I’ve been driving my Yukon sparingly since the CEL came on and didn’t drive it at all yesterday. About an hour ago when I drove it I noticed that the light was gone. I have an appointment at the dealership on Friday but now there’s no light for them to check. Although I already told them what the code was. Is there anything in the computer that they can check or if I bring it in without the light on are they going to say there’s nothing they can do? It’s been running fine the last few times I’ve driven it so it really was a random misfire that caused the light to come on in the first place.
Another side note, after months of the speed limit sign on the HUD being blank when I drove it today the speed limit was displayed again. This vehicle does some random things
Software glitches are part of the "experience" at this point. There is so much software/hardware on these vehicles that as they fix issues in one place, new issues come up in other places. Also, with the amount of modules/features all booting up and communicating, there's bound to be a time or two where things don't boot up correctly. After about 10 months into owning my Yukon I had a drive cycle where the backup camera didn't work. Next time I started it, no issues and hasn't happened since.
As far as the CEL - all codes are stored in the system with an ID of which drive cycle it occurred. After ~40 drive cycles, the system will erase the code. When the dealership hooks up to it, they can see it in the list of stored DTCs. Active DTCs are also shown and if you have a check engine light on at that moment, they will be in that list.
Every dealership is different. Some will say "Its not an active code, check engine light is gone - come back when it is an issue." Also, from what you said about it now running fine, they will likely say you got a "bad tank of gas" or something along those lines. You can still keep your appointment, but don't be surprised if it ends up being a waste of time.