Before you take your jailbroken iPhone back to Apple store for service, one important thing you have to do is to remove the jailbreak and restore it back to the original setting. This is crucial as jailbreaking voids your warranty according to Apple.
However, it’s pretty easy to convert your jailbroken iPhone back to factory setting. This tutorial walks you through the steps to restore your iPhone. The procedures should apply to both iPad and iPod touch as well.
1. Connect your device to computer via USB.
2. Launch iTunes
3. Select your device in the left column of iTunes.
4. Click “Restore” button.
Note: If you need to restore to a specific version of firmware, press SHIFT (for Windows user) or OPTION (for Mac user) key and click “Restore” button. This will pop up a file dialog for you to select the firmware file (i.e. IPSW).
4. If you don’t want to lose your data (such as contacts, sms, photos), backup your iPhone by selecting the “Backup” option. Otherwise, just proceed to restore without backup.
From now onwards, iTunes will restore your device to the latest version of firmware. It’ll take some time for the restoration process. Once complete, your iPhone will be rebooted automatically. That’s it. Your iPhone is now returned to the factory settings with the jailbreak, as well as, all cydia applications removed.