I just purchased my first Lexus. It is a 2008 Lexus IS250 with 74,000 miles. After driver about 30 miles or so the tire pressure light comes on and will not go off. The first time this did it, I checked the pressure in the tires and it was high (the car had been sitting all night) at around 42 in each tire (the door says 35 for the fronts & 38 for the rears). I drove to the tire shop and they did not see anything wrong with the tires but we lowered the pressure to 38 in the fronts and 40 in the rears. Driving to and from the tire dealer, the light was off. Later that day though, while driving on the freeway, the light came back on. Later in the day I discovered that the pressure was back up to around 42 in each tire (this was just after driving for awhile). I lowered the tire pressure to 35 in the fronts and 38 in the rears but the light did not go off in my 8 mile drive home. Any help for this problem would be appreciated.