For chxf - The US version of the Ltd and the SRT have a sensor on each wheel that transmits a signal to a light on the dash when the tire pressure in a particular tire drops a certain amount.
The sensor is a part of the valve stem assembly. The problem I have is figuring out just which tire or was it all the tires that need air. I guess I check all of mine any way but the light on the dash is not tire specific, in other words it doesn't tell you right front is low just that one of the four is low.

Pat