This message would appear if the drum unit is near the end of its life. Use the drum unit until you have a print quality problem, then replace the drum unit with a new one.
This message would continue to appear if the drum counter was not reset when you replaced the drum. To reset the drum follow the instructions below:
Open the top cover.
Hold down the Go button for more than 4 seconds to reset the drum counter.
Close the top cover.
Reset the drum counter only when you replaced the drum unit with a new one.
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