2004 Chevrolet Colorado Owner's Manual - Page 186

Radio with Six-Disc CD AUTO VOL (Automatic Volume): With automatic volume, your audio system will adjust automatically to make up for road and wind noise as you drive. Set the volume at the desired level. Press this button to select MIN, MED, or MAX. 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. If you do not want to use automatic volume, select OFF. RCL (Recall): Press this knob to switch the display between the radio station frequency and the time. Press this knob with the ignition off to display the time. To change the default on the display, press the RCL knob until you see the display you want, then hold the knob until the display flashes. The selected display will now be the default. Playing the Radio PWR (Power): Push this knob to turn the system on and off. VOLUME: Turn this knob to increase or to decrease volume. 3-58