These are the instructions on how to restore or update iPhone 4 on iOS 4.2.1 by preserving the baseband to 01.59.00 using Custom Firmware. Those of you who have already upgraded to 4.1 & 4.2.1 and are on their respective Modem Firmware (02.10.04, 03.10.01) this is strictly NOT for you. wait for the unlock to come.

Step 1:

Download the following files :

Redsn0w 0.9.6b5 OR 0.9.6b6

Stock/Original iOS 4.2.1 Firmware (iPhone 4)

Step 2:
Connect your phone with your computer and switch it off.

Step 3:
Open Redsn0w and browse original 4.2.1 firmware.

Step 4:
if your phone has new bootrom version then select Yes and click on the next button.

Step 5:
Select “Just Enter Pwned DFU Mode Right Now”

Step 6:
click on the next button and follow the on-screen instructions to put your device in DFU mode.

Step 7:
open iTunes. on Summary tab, hold shift key on your keyboard and click on the Restore button. A dialog box will appear , asking you to select .ipsw firmware. select custom 4.2.1 firmware and click Open.

Step 8:
wait for 5-10 minutes for phone to restore.

Step 9:
Disconnect your phone once the restore is complete and connect it again and launch Redsn0w.

Step 10:
Browse original firmware on Redsn0w & select “Yes” if your phone is a new bootrom model and click on next.

Step 11:
Select only “Install Cydia” as option and click on the next button.

Step 12:
follow the instructions and put your iPhone in DFU mode.

Step 13:
if your phone stucks, re-run Redsn0w and select only “just boot tether right now” option and click on next button.

Step 14:
Open Cydia and add to install Ultrasn0w package so that you could unlock your phone.

You now have a fully jailbroken & unlocked iOS 4.2.1 on iPhone 4 with 01.59.00 baseband.

Related posts:

  1. How To Update Your iPhone 3GS To 4.2.1 While Preserving The Baseband as 05.13.04
  2. How to Jailbreak Using a Custom Restore IPSW and RedSn0w (Windows)[4.2.1]
  3. How to Jailbreak Using a Custom Restore IPSW and RedSn0w (Windows)
  4. Fix 1604 Error During iPhone 3.1.3 IPSW Custom Restore
  5. How To Update iPhone 4 To iOS 4.1 Without Updating the Baseband/Modem Firmware

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