Unable to downgrade 3G from 4.0.1 to 3.1.2

[str0ppy]

I want to downgrade from 4.0.1 to 3.1.2.

I put the phone in DFU mode - Turn off, hold lock and home button for 10 seconds, then home button on its own.

Device shows in iTunes 9.2 as being in recovery mode.

Shift restore in iTunes, locate and 3.1.2 IPSW phone then flashes white for a second before the Apple logo appears. The phone then eventually boots without restoring.

I get error 1601 and don't even get the attach to iTunes screen (which I think I'm supposed to get?)

I am using Windows 7 Ultimate.

I really can't think what I am doing wrong here. Please help as I really want to get back to 3.1.2 as load of my apps are crashing and most of my JB apps have been rendered useless.

Thanks.

 

[thelatinist]

Is your phone's screen completely black when it is recognized by iTunes in recovery mode? If not, then you are not in DFU mode. Follow this tutorial.

 

[str0ppy]

Is your phone's screen completely black when it is recognized by iTunes in recovery mode? If not, then you are not in DFU mode. Follow this tutorial.

It's definitely in DFU mode, the screen is totally black. When I point it at the IPSW the screen flashes white, like it does if you jailbreak it with redsn0w, then the apple logo appears just as it would rebooting. There's no loading bar like you would get with a normal restore, it just reboots.

 

[thelatinist]

I would try another computer.

 

[str0ppy]

I would try another computer.

I haven't got another computer.

 

[str0ppy]

Ok, fixed it. Took ownership of the IPSW and put it in the root. Not sure which of those made any difference but it's now restoring.

 

[benflick]

Ok, fixed it. Took ownership of the IPSW and put it in the root. Not sure which of those made any difference but it's now restoring.

You *may* not be out of the ballpark yet. If the phone successfully restored to 3.1.2, then you're golden. The phone might error out during the end of the restore process. Then you can kick the phone out of recovery if this happens. Only if something goes wrong, if not, ignore this post.

 

[str0ppy]

You *may* not be out of the ballpark yet. If the phone successfully restored to 3.1.2, then you're golden. The phone might error out during the end of the restore process. Then you can kick the phone out of recovery if this happens. Only if something goes wrong, if not, ignore this post.

Yep got a 1015 but kicked it out of recovery with Recboot.

Just to try and get a better understanding I restored from the 3.1.2 IPSW to see if it would do it without the error. Still got a 1015 so I guess that even though I wasn't downgrading, something in iTunes still knew that I had previously been on a more recent version and was trying to stop me staying on the earlier version.

Does that sound right?

 

[brunetmj]

To the best of my knowledge apple does allow you to downgrade. Once you upgrade to 4.0 for example you can't go back to 3.3.
Check that error code with apple

 

[thelatinist]

Just to try and get a better understanding I restored from the 3.1.2 IPSW to see if it would do it without the error. Still got a 1015 so I guess that even though I wasn't downgrading, something in iTunes still knew that I had previously been on a more recent version and was trying to stop me staying on the earlier version.

Does that sound right?

The 1015 error is caused by the phone's inability to accept the 05.11.07 baseband 'upgrade' included in the 3.1.2 firmware (since you already have the 05.13.04 baseband). Fortunately, that is the last step in the restore process; unfortunately, the phone refuses to reset the boot flag, and will force you back into recovery mode. That's where RecBoot comes in.

To the best of my knowledge apple does allow you to downgrade. Once you upgrade to 4.0 for example you can't go back to 3.3.

It is possible to downgrade in DFU mode. The process will error out and leave you in recovery mode, but it is possible to reset the boot flag using RecBoot, TinyUmbrella, or iRecovery.