Most owners of mobile equipment, including such as an iPhone, are well aware and able to perform the recovery and flashing procedure. Unfortunately, sometimes this process ends with the appearance of some regular failure. For example, it could be error 21 when restoring iPhone.

I would like to note right away that it is not always possible to fix such a nuisance. Unfortunately, sometimes error 21 does not occur because of a software glitch, but because of a hardware failure. Naturally, in this case, only the help of a good specialist is required.

It is clear that you should contact the wizard only after you have not been able to solve the problem on your own using the methods suggested below.

An attempt to solve the problem by program methods

So, if an unknown error occurred on a mobile phone, then it should be diagnosed. If, when you try to connect the phone to a computer or connect the charging cable, it starts to show the Apple icon, and then, literally three seconds later - the iTunes logo and the lanyard, then this is clearly a nuisance with code 21. This statement is confirmed by the black screen that appears instantly after disconnecting cable.

So, if it was not possible to restore the iPhone 4s precisely because of such a nuisance, then it is recommended to try the following method:

You need to act in the same way when restoring iPhone 5.

Unfortunately, this method does not always lead to the desired result. In this case, you should do the following:

If there is no result, then, unfortunately, the problem is a hardware malfunction.

Hardware solution to this problem

It is clear that I don’t want to carry the phone to the service center. Usually, not the smallest money is taken there for repairs. Therefore, if you have some experience with electronics, then you can try to carry out the following checks:

If the actions at home did not bring results, then, as you do not want, you will have to carry it to the workshop. In this case, there is one recommendation - try to bypass as many of these service centers... This can sometimes lead to real cost savings. In one place they will name one price, in another - two or three times lower!

Hello everyone, we decided to investigate error 21 when restoring iphone 4s. In this article, we will tell you about the causes of the error and how to solve it.

Symptoms do not turn on, and when the cable is connected to the PC or to the network, it shows an apple and after 3 seconds the lace and aytyuns icon, if the cable is disconnected, it immediately displays a black screen.

Software solution to error 21

Trying to restore the iphone in DFU Mode:

• Connect the device to your computer using a USB cable (original);

• Press the Power button (in the upper right corner) and hold it for 3 seconds;

• Without releasing the top Power button, press the HOME button (which is at the bottom center) for 10 seconds;

• Without releasing the HOME button, release the Upper Power button while continuing to HOLD the HOME button for 10 seconds;

• Launch iTunes. The program will detect the iPhone in recovery mode;

• Hold down the "Shift" key on your keyboard and click on "Restore" (Mac users should press "Alt + Restore");

• Open the previously downloaded firmware file with the extension ".ipsw". ITunes will take over the further work, wait until the end of the process.

If you can't clear the hosts file. Open the file C: \ Windows \ System32 \ drivers \ etc \ hosts (Windows) with notepad and put the # sign in front of all lines containing "gs.apple.com" and127.0.0.1 localhost or remove them. Save. Close. Re-flash.

You can also take advantage of the following programs to enter the device in the DFU Mode Pwnage Tool, sn0wbreeze or redsn0w.

Hardware solution to error 21

The repair technique is as follows: Replacing the battery - Replacing the lower loop - soldering the battery connector (1) - jumpers (error 29 solved on youtube) - check the quartz (2) - replacing the power controller (4) - reballing the processor - garbage.

• The first step is to check the voltage on the battery, if it is less than 3.7 V, then we put it on charge using a "frog" or directly connect the wires to the battery;

• The second is to check the ribbon cable and connectorthe power supply must be undamaged;

• Third, remove the power cables, motherboard and put in place;

• The fourth replacement of the power supply ( it should be desirable from the original iPhone);

• Fifth check the controller if necessary, replace the power supply.

Practical experience correcting error 21

The apple is on when it is turned on and a constant reboot, when the cable is connected - the aytyuns icon and that's it. When I connected it to the computer via a cable, the program said that it needed to be updated or restored.

When flashing / restoring, there was ERROR 21. With this, the voltage on the battery was only 3.6 volts for charging, it did not react when measuring the voltage on the board was 0. After disassembling the device, an oxide was found near the capacitor C135 next to the transmitter. the capacitor dropped out, put it on charge - charging went on the connector of the battery board, a voltage of 1.2 volts appeared during firmware / recovery, it gave error 6.

I switched to another computer with windows 7 64 bit and disabled the antivirus and firewall. Connected only the phone, not connecting third-party USB devices, the Internet was via Wi-Fi, the firmware was downloaded separately and during the firmware I pressed the Shift button and selected the firmware file (preferably a path without Russian letters). Update failed, restored. It didn't work the first time. So you have to try. At first, there was also an error 6. As a result of long attempts, everything worked out. TA started working. Try it might help.

Similar components on iphone 5

Red - GSM / GPRS / EDGE signal power amplifier, Skyworks 77352-15;
Orange - module for switching between antennas SWUA 147 228;
Yellow - UMTS signal power amplifier, also known as duplexer, Triquint 666083-1229;
Green - dual-band LTE duplexer Avago AFEM-7813;
Blue - CDMA signal power amplifier, Skyworks 77491-158;
Purple - LTE signal power amplifier, Avago A5613 ACPM-5613;


Red - Qualcomm PM8018 RF power controller;
Orange - Apple 338S1131 power controller, manufactured by Dialog;
Yellow - Hynix H2JTDG2MBR 16GB flash memory chip;
Green - multi-chip auxiliary memory module for LTE, Apple 338S1117, manufactured by Elpida;
Blue - STMicroelectronics L3G4200D triaxial gyroscope, as in iPhone 4S and iPad 2;
Purple - Wi-Fi module Murata 339S0171.


Red - STMicroelectronics LIS331DLH triaxial accelerometer with low power consumption;
Orange - single-chip controller touch pad Texas Instruments 27C245I;
Yellow - Another touchpad controller, Broadcom BCM5976;
Green - Apple A6 chip;
Blue - the vaunted Qualcomm MDM9615M LTE modem for both voice and data;
Purple - RTR8600 multiband transceiver, as in ... Galaxy S III.

Many users have heard a lot about the quality of Apple products, however, iTunes is one of those types of programs, when working with which almost every user at least once, but encounters an error in work. This article will discuss how to resolve error 21.

Error 21 usually occurs due to hardware malfunctions of the Apple device. Below we will look at the main ways that can help solve the problem at home.

Method 1: update iTunes

One of the most common causes of most errors when working with iTunes is updating the program to the latest available version.

All you need to do is check iTunes for updates. And if available updates are found, you will need to install them and then restart your computer.

Method 2: disable antivirus

Some antiviruses and other security programs may accept some iTunes processes for viral activity, and therefore block their work.

To check this probability of the cause of error 21, you will need to disable the antivirus for the time being, and then restart iTunes and check for error 21.

If the error disappears, then the problem really lies in third-party programs blocking iTunes actions. In this case, you need to go to the antivirus settings and add iTunes to the list of exclusions. Additionally, if you have such a function active, you will need to deactivate network scanning.

Method 3: replace the USB cable

If you are using a non-original or damaged USB cable, then most likely it was this cable that caused the error 21.

The problem is that even those non-original cables that have been certified by Apple may sometimes not work correctly with the device. If your cable has kinks, twists, oxidations and any other types of damage, you will also need to replace the cable with a whole and always original one.

Method 4: update Windows

This method rarely helps to solve the problem with error 21, but it is provided on the official Apple website, which means it cannot be excluded from the list.

For Windows 10, press the keyboard shortcut Win + I to open the window "Parameters" and then go to section Update and Security .

In the window that opens, click on the button Check for Updates ... If updates were found as a result of the check, you will need to install them.

If you have a younger version of Windows, you will need to go to the menu "Control Panel" - "Center windows updates"And check for additional updates. Install all updates, including optional ones.

Method 5: restore devices from DFU mode

DFU is an emergency mode for Apple's gadgets, which is aimed at troubleshooting device operation. In this case, we will try to enter the device into DFU mode, and then restore it through iTunes.

To do this, completely disconnect your Apple device, then connect it to your computer with a USB cable and launch iTunes.

To enter the device in DFU mode, you need to perform the following combination: hold down the power key and hold it for three seconds. After that, without releasing the first key, hold down the Home key and hold both keys for 10 seconds. Next, you just have to release the power key, but continue to hold "Home" until your device is detected by iTunes (a window should appear on the screen, as shown in the screenshot below).

After that, you will need to start device recovery by clicking on the corresponding button.

Method 6: charge your device

If the problem lies in a malfunction of the battery of the Apple gadget, then sometimes full charging of the device to 100% helps to solve the problem. After fully charging your device, try the recovery or update procedure again.

In conclusion. These are the main methods that you can follow at home to solve error 21. If this does not work for you, the device most likely needs to be repaired. only after carrying out diagnostics will the specialist be able to replace the defective element, which is the cause of the malfunction with the device.

Apple products are renowned for their reliability, but errors often occur when using iTunes. Probably every Apple gadget user at least once, but faced this. Errors can occur due to a system failure or hardware failure. ITunes error 21 is hardware related.

You decided to update the device system and encountered error 21. How can it manifest itself? An error message appears and the iTunes working window closes, after which it will be impossible to work in the program. After the error appeared, the computer turned off. You received a notification that says "iTunes Error 21". The operating system on the PC is slow when you issue commands through the mouse or when typing on the keyboard. Sometimes the PC freezes for 3 - 4 seconds.

Such a failure can give alerts not only when working in iTunes itself, but also when using components associated with it. When the PC shuts down or when it turns on, there may also be a crash alert 21. By tracking the occurrence of the crash in time, you can easily fix the problem.

Causes of occurrence

This failure may occur due to incomplete installation of iTunes components or damage to these files. It can occur if the registry that is responsible for the iTunes program is damaged. This can happen due to the installation or removal of software that works with the program.

System or program files have been damaged by malware or viruses. The files necessary for the correct functioning of iTunes by another program were deleted (intentionally or accidentally). The most common reason for the error is updating a jailbroken device.

How to fix Error 21

If you need to update your jailbroken device, use DFU recovery using the "Redsn0w" program. Redsn0w allows you to restore any gadget from any state. In order to eliminate the failure, enter the device into DFU mode by simultaneously pressing and holding the "Home" and "Power" buttons for 10 seconds. After that, stop pressing "Power" while continuing to press "Home" until the message about emergency recovery of the gadget appears in the iTunes window.

In this case, the display of the device must be without images. Wait for another message “The iDevice“ iDevice ”could not be restored ...” to appear and restore the IPSW. Other methods are aimed at fixing the crash of non-jailbroken gadgets.

Updating or Installing iTunes

Check if there are updates for the program and update it to the latest current version... If that doesn't work, try uninstalling and reinstalling it completely. Keep in mind that uninstallation may not remove all program components. Therefore, remove it using a special utility for complete removal. Only then install iTunes again.

Disable antivirus software

Virus tracking software can interpret the program's actions as malicious activity and, as a result, stop it using blocking tools. In order to avoid such situations, you can turn off the antivirus program while working in iTunes or fix failures by disabling the antivirus program after they appear.

In the future, you can add iTunes to the list of exceptions. As a result, the antivirus program will not block its activity. You can do this in the settings. Provided that this function is already active, you need to disable network scanning.

USB cable

Failures can be caused by the use of non-original components or those that are damaged. Replace the non-original cable with an original one. If you are using the supplied cable, check its integrity. Do not neglect such a trifle, the use of good components can extend the life of your devices and get rid of such failures.

OS update

To update Windows system 10 Press the two keys "Win" and "I". This combination will open the options window. Here you need to open the "update and security" section. A workspace will open in front of you, where there is a button "check for updates". Click it. If updates are found, install them.

When using an earlier Windows versions open the "control panel". Here click on Windows Update and run a test. If updates are found, install them.

DFU mode

This mode is for disaster recovery... It works at the hardware level bypassing operating system... Turn off the device completely and after a couple of minutes connect it to a PC via a USB cable. Open iTunes. To enter the gadget into DFU mode, you need to hold down the "Power" button for three seconds and then also hold down the "Home" key. Keep them clamped for 10 seconds. After this time, stop pressing the "Power" button, but hold "Home" until an alert appears in iTunes that the gadget is in emergency recovery mode. Click on the "restore" button.

Garbage disposal

When using a PC, over time, a lot of unnecessary information accumulates in it. It can slow down the OS and cause error 21. This happens due to conflicts between files or when there is a heavy load on HDD... You can remove garbage with the Cleanmgr utility. It is built into the system, but it has several disadvantages. For a more complete cleaning, it is better to use WinSweeper.

To activate the process, click "start". Then specify "command" in the search string. Now hold down the Shift keys and CTRL click Enter. In the access dialog box, click "yes". A blinking cursor indicates an open black box. Type "cleanmgr "And click Enter. In the dialog box, place a checkmark in the places where you want to clean. Pressing "ok" will start the cleaning process.

You can also restore registry entries. But it is not worth doing it yourself if you are not an expert in this matter. With this question, it is better to contact a person qualified in this area, otherwise you can harm the PC and disable it. If the above methods do not work, go to the repair center to diagnose the device. Hardware repair may be required.

Specially designed by Apple for working with devices on the iOS platform, provides apple owners with synchronization of the device with a computer, convenient work with content and a host of other functionalities, including firmware recovery. The procedure performed with iTunes is easy to carry out, but during operation, unexpected problems may arise that interrupt the action. With the help of notifications with error codes, the program informs users about software failures or problems with hardware. Error 21 in iTunes may occur when updating or restoring iPhone firmware different versions. The program crash messages appear for various reasons. Error 21 most often indicates mechanical damage to the device resulting from malfunctions of the modem, device battery, internal cards and other components, but it can also appear as a result of software failures during the jailbreak process. Another reason is often low battery power or battery failure.

Troubleshooting options for error 21 in iTunes.

Though given failure often provoked by micro-damage after a blow or fall, as well as other hardware malfunctions, there are software solutions with which the user can cope with the problem on his own.

Method 1. Update iTunes

A universal method that often allows you to get rid of most application crashes when updating or restoring iPhone 4s and other "apples", in some cases also eliminates error 21. If the computer is not the latest version of iTunes, then after updating and restarting the PC, the problem may be resolved.

Method 2. Replacing the USB cable

Sometimes error 21 can be caused by damaged cables or using a non-original cord. But even if the original equipment is used, it is necessary to inspect it for kinks, twists, oxidations and other minor defects. The correctness of the interaction of the device with the computer largely depends on the integrity of the cable, therefore, if any damage is found, it should be replaced with a serviceable original cable.

Method 3. DFU mode

By activating the DFU emergency mode, you can often get rid of many failures that occur during the update and recovery process, including error code 21. For iPhone 4s and other versions, the procedure is similar. Before entering the device into DFU mode, turn it off completely, and then connect it to the computer using the original USB cable. Next, we carry out the following actions:

• press the "Power" button and hold it for 3 seconds;
• without releasing the top power button, we also hold down “Home” and hold it for 10 seconds;
• after this time, release only the "Power" button, while "Home" continue to hold until iTunes detects the device in DFU mode;
• after the performed manipulations, the program will offer to perform the only action - restore the iPhone. Next, you need to follow the instructions on the monitor.

Method 4. Disable antivirus

Some antivirus programs, firewalls, and other system defenders can block iTunes processes, treating them as viral threats, as a result of which the error that appears prevents the continuation of the procedure. You can pause the work of the antivirus while the firmware is being restored and after restarting the application, see if error 21 is observed again. If the problem is resolved, you need to add iTunes to the antivirus exclusion list, and also cancel network scanning.

Method 5. Windows update

In rare cases, updating system components helps, for which you need to go to the update and security settings of Windows and search for available updates. If they are found, it is worth installing.

Method 6. Fully charge the device battery

When the source of the problem is the battery of the Apple device, the method of fully charging the battery often helps. After the battery has been charged to 100%, you can try the update or restore procedure again.

Method 7. Restoring registry files

Restoring registry entries can often help you fight iTunes errors if files have been corrupted by viruses or accidentally deleted by conflicting programs. The automatic fix will help you run the Microsoft tool WinThruster. The program scans, then replaces the damaged files with "healthy" ones. Manually adjusting the registry is only possible if you have special skills. Self-correction without certain knowledge can significantly disrupt the operation of the system.

Method 8. Hardware solution

If none of the above methods led to the elimination of error 21 in Aityuns, most likely the problem lies in internal damage to the device. Diagnostics in the service will help to pinpoint hardware faults. It may be necessary to replace the battery, power controller or bottom cable and it is better to entrust the matter to a specialist.

You should not solder or change elements on your own without having the appropriate skills, because one wrong action can only aggravate the situation and lead to irreparable consequences in the form of the final failure of the iPhone.