Let me clear this upfront. The following instructions will only help downgrade iPhone 3G which is currently on iPhone OS 3.1.3 with 05.12.01 baseband and older bootloader 05.08. This wont work with iPhone 3GS.
I have got loads of emails and queries via comments on the posts here and here where many of you have been asking on how to fix 1604, 1603, 1602, 1601, 1600 error in iTunes during firmware restore. This error is occurred when you are trying to restore your jailbroken custom iPhone 3.1.3 .ipsw file which you cooked using either PwnageTool or sn0wbreeze.
PwnageTool 3.1.5 for creating iPhone 3.1.3 custom ipsw files is now LIVE! The infamous iPhone Dev-Team has updated their PwnageTool for Mac to make it compatible with the new iPhone 3.1.3 firmware. This latest version of PwnageTool can jailbreak the original iPhone (Edge/2G), iPhone 3G, iPhone 3GS(older bootrom only with baseband 04.26.08) and iPod touch (1G and 2G non-MC model; 2G should also be pre-jailbroken) running on iPhone firmware 3.1.3. The custom .ipsw firmware files created with PwnageTool can update iPhone to firmware 3.1.3 without updating its baseband so that it can be unlocked to run on any carrier SIM. If you previously relied on blacksn0w unlock for iPhone 3GS, then this is NOT for you. iPod touch 3G is also currently not supported.
The iPhone Dev-Team has just confirmed (sort of.) that they are working on a new version of PwnageTool which will enable iPhone 3G and iPhone 3GS users to jailbreak iPhone 3.1.3 firmware without having to update their baseband. For those of you who don't know, PwnageTool, like Sn0wbreeze is an iPhone jailbreaking tool which creates custom .ipsw files without the upgraded baseband.
Sn0wbreeze 3.1.3 is now available for download which can jailbreak iPhone 2G, 3G and iPhone 3GS (old bootrom only) on iPhone OS 3.1.3. We have already published a detailed guide on how to jailbreak using Sn0wbreeze and unlock using ultrasn0w. Ultrasn0w unlock is for iPhones with baseband 04.26.08 baseband. If you are on 05.11.07 baseband, then you may use Geohot’s blacksn0w unlock which was released last year with blackra1n.
Sn0wbreeze 3.1.3 has been released which can jailbreak iPhone 2G, 3G and iPhone 3GS on the latest iPhone 3.1.3 firmware. One thing which is to be noted here is that it will work with iPhone 3GS only if it has the older bootrom (non-MC model). iPhone 3GS users who have upgraded to the stock 3.1.3 are still out of luck.
This is a guide geared towards iPhone users with Mac OS X. The steps are exactly same as they are on a Windows system. You can find the Windows version of the guide here.
The iPhone Dev-Team has just released redsn0w 0.9.4 to jailbreak and unlock iPhone 2G, iPhone 3G (No unlock for 3G), iPod touch 1G and iPod touch 2G (older Non-MC models only). Do not update to iPhone 3.1.3 firmware yet if you want to preserve your unlock for iPhone 3GS, iPhone 3G, iPod touch 2G (new models) and iPod touch 3G. This is because the new iPhone 3.1.3 firmware updates baseband to 05.12.01 on iPhone 3GS and iPhone 3G which makes it impossible to jailbreak and unlock iPhone 3GS and 3G.
The newly released iPhone 3.1.3 firmware for iPhone and iPod touch updates baseband to 05.12.01 on iPhone 3GS and iPhone 3G, hence making it impossible for these two devices to get unlocked using blackra1n with blacksn0w. Fortunately for iPhone 2G (the first generation iPhone with EDGE) users, the baseband remains intact. The iPhone DevTeam has just confirmed that their newly released jailbreaking tool called redsn0w 0.9.3 can be used to jailbreak and unlock iPhone 2G on firmware 3.1.3, provided that you have jailbroken it previously at least once.
Apple today has released the new iPhone 3.1.3 firmware for iPhone and iPod touch. This release is just a minor upgrade over the last firmware and it mostly brings stability and bug fixes for iPhone 3GS, 3G, 2G and iPod touch. Interestingly, this (version 3.1.3) isn't the same version which runs on the newly released Apple iPad (OS 3.2).
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