2020 GMC Sierra 3500 Problems and Top Complaints – Is Your Car A Lemon?

Electrical system, steering and structure issues among the top complaints received by the NHTSA from vehicle owners

Updated on Author: Brian Jones

Updated on Author: Brian Jones

Heavy-duty trucks have a massive job to accomplish. That’s why owners opt for the capable 2020 GMC Sierra 3500. After all, the automaker labels it as “best-in-class” in many areas, so it should provide everything a consumer needs. But, it doesn’t. This HD pickup suffers from a faulty electrical system, malfunctioning steering and a poorly-built structure.

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NHTSA Complaints for the 2020 GMC Sierra 3500

Complaint CategoryNumber of Complaints
Electrical System
Service Brakes
Power Train
Unknown Or Other
Forward Collision Avoidance: Automatic Emergency Braking
Electrical System:12v/24v/48v Battery

lick on other model year to view more problems: 2018

Problems with the Electrical System

When a small malfunction happens with the electrical system, it isn’t often a big deal. After all, having an infotainment system that doesn’t play the right volume level or provides connectivity concerns is more of an annoyance. However, electrical systems can also be major, such as what’s found with the GMC Sierra 3500.

One NHTSA review states, “Progressive pause starts when starting vehicle. After a few weeks of pause starting vehicle had no power at all. Towed it to dealer they replaced a bad battery. Pause start continued and after 4-5 weeks vehicle would not start. Couldn’t turn park brake off. There was power (lights in dash came one) but didn’t start. Vehicle parked and only after sitting unused this happened both times. (1st time no start, hadn’t driven for 3 days, end of summer weather)(2nd no start, sat overnight cool weather, but no freezing). Towed to dealer and they found nothing wrong.”

Electrical system problems continue to infiltrate the GMC Sierra truck. Just look at Service Bulletin #PIT5756. This states that electrical center bolts under the hood might be loose which leads to a no crank situation, trouble starting, grinding during starting, flickering headlights, flashing headlights and unregulated system voltage. Some issues can even be linked with unexpected powertrain movement, affecting acceleration and braking. What might seem like a small problem, just a loose bolt, turns into massive issues that can lead to an accident. In this case, GMC can only claim to be the best-in-class at failing.

Problems with the Steering

Steering the GMC Sierra 3500 is one of the most critical aspects, especially when towing or carrying cargo. Yet, this critical system is showing itself defective. 

Here is another NHTSA complaint. “Vehicle exhibits steering wheel shake/shimmy at speeds above 50 mph, sometimes severe. Repeated attempts at repair (currently 4 dealer visits), including application of Service Bulletin #19-NA-240 does not correct the problem. GM has now indicated this is a ‘normal’ condition and will not authorize further warranty reimbursable labor for correction to dealer. This steering condition affects safety as it occurs in varying severity and with no warning, especially during driving over rough pavement/bumps, and has nearly lead to a loss of control of the truck. This condition was present at delivery of truck at 221 miles. Truck current has 1688 miles.”

There’s nothing scarier than having steering issues while towing or hauling goods. If someone were to lose control of the Sierra 3500, there are further safety issues to be aware of. NHTSA Campaign Number 20V446000 is an air bag recall that states the Roof-Rail Air Bag (RRAB) inflator contains a diffuser component that wasn’t properly crimped, causing it to separate from the air bag. What owners are left with is an air bag that might not deploy as intended, especially if the truck rolls because of steering issues. Before driving this GMC truck, it might help to exercise arm muscles in order to put the effort forth it requires to keep the pickup on the road.

Problems with the Structure

The GMC 3500 costs far more than the standard truck lineup and it is designed for bigger jobs, so it should be made to handle the work, but it’s not.

Here is one more NHTSA complaint. “While towing a fifth wheel camper, the exhaust was so hot it melted the camper directly behind it. Was caught in side mirror before anything caught on fire.”

Showing how terrible this structure and design is, you can look at two more recalls. NHTSA Campaign Number 19V814000 states that over 500,000 vehicles have carpet floor covering that could catch on fire because of the hot gas venting through an opening in the pretensioner bracket. It’s just one more way that the GMC is attempting to start on fire. But that’s not all. NHTSA Campaign Number 20V324000 says the hood-latch striker wires might not have received the appropriate level of heat treatment. Because of this defect, the striker wires could fracture, causing the hood to open unexpectedly during a drive. Imagine towing a heavy trailer when the hood suddenly opens and blocks the view. This is the time when those air bags need to be working, but they aren’t either. It seems that this GMC truck is best-in-class, of having the most defects across multiple systems.

Your Lemon Law Legal Rights

Think you have a lemon? Sit back and let the experts work out your lemon case at no cost to you. The law makes GMC pay legal fees. You may be able to get your lemon out of your life. Every year, auto manufacturers buy back, replace or pay cash settlements to thousands of ‘lemon’ owners like you.

Complaint Data

CategoryForward Collision Avoidance: Automatic Emergency Braking, Power Train, Service Brakes
DateJan 16, 2023
Rear tires locking up out of no where almost made me jack knife.
DateDec 16, 2022
Rear window leaking on 2020 gmc truck due to faulty rear window seal and plastic slide. Known issue in 2020 models with a service bulletin already in place. Headliner saturated and black mold showing. Rear back liner has been saturated multiple times and gmc would not refund the cost of a whole new window to be put in and reimbursed. Gm bulletin # is 18-na-383
DateNov 29, 2022
Goodyear wrangler trailrunner at, lt275/65r20, factory installed on a 2020 gmc sierra denali 3500. While traveling 60 mph pulling a fifth wheel in south texas on a clear and dry day, the rear passenger tire unexpectedly lost its tread. As we slowed down, it completely lost tire pressure and we ran on the rim until coming to a complete stop. Immediately prior to the incident, the tpms and other safety systems in the truck read normal. There were no system warnings and no objects in the road. It put us in a dangerous situation as we were stopped on the shoulder of the highway right before a bridge and had our 3 children in the backseat. We called the police, but they never sent anyone to help with traffic. The rear fender and the wheel well of the truck were badly damaged. We have the faulty tire and it is available for inspection.
CategoryElectrical System, Engine, Structure:body
DateNov 14, 2022
Plugged in engine block heater and the car erupted in flames. Total loss.
CategoryPower Train
DateSep 20, 2022
The exhaust system is directed to the rear of the vehicle and when towing causes extreme heat to build on the item being towed, in my case a 5th wheel camper. The heat has melted the trim on my camper and is a potential fire hazard.
DateSep 04, 2022
These tires are good year wrangler trail runner at size lt275/65 r20. My total mileage on these tires was 42,751. These were the original tires that were installed when the truck was purchased new. My tires are rotated every 7,500 miles. Tire pressure is maintained at the exact pressure and in this case was just checked 4 days prior to the incident. I was driving on an interstate at 70 mph. A vibration started. I checked the tire pressure monitors and all showed normal pressures. About 4 minutes later the vibration increased and I decided to pull over. I had slowed to about 45 mph and had my turn signal on, as I was intending to pull on to the right shoulder. Suddenly the left rear tire exploded, and tread had separated. My truck was damaged . All the components in the wheel well are gone or damaged. The left rear 1/4 panel/fender is bent. No repair estimate yet. After the incident I saw zero pressure on that tire indicating on the tpms.
CategoryElectrical System:12v/24v/48v Battery
DateJun 28, 2022
The component that failed was the passenger side or main battery. Our safety was compromised when the design of the hvac system and the battery location allowed the hydrogen sulfide gas into the passenger compartment of the vehicle. The issue has not been confirmed by a deal or independent service center. The battery(s) and vehicle are available for inspection to confirm the issue. I have uploaded pictures of the battery and one can visually see the swollen battery with liquid leaking out of it. There were no warning messages or other symptoms prior to the failure. The rotten egg smell started shortly after the truck was started and my three young children were in the truck for about 10-15 minutes while I was loading items in the bed of the truck. When I entered the vehicle, the smell was extremely strong and my eyes started burning. I opened all the windows to air out the passenger compartment and thought it was possible off gassing from the nearby septic field. Once driving with the windows now closed, the smell came back instantly and very strong. My children started complaining of headache and nausea. For the next part of the trip, we drove with the windows down. When we arrived at our destination, I was able to determine the smell was coming out of the hvac system while in normal "auto" mode. Opening the hood, I went to smell around the engine compartment and when I got over the passenger side main battery, the rotten egg smell was so strong that my nose and eyes instantly started burning. We then drove the truck home with the windows closed and the hvac system in recirculate but the smell still entered the passenger compartment. All four of us had symptoms of hydrogen sulfide poisoning with my son being the worse with multiple vomiting episodes immediately upon exiting the vehicle. Poison control was notified and all four of us were evaluated in our local emergency department for inhalation toxin. The truck is all oem.
CategoryUnknown Or Other
DateMar 11, 2022
In short, the diesel exhaust fluid (def) reductant heater failed which requires the entire def tank assembly (part 85138746) to be replaced on my 2020 gmc sierra 3500. This cause the truck to go into "limp" mode where it will not travel above 65 mph, and after another period, the speed continues to be reduced down to 25 mph. Prior to the speed being reduced, there is a warning message that appears stating "service def system see owner's manual" and a warning light illuminates in the gauge cluster. Any severe reduction in speed that can cause the truck to go "limp" is a safety concern. In addition to being a safety concern, some quick internet research reveals that this has been a known problem with gm's def system since at least 2019. The electrical connections are too small for the current which supplied the def tank heater, causing the system to short and trigger the truck into limp mode which renders it useless. The replacement part is on national backorder, and it has been on backorder for years. My truck is completely useless until this part (or a better-engineered replacement) arrives at the dealer, and there are hundreds if not thousands of people waiting on this same, defective part to get their trucks back on the road. People are losing their livelihood and the means by which they support their families. Gm has known about this defective part for years and has done nothing- neither engineered a better part nor issued a recall with some kind of workaround. They haven't even been able to stock the defective part, and this is not just a supply chain issue as new trucks are still being built. This problem was not inspected by any police or insurance agency as it did not cause an accident or injury in this case.
CategoryElectrical System
DateNov 17, 2021
Infotainment system and center instrument cluster went completely black - six times over the course of one month. I took the truck to alan webb chevrolet in vancouver washington. Their service technician was aware of infotainment system “black screen of death - bsd” problems due to previous repair work on several different gm models. However, on the way to their service department to get this fixed, I rolled down the driver's side window about 6 inches to get some fresh air and rolled it back up. Out of nowhere the infotainment system and the center instrument cluster came back to life. No rhyme, no reason and both stayed on (illuminated). Their service technician could not recreate the bsd. They had my truck for more than one week and said they were working with gm engineers to resolve this issue. Gm case number sr 9-7065134382. I'm driving and towing my 5th wheel blind without a remedy for this electrical issue.
CategoryElectrical System, Power Train, Service Brakes
DateMay 26, 2021
The computer lite up the dash and reduced power, plus took the trailer brakes off line. This happened while loaded. To reset the system you have to pull over and turn the vehicle off. This happens 2-3 times per day. This was a problem at 600 miles. The transmission shifted from 10 gear to 5th gear while driving 75 miles per hour. The truck had 75,000 miles on it . Had to send another truck out to pick up the load in santa rosa new mexico. The dealer glenn polk in sanger has been working on for the last 4 months there is never a warning until the lights come on with a system failure.
CategoryElectrical System, Engine, Service Brakes
DateMay 26, 2021
The computer lights up the dash reducing power and turning off power to trailer brakes. This has almost caused an accident on several occasions . It happens a couple of times per trips. This vehicle has been in the shop a couple of times per month since it was put into service. Glenn polk chevrolet has worked on it each time and the problem is still there. This truck has also had several injector issues. There is an open case with this vehicle with general motors with no resolution. I have filled out forms on each of my 2020 gmc's 3500's.
CategoryElectrical System, Service Brakes
DateMay 26, 2021
The computer lights up dash reducing power and taking the trailer brakes away. This almost caused a wreck when the truck shut off and the brakes failed. This truck has been in the shop at least once per month trying to fix the issues, from computer and brake failure to injector failure. Glenn polk chevrolet in sanger has been working on this since the truck was new. Also we have case open with general motors without resolution. The dash lights up at the same time as the brakes fail.
CategoryElectrical System, Fuel/propulsion System, Service Brakes
DateMay 25, 2021
The computer malfunctions. It is available for inspection. The computer lights up and causes failure in the trailer brakes. Glenn polk the dealership in sanger texas has been working on a fix but has yet to come up with one. I have spoken with general motors representatives several time trying to resolve the problem without result. I also emailed the ceo last friday and have heard nothing. There were no warning lights until seconds before failure.
CategoryElectrical System
DateNov 22, 2020
Progressive pause starts when starting vehicle. After a few weeks of pause starting vehicle had no power at all. Towed it to dealer they replaced a bad battery. Pause start continued and after 4-5 weeks vehicle would not start. Couldn't turn park break off. There was power (lights in dash came one) but didn't start. Vehicle parked and only after sitting unused this happened both times. (1st time no start, hadn't driven for 3 days, end of summer weather) (2nd no start, sat overnight cool weather, but no freezing. Towed to dealer and they found nothing wrong.
CategoryUnknown Or Other
DateJul 23, 2020
While towing a fifth wheel camper, the exhaust was so hot it melted the camper directly behind it. Was caught in side mirror before anything caught on fire.
DateDec 12, 2019
Vehicle exhibits steering wheel shake / shimmy at speeds above 50mph, sometimes severe. Repeated attempts at repair (currently 4 dealer visits), including application of service bulletin 19-na-240 does not correct the problem. Gm has now indicated this is a "normal" condition, and will not authorize further warranty reimbursable labor for correction to dealer. This steering condition affects safety as it occurs in varying severity and with no warning, especially during driving over rough pavement / bumps, and has nearly lead to a loss of control of the truck. This condition was present at delivery of truck at 221 miles. Truck currently has 1688 miles.

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Brian Jones

About the Author:

Brian Jones spent more than 20 years working as an ASE Certified Master Tech and Parts Specialist at multiple dealerships. Brian has become an authority in the industry, traveling across the country to consult for car dealerships and contributing his expertise as a writer for several major automotive publications. In his spare time, Brian enjoys working on pickup trucks, muscle cars, Jeeps and anything related to motorsports.

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  • Maurice P

    My 2020 3500 Sierra Denali check light came on with only 6200 miles on it I’m the only owner I received a text stating it was a emissions problem so when I took it back to the dealership I was told I wasn’t driving it hard enough in my mind I’m wondering what’s next

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