2024 GMC SIERRA 2500 Complaints

On 3 separate instances the past few months the truck slammed on brakes for no apparent reason. And 2 separate times the past week or so the truck suddenly and uncontrollably accelerated — first at gas a station convenience store and almost ran over old lady, secondly while waiting line on arterial entrance ramp!

I own a 2024 GMC Sierra Denali Ultimate 2500HD diesel that has been out of service for 52 days due to an oil cooler / service bulletin related failure. The vehicle is under warranty. The required replacement part is on national backorder and, as of today, has not shipped. The current estimated ship date is February 17. During this time, neither the dealership nor GMC has provided proactive communication. I have had to repeatedly contact them for updates. This extended inability to repair a critical component, combined with the lack of parts availability and communication, raises concerns about the reliability of this system and the manufacturer’s ability to support safe operation of the vehicle in a reasonable timeframe. The truck is my primary vehicle and is intended for towing and transportation. Being unable to repair it for nearly two months due to parts unavailability presents a significant safety and reliability concern.

The transmission made a loud noise, resulting in a sudden decrease in speed while driving in traffic. Felt similar to being rear ended in a collision. The lights came on in my dashboard including the check engine light. Tried driving the vehicle and it would shift erraticaly rendering un-driveable. Had to be towed to my GMC dealership for service. The initial diagnosis is an issue with the "valve body". a quick search on the internet presented several other users with this issue in this model truck with this transmission. The service department also seemed to be aware of the issue. If it is so widely known, why would there not be a recall placed on these vehicles? I'm glad I had already dropped my son off at school and that I was not on a Main Street where I could safely pull over and wait for the AAA driver.

About 2-3 months ago I had a battery swell up and start smoking and making an awful smell in my truck. I took it to dealership and was informed that I needed a new battery and it was not covered under bumper to bumper warranty or my extended warranty which I thought was ludicrous. The truck is 18 months old. It does have 50,000 miles but I have yet to see one that isn’t at least prorated for five years. So fast forward to today and the other battery starts doing the same thing except this time my lights are going crazy. Brights on and off and on and off. I get back to my camp and the battery and wiring is smoking like crazy. I towed it to the shop. It’s been in there two weeks and the only thing they tell me now is that I need 2 new batteries and that’s all they can do until I agree to pay for the other one that isn’t under warranty (because I already paid 300 to change 1st one it’s under warranty for 5 years). So I told them to do it. It’s been there two weeks and not a damn thing has been done. Not even installed a new battery. I know because I went yesterday and they couldn’t open my tailgate to get my tools out. Probably the last GMC I purchase.

Complete engine failure with no warning on major road in heavy traffic. Very dangerous situation to pull off safely. Vehicle was towed to dealer and confirmed engine is seized. Unknown cause at this time. Transmission has had valve body replaced prior to engine failure. Transmission still has shudder after valve body replacement and prior to engine failure.

Constantly having to clean the map Senor to be able to drive pickup without service emissions alerting me to clean the map Senor or my truck goes in limp mode. This can’t be normal to have to clean this so much. My truck is fairly new and should not be having these issues. Put a scanner on my GMC and the code says P122D. I got on YouTube and I found MANY people complaining about my exact problem for quite some time!

Vehicle shudders while accelerating and a constant speed from 1000-3000 rpm. Vehicle will shudder/shake for hundreds of miles at highway speed. Vehicle shakes violently going up steep grade. Vehicle shake is so consistently random it makes passengers ill. Warranty claim denied by GM after issue was recognized by technician.

Premature brake pad wear on all Brakes. All break pads worn down and had to be replaced at or before 25,000 miles. No trailer pulling and only light driving. Dealer stated rotors needed to be turned as well due to extremely low brake life.

Upon exiting the freeway, I pressed the gas and the vehicles rpm’s went up to 4K plus on a diesel engine, no acceleration. Thought maybe there was ice and had lost traction, tried again, same thing. Then a shudder, bang and pop. The check engine light went on and informed me of limited power and acceleration. There was no acceleration. Rpm’s would go to 2000 plus just to move. Got it to the dealership and parked it. Made a service appointment. They tried to put it into reverse and it wouldn’t move.

The transmission is locking up, to the point it stoped pulling, it has been to several dealerships, and they can’t find any problems, put another transmission in the truck and it’s doing the same thing, the dealer ship told us there’s nothing they can do for us!