Hey friends after reading and testing all htese secret codes i am going to reveal the secret code of samsung galaxy s4.. How it is helpful to you??? It helps us in accessing the internal functions of the device and used for testing all the various hardware parts of your phone if it is working properly or not with the help of this secret code you can test lcd, vibration, camera, sensor (accelerometer sensor, proximity sensor, magnetic sensor), touch screen, speaker, sub key, etc... Are you having any problem withj your galaxy s4 device ?? You can solve ouit any hardware problem with your Galaxy S4 and can identify code if it is working or not to do this follow the steps below. **You have to dial these codes on your dialpad.. Then dial the secret code *#0*#. Now you get a screen with title LCD TEST and below that you have lots of option to test various hardware parts of your phone such as speaker, sensor, lcd, etc To go back use right physical button while testing the