How to Update iPhone 3g/3gS & iPhone 4 to Custom iOS 4.2.1 Preserving your Baseband

This video describes how to update your iPhone 3g/ 3gS or iPhone 4 from any firmware lower than 4.2.1 to a Custom 4.2.1 Firmware. It could be 3.0, 3.1, 3.1.2, 3.1.3, 4.0, 4.0.1, 4.0.2, Custom 4.1. In other words if your baseband is 4.26.08, 5.11.07, 5.12.01, 5.13.04, 01.59.00 then you can successfully follow this video directions. And if your baseband is 5.14.02 or 5.15.04 then you will need to follow the video given at the end of this written description. All this will be an Untether way of Jailbreak covering both new or old bootrom for your particular devices.

METHOD: First use Redsn0w 0.9.6b6 to put your iPhone in Pwned DFU mode so that it is able to accept Custom Firmware file. When iDevice in Pwned DFU mode then simply open iTunes and hit Shift + Restore (Windows) or Option key + Restore (MAC) and load in Custom 4.2.1. Sit back and relax till updating/restoring process is done. When it is all ready then simply install “Ultrasn0w” from Cydia. You will be fully Unlocked and Jailbroken on 4.2.1 Firmware.

Download Redsn0w for WINDOWS:!Qw8QXCBA!RSIEDz-XHViVsPPmmkYqXAODMVgigSNKvzP_cp358EM

Download Redsn0w for MAC:

IF above Redsn0w gives you issues while running, then run these versions of Redsn0w

Download Official iOS 4.2.1 firmwares (Browse in Redsn0w 0.9.6b6)

Below are the CUSTOM 4.2.1 Firmwares: (Browse in iTunes)

Custom 4.2.1 Firmware for iPhone 3g –!Ql1WHJCJ!WQvhJhahSrt1XGo7a0H2ElURdzJML065LD1gZAYvqFs
Custom 4.2.1 Firmware for iPhone 3gS-
Custom 4.2.1 Firmware for iPhone 4 –

Users with iPhone 3g or 3gS and have updated to Official 4.2.1 firmware directly through iTunes need to follow this video to Unlock their devices

[Here is a complete list of errors while Upgrading/Downgrading an iPhone/iPod Touch or iPad Firmware]

NOTE: (ONLY iPhone 4 Users): This video is for unlockers. The custom firmware used here are ‘hacktivated’ and you will NOT get a service if you use these with official sim cards on your iPhone 4. You will have to use Pwnagetool (MAC) or Snowbreeze (WINDOWS) to make your own custom 4.3.1 firmware and make sure to Uncheck ‘Activate iPhone’ option when you make a custom firmware using pwnagetool or snowbreeze. Then upload that on your iPhone. You will get your reception back on iPhone 4.

All Credits go to:

Happy Jailbreaking !!

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  1. hi emac, i have been trying to download the custom 4.2.1 firmware for 3g but i have been having problems. It downloads to 99% but and freezes. Can you give me another link to the custom 4.2.1 firmware for iphone 3g ? Thanks

  2. hi buddy, great tutorial. I have a 3g on 4.0 and baseband is 5.13.04. I just want to know if something goes wrong will i be able to restore my iphone from back-up?

  3. Hello, you helped me fix my iphone 3g some time ago to 3.1.2.  Originally my phone was  jailbroken and on 4.2.1. I don't know what the baseband was at that point but I would like to update bk to 4.2.1 in order to have apps I had previously.  I am confused as to issues surrounding the importance of the baseband currently it's 06.15.00.

    Please could you point me in the right direction? 
    Many thanks in advance.

  4. Hi emac2299….I have iPhone 3gs(8GB).I was upgrading my iPhone OS 3.0.1 to 4.1.2 by using iTunes..when I connect my phone to iTunes then I saw message on screen that Updates are available to U..and I click on Update Button….then "Sync Processing" msg was come on my mobile sceen…and iTunes start updating…..after some time (30 min) mobile screen was turn to black and Apple logo was display on screen for some time….then it turn to black screen….and after that my mobile was not responding……nothing is happnd with mobile……..then I unplug my phone still nothing was happnd…after that again I pluge it to my Comp….and nothing was hppnd…. 🙁
    Plz help guys……I want to start my phone…. 🙁 :'(
    Help Me….

  5. hello plz reply as soon as you can bc im tring to do this now… im tring to download the official firmware and i'm having problems

  6. If you have an iPhone 3gs then this is not the right time to update. If you depend on Ultrasn0ww then stay where you are and wait for a new Untether Jailbreak. Unless you have an iPhone from ATT USA then send me its IMEI number and I will permanently unlock you riPHone.


    I deleted several ispw files making sure to use those from your site .
    The phone has been returned to factory settings.
    3G 4.2.1 BB 5.15.04.

    Network/Carrier Not Available. Phone indicates No Sim.
    Can connect to WiFi.

    I am figuring out what to do next?

  8. I am going to try again making certain I use the link from your site for the custom firmware. I have been to so many sites I don't know whether I'm coming or going.

  9. I did go ahead and try to upgrade 4.2.1 with correct custom file but iTunes says could not restore as firmware incompatible 🙁

  10. Thank you.

    It's in recovery iTunes logo at the moment; 3.1.2 BB 5.15.04.
    I am going to attempt a downgrade to 3.1 unless you suggest otherwise? Can I upgrade the current version from recovery mode?

  11. 1st option: All you need to do is put your iPhone in "pwned dfu' mode using Redsn0w. Once you have done this now launch iTunes and hit shift+restore and locate Custom iOS 4.2.1firmware that you downloaded from this video. Let it load, Done.
    2nd option: If above does not work, then put iPhone in regular dfu mode and hit shift+restore and load Official iOS 4.1 (not 4.2.1) firmware. Now iPhone will be downgraded to 4.1. You will get stuck on emergency screen. Then follow 1st option as written abov

  12. I made a really stupid mistake in attempting to ugrade to 4.2.1. I used 4.1 custom ipsw by mistake and not 4.2.1. Stuck on Apple logo now. Have managed a few times to get the iTunes/USB logo recovery mode but it reverts back to the apple. Have I killed it? Please tell me what I should try to do.

    Thank you again 🙁

    Thank you yet again

  13. I installed iOS 4.2.1 on my iPhone 3G and wanted to unlock it using Ultrasn0w. When all was done, when I get into cydia, and try to install Ultrasn0w, it says Cannot Comply and at the bottom: Depends iOS Firmware >=3.0
    I have iOS 4.2.1, Baseband 6.15 so what is the problem? Please help!

  14. Sure it will. Make sure to backup iphone before starting . After all process is completed install Ultrasn0w and re-run Redsnow and check Install iPad baseband option again if you don't see your service.

  15. sir emac2299 please reply..
    will this work if my iPhone 3g baseband is 6.15.00?
    thanks in advance ^_^

  16. emac2299 plz replay I have a iphone 3G with Baseband 6.15.00 and can I update my iphone 3G with custom firmware

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