grblHAL Alarm 4

grblHALAlarmPosition is kept

The probe already looked touched (or untouched, for a probe-away move) before probing even started.

Position is kept. The probe cycle stopped before moving. (Hamrun's reading)
What to do
  1. Check the probe isn't already touching: the clip on the bit and the plate under it shouldn't meet before the move.
  2. Touch the clip to the plate by hand and see whether your sender's probe light changes. If it's always on, the probe input is inverted ($6) or the wire is shorted.
  3. Unlock and try the probe again.
Official grblHAL message: “Probe fail. Probe is not in the expected initial state before starting probe cycle when G38.2 and G38.3 is not triggered and G38.4 and G38.5 is triggered.” 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 Alarm 4: The probe already looked touched (or untouched, for a probe-away move) before probing even started.
  • FluidNC Alarm 4: The probe already looked touched (or untouched, for a probe-away move) before probing even started.

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.