How to Unlock iPhone 3GS on iOS 4.2.1 (Baseband 05.15.04) and Update to iOS 6
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slom • January 2, 2013 at 3:16am
I have a locked iPhone 3GS running iOS 4.2.1 with baseband 05.15.04 and no valid SIM card. I want to upgrade to iOS 6 and unlock the device using the iPad baseband downgrade method with Redsn0w 0.9.15b3. What are the correct steps to achieve an untethered unlock on the latest supported firmware?
Answers
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iClarified • January 12, 2026 at 4:43am
To unlock an iPhone 3GS on baseband 05.15.04 and move to iOS 6, you will need to use Redsn0w to update your baseband to the iPad version (06.15.00) and then immediately downgrade it to 05.13.04, which is compatible with the ultrasn0w unlock.
First, download Redsn0w 0.9.15b3 and the iOS 6.0 IPSW file for the iPhone 3GS. Even if you are targeting iOS 6.1.6, Redsn0w often requires the 6.0 firmware for identification. Connect your iPhone to your computer and put it into DFU mode.
Open Redsn0w, click Extras, then Select IPSW and point it to the iOS 6.0 firmware. Go back to the main screen and click Jailbreak. Select the Install iPad baseband option. Once that process completes, repeat the jailbreak process in Redsn0w, but this time uncheck Install iPad baseband and select Downgrade from iPad baseband. This will bring your baseband to 05.13.04.
After the baseband is downgraded, you can restore your device to iOS 6.1.6 via iTunes. Since you do not have a valid SIM, you may need to jailbreak again to hacktivate the device. Once the device is on iOS 6.1.6 and jailbroken, open Cydia and install ultrasn0w to unlock the carrier. Note that if you have a newer 3GS manufactured after late 2011 (week 34), updating to the iPad baseband may damage your radio chip, so verify your manufacture date via the serial number before proceeding.
First, download Redsn0w 0.9.15b3 and the iOS 6.0 IPSW file for the iPhone 3GS. Even if you are targeting iOS 6.1.6, Redsn0w often requires the 6.0 firmware for identification. Connect your iPhone to your computer and put it into DFU mode.
Open Redsn0w, click Extras, then Select IPSW and point it to the iOS 6.0 firmware. Go back to the main screen and click Jailbreak. Select the Install iPad baseband option. Once that process completes, repeat the jailbreak process in Redsn0w, but this time uncheck Install iPad baseband and select Downgrade from iPad baseband. This will bring your baseband to 05.13.04.
After the baseband is downgraded, you can restore your device to iOS 6.1.6 via iTunes. Since you do not have a valid SIM, you may need to jailbreak again to hacktivate the device. Once the device is on iOS 6.1.6 and jailbroken, open Cydia and install ultrasn0w to unlock the carrier. Note that if you have a newer 3GS manufactured after late 2011 (week 34), updating to the iPad baseband may damage your radio chip, so verify your manufacture date via the serial number before proceeding.