How do you fix a CFast card that stops in a Canon 1DXMII camera?

“My CFast Card Stopped Working in a Canon 1DXMII. What’s the solution?”


The following is a quick troubleshooting exercise to resolve the issue of a CFast card stopping in the Canon 1DXMII Camera:


CFast Card Formatting

Delkin has found that a full “deep format” of the card via PC or Mac will refresh the card so it will continue to perform properly. A “quick format” only erases the table of contents, not the actual information. As you write to the card, it must erase and write new information “on the fly”. After a few quick formats, there is a buildup of scattered and fragmented garbage files that need to be erased as you write to the card. This will slow the card down, which will affect your sustained write speed, resulting in the camera stopping its current activity. A Deep format removes these garbage files and completely erases the card, bringing to back to a “like new” state.


Here is a link to our product notification and instruction for refreshing Cfast memory cards:  


Here is a link to the Canon 1DXMII Spec which states:

“Proper operation cannot be guaranteed for all recording media. Long term usage may reduce a CFast™

card’s write speed. We recommend users regularly fully format and refresh their card using the

“Full Format and Refresh Tool.”



Delkin Devices Warranty

Delkin products have a lifetime warranty against manufacturing defects. If there is an issue with the card, we are happy to authorize a return for evaluation and repair or replacement.

If you still feel there is an issue with your card, please provide your address and contact information, and we will authorize a return for evaluation.

Please email us at