Epson Stylus Pro 4000 Reference Manual page 272

11. After confirming that INSERT CLEANING CRTG is displayed on
the LCD, insert a cleaning cartridge into the slots on the right
ink compartment.
12. After confirming that LOWER THE RIGHT INK LEVER is
displayed on the LCD, lower the ink lever on the right.
13. The printer starts cleaning the ink tubes, and CLEANING XXX%
is displayed on the LCD. Wait until cleaning is complete.
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Maintenance and Transportation