Please check the following points to solve the problem:

• The toner cartridge may be damaged. Put in a new toner cartridge.
  Please refer to the instructions, "REPLACE TONER".
  
  
• The drum unit may be damaged. Put in a new drum unit.
  Please refer to the instructions, "REPLACE DRUM".
  
  
• Check if the Toner Settings of Replace Toner is Continue(Continue mode). To check the setting, press Menu, and choose General Setup => Replace Toner.
  
  
• Make sure that a torn piece of paper is not stuck inside the machine blocking the scanner.