Back in 2010, iPhone Dev team had released a solution that allowed users to unlock their iPhone 3GS by upgrading the baseband to 06.15.00. Unfortunately, the solution caused GPS issues and it was also not possible to downgrade the baseband.
With Redsn0w 0.9.14b1 or later, iPhone 3GS users will finally be able to downgrade the baseband from 06:15:00 to 05:13:04. This will solve the GPS issues and also give these iPhone 3GS users the ability to use stock iOS firmware files again.
iPhone Dev team has provided the following details required to downgrade the baseband:
Here are the steps:
- 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.
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.
iPhone 3GS users should also read the following warning before installing 06:15:00 baseband:
For those who are wondering if you can update your 3G or 3GS to 06.15 solely for the purposes of downgrading to 05.13.04, the answer is “yes” for 3G owners, and “maybe” for 3GS owners. The iPad baseband is not compatible with 3GS units manufactured week 34 of 2011 or later. 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! It will brick your radio, preventing both the downgrade from working and normal iPhone software from using it as a phone! Be warned!
Kudos to MuscleNerd for finally figuring out a way to downgrade from 06:15:00 baseband. It shows his unwavering commitment to the jailbreak community.
If your the baseband is still at 06:15:00 after completing the process, just do it again. MuscleNerd says “the downgrade code minimizes risks but false positives are possible”.
A tip from MuscleNerd: Many people who saw “No signal” issues after the downgrade from 06.15 fixed it by re-installing Mobile Substrate and/or Ultrasn0w
If you’ve problems downgrading your iPhone 3GS’ baseband even after trying multiple times, then MuscleNerd has just tweeted that he will release an update next week to fix the issue. Check out this post for more details.