Adapted from my original article How to Jailbreak and Unlock the iPhone 3GS.
Unlocking the iPhone 3GS…impossible they say! Not so. Here’s a very simple walkthrough for the jailbreaking and unlocking process. It’s quite a bit different from unlocking the iPhone 3G, so make sure you follow the instructions carefully. Once you have all the software, you’re about twenty or thirty minutes from having a fully Unlocked iPhone 3GS!
Step 1. Before we unlock the iPhone we have to jailbreak it, and that requires the official Apple IPSW. Rather than trusting a third party for the download, get it straight from Apple by opening iTunes. Plug in your iPhone 3GS and click the “Restore” button. Agree to backup the iPhone and download the restore software. Once the see the download pop up on the left hand side, disconnect your iPhone. We don’t really want to restore, we just want to download that IPSW file.
Step 2. Once the download completes, open up redsn0w (which you can get here) and click the “Browse” button. You need to select the iPhone2,1_3.0_7A1 file. If you downloaded it through iTunes, you can find it in the Library/iTunes/iPhone Software Updates folder under you user account. Click the “OK” button to continue.
Step 3. Click “Next” to patch the kernal. This will begin assembling the custom firmware used to jailbreak the iPhone 3GS. After the loading scree you will be asked which options you’d like to install. Check both Cydia and Icy, and then click “Next”. Redsnow will finish building the firmware.
Step 4. Now that the custom jailbreak firmware is built, redsn0w will prompt you to put your iPhone in DFU mode. TAKE NOTE! The iPhone 3GS has a different process for DFU mode than the old iPhone. Follow the instructions – Disconnect the phone, turn it off, and then plug it back in while holding the home button. Continue to hold the home button until the iTunes logo appears. The program will now begin jailbreaking.
Step 5. After the iPhone is jailbroken, connect to Wi-Fi and open the Icy app. You may need to wait until and tap “Sources”. Wait for it to finish checking the sources. Tap “Edit” in the upper right hand corner and then tap the plus button the upper left hand corner. Tap the Add button and enter http://repo666.ultrasn0w.com in the Source Window. Tap the large “Add” button to finalize the source addition. Tap the refresh button at the top to check the source.
Step 6. While you’re still in the Icy app, tap “Categories” from the bottom options. Scroll down and select “Utilities”. Make sure you select “Utilities” and not “Utility”. At the bottom of the utilities screen you should see ultrasn0w. Tap that and select “Install” from the upper right hand corner. Once the install is complete your iPhone 3GS will be jailbroken. You may need to restart the iPhone.
T-Mobile users will want to disable their 3G in the preferences before they pop their SIM card in. Turning on data roaming may also increase performance.