I just had the tire pressure light on too. If you have a low tire and fix the problem, it should go out in about a mile or so. Mine did when I filled the low tire. BUT, it went on again and it turned out I have a hairline crack on the inside of my right rear rim
I took it to a wheel dealer and they said I must have run over a pot hole in the rain. Turns out the rim also got a bit out of round, but they said they could fix it all for $135.
I'm not sure how the tire pressure sensors work, but they gave me an ugly wheel and tire as a loner, and they said I should ignore the light as it did not have a sensor. With the loner wheel I do not get the light????
I get the wheel back mon or tue. hope there are no surprises!