2024 2500 gasser with 47,000 miles. Driving on interstate Friday when my truck shudders, downshifts, and I get the above message with check engine light. Transmission would not upshift. I had to drive home 2 hours at 65 mph at 3600 RPM with transmission temps 190-200 degrees.
Got it to the dealer Monday. They ran the code and said the #1 valve body was malfunctioning in the transmission. Miraculously, they had the part in stock and I had a new valve body installed that day with new transmission fluid/filter. Thankfully, all under warranty. Shout out to Everett Chevrolet in Hickory, NC.