3ds_hw_test is a .firm application that tests a 3DS console's RAM for errors. There are plans to expand the test so it checks more types of hardware, but so far these plans are entirely a work-in-progress.
The latest release of 3ds_hw_test (the 3ds_hw_test.firm file)
Section I - Hardware Test
Power off the console and insert your SD card into your computer
Copy 3ds_hw_test.firm to the root of your SD card
Rename boot.firm to luma.firm
Rename 3ds_hw_test.firm to boot.firm
Reinsert the SD card into your console
Power on the console without pressing any other buttons
Press any button to start the test
The test will take around 30 minutes for an old model and around 45 for a new model
If you are unsure what model the console is, look at the shoulder buttons - a new model has four (L+ZL+ZR+R), and an old model has two (L+R
When the test finishes, press any button to turn the console off and insert your SD into your computer
Open the newly generated sd:/HWTEST.LOG file in a text editor, then scroll to the end and look at the line that says [ARM11] Done. ___ total errors detected.
If the number on this line is 0, your console's RAM is not the issue
If the number on this line is not 0, your console's RAM is dying and you need to either repair or replace the motherboard
Delete boot.firm and rename luma.firm to boot.firm
Place 3ds_hw_test.firm in the root of your SD card
Turn on your 3DS while holding HOME to enter the fastboot3DS menu
Select [+]Boot from file... -> sdmc: -> 3ds_hw_test.firm
Press any button to start the test
The test will take around 30 minutes for an old model and around 45 for a new model
If you are unsure what model the console is, look at the shoulder buttons - a new model has four (L+ZL+ZR+R), and an old model has two (L+R
When the test finishes, press any button to turn the console off and insert your SD into your computer
Open the newly generated sd:/HWTEST.LOG file in a text editor, then scroll to the end and look at the line that says [ARM11] Done. ___ total errors detected.
If the number on this line is 0, your console's RAM is not the issue
If the number on this line is not 0, your console's RAM is dying and you need to either repair or replace the motherboard