A distinction is made between direct and indirect tire pressure monitoring systems.
Direct TPMS systems measure and record air pressure data with extreme precision using sensors that are built into the valves in the tires. The data is transmitted wirelessly to the vehicle’s on-board electronics system almost in real time and it also appears on the driver’s display.
Indirect TPMS systems use the so-called ABS system. This determines air pressure loss using the rolling circumference of the wheel. However, these ABS systems have very tight legal tolerances and, unlike direct systems, are not suitable for all vehicles.