For those who had iphone 3gs 3.1.2 on AT&T network and got stuck trying to jailbreak there iphone 3gs 3.1.3 with baseband 5.12. This will not unlock your phone. NO T-MOBILE. ITS ONLY A JAILBREAK. This is for people on AT&T Network and wants to jailbreak there upgraded iphone 3gs 3.1.3 phone.




MUST HAVE SHSH's ON FILE FOR iPHONE 3gS 3.1.2 on Saurik's server.


OK... I've upgraded my iphone 3gs untethered to 3.1.3 on purpose because I'm on at&t. But I couldn't jailbreak it for some odd reason. So luckily my SHSH's is saved onto Saurik's server and I was able to Jailbreak my iphone 3gS 3.1.3. The SHSH's came in handy. 8-)


My steps were:
1) iphone in DFU MODE

2) Make sure your using itunes 9.03

3) Host File pointed to Saurik's server.

4) SHIFT + ENTER on Restore while iphone 3gs in DFU mode.

5) Locate the file(iPhone2,1_3.1.2_7D11_Restore)

6) Wait for the Downgrade process to finish

7) iPhone 3gs 3.1.2 should be install.

WARNING!!!
You should get an itunes 1600 error and your iphone 3gs should be in recovery mode!! While your iphone 3gs is in recovery mode, your going to restore your iphone 1 MORE TIME while it's in RECOVERY mode. Now go to iTUNES and hold down the SHIFT Key and click on RESTORE and locate file (iPhone2,1_3.1.2_7D11_Restore).

After the process is finish once again. You will get an itunes 1600 error AGAIN!! but that's ok


DON'T WORRY!!
NOW! Locate the application on google for "redsn0w-win_0.9.4"

While your iphone is still in recovery mode run "redsn0w-win_0.9.4" As you should know right now you'll need the iphone 3gs 3.1.2 restore file (iPhone2,1_3.1.2_7D11_Restore). Now run the redsn0w application as a regular jailbreak. Install with Cydia and all that good stuff. redsn0w will ask you if you have a tethered iphone 3gs. Answer correctly!

Once redsn0w done it's job your iphone 3gs will get kick off from recovery mode and should work as normal.... but it won't have any service at all because your baseband was updated... and it did not jailbreak your iphone 3gs. (which sucks for me at first). BUT LUCKILY... there's Sn0wbreeze!!! heh heh


Forget about your iphone 3gs right now and lets focus on the application sn0wbreeze. sn0wbreeze is a iphone custom firmware creator which creates the firmware without updating your baseband and implements cydia within the firmware. In this case your iphone 3gs baseband is already upgraded and service isn't working on 3.1.2. Luckily Sn0wbreeze is a iphone 3.1.3 custom firmware creator, VIOLA! you can upgrade your downgraded iphone 3gs 3.1.2 with the CFW and have a clean jailbreak!! ha ha ha!

STEPS!

1) Create custom firmware 3.1.3 for iphone 3gs using Sn0wbreeze
-You'll need (iPhone2,1_3.1.3_7E18_Restore)
(Search on Google on how to use Sn0wbreeze)

2) Your created custom firmware should be made.(sn0wbreeze_iPhone 3GS)

3) PUT YOUR iPhone in recovery mode! NOT DFU mode!

4) itunes - hold down Shift key and click on restore. locate your created custom firmware (sn0wbreeze_iPhone 3GS)

5) Your iphone 3gs should Restore with the custom firmware, wait for it to finish... and you should have a jailbroken iphone 3gs with service on baseband 5.12.


and there you go. The steps i took to jailbreak my upgraded iphone 3gs 3.1.3 baseband 5.12!! if you have a tether iphone 3gs. good luck. but you should have a jailbroken iphone 3gs.