a lil more description
The Tire Pressure Monitoring (TPM) system monitors air pressure in the four road tires (excludes spare). Pressure in the spare tire is monitored incase of a matching spare with sensor. These sensor transmissions occur only every 13 hours or if there is a significant change in pressure. RFHM has to be awake when sensor transmits to monitor spare pressure.
The TPM system consists of tire pressure monitoring sensors attached to each road wheel through the valve stem mounting hole, an electronic display, and an indicator lamp. The system communicates through the RF Hub Module.
The receiver circuit for the TPM system is integrated into the RF Hub. The RF Hub decodes the RF signals transmitted by each of the vehicle's tire pressure sensors. The decoded information is used to determine if "warning" or "fault" conditions exist within the TPM system.
Upon detection of a warning or fault condition, the RF Hub will send a request to the module that controls the indicator lamp and the text display via the vehicle bus system to illuminate or flash the indicator lamp. Also, upon detection of a warning or fault condition, the electronic display will send a request to sound the "chime".
The RF Hub will store all warning and fault conditions, placard pressure values and low-pressure threshold values (lamp ON and OFF) in memory that can be accessed through diagnostic communication. If new sensors are introduced to the vehicle, the data stored for the sensor being replaced will be deleted.
The RF Hub will store all wheel sensor IDs and locations and faults in memory that can be accessed through diagnostic communication. All other data values transmitted from each active wheel sensor shall be stored in the RF Hub memory.
The RF Hub automatically learns and stores the sensor IDs while driving “within 10 minutes continuously above 15 mph (24 km/h)” after a sensor has been replaced. The learning sequence will initiate when the vehicle has been stopped for more than 20 minutes.