EL
ErrorLib
Brands
||
  1. Home
  2. Mitsubishi Electric
  3. MELSEC System Q/L Series
  4. 1040
About·Privacy·Terms

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.

1040

CPU Unit Down Error (Built-in I/O)

Mitsubishi Electric · MELSEC System Q/L Series

What does 1040 mean?

The CPU module, specifically its built-in I/O, has experienced a runaway condition or failure. This can be caused by electrical noise interference or a fundamental hardware fault within the CPU module. The condition indicates that the CPU is not operating correctly.

Common Causes

  • Runaway or failure of CPU module (built-in I/O).
  • Malfunctioning due to noise or other external reasons.
  • Hardware fault within the CPU module.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Implement noise reduction measures for the control system environment.

  2. 2

    Reset the CPU module and attempt to RUN it again.

  3. 3

    If the same error is displayed again after resetting, diagnose for a CPU module hardware fault.

Browse all codes in this manual (53)
Verified technical data. Last updated: April 2026

Related Faults

1000CPU Down Error1001CPU Down Error with Device Access Issue1002CPU Down Error
Source: Mitsubishi Electric MELSEC System Q/L Series
Open Manual (Page 1308)Search more codes in this manual