CHECK TONER CARTRIDGE

Cause: Toner cartridges with print quality that cannot be guaranteed due
       to their decreasing lifetime etc., or used toner cartridges that have
       reached their lifetime, may have been inserted.

 Action: Pressing [OK] can continue printing as is, but these cartridges may cause a malfunction
            so replacing these cartridges with new cartridges is recommended.
     "Replacing Toner Cartridges"