GRBL Errors and Alarms: Read the Console Before You Unlock Anything

Why this matters

Treat GRBL alarm/error numbers as diagnostic messages and fix the cause instead of reflexively clearing the controller state.

How it works

• GRBL alarms indicate serious machine states; error codes indicate commands the controller cannot act on.
• ALARM:1 can follow a limit trigger and often requires rehoming because position may be lost.
• ALARM:2 indicates motion outside known workspace and can be caused by job size, Start From/Origin choices, rotary limits or configuration.
• Error:5 commonly appears when LightBurn requests homing but homing is not enabled/configured.

Practical workflow

1. Record the exact ALARM:# or error:# before doing anything.
2. Match the code to the LightBurn/GRBL explanation.
3. Check the physical machine state, coordinates and recent workflow change.
4. Correct the cause, then rehome/recover in the controller-appropriate way.
5. Repeat a low-risk Frame or jog test before returning to production.

What to watch for

• $X can unlock some states but does not restore lost position or fix incorrect configuration.