Explination point(?) warning light...

[dodgerblu88]

I have a 2008 Yaris, and was told the warning light that looks like an explination point was to let me know that one of the tires have low air pressure. It went out once I filled that tire with air, but has recently come back on. All the tires have the correct air pressure. Does anyone know what causes this light to come on, and what can be done to correct the problem?
Thanks

[CTScott]

There are a few other reasons why the light can come on, including having a bad sensor. This thread explains how to find out what the error code is by connecting two pins on the OBD connector, which will make the TPWS ECU flash the light in a pattern to indicate the error code:

http://www.yarisworld.com/forums/showpost.php?p=197208&postcount=11