I have a brother MFC-490CW and replaced the black ink, and my color ink has run out. It will not let me print as it says ink is low, so it won't even let me use the black? How do I print with only using black?

Greyscale is color not black only.
You can print in black and it will look grayscale only darker, printers are a pain to work with after a year has gone by, I can expect almost a half hour to print something with my $400 epson because one of the colors is out even though I never printed in the last year a colored page. I take the color cartirges out and they are empty, but I only print a page 2-3 times a year. I use the scanner all the time. Brother and epson have their print heads in the printer not the cartridge so make sure your inks are always have something in it or it will be miricle for the printer to last more than a year. Check colors every other week. One Epson printer only lasted 3 months because I never used it(print head dried up). Never use the set up with tubes running outside printer to small tanks of ink if you only use it occationally.

maybe you run out of ink for black, try to use other ink, if its still the same then their a stockup ink on your head of the printer and better to replace it. I think once you purchase an ink cartridge of cannon their is also printer head included. Hope it helps thanks.

here's a solution i came across when dealing with the same problem. apparently the printer expects all of the cartridges to be full and has a sensor to make sure they are even when only printing black. hope this helps!

http://journal.drfaulken.com/trick-your-brother-inkjet-into-working-when-an-ink-cartridge-runs-dry/

Try to clean the print head 2-3 times,if not work you need to replace 100% the print head.If a have been usefut please give me a vote :)

Check out if you've installed it correctly. Also check out other ink cartridges, are they empty? If yes you won't be able to print anything. However, if all ink cartridges are OK then try to reset the printer or reinstall the drivers. You can find help in MFC 495cw users manual

please try other black ink cartridge and run self test print, if black printed will.

You should run a few cleanings. Push the ink button then down arrow for cleaning and push ok.

Try remove all cartridges then put back it one by one.Make sure the color cartridges are not empty too.The printer need all cartridges not empty to initialized and working.

There may be an air bubble in the black tubing, it will take several more cleaning cycles to clear. You can tell it to clean only the black and save the other inks.

Did you try onboard print test by pressing INK LEVEL button. I am having similar problem but color prints but black does not. The printer has built in diagnostics that walks you thru some troubleshooting steps. It has you repeat cleaning 5 times and then asks you to replace cartridges if test fails...than repeat tests and call customer support if that does not work. Which I may do soon.