Error code 5100 on Canon inkjet printers

Solution 1:

• Look inside for a tiny object like a piece of paper, a staple...

Solution 2:

• There is a thin plastic strip running across the width in front of and below the drive belt: there are fine black vertical lines on this strip. 
• If the strip gets a piece of crud on it, you get an error during the start-up sequence.
• Gently clean this strip with a damp lint-free tissue.

Solution 3:

• The purge cap (the white sliding mechanism that the print head parks to when it's not in use) may be not lubricated well enough. 
• Lubricate the sliders with some white grease (don't get it on the small wipers or the black caps).
• This repair probably require to remove the right panel off of the printer to gain access to the purge mechanism.