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ErrorLib — Industrial Fault Code Library

Disclaimer: ErrorLib is an independent technical reference tool. While we aim for accuracy, always verify with the manufacturer’s official service manuals before performing maintenance on industrial equipment. ErrorLib is not affiliated with the brands listed.

W 

Watchdog Timer Error

Mitsubishi Electric · MELSEC iQ-R Motion Controller

What does W  mean?

This error indicates a watchdog timer fault, where the system's watchdog mechanism has not been reset within its expected interval. This typically points to a software malfunction or an unresponsive process within the Motion CPU module, or a hardware error.

Common Causes

  • Software malfunction causing the watchdog timer to expire
  • Unresponsive process within the Motion CPU module
  • Hardware error impacting watchdog timer operation

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Check the error cause with 'Motion CPU WDT error cause (SD512)' using MT Developer2 to diagnose the specific watchdog error.

  2. 2

    Remove the identified error cause (e.g., correct program logic, optimize processing).

Browse all codes in this manual (19)
Verified technical data. Last updated: April 2026

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Source: Mitsubishi Electric MELSEC iQ-R Motion Controller
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