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SIMULTANEOUS-OUTPUT-ON

Simultaneous Output ON (Source Type)

Mitsubishi Electric · MELSEC iQ-R I/O Module

What does SIMULTANEOUS-OUTPUT-ON mean?

When one output of a transistor output (source type) module is turned on, other loads connected to different outputs simultaneously turn on. This fault arises from a non-connection or disconnection between the external power supply 0V and the common line of the load, allowing current to flow through parasitic circuits in the off-state output elements. Continuous operation under this condition can lead to module failure.

Common Causes

  • Non-connection or disconnection between the external power supply 0V and the common line of the load.
  • Current flowing through parasitic circuits within the off-state output elements of the transistor output (source type) module.
  • Incorrect wiring configuration where common lines are not properly referenced to the external power supply 0V.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Correctly connect the external power supply and the load, ensuring the 0V and common lines are securely and properly connected.

  2. 2

    To prevent further occurrences, insert diodes at each output terminal to block parasitic current paths and isolate the outputs from unintended activation.

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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