This tutorial will show you how to upgrade your iPhone 4 to iOS 4.1 without upgrading its baseband using TinyUmbrella for Mac. We recommend reading the TinyUmbrella Read Me located here before doing anything. The Windows version of this tutorial is here.
Please Note: This ONLY Works with the iPhone 4!
Download TinyUmbrella from here Also make sure to download the iPhone 4 iOS 4.1 Firmware located here
Double click the downloaded Umbrella.dmg file to mount it. Drag the Umbrella app from the mounted dmg into your Applications folder. Then double click the Umbrella app to launch it.
**If you haven’t already saved your SHSH blobs then click Save My SHSH.
If you do receive an error, DO NOT continue. Your restore will not work if the TSS server cannot be started.
iTunes should give you error 1004. This is what we wanted, as it notes the baseband has not updated
*If you have issues here, try closing and re-opening TinyUmbrella.
Your iPhone will now be on 4.1 with the 1.59.00 baseband!
**Thanks to semaphore for his work on this tool