After installing iPad BB 06.15.00 on your iPhone 3GS or 3G, you might want to know that how you can downgrade baseband 6.15.00 so you can fix GPS issue with your phone. The BB we mentioned earlier is quite famous for 3GS and 3G users because it’s the only modem firmware which can be installed over baseband 5.16.05. Without installing it, you can’t unlock 5.16.05.
Although, you get your phone unlocked after getting baseband 06.15 but there are few issues related to this modem firmware. After installing it, your Smartphone GPS would stop working and your device looses the capability to use stock iOS. Only custom firmware can be used after that. But, with the introduction of Redsn0w 0.9.14b1, both these problems will be solved because it comes with the ability to downgrade iPhone 3GS on baseband 6.15.00 to 05.13.04. If you’ve a sharp memory then you would remember that 05.13.04 can be unlocked with Ultrasn0w and this BB has no issues at all.
Here’s the tutorial that will guide you that how you can use Redsn0w 0.9.14b1 for downgrading baseband 06.15.00.
iPhone 3GS owners with new Bootrom must not install 6.15 on their phones because it will brick your radio. As a result, it’ll not let you downgrade your device and it’ll also prevent normal iPhone software from using it as a phone and your phone will become unusable.
The devices with new Bootrom came after week 34 of year 2011 which means that iPhone 3GS owners who have Serial Number with digits 3-5 as 134 or later (xx134) should not install iPad baseband 6.15.00.
How To Guide
1. Connect your iPhone 3GS / 3G to the Computer with the USB cable.
2. Run Redsnow software you downloaded earlier and head over to the Extras.
3. Now you’ll be presented with the Menu where there are numerous options. Choose “Select IPSW” option and locate the firmware file you’ve already installed on your device.
4. Now power off your iPhone with “Slide To Power Off” function. This is a very important step. Remember not to miss it because it avoids mount issues while running Ramdisk.
5. Return back to the Main Menu screen and hit the “Jailbreak” button. Check “Downgrade from iPad baseband” option. Don’t check “Install Cydia” option if you already have Cydia on your phone. Hit the “Next” button and get your device into DFU mode by following on-screen instructions.
6. After running Ramdisk, you’ll see “Flashing Baseband” step. This process will take a few minutes. When the process is complete, your iPhone 3GS / 3G will reboot and you’ll see that your device has been downgraded to baseband 5.13.04.
Note 1: If you’re experiencing crashes or no signal issues then you should try re-installing Mobile Substrate and/or ultrasn0w.
Note 2: If you’re still seeing BB 6.15.00, then you should try the above process again.
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