GMC Sierra 1500 misfire problems

Filed Oct 19, 2026 · Engine · MI

In April 2025, we purchased a new GMC Denali Sierra 1500 Ultimate pickup truck. Concerns – Many of these comments appear in the Dealer Service Reports 1st Service Visit 10/17/25 At our first oil change and scheduled maintenance (10/17/25) with mileage of 5403 miles, during the drop-off I informed the GM Service Advisor of a clicking sound from the engine which I thought might be a fan belt. When I picked up the truck from Service, the Service Adviser informed me that upon startup, a “clatter” type noise was heard, “reminiscent of bad lifters.” The Service Adviser reported that during the mechanic’s test drive, the “clicking noise would get louder with engine speed.” No trouble codes were found after being checked by the MDI. They checked for misfires and a few misfires were found but “not often. At “idle” during this service call, the Left Engine Bank had a “good click/metallic tap to it.” “When the idle was raised, the Right Bank would get loud and had a loud tapping sound.” The oil change did not show any visible metal particles. The GM Service Department recommended a “complete tear-down of the engine for further inspection,” tentatively scheduled in a few weeks, pending Service availability. The Service Adviser stated he would recommend an engine replacement. 2nd Service Visit 10/27/2025 While driving the truck, I noticed that the engine “ticking” had gotten louder, and a Check Engine light had gone on and off. I returned to the Service Department on 10/27/25 (mileage 5807). The Service Department inspected the vehicle and found no “stored DCTS” but found “noise is there for internal engine noise.” The team recommended “tear-down or possible new engine.” Service appointment was set for 11/3/2025 for 5-days. 3rd Service Visit 11/3-7/2025 Service department reported that there were no problems. Vehicle was not under recall..... Scheduling a oil change this week. 14,500 miles.

Filed Oct 7, 2026 · Engine · 110,000 miles · MN

The contact owns a 2021 GMC Sierra 1500. The contact stated that while driving and towing a 5,000-pound load, the vehicle made an abnormally loud sputtering sound at 3,000 RPM. The contact stated that the failure was more noticeable while towing a load. The vehicle was taken to an independent mechanic, where an audible diagnostic test was performed and the contact was informed that the sound was related to the engine bearings. The vehicle was then taken to the dealer, where it was diagnosed with fifty-two engine misfires. The contact was informed that the misfires should have caused the check engine warning light to illuminate; however, the light was not illuminated. The dealer replaced the ignition coils and spark plugs; however, the failure recurred while driving. The manufacturer was notified of the failure. The failure mileage was approximately 110,000.

Filed Sep 24, 2026 · Engine · CA

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.

Filed Sep 24, 2026 · Engine · OH

2026 GMC Sierra SLT with 3.0 Duramax diesel engine. While driving down the road with the cruise set to 55 MPH on 8/29/26, the engine started to run rough. I slowed down, but this did not seem to help; I sped up, and the problem persisted no matter what I did. Service traction control and service ESC displayed on the dash. I drove to the dealership; their service department was closed because it was Saturday. I took my salesman for a ride so he could witness the issue firsthand. He confirmed something was not right, and they put me into a loaner vehicle. The truck has 848 miles on it. Service diagnosed it as a fuel issue in cylinder 2, replaced the injector, but the issue did not go away. GM TAC team advised replacing the motor; that is what I am currently waiting on. The dealer has the motor and is awaiting the install.

Filed Sep 22, 2026 · Engine, Fuel system · NC

On [XXX], my vehicle suffered a complete loss of propulsion on the highway, displaying fault codes P0324 and P0016. The vehicle was taken to Boyd's Tar Heel Chevrolet in Roxboro, NC, where the engine block was replaced under the official GM 6.2L engine safety recall.The truck was delivered back to me, and on the very first day I drove it—only 28 miles from my house—it suffered a secondary catastrophic loss of propulsion on the highway on [XXX]. The check engine light began flashing violently, indicating an immediate catalyst-damaging safety hazard, and the vehicle displayed fault code P0307 (Cylinder 7 Misfire).The dealership explicitly instructed me to stop driving the vehicle immediately, authorized the recovery, and told me to bill the tow directly to them. After towing the vehicle back to their facility, Boyd's Tar Heel Chevrolet reversed their position. They are now attempting to hold me financially responsible for the towing fees, along with spark plugs, wiring, and fuel injector services, claiming the failure is due to routine maintenance.This represents a severe highway safety hazard, a direct failure of the manufacturer's official recall remedy, and potential dealer misconduct to avoid liability under the active the federal safety agency Engineering Analysis EA26005 for post-recall 6.2L engine failures. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Sep 16, 2026 · Engine · 159,000 miles · CO

The contact owns a 2019 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the vehicle came to a full stop to allow wildlife to cross the road. Upon accelerating, the engine made an abnormal banging noise. The contact stopped to inspect the vehicle and observed an engine misfire while idling. The vehicle was towed to the residence, where an independent mechanic diagnosed that the lifters had collapsed, and that the engine needed to be disassembled for further diagnostic testing. The failure mileage was approximately 159,000.

Filed Sep 10, 2026 · Engine · WA

I purchased said vehicle with a little over 76,000 miles on XXX from NW Chevrolet, [XXX]. Dealership service the engine on XXX and remained on their lot until it was sold. While driving home, I smelled gas fumes coming into the cabin and the engine was misfiring causing slight hesitation in motor acceleration while adjusting to speed limits and climbing hills. I told management at the dealership about these issues on XXX. My vehicle is currently in the shop to fix the fuel injection system, spark plugs, grounding issues as of XXX to fix the dealerships mistake costing more out of pocket expense. Management will not do anything about it because it was sold (As Is) without a warranty which I refused to purchase through finance and interest charges on a car loan. I purchased a 4-year warranty through Endurance on XXX with a 30 day wait period before filing a claim. GM is letting their dealerships advertise and sell problem vehicles with known motor issues to consumers while marking up the sale price. Vehicles should never be sold until GM fixes all motor defects before advertising to the consumer. The consumer is at serious financial risk when getting an auto loan paying on a broken vehicle. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Sep 7, 2026 · Brakes, Engine · NC

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.

Filed Sep 3, 2026 · Engine · UT

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.

Filed Aug 28, 2026 · Engine · MI

I had the L87 recall completed, and the vehicle passed inspection. The dealership completed the required protocol and replaced the engine oil with 0W-40. Approximately 6,000 miles later, while traveling at about 75 mph and six hours from home, I experienced a brief loss of power followed by an immediate return of power. My wife and I noticed it but, with no warning lights or alerts, continued driving while monitoring the vehicle. About 10 miles later, we began hearing a faint squealing noise that progressively became worse. I was able to exit the highway safely, but once I came to a complete stop, the engine shut off and would not restart. I had the vehicle towed to the nearest dealership, where it was determined that I had suffered a catastrophic engine failure. No loaner vehicle was available, leaving my family stranded six hours from home with an inoperable vehicle. It took approximately seven to eight weeks for the repair to be completed. When I received the vehicle back, I immediately noticed something still was not right. At around 40 mph and 1,000 RPM, the truck would shudder or hesitate. My local dealership diagnosed a poor spark plug connection on cylinder #3, which was causing arcing and a misfire. After the connection was repaired, the issue was resolved. My local dealership is currently working with the repairing dealership to address several minor workmanship issues, including wire clips, fittings, and missing bolts. This entire event was unexpected. There were no warning lights, alerts, or unusual noises before the initial loss of power. The only indication of a problem was the sudden power loss followed shortly thereafter by a horrific screeching noise. Thankfully, I was able to safely exit the highway and bring the vehicle to a stop. Considering I was traveling at 75 mph, the situation could have been much worse.