Re: TPMS Sensor Issue?
By any chance did the tire pressure drop below the warning trip point due to cold weather (I think 31)?
The warning is set by the computer, based on the psi readings of the sensor. The sensor does not trip the warning, the computer decides to set or reset the warning. If your EVIC is showing an OK psi reading, there is nothing wrong with the TPMS sensor itself. The computer has some hysteresis programmed in, so the warning won't reset when the pressure increases to the trip point (31 psi), needs a couple psi more (34 psi I think) and perhaps 20-30 minutes on the road.
If you normally run on the low side of the recommended pressure, the warning behaves as you've seen. Before taking it back to the dealer, you may try just putting a few more psi in that tire until the indication resets. Once it resets you can lower the psi to any point above the trip point as you like.
BTW, All my TPMS seem to indicate low by 2 psi compared to a tire gauge.