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Active NHTSA advisory: park outside and away from structures until repaired. Check your VIN at nhtsa.gov/recalls and see the recall details below.
GMC · Pickup truck

2021 GMC Sierra 3500HD

Heavy-duty pickup
0 EPA-rated configurations
Data refreshed 2026-10-26
F
Safety Signal
57 / 100 from the NHTSA recall record
Recalls2 critical 5
Complaintsnone reporting a crash, fire or injury 20
Crash ratingnot rated by NHTSA —
20262025202420232022202120202019201820172016

The 2021 GMC Sierra 3500HD is a pickup truck; vehicles over 8,500 lb GVWR are not certified for fuel economy by the EPA, so this page is built from NHTSA's recall, complaint and investigation records. NHTSA lists 5 recall campaigns for this model year, 2 rated critical, which gives it a Safety Signal grade of F. Owners have filed 20 complaints, most often about the power train.

GMC Sierra — photograph via Wikimedia Commons
GMC Sierra · Photo: Ethan Llamas · CC BY-SA 4.0 · Wikimedia Commons

Specs & fuel economy

Source: EPA fueleconomy.gov

No EPA fuel-economy record: the EPA does not certify vehicles over 8,500 lb GVWR. Recall, complaint and investigation data below come from NHTSA.

Specifications filed with NHTSA

Source: NHTSA vPIC

Dimensions Exterior

Body styleIncomplete - Chassis Cab (Double Cab)
Doors4
GVWR classClass 3: 10,001 - 14,000 lb (4,536 - 6,350 kg)

Engine Basics

Cylinders8
Displacement6.6 L
Engine configurationV-Shaped

Fuel Economy

FuelGasoline

Transmission

Drivetrain4WD/4-Wheel Drive/4x4

Filed by the manufacturer with NHTSA under the federal vehicle-identification rule and decoded from the VIN pattern — not a manufacturer press kit, so it describes the configurations we could identify rather than every trim (seen: AT4, Fleet/Base, SLE, SLT). Figures for the trim you are looking at may differ.

Dimensions & weight

Source: Transport Canada
Length235.4–266.1 in
Width (body, without mirrors)81.9 in
Height79.9–80.7 in
Wheelbase141.7–172.0 in
Track, front67.3 in
Track, rear68.1 in
Curb weight6,338–7,172 lb
Weight distribution, front/rear57/43

Measured by Transport Canada for its Canadian Vehicle Specifications database, which covers the North American versions of each model — here 14 configurations: Crew Cab L/Box Drw 2WD, Crew Cab L/Box Drw 4X4, Crew Cab L/Box Srw 2WD, Crew Cab L/Box Srw 4X4, Crew Cab M/Box 2WD, Crew Cab M/Box 4X4 …. Where a range is shown, those versions differ. Width is the body without mirrors, which is why it can read narrower than a brochure figure. Before we used it we checked it against the US manufacturer press kits we hold (27 Sep 2026): wheelbase agreed within 1% on every vehicle we could compare, length on 98%, and the curb weight fell inside the manufacturer's range on 96%. Source dataset. Contains information licensed under the Open Government Licence – Canada. Licence.

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Factory warranty running out?

The 2021 GMC Sierra 3500HD is in the years where transmission, electronics and drivetrain repairs land on the owner. What an extended plan does and does not cover is worth reading before a dealer quotes you one.

What to check before you buy →

Affiliate disclosure: some links on this page are affiliate links. If you request a quote or buy through them we may earn a commission at no extra cost to you. Nothing on this page changes because of it.

Recalls (5)

Source: NHTSA recall database
!critical

Power Train

N242454440
463,295 vehicles 78% reported repaired
Problem 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 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.
NHTSA campaign 24V797000 reported Oct 24, 2024 General Motors, LLC the full filing, and every vehicle covered →
▲high

Latches/Locks/Linkages

N232426400
570,434 vehicles 74% reported repaired
Problem 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 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.
NHTSA campaign 24V060000 reported Feb 1, 2024 General Motors, LLC the full filing, and every vehicle covered →
!critical

Service Brakes, Hydraulic

N212349181
Park outside 3,241 vehicles 96% reported repaired
Problem 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 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.
NHTSA campaign 21V758000 reported Sep 29, 2021 General Motors, LLC the full filing, and every vehicle covered →
▲high

Seat Belts

N202322230
470 vehicles 94% reported repaired
Problem 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 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.
Filed with NHTSAOwner letter PDF
NHTSA campaign 20V811000 reported Dec 23, 2020 General Motors, LLC the full filing, and every vehicle covered →
▲high

Seat Belts

N202314670
624,216 vehicles 90% reported repaired
Problem 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 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.
Filed with NHTSAOwner letter PDF
NHTSA campaign 20V792000 reported Dec 17, 2020 General Motors, LLC the full filing, and every vehicle covered →

These are vehicle campaigns — the ones the automaker filed against this model. NHTSA also records equipment recalls, filed by a parts maker against a component (a tyre, a child seat, an aftermarket part), and those are not listed here or counted above. nhtsa.gov/recalls shows both for a VIN.

NHTSA defect investigations

Air Bags:Srs Malfunction Warning Lamp/Light — Air Bag Malfunction closed

On April 9, 2021, the Office of Defects Investigations (ODI) opened PE21-010 to investigate instances of air bag malfunction indicator light (MIL) illumination and potential for frontal air bag non-deployment in several vehicles manufactured by General Motors (GM). The vehicles included model year (MY) 2020 through 2021 CT4 and CT5 passenger cars, Sierra and Silverado trucks (1500/2500/3500 models), XT4 and MY 2021 Escalade, Suburban, Tahoe, Yukon SUVs. Technical Service Bulletin (TSB) 21-NA-005, issued in March 2021, addresses air bag MIL illumination with diagnostic trouble codes (DTCs) B0001-1B or B0012-0D. It cites rust particles in the connection terminal interface of the driver air bag

Opened Apr 9, 2021 · closed Aug 24, 2023 · action PE21010 · the investigation’s page →

Whether any of this applies to one specific Sierra 3500HD

A campaign covers a build range, not a model year, so two identical-looking cars from 2021 can differ. Both of these check a VIN against the manufacturer’s own list, free, in about ten seconds. GMC publishes its own lookup because federal rule 49 CFR 573.15 requires it to, and to keep it current to within seven days.

Hear about a recall before the letter does

The manufacturer’s letter is the last step of a recall: it has up to 60 days after filing to mail owners, at the address on the registration. We email you the day NHTSA posts a recall on the 2021 GMC Sierra 3500HD, with what to do next. Nothing else, ever — no newsletter, no marketing, one-click unsubscribe in every message.

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Parts & accessories for the 2021 GMC Sierra 3500HD

Search by fitment on eBay Motors — OEM take-offs, aftermarket, and the trim pieces dealers no longer stock. The listing and the price are the seller's.

Find parts for this Sierra 3500HD →

Owner complaints

Source: NHTSA complaint database
20complaints filed

0 involved a crash · 0 a fire · 0 injuries · 0 deaths reported

10 per 10,000 built · GMC reported 19,358 Sierra 3500HD built (its Early Warning production report to NHTSA)

Filed per year: 2021: 2 · 2022: 5 · 2023: 1 · 2024: 3 · 2025: 8 · 2026: 1

Most-cited components

Power Train 7
Service Brakes 5
Electrical System 4
Engine 3
Unspecified 3
Fuel/Propulsion System 2

In owners' own words

Filed with NHTSA by the people who own these cars, one per problem area. Quoted as written, with anything identifying removed.

The contact filed the complaint on behalf of the owner of a 2021 GMC Sierra 3500. The contact stated that while the vehicle owner was driving at an undisclosed speed, the driver noticed that the rear wheels were attempting to lockup. The contact stated that the failure was noticeable while driving forward and while reversing.
Service Brakes at 140,606 miles Jun 12, 2026 NHTSA owner report · ODI 11743698
During takeoff the transmission acted as if it was in neutral while I was crossing traffic luckily, the semi truck that was coming towards me was able to stop. I had the vehicle towed to a shop. After the vehicle was towed to the shop the transmission acted normal when the mechanic searched the VIN number.
Power Train Nov 24, 2025 NHTSA owner report · ODI 11701315
The contact owns a 2021 GMC Sierra 3500. The contact stated that while his wife had the vehicle idling with the rear defroster activated, shortly afterwards, she observed smoke coming from the plastic on the rear sliding window.
Electrical System at 26,000 miles Sep 8, 2025 NHTSA owner report · ODI 11685740
The contact owns a 2021 GMC Sierra 3500. The contact stated that while reversing, the back over prevention camera screen displayed an image of the ground. The contact stated that the image was approximately ten feet behind the vehicle. The vehicle was taken to the dealer; however, the failure was not duplicated.
Back Over Prevention at 70,000 miles Aug 14, 2025 NHTSA owner report · ODI 11680762
Multiple instances of diesel engine emissions system parts and software failure. While driving, towing or not, the DIC would randomly display a message that the DEF level is low and reduced speed will occur in x-amount of miles and that mileage would then begin a visible countdown on the DIC, sometimes much more quickly than the actual…
Engine Nov 1, 2024 NHTSA owner report · ODI 11623109
The right rear tire (Goodyear Wrangler 275/65R20) separated and blew out on the highway, the truck was very difficult to control however it was safely stopped and there were no injuries. There was no observed warning prior to the blow out. The tire separation caused damage to the right rear quarter panel.
Tires May 24, 2023 NHTSA owner report · ODI 11523697

Complaint counts are raw owner reports to NHTSA, not verified defects, and scale with how many were sold. Use them to spot patterns, not to rank.

Reported by GMC itself: 4 death-or-injury claims on this model year in its quarterly Early Warning reports to NHTSA (49 CFR 579.21): 8 injured, as claimed, not verified — about 21 per 100,000 built. Every Sierra 3500HD model year, by year and system → Dated and by system, they are exhibit F of the defect dossier.

Crash ratings

Source: NHTSA NCAP

NHTSA has not published 5-Star crash ratings for this model year.

Service bulletins & campaigns

Source: NHTSA manufacturer communications
Extended coverage on file 4 filings by the manufacturer with NHTSA naming this model year

The term and the vehicles it covers are the manufacturer’s, as NHTSA’s summary of each filing states them; a dealer checks one particular car by its VIN. Every GM warranty extension (33) → · Every warranty extension on file, all makes →

Communicationsfiled with NHTSA 841
Most recentmanufacturer date 2026-09-26
Kindsas classified by NHTSA 833 service bulletins, 6 service campaigns, 1 warranty extension

Most often about: Engine, Electrical System, Equipment, Unknown Or Other, Power Train.

  • PIT5698F Service bulletin
    2026-09-26 · Unknown Or Other
  • This PI provides Diagnostics tips on how the LIN bus works and how to diagnosis it.
  • PIP4902W Service bulletin
    2026-09-04 · Unknown Or Other
  • This preliminary information advises a dealer on how to email GDS2 session logs into Technical Assistance.
  • PIP6127A Service bulletin
    2026-08-27 · Unknown Or Other
  • This document assists GM dealer technicians with diagnosing torque converter concerns to ensure torque converter replacement is necessary. The torque converter part number will be placed on order restriction, and the technician will be asked to follow 25-NA-148 before requesting a part through PQC.
  • PIC6551C Service bulletin
    2026-08-20 · Unknown Or Other
  • This Preliminary information communicates to dealer to perform a MEC reset for wireless projection issues
  • PIT6031B Service bulletin
    2026-08-07 · Unknown Or Other
  • This Preliminary information communicates an issue where an aftermarket autostop device or rear taillights is causing a dead battery.
  • PIT5680B Service bulletin
    2026-07-23 · Unknown Or Other
  • This PI provides information to repair the door water deflector which is not sealed properly allows water into the door jam/sill area.
  • PIT5099J Service bulletin
    2026-07-21 · Unknown Or Other
  • PI to help diagnose A/C concern
  • PIT5509N Service bulletin
    2026-07-21 · Unknown Or Other
  • This PI provides diagnostic tips for diagnosing electric trailer brakes issues.

A service bulletin is the manufacturer telling its dealers how to diagnose or repair a known condition. It is not a recall, not a finding that the vehicle is defective, and the work is not automatically free — though a bulletin is often what a dealer works from when you describe a symptom, so quoting the document number can save a diagnosis. The count is every communication filed; the list shows the most recent, one entry per campaign, because a single campaign is usually filed as several documents on the same day. The summaries are NHTSA's; the full documents come from the manufacturer.

Diagnostic trouble codes on file

Source: NHTSA manufacturer communications and complaints

Codes documented against this model year in the federal record. A code appearing here does not mean this vehicle will set it — it means the code is part of this nameplate-year's documented history.

CodeWhat it meansMost often filed underWhere it appears
P12A6
P12A6 on GMC →
Manufacturer-defined — the meaning is set by the automaker, not the standard.Engine7 bulletins
P0442
P0442 on GMC →
A small leak in the evaporative emissions system.Engine · Gas cap →6 bulletins
P0455
P0455 on GMC →
A large leak in the evaporative emissions system — often a fuel cap left off.Engine · Gas cap →6 bulletins
P0747
P0747 on GMC →
Manufacturer-defined — the meaning is set by the automaker, not the standard.Power Train6 bulletins
P0446
P0446 on GMC →
A fault in the evaporative vent control circuit.Engine · EVAP vent valve →5 bulletins
P0449
P0449 on GMC →
A fault in the evaporative vent valve or solenoid circuit.Engine · EVAP vent valve →5 bulletins
P062B
P062B on GMC →
Manufacturer-defined — the meaning is set by the automaker, not the standard.Unknown Or Other5 bulletins
P2463
P2463 on GMC →
Soot has built up in the diesel particulate filter beyond the allowed limit.Engine4 bulletins
B2B0D
B2B0D on GMC →
Manufacturer-defined — the meaning is set by the automaker, not the standard.Electrical System · Battery →3 bulletins
B2B0E
B2B0E on GMC →
Manufacturer-defined — the meaning is set by the automaker, not the standard.Electrical System · Battery →3 bulletins
P0300
P0300 on GMC →
Misfire detected, but not isolated to one cylinder.Engine · Ignition coils →3 bulletins
P2714
P2714 on GMC →
Manufacturer-defined — the meaning is set by the automaker, not the standard.Unknown Or Other3 bulletins

Generic codes (the second character is 0 or 2) mean the same thing on every vehicle sold in the United States. Manufacturer-specific codes (1 or 3) mean whatever the automaker assigned, and no honest source can define them for you — which is why the ones here carry the evidence instead of a definition. A code is a link when enough separate federal documents name it across the catalogue to be worth a page of its own; the rest are listed here, where the vehicle is the context that makes them mean something.

Affiliate disclosure: some links on this page are affiliate links. If you request a quote or buy through them we may earn a commission at no extra cost to you. Nothing on this page changes because of it.

Common questions about the 2021 Sierra 3500HD

Source: EPA, NHTSA and manufacturer press kits

Does the 2021 GMC Sierra 3500HD have any recalls?

NHTSA has posted 5 recall campaigns for the 2021 GMC Sierra 3500HD, 2 of them rated critical. The most serious on file is 24V797000, covering Power Train. There is an active park outside advisory — act on it before driving. Check your own VIN at nhtsa.gov/recalls; a recall applies to specific build ranges, not every car.

How safe is the 2021 GMC Sierra 3500HD?

NHTSA has not published a crash-test rating for the 2021 GMC Sierra 3500HD yet. On the recall record WhichTrim grades it F (57/100), which measures open and severe recalls rather than crash protection.

What are the dimensions of the 2021 GMC Sierra 3500HD?

Transport Canada measured it at 235.4–266.1 in long, 81.9 in wide (body, without mirrors), 79.9–80.7 in tall, on a 141.7–172.0 in wheelbase. Curb weight: 6,338–7,172 lb depending on configuration. Those are its measurements of the North American versions; every figure is in the table above.

What do owners complain about on the 2021 GMC Sierra 3500HD?

Owners have filed 20 complaints with NHTSA about the 2021 GMC Sierra 3500HD, most often about power train, service brakes, electrical system. Complaints are unverified owner reports, so treat the pattern as a signal and the individual report as an anecdote.

Are there service bulletins for the 2021 GMC Sierra 3500HD?

The manufacturer has filed 841 service bulletins and related communications with NHTSA for the 2021 GMC Sierra 3500HD, most often covering engine, electrical system, equipment. The most recent is dated 2026-09-26. A bulletin is not a recall: it is the repair procedure a manufacturer sends its dealers for a condition it knows about, and the work is not automatically paid for. It is still worth knowing — if the symptom matches, quoting the bulletin number at the service desk can save a diagnosis. The document numbers and summaries are listed above.

What we hold, and what an empty row means

Paid vehicle-history reports will not tell you the difference between “nothing happened to this car” and “we never received that record” — both of the big two say as much in their own help pages. Most of what is on this page comes from complete federal registers, so we can tell you which is which, row by row.

DataHeldSourceWhat it covers — or what empty means
Fuel economy & configurationsnoneEPA certification recordsThe EPA does not certify vehicles rated over 8,500 lb GVWR, so heavy-duty nameplates have no entry at all.
Emission certificatesnoneEPA emission certificatesThe EPA published no certificate we could match to a configuration on this page.
Recalls5NHTSA recall campaignsA complete federal register: every campaign covering this model year, with severity and advisory flags.
Owner complaints20NHTSA complaint databaseAlso complete, but unverified: these are reports owners filed, not findings. Counts scale with how many were sold.
Crash ratingsnoneNHTSA NCAPNHTSA has not tested this model year. Cars are selected for testing, so untested is not unsafe.
Service bulletins841NHTSA manufacturer communicationsEverything the manufacturer told its dealers about a defect or malfunction, short of a recall.
Investigations1NHTSA Office of Defects InvestigationOpen and closed defect investigations, with the agency's own narrative.
Driver-assist crash reportsnoneNHTSA Standing General Order 2021-01No report has been filed. Only entities named in the order report, and only crashes they hear of — so this is also what an unequipped car, or a manufacturer without telematics, looks like.
Specifications filed with NHTSA8 fieldsNHTSA vPIC, decoded from VIN patternsWhat the manufacturer filed under the federal VIN rule — a configuration, not the full trim ladder.
Measured dimensions7 fieldsTransport Canada, Canadian Vehicle SpecificationsLength, width, height, wheelbase, track and curb weight, measured on the North American versions.
Trims, pricing & equipmentnoneManufacturer press kitWe have not transcribed a press kit for this model year yet. This is our gap, not the manufacturer's — the one row here where an empty cell means we are behind.

Rebuilt nightly; this page was generated 2026-10-26. Every figure above is traceable to the source named beside it, and the JSON for this page carries the same values with their identifiers.

Sources & method

Safety Signal starts every model-year at 100 and subtracts points per open NHTSA recall campaign by severity: critical 15 (fire risk, park-outside or do-not-drive advisories), high 8 (brakes, steering, airbags, loss of drive power, structure, battery), moderate 6, minor 3 (software, labels, lighting fixed by an update). The most serious recall counts in full and each further one counts 85% of the one before, because a vehicle sold in millions is recalled more often than a rare one without being more dangerous — and because a flat subtraction bottomed the scale out, scoring a vehicle with 22 recalls within a point of one with six. A ≥ 90, B ≥ 80, C ≥ 70, D ≥ 60, otherwise F. Read it as what it counts: recall campaigns on the federal record, weighted by severity. The damping reduces the sales bias by roughly 40% but does not remove it: like our complaint counts, this is not normalized by how many were sold, so a best-seller still scores somewhat worse than an obscure model with the same real risk. NHTSA crash ratings, do-not-drive and park-outside advisories, and the crash, fire, injury and death counts in owner complaints are reported separately on every page and never blended into the letter — a vehicle can hold five stars and a poor letter at once, and where that happens we say so rather than leave you to notice. Because the scale subtracts from a clean sheet, a model year too new to have been recalled, complained about or bulletined scores full marks on an empty record; we label those grades provisional rather than present them as earned.

EPA figures come from fueleconomy.gov vehicle records. Recalls, complaints, investigations and crash ratings come from NHTSA's public flat files, refreshed nightly.

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