2004 Cadillac Escalade EXT Tire monitor

Funny they should know how to do it. It's in your manual if you have one if not follow theses steps.
Turn ignition switch to ON position, with engine off. Apply parking brake.
NOTE:If learn mode cannot be enabled, TPM system is not enabled in PDM/RCDLR. See appropriate manufacturer service information.

Turn headlight switch from OFF to parking lamps 4 times within 4 seconds. A double horn chirp will sound and the low tire pressure indicator will begin to flash to indicate the learn mode has been enabled (the low tire pressure indicator should continue flashing throughout the matching procedure, and "SERVICE TIRE MONITOR" message will be displayed on the DIC).
WARNING:Overinflating tires may cause personal injury or damage to the tires and wheels. When increasing tire pressure, do not exceed the maximum inflation pressure as noted on the tire sidewall.

NOTE:If a horn chirp does not sound after 35 seconds for any of the 4 sensors, turn ignition switch to OFF position to exit the learn mode. Repeat procedure from step 1.

Starting with left front tire, increase or decrease the pressure for 8-10 seconds, or until a horn chirp sounds. Horn chirp may occur before the 8-10 second pressure increase/decrease time period has been reached, or up to 30 seconds after the 8-10 second pressure increase/decrease time period has been reached.
After horn chirp has sounded, proceed as in step 3 for the next 3 sensors in the following order: right front, right rear and left rear.
After left rear sensor has been learned, check to see if the low tire pressure indicator is still flashing. If it is, turn ignition switch to OFF position to exit relearn procedure. Adjust all tire pressures to specification. If the low tire pressure indicator is not flashing, repeat procedure from step 1.
The DIC may list all 4 of the tire pressures at 0 psi after tire pressure sensor relearn procedure has been performed (although PDM/RCDLR reads correct learn value of the tires). To complete the relearn procedure, drive the vehicle at highway speeds for 5 minutes.
If this doesnt' work you'll have to have a pro do it with a scan tool it doesn't have to be a dealer.