Theory Of Operation
The Tire Pressure Monitoring (TPM) system, when all components are operating correctly, will automatically learn TPM Sensor IDs (new or existing) on every ignition/drive cycle, and locate the sensor to the correct position on the vehicle if the vehicle has been off (not driven) for 15 minutes prior to the drive.
At the start of the drive, the TPM system must first learn (both existing and new) sensors IDs prior to the automatic location process. Learning an existing TPM sensor occurs on the first Radio Frequency Hub (RF Hub) Module message reception from that sensor. Learning a new sensor ID requires multiple messages to be received from that sensor in approximately 2 minutes of cumulative driving at speeds above 15 mph. If new sensors must be learned and there are to many new Sensors IDs being received from different vehicles during the learning process, the learning period will be extended until the number of new sensor IDs are reduced to the same number of new sensors put on the vehicle. If this doesn't happen within 20 minutes of driving above 15 mph, then a "TPM Sensor -No Signal" DTC(s) occurs. When new sensors are used to replace existing sensors, the IDs from the new sensors should be written into the system first, before a TPM SENSOR VERIFICATION drive, to expedite the diagnostic procedure. If incorrect IDs are manually programmed into the RF Hub, the system will auto-learn the correct IDs so long as all sensors are functional. If a sensor is not functional and incorrect IDs are programmed into the RF Hub, pressure values on the TPMS display will not be updated for the miss-programmed IDs and malfunctioning sensor(s). After manually programming the TPM Sensor IDs, the ignition should be turned off before test driving.
Once the learning process has completed, the RF Hub starts the process for auto-location. The RF Hub compares the time of transmission by the TPM sensors to that of the wheel rotation positions determined from the ABS wheel pulse information. The RF Hub will use up to 36 TPM sensor transmissions verses wheel rotation position comparisons to determine the position of a sensor.
The RF Hub uses the ABS wheel pulse information to keep relative track of the rotation position of each wheel position. The TPM sensors will transmit relative to certain rotation positions. The TPM sensors will only enter this transmit with respect to a rotation position if they had been at rest for at least 15 minutes prior to being driving
When the RF Hub receives a TPM message during auto-location, it will record the rotation position of the four wheel positions (FL, FR, RR, and RL) for that Sensor transmission. During driving, all of the wheels do not rotate at the same rate (i.e. during turns). Over multiple TPM sensor message receptions from the same sensor, only one wheel position (FL, FR, RR, or RL) will have at a consistent rotation position for that particular sensor. The wheel position that has a consistent rotation position value over multiple TPM messages for that particular Sensor ID, is the position (FL, FR, RR, RL) for that particular Senor ID. Once auto-location is completed, it will update the pressure values on the display to the appropriate positions.
The use of the TPM-RKE tool is solely for the purposes of identifying the location of a sensor ID or non responsive sensor. It can't verify full functionality of the sensor. That is determined by the RF Hub DTCs during each drive cycle.
In addition to normal systems components diagnosed within this manual, non-FCC compliant components (added electronics) or aftermarket tires / wheels can also contribute to loss of signal. Off-road tires with alternate valve stem mounting from original equipment will affect TPM performance.