Please check the following points:

• Make sure that a torn piece of paper is not inside the printer covering the scanner window.
  
  
• Wipe the scanner window with a soft cloth.
  To see how to clean the scanner window, click here.
  
  
• The toner cartridge may be damaged. Put in a new toner cartridge.
  To see how to replace the toner cartridge, click here.
  
  
• The drum unit may be damaged. Put in a new drum unit.
   To see how to replace the drum unit, click here.