[Barbja]

How can you tell the difference between a TPMS warning that you get because your tire is low and one that you get because your tire is actually flat?

I've gotten a TPMS warning twice: front passenger side on my X5 about 6 months or so ago and rear driver side on my X6 this weekend. Both happened in my parent's driveway. They didn't appear 'flat', so I just topped 'em off and went on my way. No further problems.

I've never seen a RFT that's 'flat'; will I be able to tell that the tire in question is 'flat' and that more is required than just more air?