CEL Question
 

I have a 2019 SS with 23k miles.
Have had zero issues with this car until today.
Driving back from work I noticed the CEL was showing a steady light.
The car is driving perfect. The only thing I noticed is the AFM is not working,
Not that that is a problem, lol! But it’s not normal. I plan to take it down to have the codes read, but I was just curious sitting here tonight, if anyone had any insight into what this might be.
I got out of the car and went to the rear and listened to the engine idle. It sounds as smooth as it can be. I detected no misfiring. Obviously, our cars don’t have gas cap so I know that’s not the issue.
The only thing out of the normal around here is that it is unusually cold. The temperatures the last couple of days have been in the single digits. As it is in many areas in the country right now.
Any ideas?

Buy yourself an OBD-II reader on Amazon, you can get ones that hook to your phone for like $25, best investment ever, at least you'll go in armed with knowledge (you can Google any codes you find that will help you understand what caused the CEL)...

While we don't have a gas cap the door does still need to be closed all the way. Check that.

If you have OnStar just push the blue button. They can read the code(s) for you.

No, it doesn't. The fuel door has no sensors.

Can't support this approach enough. Once you have the reader, you put an app on your phone. Many of these, for the purposes of reading codes, are free - inCarDoc, Torque (Lite), and TrackAddict are ones that I use.

I have a FOSEAL reader that I've used on my previous truck with TrackAddict to diagnose a high pressure fuel pump that was starting to fail and then with my wife's Acura RDX to determine which oil pressure switch had failed putting her car into limp mode. I had to search the codes, look through forums, and learn more about the inner workings of the vehicles to diagnose the issues, but I learned a lot and saved hundreds of dollars (likely much more on the Acura) on each repair. I also used the setup on my new truck to provide details to GM about issues with codes right off the lot that ensured they did the correct repairs (on the second try because they ignored me at the dealership level on the first try).

There are several hundred reasons why you may get a light but notice no performance or operational issues. With a very wide variety of systems being monitored, it's impossible to narrow down likely causes from the description of your experience.

Any potential cause offered here without knowing the code is 100% pure speculation and has more potential to lead you down the wrong diagnosis path spending more time, money and aggravation.

As others have said, you need to read the code(s). OnStar will do it. I believe most chain Auto Parts stores will do it (for free), But as others suggested, for about 1/3 the price of a fill-up, you can buy a cheapo code reader for the future or a surprisingly powerful OBDII interface and phone app for some real-time information...

Maybe he meant the little flappers in the cap have to be closed so the evap system is sealed off. Not the actual fuel filler door.

Yeah, indeed that's possible, the rubber flappies do need to close all the way (but there is nothing for the driver to do about it).

So the code was P01F0. Coolant temp dropped below diagnostic levels.
Cleared the code…it’s gone
So the 1 degree temps caused the code.

It might be a good idea to check your coolant level to make sure the top tank is full and the bottom one is half full.

https://www.camaro6.com/forums/showthread.php?t=555908

It's been below zero here and no codes on my 2021. I doubt the cold temperature had anything to do with the code. Something else is probably going on.

I tend agree with Hack.
The more likely explanation is that the thermostat is not fully closing, and the car is taking longer to warm up, or never getting up to temp.
Is the car warming up normally and is the heater operating normally?

Heater and everything worked fine. Code never came back so hopefully it’s a done deal until it’s 0 degrees outside again.