2020 GMC Sierra 1500 Problems

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.

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.

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.

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

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.

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

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.

The contact’s mother-in-law owns a 2020 GMC Sierra 1500. The contact stated that while her brother-in-law was starting the vehicle, the brake, service engine, and engine warning lights illuminated and the vehicle failed to start. The contact stated that the failure was associated with NHTSA Action Number: EA25007 (ENGINE, ENGINE, AND ENGINE COOLING) and PE25001 (ENGINE, ENGINE, AND ENGINE COOLING). The vehicle was towed to a local dealer, where it was diagnosed with engine failure. The vehicle was not repaired. The owner was scheduled to meet with the dealer to discuss the issue. The manufacturer was contacted and confirmed that there were no open recalls on the VIN related to the failure. The failure mileage was approximately 45,000.

- THE GROUND STRAP CORRODED AND BROKE APART. YES, I HAVE THE GROUND CABLE THAT FAILED, IF NEEDED FOR INSPECTION. - YES!!! THE TRUCK'S STEERING KEPT GOING IN AND OUT OF MANUAL STEERING AND THE ENGINE REDUCED IN SPEED ALLOWED, AND THEN THE ENGINE CUT OUT ON ME COMPLETELY - WHILE I WAS IN THE MIDDLE OF A BUSY ROAD TRYING TO TURN ONTO A SIDE STREET. THEN THE ENGINE WOULD NOT RESTART. - I HAD THE TRUCK TOWED ON A FLAT BED TO A GMC DEALERSHIP NEARBY. THEY CONFIRMED THE ISSUE WAS THAT THE GROUND STRAP FAILED. THEY REPLACED THE PART AT MY COST, WHICH FIXED THE ISSUES. - YES, THE DEALERSHIP INSPECTED AND CONFIRMED THE ISSUE WAS THE CORRODED AND BROKEN GROUND STRAP. - YES, THERE WERE MANY WARNING MESSAGES THAT STARTED TO APPEAR ABOUT 3-4 DAYS PRIOR TO THE COMPLETE FAILURE OF THE ELECTRICAL SYSTEM. I STARTED SEEING A MESSAGE ABOUT SERVICING THE TRAILER BRAKE SYSTEM, AND ANOTHER ABOUT SERVICING THE SIDE DETECTION SYSTEM. THEN A SERVICE POWER STEERING WARNING AND TO DRIVE WITH CARE. THE CHECK ENGINE LIGHT WAS OFF AND ON OVER THAT TIME. - I CHECKED THE WIRE CONNECTIONS IUNDER MY VEHICLE TO CHECK FOR BROKEN WIRES OR CORROSION. I DID NOT FIND ANY. I THEN CHECKED IF A HARD BATTERY RESET WOULD WORK, BUT IT DID NOT. LASTLY, I BOUGHT A NEW BATTERY TO REPLACE THE EXISTING ONE, EVEN THOUGH THE EXISTING BATTERY HAD NO ISSUES EVEN WHEN TESTED UNDER LOAD. THAT RESOLVED THE ISSUE FOR ABOUT 35 MINUTES THAT NIGHT AND THEN THE NEXT MORNING. AFTER THAT, THE ELECTRICAL SYSTEM FAILED AND THE TRUCK WOULD NOT START. AT THAT POINT I GOT TOWED IN TO THE GMC DEALERSHIP. I HAD TO LEAVE THE TRUCK FOR A WEEKEND, AND THE DEALERSHIP DID NOT COME UP WITH A LOANER, EVEN THOUGH I REQUESTED ONE. I GOT THE TRUCK BACK ON MONDAY AFTERNOON AND EVERYTHING WAS WORKING FINE SINCE THEN. - OVER THAT WEEKEND, I WAS AMAZED TO FIND OUT ABOUT THE BULLETIN GM RELEASED TO COVER ONLY SOME TRUCKS FOR THE ISSUE, BUT NOT OTHERS! MY TRUCK IS STILL NOT COVERED, DESPITE THE OBVIOUS SAFETY ISSUES I EXPERIENCED!!

A known problem with these trucks is ground strap failure. I was driving and all the sudden lost power steering which almost caused an accident. There is a customer satisfaction program N252515590 that covers 2019-2024 trucks but mine was not included in this for some reason. I did have the truck fixed a my cost and was looking to get my money back from GM. I'm not sure if you can help with this but wanted to make a report that is happening with more trucks then they are fixing. If you need any other info from me please let me know

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.

Piston 5 dropped compression to 120 the rest were 190-200. The engine failed therefore none of my parking assist sensors were working and I backed into a car because the truck was misfiring.

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.

Gas fill door won’t stay closed

My truck transmission beed jerking off and on for over a year. One time it lose power when i was driving and could have caused an accident. I took it to the dealership and they said i new a new transmission for $12000. Something just doesn’t seem right about this! I brought a brand new truck thats unsafe and its no recall for my model but other models with the same issue had a recall. I would just like some answers. I feel like i brought a lemon. Thanks for listening.

My 2020 GMC Sierra Denali diesel with approximately 90,000 miles experienced two separate front suspension failures within a short period of time. The driver side tie rod and wheel hub failed first and required repair. Shortly after, the passenger side front suspension failed in a similar way and the vehicle had to be towed. These failures caused the front wheels to become unstable and created a serious safety concern while driving. Suspension components such as tie rods and hubs should not fail at this mileage under normal driving conditions.

The frame of the back window is cracking allowing water to come in through the back glass. This is causing the headliner and other components such as air bags and other electrical components to get wet and damaged. This could cause risk of fire or failure of safety components within the vehicle such as air bags, cameras and other sensors. With water intrusion comes the high risk for mold to develop and cause serious health risks. GMC is aware of this issue and will not agree to repair it. A GMC dealer has inspected the glass and said it was a faulty seal but since it's not in the 3 year warranty window, it's not covered. Independent auto glass companies state they have seen this issue many times and the glass seal is faulty. GMC should do the right thing and fix this issue. This devalues the vehicle and the GMC brand and poses serious risks to driver. I have created a case with GMC and submitted photos, videos and dealership estimates for proof.

Back window leaks down onto electrical compents and causes mold behind rear seat, plus staining mold on headliner

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.

The frame of the back window is cracking allowing water to come in through the back glass. This is causing the headliner and other components such as air bags and other electrical components to get wet and damaged. This could cause risk of fire or failure of safety components within the vehicle such as air bags, cameras and other sensors. With water intrusion comes the high risk for mold to develop and cause serious health risks. GMC is aware of this issue and will not agree to repair it. A GMC dealer has inspected the glass and said it was a faulty seal but since it's not in the 3 year warranty window, it's not covered. Independent auto glass companies state they have seen this issue many times and the glass seal is faulty. GMC should do the right thing and fix this issue. This devalues the vehicle and the GMC brand and poses serious risks to driver. I have created a case with GMC and submitted photos, videos and dealership estimates for proof.

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.

Driving on state highway at posted speed. A deer ran into the right front and side of vehicle. Side airbags deployed. When the right side airbag deployed, it burned a hole in my passengers winter coat that completely went through the right sleeve forearm and scorched the sweatshirt that she was wearing under the coat. Smoke was visibly apparent in the cab of the vehicle. We thought the truck was on fire , then finally determined it was the sleeve of here coat.

DANGEROUS VISIBILITY HAZARD WHEN BACKING UP VEHICLE AT NIGHT. INFOTAINMENT SCREEN SWITCHES TO "FULL BRIGHTNESS" WHEN BACKUP CAMERA IS ACTIVATED, RESULTING IN BLINDING LIGHT TO DRIVER. DRIVER CAN NOT BACKUP SAFELY WITHOUT PHYSICALLY COVERING THE SCREEN TO REGAIN VISIBILITY. SCREEN BRIGHTNESS REFLECTS OFF ALL 4 WINDOWS, WINDSHIELD AND BACK GLASS. SIDE MIRRORS ARE UNUSABLE IN THIS CONDITION. THERE WAS A FIX FOR THIS ISSUE ON PREVIOUS GM MODELS, (PRIOR TO 2018), HOWEVER NO FIX FOR 2019 - PRESENT

BRAND NEW TRUCK. STUCK AT THE GYM IN THE MIDDLE OF THE NIGHT TRUCK WONT START. THE INTERIOR LIGHTS, HEAD LIGHTS, AND RADIO WONT SHUT OFF. VEHICLE WONT START. I'M ASSUMING THE BATTERY WAS DRAINED BECAUSE INTERIOR LIGHTS, EXTERIOR LIGHTS, RADIO, WONT SHUT OFF. HAS TO BE SOME KIND OF ELECTRICAL MALFUNCTION. WAITING ON GM ROADSIDE.

Our middle seat belt has stopped working in the back seat- we have not had it replaced yet. No damage was done on it by us, but will not click into the buckle. Driving on the hi-way engine started making awful noises. We pulled over and had the truck towed to Royal Moore GMC in Hillsboro Oregon as we didn't want to cause any more harm to the engine. Royal Moore GMC informed us the engine rod bearing failed on [XXX], leading to breaching of the engine block by the rod. This caused us to replace the entire engine at the cost of over 13,000$ and no vehicle for over 3 months. (Along with engine replaced they told us we had to replace the O2 sensor as the light came on after the engine was replaced). We had to take a hardship loan to get the engine replaced, and had the truck back for 1 day before we had a o2 error l light came back on. At this time (May 5th) we are still waiting for our truck back. Royal Moore doesn't know why the engine light is on- and contacted TAC for GMC. We also contacted GMC multiple times when we were waiting for the engine. They have offered no help to us besides empty promises to call us back later. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

KEEP GETTING "SERVICE SAFETY RESTRAINT SYSTEM " ALERTS. VEHICLE ONLY HAS 550 MILES. ALERTS ARE INTERMITENT WHEN DRIVING. CONTACTED THE DEALER AND WAS ADVISED THAT UNLESS IT REMAINS ON THEY COULD NOT TRACE THE ISSUE.

The contact owns a 2020 GMC Sierra 1500. The contact stated that while driving 60 MPH, the horn failed to function as intended. There were no warning lights illuminated. The contact stated that on a separate occasion, the right lane sensor stopped working as intended. There were no warning lights illuminated. The contact stated that on a separate occasion, while driving 60 MPH in the rain or on rough asphalt, the rear suspension caused the vehicle to fishtail to the right. The contact turned to the left to control the vehicle. The contact stated that the vehicle returned to normal functionality after the failure. The low transmission fluid warning light was illuminated. The vehicle was taken to an independent mechanic, who diagnosed the vehicle with an electrical systems failure. The independent mechanic informed the contact that there was adequate transmission fluid inside the transmission, and it was unclear why the warning light was illuminated. The contact was informed that weights were added to the wheels to balance each wheel. The vehicle was not yet repaired for the other failures. The contact stated that the transmission was replaced a year prior to the failure, and the horn had failed to function soon after the transmission replacement. The manufacturer was made aware of the failure. The failure mileage was approximately 68,000.

The contact owns a 2020 GMC Sierra 1500. The contact stated that while driving 65 MPH, the check engine and the traction control warning lights illuminated. The contact stated that a dealer was contacted. The vehicle was taken to a dealer where it was diagnosed and determined that the engine needed to be replaced. The vehicle was not repaired. The manufacturer was notified of the failure and informed the contact that he would receive a callback. The approximate failure mileage was 87,000.

The contact owns a 2020 GMC Sierra 1500 equipped with Goodyear Tires, Tire line: Wrangler AT/S, Tire Size: LT275/65/R20, DOT Number: PJOTJB1V. The contact stated while driving 65 MPH, there was a slight wobble and then an impact was felt when the rear passenger’s side tire tread separated and damaged the rear fender and bumper. The contact pulled over and had assistance replacing the rear passenger’s side tire with the spare tire. The dealer was made aware of the failure and was in possession of the failed tire. The manufacturer was not made aware of the failure. The failure mileage was unknown.

TL* THE CONTACT OWNS A 2020 GMC SIERRA 1500 EQUIPPED WITH BRIDGESTONE TIRES, TIRE LINE: ALENZA A/S 02, TIRES SIZE: 275/50/R22, DOT NUMBER: UNKNOWN. THE CONTACT STATED THAT THE TIRES FAILED TO HOLD THE TIRE PRESSURE. THE VEHICLE WAS TAKEN TO SCENIC CHEVROLET BUICK GMC CADILLAC (2300 ROCKFORD ST, MT AIRY, NC 27030) WHERE THE VEHICLE WAS PURCHASED. THE TECHNICIAN ADDED NITROGEN GAS INTO THE TIRES HOWEVER, THE FAILURE PERSISTED. THE CONTACT STATED THAT A LETTER WAS SENT TO THE MANUFACTURER HOWEVER, THERE WAS NO RESPONSE. THE FAILURE MILEAGE WAS 2,976. *JS *JS

The contact owns a 2020 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the vehicle unexpectedly sputtered. There was no warning light illuminated. The vehicle was taken to the dealer, where it was diagnosed with torque converter failure. The dealer determined that the torque converter needed to be replaced. The vehicle was repaired. The contact later stated that while driving at an undisclosed speed, the vehicle unexpectedly went into LIMP Mode. There was no warning light illuminated. On several occasions, the vehicle unexpectedly downshifted and lunged forward while stopped at a traffic light. There was no warning light illuminated during the failure. The dealer was contacted. The vehicle was not diagnosed or repaired. The manufacturer was made aware of the failure and referred the contact to the NHTSA Hotline for assistance. The failure mileage was approximately 97,000.