GMC 2006 Sierra - Manual (Page 310)

After the player is cleaned, press and hold the eject
button for five seconds to reset the CLEAN indicator.
The radio will display --- or CLEANED to show the
indicator was reset.
Cassettes are subject to wear and the sound quality
may degrade over time. Always make sure the cassette
tape is in good condition before the tape player is
serviced.
Care of Your CDs and DVDs
Handle CDs carefully. Store them in their original cases
or other protective cases and away from direct sunlight
and dust. The CD player scans the bottom surface of the
disc. If the surface of a CD is damaged, such as cracked,
broken, or scratched, the CD will not play properly or not
at all. 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.
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.
Care of the CD and DVD Player
The use of CD lens cleaners for CDs is not advised,
due to the risk of contaminating the lens of the CD optics
with lubricants internal to the CD mechanism.
Fixed Mast Antenna
The fixed mast antenna can withstand most car washes
without being damaged. If the mast should ever become
slightly bent, straighten it out by hand. If the mast is badly
bent, replace it.
Check occasionally to make sure the mast is still
tightened to the cowl. If tightening is required, tighten
by hand, then with a wrench one quarter turn.
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