Method and apparatus for determining tire condition using ideal gas law

An apparatus is provided for determining a tire operating condition including a tire-based sensor for sensing tire pressure and temperature and transmitting a signal indicative thereof and a vehicle ignition system. A vehicle-based receiver/controller is provided for receiving the signal from the tire-based sensor and for detecting the state of the vehicle ignition system. The controller provides an error signal when the sensed tire pressure is less than a set threshold value P set and resets the error signal when the sensed tire pressure is greater than a reset threshold value P rst . The receiver/controller determines the set threshold value P set and the reset threshold value P rst as a function of a calculated warm tire pressure value P warm , determines a mole value N of the tire pressure, and adjusts the determined set threshold value P set and the reset threshold value P rst in response to the vehicle ignition state and a change in the determined mole value N. A display is provided for displaying the error signal from the vehicle-based receiver/controller.