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ErrorLib — Industrial Fault Code Library

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A402.02

Special I/O Unit Setting Error

Omron · SYSMAC CJ2 CPU Unit

What does A402.02 mean?

This fault indicates a setting error for a Special I/O Unit. When a Special I/O Unit Setting Error occurs, A402.02 and the bit in A428 to A433 corresponding to the Unit's unit number (0-95) are turned ON. The CPU Unit will continue operating, and the ERR/ALM indicator on the front of the CPU Unit will flash. These flags are refreshed when power is turned ON or I/O is recognized.

Common Causes

  • Incorrect configuration parameters or settings for a Special I/O Unit (e.g., I/O table, PLC Setup).
  • Mismatched hardware or software settings for the Special I/O Unit.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Identify the specific Special I/O Unit with the setting error by checking bits A428.00 to A433.15.

  2. 2

    Compare the configured settings for the identified Special I/O Unit in the CX-Programmer with the actual hardware.

  3. 3

    Reconfigure the Special I/O Unit settings to match the expected parameters.

  4. 4

    Cycle power or re-recognize I/O to refresh the status after correcting settings.

Browse all codes in this manual (27)
Verified technical data. Last updated: April 2026

Related Faults

A10101Synchronous Input Data Refresh ErrorA259.12Task ErrorA295.09Indirect DM/EM Addressing Error
Source: Omron SYSMAC CJ2 CPU Unit
Open Manual (Page 628)Search more codes in this manual