Today, a tutorial appeared on BigBoss's blog (the one that also has the Cydia repo) that says it allows those with iPhone 3GS and iOS 4.0.2 without SHSH saved to downgrade to iOS 4.0.1 without Cydia without SHSH without nothing. I tried that tutorial on my phone and I only got error 3194, so the restore didn't work because Apple doesn't sign SHSH files for 4.0.1 now and without SHSH it's practically impossible to downgrade. Some say that the tutorial worked for them, but many say that they didn't manage to downgrade, I didn't either, so for now I say that this tutorial is fake and one works.
If you still want to follow the steps, you have them below in English and later in the evening I will redo them in Romanian:
1. Download 4.0.1 ipsw
2. Extract it with winrar or winzip to a folder on the desktop with. You may need to rename the firmware file from .ipsw to .zip to do this.
3. Open the buildmanifest.plist with the notepad. Search and replace all – 8A306 with 8A400. Save. Repeat the same with the restore.plist file
4. Download 4.0.2 ipsw and open this with winrar or winzip. Notes: do not exactly it. Just open it and leave it open. You must use this exact file and not create a new one. If you have to create a new one for reasons like you are on OSX, then use zip command line not explorer or finder to make the zip. I will assume you are using the original file opened in winrar for the rest of this guide.
5. Take all the files from the 4.0.1 and drag them over to the 4.0.2 zip archive that you have opened.
6. Delete all the dmg files that have 002 at the end, leaving only the 001 files left.
7. Save the archive. And rename it back to .ipsw if you changed the name to get winrar/winzip to open it.
8. Optional: (this helps ensure you get an shsh file request for the future, but should not be necessary to just restore 4.0.1). Add the 74.208.10.249 gs.apple.com line to the host file.
9. Put the device into dfu, open iTunes and restore the firmware you changed.
Check out the original post or give thanks to CodeBlue at his blog.
