What gives? My '07 335I has started indicating that the TPMS is 'Inactive' Tire pressures are all ok. Resetting the system will turn the indicator off but it generally will come back on within 15 to 20 miles. Is this an electrical problem? The convenience system ( unlock, starting witout the key in the slot, ets has also stopped working. Are these related? OH, yes, I'm out of warranty.