GMC Sierra Complaints (2020)

626 consumer complaints on file.

#11767451September 28, 2026
POWER TRAIN, VEHICLE SPEED CONTROL
The vehicle in questions was purchased with less than 5 miles in year 2020. This vehicle was dropped off at MAC HAIK CHEVOLET MADISON MS on September 25, 2026. I was advised on September 28, 2026, that the vehicle was test driven with the scan tool connected, Graph Torque converter slip, found over 100 RPM slip when torque converter engaged and causing shutter at highway speeds, also felt 1-2 and 2-1 harsh downshift, check fluid condition was black and smelled burnt, replace transmission assembly, flush cooler, program transmission control module and perform clutch fast learn. Estimated cost of $8k
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11767573September 28, 2026
ENGINE, ELECTRICAL SYSTEM
6 months after owning it the lifters went bad got them Fixed then they immediately went bad again also bent rods then a day after getting that fixed again the oil pump went bad it was issue after issue
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11766667September 24, 2026
POWER TRAIN
A dealer "fixed" the P20EE code on this date, then the code came back a week later. Same dealer said they don't have qualified diesel technician, took vehicle to a 2nd dealer 9/22/2025, unable to determine cause of code. On 6/18/2026 same P20EE code came on again, took to dealer, dealer able to perform repairs on 7/30/2026 after ordering the correct parts. No on 9/23/2026 P20EE code is back.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11766668September 24, 2026
ENGINE
While slowly accelerating from a stop, with 4 family members in the truck, the engine began to run rough for about 1-2 seconds then multiple notifications flashed across the dashboard (Check Engine, Steering Assist is Reduced-Drive with Care, Service ESC, and Service Parking Brake). The road we were on was steep and twisty and did not have room to pull over which put us in an unsafe position with compromised steering and no shoulder. We made it 2 miles home but there was smoke coming from the exhaust and the engine ran very rough. Truck was towed to my mechanic. Mechanic confirmed issue. Diagnosis was misfire in #5 cylinder, confirmed initial compression upon startup (1 second) then compression loss and cylinder full of oil due to failed lifter. No previous issues prior to failure.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11765481September 19, 2026
ENGINE, FUEL/PROPULSION SYSTEM, UNKNOWN OR OTHER
Vehicle: 2020 GMC Sierra 1500 SLT VIN: 3GTU9DEL5LG340438 Engine: 6.2L V8, RPO L87 Mileage: approximately 129,854 miles My 2020 GMC Sierra 1500 equipped with the L87 6.2L V8 experienced an engine failure and has been diagnosed as needing an engine replacement. I am reporting this because my vehicle is equipped with the same L87 6.2L engine currently being investigated by NHTSA under Engineering Analysis EA25007 for engine failures occurring outside the scope of Recall 25V-274. My model year is not currently included in Recall 25V-274. However, EA25007 specifically addresses L87 engine failures occurring outside the existing recall population, including 2019–2024 GMC Sierra 1500 vehicles. GM also issued Preliminary Information bulletin PIP5900, “Diagnostic Tips for Seized Engine or Engine Noise,” applicable to 2019–2023 GMC Sierra vehicles equipped with the 6.2L L87 engine, which identifies possible crankshaft bearing failure. I am requesting that this engine failure be documented as part of NHTSA's ongoing investigation of L87 engine failures outside Recall 25V-274.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11765548September 19, 2026
VEHICLE SPEED CONTROL, POWER TRAIN, FORWARD COLLISION AVOIDANCE: AUTOMATIC EMERGENCY BRAKING
While driving vehicle flashed engine power reduction signal and then the emergency brake automatic feature came on abruptly. Fortunately, I had been able to slow down after the reduced power, but if I wouldn't have quickly reacted to that, I think the emergency brake system would have caused a safety issue. Now. The vehicle is incapacitated. There were two recalls that describe this exact situation on the same year and model of truck, but my VIN number did not fall. Under that recall. The recall was for the sensor and then the second recall was because the first recall didn't correctly fix it. But the details of the faulty sensor are exactly what happened to my truck. So it sounds to me like they had more problems than just the recall that they acknowledged but they have not expanded it. My quest is to have them expand the recall to all of the vehicles that had the same problem.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11764362September 15, 2026
POWER TRAIN, ENGINE, ELECTRICAL SYSTEM
5/5/25 woke up back seat entire truck flooring soaking wet back glass cracked. 4/8/25 transmission went out 117,000 miles 7/3/25 exhaust leak and placed nox 1. 7/8/25 127551 mileage exhaust leak replace gaskets, belt , tensioner, and pulley, 6/8/2025 3 knock sensors replaced and replaced intake manifold.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11764385September 15, 2026
ENGINE
Timing in engine is going out at 150,000 miles
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11764134September 14, 2026
ENGINE AND ENGINE COOLING
The contact owns a 2020 GMC Sierra 1500. The contact stated that while driving approximately 55 MPH, the vehicle started losing power and decelerated. The check engine warning light was flashing with several unknown messages displayed. The vehicle was parked on the side of the road and later towed to the local dealer to be diagnosed. The contact was informed that the lifters, push rods, and camshaft had failed and needed to be replaced. The lifters, push rods, and camshaft were replaced, and the vehicle was repaired. The contact stated that approximately 6,900 miles later, the failure reoccurred. The vehicle was towed back to the local dealer, and the contact was informed that the engine crankshaft and connecting rods had failed and the engine needed to be replaced. The vehicle was not yet repaired. The failure mileage was 115,000.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11764196September 14, 2026
POWER TRAIN
Transmission shifting hard in first few gears and only 87,000 miles on Transmission.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11764047September 14, 2026
FORWARD COLLISION AVOIDANCE: ADAPTIVE CRUISE CONTROL
The contact owns a 2020 GMC Sierra Denali. The contact stated that while driving with Adaptive Cruise Control set to 55 MPH, the vehicle suddenly accelerated. The contact depressed the brake pedal to disengage the Adaptive Cruise Control settings, preventing the vehicle from crashing into the vehicle ahead. The contact stated that the failure had occurred while the Adaptive Cruise Control was engaged. The approximate failure mileage was 99,000.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11763621September 11, 2026
ENGINE
The contact owned a 2020 GMC Sierra Denali. The contact stated that while the vehicle was parked, there was an abnormal knocking sound coming from the engine compartment. The check engine warning light was intermittently illuminated. The vehicle was taken to a dealer; however, the cause of the failure was not yet determined. The dealer advised the contact to purchase a new vehicle because the engine would eventually need to be replaced. The contact stated that at approximately 3,000 miles, there was an abnormal odor oil burning odor coming from the vehicle. The contact stated that the vehicle was consuming an excessive amount of engine oil and approximately 5 quarts needed to be added between scheduled oil changes. The failure mileage was approximately 25,000.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11763011September 9, 2026
ENGINE
I was driving home with my wife. The engine just cut off. No power to the gas pedal. Luckily we were able to coast long enough to find a shoulder to pull off onto. Truck wouldn’t restart. Had to call a tow truck and have it towed to the Chevy dealership. The engine was already repaired once. Ref number 11696129. I just got the truck back and fixed again. So far I’ve had to pay for 2 tows and 2 repairs costing be about 3000 dollars. Both repairs have been done at a Chevy dealership.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11763015September 9, 2026
ENGINE, POWER TRAIN
Powertrain issues and a chassis issue that is extremely dangerous.Tailgate on rare occasions falls open by itself. There is a design flaw in the placement of the catalytic converters. The heat is burning up the fluid. I could not believe my eyes when I serviced the transmission. This is another shortcut by GM to save on the extra wiring needed for the oxygen sensors (2)in the converters and the two oxygen sensors downstream of the converters. There is plenty of room for the converters further down by the tail shaft to drive shaft connections. This is GM’s way of being cheap. Here’s the problem. The converters get way too hot. The fill plug for the transmission which is behind a low rent heat shield crumbled into my hands from excessive heat buildup. GM knows there is a problem with the fluid breaking down. Their bandaid answer is to use Mobil 1 fluid instead of the recommended Dexron 6. What needs to happen is a safety recall issued for the unwanted tailgate deploying all by itself. There needs to be a redesign in the exhaust system. The Transmission (8 Speed) has a catalytic converter exactly on both sides and the crossover pipe runs directly under the transmission sump pan. No wonder they are having issues with transmissions burning up. THIS IS A FIRE HAZARD !!! With the converters being so close to the exhaust manifolds, a leak from the engine or the transmission would be enough to ignite and possibly kill the occupants. All in the name of saving a few cents in wiring. Myself, I am a retired GM Mechanic. I started working at Sewell Cadillac in [XXX] in 1975. I have held the title of ASE Master Tech. Cadillac Master Tech. I have been a GM Shop Foreman and A GM Service and Parts Director in my Career. I retired from Federal Express as in charge of Fleet Maintenance and GSE(Aircraft Equipment). I have certifications from Mercedes, BMW, Toyota, Commander Loaders, Goodyear, and more. Given the right set of circumstances, it could end very badly. Dangerous Truck ! INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INF
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11762788September 8, 2026
ENGINE
I was driving on the highway at 70mph when out of no where my truck stopped running and I received a message warning to put the truck in neutral and restart the engine. It was very alarming being on the highway and this happening. I was unable to restart the vehicle so I had to coast and navigate us at high speed to the should of the highway. Since it was Labor day I had to sit for over 4 hours before getting a tow vehicle at 2am to tow my truck to [XXX] FLOW Buick GMC. They contacted me and told me that my engine had seized and that it was possible bearings or something that made it seize and I need a whole new engine. They quoted me $12,500. I have not done anything yet in repairs and I now contacted GM and submitted a Case #XXX. I notified them I am aware of the known issue and the GM service bulletin PIP5900. I am waiting for them to respond now. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11762548September 7, 2026
ENGINE, SERVICE BRAKES
Lifter failed due to AFM system. Cyl 8 misfire due to oil fouling. The onboard computer got confused and would not release the parking brake until repeated attemtps to release it. 5.3L V8 2020 model year 115250 miles. Isn't this the same problem as the 2021 and newer engines? 8spd transmission. AFM failure. $9k repair.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11762323September 5, 2026
ELECTRICAL SYSTEM
When I try to start my truck it comes up as service trailer brake control module and it has caused my truck battery to drain so I cant even crank my truck up.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11762016September 3, 2026
ENGINE
2020 GMC Sierra 1500 AT4, 3.0L LM2 Duramax. In service 08/13/2020. Five glow plug failures on five different cylinders in under 19,000 miles, all at one GM dealer, all part 24000504: Cyl 1, 10/21/2024, 38,650 mi, P0671, RO 13714, warranty. Cyl 6, 11/05/2024, 38,793 mi, P1330, RO 26665, warranty. Cyl 4, 11/29/2024, 39,683 mi, P133B, RO 57498, warranty. Cyl 3, 01/22/2026, 52,959 mi, P0673/P06C7/P133A, RO 100951, I paid $713.38. Cyl 2, 08/26/2026, 57,466 mi, P06C6/P0672/P1339, RO 115953, GM under N232430460. The first three came within 39 days and 1,033 miles. Every RO documents the same finding: high internal resistance in the plug, circuit tests good. The failure is internal to the plug. Glow plug failure on a diesel causes hard starting, extended cranking, no-start in cold weather, and startup misfire - risk of being stranded or unable to start. GM has documented this defect three times: PIP5762 (12/2020), TSB 22-NA-027 (2/2022), Special Coverage N232430460 (1/2024). All name an inadequate camshaft housing cover baffle plate weld, and all limit the remedy to cylinder 2. On the recorded walkaround for RO 115953 the tech stated my engine serial falls inside the affected population and my earlier failures were probably the same condition. GM replaced only the glow plug. The camshaft cover GM identifies as the cause is still installed; GM quoted me $5,100 to replace it at my expense. Four of five failures were on cylinders 1, 3, 4 and 6, outside that scope. If the bad weld passes oil into the PCV and intake path rather than only the cylinder 2 glow plug well, ingested oil would reach other cylinders. No RO shows anyone inspected the intake tract, charge piping, cooler, PCV separator, a removed plug, or a glow plug well. I ask ODI to examine whether the cylinder-2-only scope of N232430460 is under-inclusive, whether replacing the plug while leaving the cause installed is an adequate remedy, and whether repeated internal failure of part 24000504 warrants a recall.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11760597August 29, 2026
ENGINE
Driving approximately 75mph on a local highway, my engine shut down with no warning, the screen said to shift into neutral to restart but nothing happened so I was stranded along the side of the highway and had to wait 2hrs for a tow truck in the middle of the night and the engine is currently locked up.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11759608August 26, 2026
ENGINE, POWER TRAIN
High pressure fuel pump went at 80k and now on my 2nd transmission under 100k miles this is absolutely absurd
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0

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