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ErrorLib — Industrial Fault Code Library

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6220

Redundant System Communication/Hardware Fault

Mitsubishi Electric · MELSEC-Q/L Common Instruction

What does 6220 mean?

This code signifies various critical issues within a redundant system, including physical disconnections or faults in the tracking cable, hardware malfunctions, power interruptions, or watchdog timer errors in either the control or standby CPU. It also indicates communication timeouts, discrepancies in operating status between systems, or network faults, all of which compromise the integrity and operation of the redundant setup.

Common Causes

  • Tracking cable is disconnected or physically damaged between CPU modules.
  • Hardware fault, power-off, or reset occurred in the standby system CPU module.
  • Watchdog timer error occurred in the control system or standby system CPU module.
  • Communication time-out occurred between the control and standby system CPUs.
  • Operating status differs between the control system and standby system CPU modules or a network fault was detected by the standby system.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Inspect the tracking cable for physical damage and verify secure connections between CPU modules.

  2. 2

    Verify the power supply to the standby system CPU module and check module status indicators for hardware faults or reset conditions.

  3. 3

    Monitor the control and standby system CPU modules for watchdog timer errors via diagnostic tools or LED indicators.

  4. 4

    Verify communication parameters and network integrity between the control and standby system CPU modules.

  5. 5

    Compare the operating status of the control and standby system CPU modules. Identify and resolve any discrepancies.

Browse all codes in this manual (11)
Verified technical data. Last updated: April 2026

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Source: Mitsubishi Electric MELSEC-Q/L Common Instruction
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