How To Downgrade 6.15.00 Baseband On iPhone 3G 5.08 Bootloader?

Good news for people who updated their Basebands on iPhone 3G to 6.15.00. Now you can downgarde your baseband back to 5.13.04. So you can update and restore any firmware without iTunes give you errors.

  • Jailbroken iPhone 3G;
  • Fuzzyband installed via Cydia
  • afc2add installed via Cydia;
  • iFunBox (for Windows) or DiskAid (for Mac)
  • Certified for use with Fuzzyband be downloaded from HERE

  • Download the certificate ICE2 06.15.00.cert-HERE
  • Install Fuzzy Band through Cydia. (It is important to verify that the application starts, you say that your boobloader is 5:08,( if not so the procedure should not be performed)
  • Connect the iPhone 3G to Computer
  • Start i-FunBox or Disk Aid and click File, then navigate toApplications/, right-click and then select Copy from PC.
  • Select the ICE2-06.15.00.cert file you downloaded earlier and then copy it to this location: Applications/
  • Now simply disconnect your iPhone from your computer and start Fuzzyband app (which you previously installed using Cydia) on your iPhone.
  • In Fuzzyband, you will now see your current version of Baseband, (which should still be 06.15.00). But now you will have the option to downgrade it to version 05.13.14.

Once you have downgraded, Go to Settings > General > About and scroll down to check your Modem Firmware which should now read 05.13.14 (which is unlock able via Ultrasn0w). You can now also update or restore any firmware without iTunes given any errors.

This method currently only works with the iPhone 3G with bootloader 5.8. We also recommend that you backup data to restore your device in case something goes wrong in the execution, you do at your own risk. Here is the video for help you more.