2020 GMC Sierra 1500 problems

POWER TRAIN

Transmission shifting hard in first few gears and only 87,000 miles on Transmission.

NHTSA complaint #11764196 — an unverified report by a vehicle owner.

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

NHTSA complaint #11763015 — an unverified report by a vehicle owner.

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.

NHTSA complaint #11763011 — an unverified report by a vehicle owner.

ENGINE

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

NHTSA complaint #11763015 — an unverified report by a vehicle owner.

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)

NHTSA complaint #11762788 — an unverified report by a vehicle owner.

ENGINE

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.

NHTSA complaint #11762548 — an unverified report by a vehicle owner.

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.

NHTSA complaint #11762548 — an unverified report by a vehicle owner.

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.

NHTSA complaint #11762016 — an unverified report by a vehicle owner.

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.

NHTSA complaint #11760597 — an unverified report by a vehicle owner.

POWER TRAIN

High pressure fuel pump went at 80k and now on my 2nd transmission under 100k miles this is absolutely absurd

NHTSA complaint #11759608 — an unverified report by a vehicle owner.

POWER TRAIN

This truck was bought brand new by my father. Around 38,000 miles it begin having issues with shifting which eventually got worse. When I searched google for issues many others on different pages have had the same issues. The shifting would be so rough it feels like you're being hit by another vehicle. This could cause accidents for anyone who cannot afford to fix these known issues by GMC. I was told today by my local dealership their transmissions for my specific truck is on backorder. Should that not indicate an issue when this truck is a 2020. But to my father having a stroke I was not able to handle this issue sooner as he was very ill for four years and passed last year. The truck was not the priority at the time.

NHTSA complaint #11759816 — an unverified report by a vehicle owner.

VEHICLE SPEED CONTROL

This truck was bought brand new by my father. Around 38,000 miles it begin having issues with shifting which eventually got worse. When I searched google for issues many others on different pages have had the same issues. The shifting would be so rough it feels like you're being hit by another vehicle. This could cause accidents for anyone who cannot afford to fix these known issues by GMC. I was told today by my local dealership their transmissions for my specific truck is on backorder. Should that not indicate an issue when this truck is a 2020. But to my father having a stroke I was not able to handle this issue sooner as he was very ill for four years and passed last year. The truck was not the priority at the time.

NHTSA complaint #11759816 — an unverified report by a vehicle owner.

UNKNOWN OR OTHER

This truck was bought brand new by my father. Around 38,000 miles it begin having issues with shifting which eventually got worse. When I searched google for issues many others on different pages have had the same issues. The shifting would be so rough it feels like you're being hit by another vehicle. This could cause accidents for anyone who cannot afford to fix these known issues by GMC. I was told today by my local dealership their transmissions for my specific truck is on backorder. Should that not indicate an issue when this truck is a 2020. But to my father having a stroke I was not able to handle this issue sooner as he was very ill for four years and passed last year. The truck was not the priority at the time.

NHTSA complaint #11759816 — an unverified report by a vehicle owner.

STRUCTURE:BODY

I have a rear sliding window on the cab of my truck that leaks from both ends of the plastic guide. I noticed it when placing my young children in their car seats. I contacted my dealership and was informed the repair would cost $1500+ and not be covered by GM or warranty.

NHTSA complaint #11759726 — an unverified report by a vehicle owner.

ENGINE

High pressure fuel pump went at 80k and now on my 2nd transmission under 100k miles this is absolutely absurd

NHTSA complaint #11759608 — an unverified report by a vehicle owner.

ENGINE

On XXX my GMC 6.2L Sierra 1500 Denali engine cutoff in Traffic and had to be towed. There was no indications prior to failure. Found out after replacing battery that the 400amp fuse blew and the engine seized. Vehicle was then towed to Hendrick Buick GMC dealer in [XXX] for repair. My engine has 49,500 miles but is out of warranty due to time. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA complaint #11759731 — an unverified report by a vehicle owner.

ENGINE

Misfire on 2 cylinder, noise on start up diagnostic code P0300 P0302 P050 I was driving home and the engine started making a strange sound, vehicle would could no increase speed normally. The dealership did basic analysis from the onboard computer and did a compression test. Heavy knocking sound on passenger side of the engine. The issue happened on Aug 5th 2026. The issue is due to the AFM that causes the lifter to fail and dealership says I need a new engine $15787 or replace cam shaft $14530.

NHTSA complaint #11759795 — an unverified report by a vehicle owner.

ENGINE

Engine went into limp mode and engine is no longer good

NHTSA complaint #11759601 — an unverified report by a vehicle owner.

POWER TRAIN

Our 2020 GMC SIERRA 1500 has suffered catastrophic systems and engine failure including the brakes multiple times for almost 4 years. It has happened in high traffic and on the interstate each time having to be coasted off of the road to come to a rolling stop. There have been nine repair attempts with GM dealers repeatedly stating the issues were repaired and returning our vehicle to us. We began making the CEO and Executive team aware of the potentially deadly safety hazards including the fact that I, [XXX] am disabled and power wheelchair dependent requiring a truck that can carry my power wheelchair. We have sent numerous emails to Ms. [XXX] and the Executive team numerous times informing them in detail, each time, of all issues involved. We started communicating via phone and email with customer care to no avail. All attempts at repair finally ended in complete engine failure leaving us with an estimate to replace the engine of over $13,000. We have also, submitted a detailed complaint to the Attorney General’s Office and after review were given the Case # TCP - XXX. I will attach the Complaint and Addendum sent to the Attorney General along with two of the emails sent to Ms. [XXX] and her team informing her of all issues with the truck. They took no action to actually help us get this truck off of the road knowing it was having catastrophic engine and system failure and that it had to be driven to transport a disabled power wheel dependent with severe medical issues and the medically necessary power wheelchair. I am also attaching the earliest OnStar Diagnostic notice of Engine, Transmission and Emissions system issues from May of 2023. The issues have remained the same from the beginning only worsening though my husband has only driven the truck in town on slower less busy streets learning how to make adjustments such as pumping the brakes and starting and stopping the truck to keep it going. My carrier is installed and yet it is undrivable. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATIO

NHTSA complaint #11759239 — an unverified report by a vehicle owner.

POWER TRAIN

The 5.3L Engine active fuel management failure problem. This known problem with the GMC motors was not disclosed by any dealerships or the manufacturer. While driving down the roadway, the truck had an engine malfunction and I was fortunate enough to be able to safely pull over. The check engine light activated and I took it to the dealer the next day. I was informed by the dealer that this was a known, common issue that GM was aware of but was not offering assistance. I had to pay $11,000 out-of-pocket because of this.

NHTSA complaint #11759295 — an unverified report by a vehicle owner.

ELECTRICAL SYSTEM

Our 2020 GMC SIERRA 1500 has suffered catastrophic systems and engine failure including the brakes multiple times for almost 4 years. It has happened in high traffic and on the interstate each time having to be coasted off of the road to come to a rolling stop. There have been nine repair attempts with GM dealers repeatedly stating the issues were repaired and returning our vehicle to us. We began making the CEO and Executive team aware of the potentially deadly safety hazards including the fact that I, [XXX] am disabled and power wheelchair dependent requiring a truck that can carry my power wheelchair. We have sent numerous emails to Ms. [XXX] and the Executive team numerous times informing them in detail, each time, of all issues involved. We started communicating via phone and email with customer care to no avail. All attempts at repair finally ended in complete engine failure leaving us with an estimate to replace the engine of over $13,000. We have also, submitted a detailed complaint to the Attorney General’s Office and after review were given the Case # TCP - XXX. I will attach the Complaint and Addendum sent to the Attorney General along with two of the emails sent to Ms. [XXX] and her team informing her of all issues with the truck. They took no action to actually help us get this truck off of the road knowing it was having catastrophic engine and system failure and that it had to be driven to transport a disabled power wheel dependent with severe medical issues and the medically necessary power wheelchair. I am also attaching the earliest OnStar Diagnostic notice of Engine, Transmission and Emissions system issues from May of 2023. The issues have remained the same from the beginning only worsening though my husband has only driven the truck in town on slower less busy streets learning how to make adjustments such as pumping the brakes and starting and stopping the truck to keep it going. My carrier is installed and yet it is undrivable. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATIO

NHTSA complaint #11759239 — an unverified report by a vehicle owner.

ENGINE

I purchased my 2020 GMC Sierra 1500 AT4 with the L87 6.2L V8 new from a GMC dealer in March 2020 for $65,910 (VIN [XXX]). The truck has primarily highway mileage, very little towing, and has been well maintained. At 166,634 miles on [XXX], the truck developed a flashing check-engine light. The GMC dealer diagnosed “Cyl 3 lifter failure with camshaft damage” and determined that replacing the engine was preferable to repairing it because of the vehicle's mileage. The dealer installed a replacement OEM GMC engine and replaced both broken engine mounts. The replacement engine and installation cost $11,778. The replacement engine has subsequently required multiple repairs. At approximately 170,411 miles, the GMC dealer documented an exhaust leak that had occurred since the engine repair and a coolant leak from the upper radiator hose; both were repaired. At approximately 187,699 miles, the truck experienced overheating, coolant leakage, and loud engine-area noise. The dealer found that the water pump was coming apart and replaced the water pump and related components. I am reporting this vehicle because it is a 2020 Sierra equipped with the L87 6.2L engine and experienced catastrophic lifter/camshaft failure requiring complete engine replacement, followed by multiple engine-related repairs. I believe this history is relevant to NHTSA's investigation of L87 engine failures in earlier model years and warrants consideration when evaluating whether the known L87 engine defect extends beyond the vehicles currently covered by the recall. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA complaint #11759035 — an unverified report by a vehicle owner.

ENGINE

Our 2020 GMC SIERRA 1500 has suffered catastrophic systems and engine failure including the brakes multiple times for almost 4 years. It has happened in high traffic and on the interstate each time having to be coasted off of the road to come to a rolling stop. There have been nine repair attempts with GM dealers repeatedly stating the issues were repaired and returning our vehicle to us. We began making the CEO and Executive team aware of the potentially deadly safety hazards including the fact that I, [XXX] am disabled and power wheelchair dependent requiring a truck that can carry my power wheelchair. We have sent numerous emails to Ms. [XXX] and the Executive team numerous times informing them in detail, each time, of all issues involved. We started communicating via phone and email with customer care to no avail. All attempts at repair finally ended in complete engine failure leaving us with an estimate to replace the engine of over $13,000. We have also, submitted a detailed complaint to the Attorney General’s Office and after review were given the Case # TCP - XXX. I will attach the Complaint and Addendum sent to the Attorney General along with two of the emails sent to Ms. [XXX] and her team informing her of all issues with the truck. They took no action to actually help us get this truck off of the road knowing it was having catastrophic engine and system failure and that it had to be driven to transport a disabled power wheel dependent with severe medical issues and the medically necessary power wheelchair. I am also attaching the earliest OnStar Diagnostic notice of Engine, Transmission and Emissions system issues from May of 2023. The issues have remained the same from the beginning only worsening though my husband has only driven the truck in town on slower less busy streets learning how to make adjustments such as pumping the brakes and starting and stopping the truck to keep it going. My carrier is installed and yet it is undrivable. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATIO

NHTSA complaint #11759239 — an unverified report by a vehicle owner.

ENGINE

The 5.3L Engine active fuel management failure problem. This known problem with the GMC motors was not disclosed by any dealerships or the manufacturer. While driving down the roadway, the truck had an engine malfunction and I was fortunate enough to be able to safely pull over. The check engine light activated and I took it to the dealer the next day. I was informed by the dealer that this was a known, common issue that GM was aware of but was not offering assistance. I had to pay $11,000 out-of-pocket because of this.

NHTSA complaint #11759295 — an unverified report by a vehicle owner.