Downgrade iPhone 3GS, 3G 6.15.00 to 05.13.04 with Redsn0w 0.9.14b1 to fix GPS issues, Dev-team Released Redsn0w 0.9.14b1 that supports 6.15.00 downgrade feature for iPhone 3GS and iPhone 3G. Now you can Download Redsn0w 0.9.14b1.
The new feature will bring two new major features for iPhone 3GS and Phone 3G devices, as downgrading from 6.15.00 to 5.13.04 will fix the famous GPS issue and unlocking your devices using ultrasn0w.
Downgrade iPhone 3GS, 3G 6.15.00 to 05.13.04 with Redsn0w:
Step 1: Connect your iPhone 3GS / 3G to your PC via USB cable.
Step 2: Launch Redsn0w 0.9.14b1, the click on Extras > Select IPSW button then point Redsn0w to the 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).
Step 4: Go back, and click “Jailbreak” button, Enable the “Downgrade from iPad baseband” checkbox, disable Cydia if you already have it installed, and click Next then follow the DFU instructions.
Step 5: After the ramdisk gets launched and you see the running Pwnapple, you’ll eventually get to the “Flashing Baseband” step. THIS STEP TAKES A VERY LONG TIME to complete and there won’t be any feedback while its running. Please just let it be for the next 3-8 minutes! When the ramdisk has done its job it will reboot the phone on its own.
Now, you should have 5.13.04 baseband, so who haven’t installed ultrasn0w, go to Cydia and search for ultrasn0w and install it to unlock your iDevice
Note: If you still see 06.15 after the full process, just try again (the downgrade code minimizes risks but false positives are possible)