An E3 error code in a Canon MP210 printer is frustrating. This code reflects a paper jam that is not always apparent immediately and can be indicative of other problems.
Remove the jammed paper by pulling it from the front or top of the printer. If it does not come out, restart the printer to eject the paper. If the paper fails to come out or rips, remove the cover and retry. Once you have removed all visible paper, check paper sensor paths for debris or damage, blowing it out as needed.
Reload and Test
Reload the paper as recommended and print a test page using the printer's software. If the error continues, the sensor that generates the error may be damaged. If so, bring your printer to an authorized service center.
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For prevention, verify your paper is the correct type and isn't folded or substandard. Clean feed rollers periodically with a swab, removing loose particles. Push the "Maintenance" button repeatedly until the "B" appears. Next push the "Black" or "Color" button to run standard paper through it. Once complete, run three sheets of A4 paper through it, setting paper thickness settings and arranging the papers vertically using the same steps.