Yesterday night I finally got my mind set to upgrade my iphone 3g to ios version 4.2.1. They say its a lot faster than 4.0.1 which I was using.
I know there are many guides out there, I tried following them, but I ran into a lot of trouble, no guide (that I found) was complete, So I decided to make my own.
Before you start, please back up your iphone by right clicking it and selecting backup from the left side menu in iTunes. Also please know that this process is Dangerous. and can lead to loss of data, and – or damage to your iphone. Do this at your own risk .
1. Download the following files:
– the original IOS 4.2.1 http://www.filefactory.com/file/cd51494/n/iPhone1,2_4.2.1_8C148_Restore.ipsw
– Sn0wBreeze 2.2.1 http://www.filefactory.com/file/cd51574/n/sn0wbreeze-v2.2.1.zip
-iREB r4 http://www.filefactory.com/file/cefa17a/n/iREB-r4_2.zip
– Itunes (10 or higher) if you dont already have it
Make sure you have internet Wifi if you will be unlocking
Before we start I will give you an Idea about what we are going to Do.
I assume that you are running IOS 4.1 or lower, and that you have never upgraded your phone to 4.2.1. If this is the case, you are likely to still have the old baseband, which is a good thing, because it can be unlocked easily. in this guide we will preserve your baseband and only upgrade the rest of the IOS (SOME OTHER GUIDES ASK YOU TO UPGRADE USING ITUNES TO 4.2.1 AND THEN JAILBREAK, DONT DO THAT) if you do that you will be upgrading your baseband to a new version, that is only unlockable by replacing it with the ipad baseband. What you need to understand is that this process in irreversible, and may prevent you from upgrading to newer IOSs in the future.
We will take the stock IOS, jailbreak it with with snowbreeze, then get the phone in a special DFU mode using iREB, then use itunes to upload the modified IOS.
OK lets start.
1. Open snowbreeze and drag / drop the iPhone1,2_4.2.1_8C148_Restore.ipsw over it. hit the blue arrow
2. select “Simple” (don’t worry it will also preserve your baseband similar to the first option but it will also jailbreak the ios).
3. IF your will unlock your phone, select yes on the next message.
4. let sn0wbreeze do it’s magic. Then (CHECK THE SIZE OF THE GENERATED IPSW file) in my case snowbreeze made a mistake generating the file, it was around 30mb in size. Itunes will try to flash the corrupted IOS wich can lead to problems. MAKE SURE THE IOS IS LARGER THAN 300 MB
5. Snowbreeze will now help you get your phone into DFU mode, a state required to be able to flash a custom IPSW using itunes. Follow the instructions on screen.
If the program gets stuck during the process, don’t panic, it’s probably because of windows update trying to find a driver for the DFU mode iphone online, make sure to prevent windows from looking up drivers online.
IF YOU REALLY HAVE TO SHUTDOWN your phone because the software got stuck, do it by holding the home and power buttons together until the phone is off (around 10 secs)
If you got it right, your screen will turn GREEN open itunes, it will ask you to restore your iphone, HOLD SHIFT and click the restore button. browse and find the snowbreeze IPSW let itunes flash it.
In my case this didnt work, I got error 21 , cannot restore your iphone. well this is because I’m as lucky as Kenny from southpark, if you are too. dont panic. close itunes, shut down your phone by holding home and power and open iREB.
Select iphone 3g and follow the instructions to set your phone in an alternative DFU mode, in this one the screen is black, not green. once done open itunes and shift-restore the snowbreeze ipsw,you may have to try a couple of times if you get error 1600 you can try to close/open itunes, or unplug-plug your phone while itunes is open.
that’s about it, your phone should now be restored to 4.2.1, once done, go to Cydia (which is already there) and perform a complete update (you will have to be on Wifi to do this) . once done, lookup ultrasn0w in cydia and install it, after the install is complete it will ask you to reboot. Do so.
Now you should have a working jailbroken unlocked iphone 3g on 4.2.1,
you may restore your itunes backup now. Note: if you have installous apps in your back up, you will have to install installous from cydia before restoring the backup. otherwise it will fail