Results 1 to 7 of 7

Your favorite Apple, iPhone, iPad, iOS, Jailbreak, and Cydia site.


Thread: Downgrade of 3GS to 3.0 fails repeatedly dd with error (20)

  1. #1
    Default Downgrade of 3GS to 3.0 fails repeatedly dd with error (20)
    I have an iPhone 3GS, and I have a sig for 3.0 on file with Cydia. I use AT&T so I don't need the unlock. I had to upgrade to 3.1 but now want to downgrade to 3.0 to get jailbreak back, and I'm having problems. I consistently get the following error immediately after the "verification with Apple" phase of the upgrade:

    The iPhone "iPhone" could not be restored. An unknown error occured (20).

    I've carefully followed Saurik's instructions here: Caching Apple's Signature Server - Jay Freeman (saurik), including setting the hosts file appropriately. I'm using iPhone2,1_3.0_7A341_Restore.ipsw as the IPSW.

    I'm well aware that error code (1015) means you just need to repeat, and that getting two errors like this is expected behavior for phones in my situation. However, repeating this many times still fails, and I couldn't find anoyone else who has talked about an error (20) recently.

    I did find some references to the error message with an error code of (20), but these were relatively old with firmwares in the 1.x or 2.x range. These seemed to refer to an intermittent problem that fixes itself, so I've tried many, many times with the same result. I've also tried it with the ipsw downloaded from different sources, and I've even tried doing the restore using iTunes running on different computers. It always gives the same result, but doing normal upgrade to 3.1 works fine.

    Any ideas? I want jailbreak back!
    Last edited by Dolphin Developer; 2009-10-06 at 06:59 PM.

  2. #2
    Error 20 happens when you try to downgrade from recovery mode you need to put the phone in DFU should be a black screen. with the phone on and plugged in hold home and sleep buttens about 7 secounds (till your computer beeps) then let go of sleep and keep holding home till your computer beeps again also about 7 secounds. You should get a black screen but itunes still sees the phone.

  3. #3
    Just to verify...You did put it into DFU mode, right?

  4. #4

  5. #5
    hehe, ya I am a newb, thanks for pointing out the DFU vs recovery mode... I thought they were the same, lol.

    Rather embarrassing, really, I completely glossed over a very important paragraph in the instructions because I thought I knew that stuff.

    Will try now...
    Last edited by Dolphin Developer; 2009-10-06 at 07:43 PM.

  6. #6
    Quote Originally Posted by Dolphin Developer View Post
    hehe, ya I am a newb, thanks for pointing out the DFU vs recovery mode... I thought they were the same, lol.

    Rather embarrassing, really, I completely glossed over a very important paragraph in the instructions because I thought I knew that stuff.

    Will try now...
    actually the same thing happend to me. the instructions posted here are wrong:

    http://modmyi.com/forums/3g-s-downgr...ecid-shsh.html

    Part 4 - Using iTunes to downgrade

    After checking the server is running, and gs.apple.com resolves to 127.0.0.1 as explained above, open iTunes 9
    Note: 9.0.1 works fine, and I would recommend updating to 9.0.1 if you have not already.

    1) Switch your iPhone off.
    2) Hold down the home button and plug your iPhone up to the USB cable.
    3) When iTunes opens and tells you your phone is in Recovery mode, hold down shift (Windows) option (Mac) then click Restore.
    4) Now browse to the firmware you need to restore.
    5) After selecting it, click Open.

    If you are downloading from 3.1, you need to use this method to restore your phone twice.

    The first time it should fail with "An unknown error occurred (1015)", basically, what has happened is that some of the NAND storage has been slightly reorganized in 3.1, and the 3.0 iBoot can no longer parse it.

    Now, try again, this second restore is also going to fail with "An unknown error occurred (1015)", this is normal behaviour, don't worry. However, this second restore re-formats the NAND fixing the previous problem.

    Note: If this does not work in recovery mode, try again, but using DFU mode instead.
    this should be corrected. ..DFU mode should be used first (and only?)

    this lesson is also posted in my post in the main howto thread

  7. #7
    Default repeated error 20 in DFU mode solved using 3.01 firmware instead of 3.0
    I had registered with Cydia and had edited my etc/host file (on mac) as directed
    repeatedly tried to restore to 3.0 using:
    iPhone2,1_3.0_7A341_Restore.ipsw

    while in dfu mode, near the end of the process, it would jump out of dfu mode into restore mode and then i'd get the error 20.

    i had someone watch me go into dfu mode to verify that i was doing it correctly.
    i tried a different usb cable, tried a pc...

    then i thought, well how about trying to restore to 3.01, so i did a google search for 3.01 firmware for the 3gs and found the file:

    iPhone2,1_3.0.1_7A400_Restore.ipsw

    redid the whole dfu, option restore method with this new 3.01 file and it worked!!!!!!

Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •