Put your iPhone into recovery mode. If you do not know how to do this then you can follow this tutorial.
Launch the USBView application. If you do not already have this application you can download it here. It is a small free utility provided by Microsoft.
Click to select Config Discriptors from the Options menu.
Click to select Refresh from the File Menu.
Select the Apple Recovery (iBoot) device from the USB Device Tree in the left panel then Copy (highlight and press Control+c) your ECID from the Descriptor fields on the right.