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ErrorLib — Industrial Fault Code Library

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Alarm 2

Software Disconnection (Closed Loop)

Fanuc · Alpha i Series Servo Amplifier

What does Alarm 2 mean?

This alarm is issued when the change in position feedback pulses is relatively small for the change in velocity feedback pulses. This condition typically occurs in a closed-loop system and is not issued with the semi-closed loop.

Common Causes

  • The closed-loop control system has lost its feedback signal.
  • Software error preventing the system from establishing a closed loop.
  • Encoder or sensor is not providing valid position data.
  • Communication failure with the position feedback device.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Check whether the separate detector outputs position feedback pulses correctly.

  2. 2

    If the detector outputs pulses correctly, investigate for a large backlash between the motor position and scale position causing reverse rotation of only the motor at the start of machine operation.

Browse all codes in this manual (101)
Verified technical data. Last updated: April 2026

Related Faults

0233Velocity Pulse Count Exceeded0243Position Pulse Count Exceeded0434Velocity Loop Integral Gain Overflow
Source: Fanuc Alpha i Series Servo Amplifier
Open Manual (Page 45)Search more codes in this manual