All iTunes Error Code with How to Solve It .

Error 1
Unable to downgrade. Try changing the USB port (the back one of chassis is better) and restart computer.
The installed version of iTunes may also be too old. Update iTunes.

Error -1
Error occurs when one uses the "last ditch" method for preventing baseband updates on the iPhone 4. The baseband does not get updated using this method. Use FixRecovery to kick it out of recovery mode.

Error 2
Sn0wbreeze 1.6 Custom Firmware has a ASR patch problem. Use sn0wbreeze 1.7 or PwnageTool. Device isn't bootable.

Error 6
Not enter the downgrading mode, change USB port (the back one of chassis is better) and restart computer.

Error 9
Due to asr being patched, the SHA signature is automatically changed and after being resigned the kernel will refuse to use it. Therefore proper kernel patches are required. If necessary kernel patches are not applied, it will fail to load asr and error 9 would occur during restore.
Rebooting your PC may resolve this issue. Aslo it can be connection issue.

Error 10
LLB is missing from the IPSW. The device cannot be booted up. The trick to skip the baseband update no longer works.

Error 11
Removed bbfw file in the firmware folder of an unzipped IPSW.

Error 13
Occurs when you want to install a beta firmware with iTunes for Windows (actively blocked by Apple; beta users are developers and therefore must have a Mac).
Error 13 may also signify a USB problem. Check the USB connection and try other direct ports or maybe the USB cable is an older one. Device isn't bootable.

Error 14
Custom firmware update fail (PwnageTool). You have to restore the device with a custom firmware. Update to a custom firmware isn't working. Device isn't bootable. 2
USB Problem. Check the USB connection and try other direct ports or maybe the USB cable is an older one. Device isn't bootable.

Error 17
Custom firmware update fail (sn0wbreeze). You have to restore the device with a custom firmware. Update to a custom firmware isn't working.

Error 18
This occurs when the media library on the device is corrupt and cannot be modified or updated. Updating to the latest version of iTunes and then restoring should resolve this issue.

Passcode unlock for iPhone 4 iOS 7.0 / 7.0.4 / 7.1 / 7.1.2

This tutorial will support some owner of iphone 4 when forgot PassCode

or can't remember Passcode and for Education

This tools only support with the iPhone 4 (IPHONE3,1) revision is supported 

Gecko iPhone Toolkit

Download Gecko Tools for read passcode 

Download iPhone 4 (iPhone 3.1 Firmware Here )

How to read iPhone 4 Passcode with Gecko iPhone Toolkit

How to fix iPhone 5 error 14 when restore with iTunes

iTunes error 14 sometime cause from your Internet connection slow or stuck when you download ipsw file from another update source not update direct from apple site. Usually iTunes code error 14 will be pops up when you try to upgrade your iPhone, iPad or ipod Touch iOS version to 5.0 and above.