Previously, I’ve downgraded my iPhone 3GS from firmware 3.1 to 3.0. However, my Singtel sim card was not detected and the iPhone 3GS has totally no Singtel carrier network. But, now I manage to fix it. If you’re having the same issue, here’s the solution.
Please note that your device/iPhone 3GS must has a 3.0 ECID SHSH on file before you’ve updated to firmware 3.1.
Please skip entire guide if you don’t see the wordings “This device has a 3.0 ECID SHSH on file” on Cydia home page when your iPhone 3GS is on firmware 3.0.
Downgrade iPhone 3GS 3.1
- Uninstall iTunes 9 and install iTunes version 8.2.
- Close the iTunes if it’s running. Run c:\windows\System32\drivers\etc\hosts and open with Notepad. Add 188.8.131.52 gs.apple.com at the last line and save it.
- Put your iPhone 3GS to DFU mode and shift restore to firmware 3.0 through iTunes 8.2. You’ll get error (1015). Shift restore to firmware 3.0 again and you’ll still get error(1015).
- For official iPhone, jailbreak your iPhone 3GS using purplera1n and then unlock it through iTunes.
- For non-official iPhone, jailbreak your iPhone 3GS using redsn0w and you’ll not be able use the ultrasn0w to unlock as the iPhone baseband was being updated on firmware 3.1. You’ll probably need to wait iPhone dev team to release the unlock for baseband 05.11.07.
For more information about iPhone 3GS downgrading, click here.