This jailbreak is compatible with iPhone 4 baseband/ modem firmware 01.59.00 and iPhone 3Gs baseband/ modem firmware 04.26.08, 05.11.07, 05.12.01, 05.13.04 and 06.15.00. See your modem firmware before doing this untethered jailbreak.
Step by step :
2. Save your .shsh in cydia
3. Download redsn0w from here
4. Open it and select Extras
5. Select custom ipsw
6. And open the .ipsw which is downloaded before in your computer
7. It will make NO_BB_iPhone,1_5.1.1_9B206_Restore.ipsw
8. Now select pwned DFU mode
9. Here has some step for DFU mode
10. After managing DFU / black mode, your computer recognize the iPhone
11. Now open iTunes and select (shift button + restore).
12. Now select NO_BB_iPhone,1_5.1.1_9B206_Restore.ipsw
13. Then iTunes manage to install the ipsw in your iPhone.
14. Now your iPhone will be start in a factory mode.
15. Open redsn0w and select jailbreak
16. Again go to DFU mode and select next, it will work itself in your iPhone
17. Now your phone completely restored by no baseband
18. Open Cydia from your iPhone and refresh
19. Then search ultrasn0w version 1.2.7 and install
20. After installing it ask to restart.
21. After restarting, again open Cydia
22. search rocy Racoon for ios 5.1.1 and install or search Corona 5.0.1 untether and install
23. Now your iPhone is untethered jailbreak.
**You need internet and WiFi connection for this jailbreak