Tire pressure should always be checked cold. The manufacturer take the heat build up into account when they set cold pressure. Dunlop says to let a warm tire set for a minimum 2 hrs before checking tire pressure. Theres always nitrogen.
Yes, I understand this, but, living in the desert southwest, our nights get cold but, day time temps still rise pretty high, so, I wake in the morning the light is on (tire cold) by the time I go to work and the vehical sets 10 hours, (tire cold again) the light is off, just the normal air temps cause a variation in the sensior. I find myself constly checking for a low tire becouse of the stupid light

I have yet to have a low tire, a slow leak, or a flat on this truck,(knock on wood)

and the light has been on lots of times!!!! at first I would add a little air in the mornings, just to be safe check the pressure at the end of the day ,before leaving work and find there was to much air in the tire. I beleive this is becouse the sensor activates the light, even with a 2 lb drop in pressure, really in my opinion it is just a pain in the a$$, maybe it would be better if I lived where the air temps were not so radical.but if this happens on a truck...... just think of one on the bike!!

I will wait for them to improve!!!