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: March 2026

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Source: Mitsubishi Electric MELSEC iQ-R Motion Controller