Upgrade iOS3.1.3 to iOS 5 on an unlocked, jailbroken iPhone 3GS?
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devanshi_dns • September 24, 2012 at 7:41pm
I have an iPhone 3GS:
running version: 3.1.3 (7E18)
modem firmware: 05.12.01
this is jailbroken + unlocked (from grey market, not factory)
I want to upgrade it to iOS5 to run the latest apps.
Please let me know what to do.
I have cydia in my phone, is there a straight forward way?
DS
Answers
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iClarified • January 11, 2026 at 8:19pm
Upgrading an unlocked iPhone 3GS from iOS 3.1.3 to iOS 5 requires caution to avoid updating your baseband, which would break your software unlock. Since Apple no longer signs iOS 5, you can only upgrade to that specific version if you have previously saved your SHSH blobs for it. If you do not have these blobs, you will likely be forced to upgrade to the latest supported version for the 3GS, which is iOS 6.1.6. To maintain your unlock during the process, you must use a tool like Redsn0w or PwnageTool to create a custom IPSW (firmware file) that does not include a baseband update. Once the custom firmware is installed, you can jailbreak the device and then install ultrasn0w from Cydia to restore your carrier unlock. Note that the success of the software unlock depends on your specific baseband version remaining at a compatible level, such as 05.12.01 or 05.13.04.