When the light comes on low tire press check each tire with tire press guage what ever tire has the lowest press add air, I carry one in all 3 of my cars works fine but is a pain in the rear
Once you hook up the guages and start feeding in the freon it will automaticlly trip the switch and bring on the compressor when you get enough freon in the system:)
I just replaced my dunlop runflats, what a terrible ride,the tires only had 18,000 miles on them.I replaced them with Falkens,so far so good, reasonable cost,much better ride. :)
I have a 06 gs300 purchased my chrome wheels from CA off of e-bay same exact wheels that came with the car,I did a chrome exchange,a lot less expensive very happy with the deal. :)