2008 GMC Sierra 1500 Pickup Owner's Manual - Page 226

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 Obutton 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 3-109 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 3-118 for more information. Playing an MP3 CD-R or CD-RW Disc Radios with a Six-Disc CD player have the capability of playing an MP3 CD-R or CD-RW disc. For more information on how to play an MP3 CD-R or CD-RW disc, see "Using an MP3" in the index. Playing an MP3/WMA CD-R or CD-RW Disc Radios with a CD and DVD player have the capability of playing an MP3/WMA CD-R or CD-RW disc. For more information on how to play an MP3/WMA CD-R or CD-RW disc, see "Using an MP3" in the index. CD Messages CHECK DISC: Radios with a Single CD player or radios with a Six-Disc player displays CHECK DISC and/or ejects the CD if an error occurs. Radios with a CD and DVD player may display other messages when an error occurs: Optical Error: The disc was inserted upside down. Disk Read Error: A disc was inserted with an invalid or unknown format. 3-90