Complaint volume
425 consumer-submitted complaints are matched to this model year. Treat the count as a research signal, then read the actual summaries for repeated symptoms.
Complaint records
2020 GMC Sierra Complaints
425 consumer-submitted complaints on record for the 2020 GMC Sierra, grouped by component category.
425 Total complaints
11 Crash reports
4 Fire reports
6 Injury reports
Complaint data reflects consumer-submitted reports. A complaint is not proof
of a defect, recall, or manufacturer fault. Enriched severity fields come
from official bulk records when the complaint can be matched by ODI number.
Buyer interpretation
How to use these complaints before buying
Complaint records are most useful when they turn into inspection points, seller questions, and comparison checks against nearby model years.
Pattern to inspect
The most common categories are engine, power train, electrical system. Use those categories as a test-drive checklist instead of judging the vehicle from the total count alone.
Severity flags
Enriched records include 11 crash reports, 4 fire reports, 6 injury reports, and 0 fatality reports. These fields come from complaint records and should be read in context.
Mileage clue
Mileage is available on 118 complaints, with an average reported failure mileage of 44,233 miles. Compare that with the mileage on the listing.
Questions to ask the seller
- Have you had any problems related to engine, power train, electrical system?
- Can I see recent maintenance and repair records?
- Has the vehicle ever been towed, involved in a crash, or repaired for the same issue twice?
- Can we also check the recall record for this 2020 GMC Sierra?
Used-car checklist
Use these complaints before the test drive.
Build a buyer checklist to turn these issues into questions and inspection points.
2020 GMC Sierra
Build buyer checklist Compare with other years Sends year, make, and model to pre-fill your checklist.
How severe are the 2020 GMC Sierra complaints?
11 Crash
4 Fire
6 Injury
0 Fatality
28 Towed
4 Medical attention
What are the most common 2020 GMC Sierra complaint categories?
ENGINE 125
POWER TRAIN 36
ELECTRICAL SYSTEM 21
POWER TRAIN,ENGINE 17
SERVICE BRAKES 16
STEERING 14
UNKNOWN OR OTHER 14
ENGINE AND ENGINE COOLING 9
SUSPENSION 9
ELECTRICAL SYSTEM,ENGINE 8
425 total complaints on record
Latest complaints
| Date | Component | Summary | Severity | Mileage |
|---|---|---|---|---|
| Oct 2024 | POWER TRAIN | Transmission failed at 75,000 miles, yes it is available for inspection. Truck went into limp mode on the highway and turned into a very dangerous situation, I was barely able to exit the highway. Yes the dealership Martys GMC in Kingston MA has confirmed that it is transmission failure. My vehicle has been sitting on the lot of Marty's GMC since September 13, 2024 waiting for a backordered part to fix the transmission at an estimated cost of $2,500. The warning check engine light followed by every single lamp on the dash appearing on [XXX] which is the date of transmission failure. After careful research of this issue I have found this is a widespread problem with this particular 10 speed GMC transmission in my 2020 GMC Sierra that I am still paying car payments on. I have rented a vehicle at my own cost for the past 4 plus weeks to get back and forth to work. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6) | Crash: No Fire: No | Unknown |
| Oct 2024 | ENGINE | The contact owns a 2020 GMC Sierra 1500. The contact stated that while the vehicle was parked and being driven, the vehicle was shaking violently. There were no warning lights illuminated. The contact stated that the failure was related to Technical Service Bulletin: 22-NA-186. The vehicle was taken to a local dealer, where it was diagnosed that the motor mount brackets needed to be replaced. The vehicle was repaired, but the failure persisted. The manufacturer was contacted, opened a case, and referred the contact to the NHTSA Hotline for assistance. The failure mileage was approximately 100,000. | Crash: No Fire: No | 100,000 |
| Oct 2024 | SERVICE BRAKES, HYDRAULIC | The contact owns a 2020 GMC Sierra 1500. The contact stated that the vehicle failed to start. The battery was replaced, and the failure was remedied. On another occasion, the contact stated that the brake percentage was low on the instrument panel and that the lights were becoming dim. The vehicle was taken to a dealer where the brakes were replaced; however, the computer failed to detect the repair; and the message "1 More Mile Left to Drive" was displayed. The contact also stated that two weeks later while driving 45 MPH, the brake pedal failed to respond and felt abnormally loose. The vehicle was driven over a concrete sidewalk to stop the vehicle. There was no crash, and no injuries were sustained. The vehicle was towed to the residence. The vehicle was not diagnosed or repaired. The manufacturer was notified of the failure and confirmed that the VIN was not under recall. The approximate failure mileage was 102,000. | Crash: No Fire: No Towed | 102,000 |
| Oct 2024 | FORWARD COLLISION AVOIDANCE | On two separate occasions, while traveling at highway speeds with the adaptive cruise control system on, my truck randomly started braking hard as if it was sensing a vehicle or obstacle in front of me but my lane was completely clear. The most recent time, I was almost rear ended because of this issue. | Crash: No Fire: No | Unknown |
| Sep 2024 | ELECTRICAL SYSTEM,UNKNOWN OR OTHER,SERVICE BRAKES | My truck 2020 gmc sierra 1500 AT4 denali is not working properly since July 2024. I took it to 2 different dealership to get a diagnostic and i finally ended doing the repairs for brake issues. I have been towed 6 or more times and almost experienced 2 car accidents since I drive the truck after the supposedly repairs where done but i ended stranded again with no brakes. The dealership has repair the truck 3 times but im still getting sevaral codes the fact that i had to pay out of pocket and have to deal with this and expose myself to danger and my family in driving a vehicle that is no safety condition its absurd. I call several times the recall GM hotline and i was told GMC 1500 are included in the recalls just not the AT4 and i have a family member with the same truck and same issues she ended up trading in the truck recently since she kept experiencing the same issues over and over again just like me. | Crash: No Fire: No | Unknown |
| Aug 2024 | ELECTRICAL SYSTEM,VEHICLE SPEED CONTROL,SERVICE BRAKES | My brakes failed 2 times. One time I almost got into a horrible wreck with my daughter in the truck. "Brake system failure" " max speed 43mph" I have not had any brake work or anything done. The dealer is trying to charge me to replace the whole brake system when [XXX] this says to reprogram. Still waiting on gmc to tell me if it's covered under warranty. From my own research this has been a major problem for hundreds of people if not more. I could have died because of a faulty brake system or a bad software update. I need help with this and so do the countless other 2020 gm owners. There is a recall on the 2019 for the exact problem but not the 2020s. GM safety recall N192268090 please advise INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6) | Crash: No Fire: No | Unknown |
| Aug 2024 | STEERING | Without warning power steering went out. Flashed code: service power steering; service esm and traction control light. After two restarts, went away like it never happened. I was backing a 24 ft trailer at the time of occurrence. There are numerous other people with the same problem in online forums. I cannot believe that there has not been a recall or even service bulletin regarding this problem. It is a MAJOR safety concern | Crash: No Fire: No | Unknown |
| Jul 2024 | POWER TRAIN | The AFM/DFM system in these trucks are making the engines and transmissions go out around 70k miles. The lifters fail right around the same time factory warranty runs out then your left with a 6 thousand dollar bill to have it fixed. I hope this becomes a recall because numerous people I talk to are getting rid of they're gmcs and chevys and going elsewhere. | Crash: No Fire: No | Unknown |
| Jun 2024 | POWER TRAIN | The transmission went at 67,000 miles and posed a safety issue when my husband was driving & suddenly couldn't drive above 1st gear. Vehicle is at the GM dealer and has been for weeks, but there have been so many issues with the transmissions of this year, make & model, that the transmissions are on back order and we are told it can be MONTHS before they get one in. The dealer already has another one that has been waiting for once since April. We know of others with this same issue on this make/model/yr, as well as engine issues, but yet there are NO recalls for this issue. The only warning that came on was when the issue occurred- no prior warning or indications. GM is involved but make no comment on why there isn't a recall for an obvious known issue. | Crash: No Fire: No | Unknown |
| May 2024 | SERVICE BRAKES, AIR,ELECTRICAL SYSTEM,ENGINE | The contact owns a 2020 GMC Sierra 1500. The contact stated while driving at various speeds, the vehicle was stuck in gear. While driving there was an abnormal burning odor coming from the vehicle. The vehicle failed to start on several occasions. There were sparks from the passenger's side front seat. Several unknown warning lights were illuminated. The vehicle was taken to the local dealer, where it was diagnosed with electrical, transmission module, wiring harness, air alternator cooler, and exhaust system failures. The vehicle was repaired; however, the failure recurred. Additionally, while driving at undisclosed speeds, there was a failure with the vault meter. The OnStar system provided an error with the antilock braking system. The manufacturer was contacted, but no assistance was provided. The failure mileage was approximately 44,000. | Crash: No Fire: No | 44,000 |
| May 2024 | ELECTRICAL SYSTEM,ENGINE,FUEL/PROPULSION SYSTEM | My wiring harness which affects all systems. I was on the Interstate when out of nowhere any and all warning lights came on. The power was cut and rapidly slowed down. I also pulled into traffic and the truck just lost power. The problem was confirmed by dealership. The vehicle was inspected by dealership and wiring harness was the issue. The issues appeared out of nowhere. All the warnings lights came on at once. There has been numerous issues with this part and it’s even recognized by just. | Crash: No Fire: No | Unknown |
| May 2024 | POWER TRAIN | Has happened three times. 1st and 2nd time driving down road towing trailer, rear wheels locked up for 12-15’ while driving 50-55mph. I had thought it was my trailer axel. Happened twice within 6 miles. 3rd time was 1 month later. Rear Wheels locked up driving on interstate at 70-75 mph. I estimate that i traveled 1,800 miles between the 2nd and third incident. Vehicle is at the dealership getting inspected for repairs No warning lamps before, almost every warning light came on after incident If this happened on a wet, ice, snow or dirt road this could have caused a serious accident. It would also be bad in a curve. Dealer took for road test but did not have any luck recreating the issue. They checked the differential oil And it didn't have any heavy metals. They are going to take the differential apart to inspect it to verify. They checked my battery and said it needed to be replaced. Also a wheel speed sensor needed to be replaced. | Crash: No Fire: No | Unknown |
| May 2024 | ELECTRICAL SYSTEM,STRUCTURE,UNKNOWN OR OTHER | The rear sliding window leaks water inside the cab every time it rains. With water getting into the cab the issue of mold has begun and that could be a serious factor to any children or adults that ride inside the cab of the truck. There is also rust issues that are notable under the rear seats of the vehicle. Water inside the cab can also interact negatively with any electrical components of the vehicle. I tried to get ahold of the dealer and they always say they don't have time to get my truck in. I have read that this has happened to other vehicles that are the same year and model and they just fix it with caulk which does not seem appropriate for a almost new vehicle. The vehicle has not been inspected. There were no warning lamps prior to this issue. A possible symptom was that my back up camera stopped working for a day right after a rain. | Crash: No Fire: No | Unknown |
| Apr 2024 | AIR BAGS | The contact owns a 2020 GMC Sierra. The contact proceeded through the intersection when a vehicle crashed into the contact's driver's side door and wheel at unknown speeds. The contact stated that the other vehicle crashed into two vehicles, then crashed into the contact's vehicle and stopped. The contact stated that the police report stated that the vehicle that crashed into the contact was constantly moving at the posted limit of 50 MPH. The air bags did not deploy. The contact was treated for a left shoulder sprain and swollen right hand, however, it was unknown if other passengers sustained injuries. A police report was filed. The vehicle was towed to a body shop but the vehicle was not repaired. The failure mileage was approximately 34,800. | Crash: Yes Fire: No Injuries: 1 Towed Medical attention | 34,800 |
| Apr 2024 | STRUCTURE,UNKNOWN OR OTHER | Rear window leak causing whole inside back to get soaked. Have paid hundreds of dollars to have sealed didn’t work. New window didn’t work it still leaks. It’s going to cause interior to mold and body to rust. Dealership and glass business both say it’s body issue and they have seen many GMC and Chevrolets with this issue. Google show 1000s with same problem. | Crash: No Fire: No | Unknown |
| Apr 2024 | STRUCTURE | GM refuses to fix a known design flaw in the back sliding glass frame on 2020_24 gmc sierra trucks. This issue will generate toxic mold as large quantities of water enter the cabin and can be extremely harmful for certain individuals allergic to mold. GM knows about this issue and tried to secretly advise techs via TSB 18-na-383 to apply sealant on the frame and if customer returns to replace frame. However they do not want to do this outside the 3 year warranty. The back glass on a truck is not a serviceable item. | Crash: No Fire: No | Unknown |
| Mar 2024 | FUEL/PROPULSION SYSTEM | 13540028 Fuel Pump Power Control Module Part failed leaving me stranded and had to get a tow. When the failure occurred, vehicle would not crank and there was no forewarning. It worked and then it didn't. The part is on notional backorder and there seems to be a lot of vehicles out there with the same issue and that just with the mechanics\service departments I've contacted that have had the part on backorder for months. So the fail rate seems high and I'm sure others got stuck in a lot worse situation than me. Then GMC continues to produce vehicles with a newer similar part while not producing the same part for like new vehicles. Which will probably only compound the backorder issue when the newer vehicles eventually have the same issue. | Crash: No Fire: No | Unknown |
| Mar 2024 | ENGINE AND ENGINE COOLING | See attached document for complaint | Crash: No Fire: No | Unknown |
| Mar 2024 | ENGINE | Vehicle has excessive oil consumption. Within 5000k oil change interval, no oil on dip stick around 3000k miles. | Crash: No Fire: No | Unknown |
| Mar 2024 | ELECTRICAL SYSTEM,VEHICLE SPEED CONTROL,VISIBILITY/WIPER | Back window frame crack led to water intrusion which flooded electric module controlling speedometer and adaptive settings. Extremely unsafe driving with faulty electrical components unknown to me. Insurance and Dealership told me this is a common GMC occurrence. Cost is near $10,000 to make truck drivable. | Crash: No Fire: No | Unknown |
| Feb 2024 | FUEL/PROPULSION SYSTEM | Fuel Pump Drive Control Module (Part No. 13540028). This item is a recall on several other vehicles, but not identified on my year/model. On 4 separate occasions over a 3-4 week period, the engine starting running very rough lost power and stalled while traveling down the road (highways, interstate, and a side street). I was finally able to pull a fault code and research the history of this code and this part on several other GMC/Chevy modeled vehicles. The dealer advised I was lucky to find the part because most of them are on backorder due to the recall on other vehicles. The one I got was for a recall, but the customer hadn't returned in time so they sold it to me. I had a repair garage replace the component on Jan 13, 2024, and haven't had any repeat issues. The check engine light did come on each time with a P129F code. It would reset after the vehicle stalled and was powered off for 10-15 minutes and the symptoms would go away. Each time left me lucky to get my vehicle over several lanes and off the side of the road. The date below was the last time it happened. The first time it happened was on Dec 6th and the vehicle started back up in just a minute or two. I still have the old part if it needs to be sent and evaluated to compare with other recalls on the item in other vehicles. | Crash: No Fire: No | Unknown |
| Feb 2024 | STRUCTURE | Rear Sliding Glass window frame has cracked and allows water to enter the cab of the vehicle. Yes this is available for inspection. The water entering the cab of the vehicle can create mold from moisture build up if left untreated. I was able to have the dealer service center confirm the issue noted in [XXX] but they were unable to repair it as it is outside of warranty. I was able to have an independent 3rd party glass company confirm that it was indeed a manufacturers defect with a cracked housing and not an issue with sealant around the glass itself. No warning lamps or other indications other than water in the back seat of the vehicle. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6) | Crash: No Fire: No | Unknown |
| Feb 2024 | ENGINE | 1. Valve Lifter Failure 2. While entering the [XXX] freeway and trying to merge into traffic the engine lost power and I had to swerve and brake to avoid an adjacent vehicle, and freeway traffic had to avoid my slowing down to pull over. 3.Yes, Van GMC in Scottsdale, confirmed lifter failure. 4. Yes, GMC Dealership 5. Absolutely no warning given INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6) | Crash: No Fire: No | Unknown |
| Feb 2024 | STRUCTURE,UNKNOWN OR OTHER | Rear Window Leaks due to failed sealing at the factory. If not fixed will ruin interior components and possibly rust. Yes No No | Crash: No Fire: No | Unknown |
| Feb 2024 | VISIBILITY | The contact owns a 2020 GMC Sierra 1500. The contact stated while detailing the rear interior of the vehicle, the contact discovered water surrounding the rear windshield casing and the water was leaking into the rear seating. Additionally, the rear carpet was soiled with water. The contact used towels while attempting to soak up the water. The vehicle was taken to the dealer where it was diagnosed that the failure was due to the failed rear windshield glass fasteners. The contact was informed that the failure had damaged the rear carpet, padding, and the rear seat. In addition, the contact was informed that the carpet and padding needed to be replaced due to mold build up. The contact was informed that the vehicle was out of warranty coverage. The vehicle was not repaired. The manufacturer was made aware of the failure but provided no assistance. The failure mileage was approximately 31,000. | Crash: No Fire: No | 31,000 |