350

Serial Pulse Coder is Abnormal

Fanuc · Series 20 CNC

What does 350 mean?

This alarm indicates an abnormal condition or communication error with a serial pulse coder (encoder) connected to the Fanuc Series 20 CNC. Serial pulse coders communicate digital position data over a serial link, and this alarm signifies a disruption or corruption of that data.

Common Causes

  • Loose or damaged serial communication cable between the pulse coder and the servo amplifier.
  • Electrical noise interfering with the serial data transmission.
  • Malfunction of the serial pulse coder itself.
  • Faulty serial interface on the servo amplifier.
  • Incorrect parameter settings for the serial pulse coder.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Inspect the serial pulse coder cable for physical damage, loose connections, or improper shielding.

  2. 2

    Verify proper termination of the serial communication line if applicable.

  3. 3

    Check for sources of electromagnetic interference (EMI) near the cable runs and ensure proper grounding.

  4. 4

    Examine diagnostic data related to the serial pulse coder for specific error sub-codes or communication status.

  5. 5

    Temporarily swap the suspected pulse coder or servo amplifier with a known good one if feasible to isolate the fault.

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

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