2020 Gmc Sierra 1500 Electrical Problems

Your engine shut down suddenly while driving on the freeway with no warning, and you noticed a burning smell. When a mechanic examined it, they found a camshaft issue and heard knocking noises—the engine would only run briefly before shutting off again. You'll need to replace the entire engine due to the camshaft failure and internal engine damage.

You discovered that the odometer mileage on your 2020 GMC Sierra 1500 doesn't match the vehicle's history. When you purchased the truck, the odometer showed 75,000 miles, but the Carfax report indicated 175,000 miles at the time of registration. This suggests the odometer reading may have been altered or the mileage history is inaccurate. Resolving this will likely require working with your state's motor vehicle department and potentially consulting with a lawyer regarding the private sale.

Your backup camera displays an excessively bright image at night, making it difficult or impossible to see what's behind your truck. You've researched online solutions without success, and the dealer was unable to help despite multiple reports of this issue appearing online. The fix may involve adjusting camera settings through the infotainment system, updating the camera firmware, or replacing the backup camera unit.

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

The morning of December 12th, 2025 I used my vehicle to transport my daughter approximately 5 miles round trip from our home to drop her off at daycare and then I returned home. I used my front and rear defrost elements to expedite removal of heavy condensation which had formed on all windows overnight. This was approximately 7 AM. I parked my truck in the driveway and went inside until approximately 11:45 AM when I went to leave in my truck and noticed the rear sliding window had shattered. The window shattered and distributed tempered glass fragments all over the inside of the cab. Only approximately 10% of the window remained intact. I then reviewed the security camera footage from my driveway and discovered that the window failed entirely on its own with nothing hitting/striking/touching the window, nor any humans or animals in the vicinity. I attempted to take the vehicle to a GMC service department this morning (Dec 13) but due to their demand to keep the vehicle for 2-3 days to investigate yet unable to provide a loaner vehicle, I was unable to leave the vehicle in their possession and returned home. I plan to continue to contact GMC dealership service departments in hope I can find one which can provide a loaner vehicle, as I will need transportation to and from work in the coming days. I do have video footage of the incident although I am unable to add it below.

The contact owned a 2020 GMC Sierra 1500. The contact stated that after the vehicle was purchased and while driving at an undisclosed speed, the check engine warning light illuminated. The dealer was contacted. However, the check engine light turned off, and the dealer refused to inspect the vehicle. The contact stated that while driving at an undisclosed speed, the vehicle jerked and the check engine light illuminated. The dealer was contacted. However, the warranty had expired, and the dealer refused to inspect the vehicle. The manufacturer was contacted, and the contact was offered a five-hundred-dollar coupon. The vehicle was taken back to the dealer. However, no cause for the failure was found. The contact stated that an unknown part was replaced. The contact stated that the failure persisted. The contact stated that while turning on the engine, the contact's sister informed him that smoke was emitting from under the hood. The contact turned off the engine, opened the hood, and noticed that all of the wires were melted. The contact splashed water on the wires. The contact checked underneath the vehicle and noticed that the plastic that was burnt was leaking residue. The vehicle was left at the residence where the contact's mother lives. The next day, the contact noticed that the front windshield had shattered due to the heat from the burnt wires. The insurance company was notified and referred the caller to take the vehicle to be inspected. The vehicle was towed to a collision center. The contact was informed that the vehicle had a factory defect. The vehicle was not repaired. The manufacturer was notified of the failure. However, no assistance was provided since the warranty had expired.  The failure mileage was approximately 32,000.

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

Woke up one morning and the entire back seat, entire truck flooring was soaking wet. Got it to Gerber collision in El Reno, Oklahoma. They said that the back window had a crack in it. My insurance said it is a mechanical issue on the sliding back glass and they do not cover such issue. Also want to turn in that the transmission in this truck had to be replaced two week prior to this incident. The truck only had 118,000 miles on it. Safe to say that this 10 point GMC diesel truck is a nightmare and the entire truck is a hazard. They need to take these truck off the market.

Power Steering works sometimes and then stops Trailer Break system issues

The contact owns a 2020 GMC Sierra 1500. The contact stated that while driving on a main road at 40 MPH, the vehicle lost automotive power, causing the vehicle to shut off. There was no warning light illuminated. The vehicle was towed to a local dealer where the vehicle was diagnosed, and the contact was informed that the engine wiring harness was faulty and needed to be replaced. The vehicle was not repaired. The manufacturer was not notified of the failure. The approximate failure mileage was 80,000.

While driving my vehicle it began down shifting harder than normal (at various speeds and road (highway, city and dirt road)); along with a noticeable burning smell after every trip. GM Maintenance personnel discovered that the wire was chafed and arching / catching on fire underneath passenger side resulting in the burning smell and the wiring issue aligned to the transmission. Personnel took a video and provided to me as evidence of the fire / smell; however, that was on their official GM app so i was unable to download

After repair got a few miles down the road and noticed the volt meter jumping back and forth between the white lines. Line would slowly go up to max line and then slowly drop back down to lower limit and continue to go back and forth. This was very concerning to myself and i was waiting for something to fail while driving. Got about 10 miles away and was to concerned / returned the vehicle Informed by GM Maintenance tech that this is what / how the vehicle is designed and that it is the operating within its parameters. I expressed that only time i noticed something like this was prior to an engine light / electrical failure; however, maintenance team expressed GMs stance that it is operating within tolerance.

I was driving about 45 mph when the vehicle started to brake on its own. Message center said "Brake Failure max speed 62 mph". I had to move the vehicle, so I continued forward. It was still trying to self-brake, i decided to stop and turn ignition off so computers could re-set but I had no brakes. I had to stand on brake pedal to get it stopped. Turned ignition off and restarted. The problem was gone, but it happened again 2 weeks later. Took to dealership where purchased and they said it needed a computed recalibration. Something I didn't know about. They charged me $200 to recalibrate the computer. My issue is the danger of not having brakes, not the $200. How many similar vehicles could this happen to?

I was about 45 miles or so from home on [XXX]. As I left a business my truck went about 100 feet and the engine stopped working . No warning. Truck was towed to a GM dealer in Wilmington Il. It was determined the cause was due to the wiring from the engine ECM that was run over the top of a very sharp plastic mounting bracket for the ECM. The wire had been cut because of the way this was done at the factory. In addition the fuel pump also needed to be replaced . At the time of this, the truck had 39,140 miles on it. I had no warning this was about to happen. No check engine light went on , etc. Most of my route home is on the highway . Had this not happened on a side street , I would have been involved in an accident. I ended up paying $865.42 plus towing for this repair I should not be paying for. The people at the GM dealer told me this has been happening on numerous GM pick up trucks. This is NOT a maintenance issue or an isolated case. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Had GMC (Leominster, MA), perform the safety recall for the transmission on my Sierra. This is the one for the rear wheel lockup that requires a software update. My battery was completely dead after the vehicle sat for a week. No accessori s plugged in, and it's a 6 month old battery Battery tested fine and is charging now, but it appears the CPU never fully powered down after the software update, resulting in needing multiple jump starts and 3+ hours of run time to charge the battery enough to turn over on its own. I can see this being a safety issue in relation to the Auto-start, because when it is being used, the battery is needed to restart the engine. This could result in a stall at an intersection, and if drivers are not alert, may collide with a stalled vehicle.

While driving on interstate transmission would “lock up” momentarily creating drastic drop in speed and unable to shift gears and accelerate. “D” would start flashing in dash board. Dealership said this is unrelated to current recall about rear wheels locking up from valve body failure and instead this is an electrical issue. Dealership also stated this is the 2nd truck in a week they have had come in with this issue. Almost caused accident on interstate with my family and I as a result of sudden drop in speed and unable to accelerate with multiple cars behind us.

Driving down highway at 60 mph and truck shut off. had to try to get it over to the shoulder to off the travel lane. Dealer found wire harness chaffed at front left shock tower ECM bracket. Several wires damaged, repaired and cleared codes. This could have been much worse had I been in heavy traffic and needed to cross additional lanes of traffic to park in a safe area. I had no power steering and limited space to park the truck. I called to police to have a car dispatched to park behind me so the truck could be loaded on a tow vehicle to bring it to the dealer. This could have been worse had my wife been driving.

Tailgate releases on its own while parked, without the use of the switch. Tailgate released on its own with my trailer attached while parked on many occasions. The result of the Tailgate releasing caused damage to the upper section of the Tailgate, the "kicker speaker system" in the Tailgate and Tailgate switch located on the upper section of the Tailgate. There also have been multiple times when attaching the trailer that the Tailgate has released and struck me in the head. The Tailgate also fills with water during rain, and carwashes. The damage caused by the Tailgate releasing is a dent on the upper section of the multi-pro Tailgate and rust and malfunction of the " kicker speaker system " as well as the occasional hickey and headache on my head. The Tailgate has filled up with water since I purchased it new in December of 2020 which I believe has been electricly shorting the Tailgate switch/button releasing the Tailgate randomly. Due to my particular 2020 GMC Sierra 1500 AT4 CarbonPro having the " kicker speaker system " in my opinion makes the Tailgate so much heavier than one without it that it made the damages such as the dent in the face above the Tailgate switch much worse than trucks without it also causing more water to enter the Tailgate causing more damage to the switch and components of the " kicker speaker system ", such as the amp and buttons for it not to mention my head on several occasions.

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.

My brakes failed 2 times. One time I almost got into a horrible wreck with my daughter in the truck. "Brake system failure" " max speed 43mph" I have not had any brake work or anything done. The dealer is trying to charge me to replace the whole brake system when [XXX] this says to reprogram. Still waiting on gmc to tell me if it's covered under warranty. From my own research this has been a major problem for hundreds of people if not more. I could have died because of a faulty brake system or a bad software update. I need help with this and so do the countless other 2020 gm owners. There is a recall on the 2019 for the exact problem but not the 2020s. GM safety recall N192268090 please advise INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

My wiring harness which affects all systems. I was on the Interstate when out of nowhere any and all warning lights came on. The power was cut and rapidly slowed down. I also pulled into traffic and the truck just lost power. The problem was confirmed by dealership. The vehicle was inspected by dealership and wiring harness was the issue. The issues appeared out of nowhere. All the warnings lights came on at once. There has been numerous issues with this part and it’s even recognized by just.

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.

Back window frame crack led to water intrusion which flooded electric module controlling speedometer and adaptive settings. Extremely unsafe driving with faulty electrical components unknown to me. Insurance and Dealership told me this is a common GMC occurrence. Cost is near $10,000 to make truck drivable.

We are unsure what happened that caused the issue. One day the dashboard just started giving us error messages, 3 of them to be specific. One says check turn signals, another says check trailer brake light and another something else about brakes or turn signals. (We have to dismiss them all before anything on the dash is viewable). This issue is causing the blinkers to blink fast as though the blinker lights need replaced and it happens when turning right or left. The alerts continue to give us error messages every few minutes, even after we have dismissed them all. We had the truck at a shop trying to figure out the issue and his guys spent hours and replaced things he thought were causing the issue but nothing fixed it. He referred us to take it to the dealership service shop for troubleshooting so we took it to the GMC dealer where we bought the truck. GMC has already spent hours, maybe 5-7 hours at $150 per hour, trying to figure out what's wrong and have been unable to find anything wrong. The truck is still at the GMC dealership shop but I can get pictures of the errors when we get it back.

Camera always stays on even when i am driving camera still on my dashboard

I have a lifters problem that the dealership takes more that three weeks to fixed without a loaner car, then i have electrical problems where the truck doesn't start at all without any warning and that's it's dangerous, never now where its going happen

Own a 2020 GMC Sierra AT4 with 13K miles and I owned the truck for 1 year. All of a sudden my vehicle started receiving multiple warning messages. Electronic Stability Control, Antilock Braking System, ECM, reduced Engine Power, etc. I see there was a recall for 2019 GMC Sierra's for the same issues. Why isn't 2020 GMC Sierra's not also part of that recall ? It is ridiculous that a brand new truck has these types of serious issues affecting so many vehicles. Why is GMC allowed to continue to sell later model trucks after the 2019 recall with the exact same ESC and Anti-lock Braking system problems ?

Two times while on the freeway the service parking brake and engine lights came on and starting braking. Could not drive over 20 mile an hour. Both times taking to dealer the lights where not on and they could not find anything wrong. I even have video of it happening.

Bought 9-4-2020. On 9-4-2021 went start vehicle and no electrical power, battery dead. Will not hold charge to start. Brand new purchased at Morgan GMC in Shreveport Louisiana

Issue 1: Front left sensor(s), after a rain, car wash and now after an oil change, continuously vibrates the drivers seat and the red light warning stays lite indicating that an obstacle is located near the left front of the truck. This has happened on several occasions and after a time both indicator stop. Issue 2: When traveling on a freeway, twice now, the cruise control suddenly disengaged or decreased mileage, as if it had detected a vehicle in front of us. There was no vehicle within a quarter mile of us front or back, nor any vehicles on the side. No debris in the road either. Usually when the adaptive cruise is set and detects something in front the icons on the dash turn orange and starts to flash. That didn't happen, rather the cruise icon changed to blue in color and the truck slowed. This I would consider a safety risk. Both instances (December 2020 and April 2021) have been reported to a dealership and noted in a file. When the customer care person attempted to get malfunction codes, nothing appeared to be wrong with the vehicle.

Service ESC, Service Power Steering, antilock brakes disabled all flashed on information center of vehicle. Service engine light, antilock brake light, ESC, low battery all illuminated. Vehicle would not start - try to start it would go through all issues on information center. This is the same ESC issue described for 2019 Silverado and GMC Sierras.

The display for the backup camera and infotainment system became blank. Other owners have the same complaint. This is a serious safety issue because I was backing up when it went blank.

TL* THE CONTACT OWNS A 2020 GMC SIERRA 1500. THE CONTACT STATED WHILE DRIVING, THE SIDE VIEW MIRROR'S BLIND SPOT ALERTS ON BOTH SIDES ENGAGED WITH NO VEHICLE NEARBY. THE VEHICLE WAS TAKEN TO TURNER BUICK GMC (612 E MAIN ST, NEW HOLLAND, PA 17557) WHERE THE CONTACT WAS INFORMED THAT THE SENSORS WERE DIRTY. THE CONTACT THEN WASHED THE VEHICLE HOWEVER, THE FAILURE RECURRED. THE VEHICLE WAS NOT REPAIRED. THE MANUFACTURER HAD NOT BEEN INFORMED OF THE FAILURE. THE FAILURE MILEAGE WAS APPROXIMATELY 400. THE VIN WAS NOT AVAILABLE. *BF

[XXX] INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6). *TR

ON TWO SEPARATE OCCASIONS, THE TRUCK HAS BEEN DEAD WHEN ATTEMPTING TO CRANK. THERE WERE NO LIGHTS OR DEVICES LEFT ON AFTER THE PREVIOUS TIME THE TRUCK HAD BEEN USED. SOMETHING IS DRAWING POWER FROM THE BATTERY CAUSING IT TO BE DEAD. AFTER RECHARGING THE BATTERY, THE CHECK ENGINE CODES READ THAT THERE IS A PROBLEM WITH 'BRAKE LIGHT ILLUMINATION.' HELP IN DETERMINING WHA T IS CAUSING THE BATTERY TO DIE ON SUCH A NEW VEHICLE WOULD GREATLY APPRECIATED! I'M UNCERTAIN AT THIS TIME AS TO WHETHER OR NOT THE BRAKE LIGHT ILLUMINATION IS CAUSING A SAFETY HAZARD.

AFTER HAVING ALL SORTS OF WARNINGS OVER TIME LIKE "SERVICE ESC," "SERVICE PARKING BRAKE," AND MORE, I NOW SEE "BRAKE SYSTEM FAILURE: 62 MPH TOP SPEED" FLASH ACROSS MY DASH. I AM READING AND HEARING THAT THIS IS A VERY DANGEROUS PROBLEM. NEW TRUCK. BRAND NEW. HAD IT LESS THAN A YEAR. BRAKE MESSAGE ALWAYS ON START UP.

THERE IS NO WAY TO PERMANENTLY DISABLE THE AUTO START STOP ON THE VEHICLE. SEVERAL OTHERS HAVE COMPLAINED ABOUT THIS, NO RESPONSE FROM GM. THERE NEEDS TO BE A FIRMWARE UPGRADE TO THE ECM TO ALLOW THE OWNER MAKE THE DECISION ON IF THAT IS ENABLED OR DISABLED. ON MINE, I HAVE TO PUSH A BUTTON EACH TIME I START THE ENGINE TO DISABLE THAT. SOME GM VEHICLES DON'T HAVE THAT OPTION.

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.

DISPLAY IS DANGEROUSLY TOO BRIGHT WHEN BACKING UP CANNOT SEE TO BACK UP VEHICLE SAFELY

VEHICLE DOES NOT START AND FLASHING VARIOUS CODES SERVICE JUST ABOUT EVERYTHING ON THE VEHICLE

THE NIGHT TIME BACKUP CAMERA IS REALLY BRIGHT AND BLURRY AND IT MAKES IT HARD TO SEE WHEN BACKING AT NIGHT

ELECTRONIC ABS BRAKE FAILURE WITH 73 MILES ON ODOMETER WHILE STOPPED AT RED LIGHT ALARM CHIMES SOUNDED AND POWER BRAKES WERE LOST. WARNING LIGHTS ON DASH ABS BRAKE FAILURE MULTIPLE ENGINE WARNING LIGHTS CAME ON. DEALER SERVICE WAS PUZZLED NEEDED TO CONTACT GM TECHNICAL SUPPORT. FINAL OUTCOME THEY ARE REPLACING THE ELECTRONIC BRAKE MODULE.

BATTERY WAS DEAD IN THE GARAGE. CALLED ROAD SIDE ASSISTANCE WHO JUMP-STARTED CAR. CAR WOULD NOT GO INTO GEAR. WE ROLLED IT OUT INTO DRIVEWAY WHERE IT SAT FOR 24 HOURS. WHEN IT WAS LOADED FOR TRAVEL TO DEALERSHIP, IT CRANKED AND WAS DRIVEN UP ON WRECKER TRAILER LIKE IT HAD NO APPARENT PROBLEMS. WAS CARRIED TO DEALERSHIP WHERE THEY RECHARGED AND CHECKED THE BATTERY AND RESET 14 DIFFERENT CODES WHICH WERE LOST WITH THE LOW VOLTAGE.

BRAND NEW TRUCK PURCHASED IN MAY 2020. VEHICLE WOULD NOT START ON 7/2/2020 AND A NEW BATTERY WAS PLACED IN THE VEHICLE. THE TRUCK WOULD NOT START AGAIN ON 7/17/2020 UNKNOWN REASONS...

REVIEW CAMERA IS EXTREMELY BRIGHT WHEN BACKING. IT'S SO BRIGHT THAT A GLARE IS THROWN ONTO REAR WINDOW MAKING IT NEXT TO IMPOSSIBLE TO SEE OUT REAR WINDOW OR USE SIDE VIEW MIRRORS. I OFTEN REVERT TO TO OPEN DRIVERS DOOR AND LOOKING BACKWARDS THAT WAY. SOMEONE IS GOING TO GET RUN OVER AS YOU CANNOT SEE WHERE YOU ARE BACKING. VERY DANGEROUS!

SMELL OF SMOKE STRONG IN THE CAB AND OUTSIDE HOOD OF TRUCK. ALSO HAVE SEEN SMOKE COMING FROM HOOD OF TRUCK. SMELLS LIKE BURNING ELECTRICAL OR PLASTIC

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.