CO 2020 GMC AT4

Mine did the same thing multiple times, then I ran the update and no issue since...

Harley The dealer found a bulletin on this, said they updated the ECM and performed three other recalls at the time. I have not had this issue since. (If your dealer doesn't know what to do, they can call Fuoco in Grand Junction, CO. They should be able to help. For the last 6 months I have had a brake squalling issue, they replaced once under a recall/bulletin but put the same low friction pads on and less than 1000 miles its doing it again. They said just drive it, they don't have a fix, GM won't let them put in high friction pads....

I'm experiencing the same issue, especially when pulling a good load. Hauling hay in western CO, empty flatbed gooseneck weighing about 5k, then loaded with 14k of hay back up hill to the house. 7 trips, 882 miles, half without hay, burned over 5 gallons of DEF. Truck handled the load nicely, really like the 10 speed, topped out on a 1 mile 7'% grade at 48 MPH. GVW around 27k....Not bad starting at 45 to make the curve at the bottom....

The dealer reprogrammed the ECM and did 3 other recalls on the pickup. So far so good.

Newdude Thanks, Should have said this initially: 2020 GMC 2500 AT4, 6.6 Diesel, Crew Cab standard bed. No modifications except B&W Ball and a folding bed cover. Yes, I live in Western Colorado, so cold but the days it occurred have not been too bad. It is happening after I have been running the vehicle, then stop for fuel or to return phone calls, so short amount of time turned off. Have not been towing either time. Found the printout from last time, 6 pages of issues: Most seem related to the Engine Control Module - No Communication Serial Gateway Module, no communication, Power Steering Module, lost communication with Engine Control Module, repeats for Transmission, Transfer Case, Body control, Chassis Control, Electronic Brake Control, etc... DTC Display codes...U0100, U0422, DLC Pin 6, 14 or 12,13 , 1 or 3,11 Called the dealer first thing this morning, they were going to discuss but still no answer...Just started it up, like nothing ever happened, well except the check engine light...

Thanks for the feedback. I'll check the cables and try placing the FOB there if it happens again. I'm usually on the road when this happens and leave the other FOB at home. I'll swap them out and see if I have the same issue. Picked up the truck in October 19, around 6k miles. Other than this issue, I really like it...

Twice now I go to start my 2020 GMC AT4 Dsl after it running fine throughout the day and nothing but errors. I select the Start button and it acts like it is going to start as the dash lights up, then starts clicking and running through a bunch of error codes, from low fuel to other sensor issues. Runs through the errors then just clicks and shuts down. Then it trys again, showing the same errors. It happened first time in December. I tried for 30 minutes to get it to start without any luck, then walked away and from about 50 feet hit the remote start and it fired right up. I took it immediately to a dealer and they cleared the codes but could never duplicate it. Said the first relay it came to was throwing a code and blocked the rest from letting it start. Took it the next day to my local dealer and they couldn't do anything as the codes were cleared, but reviewed the printout from the dealer that cleared to codes and said they have never heard of the issue and was probably a fluke and would never happen again.... Their suggestion was to remove the battery terminals and touch them together, shorting out the system and resetting the computer....seems strange. Yesterday, it did the same thing. Tried for over thirty minutes, and even the remote start would not work. I didn't try to remove the terminals as it was freezing and 40MPH winds. I went back in to the gas station and gave it some time, came back out and hit the remote start and it finally started up. Anyone else having this issue? Any ideas on a resolution? Getting tired of GM at this point. My 17 and 18 had the lurching issue at altitudes from 5-6k feet, finally got a repurchase from GM on the 18..... Thanks for any advice Shane