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ErrorLib — Industrial Fault Code Library

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1401H

Input Dark Test Error

Mitsubishi Electric · MELSEC iQ-R I/O Module

What does 1401H mean?

During an input dark test, the module failed to detect the expected test pulses. This indicates a problem with the input dark test setup, the input wiring, the connected devices, or an unused input terminal that has not been correctly configured to be 'Not used'.

Common Causes

  • Expected test pulses were not detected during an input dark test, possibly due to wiring or device issues.
  • An unused input terminal is not correctly set to 'Not used' for 'Wiring input selection', interfering with the dark test.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    For any unused input terminals, set 'Wiring input selection' to 'Not used'.

  2. 2

    Check for the specific input terminal with the error using Input dark test error detection state (Un\G1040).

  3. 3

    Review and adjust the connected devices and wiring for the identified problematic input terminal.

Browse all codes in this manual (56)
Verified technical data. Last updated: April 2026

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Source: Mitsubishi Electric MELSEC iQ-R I/O Module
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