Downgrade iPhone 3Gs 3.1.3 To 3.1.2 For Mac

Let’s say you accidentally upgraded your iPhone 3GS to 3.1.3, then you managed to downgraded to iPhone 3.1.2 but facing the inconvenient result, because you are experiencing no service problem on the iPhone 3GS, then the tutorial of this post might become a helper to solves your no service problem after downgrading your iPhone

In this tutorial we will try to get your iPhone 3GS 3.1.3 downgraded to 3.1.2 and jailbroken too, albeit the title says it’s downgrade to 3.1.2 for Mac but can applied to for Windows but previously I also posted about the same issue for Windows only here

1. Firstly made backup on Saurik’s server from Cydia before
2. Download iPhone 3.1.2 firmware
3. Play a little trick now to fool iTunes, by editing you Computer host, to make iTunes communicate with Saurik’s server instead of Apple, thus go to the following link to edit host file for Mac OS
4. Locate the following: 74.208.10.249 gs.apple.com at the end of the file and save it and at the time Terminal is open then you are exited the host file, then dscacheutil -flushcache and hit enter.
5. Locate the iPhone of yours in DFU mode, DO NOT, locate it in Recovery mode
6. This step for Mac only, click on your option key on keyboard afterward click restore on iTunes, then define or specify where did you save the downloaded iPhone firmware 3.1.2 (Look at the step 2 above)
7. An error message 1015 appears while restoring, stay cool, just wait your iPhone to reboot and the connect to iTunes screen come to appears
8. In case you are stuck on the connect to iTunes screen, download iRecovery from here iRecovery Package for Windows & Mac.rar .

   8.1 To start iRecovery on mac, simply open the command line applicaiton(Terminal), and then DRAG the iRecovery file from the location you’ve extracted it and DROP it inside the Terminal window and add to the end of the command line that is automatically written ‘-s’ so it should be ‘irecovery -s’.

   8.2 To start iRecovery on windows, first extract the iRecovery to the root directory “c: \” of your hard disk, then run the exe file ‘libusb-win32-filter-bin-0.1.12.2.exe’ already contained in the archive downloaded in step 7, then open windows command line application ‘cmd’ and type ‘irecovery -s’ while you are at c: \

   Windows users : BEFORE INSTALLING libusb-win32-filter-bin-0.1.12.2, right click the file and set it to run under compatibility mode for Windows xp sp2. Thanks to gangsta415 and pappajohn for pointing that out, as i’m not a windows person

9. Let’s say you face the command line empty, yous should type in the following :
   setenv auto-boot true press enter
   saveenv press enter
   /exit press enter
10. Reboot your iPhone by pressing and holding the sleep/power button and the home button until the iPhone display turn off.
11. Insert you SIM card to iPhone.
12. While the iPhone is still connected to your computer and iTunes running, Start your iPhone normally by pressing on the Sleep/Power button.
13. Your iPhone will get ACTIVATED by iTunes so just wait
14. When it’s done, you are free to jailbreak to any techniques or any jailbreaking tools available but Blackra1n is a good choice.
15. Done!

Hope it helps!

Source Rafay