Automatic Transmission Control Module problems of the 2019 GMC Sierra 1500

The contact owns a 2019 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the transmission unexpectedly hard downshifted. No warning lights were illuminated. The contact stated that the vehicle was hesitating while driving the rest of the drive. The vehicle was taken to the dealer; however, no cause for the failure was found. The dealer performed an 8-speed transmission fluid and filter replacement. The contact stated that the failure persisted. A month later, the contact stated that on a separate occasion, the transmission unexpectedly downshifted. No warning lights were illuminated. The vehicle was taken to the dealer; however, no cause for the failure was found. The contact stated that the failure persisted. The contact stated that a month later while her husband was driving on the freeway at an undisclosed speed, the engine seized and the rear-end locked and threw the driver into the steering wheel even though the seat belt was securely buckled. The contact stated that the transmission was stuck in drive(d), and the vehicle was unable to move forward. The driver shifted into reverse(r) and was able to pull off the freeway. The contact stated that the vehicle was then driven to an empty parking lot and left overnight. The vehicle was then picked up the following day and was driven to the dealer; however, no cause for the failure was found. The contact stated that the failure persisted. The manufacturer was notified of the failure. The contact hired a GMC engineer to inspect the vehicle and informed the engineer that the vehicle needed to be driven a minimum of three days and 300 miles before experiencing the failure. The contact stated that the engineer drove the vehicle for 100 miles. The contact stated that the GMC engineer and one of the employees at the dealer suggested replacing the pcm module because there was no fault code present during the failure. However, the contact was informed that there was no guarantee that replacing the pcm would fix the vehicle. The failure milea.

First feeling was, I was driving in a parking lot going maybe 5 miles an hour and I felt a vibration in the brake pedal. Pulled onto the main road and approached a stop light when the truck stopped a little hard as I was depressing the brake pedal. As I started pressing on the gas when the light turned green, I was traveling around 35 mph or so, when the truck came to a complete stop in which myself & passenger were slightly thrown forward due to the abrupt stop for no apparent reason. The vehicle in back of me nearly rear ended me due to the abrupt stop the truck did. I immediately contacted the dealer, in which after several days in the shop, the dealer told me that GMC knew about this particular issue but has not issued a recall. The dealer was instructed to replace the transmission control module, due to a malfunction in the tcm that apparently was trying to shut the truck down completely. Therefore causing the truck to stop abruptly with no warning.