Hi @hariharapandian,
If you are finding your handset is turning black on calls this may indicate the proximity sensor that is developed to turn the screen off on calls when by your ear is being covered by something.
The most common cause of the issue you are experiencing is that a case, film or screen protector is covering this sensor.
All Xperia devices have a protection film which is a thin transparent adhesive film that covers the touchscreen when you first buy it. When the protection film is on, it covers the proximity sensor which is placed on top of the phone beside the ear speaker.
If you have a screen protector or case you have put on the phone or you have left the protection film on the phone we would first advise to remove these and test the device either on a call or through the diagnostics.
To check the Proximity sensor functionality with Diagnostics
- From your Home screen, tap the Applications screen icon.
- Find and tap Settings > About phone > Diagnostics.
- Tap Test device > Ear Proximity/Ear Sensor.
- Tap Test then cover the top of your screen (around the Sony logo) with your hand.
- If the phone vibrates only when the phone is being covered but stops when it is not covered this indicates the sensor is working correctly.
- If the phone either vibrates constantly or not at all this indicated that something is causing the sensor to not respond correctly.
If the sensor fails the test once any cases, films or screen protectors are removed I would recommend you perform a software repair using Xperia Companion on your handset.
