So on Saturday as I am driving my car, the Low Tire Pressure light appears on my dash. I check the tire pressure, and it was at 26 PSI, so i inflated it back to the normal 37psi, plus a couple more pounds due to a warm tire. I assume all is good, since the Low Tire light went off.

Sunday, drove down to the beach to go fishing, no light, no problem (no fish either). Today, I check the tire just to see if i needed to bleed any air out since i knew i put more air in. I read the gauge and its at 30psi, cold tire. So i am assuming i have a slow leak somewhere.

The million dollar question is, why didnt my sensor go off again? Does it have to be below a certain PSI? I will check again tomorrow morning, and see. Post later

There is a difference between cold and hot tire pressure. If you inflated the tire after driving around, your cold tire pressure will be different. Usually 5-7 PSI difference. Add 1 psi cold pressure tire pressure to compensate for each 10° Fahrenheit temperature difference between the temperature in the garage and outside. The tire pressure sensors will go off when it is below a certain PSI.

Normal is 37?? I thought normal is 35psi for the fronts and 38 for the rear.....

Catch and release right? I would never, ever put a dead fish in my new IS

I think once calibrated, there is a tolerance limit of the pressure sensor. Not sure what the limit is but that may be why your light hadn;t come on yet. Normal pressures are 35 front and 38 rear in all IS versions.

One way to find out when the low pressure signal switches on, is to bleed the air out with a pressure gauge and have someone inside the car look at the low pressure alarm. I'm also curious on what the setting is.

i had this same problem, i went to a tire shop and found out my valve stem was leaking air. Got it fixed, never happened again.

FWIW, my TPMS warning kicked in recently when all four of my tires dropped to around 30 PSI. I inflated the fronts to 35 and rears to 38 and reset TPMS to those values.

Cheers,
Kermee

Your right, 38PSI is right.

My tire is at 29PSI right now, cold tire. No light yet either. Going to get it fixed tomorrow morning