Secret Codes helps you to access some internal functions of mobile which are intended for developers and troubleshooting purposes. They are the combination of numeric and Special Characters like * and #.
These codes can give you access to the whole new world of hidden menu, diagnostics test and much more.
So, here i am going to show you how to access the internal function of HTC One M8 Touch screen android phones for testing 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, earphone, sub key, etc… if you have any hardware problem with your phone you can identify with this code if it is working or not to do this follow the steps below.
Step 1 : First of all open your keypad (where you dial the phone numbers)
Step 2 : Then dial the secret code *#*#3424#*#*
This will open up a HTC Function Test Program as shown in figure ( you need to click accept to proceed)
Then select the test you need to perform and press the Run key.
(Click more to get list of some more codes)
One more code that you can try on you HTC mobile phone is *#*#4636#*#*
By dialing this code on the mobile you can get information on phone, battery, wifi and some usage statistics like shown in the image below
There are plenty more of these to be found on the internet, these are just some of the best ones.