Yesterday I topped of the air in my tires in prep for our Xmas trip to Cal. This morning the TPMS was beeping and flashing the red light, I can keep it in the house and monitor the tires from inside. The pressure in the left outside rear tire had dropped to about 60 lbs. I couldn't tell by looking at it and it drove OK but it sure was low. I took it in and they found the valve stem leaking at the rim. It was replaced with a metal one and extensions were added so I have access to all six tires from the front of the rim.
I would have surely thrown that tire somewhere in the AZ desert.
THANK YOU TST!!!