Fanuc 0i Error Code APC 301

Fanuc CNC Major APC Alarm

Model: FANUC Series 0i / 0i Mate (APC) | Code: APC 301

Applicable Systems
Series 0i Series 16/18/21 Alpha Beta

Symptoms

A communication error occurred with the absolute pulse coder. APC alarm APC 301 is displayed.

Possible Causes

  • Absolute pulse coder battery depleted
  • APC cable disconnected or damaged
  • APC module internal failure
  • Origin position not set after battery replacement

Troubleshooting Steps

  1. Step 1: Check the APC battery voltage for the affected axis when alarm APC 301 appears
    Battery voltage above 3.0V; if below, replace battery
  2. Step 2: Inspect APC cable and connector at the servo motor
    Cable intact, connector properly seated
  3. Step 3: If battery was replaced, perform origin return procedure for the affected axis
    Axis origin set successfully, alarm clears
  4. Step 4: If alarm persists, the APC module or pulse coder may need replacement
    Fault confirmed by FANUC servo system diagnosis

How to Reset

Replace the APC battery if low, perform origin return after battery replacement. For cable or module faults, inspect and replace as needed, then clear with RESET.

Common Replacement Parts

  • A02B-0309-C: APC battery unit (3.6V lithium) (Replace before battery fully discharges to prevent position loss)

Frequently Asked Questions

  • Q: What does Fanuc APC alarm 301 mean?

    APC Communication Error: A communication error occurred with the absolute pulse coder.

  • Q: How do I fix APC alarms?

    Check and replace the APC battery if low. After battery replacement, perform the origin return (dog-less or with dog) procedure. If the alarm persists, check the APC cable and connector.

Related Fanuc Fault Codes

Source: Fanuc 0i/0iMate APC Alarm Code List, FANUC Corporation

Category: CNC