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ErrorLib — Industrial Fault Code Library

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2128

Redundant System Extension Base Unit Unusable Module

Mitsubishi Electric · MELSEC System Q/L Series

What does 2128 mean?

This error indicates that an unusable module is mounted on an extension base unit within a redundant system (QnPRH with serial No. 09012 or later). This suggests an incompatibility or an incorrect module type for the specific redundant system configuration. The error is detected at power ON or during a reset, causing the CPU to stop.

Common Causes

  • An incompatible or unusable module is physically installed on the extension base unit in a QnPRH redundant system.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Physically remove the unusable module from the extension base unit.

  2. 2

    Verify that all modules installed on the extension base unit are compatible and applicable for the QnPRH redundant system.

Browse all codes in this manual (53)
Verified technical data. Last updated: April 2026

Related Faults

1000CPU Down Error1001CPU Down Error with Device Access Issue1002CPU Down Error
Source: Mitsubishi Electric MELSEC System Q/L Series
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