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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.

E.5

CPU fault

Mitsubishi Electric · FR E700

What does E.5 mean?

This is a CPU fault that stops the inverter output when a communication fault occurs within the built-in CPU. Such an error indicates a critical internal processing issue, which can be influenced by external factors like electrical noise. Inverter operation is halted to prevent further damage or incorrect control.

Common Causes

  • Internal data bus communication error within the CPU or between the CPU and peripheral chips.
  • Instability of internal clock signals critical for CPU operation due to component drift or noise.
  • Insufficient or fluctuating internal power supply voltage to the CPU and associated circuitry.
  • Faulty firmware executing an illegal instruction or entering an infinite loop.
  • Excessive ambient temperature causing thermal stress on CPU components.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Power cycle the inverter by disconnecting all input power for a minimum of 60 seconds to ensure a full reset of all internal logic.

  2. 2

    Ensure the inverter's operating environment is within specified temperature limits (e.g., 0-50°C) and that cooling fans are operational.

  3. 3

    Measure the stability of the 24VDC control power supply at designated terminals (e.g., PC/P24) to ensure it is constant.

  4. 4

    Check for any external sources of electromagnetic interference (EMI) near the inverter's control section or communication lines.

  5. 5

    Visually inspect the control circuit board for any physical damage, discoloration, or loose connections.

Browse all codes in this manual (26)
Verified technical data. Last updated: April 2026

Related Faults

E. 1Option faultE.13Internal circuit faultE.6CPU fault
Source: FR E700
View Official PDFSearch more codes in this manual