Tire Pressure Monitoring: Description
The Tire Pressure Monitoring (TPM) system monitors air pressure in the four road tires (excludes spare). Pressure in the spare tire is monitored in case of a matching spare with sensor. Sensor transmissions occur if there is significant change in pressure. The Radio Frequency Hub (RFH) has to be awake when sensor transmits to monitor spare pressure.
Vehicles over 10, 000 lbs GVWR will not have a warning lamp.
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 RFH.
The receiver circuit for the TPM is integrated into the RFH. The RFH decodes the Radio Frequency (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.
Upon detection of a warning or fault condition, the RFH 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 RFH 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 RFH 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 RFH memory.
The RFH automatically learns and stores the sensor IDs while driving "within 20 minutes continuously above 20 mph (32 km/h)" after a sensor has been replaced. The learning sequence will initiate when the vehicle has been stopped for more than 20 minutes.
A new sensor ID can also be programmed directly into the RFH by using a RKE-TPM Analyzer in conjunction with a Scan Tool. Once the new sensor ID has been programmed, the RKE-TPM Analyzer can be used to update the TPM by activating the sensor.