Here is a typical schematic diagram of the 2006 Volkswagen Touareg Tire Pressure Monitoring Circuit and Wiring System. The system consist of tire pressure monitoring control module, tire pressure sensor, computer data lines, power supply and fuse panel #8 (click image to enlarge).
The pressure sensors in the tires send data to a control unit which analyzes the data and sends results to a display. The control module identifies the signal from each wheel and tracks the tire pressure. Each wheel sensor has a unique identification code so the control module can recognize each sensor.