You will want to perform this tutorial if you accidentally updated to the 2.0 firmware or you just rather be on 1.1.4.
To follow this tutorial you will need to have iLiberty (Windows, Mac), iTunes 7.5 (Windows, Mac), and the 1.1.4 firmware.
If you have Windows, uninstall iTunes 7.7 and then reboot your computer.
If you have Mac OS X, open Terminal from Applications:Utilities. Enter the following commands into the Terminal window:
defaults write com.apple.iTunes StoreActivationMode -boolean NO
defaults write com.apple.iTunes StoreGeniusMode -boolean NO
rm -r /Applications/iTunes.app
rm -r /Library/Receipts/iTunesX.pkg
Install iTunes 7.5 onto your computer using the download links provided above.
Before attempting to launch iTunes 7.5 for the first time you need to delete or rename the iTunes folder.
Rename the C:\Documents and Settings\**your user name**\My Documents\My Music\iTunes folder to iTunes Backup.
Mac OS X:
Select the iTunes folder in your Music directory and rename it iTunes Backup. You press the Enter key to rename a file in Mac OS X.
Launch iTunes by selecting its icon in the dock.
Put your iPhone into DFU mode by: connecting your iPhone to iTunes like you always do. Making sure it's on. Once itunes recognizes your device hold down the power button and the home button at the same time. KEEP holding it untill it turns off, reboots and the "connect to itunes" symbol will appear on your screen. Ones it does you will get a pop up from itunes.
iTunes will notify you that it has found an iPhone in recovery mode. Click the OK button.
Hold down Option and press the Restore button. If you are using Windows hold down Shift and press the Restore button.
Select the iPhone 1.1.4 firmware file you downloaded earlier and click the Open button.
Once the restore has completed you will get a 1015 error or similar.
If you get an error in the 1600s then try putting the iPhone into DFU mode and try again. You might also want to try a different USB port and restart your system and if all else fails use a different computer!
Now you can use your favourite unlocking method to kick your iPhone out of restore mode and unlock it.
Below are some instructions to help you with the more popular methods...
iLiberty+ _ iLibertyX_ guides for Windows-Mac
PWNAGE: Unlocking tool by Dev Team_guides here
The first time I tried this I opened iLiberty+ with iTunes still open. It immediately kicked my phone out of recovery mode and then the application closed down. I reopened it and then was able to unlock successfully on my first attempt.
Select Software Update from the Apple Menu at the top left hand corner of your screen.
Select iTunes 7.7 from the list of software available for install and click the Install 1 Item button.
For windows users just reinstall iTunes 7.7 from the Apple website here
Once installation of iTunes 7.7 has completed you can rename the folder iTunes Backup created in Step Three to just iTunes. You will then get your library back!
I have only found one method for downgrading the baseband easily. I have done this myself twice with no ill side effects, yet... This program calls itself a "patched" version of z i p h o n e, but it is NOT the actual program. It will only downgrade your baseband, it will not do ANYTHING else.
I do not endorse the use of the actual z i p h o n e program as it has harmed more iPhones than anyone can count (regardless of what its creator claims). To read more about the DANGEROUS side effects of this program, read this.
You use this patched program completely at your own risk.
The program can be downloaded here.
You can read a thread discussing this program here.
All you have to do is check the box for Baseband downgrading, then click the Start button.
It will finish in about three minutes. You should now have a cellular signal again. You will be on 1.1.4 firmware, but you will have 1.1.3 baseband (04.03.13_G). You could restore the iPhone again back to 1.1.4 to put the correct baseband on, but you don't have to.