GMC 2009 Sierra 1500 Crew Cab Owner's Manual page 280

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.
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 3-138 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.
3-96
When a CD is inserted, the text label 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.
Care of CDs
If playing a CD-R, the sound quality can be reduced due
to CD-R or CD-RW quality, the method of recording, the
quality of the music that has been recorded, and the way
the CD-R or CD-RW has been handled. Handle them
carefully. Store CD-R(s) or CD-RW(s) in their original
cases or other protective cases and away from direct
sunlight and dust. The CD or DVD player scans the
bottom surface of the disc. If the surface of a CD is
damaged, such as cracked, broken, or scratched, the CD
does not play properly or not at all. Do not touch the
bottom side of a CD while handling it; this could damage
the surface. Pick up CDs by grasping the outer edges or
the edge of the hole and the outer edge.
If the surface of a CD is soiled, take a soft, lint free cloth
or dampen a clean, soft cloth in a mild, neutral detergent
solution mixed with water, and clean it. Make sure the
wiping process starts from the center to the edge.