2004 GMC Savana Van Owner's Manual - Page 167

To adjust both tone controls and both speaker controls to the middle position, first end out of audio mode by pressing another button, causing the radio to perform that function, or by waiting five seconds for the display to return to time of day. Then press and hold the AUDIO button for more than two seconds until you hear a beep. CEN will appear on the display. To adjust balance or fade to the middle position, select BAL or FAD. Then press and hold the AUDIO button for more than two seconds until you hear a beep. L and a zero or F and a zero will appear on the display. To adjust both tone controls and both speaker controls to the middle position, first end out of audio mode by pressing another button, causing the radio to perform that function, or by waiting five seconds for the display to return to time of day. Then press and hold the AUDIO button for more than two seconds until you hear a beep. CEN will appear on the display. Adjusting the Speakers (Balance/Fade) AUDIO: To adjust the balance between the right and the left speakers, press and release the AUDIO button until BAL appears on the display. Then press and hold the up or the down arrow to move the sound toward the right or the left speakers. To adjust the fade between the front and the rear speakers, press and release the AUDIO button until FAD appears on the display. Then press and hold the up or the down arrow to move the sound toward the front or the rear speakers. Radio Messages CAL (Calibration): Your audio system has been calibrated for your vehicle from the factory. If CAL appears on the display it means that your radio has not been configured properly for your vehicle and must be returned to the dealer for service. LOC (Locked): This message is displayed when the THEFTLOCK® system has locked up. You must return to the dealer for service. 3-45