MewTools MAKCU and FERRUM errors (MT-401 to MT-408) and fixes

These are the error codes MewTools shows on the MAKCU and FERRUM screen. Find the code or the message the app gave you, and the fix is under it. Words in curly brackets, like {name}, get filled in by the app with your details.

The full setup for each device is in MAKCU setup and FERRUM setup.

MT-401: No MAKCU found.

The app doesn't see a MAKCU on any port.

• Plug the MAKCU in.
• Check the CH343 driver on the Drivers screen. If it's missing, see MT-204.
• MAKCU not showing a COM port has the rest.

MT-402: No FERRUM found.

The app doesn't see a FERRUM.

• Plug in the FERRUM.
• Click Find devices on the MAKCU and FERRUM screen.
• FERRUM not showing a COM port has the rest.

MT-403: {port} is 10 or higher. Some tools can't open it.

Some tools only open COM1 to COM9.

• Follow the steps the app shows to move it to a free port below 10 in Device Manager.
• Then set the new number in your software. COM port number is 10 or higher has the same steps.

MT-404: {port} is busy. Close other apps that use it.

Only one program can have a COM port open at a time.

• Close other tools that talk to the device.
• Try again.

MT-405: The device did not answer like a MAKCU or FERRUM.

Something answered on that port, but not the way a MAKCU or FERRUM does.

• Check you picked the right port.
• Unplug the device and plug it back in.
• Close other tools that use it.

MT-406: The cursor didn't move.

The test sent a move and the cursor stayed put.

• Make sure the device is plugged into this PC.
• Make sure your mouse is plugged into the device.
• Try again. More on this in mouse not passing through.

MT-407: The MAKCU firmware flash failed.

The MAKCU flash stopped before it was done.

• Start the steps again from step 1.
• Use the cables that came with the MAKCU.

MT-408: This is not a MAKCU firmware file.

The file you picked isn't MAKCU firmware.

• Download the firmware again from makcu.com.
• Pick the .bin file.

Still stuck

Open a ticket in our Discord (how to open one) and paste the summary MewTools gives you, so we can see what it saw.