2021 Gmc SIERRA 2500 problems and owner complaints
Explore the records behind recurring owner reports.
Key facts
51 owner complaints analyzed
6 distinct recall campaigns
54,000 mi median reported failure mileage
Scope: 2021 model year. Data snapshot: . 14 complaints include usable failure mileage.
Most common problems
Power Train is the most frequently named component, appearing in 12 of 51 complaints (23.5%). A complaint can name multiple components.
| Topic | Matching reports | Share of complaints |
|---|---|---|
| Transmission and shifting | 14 | 27.5% |
| Braking behavior | 8 | 15.7% |
| Engine operation | 3 | 5.9% |
| Electrical and battery issues | 2 | 3.9% |
| Fuel system concerns | 2 | 3.9% |
| Steering behavior | 1 | 2.0% |
Topic matches use published keyword rules. They describe mentions, including negations or comparisons, and do not confirm a diagnosis. Read the matching rules.
Component breakdown
Number of unique complaints naming each component. Top eight shown.
| Category | Count |
|---|---|
| Power Train | 12 |
| Exterior Lighting | 9 |
| Engine | 8 |
| Electrical System | 6 |
| Service Brakes | 6 |
| Structure:Body | 4 |
| Latches/Locks/Linkages | 3 |
| Unknown Or Other | 3 |
Power Train: 12; Exterior Lighting: 9; Engine: 8; Electrical System: 6; Service Brakes: 6; Structure:Body: 4; Latches/Locks/Linkages: 3; Unknown Or Other: 3
Reported problems by failure mileage
Complaint counts in mileage bands. These are not failure rates per vehicle or mile.
| Category | Count |
|---|---|
| Under 25,000 | 2 |
| 25,000 to 49,999 | 2 |
| 50,000 to 74,999 | 5 |
| 75,000 to 99,999 | 3 |
| 100,000 to 149,999 | 2 |
| 150,000 and above | 0 |
Under 25,000: 2; 25,000 to 49,999: 2; 50,000 to 74,999: 5; 75,000 to 99,999: 3; 100,000 to 149,999: 2; 150,000 and above: 0
50,000 to 74,999 miles has the most reports with usable mileage (5). 37 complaints have missing, zero or invalid mileage.
Complaints over time
Year the complaint was filed, not the vehicle model year or incident year. The snapshot year is partial.
| Category | Count |
|---|---|
| 2021 | 2 |
| 2022 | 6 |
| 2023 | 4 |
| 2024 | 15 |
| 2025 | 14 |
| 2026 | 10 |
2021: 2; 2022: 6; 2023: 4; 2024: 15; 2025: 14; 2026: 10
Pattern summary
Power Train leads the component reports. Transmission and shifting appears in 14 complaint narratives. Braking behavior appears in 8 complaint narratives. Engine operation appears in 3 complaint narratives. Use these patterns to inspect individual reports and prepare questions for a mechanic.
Calculated from recorded counts. An AI narrative has not been published for this selection.
Complaint evidence
Examples provide context, not a representative sample or a verified diagnosis.
Owner report 11526772 · 2023-06-13 (June 13, 2023)
The owns a 2021 GMC Sierra 2500. The contact stated while driving 70 MPH, the RPM revved up to 6,000 RPM. Additionally, the vehicle lost motive power. The vehicle was taken to the dealer, who informed the contact that the transmission needed to be replaced. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was 47,000. The VIN was not available.
Owner-reported narrative. 47,000 miles reported. Look up ODI 11526772 at NHTSA ↗
Owner report 11557590 · 2023-11-30 (November 30, 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 repla…
Owner-reported narrative. 51,248 miles reported. Look up ODI 11557590 at NHTSA ↗
Owner report 11441628 · 2021-11-24 (November 24, 2021)
Brake pads have excessive squealing. Squealing implies incorrect pressure to rotor to stop the vehicle, which highly concerns me as an operator. According to the dealer where I reported the issue, there is a technical bulletin that approves replacement of the brake pads for free if reported in first 7500 miles. My truck exceeded that mileage when I noticed the squealing. If this was a recall for the defective brakes, the dealer would cover the costs to repair, but not for a technical bulletin according to the service department, and confirmed…
Owner-reported narrative. Look up ODI 11441628 at NHTSA ↗
Owner report 11491956 · 2022-11-02 (November 2, 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 t…
Owner-reported narrative. 800 miles reported. Look up ODI 11491956 at NHTSA ↗
Owner report 11631610 · 2024-12-19 (December 19, 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 …
Owner-reported narrative. 134,000 miles reported. Look up ODI 11631610 at NHTSA ↗
Owner report 11726714 · 2026-03-24 (March 24, 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 rap…
Owner-reported narrative. Look up ODI 11726714 at NHTSA ↗
Owner report 11478489 · 2022-08-09 (August 9, 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 p…
Owner-reported narrative. Look up ODI 11478489 at NHTSA ↗
Owner report 11574476 · 2024-02-28 (February 28, 2024)
The contact owns a 2021 GMC Sierra 2500. The contact stated that the vehicle was equipped with an engine block heater that he plugged into the vehicle when the weather was below 32 degrees to start the vehicle. The contact stated that he noticed that the engine block heater was causing the GFCI outlet in his residence, to experience an electrical short circuit. The dealer was notified of the failure and informed the contact that it was a known failure. An appointment was scheduled for diagnostic testing. The vehicle was not diagnosed or repaire…
Owner-reported narrative. 55,000 miles reported. Look up ODI 11574476 at NHTSA ↗
Owner report 11746749 · 2026-06-26 (June 26, 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 im…
Owner-reported narrative. Look up ODI 11746749 at NHTSA ↗
Owner report 11753689 · 2026-07-30 (July 30, 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.
Owner-reported narrative. Look up ODI 11753689 at NHTSA ↗
Owner report 11692084 · 2025-10-08 (October 8, 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 dia…
Owner-reported narrative. Look up ODI 11692084 at NHTSA ↗