Instructions for jailbreaking iPhone 3GS on iOS 4.3.1 with PwnageTool for Mac.
How to jailbreak iPhone 3GS with 4.3.1 firmware version with Pwnage Tool on Mac OS X
1. Make a new folder on the desktop of your Mac computer. Download Pwnage tool version 4.3 from here. Also download the iPhone 3GS 4.3.1 firmware from here. You should download the firmware file with Firefox browser as some other browsers like Safari usually rename the file deeming it unusable for restoring.
2. Click twice on the PwnageTool file to extract it and move it to your new desktop folder. Click on the Pwnage tool to fire up the software tool.
Click OK for the copyright warning.
3. Pwnage Tool will offer you some choices, you have to select the “Expert” option.
4. Select your iPhone when prompted. Click on the blue sign to continue with the jailbreak.
5. Pwnage Tool will now offer you to browse to point to the previously downloaded iOS 4.3.1 IPSW file. It will be in your desktop folder or other place where you have saved it. Click on the file to choose it then click ” Open”.
6. Now you will see a number of different options. Please choose the option “General” and again click on the arrow in the lower right side of the screen to proceed to the next step.
Within General settings you will be able to choose the size of the partition. You can choose to activate the iPhone if you need it (this is necessary only if you are using a non official network carrier. If you are on official iPhone carrier do not forget to deselect this option.
7. Now your iPhone is ready to begin with the process. Click on the Build option to choose it and continue by clicking on the blue arrow sign.
8. Pwnage Tool will now ask you where you want to save the custom firmware file. You can save the file into the desktop folder you made previously.
Pwnage Tool will now build your custom IPSW firmware file. Wait for the process to finish. It will take approximately 10 minutes. When prompted for your administrator password type it and press OK to continue.
9. When the custom firmware is made it will ask you to connect your iPhone to your Mac computer. When you connect your iPhone, Pwnage Tool will show you instruction for entering your 3GS iPhone into DFU mode. To enter the DFU mode please press and hold home and Power buton for 10 seconds, follow up by releasing the Power but continue hold on the Home button for 10 seconds more.
When Pwnage Tools recognizes that your iPhone has entered DFU mode it will ask you to start iTunes.
10. While in iTunes hold the function key on your keyboard and choose “Restore”.
11. iTunes will prompt you to browse to the firmware file. Browse to custom firmware file you have previously built with Pwnage Tools. It will be in your desktop folder. Click on the IPSW file and click “Choose”.
12. Your iPhone will now be restored with the custom 4.3.1 iOS firmware. You will need to wait for about 10 minutes or less and when the restore is completed iPhone will reboot and it will be jailbroken and with iOS 4.3.1.
You can now tap on Cydia and enjoy many free and paid tweaks and apps which are available from the Cydia app store.





I have a 3G. Can I use this procedure? By the way, I didn’t see the links
No, ths is for iPhone 3GS on 4.3.1. You need to find instructions for iPhone 3G with your firmware version.