GMC 2003 C4C042 Owner's Manual page 179

Adjusting the Speakers (Balance/Fade)
AUDIO: To adjust the balance between the right and
the left speakers, press and release AUDIO until BAL
appears on the display. Then press and hold the up or
the down arrow to move the sound toward the right or
the left speakers.
To adjust the fade between the front and the rear
speakers, press and release AUDIO until FAD appears
on the display. Then press and hold the up or the
down arrow to move the sound toward the front or
the rear speakers.
To adjust balance or fade to the middle position, select
BAL or FAD. Then press and hold AUDIO for more
than two seconds until you hear a beep. L and a zero or
F and a zero will appear on the display.
3-10
To adjust both tone controls and both speaker controls to
the middle position, end out of audio by waiting for the
display to change to the time display. Then press and
hold AUDIO for more than two seconds until you hear a
beep. CEN will appear on the display.
Fade may not be available if you have a regular
cab model.
Radio Messages
CAL (Calibrated): Your audio system has been
calibrated for your vehicle from the factory. If CAL
appears on the display it means that your radio has not
been configured properly for your vehicle and must be
returned to the dealership for service.
LOC (Locked): This message is displayed when the
R
Theftlock system has locked up. Your vehicle must be
returned to the dealership for service.