2003 GMC Sonoma Owner's Manual - Page 179

Radio with Cassette and CD Set the volume at the desired level. Press this button to select LOW, MEDIUM or HIGH. AVOL will appear on the display. Each higher setting will allow for more volume compensation at faster vehicle speeds. Then as you drive, automatic volume increases the volume as necessary to overcome noise at any speed. The volume level should always sound the same to you as you drive. NONE will appear on the display if the radio cannot determine the vehicle speed. If you don't want to use automatic volume. select OFF. DlSP (Display): Press this button to switch the display between the radio station frequency and the time. Time display is available with the ignition turned off. Playing the Radio PWR (Power): Press this knob to turn the system on and off. VOL (Volume): Turn this knob to increase or to decrease volume. AUTO VOL (Automatic Volume): With automatic volume, your audio system adjusts automatically to make up for road and wind noise as you drive. To change the default on the display, push the knobuntil you see the display you want, then hold the knob for two seconds. The radio will produce one beep and selected display will now be the default. 3-52