Over the years, I bought many iPhones for family and friends from US. Only for the last 2 Years, Apple has been selling unlocked phones. Before that, for most phones, I had to figure out a way to jailbreak and carrier unlock the phone via Ultrasn0w.
For iPhone 3Gs, to carrier unlock your phone, I had to upgrade my phone’s baseband to 6.15.00 (iPad’s baseband) and then using Ultrasn0w I could use the phone with any service provider in India.
However for iPhone 4 with baseband 4.11.08, Ultrasn0w could not do the carrier unlock. Basically there was no way to upgrade/downgrade the baseband. I had given up hope and my daughter was happily using those iPhones as toys. Just then I came across BejingPhoneRepair’s IMEI Unlocking Steps. I was very skeptical that this would work. Paid $15 USD for 1 phone and it worked like a charm. I was able to unlock all my iPhone4’s.
Then I had this iPhone 3Gs, which I had jail broken and upgraded the baseband to 6.15.00. I wanted to upgrade that to iOS 6.0.1. So I thought I might as well use the same IMEI unlock. After I paid and followed the exact same steps I did for iPhone4, I realized there was an issue:
It refused to recognize the SIM card. Then I came across this article from Richard Ker of BeijingiPhoneRepair. This explains that iTunes does not let you activate your iPhone 3Gs with baseband 6.15.00 on iOS 6.
The solution they propose is to downgrade your baseband to 5.13.04 first. To downgrade your baseband you can get the original iPhone 3GS iOS 5.1.1 firmware and then using Redsn0w to flash the baseband. Since I already had iOS 6.0.1 installed on my phone, I kept getting the following error:
AppleBaseband: Could not find mux function error.
Tried downgrading my phone to iOS 5.1.1 using Redsn0w and iTunes, but no luck. Apple does not allow you to downgrade from iOS 6 to iOS 5. You need the SHSH blobs saved for iOS 5.1.1 to downgrade as Apple has stopped signing this firmware. Using Redsn0w I tried searching Cydia’s server to see if SHSH blobs were available. No luck. So I followed the following steps to fix the issue:
- Using Redsn0w (0.9.14b2 or above), I put my phone in DFU mode.
- During the restore process, iTunes verifies with Apple’s server if the device is allowed to install the specific version of firmware. To work around this issue, I appended the following line 188.8.131.52 gs.apple.com to my host file (/etc/hosts) to fool iTunes.
- Then using iTunes, restored iOS 4.1 (8B117) firmware on my phone. I usually download my firmwares from iClarified’s site.
- After Launching redsn0w. Under Extras > Select IPSW and select the original iOS 4.1 (8B117) firmware
- Did a controlled shutdown of my iPhone (“slide to power off”).
- Returned to the first screen and clicked ‘Jailbreak’.
- Checked the ‘Downgrade from iPad baseband’ checkbox and unchecked Cydia. Next.
- Redsn0w started the downgrade process and you finally I saw the ‘Flashing Baseband’ screen on my iPhone with the Pawnapple icon. DO NOT INTERRUPT your iPhone while baseband flashing is in progress. This steps takes a good 5-10 mins.
- When this was done, after rebooting my iPhone, the baseband was downgraded to 5.13.04.
- Then I connected my phone to iTunes once more and upgraded my firmware to iOS 6.0.1.
- Once the upgrade was done, I saw this screen on iTunes.
- Now my phone can connect to the local service provider.