On Canon Fax machines and multi-use machines that include printers, the E100 error refers to a printing fault on the machine. No new parts are usually needed, but the error can be annoying if it keeps repeating.
On the fax machine status screen, look for the "E100" error. It could also display as "E#100," "ERR 100" or "E100-0000."
The printer will only feed out blank pages and empty faxes, because the laser is not properly gliding on the printer cradle. It remains in the resting position and does not move.
Flip open the top to your fax machine. Look for a small shutter that holds the laser. Carefully force this open with your hands and force the laser out into the center of the tracking cradle.
After you move the laser, unplug the printer for a few minutes to let everything reset. Once you plug the printer back in, the laser shutter will reset itself and the error message will go away. Resume printing to make sure the laser works again.