Hello. I am an Oki Data helpdesk technician from Oki Data America's. Error 990 is a "Waste toner sensor detection error". This is a part of the black (K) toner. I recommend replacing the black toner which should resolve the issue. Make sure you purchase a genuine Oki Data replacement cartridge using part number 44469801 for the standard cap toner or part number 44469802 for the hi cap toner.If you need further assistance or have any questions, please contact our technical support number at 1-800-654-3282 available 24/7. You can also send email request's to our email support address at email@example.com.
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