Unlocking Japanese iPhone 4 (4.2.1)

Discussion in 'Jailbreaks and iOS Hacks' started by sekaijin, Jan 27, 2011.

  1. sekaijin macrumors newbie

    Jan 27, 2011
    Hello all, long time reader first time poster here.

    I have just been sent back to the US from Japan, and only 2 months after having purchased a shiny new iPhone 4 in Japan.

    I am now trying to get the phone to work in the US, but I have been unable to figure out what to do and some stores I have visited in NYC have also been unable to provide help.

    The J iPhone is also locked to a provider, which means I need to unlock the phone to use it with a US SIM.

    Details on my phone are as follows:
    iPhone 4
    Firmware 4.2.1
    Baseband 03.10.01

    Can anyone tell me if this phone can be downgraded or otherwise jailbroken/unlocked?
  2. winterny macrumors 6502

    Jul 5, 2010
    Tethered Jailbreak: yes [you will need to have a computer to boot up your iPhone]
    Untethered Jailbreak: no
    Unlock: no

    In the future new hacks may be released that improve things.
  3. oakie macrumors 6502


    Oct 16, 2008
    contact softbank and see if they'll be willing to unlock it for you considering your move back to the US. i had no problems with them doing that for me, but i did it before i left japan when i went in to settle up the contract in full.
  4. labman macrumors 604


    Jun 9, 2009
    Mich near Detroit
    either see if you can get them to unlock it in Japan, or sell it then buy one when you back to the US. less headaches in the long run. ;)
  5. sekaijin thread starter macrumors newbie

    Jan 27, 2011
    Unfortunately I did not have Softbank unlock the phone when I cancelled my contract. I asked the person at the counter to do so but was told that was impossible...

    I just tried a tethered JB with redsn0w, and an unlock with ultrasn0w. It appears to have worked properly, but I suppose the jury is out until I can get a SIM card from AT&T or T-mobile and test it.

    I figure that I may as well post as this may help others in similar situations.
  6. CZK macrumors 6502a

    Oct 25, 2010
    Ahhhh the famous japanese 03.10.01 baseband ... You should have said it before!!!!!!

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