ACDelco GM Original Equipment 13598772 Tire Pressure Monitoring System (TPMS) Sensor Kit with Sensor, Stem, Bolt, and CapACDelco GM Original Equipment Tire Pressure Monitoring Sensors (TPMS) are battery powered sensors located in the tire that monitor the vehicles tire pressure and warn the driver when pressure falls more than 25% below the manufacturers recommendations (normally through a slow pressure loss), and are GM recommended replacements for your vehicles original components. The sensor is connected with the valve stem and, by way of Radio Frequency (RF)