GRBL error codes
What error:N and alarm:N mean, and how to clear them.
You see
The Console panel shows error:N or alarm:N where N is a number. The machine refuses to move (alarm) or refused to accept a specific command (error).
What is happening
GRBL has structured error and alarm responses. The number is a code that names the exact thing that went wrong.
Common error codes
| Code | Meaning | Common fix |
|---|---|---|
error:1 | Expected command letter | Bad G-code syntax. Usually a Beam Bench bug, report it. |
error:2 | Bad number format | Same. |
error:3 | Invalid $ command | Send a valid $ command. |
error:9 | G-code locked out during alarm | Clear the alarm first ($X or Unlock in the Move panel). |
error:15 | Travel exceeds soft limit | The commanded move goes outside the machine's bed (per $130-$132). Check your project size and machine bed dimensions. |
error:20 | Unsupported command | The firmware does not know that G-code. Use a Beam Bench-supported subset. |
error:22 | Feed rate not set | The first move had no F value. Usually a Beam Bench bug, report it. |
error:24 | Move with no Y | Same. |
Common alarm codes
| Code | Meaning | Common fix |
|---|---|---|
alarm:1 | Hard limit triggered | A limit switch was hit. Move the head away manually, then Unlock. |
alarm:2 | G-code motion target exceeds machine travel | The job ran past the bed boundary. Reframe within bounds. |
alarm:3 | Reset while in motion | Soft reset happened mid-move. Position is uncertain, home before continuing. |
alarm:8 | Homing failed: pull-off travel failed to clear switch | A limit switch is stuck or wired wrong. Inspect switches. |
alarm:9 | Homing failed: could not find limit switch | The head did not reach a limit switch within the homing distance. Check switch wiring, homing direction ($23), and that $132 is set correctly. |
Fix
Clear an alarm
In the Move panel, click Unlock when the machine is in alarm state. This sends $X to GRBL.
Or send $X manually in the Console panel.
After unlocking, home before running anything. The machine no longer trusts its position.
Find the full meaning of a code you do not see above
GRBL's source documents every error and alarm code. Search "GRBL error codes" online for the full reference for your firmware version.
Repeated alarms during normal use
Suggests a mechanical or wiring issue: limit switch failing, soft-limits set wrong, motor stalling and the controller noticing.
Still stuck?
- Connection Diagnostics panel: recent traffic and events.
- Console panel: send
$$for current settings. - GRBL essentials: concept review.
- Dollar settings reference.
- Post in the Facebook group with the exact code and the recent log.