Managed to find a free manual on-line but does not cover errors:
There are sites that offer a manual for a fee. Manual is not available on the canon sites.
Common cause of an E100 error is something in the way of the laser path or a problem with the laser unit.
Check the drum unit to make sure there is no problems that would prevent activation of the laser unit shutter .
Check the beam detect reflecting mirror inside the laser box and carefully clean with a dry cloth; this
is reportedly a likely cause.
On the iR550 the laser shutter is actuated by the front door interlock. The laser shutter is a protective feature designed to prevent accidental exposure to laser light while you're removing jams.
If the interlock assembly is loose or the plate is bent or it is sticky it will cause an E-100. You can remove the shutter and not have a problem. If you need to remove the Beam Detect sensor for cleaning, mark the spot so it can be replaced in the exact spot or you could have problems with it seeing the beam.
if you are able to resolve
the E100 error message you may be interested to know that the Canon site does have updated drivers available here
You may want to check to see if you have the most current driver for your printer and operating system. If not, uninstall
your current driver and download and install a new driver for your operating system.