The Brother machine has separate consumables the toner cartridge and the drum unit. Verify you replace only the drum unit and not the toner cartridge. If you want to know their difference, refer to "What is the difference between the toner cartridge and the drum unit?"

• 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:
  
  
  1. Open the front cover.
  2. Press the Clear/Back key.
  3. Press 1 to reset.
  4. Close the front cover, pressing firmly on each side until they click into place.