2025 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 2025 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.

• Tires:Pressure Monitoring And Regulating Systems

  Aug 2026 · #26V530000

  General Motors, LLC (GM) is recalling certain 2024-2025 Chevrolet Silverado 2500 and GMC Sierra 2500 vehicles equipped with the enhanced towing option and 20-inch accessory tire/wheel package. The tire information label may state the incorrect rear tire pressure, resulting in underinflated tires and preventing the tire pressure monitoring system (TPMS) from displaying a low tire pressure warning.

  Risk and fix

  Risk: Driving with underinflated tires can increase the risk of a crash.

  Fix: Dealers will inspect, update the engine control module (ECM) software, apply a tire label overlay, inflate tires to the correct pressure, and perform a tire pressure monitor system (TPMS) re-learn process as necessary, free of charge. Owner notification letters were mailed September 17, 2026. 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 N262561970. Vehicle Identification Numbers (VIN) involved in this recall became searchable on NHTSA.gov on August 13, 2026.

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.

• Service Brakes7

  • Filed Jul 2026

    My 2025 Sierra 2500HD repeatedly displays “Trailer Brakes Disabled—Service Required” with a lithium- and solar-equipped trailer. The truck passes the EL-52641 simulator, but the failure occurs intermittently while towing and resets after Park or reconnecting the trailer. This closely matches the higher-trailer-battery-voltage/backfeed condition described in N232414840. Please open a TAC case and determine whether my 2025 has the revised Trailer Brake Power Module or whether GM engineering authorizes module replacement.

  • Filed Jun 2026

    Normal driving 40mph brake failure and power steering loss. Towed vehicle to dealership

  • Filed May 2026

    Power steering pump failed when decelerating after 9500 miles. When power steering pump fails, power assisted braking also fails. Upon deceleration, I could not turn the steering wheel at all or stop the vehicle without extreme pressure on the brake pedal. I narrowly avoided impact with a concrete barricade at the entrance to a parking lot. GM issued a technical bulletin (DCS7112) on January 16, 2025 identifying the problem and failure and directing dealerships to replace the pump on inventory vehicles. No mention was made to repair or notify owners of the potential problem.

  • Filed Mar 2026

    On highway taking an exit. The brake pedal sank and did not engage at normal pressure, I had to push the brake all the way down for it to engage. Concurrently the steering wheel locked up where I could not turn the wheel at all. I drove straight through the exit ramp to the entrance ramp, luckily no one was entering the highway at the same time. I very well could have hurt some one else or myself. The steering wheel finally engaged where I had full power steering again and I was able to remove my truck off the highway and cautiously drove to a parking lot to get it towed. I have not tried to drive sense incident as it is at the dealer for service. The GMC Dealer has not inspected the vehicle yet, they are backed up with other services. There were no warning lamps at the time nor before the incident. Symptons see bellow. I have had issues with the brakes and it has been to the dealer 4 times including this incident, Service issue #1 at 21,501 miles -Breaks were pulsating, squealing and rough and it was shaking the steering column - The smell of burning breaks was present after drives -Solution they sanded down the hot spots on both rotors and pads for the front brakes Temporarily fixed the breaking and steering column shaking ( it did not solve the burning break smell problem. Service issue #2 at 28,142 miles Breaks were pulsating, squeaking, and steering column shaking - The smell of burning breaks was still present after drives. solution new front brake pads and rotors. Service issue #3 at 39,893 miles Rear brakes locked up while taking a turn on to a street Breaks were pulsating Squeaking and steering column shaking Smell of burning breaks is still present after drives solution machine front brake rotors. could not reproduce brake locking issue Final issue as mentioned above #4 @43,426 miles I cant help but think the constant break issues were warning signs.

  • Filed Sep 2025

    The contact owns a 2025 GMC Sierra 2500. The contact stated that while depressing the brake pedal to come to a complete stop, the brakes made a loud whistling and squealing sound. There were no warning lights illuminated. The vehicle was taken to the dealer, Bellamy Strickland Chevrolet GMC (145 Industrial Blvd, McDonough, GA 30253); who was unable to determine the cause of the failure. The dealer informed the contact that it was a known issue with no fix for the failure. The vehicle was not repaired. The vehicle was taken to a second dealer, who was also unable to diagnose the vehicle. The manufacturer was not informed of the failure. The mileage was approximately 5,000.

  • Showing the 5 most recent of 7.
• Steering7

  • Filed Jun 2026

    Normal driving 40mph brake failure and power steering loss. Towed vehicle to dealership

  • Filed May 2026

    Power steering pump failed when decelerating after 9500 miles. When power steering pump fails, power assisted braking also fails. Upon deceleration, I could not turn the steering wheel at all or stop the vehicle without extreme pressure on the brake pedal. I narrowly avoided impact with a concrete barricade at the entrance to a parking lot. GM issued a technical bulletin (DCS7112) on January 16, 2025 identifying the problem and failure and directing dealerships to replace the pump on inventory vehicles. No mention was made to repair or notify owners of the potential problem.

  • Filed Mar 2026

    On highway taking an exit. The brake pedal sank and did not engage at normal pressure, I had to push the brake all the way down for it to engage. Concurrently the steering wheel locked up where I could not turn the wheel at all. I drove straight through the exit ramp to the entrance ramp, luckily no one was entering the highway at the same time. I very well could have hurt some one else or myself. The steering wheel finally engaged where I had full power steering again and I was able to remove my truck off the highway and cautiously drove to a parking lot to get it towed. I have not tried to drive sense incident as it is at the dealer for service. The GMC Dealer has not inspected the vehicle yet, they are backed up with other services. There were no warning lamps at the time nor before the incident. Symptons see bellow. I have had issues with the brakes and it has been to the dealer 4 times including this incident, Service issue #1 at 21,501 miles -Breaks were pulsating, squealing and rough and it was shaking the steering column - The smell of burning breaks was present after drives -Solution they sanded down the hot spots on both rotors and pads for the front brakes Temporarily fixed the breaking and steering column shaking ( it did not solve the burning break smell problem. Service issue #2 at 28,142 miles Breaks were pulsating, squeaking, and steering column shaking - The smell of burning breaks was still present after drives. solution new front brake pads and rotors. Service issue #3 at 39,893 miles Rear brakes locked up while taking a turn on to a street Breaks were pulsating Squeaking and steering column shaking Smell of burning breaks is still present after drives solution machine front brake rotors. could not reproduce brake locking issue Final issue as mentioned above #4 @43,426 miles I cant help but think the constant break issues were warning signs.

  • Filed Oct 2025

    i experience a steering wheel shimmy between the speeds of 70- 75 miles an hour

  • Filed Aug 2025

    While towing a less than 2000 lb trailer I had total loss of power steering when speeds dropped below about 5 mph. I got off interstate and was turning right at the end of exit ramp and I could barely turn the vehicle. At the next stop sign it did the same thing. I stopped turned off the vehicle and restarted it and it continued this for the next few miles. Then just as suddenly as it started it stopped doing this and worked fine the rest of my trip.

  • Showing the 5 most recent of 7.
• Unknown or Other6

  3 involved a crash

  • Filed Sep 2026

    A driver hit me in the side of the car at around 70 mph to where it bent the frame of the truck and the airbags did not deploy causing a major issue and my daughters head to hit the side window.no warning lamps and it’s currently at a body shop right now

  • Filed Sep 2026

    Air bags didn’t deploy after being hit so hard in the side it bent the frame and my daughters head head hit the side window

  • Filed Aug 2026

    My 2025 GMC Sierra 2500 experienced repeated electrical failures that caused complete battery drainage and multiple overnight no‑start conditions within the first year of ownership. These failures occurred in extreme desert heat, where temperatures in [XXX] reach 120°F. A vehicle that repeatedly fails to start in these conditions creates a serious safety hazard, including risk of heat‑related medical emergencies if stranded. The defect persisted despite multiple repair attempts and two battery replacements. The dealership ultimately told me I would “need to replace batteries as needed,” instead of diagnosing the underlying electrical issue. Detailed Description of the Problem Multiple overnight no‑start incidents Several jump‑start events required XXX – 15,265 miles: Battery replaced due to electrical drainage XXX: Battery replaced again for the same defect Electrical system continued to fail after repairs Dealer advised ongoing battery replacement rather than addressing root cause The truck was unreliable and unsafe in extreme heat. A no‑start condition in 120°F temperatures can leave occupants stranded without air conditioning, posing a life‑threatening risk. Frequency of the Problem The electrical failure occurred multiple times over several months, including late 2025, early 2026, and again in mid‑2026. The defect was consistent and repeatable. Consequences Risk of being stranded in extreme heat Loss of air conditioning during no‑start events Potential for heat exhaustion or heat stroke Vehicle unreliable for daily use Safety hazard for driver and passengers INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

  • Filed Feb 2026

    Component / System Failure The exhaust system, specifically the exhaust manifolds and previously the EGR system components, appear to have failed or malfunctioned, allowing exhaust gases to enter the passenger cabin. The dealer initially replaced the EGR cooler diverter on December 23, 2025. However, the condition persisted. On February 3, 2026, cracked exhaust manifolds were identified by the dealership, and a major front-end teardown was advised to complete the repair. The vehicle is currently available for inspection upon request. ⸻ How Safety Was Put at Risk The malfunction allowed exhaust gases, including carbon monoxide, to enter the passenger cabin during vehicle operation. Carbon monoxide readings inside the cabin reached up to 50 parts per million (ppm) while driving. Carbon monoxide is a toxic gas that can cause: •Headaches •Dizziness •Impaired concentration •Nausea •Vision disturbances Because carbon monoxide is odorless and colorless, this presents a significant safety risk, particularly at highway speeds where driver alertness is critical. The exposure occurred while operating the vehicle in normal driving conditions. This created a potential risk of driver impairment and increased risk of collision. ⸻ Has the Problem Been Reproduced or Confirmed? Yes. The vehicle was presented to the dealership three times for the same exhaust intrusion concern: •December 16, 2025 •December 29, 2025 •February 3, 2026 During the February 3 visit, the dealership confirmed cracked exhaust manifolds requiring major disassembly for repair. The carbon monoxide readings were observed during vehicle operation. The exhaust odor and intrusion symptoms were consistently present following the first attempted repair. ⸻ Has the Vehicle Been Inspected by Manufacturer or Others? The vehicle has been inspected by the authorized dealership on multiple occasions. Two manufacturer customer care cases were opened.

  • Filed Jan 2026

    Had a minor wreck was to be two weeks to then it had to have a new frame they said it coun't be repair if a minor wreck can do this much damage there is a problem with subpar frames that any sudden stops or turns

  • Showing the 5 most recent of 6.
• Power Train4

  • Filed Mar 2026

    The transfer case leaked out all the fluid while driving over a period of time and damaged internal parts before the first oil change. This has happened 2 times now, and is currently leaking again with less than 10k miles.

  • Filed Dec 2025

    The 2025 GMC Sierra 2500 HD, equipped with the 10-speed "Allison" transmission, rough shifting,

  • Filed Nov 2025

    transmission locked up 8 times from 1,050 miles to current 3,885 miles. It has happens each time around 40 mph. Each time it’s like hitting the brakes. The 8th time it locked really hard like slamming on the brakes. I’m worried with winter months what will happen on snow/ice covered roads. Called dealership and was told GM refuses to do anything until it completely fails. It seems they know what the problem is but refuse to fix till the truck stops moving during complete failure. No warning lamps and dealer ship says they can’t replicate it.

  • Filed May 2025

    Transmission fluid overheating, which is a known issue in other GM models with 6.6L diesel with 12 speed allison transmission. Confirmed by warning message received on dashboard and transmission fluid temperature gauge. This occurred within 3 weeks of purchase. Dealer confirmed “Valve” needs to be replaced. Part is on back order with no arrival eta. Service advisor indicates the truck is not safe to drive and remains in the service department.

• Engine4

  • Filed Feb 2026

    Component / System Failure The exhaust system, specifically the exhaust manifolds and previously the EGR system components, appear to have failed or malfunctioned, allowing exhaust gases to enter the passenger cabin. The dealer initially replaced the EGR cooler diverter on December 23, 2025. However, the condition persisted. On February 3, 2026, cracked exhaust manifolds were identified by the dealership, and a major front-end teardown was advised to complete the repair. The vehicle is currently available for inspection upon request. ⸻ How Safety Was Put at Risk The malfunction allowed exhaust gases, including carbon monoxide, to enter the passenger cabin during vehicle operation. Carbon monoxide readings inside the cabin reached up to 50 parts per million (ppm) while driving. Carbon monoxide is a toxic gas that can cause: •Headaches •Dizziness •Impaired concentration •Nausea •Vision disturbances Because carbon monoxide is odorless and colorless, this presents a significant safety risk, particularly at highway speeds where driver alertness is critical. The exposure occurred while operating the vehicle in normal driving conditions. This created a potential risk of driver impairment and increased risk of collision. ⸻ Has the Problem Been Reproduced or Confirmed? Yes. The vehicle was presented to the dealership three times for the same exhaust intrusion concern: •December 16, 2025 •December 29, 2025 •February 3, 2026 During the February 3 visit, the dealership confirmed cracked exhaust manifolds requiring major disassembly for repair. The carbon monoxide readings were observed during vehicle operation. The exhaust odor and intrusion symptoms were consistently present following the first attempted repair. ⸻ Has the Vehicle Been Inspected by Manufacturer or Others? The vehicle has been inspected by the authorized dealership on multiple occasions. Two manufacturer customer care cases were opened.

  • Filed Jan 2026

    Burning an unusual amount of oil. Have seen several instances of blue smoke in the exhaust. Have had to add over a quart of oil twice in less than 6500 miles.

  • Filed Oct 2025

    We were towing a fifth wheel camper with our truck on an interstate highway in Pennsylvania when our serpentine belt burst suddenly and without warning. Our truck is a 2025 model with only 10,000 miles driven. We lost all power steering and power brakes of both the truck and the camper and the motor shut off while we were driving at 65 mph. My husband struggled to gain control of the truck and camper which was severely fishtailing and was eventually able to get over to the shoulder and stop the vehicles. We were towed to a GMC dealership where a factory technician happened to be on site providing an in-service for the dealership's service team. He inspected our truck and we were told that he said that GMC is aware of catastrophic failures in these serpentine belts. We were also told that he took photos and was sending a report to the GMC factory regarding our situation. When the serpentine belt blew, it damaged fan blades, shroud, oxygen sensors and our air conditioner belt (which fell off 200 miles later). We had absolutely no warning of the sudden catastrophic failure of the serpentine belt and came close to losing our lives. Our biggest concern is that the serpentine belt was replaced with the exact same model of belt that failed. What does it take for a company to recall a known defective belt? A fatality? We were very fortunate to have walked away without injury or losing our lives. We have written a letter to GMC but they have not contacted us as of yet.

  • Filed Jan 2025

    The contact owns a 2025 GMC Sierra 2500. The contact stated that while driving at an undisclosed speed, the vehicle failed to accelerate as intended while depressing the accelerator pedal. The check engine warning light was illuminated. In addition, the contact stated that the RPM was fluctuating while driving. The vehicle was towed to a local dealer however, the vehicle was not diagnosed or repaired due to the warranty. The manufacturer was made aware of the failure. The failure mileage was approximately 600.

• Air Bags2

  2 involved a crash

  • Filed Sep 2026

    A driver hit me in the side of the car at around 70 mph to where it bent the frame of the truck and the airbags did not deploy causing a major issue and my daughters head to hit the side window.no warning lamps and it’s currently at a body shop right now

  • Filed Sep 2026

    Air bags didn’t deploy after being hit so hard in the side it bent the frame and my daughters head head hit the side window

• Exterior Lighting2

  • Filed Aug 2026

    My 2025 GMC Sierra 2500 experienced repeated electrical failures that caused complete battery drainage and multiple overnight no‑start conditions within the first year of ownership. These failures occurred in extreme desert heat, where temperatures in [XXX] reach 120°F. A vehicle that repeatedly fails to start in these conditions creates a serious safety hazard, including risk of heat‑related medical emergencies if stranded. The defect persisted despite multiple repair attempts and two battery replacements. The dealership ultimately told me I would “need to replace batteries as needed,” instead of diagnosing the underlying electrical issue. Detailed Description of the Problem Multiple overnight no‑start incidents Several jump‑start events required XXX – 15,265 miles: Battery replaced due to electrical drainage XXX: Battery replaced again for the same defect Electrical system continued to fail after repairs Dealer advised ongoing battery replacement rather than addressing root cause The truck was unreliable and unsafe in extreme heat. A no‑start condition in 120°F temperatures can leave occupants stranded without air conditioning, posing a life‑threatening risk. Frequency of the Problem The electrical failure occurred multiple times over several months, including late 2025, early 2026, and again in mid‑2026. The defect was consistent and repeatable. Consequences Risk of being stranded in extreme heat Loss of air conditioning during no‑start events Potential for heat exhaustion or heat stroke Vehicle unreliable for daily use Safety hazard for driver and passengers INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

  • Filed Apr 2026

    Reverse lamps are not bright. Camera does not brighten area either. Very unsafe to reverse in the dark. Have to touch the brake pedal to be able to see while backing. Also have tried the LEDs in the mirrors while backing- although the LEDs are bright- lights to see while backing are insufficient on the stop lamps.

• Structure2

  1 involved a crash

  • Filed Apr 2026

    The contact owns a 2025 GMC Sierra 2500. The contact stated that the front driver’s side door handle failed to operate as needed, and the contact was unable to exit the vehicle through the driver’s side door. The vehicle was taken back to the dealer, and a new handle was ordered. The part was replaced under warranty. Soon after the repair, the liftgate failed to open or close as needed and became inoperable. The vehicle was taken back to the dealer for the liftgate to be serviced under warranty. The manufacturer was not notified of the failure. The vehicle remained with the dealer unrepaired. The failure mileage was approximately 300.

  • Filed Oct 2025

    The accident occurred when the tailgate opened without warning or any buttons being pushed while towing a boat trailer. The tailgate become bound between the truck and trailer. The tailgate was damaged and limited my ability to turn the truck. My truck is normally parked in a garage and doesn’t sit in the weather. This truck is my 3rd vehicle so it doesn’t really get driven unless it is pulling a trailer, I tow with it all the time but very rarely use the bed or tailgate. Monday June 16 – Drove from Gallatin, Tn – Eddyville, Ky – Paducah, Ky the weather was constantly heavy rain and wind. Tuesday June 17 – Drove from Paducah, Ky to Defeated, TN more of the same bad storm. There were 3 of us and no one opened the tailgate, we hooked up to my boat and drove less than a quarter mile to the boat ramp, when we arrived, the tailgate had opened and the stairs on the boat had impacted the small part of the tailgate during a right turn. Prior to leaving the driveway and after hooking up the boat I had to back up slightly and remove pressure to remove the chock block from the boat trailer tires. (I would have noticed that the tailgate was open) this happened with no warning, put me and my passengers at risk and did over $1000 dollars in property damage. I was expecting GM to replace the parts that were faulty and the small part of the tailgate that was damaged. I returned twice to Larry Stovesand GMC and had them access the switch. They have refused to supply paperwork from those visits and have become dismissive and deceptive. The contact there is Craig Morgan cmorgan@lsbuickgmc.com

• Suspension2

  1 involved a crash

  • Filed Jan 2026

    Had a minor wreck was to be two weeks to then it had to have a new frame they said it coun't be repair if a minor wreck can do this much damage there is a problem with subpar frames that any sudden stops or turns

  • Filed Jun 2025

    The passenger side rear wheel went into a pothole while making a right turn on a city street. This resulted in the right rear leaf spring breaking at the forward mounting point. This caused thr rear axle to swivel impacting the rear of the wheel well. The ESC malfunction indicator and impact sensor malfunction llights illuminated appropriately 2-3 miles later after I was in a highway. This is a significant safety concern as I was at an increased speed in heavy traffic by the time the lights illuminated. This not only puts the vehicle occupants at risk, this is potentially a significant risk to other motorist. There were no noticeable indications of damage besides pulling until I was at appropriately 55mph on the highway. The vehicle is currently at a dealership for repair.

• Equipment2

  • Filed Dec 2025

    The contact owns a 2025 GMC Sierra 2500. The contact researched online and became aware that there was a recent recall under NHTSA Campaign Number: 25V815000 (Equipment) for the Owner's Manual. The contact stated that the vehicle was sold without the Owner's Manual. The contact stated that the manufacturer was called and was advised that the recall was only related to the 2026 Chevrolet Silverado models and the vehicle was not the same year, make or model. The contact was attempting to retain a physical copy of the Owner’s Manual and thought that it was a safety issue since there was a safety recall. The contact had not experienced a failure.

  • Filed Oct 2025

    See attached document for complaint.

• Electrical System1

  • Filed Aug 2026

    My 2025 GMC Sierra 2500 experienced repeated electrical failures that caused complete battery drainage and multiple overnight no‑start conditions within the first year of ownership. These failures occurred in extreme desert heat, where temperatures in [XXX] reach 120°F. A vehicle that repeatedly fails to start in these conditions creates a serious safety hazard, including risk of heat‑related medical emergencies if stranded. The defect persisted despite multiple repair attempts and two battery replacements. The dealership ultimately told me I would “need to replace batteries as needed,” instead of diagnosing the underlying electrical issue. Detailed Description of the Problem Multiple overnight no‑start incidents Several jump‑start events required XXX – 15,265 miles: Battery replaced due to electrical drainage XXX: Battery replaced again for the same defect Electrical system continued to fail after repairs Dealer advised ongoing battery replacement rather than addressing root cause The truck was unreliable and unsafe in extreme heat. A no‑start condition in 120°F temperatures can leave occupants stranded without air conditioning, posing a life‑threatening risk. Frequency of the Problem The electrical failure occurred multiple times over several months, including late 2025, early 2026, and again in mid‑2026. The defect was consistent and repeatable. Consequences Risk of being stranded in extreme heat Loss of air conditioning during no‑start events Potential for heat exhaustion or heat stroke Vehicle unreliable for daily use Safety hazard for driver and passengers INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

• Fuel/Propulsion System1

  • Filed Feb 2026

    Component / System Failure The exhaust system, specifically the exhaust manifolds and previously the EGR system components, appear to have failed or malfunctioned, allowing exhaust gases to enter the passenger cabin. The dealer initially replaced the EGR cooler diverter on December 23, 2025. However, the condition persisted. On February 3, 2026, cracked exhaust manifolds were identified by the dealership, and a major front-end teardown was advised to complete the repair. The vehicle is currently available for inspection upon request. ⸻ How Safety Was Put at Risk The malfunction allowed exhaust gases, including carbon monoxide, to enter the passenger cabin during vehicle operation. Carbon monoxide readings inside the cabin reached up to 50 parts per million (ppm) while driving. Carbon monoxide is a toxic gas that can cause: •Headaches •Dizziness •Impaired concentration •Nausea •Vision disturbances Because carbon monoxide is odorless and colorless, this presents a significant safety risk, particularly at highway speeds where driver alertness is critical. The exposure occurred while operating the vehicle in normal driving conditions. This created a potential risk of driver impairment and increased risk of collision. ⸻ Has the Problem Been Reproduced or Confirmed? Yes. The vehicle was presented to the dealership three times for the same exhaust intrusion concern: •December 16, 2025 •December 29, 2025 •February 3, 2026 During the February 3 visit, the dealership confirmed cracked exhaust manifolds requiring major disassembly for repair. The carbon monoxide readings were observed during vehicle operation. The exhaust odor and intrusion symptoms were consistently present following the first attempted repair. ⸻ Has the Vehicle Been Inspected by Manufacturer or Others? The vehicle has been inspected by the authorized dealership on multiple occasions. Two manufacturer customer care cases were opened.

• Hydraulic1

  • Filed Sep 2025

    The contact owns a 2025 GMC Sierra 2500. The contact stated that while depressing the brake pedal to come to a complete stop, the brakes made a loud whistling and squealing sound. There were no warning lights illuminated. The vehicle was taken to the dealer, Bellamy Strickland Chevrolet GMC (145 Industrial Blvd, McDonough, GA 30253); who was unable to determine the cause of the failure. The dealer informed the contact that it was a known issue with no fix for the failure. The vehicle was not repaired. The vehicle was taken to a second dealer, who was also unable to diagnose the vehicle. The manufacturer was not informed of the failure. The mileage was approximately 5,000.

• Vehicle Speed Control1

  • Filed Jan 2025

    The contact owns a 2025 GMC Sierra 2500. The contact stated that while driving at an undisclosed speed, the vehicle failed to accelerate as intended while depressing the accelerator pedal. The check engine warning light was illuminated. In addition, the contact stated that the RPM was fluctuating while driving. The vehicle was towed to a local dealer however, the vehicle was not diagnosed or repaired due to the warranty. The manufacturer was made aware of the failure. The failure mileage was approximately 600.

Safety ratings

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