FuseCheck Switch

FuseCheck
FuseCheck
General
Author	sthetix
Type	System Tools
Version	1.0.4
License	GPL-2.0
Last Updated	2026/06/16
Links
	Download
	Website
	Source

FuseCheck is a Nintendo Switch payload that checks your console's burnt fuse count against the installed firmware version to determine if Official Firmware (OFW) will boot properly.

This is critical for users who have been using CFW and want to know if they can safely boot into stock firmware.

Based on Lockpick_RCM_Pro, with fuse checking logic inspired by the fuse-check project and UI design from TegraExplorer Switch and NCA Database checking from NxNandManager Switch.

Features

Automatic Firmware Detection - Detects firmware version from SystemVersion NCA in SYSTEM partition
Hardware Fuse Reading - Reads burnt fuse count directly from hardware registers
Compatibility Analysis - Compares fuses against firmware requirements
Horizontal UI Layout - Clean, TegraExplorer-inspired interface
Fuse Database Viewer - Browse complete fuse requirements for all firmware versions
Scrolling Support - Navigate through unlimited database entries
Screenshot Support - Capture results with 3-finger touch gesture
Silent Key Derivation - Keys derived in RAM only, no files written to SD
External Database - Easy-to-update database file (no recompilation needed)
Auto-Return to Hekate - Launches bootloader/update.bin after exit

User guide

Why Do Fuses Matter

Nintendo uses a hardware anti-downgrade mechanism called "fuse burning." Each major firmware update burns additional fuses, and the console checks this count during boot:

Too few fuses burnt = Console will black screen on OFW boot
Correct fuse count = OFW will boot normally
Extra fuses burnt = Console will black screen on OFW boot

Installation

Download the latest zip from the Releases page.

Extract the zip to the SD card.

Boot into Hekate and launch FuseCheck.bin from the payloads menu.

Main Page (Fuse Check Results)

The main page displays:

Firmware Version - Auto-detected from SYSTEM partition
Burnt Fuses - Hardware fuse count from ODM6+ODM7 registers (X fuses burnt)
Required Fuses - Fuses needed for detected firmware
Status - Color-coded compatibility result
Detailed Info - What will/won't work based on fuse status

Controls:

VOL+ - View Fuse Database (all firmware versions)
Power - Return to Hekate
3-Finger Touch - Take screenshot

Fuse Database Page

View complete fuse requirements for all Nintendo Switch firmware versions:

System version ranges
Production unit fuse counts
Development unit fuse counts
Scroll indicator showing position [start-end/total]

Controls:

VOL+ - Scroll down (stops at bottom)
VOL- - Scroll up (stops at top)
Power - Return to main page
3-Finger Touch - Take screenshot

Status Indicators

FUSE MISMATCH

Condition: Burnt fuses < Required fuses
Result: OFW WILL NOT BOOT (black screen)
What will work: CFW (Atmosphère), Semi-stock (Hekate nogc)
What won't work: Stock OFW

FUSE MISMATCH (OVERBURNT)

Condition: Burnt fuses > Required fuses
Result: OFW WILL NOT BOOT (black screen)
What will work: CFW (Atmosphère), Semi-stock (Hekate nogc)
What won't work: Stock OFW
Note: This is very rare but can happen on some consoles

PERFECT MATCH

Condition: Burnt fuses = Required fuses
Result: OFW WILL BOOT NORMALLY
Note: System is in ideal state for both CFW and OFW

Database Configuration

FuseCheck uses an external database file for easy updates without recompilation.

Database Location

sd:/config/fusecheck/fusecheck_db.txt

Database Format

The database file supports two entry types:

Fuse Count Entries:

[FUSE] <version_range> <prod_fuses> <dev_fuses>

Example:

[FUSE] 21.0.0-21.0.1 22 1
[FUSE] 20.0.0-20.5.0 21 1
[FUSE] 19.0.0-19.0.1 20 1

NCA Entries:

[NCA] <version> <nca_filename>

Example:

[NCA] 21.0.1 e7273dd5b560d0ba282fc64206fecb56.nca
[NCA] 21.0.0 4b0130c8b9d2174a6574f6247655acc0.nca
[NCA] 20.5.0 23ce01f1fc55e55a783162d456e5ca58.nca

Comments:

Lines starting with # are treated as comments.

Updating the Database

When new Switch firmware is released:

Update the [FUSE] section with new fuse count from switchbrew
Update the [NCA] section with the new SystemVersion NCA filename
Copy the updated file to sd:/config/fusecheck/fusecheck_db.txt
No recompilation needed

A sample database file is included in the repository at fusecheck_db.txt.

How It Works

Hardware Initialization - Initializes display, storage, and DRAM
Silent Key Derivation - Derives BIS keys in RAM using Lockpick_RCM engine
Fuse Reading - Reads ODM6 and ODM7 fuse registers and counts all burnt fuses
SYSTEM Partition Access - Mounts SYSTEM partition using BIS key 2
Firmware Detection - Scans /Contents/registered/ for SystemVersion NCA
Database Matching - Matches NCA filename against external database
Compatibility Check - Compares burnt fuses vs required fuses
Status Display - Shows results in horizontal layout

Note: The Switch has two anti-downgrade fuse registers (ODM6 and ODM7). FuseCheck reads both registers to provide complete fuse coverage. As of firmware 21.0.0+, Nintendo has burned up to 22 fuses, with plenty of capacity remaining for future firmware versions.

Screenshots

Troubleshooting

Failed to derive keys

Cause: Unable to derive BIS keys from TSEC/Mariko firmware
What happens: The payload automatically reboots the console
Solution: If this persists, your console may have eMMC corruption or hardware issues

WARNING: fusecheck_db.txt NOT FOUND

Cause: The config folder with fusecheck_db.txt was not copied to the SD card
What happens: Cannot detect firmware version or verify fuse compatibility
Solution: Copy the config folder from the release archive to your SD card root (the path should be: sd:/config/fusecheck/fusecheck_db.txt)

Database file not found (in Fuse Database Viewer)

Cause: Missing fusecheck_db.txt on SD card
Solution: Copy the database file from the release zip to sd:/config/fusecheck/fusecheck_db.txt

Changelog

v1.0.4

Improvements
- Polished the landscape UI with cleaner top and bottom bars, improved spacing, and smoother action selection redraws.
- Improved Fuse Map scrolling so the header and footer stay stable while browsing entries.
Database
- Added firmware 22.5.0 database support.

v1.0.3

Added key dumping support aligned with Lockpick_RCM_Pro for firmware 21.x and 22.x.
Updated firmware key generation support through 22.1.0.
Bumped displayed/application version to 1.0.3.
Moved the screenshot saved/failed notification below the footer controls so it no longer overlaps the “Return to Hekate” option.

v1.0.2

Bug Fixes
- Fixed firmware version incorrectly displaying as 1.0.0 when NCA detection fails
- Firmware and Required Fuses now display N/A instead of a misleading version when detection fails
Improvements
- Added new STATUS: FIRMWARE NOT DETECTED state when the database is loaded but the firmware NCA hash is not found
- When firmware is not detected, users are now directed to check for an updated build at github.com/sthetix/FuseCheck
- Added console Serial Number display (read from PRODINFO)
- Added Console Type display (Erista - Icosa (V1), Mariko - Iowa (V2), Mariko - Hoag (Lite), Mariko - Aula (OLED))

v1.0.1

Added warning when fusecheck_db.txt is missing instead of showing misleading firmware version 1.0.0.
Users are now properly informed when config folder is not copied to SD card.
Improved user feedback for missing database file.

v1.0

First Release.

Credits

This project combines work from multiple excellent Switch projects:

CTCaer - Hekate bootloader, BDK libraries, hardware initialization
shchmue - Original Lockpick_RCM, key derivation engine
THZoria - Lockpick_RCMaster base
TegraExplorer - Horizontal UI design inspiration
switchbrew.org - Fuse documentation and mapping
ReSwitched community - Research, documentation, and support

Special thanks to CTCaer for excellent documentation and reusable code architecture.

External links