I have a Canon MX340 multifunction printer. Recently, it keeps saying "Document in ADF" when I turn on the printer. I've tried clearing this multiple times, but as soon as the feeder wheels stop turning, in an attempt to clear the document feeder, it just pops up the same error again. This is particularly annoying, as it blocks all functions on the device - I cannot print, even though printing has no interaction with the document feeder.

I've opened up the feeder device, as much as can be done with fingers alone. There just doesn't seem to be anything in there. I ran a sheet of paper through about six times, just to see if some dust might be getting in the way, and I've blown out the feeder with air. Still nothing.

At this point, I don't care too much about the ADF working, I just want to disable whatever sensor is tripping this error message. Any ideas?

I found this thread online, where a user has the same problem. But no resolution was reached there.