2021 GMC Sierra 3500 problems & reliability
20 owner complaints filed with NHTSA for the 2021 GMC Sierra 3500, alongside 5 safety recall campaigns. Last verified Aug 7, 2026. Complaints are unverified reports submitted by owners to the federal Office of Defects Investigation.
Each complaint is counted once (by NHTSA case number), even when it names several vehicles.
Most reported problems
| Component | Complaints | Share |
|---|---|---|
| Power Train | 7 | 35% |
| Service Brakes | 5 | 25% |
| Electrical System | 4 | 20% |
| Engine | 3 | 15% |
| Unknown OR Other | 3 | 15% |
| Fuel/propulsion System | 2 | 10% |
| Back Over Prevention | 1 | 5% |
| Structure | 1 | 5% |
| Tires | 1 | 5% |
| Visibility | 1 | 5% |
Component groups as classified by NHTSA. A complaint can name more than one component, so shares may sum to more than 100%.
Complaints by incident year
What owners report
“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…”
Service Brakes · filed Jun 12, 2026
“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. There was a…”
Power Train · filed Nov 24, 2025
“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. After a visual inspection, the contact's wife observed that the plastic was melting…”
Electrical System · filed Sep 8, 2025
Verbatim excerpts from complaints filed with NHTSA. Reports are not independently verified.
Federal defect investigations
- Air Bag Malfunction
Preliminary Evaluation PE21010 · opened Apr 9, 2021 · closed Aug 24, 2023
Technical service bulletins
836 manufacturer communications (TSBs, service campaigns, warranty extensions) are on file with NHTSA for the 2021 GMC Sierra 3500. The 10 most recent:
This PI provides information to repair the door water deflector which is not sealed properly allows water into the door jam/sill area.
PIT5680B · Service Bulletin/Repair Instructions · issued Jul 23, 2026
PI to help diagnose A/C concern
PIT5099J · Service Bulletin/Repair Instructions · issued Jul 21, 2026
This PI provides diagnostic tips for diagnosing electric trailer brakes issues.
PIT5509N · Service Bulletin/Repair Instructions · issued Jul 21, 2026
This PI was created to help avoid unnecessary front camera module replacements
PIT6473F · Service Bulletin/Repair Instructions · issued Jul 17, 2026
The purpose of this PI is to inform dealer technicians of a normal cab pressure relief valve noise to avoid unnecessary part replacement
PIT6532 · Service Bulletin/Repair Instructions · issued Jul 6, 2026
This Preliminary information communicates information on a hydraulic rush type noise from the power steering gear. This noise is a characteristic of the new Active Hydraulic Assist System RPO NV8 and no repairs should…
PIT5544J · Service Bulletin/Repair Instructions · issued Jun 24, 2026
This Preliminary information communicates an issue with an OTA pending message still displayed after an OTA event and how to reset/clear the message.
PIT5966F · Service Bulletin/Repair Instructions · issued Jun 23, 2026
This PI provides diagnostic steps for dealer technicians to verify the condition and ensure that part replacement is necessary
PIT6523 · Service Bulletin/Repair Instructions · issued Jun 10, 2026
This Preliminary information communicates an issues with the HVAC making a hum buzz noise when the blower is set to a higher speed. Engineering is working on a new HVAC door seal material to correct the noise.
PIT6132E · Service Bulletin/Repair Instructions · issued Jun 9, 2026
This PI provides diagnostic tips for diagnosing electric trailer brakes issues.
PIT5509M · Service Bulletin/Repair Instructions · issued May 14, 2026
TSBs are repair guidance manufacturers send to dealers — they are not recalls and repairs are not automatically free. Full documents are available on NHTSA’s site.
Safety recalls
The 2021 GMC Sierra 3500 has 5 NHTSA recall campaigns — recall repairs are free at franchised dealers regardless of the vehicle’s age.
Check whether your specific vehicle is affected
Recall campaigns often cover only certain VIN ranges. Enter your VIN on the official NHTSA site to confirm whether your vehicle is included and whether the repair is still open.
Check VIN on NHTSA →Buying a used 2021 GMC Sierra 3500?
- · Decode the seller’s VIN with our free VIN decoder to confirm the exact year, engine and trim.
- · Check for unrepaired recalls by VIN on NHTSA’s official lookup — recall repairs are free.