Try the instructions on the HP Web Site Here
http://h10025.www1.hp.com/ewfrf/wc/document?docname=c01884620&tmp_task=solveCategory&lc=en&dlc=en&cc=au&site=null&lang=en&product=60096&key=null
But assuming that this has been working for some time and this has just started has anyone been playing with the printer? It sounds as if it's been locked in Diagnostic Mode particularly if there are no error lights appearing on the Control Panel. If that's the case you need to grab the Manual and read up on unlocking the unit. If you no longer have the manual or can not easily find it you can download one from here
http://h10025.www1.hp.com/ewfrf/wc/manualCategory?lc=en&dlc=en&cc=au&lang=en&product=60096&
Just as an afterthought have you made sure that you have canceled any Print Jobs in the Que? I went out to one job and all that was required was to remove all of the print jobs in the Que because the owner had attempted to print bigger than the supported pages. Once this didn't work they kept attempting to reprint and got no where.
Also if this is left plugged in all of the time try unplugging it for 30 seconds or so it's always possible that a Power Spike or some other junk on the Mains scrambled the printer. 
Col
Weird icons coming from printer
I've got some trouble with my printer: The only thing it prints is a couple of weird signs and icons. What does that mean? Can it be solved? My printer's an old HP Deskjet 930C.
Thanks in advance
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