Before you go any further, make sure to READ EVERY SINGLE WORD OF THIS TUTORIAL. If you think you’re too cool for school, then go directly to the instructions but please, do not complain if you mess up your iPhone during the process, which is very unlikely to happen anyways…
First things first. In order to be able for you to use Yellow Sn0w to unlock your iPhone 3G, you have to be on a jailbroken iPhone that runs the latest firmware 2.2 with the latest baseband 02.28.00. To find out what firmware you’re on, go to Settings > General > About and look for “Modem Firmware”. It should say 02.28.00.
If you have not jailbroken your iPhone yet, you have to now in order to unlock. To jailbreak your iPhone, follow the QuickPwn 2.2 guide that I wrote a few weeks ago.
If you have already jailbroken your iPhone using PwnageTool to preserve your baseband, sorry but you have to restore and rejailbreak again in order to have the latest 02.28.00 baseband.
If you have updated to the latest firmware 2.2 with its latest 02.28.00 baseband, then you’re good to go.
So from now on, I assume that you are on a clean firmware 2.2 with firmware 02.28.00 and that your iPhone is jailbroken.
1. Go to Cydia and install this new source: http://apt9.yellowsn0w.com/ (note that snow is spelled with a zero, not an “o”). To install a new source in Cydia, go to Manage > Sources > Edit > Add, then type in the source http://apt9.yellowsn0w.com/ and tap “Add Source”.
2. Once the source has been added, tap “Return To Cydia”, then tap “Done”.
3. Now tap “apt9.yellowsn0w.com from the list of sources “Entered By Users”.
4. Select Yellow Sn0w, then tap install nad confirm.
5. Once the installation had been successfully completed, return to Cydia.
6. Hard reset your iPhone. To do this, hold the home and power buttons simultaneously for a few seconds until the phone shuts off by itself (ignore the “slide to power off” message)
7. Insert whatever SIM card you want! Wait a few seconds and you should be good.
See, that wasn’t too hard at all. Users that are already familiar with Cydia and sources shouldn’t have any problem at all. But first time jailbreakers might be a little lost, which is why I detailed this tutorial a lot.
1) If you are on tmobile USA you should disable 3G in Settings or sbsettings.
2) YellowSn0w does not work with a SIM PIN. You must disable your SIM card pin lock.