Canon imagePROGRAF GP-4000 - Manual (Page 875)

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Cause
There may be a problem with the print head.
What to Do
Turn off the power, wait a moment, and then turn it back on.
If the error appears again, remove and reattach the print head.
Replacing the Print Head
If that does not get rid of the error, replace the print head with a new one.
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