ControlLogix Major Fault Type 7 Code 42 (Revision Mismatch)

Q: What causes Rockwell Automation / Allen-Bradley ControlLogix / CompactLogix (Logix 5000) fault T07:C42?

1. Replacement controller shipped with different firmware: Read the controller firmware revision and compare it with the project revision. 2. Controller firmware changed after the card image was stored: Check the firmware history and when the card image was last stored.

Loading from nonvolatile memory failed because the firmware revision of the project in nonvolatile memory does not match the firmware revision of the controller. Rockwell’s corrective action: update the controller firmware to the same revision as the project in nonvolatile memory.

Diagnose this with AI

Upload a keypad photo, the fault history or a parameter export from your Rockwell Automation / Allen-Bradley ControlLogix / CompactLogix (Logix 5000). InduQT compares the evidence and suggests the next useful checks.

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When it happens

At power-up or on a load from the memory card
After a replacement controller with different firmware was installed

Likely causes and checks

1Replacement controller shipped with different firmware

Points to it: Fault after a controller swap; same catalog number, different firmware revision.
Check: Read the controller firmware revision and compare it with the project revision.

2Controller firmware changed after the card image was stored

Points to it: Firmware was updated but the card still holds the older project.
Check: Check the firmware history and when the card image was last stored.

Telling it apart

C42 is firmware revision only; a different controller type gives C41.

Evidence to collect

Major Faults tab screenshot
Controller firmware revision
Project revision on the card and in the site archive

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Rockwell Automation / Allen-Bradley ControlLogix / CompactLogix (Logix 5000) fault T07:C42: Nonvolatile fault: load failed, revision mismatch