to supplement the info from ReblFord...
The procedure below works on my ST, though you should be able to verify online the correct procedure for your application. The position you place and press the calibration tool depends on the location of the tire sensor. The process should only take a couple of minutes if all goes well.
If you have band sensors (like I do), the tire sensor should be 180 degrees to the opposite side of the valve stem and so depressing the button on the calibration tool is done at the outside edge of the rim at that sensor location.
Note: They recommend that the tire pressure sensor training procedure be done in an area without radio frequency (RF) noise, typically generated by electrical motor and appliance operation, cellular telephones and remote transmitters, power inverters and portable entertainment equipment.
Sensor Training (Reset Procedure)
1.Turn the ignition switch to the OFF position.
2.Turn the ignition switch from the OFF position to the RUN position three times, ending in the RUN position. Do not wait more than one minute between each key cycle.
3.Press and release the brake pedal.
4.Turn the ignition switch to the OFF position.
5.Turn the ignition switch from the OFF position to the RUN position three times, ending in the RUN position. Do not wait more than one minute between each key cycle.
6.The horn will sound once and the TPMS indicator will flash if train mode has been entered successfully. If equipped, the message center displays "TRAIN LF TIRE", place the calibration tool on the outside of the rim opposite the LF tire valve stem and press and hold the button. The horn will sound briefly to indicate that the tire pressure sensor has been recognized by the TPMS module.
7.Within two minutes after the horn sounds, place the calibration tool on the outside of the rim on the opposite side of the RF valve stem and press the calibration tool button. The horn will sound briefly to indicate that the tire pressure sensor has been recognized by the TPMS module.
NOTE: If the VSM (TPMS module integral to VSM) does not recognize any one of the four tire pressure sensors during the tire training procedure, the horn will sound twice and the message center (if equipped) will display "TIRE NOT TRAINED REPEAT" and the procedure must be repeated.
8.Repeat Step 7 for the RR and LR tires.
When the tire training procedure is complete, the horn will sound once and the message center (if equipped) will display "TIRE TRAINING MODE COMPLETE".