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ErrorLib — Industrial Fault Code Library

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300

Request for Reference Position Return

Fanuc · Series 20 CNC

What does 300 mean?

This alarm typically indicates that an operation requiring the machine to be at its reference (home) position was initiated before the reference return cycle was completed. It serves as a reminder or pre-alarm that homing is required.

Common Causes

  • Attempting to run an automatic program or move an axis in absolute coordinates before homing.
  • Power cycling the machine without re-establishing reference positions.
  • Machine parameters requiring explicit homing after certain events.
  • Loss of absolute position data due to battery failure or encoder issues (leading to a need for homing).

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Perform the reference position return (homing) procedure for all axes as per the machine's operational manual.

  2. 2

    Verify that the machine's battery for absolute encoders is healthy if the machine requires homing after every power cycle.

  3. 3

    Check if any recent parameter changes might have disabled automatic homing or altered homing requirements.

  4. 4

    Confirm that the absolute position data is retained after power off; if not, investigate the battery backup system or absolute encoder.

  5. 5

    Ensure the machine's control mode is set correctly for homing operation.

Browse all codes in this manual (43)
Verified technical data. Last updated: April 2026

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Source: Fanuc Series 20 CNC
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