ACDelco Professional Tire Pressure Monitoring Sensors (TPMS) are battery powered sensors, mounted on the inside of the wheel, and are a high quality replacement for many vehicles on the road today. This sensor monitors your vehicle's tire pressure and warns you when your tire pressure goes below 25% of the suggested pressure. The National Highway Traffic Safety Administration (NHTSA), a U.S. Federal Agency, requires that new cars and light trucks be equipped with TPMS for 2008 model year and newer vehicles. These premium aftermarket replacement components are manufactured to meet your expectations for fit, form, and function.