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How to Update iPhone 4 to iOS 4.2.1 and Preserve Baseband

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With the updated release of Greenpois0n for iOS 4.2.1, users of all iDevices can once again jailbreak to their heart’s content. If you own an iPhone 4, and want to preserve your baseband when updating to iOS 4.2.1, you can do so with TinyUmbrella.

Here are the exact instructions, but I’ve included relevant download links:

You can protect your iPhone 4 BB restoring to iOS 4.2.1. Follow these steps exactly:

1. Get the latest TinyUmbrella. OSX. Windows.
2. Get the latest greenpois0n rc5 update (http://greenpois0n.com)
3. Open TinyUmbrella
4. Plug in your device and save SHSH (make sure 4.2.1 SHSH were saved, if not don’t bother continuing)
5. Start TSS Server (If you get errors read the help section or FAQs or comment below typically it fails because you have some kind of web sharing enabled… use google to fix it – your issue really not much I can do…)
6. Open iTunes
7. Select your device in iTunes
8. Shift(windows) / Option(Mac) restore -> Select the 4.2.1 ipsw
9. Restore SHOULD error with a 1013 error. Click the “ok’s” and close iTunes.
10. With your device sitting with the usb pointing to iTunes (recovery mode), enter DFU by pressing and holding HOME + POWER until your screen goes black… then after a count of 2 (1.5-2 seconds) let go of POWER but keep holding HOME. If all goes well you will see nothing but a black screen. If your timing is even a LITTLE bit off, you will see the apple logo and your phone will boot back into recovery mode… Go back to step 10 and try again.
11. You’re now in DFU mode. Start greenpois0n and press ‘Jailbreak’
12. Once greenpois0n has finished its thing. Press ‘Complete!’
13. Let your device restart. You should end up on the activation screen.
14. Congrats your baseband was preserved and you are now on 4.2.1

If you get a 16XX error then try entering DFU and go to step 5.
If your restore does NOT end in a 1013, it means your baseband was updated. This is likely because you did not have the TSS server running OR you updated without TinyUmbrella OR you are working with a device OTHER than iPhone 4.

As always, with jailbreak-related tutorials, research first before attempting anything. You do so at your own risk and we are not responsible if you somehow damage your device. The choice is yours. If you run into trouble, check out the comments on The Firmware Umbrella link below.

[The Firmware Umbrella]

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  • TonygBaker

    Hi Gary,

    Thanks for this. It’s a huge help. I was just wondering if it is the case that apple has stopped signing for the 4.2.1 firmware? While doing some reading before going ahead with the update I came across some sites that were saying this is the case. Will this pose a problem? Thanks for your help.

  • Mark

    For number 5 if you get the error most likley you are running a web server like IIS for windows. I was running IIS and I uninstalled it and that solved my problems.

  • So does this mean that if I’ve preserved the BB since I got the phone in July, and still have 1.59, then can I still unlock it with ultrasnow?
    What about preserving the 3GS?

  • Mark

    Yes if your running 1.59 you can preserve your baseband on the iPhone 4.
    What baseband are you running on the 3GS?

  • TonygBaker

    Does anybody know once greenpois0n is finished whether you have to reactivate my phone or can I just restore from a backup? I’m upgrading from 4.1 while living in England and I don’t know what will happen if I reactivate my phone while not being on the Rogers network. Thanks so much.

  • Ex

    Restore from backup

  • TonygBaker

    Brilliant! Thanks so much for your help. And thanks to both you and Gary for these guides. They’re fantastic!!

  • Ex

    Anytime!

  • Anonymous

    nope I get a window popup that says itunes in the upper left hand corner and it asks me to look on my pc to find the .ispw file. Any help? thanks!

  • Nthammareddy

    Don’t do a custom restore (using shift + Restore) instead if you are on IOS 4.1 then after editing the host file click on UPDATE on itunes and Not RESTORE.
    It worked for me that way….

  • Jailbreaking is Cool

    download the 4.2.1 firmware from a trusted source and if it downloads as a zip file just rename the extension to ipsw.

  • Anonymous

    I’ve tried that before but whenever I get that popup window for me to ‘search” for the file on my desktop….the file never shows up in that popup window for iTunes!!!!!

  • Anonymous

    I am on 4.1 so do I follow the above directions BUT instead of clicking on (shift + restore) I click (shift + UPDATE) instead?

  • Anonymous

    I’ve renamed the extension but when I go to “open up the file on my desktop it wont’s show up. I tell it to look in the file but it shows up as blank in the file name box. This is the file name: iPhone2,1_4.2.1_8C148a_.ispw

  • 5.13.04 iOS 4.0.1 jailbroken and unlocked with ultrasnow. Want to get it to 4.2.1 but need to keep the unlock. Ideas?
    And confirming you mean that my jailbroken iPhone 4 on 4.2.1 with BB 1.59 can be unlocked with the current ultrasnow?

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