GMC 2008 Yukon Denali Owner's Manual page 248

DVD/CD AUX (Auxiliary): Press to cycle through DVD,
CD, or Auxiliary when listening to the radio. The
DVD/CD text label and a message showing the track or
chapter number displays when a disc is in either slot.
Press again and the system automatically searches
for an auxiliary input device, such as a portable audio
player. If a portable audio player is not connected,
"No Aux Input Device" displays. If a disc is in both the
DVD slot and the CD slot the DVD/CD AUX button
cycles between the two sources and not indicate "No
Aux Input Device". If a front auxiliary device is
connected, the DVD/CD AUX button cycles through all
available options, such as: DVD slot, CD slot, Front
Auxiliary, and Rear Auxiliary (if available). See "Using
the Auxiliary Input Jack(s)" later in this section, or
"Audio/Video (A/V) Jacks" under, Rear Seat
Entertainment (RSE) System on page 3-105 for more
information.
If a disc is inserted into top DVD slot, the rear seat
operator can turn on the video screen and use
the remote control to navigate the CD (tracks only)
through the remote control.
3-86
Radios with CD and DVD Audio Output
Only one audio source can be heard through the
speakers at one time. An audio source is defined as
DVD slot, CD slot, XM™, FM/AM, Front Auxiliary Jack,
or Rear Auxiliary Jack.
Press the O button to turn the radio on. The radio can
be heard through all of the vehicle speakers.
Front seat passengers can listen to the radio (AM, FM,
or XM) by pressing the BAND button or the
DVD/CD AUX button to select CD slot, DVD slot, front
or rear auxiliary input (if available).
If a playback device is plugged into the radio's front
auxiliary input jack or the rear auxiliary jack, the
front seat passengers are able to listen to playback from
this source through the vehicle speakers. See "Using
the Auxiliary Input Jack(s)" later in this section, or
"Audio/Video (A/V) Jacks" under Rear Seat
Entertainment (RSE) System on page 3-105 for more
information.
In some vehicles, depending on audio options, the rear
speakers can be muted when the RSA power is
turned on. See Rear Seat Audio (RSA) on page 3-115
for more information.