Edmontonian here with a 2014 Limited. Air ride started giving all the usual issues in cold weather (down the bumps, wont adjust due to payload even when empty, etc) shortly after I bought it used. I performed all kinds of troubleshooting and determined that:
a) the system does not appear to leak (with a caveat that it does not appear to leak via piping/springs/compressor - more on that later)
b) the system is described as being a 'closed-loop', but it is most definitely not. If it loses (or thinks it loses) pressure, it will pull in air. When it gets (or thinks it gets) too much air, it will blow down.
c) the system continuously tries to level itself, even when off, but will stop if your battery voltage drops
d) the system sensors are extremely sensitive (the rear brackets are poorly supported and the slightest bend will throw off your leveling) DO NOT TOUCH/BEND/STRAIGHTEN them if you dont have problems.
e) most of the system- save the air tanks is rubber/plastic. The exception is the solenoid block valves (which controls where air pressure goes/leaves)
The slightest amount of moisture will freeze the solenoid block valves, leading to leakage, bleed down, etc. It will also prevent the system from properly filling springs and results in the system's belief that the spring pressure is full and therefore your payload is too high (despite the fact you're not carrying anything).
I found to fix this, as others have alluded to, is to put some air line antifreeze in. They sell gallon jugs at Canadian tire specifically for air systems (big rig trucks). Eventually the antifreeze wanes and you need to top it up again.
The trick is in how you do this. Once the system is bled down, it goes into limp mode and you need a special diagnostics tool to reset it (I bought a foxwell nt301 one from amazon). I bought an air conditioning recharge valve kit from Canadian tire (the truck's air system is recharged using the same quick connect system as R-134 a/c) and modified it so that i could connect my air compressor to it. To insert the antifreeze, I bleed the system down, connect my a/c valve kit, inject a cup or so of antifreeze using a syringe, and then pump the system back up to 120psi of air. Fixes everything for the majority of the winter.