GMC 2010 Sierra Denali Owner's Manual page 260

If the ignition or radio is turned off with a CD in the
player it stays in the player. When the ignition or radio is
turned on, the CD starts to play where it stopped, if it
was the last selected audio source.
When the CD is inserted, the CD symbol displays. As
each new track starts to play, the track number displays.
The CD player can play the smaller 3 inch (8 cm) single
CDs with an adapter ring. Full-size CDs and the smaller
CDs are loaded in the same manner.
Ejecting a Disc
Z
EJECT or CD (Eject): Press and release to eject
the disc that is currently playing. A CD ejecting from a
radio with CD/MP3/DVD and USB, ejects from the
bottom slot. A beep sounds and Ejecting Disc displays.
Once the disc is ejected, Remove Disc displays. The
disc can be removed. If the disc is not removed, after
several seconds, the disc automatically pulls back into
the player.
Z
DVD (Eject): Press and release to eject the disc
that is currently playing in the top slot. A beep sounds
and Ejecting Disc displays.
If loading and reading of a disc cannot be completed,
such as unknown format, etc., and the disc fails to eject,
press and hold for more than five seconds to force the
disc to eject.
4-88
Playing a CD (In Either the DVD or
CD Slot)
Insert a CD partway into the slot, label side up. The
player pulls it in and the CD should begin playing
(loading a disc into the system, depending on media
type and format ranges from 5 to 20 seconds for a CD,
and up to 30 seconds for a DVD to begin playing).
If the ignition or radio is turned off, with a CD in the
player, it stays in the player. When the ignition or radio
is turned on, the CD starts playing where it stopped, if it
was the last selected audio source. The CD is
controlled by the buttons on the radio faceplate or by
the RSA unit. See Rear Seat Audio (RSA) on
page 4 135 for more information. The DVD/CD decks,
(upper slot is the DVD deck and the lower slot is the CD
deck) of the radio are compatible with most audio CDs,
CD-R, CD-RW, and MP3s.
When a CD is inserted, the text tab DVD or CD symbol
displays on the left side of the radio display. As each
new track starts to play, the track number displays.
The CD player can play the smaller 3 inch (8 cm) single
CDs with an adapter ring. Full-size CDs and the smaller
CDs are loaded in the same manner.