Jailbreak and Unlock iPhone 3.1.3 Firmware With Sn0wbreeze v1.5 and Ultrasn0w
Sn0wbreeze 3.1.3 is updated again to v1.5 with added support for iPod touch 2G older non-MC models. Sn0wbreeze is a jailbreaking tool which works on Windows. You can use Sn0wbreeze 3.1.3 V1.5 to create custom .ipsw files and update your firmware without upgrading the baseband of your iPhone.
You can use Sn0wbreeze 3.1.3 v1.5 to Jailbreak iPhone 3GS (old bootrom, non-MC), iPhone 3G, iPhone 2G, iPod Touch 2G (old bootrom, non-MC) and iPod Touch 1G. If you have a Mac then you can use the PwnageTool 3.1.5 to jailbreak iPhone 2G, 3G, 3GS (older bootrom with baseband 04.26.08). Many 3GS users complained that the Sn0wbreeze send the iPhone into an infinite loop after first reboot, so be away from it.
To jailbreak iPhone 3.1.3 Firmware With Sn0wbreeze v1.5 follow the guide “Jailbreak iPhone on 3.1.3 Firmware With Sn0wbreeze 3.1.3 v1.4“, but use sn0wbreeze v1.5 instead of v1.4.
After jailbreak read the guide on How to unlock iPhone 3GS and 3G on 3.1.3 Firmware Using Ultrasn0w
If you have a Mac Read the below Guides to jailbreak 3.1.3 Firmware.