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I tried to format my SD card on my Windows computer but unfortunately I pulled it out during the process. Now it can't be recognized. I tried to wipe it using disk utility on Mac OS X but after it's done and I click "check disk" I get the message:

Partition map needs repairing: there is a problem with file system of the system EFI partition.

This may be not the exact message you get in english - I translated it. How to repair the card? Using the "repair disk" button in disk utility it goes without problem but after unmounting, ejecting and putting the card in the card reader again yields the same problems.

EDIT: I tried everything I found on the net - no success. Now I get the following message in disk utility:

** /dev/disk1s1
Invalid BS_jmpBoot in boot block: ffffff

Any idea?

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  • I suggest you copy entire sd with raw command and do experiment to that copy.
    – Pol Hallen
    Dec 20, 2013 at 21:59
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    Just write a MB or so of raw zeroes to the card. Then you should be able to re-partition it. You can use something like sudo dd if=/dev/zero of=/dev/disk1 bs=1024 count=100. Just 100% triple-check that /dev/disk1 is the SD card!! Apr 30, 2014 at 6:37
  • I had similar issue and @DavidSchwartz's suggestion worked for me - however I also had to overcome a permissions issue by blowing air and tapping my card reader port 😅
    – danwild
    Apr 11, 2020 at 0:40
  • Found this comment, solved the problem for me too. You should put this as the proper answer! Mar 9, 2021 at 15:20

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