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GMC Sierra 2500Model year report

2021 GMC Sierra 2500 Problems

Compared with other GMC Sierra 2500 years

More complaints than typical for this model

69/100 1.6× a typical year · 50 = typical

Nearby years with a typical complaint level and no open NHTSA investigation: 2018, 2019, 2023

Based only on NHTSA complaints, recalls and investigations. Not adjusted for how many vehicles were sold, and not a reliability rating. How this is calculated

Complaints
52filed with NHTSA
Median mileage
53,000miles, 15 complaints with mileage
Recalls
6campaigns on record
Trend
RisingComplaints filed in the last 3 full calendar years are at least 25% higher than in the 3 years before.

Sources: NHTSA records for the 2021 GMC Sierra 2500 (complaints, recalls, investigations). Report an error

What owners report

Owners of this 2021 GMC Sierra 2500 most often report headlights and turn signals that flicker or fail, and some link this to moisture in the lamp assembly. The second main group describes sudden loss of motive power and transmission failures, often while towing or at highway speed. Brake squeal, lock-up, and parking brake problems, along with tailgate unlatching, appear as smaller groups.

  1. Exterior lighting

    Headlights and turn signals flicker or fail

    • 10 complaints (19%)
    • median 53,000 mi at 4.8 yrs old (1 states mileage, few)
    • filed 2023–2026

    Owners describe headlights, daytime running lights, and turn signals that flicker, flash at random, or stop working entirely. Many complaints link the failure to water or condensation getting into the headlamp assembly and its control module, and some describe high beams that switch on and off. A complaint says the dealer called the problem common and had the assembly in stock, while other complaints say the repair cost was high and the warranty did not cover it. Few lighting complaints list mileage, and those that do mention roughly 29,000 to 40,000 miles on trucks about three years old.

    1 related service bulletin

    What to check: Check the headlamp and turn signal housings for condensation or water inside the lens, and confirm that every light works on both sides during a test drive. Ask whether any body or upfit work was done, since a service bulletin covers fast-flashing turn signals after a factory box is removed.

    2 excerpts from owner complaints in NHTSA records

    “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. …”

    NHTSA complaint #11709159, filed 2026-01

    “The driver side headlamp stopped working, Condensate buildup may be a contributing factor. No accident and vehicle is meticulously maintained. No reason for lamp seals to be damaged or wear. Barely three years old and requires a replacement at $1400 for the part and another $1000 in labor. Outside of 36000 mile warranty.”

    NHTSA complaint #11559776, filed 2023-12
  2. Transmission and drivetrain

    Sudden loss of power and transmission failure

    • 15 complaints (29%)
    • median 51,248 mi at 4.1 yrs old (7 state mileage, few)
    • 1 mention a crash, fire or injury
    • filed 2023–2026

    Owners describe the truck suddenly losing motive power, sometimes with the engine revving high. Some complaints describe unexpected gear changes, such as a downshift while towing or the transmission leaving first gear, and some describe a sudden stop or a crash on the road. Dealers reportedly found transmission, solenoid, or valve body faults and recommended replacement, and some complaints say the truck stayed at the dealer for an extended period. A complaint says a later recall described a similar scenario, and that the claim for its repair was denied. Mileage given in these complaints ranges from about 38,000 to 134,000 miles, and many failures happened while towing or at highway speed.

    Recall 24V7970002 related service bulletins

    What to check: Ask whether the transmission control valve campaign and the cooler line bulletin have been carried out. On a test drive, check for harsh or late shifts, unexpected revving, and any loss of acceleration at highway speed.

    2 excerpts from owner complaints in NHTSA records

    “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. …”

    NHTSA complaint #11726714, filed 2026-03

    “While driving down the highway pulling a trailer the truck started to slow down rapidly. We were able to pull to the side of the road before the truck came to a complete stop on its own. From that point forward, we could not get the truck to move forward even in 4WD. Ended up towing the truck back and a repair shop determined the transmission needed replaced. About 4 months later, we received notice of a recall describing a similar scenario. …”

    NHTSA complaint #11649449, filed 2025-03
  3. Brakes

    Brake squeal, lock-up and parking brake faults

    • 7 complaints (13%)
    • median 26,024 mi at 2.3 yrs old (2 state mileage, few)
    • 1 mention a crash, fire or injury
    • filed 2021–2026

    Owners describe brake pads that squeal, including cases where the squeal returned after pad or caliper work at the dealer. Other complaints describe a parking brake warning light that stays on, a parking brake that will not release until the truck is shifted into reverse, a loud banging noise, and a parking brake that locks up, and a complaint says a parking brake lining separated from its backing plate. A complaint says the dealer cited a technical bulletin for free pad replacement that applied only to early mileage. A complaint describes a front brake that locked up after a brake service, with traction control and ABS engaging, and says the dealer could not reproduce the problem or find stored codes. Mileage given in these complaints ranges from about 800 to 51,248 miles, so both newer and higher-mileage trucks are represented.

    What to check: On a test drive, check that the parking brake releases and sets normally and that its warning light goes out, and listen for squealing or banging when braking. Ask whether any brake pad, caliper, or parking brake shoe work appears in the service records.

    2 excerpts from owner complaints in NHTSA records

    “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. …”

    NHTSA complaint #11441628, filed 2021-11

    “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.”

    NHTSA complaint #11662387, filed 2025-05
  4. Latches, locks and linkages

    Tailgate unlatches or opens unexpectedly

    • 5 complaints (10%)
    • median 53,000 mi at 4.0 yrs old (3 state mileage, few)
    • filed 2024–2025

    Owners report the tailgate opening or unlatching on its own, sometimes while driving at low speed and sometimes while the truck was parked. Some complaints link the problem to the electronic gate-release or touchpad switch, and some say items were lost from the bed on the road. Some owners say the tailgate opened again after a recall repair, and a complaint says the dealer's repair did not match the recall remedy. Mileage given in these complaints ranges from about 49,000 to 125,000 miles, and some trucks had already been through a recall repair when the problem returned.

    Recall 24V060000

    What to check: Ask whether recall 24V060000 has been completed on this VIN and check the recall record. On a walk-around, confirm the tailgate latches fully and that no tailgate-open message shows on the dash.

    2 excerpts from owner complaints in NHTSA records

    “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. …”

    NHTSA complaint #11579498, filed 2024-03

    “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. …”

    NHTSA complaint #11624010, filed 2024-11, 125,000 miles

Buying note. Headlight and turn signal failures and transmission power-loss complaints are the main themes for this model year, so checking the lamp housings for moisture and taking a longer test drive at highway speed are practical steps. Asking whether the transmission control valve campaign and the tailgate recall have been completed can also help a buyer review the service history.

Summary written with AI from a sample of 42 NHTSA complaints for this model year (picked at random, with complaints that state a mileage and recent ones taken first), then checked automatically against the source records. Where a problem shows a complaint count, every complaint for this model year was matched with fixed keyword rules (written with AI and tested against the sample), and the mileage, age and repair figures are calculated from those complaints; owners' figures are as stated, not verified. Other counts refer to the sample. The excerpts come from NHTSA's public complaint records and are unverified; capitalisation is normalised, NHTSA staff notes are removed, and shortened text ends with “…”. Something wrong? Request a correction.

NHTSA recorded 52 consumer complaints for the 2021 GMC Sierra 2500. 15 of the complaints include a mileage, and 33% of those were filed for vehicles with under 50,000 miles; the median is 53,000 miles. Of all complaints, 4 involved a crash, 1 a fire, 1 an injury, according to the filers. NHTSA lists 6 recall campaigns and 1,061 technical service bulletins for this model year. Compared with the other 14 GMC Sierra 2500 model years that have at least 25 complaints and are old enough to compare, this one scores 69 out of 100, where 50 is a typical year for the model (more complaints than typical for this model). The comparison allows for the era and for how long each year has had to collect complaints, but not for how many vehicles were sold.

Which parts are reported most

Complaints can name more than one part, so the counts add up to more than the total. Select a part to see its complaints, recalls and bulletins.

Also reported: Fuel system (2), Back-over prevention (rear camera) (1), Lane departure (1), Seat belts (1), Tires (1).

Example complaints

Transmission and drivetrain: “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.”

NHTSA complaint #11526772, filed 2023-06, 47,000 miles

Exterior lighting: “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.”

NHTSA complaint #11633825, filed 2025-01

Engine: “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. …”

NHTSA complaint #11746749, filed 2026-06

Brakes: “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.”

NHTSA complaint #11628813, filed 2024-12

Mileage when problems were reported

33% of the 15 complaints with a mileage were filed for vehicles with under 50,000 miles; the middle half falls between 49,000 and 77,000 miles.

13%0–100%10–2520%25–5033%50–7520%75–10013%100–1500%150+
Share of complaints by mileage when the problem was reported, in thousands of miles (15 complaints with mileage). Red bars: under 50,000 miles. Bucket widths differ. Median: 53,000 miles.

Complaints by year filed

Trend: rising. Complaints filed in the last 3 full calendar years are at least 25% higher than in the 3 years before.

20212022202320241520252026
Complaints by year the complaint was filed with NHTSA. Red bars: the last 3 full calendar years used for the trend. The current year (2026) is partial.

Recalls and investigations

Recall details for the 2021 GMC Sierra 2500 → · Check a VIN at nhtsa.gov/recalls

Technical service bulletins

TSBs are manufacturer notes to dealers about known repair procedures. They are not recalls and do not by themselves mean a vehicle has a fault. 1,061 on record; the latest 10 are shown.

See all 1,061 bulletins →

Other model years of the GMC Sierra 2500

YearComplaintsMedian miRecallsCrash ★MPGScore (50 = typical)Trend
2026129,0001———Too new
2025281,3001——Too new to compareToo new
20241079,9044——Too new to compareToo new
20233334,0001——40 · TypicalToo new
20224415,1673——65 · MoreRising
20215253,0006——69 · MoreRising
20207931,8009——98 · MoreRising
20193228,72974—50 · TypicalRising
20183510,00054—52 · TypicalFalling
20173722,06064—53 · TypicalFalling
20165929,50064—64 · TypicalStable
20158937,02363–4—93 · MoreFalling
20143039,00022–4—10 · FewerFalling
20134660,00032–4—0 · FewerStable
20123168,50033–4—2 · FewerRising
20116355,4004——34 · FewerFalling
20101077,0005———Not enough data
20093139,6005——38 · TypicalFalling
20086367,5003——17 · FewerFalling
20078370,0003——Not compared (before 2008)Rising
20066643,5001——Not compared (before 2008)Falling
200511560,0001—11Not compared (before 2008)Falling
200414360,0001——Not compared (before 2008)Falling
200316073,0000——Not compared (before 2008)Falling
200213485,5001——Not compared (before 2008)Rising
200113465,0002——Not compared (before 2008)Stable
20004891,0001—15Not compared (before 2008)Stable
199936100,0000—15Not compared (before 2008)Stable
19981547,0001—15—Stable
199714100,0002—15—Not enough data

All GMC Sierra 2500 model years · Best and worst years by complaints

Frequently asked questions

What are the most common problems with the 2021 GMC Sierra 2500?

Owners of this 2021 GMC Sierra 2500 most often report headlights and turn signals that flicker or fail, and some link this to moisture in the lamp assembly. The issues reported most often: Headlights and turn signals flicker or fail; Sudden loss of power and transmission failure; Brake squeal, lock-up and parking brake faults.

How many NHTSA complaints does the 2021 GMC Sierra 2500 have?

NHTSA recorded 52 consumer complaints for the 2021 GMC Sierra 2500 as of Oct 27, 2026. Complaints are unverified consumer reports and may be duplicated or inaccurate.

What part of the 2021 GMC Sierra 2500 is reported most often?

Transmission and drivetrain is named most often, in 13 complaints (25% of the total), followed by exterior lighting with 9.

Has the 2021 GMC Sierra 2500 been recalled?

NHTSA lists 6 recall campaigns for this model year. To check a specific vehicle, enter its VIN at nhtsa.gov/recalls.

At what mileage are problems with the 2021 GMC Sierra 2500 reported?

Among the 15 complaints that include a mileage, the median is 53,000 miles and the middle half falls between 49,000 and 77,000 miles; 33% were filed for vehicles with under 50,000 miles.

About this data. Data from NHTSA (ODI) complaints, recalls, TSBs and investigations, updated Oct 27, 2026. Complaints are unverified consumer reports and may be duplicated or inaccurate.

Complaint counts come from NHTSA’s public complaint database; we count each complaint once. The source records for this vehicle are on nhtsa.gov. Scores and trends are our own summaries of that data, described in the methodology. This page is not legal, safety or repair advice: for a specific vehicle, check its VIN at nhtsa.gov/recalls and ask a qualified mechanic. See an error? Tell us.