If your Canon PIXMA MP640 says the inner cover is open, first check what it is trying to do: for paper printing, close the inner cover fully and press RESUME/CANCEL or OK; for printable-disc printing, open the cover, correctly reseat the Disc Tray, and press the same button. The required cover position depends on the print mode.
Why the MP640 reports an inner-cover error
The MP640 uses an inner-cover sensor to detect whether the cover is open or closed. Canon’s MP640/MP648 service manual lists errors when the cover is open while it should be closed, or closed while it should be open. It associates these conditions with operator-call codes 1841, 1846, 1851, and 1856, and describes the corresponding corrective actions: close the cover for paper printing, or open it and place the CD-R tray for disc printing.
That means the message does not always indicate a broken cover. The printer may be waiting for the opposite cover position because the job is for a printable disc rather than ordinary paper.
Clear the error based on the print job
For paper printing
- Stop or cancel the active job if the printer is in the middle of an unexpected operation.
- Close the inner cover completely. Check that paper, a label, or debris is not blocking it from shutting.
- Press RESUME/CANCEL or OK on the printer. Canon’s paper-printing instruction is to close the inner cover and press RESUME/CANCEL.
For printable-disc printing
- Open the inner cover.
- Remove and correctly reseat the supplied Disc Tray (also called the CD-R tray), with the printable disc positioned as directed for the tray.
- Press RESUME/CANCEL or OK to dismiss the error. Canon’s instruction is to open the inner cover, properly place the Disc Tray again, and press RESUME/CANCEL.
Do not open or close the inner cover while printing is in progress. Canon warns that doing so may damage the printer.
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If the message returns even though the cover is positioned correctly
If the error appears again immediately after you correct the cover position and press the button, stop rather than repeatedly forcing the cover. A persistent incorrect reading is consistent with a problem in the cover-sensing mechanism, not necessarily with the tray itself.
- Make sure the inner cover can move freely and reaches its fully open or closed position without obstruction.
- For a disc job, reseat the tray once and verify that it is the correct tray and is properly positioned.
- If the printer continues to report the wrong cover state, have a qualified technician inspect the cover actuator, inner-cover sensor, and associated wiring. The service manual includes sensor-cable wiring information and describes removal of sensor-bearing assemblies; these are technician-level checks.
A replacement Canon MP640 CD/DVD tray may help if the existing tray is missing or damaged, but replacing a tray will not correct a defective sensor, actuator, or wiring connection. Current parts availability and repair options are not established by Canon’s cited instructions.
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What the error codes mean
The MP640/MP648 service manual (Canon Inc., revision 0, QY8-13CN-000, copyright 2009) groups inner-cover operator-call codes 1841, 1846, 1851, and 1856 with the two opposite cover-state conditions. The codes alone do not establish which component has failed; first match the cover position to the job type and follow the appropriate recovery step.
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