Welcome to the Canon Forums and thank you for your inquiry!
So that the Community can help you better, we will need to know the Computer Operating System you're using (Windows XP/Vista/7/8 or Mac 10.x), as well as the way you connect to your device (USB or networked via WiFi or Ethernet).
Any other details you'd like to give will only help the Community better understand your issue!
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If the error remains after unplugging the printer for at least 10 minutes, it may require service. The best thing to do is to get in touch with our technical support team at http://bit.ly/Phone_Support so we can discuss your options.