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"