304

Serial Pulse Coder Mispulse Alarm (PMAL)

Fanuc · Alpha i series AC Servo Motor

What does 304 mean?

A mispulse alarm (PMAL) was detected for the serial pulse coder, indicating that the coder is generating incorrect or spurious pulses. This typically points to an internal fault within the pulse coder.

Common Causes

  • Generation of mispulses by the serial pulse coder.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Turn the main power OFF.

  2. 2

    If this alarm recurs immediately when power is reapplied, replace the motor (which contains the pulse coder).

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Verified technical data. Last updated: March 2026

Related Faults

Source: Fanuc Alpha i series AC Servo Motor