GMC 2006 Sierra - Manual (Page 251)

Setting Preset Stations
Up to 18 stations (six FM1, six FM2, and six AM) can
be programmed on the six numbered pushbuttons,
by performing the following steps:
1. Turn the radio on.
2. Press AM FM to select FM1, FM2, or AM.
3. Tune in the desired station.
4. Press and hold one of the six numbered pushbuttons
until you hear a beep. Whenever that numbered
pushbutton is pressed, the station that was set
will return.
5. Repeat the steps for each pushbutton.
Setting the Tone (Bass/Treble)
AUDIO: To adjust bass or treble, press and release
AUDIO until BAS or TRE appears on the display. Then
press and hold the up or the down arrow to increase
or to decrease. If a station is weak or noisy, decrease
the treble.
To adjust bass or treble to the middle position, select
BAS or TRE. Then press and hold AUDIO for more than
two seconds until you hear a beep. B and a zero or T and
a zero will appear on the display.
To adjust all tone and speaker controls to the middle
position, first end out of audio mode by pressing another
button, causing the radio to perform that function or
by waiting five seconds for the display to return to time
of day. Then press and hold AUDIO for more than
two seconds until you hear a beep. CEN will appear on
the display.
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