LG Optimus G E973 hard reset1. Turn the phone off.
2. Press and hold Volume Down Key + Power/Lock Key at the same time.
3. Release the keys when the FACTORY HARD RESET screen appears.
4. Read the warning and press the Power/ Lock Key to confirm. Press any other key to cancel.
5. Press the Power/Lock Key to confirm once more or press any other key to cancel.
6. Your device will perform a hard reset.
or via menu
To reset your LG Optimus G E973 hard reset phone to factory settings and erase all the data on your phone, Select Settings → Back up and reset→ Factory data reset → Reset device→ Delete all.
On Android ICS or Jelly Bean 4.0 4.1 or higher
Resetting the phone does not erase any system software updates you have downloaded or any files on your microSD card, such as music or photos. If you reset the phone in this way, you are prompted to re-enter the same information that you did when you first started Android.
You can use LG Mobile Support tool to repair your LG cell phone, after download select menu Customer Support > Recovery Phone