2020 GMC Sierra 3500 problems

“The contact owns a 2020 GMC Sierra 3500. The contact stated that while driving at an undisclosed speed, the vehicle inadvertently went into LIMP Mode. There was no warning light illuminated. The vehicle was taken to the dealer, where it was diagnosed that the transmission valve body sensor had failed and needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure and referred the contact to the NHTSA Hotline for assistance. The approximate failure mileage was 130,000.”

“Vehicle will not start due to known GM issues. This failure left my family stranded in cold dark unsafe area once already. If we were in the flow of traffic or had to leave an area immediately we would have been unable too. Known GM issue, engine fault code P12A6 fault code. Bulletin: PIP5719A discusses this issue. I am being told by the dealer there is a newer bulletin which advises ECM update. GM dealer is stating ECM software upgrade is required to resolve at owners expense. Owner is responsible for diagnostic fee in addition to repair costs. If the issue is not resolved vehicle may continue to experience starting failure and or other electrical problems. The night the vehicle left us stranded instrumentation was erratic and not reading properly on the instrument cluster. Very unsafe and GM should reach out to customers to inform them a software update is needed and it should not be at the expense to the consumer if the consumer is out of the bumper to bumper warranty.”

“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.”

“Engine started skipping, then service parking brake light came on, then service engine light came on and speed dropped to 44 mph.”

“My IntelliBeam function stops working sometimes, I can still use the lights as normal but the IntelliBeam function stops every so often and starts working after about 2 to 10 mins. Lane departure warning stops every so often and will start working after 1 to 10 mins, I have noticed that when it stops working at night time then the IntelliBeam function stops working also. When I press the on/off button for lane departure then it will say that lane departure is unavailable right now. I have been getting a p20ee code showing something is wrong with SCR nox sensor 2. Scan tool reveals that the sensor works normal and then stops. Once I clear the code then it works good for a few days.”

“The contact owns a 2020 GMC Sierra 3500. The contact stated that while driving 45 MPH with passengers seated in the rear seats, the passengers became aware that water was entering the vehicle between the window and frame. There were no warning lights illuminated. The vehicle was taken to the local dealer, who informed the contact of Technical Service Bulletin: 18-NA-383. The vehicle was not diagnosed or repaired. The manufacturer was contacted and confirmed that there was no special coverage or warranty coverage on the vehicle. The contact was referred to the NHTSA Hotline for assistance. The failure mileage was approximately 50,000.”