Table 1 shows one common equipment related problems of the 2020 GMC Sierra 3500.
| Problem Category | Number of Problems |
|---|---|
| Equipment problems |
Diesel exhaust fluid tank heater malfunctioned and meted tank and connectors.
Engine started skipping, then service parking brake light came on, then service engine light came on and speed dropped to 44 mph.
The tailgate automatically opened while I was driving. I was sure the tailgate was shut and latched properly prior to the incident.
Driving approximately 50 mph when vehicle suddenly made loud bang and locked up rear brakes for 25' coming to a stop in road side ditch, numerous vehicles had to make evasive actions to avoid me and other vehicles. Flat spotted tire abut no visible physical damage. Sat on side of road for transmission temp to cool down then drove to shop without repeat. Called dealer was told the earliest appt was a month away. Have not been able to repeat incident so far. This has happened a few times and is becoming more frequent, mfg has TSB issued but indicates they cant assist because my warranty has expired so I will have to pay 225 per hour diagnostic fee. This is untenable and dangerous. This needs a recall and repair ASAP.
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.
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.
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.