With the way arm9loaderhax works right now, a formatted, dead, or otherwise deleted SD/microSD prevents you from booting the 3DS at all. Does that mean you have a brick? Not in the least! It is quite possible, even easy, to recover the ability to boot your 3DS, as long as you have a functioning SD/microSD. The purpose of this guide is to help you get your 3DS back into working order after you've lost the data on the system's SD/microSD (hereafter referred to as "SD card" or "SD"). It assumes you have no SD backups and no files saved locally to your PC. This tutorial will work for all 3DS models, including the 2DS. This guide will not recover save data, previously installed applications, StreetPass/Mii data, custom themes, or Home Menu configurations! If you don't have a SD card backup, you will have to start from scratch! Step 1 - Recover Boot Capability Download the latest version of Luma3DS. Extract the "3ds" folder and "arm9loaderhax.bin" to the root of your SD card. Boot your 3DS, which will boot into Luma settings automatically. Configure Luma, then press Start to save and boot into the Home Menu. ...That's it! Your 3DS will now boot normally. Easy, right? But you didn't install a9lh just to have a normal 3DS that doesn't boot without an SD, did you? Well, then, let's get to work on getting all of that delicious homebrew back. You might have noticed that all of your installed CIAs are gone. A temporary setback. Step 2 - FBI Inject Download the latest version of Hourglass9. Download the latest version of Universal Inject Generator (click "Clone or Download", then click "Download Zip"). Download the latest version of FBI. Create a folder on the root of the SD card called "luma". If you've booted your system after completing Step 1 and configured Luma, you can skip this step as there should already be a luma folder on your SD card. Create a folder called "payloads" in the luma folder on your SD card. Extract "Hourglass9.bin" into the payloads folder and rename it "start_Hourglass9.bin". Create a folder called "cias" on the root of your SD card. Extract "FBI.cia" to the cias folder. Create a folder called "Universal Inject Generator" on your PC (it doesn't matter where, so pick a place you can find easily). Extract the contents of the Universal Inject Generator zip file to the folder you created. Extract "FBI.cia" to the "input" folder in your Universal Inject Generator folder. Eject the SD card from your computer and place it in your 3DS. Press and hold the Start button while turning the power on. This should boot Hourglass9. Select the first option, "SysNAND Backup/Restore". Select the third option, "Health & Safety Dump". Use Left and Right on the D-Pad to select a name for the dump file ("hs.app" is the default), then press A to start the dump. If (!) appears after the file name, that means that file already exists on your SD card. Pick another name, just to be certain. Press B to return to the SysNAND Backup/Restore menu, then press Select to unmount your SD card. Remove your SD card from your 3DS and connect it to your PC. You do not have to power off your 3DS to do this. There should now be a "files9" folder on the root of your SD card. Browse to it, and find the Health & Safety dump you just made (file name should be whatever you selected). Move hs.app (or whatever your dump is called) to the input folder in Universal Inject Generator. Run Universal Inject Generator by running "go.bat" (Windows), "go.sh" (Linux/Unix), or "Mac_Script_Launcher.applescript" (Mac). When it's finished, place "FBI_inject_with_banner.app" in the files9 folder on your SD card. Eject your SD card from your PC and insert it into your 3DS. Press B to return to the SysNAND Backup/Restore menu in Hourglass9. Select the fourth option, "Health & Safety Inject". Enter the key combination Hourglass9 asks for, which should be "Left, Up, Right, Up, A". Select FBI_inject_with_banner.app using Left and Right on the D-Pad and press A to inject. Wait for the inject to finish, then press Start to reboot into the Home Menu. You will now have an app called FBI in place of the Health and Safety app on your Home Menu. The FBI icon (a blue square with the letters "FBI" inside) should now show up on your Home Menu, but if it doesn't, check the Health & Safety icon. If FBI was properly injected, the FBI banner should show up in place of the normal Health & Safety banner. This is a bit "dirty", though, so let's actually install FBI. Step 3 - Install FBI Start your Health & Safety FBI. Select "SD". Select "cias". Select "FBI.cia". Select "Install". And now you have a "legit" installation of FBI on your 3DS. This version can be updated without risk. You can now install other homebrew apps on your 3DS through this "legit" FBI. I recommend at least installing Homebr3w (an installer and manager for homebrew apps) and lumaupdate (an automated updater for Luma 3DS), but as you know, there's a whole world out there for you to explore. Step 4 - Re-inject Health & Safety This step is completely optional. Some people like keeping their Health & Safety FBI around as insurance against something like this ever happening again, especially since H&S is pretty useless. This is fine, but there's also a risk that a future OFW update might make that version of FBI unuseable, which would require you to re-inject FBI anyways, because I'm pretty sure Health & Safety injected FBI cannot update. If you want to put your Health & Safety app back to what it should be, follow the steps below from a completely powered-off 3DS: Press and hold start while pressing the power button to boot into Hourglass9. Select SysNAND backup/restore. Select Health & Safety Inject. Enter the key combination. Select your Health & Safety dump using Left and Right, then press A to start the inject. Wait until the inject is finished, then press Start to reboot into the Home Menu. And now you should have your normal Health & Safety app back.