Originally Posted by Matrixolution
it's actually the FTM that is feeding the system the alert..
TPMS reports the actual tire pressure (an actual device inside the wheel).
FTM monitors the tire rotational speed against the other 3 in order to determine if you have flat tires or not.
One way to know for sure if you have TPMS is that if you have metal stems, you have TPMS, if you have rubber stems, you have FTM.
Not entirely sure about the metal vs. rubber stems. My stock tires had metal stems but no TPMS sensor. Just put on a set of winter tires on steel rims and had no light come up. But then again, mine is an 09 128i...