i have a 2006 250 IS. i bought it in greenwich,ct. since i commute the car has about 20,000 miles on it. since jue of 2007 ive brought the car into the dealer five times because the tire pressure light goes on. does any one know if this a common problem and what can be done about it. all my repairs have been done at the lexus dealer in greenwich,ct. any comments or help would be appreciated. thanks.