If you’ve made the mistake of upgrading to 3.1.3 before checking if there was a jailbreak option available for the new firmware, fear not because you are not alone! I have done a bit of research and found several bits of information on different sites so decided to write this article and aggregate all the details in one place.
Following the steps below I have managed to get my iPhone 3G back to firmware 3.1.2 and then use blackra1n to jailbreak it again. Please note this is likely to erase all the current data on your phone so make sure you have recent backup of your apps, media and settings (this should happen automatically everytime you synchronise your phone anyway!).. Also it is important to note that this method will not downgrade your baseband!
You will need to have some understanding of computers to get through this tutorial but I have tried to keep it as basic as option:
1. Firstly you need to download firmware 3.1.2 to your computer. You can find the right version for your phone on the iClarified site. Save this file to your Desktop as we will need to use it during the restore process.
2. Open iTunes and connect your iPhone using the USB cable. If you haven’t synced your phone in a while now is a good time to do it so you can make sure there’s a recent backup of all your data.
3. Once the sync is finished, go to the iPhone summary screen (screenshot below) and OPTION+CLICK (Mac) or CTRL+CLICK (PC) the restore button. This will open a window for you to select the firmware file you wish to restore. Navigate to your desktop and click on the file you downloaded in step 1. The restoring process will begin.
4. After a few minutes a phone boot ups your device will have finished the restoring process but you will receive a 1015 error. DO NOT WORRY, this is actually good and it means the firmware was downloaded and installed properly.
5. Download iRecovery from this link (PC and Mac versions available). If you are on a PC you will need to install the usblib file that is part of the archive and then install the latest version of iRecovery which can be downloaded from here.
6. Once iRecovery is installed, run it from the command line by typing “irecovery -s”. Wait for the ] prompt and type the following. In my case I waited for quite a bit for the ] prompt and it didn’t appear so I pressed enter a couple of types and the ] prompt finally came up.
] setenv auto-boot true
] saveenv
] /exit
After the last line you should be taken back to the command line prompt which is now safe to be closed.
7. Reboot your phone by holding the HOME + POWER buttons for about 10 seconds. Once the phone is booted go to SETTINGS -> GENERAL -> ABOUT to confirm that the firmware is in fact the 3.1.2 (screenshot below).
8. You are now ready to jailbreak your phone again using blackra1n which can be downloaded here
9. Once blackra1n works its magic and the phone is restarted, open iTunes and synchronise your media files and applications back to the phone. Please note that if you have installed any apps using IPAs downloaded from websites other than the iTunes / Cydia / Rock store, you will need to install the AppSync for OS 3.1 patch which can be found at the Hackulous repo http://cydia.hackulo.us/
I hope this method has worked for you as well and feel free to let me know or add any comments or tips in the comments section below!