[XDA]有關IMEI喪失

版上有許多人的SIII因為刷ROM或諸多原因導致 IMEI (EFS) 遺失，

在此引用XDA文章(http://forum.xda-developers.com/galaxy-s3/general/ref-imei-efs-stuff-i9300-including-t2393289)來為各位說明：

I have a 0049 or 0000 IMEI. Why?


This means your phone cannot read your IMEI. There are 2 main reasons for this.

1) /efs is corrupt.

Whenever you flash a ROM, be that a custom ROM via a custom recovery or an official ROM via Odin, you risk corrupting your /efs partition and losing your IMEI.

There are 3 main steps to take to try to resolve this
Restore your EFS from a backup - A logical first step
No backup? Reflash the latest stock ROM using Odin*
Send the device for repair**

*Ultima rom users (prior to v15), first reflash the rom, choosing a non-stock kernel during the aroma install wizard first. Boefla is a good choice to test.

** a couple with "cannot mount /efs" errors have fixed their device by flashing ics. If you know you haven"t got a VTU00M eMMC firmware 0xf1 - go for it. However for those of you who don"t know, this would be extremely dangerous. You could get SDS so I do not recommend this action. If you are foolish enough to try it, flash 4.1.2 immediately afterwards.


2) /efs partition format changed

A quick note before going forward... when looking at a ROM build number, the last 3 characters mean Year, Month, Revision. Let"s take XXEMG4 for example. M = 2013, G = July, 4 = revision 4. See "Other" section at the end of this post for more info

From July 2013 (XXEMG4) onwards, official Samsung ROMs change the format of your EFS Directory/Partition. Let"s say these ROMs change from EFS v1 to EFS v2. Only basebands from July 2013 (MG2) onwards can read EFS v2.

Quick info rules:
EFS v2 Basebands can read EFS v2 and EFS v1
EFS v1 basebands CANNOT read EFS v2, ONLY EFS v1

This means if you have flashed an official ROM (or custom ROM based on official) From July 2013 (MG* or newer), you are now in a situation whereby only an EFS v2 baseband (MG* or newer) can read the IMEI in /EFS.


If you have ever flashed XXEMG* (or newer) ROM, to keep your IMEI working, you must:
Stay with the EFS v2 basebands (MG* or newer). You may flash other ROMs but must return to the MG* (or newer) baseband
Restore your EFS backup (taken before XXEMG* or newer ROM install) to use older (EFS v1) basebands. EFS backup must be an EFSv1 backup to use an EFS v1 baseband
If the above don"t work, consider sending for repair...


*Ultima rom users (prior to v15), first reflash the rom, choosing a non-stock kernel during the aroma install wizard first. Boefla is a good choice to test.

Please note, it is flashing the ROM that alters EFS format, not the basebands themselves. You can flash the MG* or newer basebands safely on their own and return to an older baseband without issue.

You can download an EFS v2 baseband (CWM) flashable package HERE - updated to MJ3 by @maatsby
Aroma installer, choose between MG2, MG4, MH1 and MJ3 basebands
Basebands alone do not alter efs format
Backs up EFS in an uncompressed format (Use Root Explorer to restore)
Does NOT include RIL, works on AOSP and Sammy

For discussion of the efs format issue, see this thread.

文章中有提到IMEI碼消失、或是出現0049開頭的情形，都是因為手機無法讀取到IMEI碼出現的情況。而主要造成這種情況的原因有兩種：

1.EFS損壞

這種情況只能用三種方法解決：

1.從原先的EFS備份還原。

2.使用Odin刷入最新版本的官方ROM。

3.送回原廠修理(最終手段)。

2.EFS分區格式改變

從2013年7月以後，三星改變了官方ROM的EFS分區格式，可以說是EFS v1變成了EFS v2，但是版本2是可以向下兼容的，而版本1卻無法相容版本2，所以我們如果刷了XXEMG4以下的版本，我們可以用以下方法解決：

1.假如是使用MG4以上的版本2，可以試著更新你的基頻。

2.假如有做備份，可以從Recovery中還原(還原並不包含基頻，可以還原後再刷入較新的基頻)。

3.如果以上方法都沒用，請送回原廠維修。

分辨版本方法：

年)

L ─ 2012
M ─ 2013

月)

A ─ January
B ─ February
C ─  March
D ─ April
E ─ May
F ─ June
G ─ July
H ─ August
J ─ September
K ─ October
L ─ November
k ─ December

修訂版本)

1 ─ Revision 1
2 ─ Revision 2
3 ─ Revision 3
4 ─ Revision 4
5 ─ Revision 5
6 ─ Revision 6
7 ─ Revision 7
8 ─ Revision 8
9 ─ Revision 9
A ─ Revision 10
B ─ Revision 11
C ─ Revision 12
D ─ Revision 13
E ─ Revision 14
F ─ Revision 15

以下為台灣版軔體清單(可自行去Sammobile尋找)

                               
登錄/註冊後可看大圖

I heard I can manually modify my IMEI, transplanted from another device?

Modifying an IMEI is illegal in many countries. Even if this was possible, discussion here would be against the rules. Your IMEI must not be modified. Either restore a backup or send for repair.

另外文章中還有提到有關手動修改IMEI，或是從別人的EFS檔案還原。這些都是非法的行為，即使可行，對自身或是提供檔案的對方都會造成權益上的損失，千萬不要以身試法。

IMEI喪失本來就沒有比較完善的解決方法，請各位在改機時一定要做好備份，然後一定要對改機有一定了解後再行動，不然最後只能將手機送回原廠修理了。