After updating iOS 5.1 on March 7th, Apple also brought two new basebands (02.0.10 on iPhone 4S 04.12.01 on iPhone 4.

Those folks who rely on iPhone unlock will put themselves in a big trouble if they update their iPhone to iOS 5.1 but those who have a factory unlocked iPhone 4S or iPhone 4 won’t have any problems with these new basebands.

Downgrade 04.12.01 to 04.11.08 Baseband

The people who have TP SIM, R-SIM or Gevey Ultra S unlocked iPhone 4S could get into more trouble than the owners of iPhone 4. You will lose your iOS 5.0.1 Untethered Jailbreak once you update your iPhone 4S to iOS 5.1, but that is not all you will also lose you iPhone unlock because no solution has been updated the new baseband 02.0.10 for iPhone 4S. If you Update iOS 5.1 on your iPhone 4 then the damage has already been done – Don’t Update To iOS 5.1!

How to Downgrade 04.12.01 to 04.11.08 Baseband

– Required to Downgrade:

  • iPhone 4
  • iTunes (link)
  • iOS 5.0.1 IPSW firmware file (link)

Step 1: Connect your iPhone to Computer via USB cable and make backup (Recommended)

Step 2: Turn off your iPhone 4 and put it in DFU mode

-How to Enter in DFU mode:

  1. Hold Power and Home buttons together for 10 seconds
  2. Release the Power button and Continue holding the Home button for new another 10 seconds
  3. Your device now will be in DFU mode with (black screen)

Step 3: Launch iTunes, after launch iTunes, will recognize your iOS device in recovery mode. Now we are going to restore with downloaded IPSW file.

unlock iPhone 4

  • For Windows users: Press Shift+Restore
  • For Mac OS X users: Press Alt+Restore

Step 4: Now iTunes will restore your iPhone 4 to iOS 5.0.1 and your baseband will be downgraded from 04.12.01 to 04.11.08.

With 04.11.08 Baseband you have a better chance for unlock solution, Stay tuned to UnlockBoot and expect an unlock solution!

  • Nidoba11

    and when the solution for bb 4.11.08 will be relased

  • farsighted

    I did that and it didn’t work. I still ended up with 5.1 and baseband 04.12.01.  What happened to the part where the file turns to NO_BB_iPhone3,1_5_1_98176_Restore.ipsw? I’ll try again with the previous one I had from before.  Also, on the mac, the key is “option;” not Alt and we don’t have an Alt key….

  • Antonio_power

    hola sabes algo? esque tengo un iphone4 de vodafone con la 04.12.01 y soy movistar y nose que acer dime algo porfa,

  • Rollno P

    I upgraded from 5.0.1 with baseband 4.11.08 to 5.1 but it dint change the sti shows 4.11.08

  • haydee

    i tried it many times but i end up to error 1601 🙁

    what will i do…pls. help 🙁

  • Big

    This situation 04.11.08 block is bad for Apple, the unlock usually maintains the client on the apple product. Once you loose a client, you loose future sales also. Without the unlock the phone is useless. Its been such a long wait for the unlock that people are starting to move to the Galaxy phone. Apple is starting to lose some business, and I will soon be one of those saying too bad guys, and I will never ever buy a apple phone again.

  • AZ

    can I get your shsh files? 

  • Asianboy2030

    lucky you, if u on baseband 4.12.0… then u will have more headache for that… 4.11.08 is what we considering for now.. more chance to unlock the iphone.. but if u got 4.12.0… then u may or may not able to unlock the phone.. they might able to unlock the phone but might take up to several months.. so stay tune as what u got right there on ur baseband 4.11.08…dont go to 4.12.0… 

  • erik.lda

    I try to do this but I’m still having the firmware 04.12.01 🙁

  • LKH66

    I don’t think that this solution should be working as my experience of iphones, only 3g and 3gs BB can be downgraded. Don’t trust any of these website regarding downgrades of your iphone 4 BB, unless they provide a video to prove it.

    The only thing can be downgraded is your IOS firmware version, not BASEBAND ! Without SHSH backups, you won’t be able to downgrade your firmware neither !

  • Canary Skies

    This garbage, all these sites are baiting traffic. DON’T FOLLOW ANY of the “tutorials” you see here. It’s all keyword-ridden garbage designed to attract searches. If the first thing you see is half a page of ads, hit the back button.

    There has never been a way to downgrade the baseband on a 4. You are going to waste your time and waste it even more once you get stuck in a recovery loop.

    If you need legitimate info you will find it on the Dev Team Blog or iClarified.