Had the TPMS alarm go off yesterday, checked the tyre and could not find any damage/nails etc and pumped back up, this morning got TPMS alarm again on same wheel, checked again and pumped up, have checked the pressure this evening and it has not dropped since 07:30 this morning and have done approx 300 miles too..   Maybe a sticking valve second time, but what caused the alarm in the first place.