CHECK XXXX 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: These cartridges may cause a malfunction, so replacing these cartridges
                with new cartridges is recommended.
     "Replacing Toner Cartridges"