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Fourth generation iPhone. Repair is straightforward, but the front glass and LCD must be replaced as a unit. GSM / 8, 16, or 32 GB capacity / Model A1332 / Black and White.

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iPhone stuck in a boot-loop + Error code: 21 upon iTunes restore?

Hello, recently bought a few iPhones as I am looking into making an application I have developed cross-platform.

This particular iPhone did come working (booted) with a cracked screen, I had purchased another screen and had fixed the iPhone but unfortunately had a pass code, I didn't see this as a problem so I installed iTunes and attempted to completely reset and restore the iPhone; I did remember the iPhone only reaching around 40% on the 'loading' bar on the phone before iTunes presented me with an error code.

I cannot remember what this error code was, but it escalated until I finally ended up getting the error code: 21, and it's pretty much stuck with 21 upon every restore attempt.

I had opened up the phone and noticed the battery connector had now became loose and has now detached from the logic board, upon doing my own research on Error code: 21 I had presumed this battery connector was the issue. (Or is it something else)

So my question is, is there a possible way to restore this iPhone 4 WITHOUT iTunes (as my plans was to purchase a charge case to keep it alive when making it portable if needed). Or will I simply have to re-solder the Connector on myself? At this very moment the phone powers on when the charger is connected HOWEVER, presents the Apple logo for around 10 seconds and re-boots (bootloop) which has lead me to think the OS has corrupted upon trying to restore the very first time.

Thank you for any help given, it's greatly appreciated!


tl;dr - Battery connector is broke, phone is in a bootloop, will I be able to restore this iPhone without iTunes and cure it from the bootloop without having to physically repair the connector?

Extra Information

*iPhone 4 - 16GB

*I have no history whether it has been jail broken or not. (Most likely has).

If anymore information is needed I will supply, thank you. :)

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1 Answer

Chosen Solution

Yes error 21 means there is a problem with the battery, in this case the connector is ripped of the logicboard.

There is unfortunaly no way to boot without the battery or battery connector.

The bootloop you're in is because an iPhone cannot boot from the charger only, and can also not restored without a battery

After you resoldered the connector to the logicboard and it is soldered good enough, then your iPhone will normally boot from its battery and then you will be able to restore it.

Watch out if your solderpads are still intact!

If you need any more help you can always ask.

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Beckibox BX-101i


Same Problum here, My iphone has no issue with bettry still getting

Error 21 ,

some times 4014

some times 3194

Please help


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