For 1990-2009 cars

Vehicles with audio steering wheel controls could differ depending on the vehicle's options. Some audio controls can be adjusted at the steering wheel.

(Next): Press to go to the next radio station stored as a favorite, or the next track if a CD/DVD is playing.
(Previous/End): Press to go to the previous radio station stored as a favorite, the next track if a CD/DVD is playing, to reject an incoming call, or end a current call.
(Mute/Push to Talk): Press to silence the vehicle speakers only. Press again to turn the sound on. For vehicles with OnStar® or Bluetooth systems, press and hold for longer than two seconds to interact with those systems. See OnStar® System and Bluetooth®in this manual for more information.
SRCE (Source): Press to switch between the radio (AM, FM, XM), CD, and for vehicles with, DVD, front auxiliary, and rear auxiliary. For vehicles with the navigation system, press and hold this button for longer than one second to initiate voice recognition. See "Voice Recognition" in the Navigation System manual for more information.
+ - (Volume): Press to increase or to decrease the radio volume.
(Seek): Press to go to the next radio station while in AM, FM, or XM™. Press to go to the next track or chapter while sourced to the CD or DVD slot. Press the if multiple discs are loaded to go to the next disc while sourced to a CD player.