TPMS sensors can leak, but I'd lean more towards a poorly-sealed bead or a tire that's contracted due to the cold weather and is leaking around the bead. GM wheels are notoriously bad for corrosion on the inside of the wheel, which can cause a poor seal and bead leaks.
The only way to really tell is to dunk the wheel(s) and look for a leak. Set up an appointment with us at NTB downtown sometime this week and we'll get you taken care of.