How to fix iTunes error -1 during iPhone restore to iOS 5.0.1 or other iOS version?
If you get error -1, most likely you attempted to flash with iPad baseband 6.15.00 with the intention to unlock it. Error -1 is related to baseband failure.
iPhone 3GS made after week 28 of year 2011 is not compatible with iPad baseband. If the baseband flashing process fails, you will get no IMEI, no Bluetooth and no WiFi error. It may reboot every 5-10 minutes due to this error.
Currently there’s no software fix available. However, if you intend to restore it, do the following:
1. Download custom iOS 5.0.1 firmware from here.
2. Pawn DFU your iPhone with redsn0w 0.9.10b5 or iREB from ih8sn0w.com.
3. Launch iTunes 10.5 and hit shift + restore or option + restore for Mac).
4. Point to the custom firmware you just downloaded in step 1.
If all goes well, the restore will complete. Once activated, go to Settings, General, About. If you see no IMEI, no Bluetooth and no WiFi, your baseband chip is broken. Contact your nearest Apple store to get a replacement (if you have a warranty). Alternatively, these guys may be able to fix it for you.