GMC 2004 Yokon Denali Owner's Manual page 240

Problem
No power.
Disc will not play.
The picture does not fill
the screen. There are
black borders on the top
and bottom or on both
sides or it looks stretched
out.
The disc was ejected, but
it was pulled back into
the DVD player.
3-90
Recommended Action
The ignition might not be
in on or accessory.
The parental control
button might have been
turned on. The power
indicator light will flash.
The system might be off.
The parental control
button might have been
turned on. The power
indicator light will flash.
The system might be in
auxiliary mode.
The disc is upside down
or is not compatible.
Check the display mode
settings in the display
menu.
The disc is being stored
in the DVD player. Press
the eject button again to
eject the disc.
Problem
In auxiliary mode, the
picture moves or scrolls.
The language in the
audio or on the screen is
wrong.
The remote control does
not work.
Recommended Action
Check the auxiliary input
connections at both
devices.
Change the Video
Format to PAL or NTSC.
See "Stereo RCA Jacks"
previously for how to
change the video format.
Check the audio or
language selection in the
main DVD menu.
Check to make sure
there is no obstruction
between the remote
control and the
transmitter window.
Check the batteries to
make sure they are not
dead or installed
incorrectly.
The parental control
button might have been
turned on. The power
indicator light will flash.