If ink is low, the 
ink light flashes. You can continue printing until the cartridge needs replacement.
ink light flashes. You can continue printing until the cartridge needs replacement.If a cartridge is expended, the 
ink light stays on. You must replace the cartridge to be able to print.
ink light stays on. You must replace the cartridge to be able to print.
Note:
Both black ink cartridges are required for printing. You cannot print when any ink cartridge is expended even if the other cartridges are not expended. Replace any expended cartridges before printing or copying.
For best printing results, use up a cartridge within six months of opening the package. When an installed ink cartridge is more than six months old, you may need to replace it if your printouts do not look their best, even after cleaning and aligning the print head.
Both black ink cartridges are required for printing. You cannot print when any ink cartridge is expended even if the other cartridges are not expended. Replace any expended cartridges before printing or copying.
For best printing results, use up a cartridge within six months of opening the package. When an installed ink cartridge is more than six months old, you may need to replace it if your printouts do not look their best, even after cleaning and aligning the print head.