If I rotate tires on my car, how does the TPMS know which wheel went where? For the OEM TPMS I don't guess it matters since it doesn't tell you a specific tire, but for an after-market one, it matters. Is there a relearn function on them?

Just curious because I've seen signs at tire stores offering to "Relearn you TPMS" for the low price of $20.00USD

Matt in Moore Tafetta White 2008 HCHII