Naturally, many iPhone owners are eager to upgrade to 4.1 as soon as possible. If you rely on a jailbroken or unlocked iPhone 4, however, you absolutely must hold off the upgrade until the iPhone Dev Team releases new tools to keep the jailbreak/unlock alive beyond 4.0.2.
IMPORTANT: The following tutorial will upgrade your iPhone 4 to iOS 4.1 while preserving your current (unlockable) baseband. Your iPhone will not be jail-broken, however, as there currently is no jailbreak for 4.1 You can only revert back to 4.0.1 or earlier (to jailbreak and unlock your iPhone) if you’ve previously saved your SHSH Blobs for 4.0.1 or earlier! If you’re not sure what this means, then PLEASE stay away from this tutorial! You’ve been warned!
Quick 4.1 Firmware/Baseband Backstory
If you’ve previously saved your SHSH Blobs with TinyUmbrella you’ll always be able to downgrade your iPhone 4 to an earlier firmware version.
For example: if you saved the SHSH Blobs for 4.0.1 you could always use TinyUmbrella’s TSS service to downgrade back to that version even after you upgraded to 4.1 through iTunes. Currently you can NOT downgrade your iPhone’s baseband, however.
So even though you could always revert back to software 4.0.1 (if you’ve got the blobs that is), there’s currently no way back to iPhone 4′s original 01.59.00 modem firmware (the baseband). And currently, 01.59.00 is the only baseband for iPhone 4 that works with the UltraSn0w unlock. iPhone 4.1 will upgrade your baseband to version 2.10.04 which, as of this moment, doesn’t (and may never) work with any unlock.
Hence, if you care about the unlock, it’s best to stay away from 4.1 for the time being. If you’re eager to play with 4.1, however, and don’t need the unlock right now, but simply would like to keep your options open for the future (until there’s an official jailbreak for 4.1, for example), TinyUmbrella 4.1.3 will help you upgrade your firmware without touching the baseband!
Upgrading to 4.1 While Retaining Original Baseband
WARNING: proceed on your own risk. Do not attempt if you’ve not saved your SHSH Blobs and may want to downgrade back to 4.0.1 or earlier!
WARNING #2: even if you have saved your SHSH Blobs, proceed on your own risk! Don’t do this if you ABSOLUTELY must rely on the iPhone 4 unlock!
1) Download TinyUmbrella 4.1.3
2) Close iTunes
3a) Some users are reporting 3002 errors. Saving your iPhone 4.1 SHSH Blobs before proceeding may help. (See 3b – 3d). Thanks to Joe and John D.
3b) Click Save My SHSH to save your 4.0.1 or 4.0.2 SHSH blob
3c) Check the Advanced Options
3d) In the Device/Version box, select iPhone 4.1 (8B117)
3e) Click Save My SHSH again to save a 4.1 SHSH blob
3d) Make sure iTunes is still closed
4) Start the TTS Server
5) Make SURE TinyUmbrella doesn’t report any errors! (If TU reports ANY errors it may not protect you from a baseband upgrade. In that case do NOT proceed!)
6) Start iTunes and restore to iOS 4.1. (Important: You must restore, not update!)
7) Accept the iOS 4.1 Update.
8 ) Cross your fingers. Hold your breath.
9) After the update is complete, don’t panic if iTunes shows the following error messages: “The iPhone could not be restored. An unknown error occurred (10044).” and “iTunes has detected an iPhone in recovery mode. You must restore this iPhone before it can be used with iTunes.” Simply press “OK” on each and proceed to the next step.
10) Return to TinyUmbrella and select “kick device out of recovery”.
11) Your iPhone should now restart and be recognized by iTunes. If everything went well your iPhone 4 is now running iOS 4.1 with baseband 01.59.00. Congratulations!
Keep in mind that you currently won’t be able to jailbreak (and therefore unlock) your iPhone 4 on iOS 4.1, even though, you preserved the original baseband.
If, at any point, you’d like to return to iOS 4.0.1 or 4.0.2, in order to jailbreak or unlock your iPhone 4, simply follow the steps posted here.
And, please remember to proceed on your own risk!