I've been advised that LG is working on a software solution for this problem.
I've found a hardware solution which worked perfectly on my phone for the past few weeks. Day to day use may lead to a build up of hand oils and dirt that weaken or break the circuit to the scanner. The process below safely cleans the rails:
- What you need: isopropyl alcohol, prepackaged swabs or bottle (readily available at drug and grocery stores), cotton swabs, lint free towel to dry, latex gloves (optional)
- Turn off the phone
- Remove the back cover and battery
- Reinstall the cover only
- Prepare a cotton swab with alcohol - do not saturate the swab, just make it wet. You don't want a lot of excess alcohol dripping on phone.
- Lay the phone on one long edge (metal rail edge) and keep it upright with one hand: thumb and forefinger in a pinching motion works well. Do not touch the metal rail with your hand.
- Swab the length of the exposed metal rail up a few times, dry with the cloth, swab a second time, then dry.
- Rotate the phone, being careful not to touch the cleaned rail with your fingers....yet
- Clean the other rail the same as the first.
- Make sure all surfaces are dry.
- Reinstall the battery and start the phone.
The fingerprint scanner should now work. If it does not...check the power button for noticeable dirt or grease. With the battery removed, you can carefully clean it with alcohol with a Q-tip or similar swab INSIDE THE BLACK ring....do not use too much alcohol. Note: I do not know if cleaning the power button is a warranty problem. Should not be as long as the battery is out and you don't soak the button. Again, make sure everything is dry before reinstalling the battery.
One other note: I've found that if my finger is dirty from working with tools or in dirt...or still wet/moist from washing my hands or taking a shower, that the scanner does not work until my finger is dry and clean.
I performed this service on my phone over 2 weeks ago and it continues to work perfectly.