Could not find this message in the service manual (at least for 2004 model)
Maybe the next step from the manual will tell you more:
The following test can be used to verify two functions.time cycle (once a minute).
One, that the tire pressure sensors are transmitting
properly and two, the EVIC module is
receiving these transmissions accordingly.
(1) Retrain the tire sensors (Refer to 22 - TIRES/
WHEELS/TIRE PRESSURE MONITORING/SENSOR
- STANDARD PROCEDURE). The tire sensors
must be retrained in order to set the proper transmitting
time cycle (twice a minute), failure to retrain
the sensors will cause a much slower transmitting
Using the STEP button on the overhead console,
scroll to the blank display, then press the
RESET button for five seconds, a beep will sound
indicating the start of this test. The vehicle icon and
transmission counters will now be displayed, (same
display as individual tire pressure except counters
replace tire pressure values).
(3) Upon entering the test mode, the EVIC will
clear the sensor counter and each time a sensor signal
for a road tire is received, the EVIC will update
the counter value (vehicle must be driven at 25 mph
to transmit). The counter values should all read close
to the same value (± 5), except for the spare tire
counter. If any of the road tires display a difference
of more than five, this is a sign of a problem. Replace
the appropriate tire sensor and retest the system.
This test will continue until any of the overhead console
buttons are pressed or the ignition is turned off.
NOTE: Pressing the RESET button during the test
will sound a beep and reset all the counter values
back to zero.