Google Android Hidden Secret Codes

• Fast Boot mode 
• Download mode
• Recovery mode

WARNING: All these modes are used to flash/reset phone firmware. Think twice before entering in these modes.

Fast Boot Mode

This mode is used to flash the phone firmware using command line tools. To access this mode:

• Power off your phone.
• Press and hold Call and End Call/Power keys.

Download Mode

This mode is also used to flash the phone firmware. Mostly this mode is used by GUI tools for easier and quicker flashing. To access this mode:

• Power off your phone.
• Press and hold Volume Down, OK and End Call/Power keys.

Recovery Mode

This mode is used for recovery purposes like to reset the phone firmware. To access this mode:

• Power off your phone.
• Press and hold Volume Down, Call and End Call/Power keys.

Once the alert triangle is shown on screen, press "Menu" key to reset the firmware or press "Home" and "End Call/Power" keys to show recovery menu.