DustoR

Same thing here. 2021 Sierra 1500 AT4 3.0 Duramax. Happened twice now with 4,500 miles on the vehicle. Cranks for 10 to 15 seconds and no start. Starts perfectly immediately after. Just waiting to see if a recall comes in because at this point it doesn't seem like anyone has a clue what's actually causing it. Both times I tried starting it cold and didn't give time for the accessory/battery mode to spool up. I think I might try letting the CPU spool up before cranking it over to see if that helps. I submitted a case with GMC through their customer chat feature. I urge you all to do the same so they can put some emphasis on this case.