LG Optimus L4 II Guide De L'utilisateur page 388

Troubleshooting
Message
The screen
does not turn
on when I
receive a call.
No sound
Hangs up or
freezes
88
Possible causes
Proximity sensor
problem
Vibration mode
Intermittent
software problem
Possible corrective measures
If you use a protection tape or case,
make sure it has not covered the
area around the proximity sensor.
Make sure that the area around the
proximity sensor is clean.
Check the settings status in the
sound menu to make sure you are
not in vibration or silent mode.
Try to perform a software update via
the website.