[Q] Galaxy S3 stuck at boot. Failed to mount Data, failed to mount EFS

Hello, I have a Galaxy S3 (GT-I9300) phone that is not feeling so well.

On startup it freezes indefinitely on the Samsung boot logo.
I am able to get into recovery and download mode.
In recovery I get errors - unable to mount Data, and unable to mount EFS.

The phone is recognized by the computer, both in Kies and Odin so flashing is possible.

It is not rooted and completely stock. Problem is that I don't know what version firmware it had.

There is unbacked information on the phone I'd like to recover.

What I've tried: Within Kies>Firmware upgrade and initialization (second option under tools) I enter the model number and then the serial, but I just get a message along the lines of "please check your model" (I entered GT-I9300).

The phone is generic international version from 2012, untouched (version-wise) since.


I very much appreciate any idea that might fix this. How can I find the right firmware? will it erase my memory? how can I restore the EFS partition?

Tkkg1994 said:

Hey there. Creat a free account on the Sammobile Website. Than you can download this file from here:


Flash it through odin as PDA. Should work fine

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Will it work even though it is intended for Android 4.3? The phone originally came with 3.0 or 3.1

Also I believe flashing firmware will not fix EFS?

Tkkg1994 said:

Yes it does. It comes with 4.0.4 out of the box And it will work

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YES! the new firmware fixed it completely. It is a bit slow, but alas that's probably the phone itself.

To anyone looking in the future:
This problem was caused by a faulty battery - the phone would turn off while working all the time, and eventually it corrupted the data and efs partitions. To my luck upgrading to new firmware fixed the problem.

Thank you.:good: