I have juse done so and the black pattern on the printout hasn't come out at all. I tried cleaning the black nozzle but still the same. I changed the black ink a few days ago when documents weren't printing. Does this mean the black ink nozzle os clogged? How do I fix this?
Canon printheads are separate from the tanks and can usally be removed for cleaning.
Lift the top cover of the printer. Flip the inner cover down until it meets the paper output tray.
Lift up on each ink cartridge tank to remove them from the cartridge holder. Set the cartridges on one side so that the ink nozzles are not damaged.
Lift the lever beside the cartridge holder, which is the print head in this model. The print head will lift slightly when you raise the lever.
Pull the print head straight up out of the printer.
Rinse the print head thoroughly under warm running water from the tap taking are not to get water in the circuit board on the back of the print head. Run the water particularly into each hole where the print cartridges sit and underneath where the ink comes out. Do this until the water runs clear. Shake the print head vigourously to remove excess water and then place on a sheet of absorbent paper to dry. Reassemble, run a couple of cleaning cycles with the print cartridges reinstalled and try the print nozzle check again. I have done this with several Canon printer in the past and found it works.
Some people recommend standing the print head in warm water overnight, other have used isopropyl alcohol - personally using running warm water has always worked for me although it can take several goes.