The TPMS will trip when there is a pressure loss of 25% or more, this can be one tire or a combination of tires. The TPMS on my XLR shows exactly what the tire pressure is in each tire in the DIC (Driver Information Center). Temperature flucuations will trip the TPMS, fill your tires with nitrogen and this will end the TPMS light tripping in cold weather(unless you are actually losing tire pressure).