downgrade baseband 6.15 redsnow 0.9.14b1 for iPhone 3G and iPhone 3GS

As musclenerd promised that he would release a downgrade method for those iPhone 3GS and iPhone 3G users, well the time is here now. iPhone Dev Team has released Redsnow 0.9.14b1 for iPhone 3G and iPhone 3GS to downgrade baseband 6.15.00 to a lower one so you can make your GPS work. So folks go ahead and downgrade baseband 6.15.00 by downloading redsnow 0.9.14b1 for iPhone 3G and iPhone 3GS.  

Download Redsnow 0.9.14b1 To Downgrade Baseband.

Steps To Downgrade Baseband 6.15.00

• Use the “Extras->Select IPSW” button in redsn0w to tell it which firmware version you have installed (new-bootrom 3GS users can usually skip this step but it doesn’t hurt for them to do it too).

• Do a controlled shutdown of your iPhone (“slide to power off”).  This step is very important to avoid mount problems when the ramdisk is running!

• Go back to the first screen and click “Jailbreak”.  Enable the “Downgrade from iPad baseband” checkbox, disable Cydia if you already have it installed, and click Next to proceed through the normal DFU ramdisk steps.

Download Redsnow 0.9.14b1 Mac

Download Redsnow 0.9.14b1 Windows

Download redsnow 0.9.14b1 from the links above and follow the steps to downgrade your baseband 6.15.00 to 5.13.04. This will allow your GPS to work and you can still unlock iPhone using Ultrasnow.

Problems While Downgrading Baseband

• If you complete the entire process and you are still on baseband 6.15.00, try it again it should work in the next round.

• If the baseband has been downgraded but no GPS or “no service”, try redsnow’s “Deactivate” option if you do not rely on using Ultrasnow anymore.

• If you are seeing “Invalid SIM”, simply unlock it using Ultrasnow 

• If you have an iPhone3GS and if digits 3-5 of its Serial Number are 134 or later (xx134…), then you should NOT try to install the 06.15 baseband on your 3GS! This will brick your iPhone making it useless.

Any more questions hit the comment section below. source: HERE