general problems of the 2020 GMC Sierra 1500 - part 1

My 2020 GMC sierra has had poor gas mileage problems I have taken it to gm a few times with them not able to dind anything wrong through diagnostic. A couple years later my horrible gas mileage came back and service ecs and stabilitrack message came back on and disappeared. I spoke to another shop and they advised me its the dfm lifter issues that everyone has been talking about. So the shop performed the well know fix and has fix the issue. A month after now the valve body gave me a p2817 code showing that the solenoid is stuck in the off and was also advised that this is a know issue being addressed. Currently the truck is in the shop. When is enough enough with all the issues across the nation whwn is gm going to make it right.

Transmission 10l80 stuck solenoid truck has hesitation delayed shifting. And will not shift after certain gears.

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.

Safety recall n242454440 momentary rear wheel lock-up was issued for 2020 to 2022 GMC Sierra 1500 but mine is not included. I drive a 2020 GMC Sierra 1500. It is experiencing harsh shifting and now there is a feeling in the rear wheels like they are trying to get stuck or hang up. Why is my truck not included?.

I heard a ticking noise coming from the engine compartment. I took it to the dealership that I purchased the truck from and that have been using consistently for service. I was told that the noise was coming from a lifter on the driver's side of the engine and, on further investigation, it was determined that the camshaft had been damaged. I was told that it could seize up as I was driving and that my safety and those with and around me would be at risk. At 85,000 miles, the engine had failed and would have to be replaced. There was no prior warning or no check engine light and the vehicle has been in for oil changes and all maintenance at the dealership. The new engine cost me $15000 including diagnosis and towing.

My doors will no longer lock or unlock, using the key fob or the lock/unlock buttons in the vehicle. This is a widely known issue for GMC trucks, once you search for it. At around 50k miles, the door actuators just quit working. So, if I have kids in my truck, I can't unluck the doors to get them out unless I climb through the truck, and have to manually do same to lock the doors to drive with kids in the car. There isn't a key hole for the back doors, so this can't be done at all outside the car. The doors are supposed to automatically lock when the truck is put in gear. Mine won't lock even when I push the button to lock. I just had this confirmed at the dealer. I also spoke to GMC and was told that it wasn't their responsibility. This is a genuine safety issue, and happens on these trucks a lot.

My multipro tailgate on my 2020 GMC Sierra 1500 unlatched while a trailer was attached and backing up said trailer. The trailer jack post proceeded to buckle the upper part of the tailgate assembly causing extensive damage resulting in over a three thousand dollar repair bill. If the tailgate had released while a child was in close proximity, serious injury may occur. The tailgate has inadvertently released twice in the five plus years I have owned it, the first time as I was traveling down a highway at over 60 mph. This could have endangered a vehicle to my rear if cargo had been released on to the road. I have reached out to a local dealership for repairs and assessment, no real way of troubleshooting something that has happened twice in five plus years. The scan did not show any codes. The info center does notify you if it is released but not before it takes place and after the fact may be too late in some circumstances as it was during the second occurrence. There has been a recall on 2500 and 3500 models with the exact same tailgate but not the 1500 models. 820k vehicles affected but not on the 1500's.

1. The vehicle’s emissions system is malfunctioning, specifically the ecm (engine control module) related to the exhaust emissions system. The diagnostic trouble code is p2c7a, indicating the system is not performing as expected. Key components such as the nox catalytic converters and diesel particulate filter have been repeatedly replaced, but the issue persists. The vehicle and all replaced components are available for inspection upon request. 2. The malfunctioning emissions system has led to an exhaust leak that allowed exhaust gases to enter the vehicle’s cab. This creates a hazardous environment for both the driver and passengers, exposing them to harmful exhaust fumes. In addition to reduced engine performance, poorer fuel economy, and emissions non-compliance, this exhaust leak poses a serious safety risk by compromising the air quality inside the vehicle. Prolonged operation under these conditions could lead to adverse health effects and further mechanical failures that impact vehicle safety. 3. Yes. The dealership has diagnosed the problem multiple times. The emissions components have been replaced under warranty on two separate occasions. The dealer attributed the fault to fuel quality; however, fuel distributor debunked these claims. 4. The vehicle has been inspected extensively by the dealership with invoiced repair work replacing key emissions control components. 5. The check engine light and service engine soon (ses) light have been illuminated with the diagnostic code p2c7a since the initial identification of the problem which started 3jun24.

1. On 05/9/25, the exhaust emissions system malfunctioned, triggering diagnostic trouble code p2c7a (exhaust emissions system failure). This repair, the seventh attempt since June 2024, addressed the same recurring emissions issue previously involving replacements of components such as the nox converter (02/18/25, 03/13/24) and egr valve (02/18/25). The vehicle is available for inspection upon request. 2. The p2c7a failure risks limp mode, reducing vehicle power unexpectedly, which is hazardous on highways, especially while towing. Exhaust emissions system malfunctions release excessive pollutants, posing environmental and health risks to others. 3. Yes, the p2c7a code was confirmed by dealer during the 05/9/25 repair, following prior confirmations (e. G. , 03/31/25–04/05/25. 4. The vehicle was inspected by young Chevrolet-Cadillac during multiple repairs (e. G. , 03/31/25, 05/9/25). 5. Yes, the check engine light and onstar emissions alerts appeared prior to the 05/9/25 repair, first noted ~June 2024 (p2c7a onset). Exhaust smell and reduced fuel economy were observed intermittently. Symptoms persisted post-03/31/25 repair, leading to the 05/23/25 service.

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

6. 2 liter engine fail- replaced at new cost, 20,000 miles later another 6. 2 engine failed. Unable to get new engine due to GMC finally recalling the engine. My VIN is not included in the recall. I now have no vehicle to drive but still have a loan to pay.

Shift to park message appears when in park and engine is turned off. Transmission control had an internal circuit failure. Park not fully engaged and vehicle could roll. Problem confirmed by dealership. Prior recalls for earlier GMC models but not my year.

Water entering from the rear window causing rear seats and roof hard cover to get wet and cause a wet odor (humid). 2020 GMC 1500 at4.

Vehicle was going in for warranty recall; however, I requested they look at the def system as my def gauge would bounce between full and empty; along with, alert me of going into limp mode. Gm maintenance updated the recall and noticed that the def tank sensor failed and required to be replaced.

I have taken my vehicle to 3 seperate mechanics (GMC, aamco and independent). They all agree that my valve body inside the transmission must be replaced. The problem is that valve bodies are on a national back order and cannot be fullfilled for months, putting my transmission at risk for further failure. Reading online forums, there are many GMC owners facing this same issue. The mechanics at GMC are requesting that I change out my entire transmission, since that will be a quicker solution than waiting months for that valve body. Now, I am being told that they are having difficulty locating an original manufactured transmission. This puts me in a serious bind because my truck is my only vehicle and there are no valve bodies or transmissions to fix this issue. My truck is only a 2020 and I just surpassed 100k miles. There were no dashboard warning lights that indicated my trucks problem. Only the fact that my truck is shuddering when shifting gears and that a diagnostic tool had to find the source of the problem. This problem started about 5 months ago and has progressivly gotten worse.

I purchased a 2020 GMC denali Sierra 1500. My oil light has came on twice and I have taken it into the dealer and dealer has said that that's normal. That car loses oil. I'm retired so I do not utilize the vehicle every day I think since I've had the vehicle I've put on several thousand miles very very low mileage put on. And I'm being told that I need to check the oil basically before I take the vehicle anywhere. During the first time when I bought the vehicle in when the light came on the mechanic said in the paperwork from GMC service that my engine oil was extremely low. This last time that I did take it in, I have some type of mechanical background, so I pulled the dipstick out and it was halfway full with oil. I took a picture of that dated the picture and said I took it in before service while when I took it into the service department of course when I came home, they said that everything's fine and so on and so on and that didn't sit well with me. So I went ahead and let the car settle. Let the car cool down several hours later. I went ahead and checked the dipstick and the dipstick was full. They went ahead and put oil into my vehicle and told me that everything's fine. And I have noticed that there are lawsuits out in regards to oil consumption issues on these vehicles. When somebody spends the amount of money they spend for these vehicles we should not have to be checking the oil almost every time we drive it. I've had multiple vehicles on 50 years old and I've never had to check the oil like it was 1914 before you go on a trip or even drive your vehicle. I am not trying to blame the dealership only being told that everything's fine but GMC the company needs to rectify this problem because there is going to be a time that people are going to forget about the oil and burn up an engine and then you're putting them out thousands of thousands of dollars because of a mistake GMC made they're trying to cover it up as you see with the current recall in regards t.

Rear window is leaking top coners from seal or plastic creating black mold inside of truck.

1. Lane keeping assistantance: the green vehicle indicator on the dashboard will disappear and stay off while driving. When it is off, it is unsafe. 2. Parking collision warning: the front and back sensors will disappear and become nonfunctional while driving and parking. Sometimes they activate for no reason as well. 3. Both exterior mirrors: after starting the engine to drive off , both exterior mirrors will lower automatically from my setting. After the truck is started and driven off, they must be rest again.

Shift to park error message to turn vehicle off when already in park.

There has been a recall on the 2020 Sierra 1500 for the driveshaft which causes shuddering and vibration which my vehicle is exibiting but my VIN is not on the recall list.

My truck 2020 GMC Sierra 1500 at4 denali is not working properly since July 2024. I took it to 2 different dealership to get a diagnostic and I finally ended doing the repairs for brake issues. I have been towed 6 or more times and almost experienced 2 car accidents since I drive the truck after the supposedly repairs where done but I ended stranded again with no brakes. The dealership has repair the truck 3 times but im still getting sevaral codes the fact that I had to pay out of pocket and have to deal with this and expose myself to danger and my family in driving a vehicle that is no safety condition its absurd. I call several times the recall gm hotline and I was told GMC 1500 are included in the recalls just not the at4 and I have a family member with the same truck and same issues she ended up trading in the truck recently since she kept experiencing the same issues over and over again just like me.

No warning; picking up child from daycare. Went to depart daycare when my dash lit up like a christmas tree with various errors, alerts, warnings; along with, not being able to start. Had to be picked up by spouse and get the truck towed to the dealership for maintenance. Maintenance tech discovered that the grounding straps for the truck needed to be replaced / resulting in a complete electrical failure of the vehicle.

Engine light came on while driving / aligned to transmission temp sensor error and brake sensor gm maintenance was able to diagnosis that the temperature loop coolant pump had failed and needed to be replaced.

Transmission shurtting, jerks, and vibration, bad torque converter bubble and pelling paint. It feel likes engine is lossing power.

The rear window was leaking a substantial amount of water soaking the back seat. Had the service bulletin done, which did not work. Then under further inspection found cracks in the rear power window track. Dealer told me gm would not cover replacement because it was out of the 3 year warranty. Then was told it would cost me 1200 dollars to replace. Gm should cover this because it will lead to black mold.

Rear window leaks due to failed sealing at the factory. If not fixed will ruin interior components and possibly rust. Yes no no.

Rear window leak causing whole inside back to get soaked. Have paid hundreds of dollars to have sealed didn’t work. New window didn’t work it still leaks. It’s going to cause interior to mold and body to rust. Dealership and glass business both say it’s body issue and they have seen many GMC and chevrolets with this issue. Google show 1000s with same problem.

Vehicle drop in gear / down shift while driving on the highway. Went from 75mph down to 55mph due to high rpm revs.

Once vehicle is put in park, the control panel comes and reads, “shift in park and radio and head lights stays on as well”. I exit the vehicle and it continues to display the mention above. I’ve restarted the vehicle and put it back in park still the “shift in park”, stays on. I exit the vehicle and monitored the vehicle for approximately 5 minutes and finally turned off. This never happened before, I’m afraid it may stay on one of these days and run the battery down.

Vehicle engine went out on truck.

The rear sliding window leaks water inside the cab every time it rains. With water getting into the cab the issue of mold has begun and that could be a serious factor to any children or adults that ride inside the cab of the truck. There is also rust issues that are notable under the rear seats of the vehicle. Water inside the cab can also interact negatively with any electrical components of the vehicle. I tried to get ahold of the dealer and they always say they don't have time to get my truck in. I have read that this has happened to other vehicles that are the same year and model and they just fix it with caulk which does not seem appropriate for a almost new vehicle. The vehicle has not been inspected. There were no warning lamps prior to this issue. A possible symptom was that my back up camera stopped working for a day right after a rain.

It was fine and we drove to our neighbor, parked about 15 mins. When we started the truck to turn back, the steering was super heavy, with 2 messages pop up on the dashboard: services esc, and service power steering drive with care. Tried several times to re-start the truck, it's keep the same. In our neiborhood, parrot tulip view, pflugerville, TX 78660. Raining all night, not sure if it's related to the weather.

When stationary and preparing to start vehicle intermittently see "service steering column lock" message appears and disappear once vehicle is started. This was previously supposed to be addressed with service bulletin 20-na-21 however being told by service department that vehicle has all current updates applied a year ago, including the one that should of addressed the issue. Told that the vehicle history shows records of past "loss of communication to dic" but as they can't immediately reproduce no action was taken.

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.

Rear window (the one that faces straight back towards bed of truck) is leaking… haven’t taken it in to dealership for repair because I’ve exceeded mileage so truck is no longer under warranty… not sure how long it’s been leaking but I’ve recently noticed that water stains (runs) on the inside of this window after rains, washes, etc….