Errors are always there, even Apple has anticipated that, that’s why the errors gets categorized into error codes. The categorization of iPhone errors makes the solution of the problem easier, because we have the Internet, the most powerful knowledge tool, discovered by mankind. Here, this article that guides you to a step by step recovery process to resolve iPhone Error 21.
The Error 21 Problem
The iPhone error
21 arises due to a technical compatibility issue. That goes to say that the error appears when you are upgrading your phone with the latest iTune software and your phone struggles to match its hardware with the upgrade, thereby giving rise to the Error code 21. Not to say, that the error code will always appear whenever you are upgrading your iPhone, but there are several other iPhone users who are facing or have faced this issue. As this error appears, there is no need to despair though because presented here is the step by step solution to solve the problem.
The Solution for iPhone Error 21
First, to troubleshoot, you will have to set right the fundamental issue. The fundamental issue here is setting the mode of the iPhone to facilitate smooth upgrade of the device. Your iPhone should ideally be in the DFU mode, while upgrading it, in order to minimize the possibility of the Error 21 appearance. So, first you check out whether your phone is in the DFU (Device Firmware Update) mode or not. A completely black screen signifies the DFU mode even when the phone is completely turned ON. If your phone is not in the DFU mode, then here is how to get there. Setting the phone to DFU mode will supposedly solve the iPhone Error 21 occurrence.
Step 1: First, you need to simultaneously press the Home key and the Power key.
Step 2: A notification will appear to slide the bar to turn off. Ignore it.
Step 3: If you are seeing your screen black, that means you are in the DFU mode.
Step 4: In DFU mode, your iTunes software will be disconnected from your iPhone.
Step 5: Now, you will have to hold down on the Home key and let go the Power key. Hold down the Home key, unless your device gets completely reconnected with the iTunes software.
Step 6: This should bypass the Error 21.
Congratulations! You just did it; resolving the iPhone Error 21 by yourself without contacting your local Apple store or the tech support. However, if the problem persists (which it ideally should not be, unless every step has been followed correctly), do consider contacting
the tech support from Apple.