From the printer manual (platform independent):
Checking the print head nozzles:
-Make sure that the printer is turned off.
-Hold down the maintenance button (teardrop and paper icon) and press the power button to turn on the printer.
-Then release only the power button first.
-When the printer starts the nozzle check, release the maintenance button.
If the nozzle check page does not print satisfactorily (for example, if any segment of the printed lines is missing), then you should clean the print head as explained below. If the printout is satisfactory, you are ready to print your first page.
Clean print heads:
1. Make sure that the power light is on and that the error light is off.
2. Hold down the maintenance button for three seconds. The printer starts cleaning the print head and the power light begins flashing. Print head cleaning takes about thirty seconds to complete.
3. When the power light stops flashing, print a nozzle check pattern to confirm that the head is clean and to reset the cleaning cycle. If print quality hasn’t improved after repeating the nozzle checking and cleaning procedures four or five times, contact your dealer.
Caution: Never turn off the printer while the power light is flashing. Doing so may damage the printer.
Hope this helps.