The Brother MFC-490cw all in one printer is notorious for it’s ability to stop printing the color black, even when the cartridge is near full. This cleaning process will usually fix the problem.
First Try This: Press the Ink button -> Test Print -> then select Print Quality -> the Brother MFC-490cw will print a text pattern of small squares in each of the four colors in the shape of parallelograms. If you see any malformations in parallelograms then you will be asked asked to clean the cartridge. Please take the time to do so. -> Just keep repeating process until there are no gaps
The Next Step: Do an alignment check after the cleaning. It is almost the same steps: Press Ink button-> Test Print -> then select Alignment-> check to make sure the patterns match to the closest number.
This has always fixed my printer with it’s printing blank pages or color but no black.