Bingo! Abosolutly right. Glass LOOKED clean but it wasn't. As I slowly passed my finger on the glass I could feel something. I took a credit card edge and removed what ever it was. Wiped with a clean soft cloth and problem solved. No more lines. To be clear, this was on the small strip of glass in front of the big glass bed. Thank you.
If the line that is being produced only occurs when using the Automatic Document feeder (ADF) and not when making a copy via the platen glass, the issue is commonly due to a small mark or debris on the scanning glass area that lines up underneath the white vertical ADF roller. A small smudge on the platen glass can cause a "line" to be produced as every inch of the paper fed via the ADF passes over the area and is picked up by the scanner. The ADF roller is located on the left and underside of your lid. The scanning light sits in this area when using the ADF.
You will want to carefully and fully clean the glass in the ADF scanning area. There can also be a strip of transparent plastic on which there can be a mark or smudge. Look for scratches, tiny spots and marks of any sort. You can use a soft lint free cloth either dry, with a little soap and water or water to clean the glass and may have to scrub until it squeaks to remove certain types of marks.
NOTE: Please do not spray the cleaning solution on the glass.
Another way to ensure the mark is removed is to use a credit card by placing in on a angle and sliding it across the glass in one direction. You can then lift the credit card when reaching the end of the glass and return to the other side to slide it across again.
After cleaning the platen glass, run four to five blank/clean pages through to test it. If the line still appears, please contact us for further steps and assistance.
We hope this helps!
I am pasting the reply from mr19th below, and here is your why explanation: depending on your model of printer, this may work for you. On my MX 922, in front of ( to the left of as you look at the printer) the big rectangular glass panel, there is a narrow glass panel. When you place a page on the big glass, it does not involve the little glass. When you use the feeder, the page passes over the little panel. The little panel may have specs of material on it, or on the black plastic guide in front of it, or on the inside cover, to the left, my model has some black and white plastic guides, these may have caught some pieces of whatever. Clean the glass and these plastic guides. It worked for me.
Here is mr19th's explanation:
"At the very front of the glass bed there should be a separate thin strip of glass that has a plastic strip over it for protection. That's the strip of glass that scans the paper fed into the scanner from the top. So what you need to do is lift the corner of the plastic, to get under it, and run a cloth or something under the plastic strip and over the glass. You can use almost anything under it to clear the glass/plastic strip. I used a moist cleaning wipe. Not a good idea because of the moisture. I could see the moisture from the wipe clinging to the plastic strip on the glass after I wiped it, so I had to go under it again with one of those computer screen cleaners and everything was dry.
I scanned a blank page and the page scanned blank. Perfect! I hope this helps."
See if this works for you. Good luck.
Having same problem with canon MF5770. Scanning (e.g. blank A4 page) from the ADF has grey lines while copying from the ADF prints a white page), meaning that it's not a cleaning problem (or scanning uses some other mechanism than when reading the page for printing which wouldn't be logical). Of course scanning from glass works too. Replacing drivers can't do since latest seem to be 2015 and are installed. How to fix this?
I have the exact sasme issue with my MX 922 scanner. I just spent 1 hour and 6 minutes on the phone with a very frinedly Cannon Support tech.
In my case it only happens when I scan on the big glass, not when I use the ADF. Each time I scan anything that is 8.5 inches wide (full size letter or anything else with the same width) it introduces that black vertical line on far the right side.
The line shows everytime in the scan preview as well as in the final saved scan, no matter what format I use to save, i.e. JPG or PDF.
It also happens when I use the MAC OSX Image Capture Utility to scan instead of the Canon IJ Scan Utility..
Copying, and printing works fine. As does scanning with the ADF.
The tech was not able to fix the issue.