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Tutorial – How to downgrade your device from firmware 4.0.2 to 4.0.1 without ECID backup

Warning. It seems that the tutorial only works for iPhone 3GS…

As you know, it is impossible to jailbreak a device if it is firmware 4.0.2. And if you want to downgrade to 4.0.1, you will not be able to save your ECID on cydia before.

In addition, those who receive their new device find themselves frustrated with having to wait for the release of firmware 4.1.

Here is a tutorial allowing you to downgrade from firmware 4.0.2 to firmware 4.0.1 without saving your ECID!


  • Have the firmware 4.0.1 of your device (see here)
  • A device in 4.0.2

downgrade dario Tutorial How to downgrade your device from firmware 4.0.2 to 4.0.1 without ECID backup

Step 1

Rename the extension “.ipsw” to “.zip” of the previously downloaded firmware.

2nd step

Look for a file named ” buildmanifest.plist » and open it with appropriate software (on Mac software is installed by default, you just have to double click on the plist).

Look for this line: “8a306” and replace this with “8A400”. Do the same for a file named “restore.plist” in the firmware.

Stage 3

Download the firmware 4.0.2 of your device and unzip it as in step 1. BUT ESPECIALLY DO NOT OPEN IT!

Step 4

Then drag ALL the contents of firmware 4.0.1 (modified in step 2) to firmware 4.0.2 (unzipped in step 3).

Step 5

Then, inside the “new” firmware 4.0.2, you should find DMG files. Delete all those that end with “002” and leave only those that end with “001”.

Step 6

Then close the folder and add an extension to the firmware folder “.ipsw”.

Step 7

So you can restore!

To do this, launch iTunes and plug in your device.

Click in the left column on the name of your device. You should see a restore button:

Hold down the “alt” key and click on the button [restaurer] in iTunes

  • If you are on Windows

Hold down the “ctrl” key and click the button [restaurer] in iTunes.

Then select the .ipsw created in step 6 and that’s it;)

If the restoration does not work, here is a solution:

Just modify the host file on your computer:

Go to the directory C: Windows System32 drivers etc hosts

Go to the / etc / hosts directory

Open the file and add the following line at the end (by skipping a line):


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