F018

Invalid 1771 module response

Allen-Bradley · Logix 5000

What does F018 mean?

The 1771 module responded with an invalid message or data. This indicates a communication protocol issue or a fault within the 1771 module itself.

Common Causes

  • The 1771 module response was not valid

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Inspect communication cabling between the Logix 5000 system and the 1771 module for damage, proper seating, and loose connections.

  2. 2

    Verify status indicators on the 1771 module and any associated communication adapter for fault or error indications.

  3. 3

    Measure the power supply voltage to the 1771 I/O rack or module against nominal specifications.

  4. 4

    Check the Logix 5000 controller's configuration for the 1771 module, ensuring it matches the physical module type and addressing settings (e.g., DIP switches).

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Verified technical data. Last updated: March 2026

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