Ink has built up on the bottom plate inside the printer. You need to run a bottom plate cleaning cycle before duplex printing.
Here's how:
- On your computer, open the printer driver setup window and go to the Maintenance tab.
- Click Bottom Plate Cleaning. A dialog box will open with instructions.
- Prepare a single sheet of new A4 or Letter-sized plain paper. Fold it in half horizontally, then unfold it.
- Fold one side of the paper in half again, aligning the edge with the center crease, then unfold it.
- Load this single sheet into the front tray with the ridges of the creases facing up. The edge of the half with no crease should face away from you.
- Make sure the printer is on, then click Execute in the dialog box.
The printer will feed the specially folded paper through to clean the inside.
If that didn't work: After the page ejects, check the folded parts for ink smudges. If they are dirty, run the Bottom Plate Cleaning procedure again.