The “Different SIM Detected” problem occurs mainly in those iPhones that were jailbroken using the easiest jailbreaking method – JailbreakME. Apple has managed to cover the exploit  but now its possible yet again to activate your iPhone for a different network and get rid of the “Different SIM Detected” problem, as shown in the screenshot below:

Here’s a step-by-step guide on how you can fix the Different SIM Detected problem on the iPhone which is jailbroken using JailbreakME.

• Restore your iPhone to the original iOS 4.0.1 firmware using iTunes.
• Now activate your iPhone using phonebook SIM card. Refer the video below for guidance:
• Jailbreak your iPhone again using JailbreakME.
• Unlock it using tutorials posted here.
• Replace the phonebook SIM card with your SIM. When you will reboot, it would show you the Different SIM Detected error.
• Download i-Funbox for Windows OS.
• Launch i-FunBox and let it detect your iPhone attached to your PC.
• Now go to /private/var/root/Library/. You’ll see several folders there, delete the folder named as “LockDown”.
• Download the patched version of LockDown and copy it on the same location, /private/var/root/Library/.
• Now you are good to go. Simply restart your iPhone and now it should be able to pick a signal.

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