http://tallyns.blogspo​t.com ...error-codes-revealed.html

Hope this is helpful.

Thanks for this. I've yet to receive an error code (somehow), but I'll certainly be bookmarking this in the event something goes wrong which will likely keep me from punching a hole in the wall (which my landlord will appreciate).

I just found this thread, and just in case the link goes bad one day, I'll post the error codes here:
(that way I can find them again if I need to)

01"- "Communication between the camera and lens is faulty. Clean the lens contacts."
10 - Malfunction related to files has been detected.
20 - Malfunction related to the mechanical mechanism has been detected.
30 - Malfunction related to the shutter has been detected.
40 - Malfunction related to the power source has been detected.
50 - Malfunction related to the electric control has been detected.
60 - not used on 5Dm2
70 - Malfunction related to images has been detected.
80 - Malfunction related to the electric control of images has been detected.
90 - not used on 5DM2