FluidNC Error 1

FluidNCErrorPosition is kept

The controller got a line that isn't proper G-code: something without a letter, or a stray character.

Position is kept. An error means the controller refused that one line or command, so nothing moved for it. (Hamrun's reading)
What to do
  1. Open the file and look at the line it stopped on for stray characters, comments without brackets, or text from another program.
  2. Check the post-processor matches your controller.
Official FluidNC message: “Expected GCodecommand letter” source

Got a different message?

Paste it into the decoder. Hamrun's editor checks your G-code before you run it, so a toolpath that leaves the machine's travel or a missing feed rate is caught before the machine stops.

Related codes

  • GRBL 1.1 Error 1: The controller got a line that isn't proper G-code: something without a letter, or a stray character.
  • grblHAL Error 1: The controller got a line that isn't proper G-code: something without a letter, or a stray character.

Official text copied from the FluidNC source on 2026-11-01. Steps and the position answer are Hamrun's reading unless marked “firmware says”. User reports are labelled CLAIMED.