GMC 2006 Sierra - Manual (Page 284)

RDS Messages
INFO (Information): If the current station has a
message, INFO will appear on the display. Press this
button to see the message. The message may display
the artist, song title, call in phone numbers, etc.
If the entire message is not displayed, parts of the
message will appear every three seconds. To scroll
through the message, press and release the INFO button.
A new group of words will appear on the display after
every press of this button. Once the complete message
has been displayed, INFO will disappear from the display
until another new message is received. The last message
can be displayed by pressing the INFO button. You can
view the last message until a new message is received or
a different station is tuned to.
Radio Messages
CAL ERR (Calibration Error): The audio system has
been calibrated for your vehicle from the factory. If CAL
ERR appears on the display, it means that the radio has
not been configured properly for the vehicle and must be
returned to your GM dealer for service.
LOCKED: This message is displayed when the
THEFTLOCK
® system has locked up. Take the
vehicle to your GM dealer for service.
If any error occurs repeatedly, or if an error cannot be
corrected, contact your GM dealer.
3-106