Yeah, that $1,200 fix is not a fix at all. Look at the quote, they are going to replace your CAC, which unless it completely filled with condensation and then froze causing it to crack, is not damaged, and is fully functional. Replacing the CAC will not fix the problem, it will just cost you a ton of cash and then you can have the same problem with the new CAC.
I live in Western North Dakota where temps are typically below 0f to -20f from December to February, this has not been the case this year, and it did not get below 0f until Monday. I have 88K miles on my 2016 Malibu. Monday evening, while driving home from the office the temp dropped to -14f, it was snowing (moisture in the air), and I felt it. Check engine light came on and then my car was shifting to maintain 70mph. Tuesday morning when I started my car to let it warm up for 20 minutes before leaving for work, the temp on the infotainment screen said -23. The CAC was so plugged with what I assume was ice that I could not get over 60mph without RPM's in excess of 4,000. I assume it just could not get any air. So I set the cruise at 55 and it got me to work (I have a 50 mile commute which is why I drive this car). I think at 55 the tachometer was right around 3,000. Now I installed a piece of cardboard, which I painted black, a couple of months ago and that seems to have helped until started getting cold (-10 or colder). Mind you I have been letting it warm up for 15 to 20 minutes each morning before leaving for the office (set a 9-minute timer and hit the start button a second time) and then once I get to the office I shut it off and then remote start it so it will sit and idle for 10 minutes after I arrive. I figure this is the best time to clear the condensation as the condensation has not frozen yet.
So what I did to get my car to start working again, after arriving at the office yesterday, I did not shut it off. I just let it sit and idle. It apparently shuts itself off after idling for so long, which I assume is 30 or 45 minutes. Then before leaving the office (by this time it had warmed up to -4) I let it idle for about 25 minutes or so and on my way home it was better but still lugging up hills. My son had a thing at the high school (another 30 miles from home) so I picked up my two younger boys from home, and we went to town. Upon arrival at the school, I again did not shut it off, it timed out again. When I got back into the car to head home, it had cleared all the crap out, so it ran fine, but again the temp had dropped to -22 so again when I got home I did not shut it off. This morning I let it warm up for about 30 minutes and it was not as good as last night, but I could at least maintain 70mph without shifting too much. It is supposed to warm up for the next few days again so hopefully it will completely come out of it again before it gets cold again.
My business partner's son is a mechanical engineer so I am working with him to 3D print me a thing to attach to the grill so it does not look like I have a piece of black cardboard zip-tied to my grill.