grblHAL Alarm 19

grblHALAlarmNot a position problem

Communication with a Modbus device (often the spindle VFD) timed out or failed.

Not a position problem. Hamrun's reading: this is about the spindle link, not motion. If the job stopped mid-cut, home before trusting position. (Hamrun's reading)
What to do
  1. Check the RS485 cable to the VFD and that the VFD is on.
  2. Check the Modbus address and speed settings match the VFD.
Official grblHAL message: “Modbus exception. Timeout or message error.” 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.

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