I got the following info directly from a Samsung tech rep for my SCX-4216F multi-function-printer, as the way to clear the lcd "Toner Empty" alert after replacing the cartridge. Quickly press Menu,#,1934. The lcd display will now display "tech" mode. Then press Menu, press the right arrow key until the display shows "New Cartridge". Press the * key labeled "Enter" two times. You should now see the red "Toner Empty" alert go off. To exit the "tech" mode... press Menu, #, 1934 like you did to enter "tech" mode at the start. Your display should now show "Ready"... and NO DISPLAY ALERT!
Hadley Cash, September 2009