Please check the following points to solve the problem:

1. The drum unit or toner cartridges may not be installed correctly. Re-install the drum unit and toner cartridges.
   
   
   • Click here to see the details of how to install the drum unit.
   • Click here to see the details of how to install the toner cartridges.
   
   
2. Make sure toner save mode is off in the control panel or the printer driver. Click here to see the details of how to change the toner save mode setting.
   
   
3. Make sure that the media type setting in the printer driver matches the type of paper you are using.
   
   
4. The toner may be solidified inside the toner cartridge. Take out all the drum unit and toner cartridge assemblies and then shake all four toner cartridges gently.
   
   
5. Wipe the windows of all four LED heads with a dry lint free soft cloth. Click here to see the details of how to clean the LED head.
   
   
6. Perform the calibration. Click here to see the details of how to carry out calibration.