Good after noon all. I was just reading the posts in this topic as My 2020 is having these issues as well. I had my 2020 Sierra towed in on Wednesday this week and called for an update on Friday. The dealership said they pulled codes for misfire on all cylinders but more on 3&8. My truck was flashing the check engine light (I think) a couple weeks ago and then on Wednesday it showed service parking brake and traction control as well as a flashing check engine light. Dealership has road tested twice now and can not duplicate. Both times I did not notice a change in operation which makes me think computer issues. Both times this happened shortly after starting the truck and claiming the same hill in the same spot. This is not a big hill by any means with a 3-4% incline. Also found that after a radio software update my radio will play both xm and Bluetooth at the same time which is odd the dealership brought in a specialist for that snag lol.
I will update when they resolve this for everyone to see
2020 SLT-T1 Sierra Elevation 5.3 with 15K KMs
