Downgrade iPhone v2.2 to 2.1 Firmware

If you accidentally upgraded your iPhone to the latest v2.2 firmware and discovered that you lost all your third party jailbroken apps, you have the option to either jailbreak the 2.2 firmware or simply downgrade your iPhone firmware back to v2.1. Should you desire to go down the downgrade route, this guide is for you.

1. Download the 2.1 restore ipsw firmware for 2G or 3G iPhone.
2. Connect your iPhone to your computer via the USB cable.
3. Start iTunes 8.0 (versions up to 8.0.2 will work).
4. Under the devices tab, select your iPhone in iTunes. If iTunes does not read your iPhone, you will need to put it into DFU (device firmware upgrade) mode. To do so, first power off your iPhone. Then press and hold the Home and Power buttons together for 10 seconds exactly. After ten seconds, release the Power button but continue to hold the Home button until your computer makes the same beeping noise it makes when a USB device is detected. You may see an alert that a DFU device has been detected. When this happens your phone is in DFU mode and you can release the Home button.
5. On Windows, shift-click the Restore button. On Mac, command-click the Restore button. You will be prompted to select the ipsw firmware file, simply browse to the file you downloaded in step 1 (iPhone1,1_2.1_5F136_Restore.ipsw or iPhone1,2_2.1_5F136_Restore.ipsw).
6. iTunes will proceed to downgrade your iPhone back down to 2.1 firmware. If you encounter any 10xx series error messages, simply click OK to ignore them. If you get 16xx error messages, your phone is not in DFU mode so go back and try it again following the instructions exactly in step 4.
7. Follow our guide to jailbreak 2.1 firmware to get your third party apps back.

Note to 3G iPhone users:

If you installed the 2.2 firmware update, your baseband firmware got updated as well. This means if your iPhone is unlocked via a hardware SIM card solution, it may cease to work. This downgrade guide will not help you downgrade the modem firmware, when we have that information we will post it so keep checking back. This downgrade guide is meant for 3G users on the AT&T network who want just to jailbreak their apps again.