A simple factory test menu is present that was used during the hardware's production to check if the handheld works as intended. To access the menu, power off the console by pressing the POWER button for 5 seconds while it's plugged in to any AC power outlet. Then hold Up + B, press POWER, then before the Mario Clock appears, release Up and B, and press GAME + PAUSE/SET.
After hitting this button combination, the system will cycle through the following tests:
Power (Eject / Insert / Current Battery Power + user confirmation)
Buttons (D-Pad / A / B / Face buttons)
RTC
Sound (Volume 0 / 5)
LCD (White / Black / Red / Green / Blue / Shade horizontal / Shade vertical)
If the test results are OK, hold B to power off. Upon booting back, the system will have its time reset to 12:00 PM, and any suspended game data will be reset (though all game records and progress will be intact).
The same menu is present in Game & Watch: The Legend of Zelda and accessed the same way, the only change being the ability to test the additional buttons the console has.
Eject the USB-C cable.Insert the USB-C cable.Check current: active charging.Check current: charging off, screen on.Check current: charger off and standby. Tests the standby option and has you press POWER again after the screen went black.Button test, D-Pad Up.Button test, D-Pad Up + Left.Button test, D-Pad Left.Button test, D-Pad Left + Down.Button test, D-Pad Down.Button test, D-Pad Down + Right.Button test, D-Pad Right.Button test, D-Pad Right + Up.Button test, A button.Button test, B button.Button test, GAME button.Button test, TIME button.Button test, PAUSE/SET button.Button test, D-Pad Left + A.RTC test, during the calculation process.RTC test that passed.RTC test that failed, triggered by halting execution with debugger while testing is in progress; cannot continue past this point.Speaker test starts on volume level 3. You can press GAME to continue to the next test.Speaker test, on the lowest volume.Speaker test, on the highest volume.Before the LCD test.LCD test, white screen.LCD test, black screen.LCD test, red screen.LCD test, green screen.LCD test, blue screen.LCD test, vertical shade.LCD test, horizontal shade. After this screen, you can press GAME to continue.You can also adjust the brightness using D-Pad Up and Down on any of the LCD test screens.Test result, this one passed.Test result, taken before shutdown.