constant problem.

  • Filed Jun 2026

    I am reporting repeated failures involving both the transmission and diesel emissions (DEF) system on my 2021 GMC Sierra 2500HD Denali equipped with the 6.6L Duramax diesel engine and Allison 10-speed automatic transmission. While under warranty, the truck required replacement of the aftertreatment fuel injector and later the Reductant Control Module due to DEF/emissions system failures. General Motors also completed recall-related transmission software updates on the vehicle. At approximately 154,833 miles, the transmission began shifting improperly, set transmission fault codes, and required complete replacement at my expense. Less than 5,000 miles later, the vehicle again experienced a "Service DEF System" warning with multiple diagnostic trouble codes. Repairs required replacement of the DEF tank, DEF heater assembly, and NOx sensor. These repeated failures involve major drivetrain and emissions components on a heavy-duty truck. DEF system failures can place the vehicle into reduced-power (derate) mode, limiting vehicle performance and creating potential safety concerns while driving or towing. I am submitting this complaint so these failures can be documented as part of NHTSA's evaluation of similar vehicles.

• Air Bags2

  1 involved a crash · 1 involved a fire

  • Filed Aug 2022

    The “Service Safety Restraint” alarm goes off continually on my 2021 GMC Sierra 2500HD AT4. The warranty is no longer valid as at the time of occurrence I was at 34,500 miles and when I took it in the warranty had expired due to exceeding 36,000 miles. Extended warranties were not purchased and this began approximately 8-9 months after purchase. The code given is “b0014 Driver Seat Side Air Bag Deployment Loop” with a description of high resistance in wiring or wiring harness. After much research I have found that many GMC 2021 vehicles and previous models have had this exact same issue. No dealership as of yet has offered to help or understand that this defect was of their own flawed design. The issue that I am having is exactly the same as other models such as the 2021 Yukon, Sierra 1500, Suburban and others. This is a safety issue and only want GMC to account for their flaw. I do not believe I should have to pay for a design flaw or equipment malfunction that is well known amongst GMC vehicles. I am asking the NHTSA to help me in this matter and the many others who are having the same issue and for the manufacturer to be accountable for their own flaw.

  • Filed Aug 2022

    Hit in the driver side tire, air bags didn’t release. Truck then went up in flames.

• Lane Departure1

  • Filed Feb 2025

    Known issue and has been attributed to a manufacturing defct, but no recall- Leaking headlight caused damage to headlight- now turn signal and headlight do not work. Entire assembly needs to be replaced, GM / Extended Warranty Company will not cover, this safety part. Head light and turn signal were working on the way to the dealer, 1 month later when we picked it up - Right turn signal malfuction reading appeared on dash, headlight blinking and will not work. Picked up on Friday 1/30/25, and made an appointment for the following Wednesday to take it back in. Was told by dealer today that the replacement will not be covered and will cost $2100.00 to replace. This is a safety part and the truck can not be driven legally or safely without both headlights working.

• Parking Brake1

  • Filed Nov 2023

    The contact owns a 2021 GMC Sierra 2500. The contact stated that on several occasions while in park(P) with the parking brake engaged, the parking brake warning light was illuminated. The contact also stated that the parking brake would not disengage until the vehicle was shifted into reverse(R). The contact stated that he observed a loud banging sound coming from the rear of the vehicle when the parking brake was finally disengaged. The vehicle was taken to a dealer where it was diagnosed that the driver’s side rear actuator needed to be replaced. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was 51,248.

• Seat Belts1

  • Filed Aug 2022

    The “Service Safety Restraint” alarm goes off continually on my 2021 GMC Sierra 2500HD AT4. The warranty is no longer valid as at the time of occurrence I was at 34,500 miles and when I took it in the warranty had expired due to exceeding 36,000 miles. Extended warranties were not purchased and this began approximately 8-9 months after purchase. The code given is “b0014 Driver Seat Side Air Bag Deployment Loop” with a description of high resistance in wiring or wiring harness. After much research I have found that many GMC 2021 vehicles and previous models have had this exact same issue. No dealership as of yet has offered to help or understand that this defect was of their own flawed design. The issue that I am having is exactly the same as other models such as the 2021 Yukon, Sierra 1500, Suburban and others. This is a safety issue and only want GMC to account for their flaw. I do not believe I should have to pay for a design flaw or equipment malfunction that is well known amongst GMC vehicles. I am asking the NHTSA to help me in this matter and the many others who are having the same issue and for the manufacturer to be accountable for their own flaw.

• Tires1

  • Filed Apr 2022

    LT245/75R17 I bought these tires on Walmart. com June 2021 and had Walmart install with road hazard and lifetime balance, I returned to Walmart in April 2022 and was told I had a defective tire, that it was coming apart, I can see the fibers around the issue area and soft spongy for approximately 14 inches sounds like glue not sticking when I push around the bead area, Walmart told me it was a manufacturer defective tire and they included that on the work order and also told me to take tire and contact manufacturer which I did, I have spoken and also emailed with a Michael Dorr with Unicorn Tire. without any positive results only denied a claim. this tire needs to be Inspected and I want a new one, this for sure is defective.

• Back Over Prevention1

  • Filed Feb 2021

    THE TRUCK IS PARKED AT DEALERSHIP

Safety ratings

NHTSA 5-Star Safety Ratings from government crash tests. Ratings can differ by cab style and 2WD/4WD.

NHTSA hasn't published star ratings for this truck. Many heavy-duty pickups aren't included in NHTSA's crash-test program, so this doesn't mean the truck is unsafe.