iPhone4 won't restore and shows Error 21

you don't have to replace battery or even take it out just take off back disconnect the battery(one screw) i don't know if you need to or not but i held home button down for 30 seconds to help fully reset the phone then push the silver connector back on and put phone together. now hold down home button and same time plug it into computer and keep holding home button until phone shows to plug in to iTunes so make sure iTunes is already open before plugging in. then do complete restore and you'll be back in business. trust me i tried for two days i thought i had a paper weight.

I have had this problem for the past 2 days and I finally fixed it. It had nothing to do with the system but the the connection between the battery and the phone had gotten messed up. It kept trying to restore but only ended up with error 21.

My solution: I opened the phone, removed the battery, cleaned out the battery connector and reattached the battery. The phone turned back on and showed the low battery sign. I had done this before and it didn't work. Apparently the problem was I hadn't properly connected them. You need to make sure it's locked on tight so when you close your phone slides on easily. I hope this can help someone else. I was ready to buy a new battery and now I don't have to.

i used to have same problem,apple logo apear and desapear, when was connected to a wall charger or to pc.the problem was the battery it doesnt hold charge then the phone cannot load the os or can not be restored cus phone is no charged replacing the battery solve that issue hope this help to you.

I have had this problem and as a trial swapped battery's with an identical iPhone 4 the phone worked fine then, I then put the old battery into the other phone and the error/ unable to boot up occurred so a new battery will resolve error 21 or other similar boot up problems and is a cheap fix £2.50-£3.50 on e-bay.

I faced Error 21 recently and the only way I was able to solve it was by removing the battery and leaving the phone for 2 minutes. I put the battery back, connected the phone to iTunes and the restore worked like a charm.

PS: I am guessing that all the phone needed was a complete hard reset.

[http://Here is ]what Apple suggest " Custom firmware restore fail (PwnageTool since 4.1). You have to put your device into the DFU mode and not into recovery mode. Device won't boot correctly an stuck at the Apple logo after the error. Press and hold power and home button until it reboots.

Error when using Sauriks server for a restore with iOS 5.x in the recovery mode at least on a A5 device. " If you need further help, check on here.

I have a similar problem with my cousins iphone 4 which i offered to look at for her. I have been told that the phone was i great working condition until the phone started to install ios 7 at which point the phone has frozen/crashed, and now wont work at all.

The phone does not show any sign of life while not connected via usb (3 different fully charged batteries have been tested). A Couple of time when pluged into the wall socket the phone has booted up to emergency calls only. When plugged into the computer it boots to the apple logo, and then restarts - sometimes it goes to itunes logo.

Now i have tried several different programs that are supposed to help put the iphone into pwned dfu mode, i have also tried normal dfu mode and restore mode, all of which fail to get past the "Preparing iphone for restore" in itunes, as the phone reboots and goes back to loading either the apple logo and restarting or itunes logo. Then itunes displays error 21. At no point have i seen the phone boot to an Apple Logo with a Loading bar. I have tried on several different computers (win xp/ win 7), different usb cables, and the hosts file never has the 74...** ip's (i have added them to see if it helped then removed them again). Removing the battery for a while then removing also has not worked.

Programs i have tried include:

ireb -windows

Tiny Umbrella

irecovery

sn0wbreeze

redsn0w

SemiRestore

I have been at this for 1/2 weeks now and have searched google and formus high and low and have not found a solution to this specific problem (none that has worked for me anyway)

Thanks in Advance

Steven

Error 20, 21, 23, 26, 28, 29, 34, 36, 37, 40

These errors typically occur when security software interferes with the restore and update process. FollowTroubleshooting security software issues to resolve this issue. In rare cases, these errors may be a hardware issue. If the errors persist on another computer, the device may need service.

Also, check your hosts file to verify that it's not blocking iTunes from communicating with the update server. See iTunes: Advanced iTunes Store troubleshooting—follow steps under the heading Blocked by configuration (Mac OS X / Windows) > Rebuild network information > Mac OS X > The hosts file may also be blocking the iTunes Store. If you have software used to perform unauthorized modifications to the iOS device, uninstall this software prior to editing the hosts file to prevent that software from automatically modifying the hosts file again on restart.

what s problem my iphone is not conneting to itunes is showing 21error i plz rectifie my problem

To solve problem with iTunes error "An unknown error occurred (21) " you have to edit hosts file and comment the line with saurik auth servers like this #74.208.10.249 gs.apple.com, or you can use redsn0w restore extra features to force your iphone restore.

The hosts file may also be blocking the iTunes Store.

If you want to have Windows try to restore the hosts to default, follow the "FixIt" in How do I reset the hosts file back to the default?.

Note: Work systems may put information into the hosts file. Consult whomever is responsible for supporting Windows on your system before resetting the hosts file to default.

If restoring the defaults did not resolve the issue, you can find your hosts file at C:\WINDOWS\SYSTEM32\DRIVERS\ETC .

Select the hosts file. Choose Edit > Copy, and then choose Edit > Paste.

There should now be a duplicate of the hosts file named "Copy of hosts" (Windows XP) or "hosts -Copy" (Windows Vista/7).

Drag the original hosts file to your Desktop. If Windows needs your permission to continue, click Continue.

Drag the "Copy of hosts" (Windows XP) or "hosts -Copy" (Windows Vista/7) to the Desktop.

Right-click "Copy of hosts" (Windows XP) or "hosts -Copy" (Windows Vista/7) and choose Open. You may be prompted to choose the program you want to use to open this file. Double-click Notepad.

When Notepad opens, choose Edit > Select All, and then choose Edit > Delete.

From the File menu,choose Save. Quit Notepad.

Drag the "Copy of hosts" (Windows XP) or "hosts -Copy" (Windows Vista/7) file from your Desktop back into the original location (given in step 2). If Windows needs your permission to continue, click Continue.

Right-click the "Copy of hosts" (Windows XP) or "hosts -Copy" (Windows Vista/7) file, and choose Rename. Type "hosts" (without quotation marks) and press Enter.

Restart your computer and try connecting to the iTunes Store.

I have also this problem where when tried to transfer files from iPhone to PC encountered error message which stops my work in between and this situation I would not be able to understand what effective steps required to take so that transfer can be easily. iTunes application also not work and show error which is known as inbuilt application.Lastly I used iPhone transfer tool which works out to be best and helped to transfer files. My problem get easily how to restore iTunes error 21.

Read More:

http://www.iphoneimagerecovery.com

I know what to do. Under the mainframe is a another frame that you have to fix the spokes if they are bent. This happens due to dropping the iphone. :)

There are many who would like to make transfer of files . Where it is easy and possible to make transfer of files. It is too difficult when try to transfer files with iTunes application. Using tools it is posisble to make transfer of filesEasy to make iPhone 5 Mac transfer].

http://www.iphone5tomactransfer.com

Just plugged my I-Phone 5 to Itunes left it there and did a restart on my computer with the phone still plugged in when it started up again I-Tunes opened and did the restore with no error codes. Hope this helps. May not work everytime but worked for me.

Replaced with a brand new battery and problem solved

same problem i changed the battery or charge the broken battery with 12Volt directly it will work

Error 21

First try to replace the battery .

still the same issue ?

if you plug in your charger and turns on immediately that means the battery connector piece on the motherboard is broken or missed place. you need a technician for that .don't wast your time trying to fix it if you are not familiar with this-----

https://i.ytimg.com/vi/t_iczh67BV8/maxre...

Hello Friend, I had this problem. struggled with it back n forth methods docking-redocking, hold power n home buttom etc but it kept throwing the same error. iPhone screen remains having an itunes logo with charger connected to it.

i've changed my dock to a different usb port, iPhone starting responding and update started. try this, may be helpful to you

hay qua ad oi . tai gioui

change the battery of iphone

I just disabled firewall and tried again. Boom! It worked.

Was so frustrated at first.

one day i can see ios update on my iphone 4s device.So i have accepted this after that my ios device is not restore and not update

Sorry if I’m 9 years late lol but for anyone who’s getting the iTunes error 21 is caused by a bad battery on ur iPhone and needs to be replaced hopefully anyone who reads this worked for yall :D

Wipe your phone in system