Epson EPL-5900L Reference Manual page 110

10. Clear the toner counter.
For Windows
Turn on the printer, access the printer driver. Click the
Optional Settings tab, and click Printer Setting. Click Toner
Level Clear, and the toner clear dialog box appears.
For Macintosh
Turn on the printer, select Chooser in the Apple menu. Click
Setup, and click Printer Settings. Click Toner Level Clear,
and the Toner Clear dialog box appears.
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Replacing Consumable Products