From Canon USA:
Thank you for using Canon products.
We would like to offer our sincere apologies to users who have been inconvenienced by the phenomenon described below. We value the trust our customers have placed in us, and we are dedicated to continuously improving product quality as well as delivering industry-leading service and support.
In rare cases, error 70 or error 80 may repeatedly display on some EOS 70D digital SLR cameras due to an internal communication failure resulting from the structure of the electrical printed circuit board. If use of the camera is subsequently continued, a state may occur in which the camera’s power does not turn on. In most cases, this phenomenon occurs in conjunction with continuous use of the camera while the camera’s internal temperature is high, such as when shooting movies continuously.
“Err 70” or “Err 80” will appear on the LCD monitor at the back of the camera or on the LCD panel at the top of the camera. There may be rare occurrences of error 70 or error 80, after which the camera functions can be recovered by turning the power off and on again, or by re-installing and reinserting the battery. The phenomenon described here refers to the frequent reccurrence of error 70 or error 80.
Possibly Affected Cameras
Only some EOS 70D digital SLR cameras are affected by this phenomenon.
The phenomenon may occur only in cameras whose first two digits in its serial number are within the range of “00” to “22”.
EOS 70D digital SLR cameras on which error 70 or error 80 occurs repeatedly and that have a serial number within the range specified above will be inspected/repaired free of charge. Please note that inspection/repairs for any other issue will be handled as normal repairs.
If you wish to make a request for the free inspection/repairs, please bring the camera body only with the body cap attached to a Canon Service Center.
If you have not already done so, please register your EOS 70D so that we will be able to notify you via email about any future service upgrades.
This information is for residents of the United States and its five territories only. If you do not reside in the USA or its five territories, please contact the Canon Customer Support Center in your region.
Customer Support Operations
Canon U.S.A., Inc.