Canon MF247dw User Manual page 537

When set to <On>
White patches may appear in images printed on paper other than lightweight paper.
Special Printing Mode J
If printing is uneven when printing fine lines or faint images, select <On>.
Off
On
<Menu>
When set to <On>.
The following may occur.
● Definition may be affected
● Toner appears in non-print areas when using a new toner cartridge
● Toner cartridge may be used up more quickly
Special Printing Mode K
If toner does not adhere adequately and printouts are faded, select <On>.
Off
On
<Menu>
<On>
When set to <On>
Print speed is slower.
Clean Fixing Assembly
Clean the fixing unit after a toner cartridge is replaced or if black streaks appear on printouts.
Assembly(P. 596)
Setting Menu List
<Adjustment/Maintenance>
<Adjustment/Maintenance>
<Special Processing>
<Special Processing>
529
<Special Printing Mode J>
<Special Printing Mode K>
Fixing
<On>