In this tutorial we are going to guide you how to jailbreak your iPhone 3GS (3.1.2 firmware) by using the RedSn0w tool in your mac computer. Before following the steps below, make sure you have latest version of itunes.
1. Create a new folder on the desktop with the name Pwnage. Download and place redsn0w-mac_0.9.4.zip and iOS 3.1.2 for iPhone 3GS in it. Extract redsn0w-mac_0.9.4.zip in the same folder (you will get redsn0w.app).
2. Connect your iPhone to the computer and launch iTunes.
3. In iTunes, By pressing the shift button from your keyboard click on the restore button. You will asked to locate the firmware, just locate firmware(iOS) in the Pwnage folder.
4. Once restoring process is done, launch redsn0w.app from the Pwnage folder.
5. Once RedSn0w opens, click on the browse button and locate the iOS you have downloaded in the Pwnage folder.
6. Now, RedSn0w will ask you whether your iPhone is a newer model of iPhone 3GS? This is because newer model of iPhone 3GS have fixed bootrom which requires you to connect your iPhone to the computer whenever you made a reboot.
If you are not sure that your iPhone is of new model then you can determine this from the serial number in your iPhone Settings > General > About.
Serial number, beginning with 88926 is old model of iPhone 3GS.
If you think your iPhone 3GS has a fixed bootrom then press on Yes button. Otherwise press on No button to continue.
7. Now, RedSn0w will validate the iOS you have downloaded. Once it has detected your downloaded iOS is valid, click on next button to continue.
8. Now, select Install Cydia, and click on next button to continue.
9. Now, RedSn0w will ask you to confirm that your iPhone is connected to the computer. Make sure iPhone is connected. RedSn0w will guide you to put your iPhone in recovery mode. Follow the instructions given by RedSn0w.
10. Once your iPhone successfully entered into DFU mode, RedSn0w will automatically detect it and start performing operations.
11. While performing the operation, your iPhone will reboot then redSn0w will begin uploading new RAM Disk.
12. Once the uploading process in your iPhone is completed, you will be notified that redSn0w is done. Now, click on the Finish button.
Your iPhone will take approximately 5 minutes to complete Jailbreaking process in the phone. Once Jailbreaking process is done, you will see iPhone springboard with cydia installed.