Restore Errors/20xx

Errors 2000-2009 (from Apple support): If you experience this issue on a Mac, disconnect third-party devices, hubs, spare cables, displays, reset the SMC, and then try to restore. If you are using a Windows computer, remove all USB devices and spare cables other than your keyboard, mouse, and the device, restart the computer, and try to restore. If that does not resolve the issue, try the USB issue-resolution steps and articles listed for Error 1604. If the issue persists, it may be related to conflicting security software.

Error 2001

 * The Mac OS X kernel extension "IOUSBFamily" that was bundled with late 2008 / early 2009 MacBooks, as well as the 10.5.6 update, has a bug where it fails to properly recognize an iDevice in DFU Mode. It can be resolved by updating to 10.5.7 (or later), or using a USB hub.
 * Close limera1n.

Error 2002
iTunes can't connect because another program is using it or it's disconnected during the Apple Server check.

Error 2003

 * Connection problem; change USB cable and check USB port.
 * sn0wbreeze failed to restore IPSW; unplug and plug iDevice and try again

Error 2005
Problem connecting. Probably a hardware failure.

Somebody reported that reinstalling the USB drivers fixed the problem.

Error 2006
Replace the USB cable with a newer one and/or disconnect all other USB devices, then retry.

Error 2009
If you experience this issue on a Mac, disconnect third-party devices, hubs, spare cables, displays, reset the SMC, and then try to restore.

If you are using a Windows computer, remove all USB devices and spare cables other than your keyboard, mouse, and the device, restart the computer, and try to restore.

If that does not resolve the issue, see Error 1604 above. If the issue persists, it may be related to conflicting security software on your computer.