How to Downgrade iPhone Firmware From 4.0
- 1). Visit the firmware software site (see Resources), and click the firmware link to download the iPhone 3.1.3 firmware to your computer. Click the downloaded firmware to highlight the file, and click it again to change the filename from "zip" to "ipsw." While the firmware file downloads as an .ipsw file on Macs, PCs will save the file as a .zip file.
- 2). Insert the dock connector USB cable into the bottom of the iPhone and into the computer's USB port. The iTunes program automatically launches when the computer detects the iPhone's connection.
- 3). Click the iPhone's icon in the left source pane or side menu, and click "Summary" in iTunes.
- 4). Hold down the "Ctrl" key on your PC or the "Option" key on your Mac, and click "Restore" in the iTunes summary window.
- 5). Click the 3.1.3 firmware file, and click "Choose" or "Open." Click "Don't Back Up," then click "Restore" in the dialog box. The iTunes program automatically launches the firmware and installs the 3.1.3 firmware over the existing iOS 4.0 firmware. Leave the iPhone connected while iTunes restores the firmware; disconnecting the phone can cause an error that would require you to restart the device restore process.
- 6). Click "Controls" and "Eject iPhone" from the iTunes menu after the firmware is installed to the iPhone.
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