general problems of the 2023 GMC Sierra 1500 - part 1

While traveling at highway speed during rush hour commute, the vehicle lost engine power and stalled. While coasting, I tried to restart the engine several times without success. Before coming to a stop, I attempted to get to the shoulder safely. Unfortunately, a portion of the vehicle was left partially in the lane and on the shoulder. Once I was completely stopped, I tried to put the electronic shift control into neutral so I could push the vehicle safely to the shoulder. The shifter would not allow me to shift into neutral and other override methods researched failed to work. I continued to try and restart the vehicle without success. I was in an unsafe position during rush hour commute for about 50 minutes until roadside assistance arrived and loaded and towed the vehicle. There was no warning of the issue prior to the incident. A code (p129f-fuel pump driver control module speed signal incorrect) was produced after the stall occurred via my GMC app. My vehicle was towed to my local dealership for service, but have not received the vehicle back at the time of reporting.

The vehicle is actively presenting severe mechanical symptoms that make it entirely unsafe to operate on public roads. Specifically, it exhibits a violent shuddering and vibration through the cabin when coasting or cruising at highway speeds. Furthermore, it undergoes aggressive jerking, harsh engagement, and dangerous hesitation the moment I press the gas pedal to accelerate or merge.

Model: sierra denali ultimate engine: 6. 2l v8 VIN: [xxx] mileage at most recent incident: approximately 52,000 miles safety complaint summary I am submitting this complaint to report a recurring loss-of-propulsion and engine power event involving my 2023 GMC sierra denali ultimate equipped with the 6. 2l v8 engine. This vehicle has experienced two separate incidents in which it suddenly lost power while being operated at highway speeds. During both events, the vehicle unexpectedly lost propulsion without warning and without any apparent driver input or mechanical indication beforehand. No warning lights, check-engine lights, reduced-engine-power messages, service transmission messages, or other warning indicators were displayed prior to the failure. The vehicle simply lost power while traveling in traffic. During both occurrences, I was forced to safely maneuver the vehicle to the shoulder of the roadway while rapidly losing speed among surrounding traffic. Once stopped, the vehicle would not resume normal operation until it was restarted. After restarting, the vehicle appeared to operate normally; however, the fact that this condition has now occurred twice raises significant concerns regarding the reliability and safety of the vehicle. Safety risk this condition presents a significant and immediate safety risk because sudden loss of propulsion during highway operation can leave the driver unable to maintain speed, safely merge, maneuver, or avoid surrounding traffic. The unexpected reduction in speed creates the potential for rear-end collisions, loss of vehicle control, or other traffic accidents, particularly when operating on high-speed roadways. Because the vehicle provided no warning before losing power, there is little opportunity for a driver to take preventive action. Additional information • vehicle: 2023 GMC sierra denali ultimate • engine: 6. 2l v8 • VIN: [xxx] • approximate mileage: 52,000 miles • number of incident information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 55.

The truck side toy down shift and the accelerator was very high…. When I was going to park the reverse was not shifting….

I was driving my family on the highway and my truck completely shut down. The screen flashed a warning and it slowly started decelerating. Thankfully I was able to make it to the shoulder of the road safely. Engine failure was a known safety issue with my model of truck, but I completed the l87 engine loss of propulsion safety recall testing on 9/18/2025 and was assured my engine passed the testing and was not at risk for engine failure.

Upon accelerating on the freeway, rear wheels locked up completely almost causing me to hit multiple vehicles. Was repeatable and was able to record the event. Manufacturer claims unable to reproduce and bring back if it happens again. No lights were set.

The transmission control module failed. The dealer said a I a high voltage alarm signal code. This was the diagnostic inform received from the dealership service department. Primary]: mdiag : misc. Vehicle diagnosis. Check engine light illuminated and getting message for service transmission, unable to shift. Please check and advise * repair items per diagnosis: found p07b4 stored in system. Verified wiring ok to gear shift control module. Si states if wiring good to replace gear shift control module and if code resets to replace ecm. Recommend starting by replacing gear shift control module the truck would not shift or go into gear at all. This was concerning because the transmission could have stopped shifting while I was driving myself and my children around. This warning light came on while I was driving on the highway. My vehicle has about 58,000 miles on it and is still under powertrain warranty. But the dealership is saying this repair isn’t included.

[xxx] [xxx] phone: [xxx] vehicle information: year: 2023 make: GMC model: sierra denali ultimate engine: 6. 2l v8 VIN: [xxx]: mileage: approximately 52,000 miles background: I previously had the engine serviced under a gm recall campaign related to known 6. 2l v8 engine concerns. Despite that repair, the vehicle has since experienced two separate highway-speed loss-of-propulsion events. Complaint the vehicle suddenly lost power while being driven at highway speed. No warning lights, check-engine lights, reduced-engine-power messages, or transmission warnings appeared. In both incidents, I was forced to coast to the shoulder of the roadway. The vehicle would not resume normal operation until it was stopped and restarted. This condition has now occurred twice. Safety concern the sudden loss of propulsion during highway operation creates an immediate safety hazard and increases the risk of collision due to the inability to maintain speed with surrounding traffic. Requested NHTSA action 1. Record this complaint as a repeat loss-of-propulsion event. 2. Evaluate whether similar complaints exist involving 2023 GMC sierra denali ultimate vehicles equipped with the 6. 2l v8. 3. Consider this complaint in any current or future investigations involving loss of propulsion, stalling, engine failure, or powertrain concerns. 4. Review whether vehicles previously repaired under gm recall campaigns continue to experience similar failures. [xxx]: update – vehicle disabled and awaiting engine replacement since filing my initial concerns regarding repeated loss-of-propulsion events, the condition of my vehicle has significantly worsened. During the dealership's inspection and test drive, the engine reportedly failed and locked up. The vehicle could not be restarted and required further diagnostics. On June 20, 2026, I received a text message from the dealership that the required engine parts remain on backorder information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

I was driving down the road at 55 mph on 4/12/2026 and had let off the gas for a 45 mph zone when I experienced a violent downshift of the transmission that squealed the tires momentarily and felt like someone had hit me from behind. It startled me and caused me to lower my speed down to 20 mph. I continued driving to my destination and when I let off of the gas doing 45 mph for a slight curve I had another violent downshift that felt again like someone hit me from behind. I contacted a GMC dealer on 4/13. 2026 to see if there was a recall on the transmission that I wasn't seeing online and was told no. I described what I experienced to their service department and was told to flush out the transmission fluid and replace the filter. I did experience another bad downshift at a slower speed (about 25 mph) on 4/13/2026. There wasn't any warnings or lights that came on when these three incidents occurred. When looking online I did see there was a similar recall for 2020-2022 GMC sierra's where customers were experiencing similar violent transmission downshifts and am wondering if this issue is affecting more than just those three model years.

On March 13, 2026 I purchased a 2023 GMC sierra at4 pickup with 3. 0 diesel engine. While driving on a state highway in a 35 mph zone I started to accelerate as the speed zone changed. The truck suddenly had the rear wheel lock up for a brief time about quarter to half second then the truck proceeded on. This happened as the transmission was downshifting. Then on or about March 24, 2026 I was using the same truck and towing a 4,000 pound enclosed trailer. This trailer was hooked up within all recommended hookup requirements. In a 225 mile trip I experienced the same rear wheel lock up happen 4 random times during the trip. Once this happened at 65 miles and hour had there been snow or ice on the highway the truck may have crashed. This lock up happened while using the truck in tow haul mode. Two times it happened while the truck was being towed with cruise control active and two times it happened while not using cruise control. Truck was brought to authorized gm dealer and inspected and truck had no stored codes from transmission related issues. Dealer blamed this for using cruise while towing. I informed dealer this happened while not using cruise as well. Was told to turn off adaptive cruise when towing. I was unable to find anything in the GMC manual regarding not using cruise while towing. This appears to be an issue with the valve body in the transmission and customer explained this to the dealer but they denied this claim. When these quick moment lockups happen no codes or engine lights show everything on dash appears normal. Customer is bringing truck to another gm dealer to be tested and examined.

My 2023 GMC sierra has 60,571 miles for a while now while driving the transmission slips and slams into gears. Recently driving with my kids in the car on highway going 70mph the back brakes locked up multiple times, so scary and dangerous while driving. I now currently have a code p-0747 in the system.

While driving the vehicle I received dash warnings of temperature rise. Pulled over and saw a large coolant leak coming from right side of engine compartment. Towed to dealership. Dealership informed me that coolant hose coming from heater core was routed by the manufacturer so that it rubbed on the frame. Dealer indicated problem persists on all vehicles and no given, other than replacing the hose and not remedy the problem. New hose will be in contact with frame again, causing inevitable where and breakage. Dealer did not cover under warranty nor did they offer solution for repair other than replacing those hose.

Drastically reduced power on highway resulting in reduced acceleration due to code p0198 engine coolant control valve position sensor. Required me to drive at reduced speed on highway to get to dealer. Safety issue.

Incident summary: on 2/2/2026, my vehicle was serviced under safety recall 25v-274 at an authorized GMC dealership. The service technician performed the mandated diagnostic protocol (including the picoscope test) and informed me that the engine had "passed" inspection. No internal components were replaced; the remedy was limited to an oil change to a higher-viscosity oil (0w-40) and a new oil filler cap. The failure: approximately 48 hours after this "successful" recall remedy, the vehicle suffered a catastrophic engine failure while in operation. The engine failed entirely. The vehicle lost all propulsion while in motion, creating an immediate safety hazard for myself and other motorists. Diagnostic and risk: the failure has been confirmed by a GMC dealer, who subsequently performed a full engine and radiator replacement. In the 48-hour prior to failure, there were no warning lamps or symptoms; the vehicle had just been cleared by the manufacturer's own diagnostic tools as safe and free of defects. Systemic concern: this incident demonstrates that the current diagnostic protocol for recall 25v-274 is insufficient to identify terminal manufacturing defects in the connecting rods and crankshaft of the l87 6. 2l v8 engine. The "remedy" of higher-viscosity oil failed to prevent the exact catastrophic loss of propulsion the recall was intended to address. The replaced engine is available for inspection upon request by the NHTSA office of defects investigation.

While entering the freeway at approximately 45 mph not towing the rear wheels locked for a second, truck went into the limp mood, and dash said reduce speed, service transmission. Dealer pulled codes, p0700 and p0747. . . The order says cause document #6998510. "replace spacer plate, check balls and valve. " correction: dtc p0747 set dealer told me the put the new updated valve in but I don't see that on the repair order? I asked about the gm extended warranty ( I think it's 10 years, 150,000 miles). They said it didn't apply to my vehicle?.

Vehicle: 2023 GMC [model], black widow package, 6. 2l l87, 41,078 miles recall: 25v?274 / gm [xxx] ; recall remedy performed by marty’s GMC (kingston, MA) on 2025 -11-12; oil changed per recall procedure post?remedy symptom: intermittent knock starting ~01 - 2025 / about two months after remedy incident: Jan 23, 2026 — engine seized / loss of propulsion while driving; stranded on highway off?ramp; vehicle impeding traffic causing dangerous conditions. Codes: obd scan by passerby indicated camshaft position sensor / correlation error (exact code not captured) crash/injuries: none current status: vehicle at marty’s GMC since Jan 23; not diagnosed as of Jan 29; GMC case #88159466 safety concern: sudden loss of motor power in traffic after recall remedy on Friday, Jan 23, 2026, while my daughter was driving, the engine seized / the vehicle lost propulsion and stranded her on a highway off?ramp. The vehicle was impeding traffic and had to be moved. It restarted briefly and was moved to a safer location but still impeding traffic. A motorist scanned the obd port and reported a camshaft position sensor / cam-crank correlation error (exact dtc unknown). No crash occurred and no injuries occurred. The vehicle has been at marty’s GMC since Jan 23, 2026 and as of Jan 29, 2026 it has not yet been diagnosed. I opened a case with GMC customer assistance (case #xxx). This is a safety-related loss-of-propulsion event occurring after the recall remedy was completed. Information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

Driving at 35 mph in traffic and the rpms started to increase to 3500rpm and vehicle started to slow down inevitably putting me into reduced acceleration. . Limp mode. Truck would not shift into reverse either once I could safely merge out of traffic and put into park. Very very dangerous and scary situation.

I had the truck inspected for recall n25249400 on August 11, 2025 with 24,610 miles. It passed the recall inspection and the dealer changed the oil to gm recall recommended oil. On January 18, 2026 with 28,275 miles, the engine seized while on a major highway. The truck lost all power and just turned off amd would not start or turn over. The vehicle was towed by the police due to the vehicle being in a dangerous spot in the middle of a lane on the highway whi h I had to pay out of pocket. January 19, 2026, the gm dealer confirmed that the truck needs a new engine due to the recall defect. They said that they had just ordered a new engine, but does olnot know hpw long ot will take to get and then install. The dealer is unable to provide a rental vehicle which means, I can't work!.

While traveling on a major route, the truck just turned off while driving. The truck was stuck in the middle of a two lane major route. Truck would not start or turn on. I was unable to put hazards on or put the truck in neutral. The engine siezed due to the gm recall. After having the engine replaced by a certified gm dealership, a few days later the throttle body stopped working. Again, keeping me stuck. Certified gm dealership had to replace the throttle body.

Vehicle passed initial inspection and had higher viscosity oil installed. After driving for the past six months I noticed a burning oil smell inside the truck. The smell gets intense at times especially during highway driving. The ow-40 viscosity oil is causing high fumes within the cockpit. Please consider checking this issue out during your added investigation into the l-87 engine failure. I shouldn't have to drive with the windows down but I do. I will have the truck inspected during my next oil change next week.

The contact owns a 2023 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the vehicle shuddered while in first gear. The contact stated that the transmission sounded strained and shifted rough before slamming into gear. The vehicle was taken to the dealer; however, no cause for the failure was found. The dealer diagnosed the vehicle and determined that the vehicle was oversteering while turning to the right. The dealer replaced the valve and torque converter. On another occasion, while driving at an undisclosed speed, the vehicle accelerated independently. Most recently, a burned transmission fluid odor was coming from the front of the vehicle and entered the cabin through the a/c vents. There oil stains found on the ground on several occasions. The vehicle was taken back to the dealer and the valve body was replaced, the fluid levels were checked, and the transmission filter was replaced; however, the failure persisted. The contact called the dealer, and the dealer towed the vehicle. The dealer determined that the oil cap was loose. The vehicle remained at the dealer unrepaired. The manufacturer was made aware of the failure, and a case was opened. The failure mileage was 8,496.

On 9/27 the engine light went on and message transmission may not shift.

This malfunction is ongoing and the dealership cannot fix the problem. The first time it happened in September 2025. I was driving down the road and the gauges started to go crazy. The screen on the dash said reduced acceleration. Then it said service esc. Then it said service traction control. It would not let me go over 40 mph. I took it to the dealership and they told me I needed a valve body replacement. They installed the valve body and that did not fix the problem. It happened again and said reduced acceleration took over forcing me to pull over on the side of the road. The GMC dealership said to bring it in again but they could not reproduce the malfunction after driving for a week. It happens randomly. The third time this happened I was traveling up interstate 24 at about 70 mph. There were semi trucks around me when the malfunction happened and my acceleration and speed was reduced throwing the rpms as high as they would go, and I was almost hit by a semi trying to move out of the way and onto the shoulder of the interstate I tried to accelerate to get out of the way of the semi truck but could not. I had to swerve over almost losing control of my truck. I informed the dealership that this had happened again and they asked me to bring it in. I did. They told me they were going to clean corrosion off of ground wires, and that should fix the problem. It did not. This keeps happening and I feel that the vehicle is not safe to drive. I do not know when it will happen again. I travel for a living and I feel the vehicle is unsafe to operate.

Driving on highway at 60mph while towing a travel trailer and the rear tires briefly locked up, the check engine light came on with an explanation mark (!) and the dash displaying a major warning. The truck went into "limp mode. " computer code read p0747. Dealer confirmed issue and replaced valve body. Truck had 22,000 miles. Appears 2023 vehicles should be added to the original recall for long-term warranty protection.

At 12,018 miles on my 2024 GMC Sierra 1500 I experienced a rear wheel lock up. I have 4wheel drive capability but I had the truck in rear wheel drive only. Thankfully I was not going fast at the time. I was going between 35-45 mph when experiencing the lock up. As I was going down a straight away, I experienced a rear wheel lock up of my 10l80 transmission. My tires were squealing like crazy. I pulled off onto the side of the road. After shifting to reverse and then park and then drive the problem corrected itself. When I brought it into the dealership, they could not find anything wrong with it. Additionally my trucks software was up to date and not lacking any updates. I don’t drive this truck very far and only drive about 150 miles a week. A rear wheel lock up of this magnitude at this low of miles is concerning. I’m not rough on the truck by any means. It’s more so a family vehicle than a hauler. I have got the truck serviced 3 times since I bought it for regular maintenance so that’s not an issue either. There were no warning indicators that this problem was occurring when I experienced the rear wheel lock up. This could have resulted in a collision with vehicles around me if I had not been aware of what was occurring.

Truck will down shift and transmission will slam, super hard. Feels like I hit something. Almost causing accident. Dealership refuses to service my truck or even take a look at the transmission because "its not broken yet" in their words " it needs to fail before they can service it or even look at it, because they wont get paid. " I have expressed my concerns about this safety issue and at this point they are being negligent. My truck is a 2023 GMC Sierra 1500 with 3. 0 duramax . Still under warranty with only 35k miles.

While driving on the freeway, 65 mph, I went to accelerate as vehicle was slowing down with no response, looked at dash and noticed vehicle was in neutral, with a message saying “restart vehicle to shift” thankfully I was able to get over a few lanes to pull over and restart vehicle. Very scary incident while on a busy early morning commute to work.

Vehicle was in for routine service, oil change and tire rotation. Per the published engine recall bulletin [manufacturer recall number n252494000] the recall directs the technicians to check for a dtc and if not present to drain and replace filter and oil using 0-40w oil, to replace the oil filler cap with new oil specification labeling, and provide a corrected page for the owners operating manual. All very simple steps. There is absolutely no reason for this check and service not to be performed during routine maintenance. Gm is dragging their feet on performing a critical recall and should be held accountable for slow walking this recall. Servicing dealer claims they had zero 0-40w oil in the entire dealership. I can go to walmart and get cases of this oil. Replacement filler caps, which must be replaced can be quickly produced by the tens of thousands if desired, which apparently is a very low priority for gm. Servicing dealer was heritage GMC, rockwall, TX. Desired outcome is to require completion of all outstanding recalls if the vehicle is presented for servicing regardless of reason. Further, to specify a definitive timeline to complete any outstanding recalls and have that information communicated to each owner. Manufacturer recall number n252494000 has not been completed at this time.

My 2023 GMC sierra at4 with the 6. 2l l87 engine is showing signs of premature engine issues despite passing the recall inspection. I hear persistent lifter chatter, which is known to be a precursor to catastrophic failure in these engines. I no longer feel safe driving this vehicle due to the known defect with the crankshaft, rods, and valvetrain. Gm issued a recall, but it appears to be incomplete and does not address the underlying issue in many vehicles, including mine. I am worried about sudden engine failure and safety while driving.

Driving on the highway under normal driving condition, my check engine light came on and said service transmission. This then put the truck into "limp mode" and I was stuck going 60mph in a 75mph zone. Dealership scanned and found that the coolant sensor control flow valve is faulty. This part is in such demand for these vehicles that it is unknown when the part will be in.

Tailgate can open by switch located at storage area in console. It can be easily bumped then tailgate will o pen without driver receiving a warning light or dashboard message. If this occurs, and it did with this vehicle, any cargo could potentially fall out causing accident to vehicles following. Additionally, the powertrain (transmission) is a known problem for failure. If such a failure occurs the rear wheels can lock up causing accidents/injury to driver and others. Note- this has not happened to this vehicle yet but does cause concern for it happening and gm not doing a recall.

Vehicle's 10 speed transmission on numerous occasions has locked the wheels at high rates of speed on the highway, causing the vehicle to veer across several lanes and almost crash. Vehicle will not always engage in drive selection causing a filed accident while trying to go from reverse to drive.

I was going camping and pulling a small 20 ft trailer with my spouse and 4 young kids in the car when the truck stopped accelerating and would not go over 30 mph on the freeway and the fan started running. There was no warning light on the dash. I was then stranded 2 hour from home with my kids in a gas station parking lot and had to have the truck and trailer hauled home.

I was driving and without warning the engine stopped. Luckily I was on a neighborhood street and was just left in the middle of the road without incident. However, if I was turning on a left into traffic or on a major highway I would hate to think what would of happened. Again, this motor gave zero indication it was going to fail. It did not knock etc. Truck is currently at the dealer waiting for a new engine. This recall will lead to fatalities if others fail in this manner.

My vehicle has the 10l80 transmission. It experienced shuddering as well as several rear wheel lock ups at highway speeds. The vehicle is now out of service, since may 19 2025. I have been told there is no answer to shipment of replacement parts.