I have a 02 mcs with the stock run flats on it and the other day I got a VERY small nail in a tire and when it got low the warning light came on and now I cant get it to go off even if the pressure is fine. Whats wrong?

 

You tried resetting the light? My guess: Switch might be faulty.... Been there.....Done that!!!!!

 

how do you reset the light?

 

you should read your manual...

but to save you a few minutes:
hold down the tire pressure reset button by the ebrake lever for 3 secs. the next time you start the car it should be reset.

 

while moving you can press and hold the tire reset under the front of the e brake until the light goes solid then release . it will go out shortly after that .