I agree with the other. Leaky bead.
I did have a tire while I was at school that the valve failed. I think water got in, and froze and let all the air out.
Just get them remounted basically
As far as TPMS goes there are usually 2 different kinds. One that goes off of wheel rotation. As a tire gets low it rotates at a different speed. The other kind is like a transmitter that measures the pressure and sends it to the computer.
My car has the latter, and with that system you can basically make a PVC 'bomb' with a schrader valve in it that you can put all the sensors in, pressurize, and place in the trunk.... no more light.
I just run my winter setup with the dash light on... I get used to it.
heres the best DIY ive found
http://www.toyotanation.com/forum/showpost.php?p=1714077&postcount=20