ControlLogix Major Fault Type 4 Code 83 (Value Out of Range)

Q: What causes Rockwell Automation / Allen-Bradley ControlLogix / CompactLogix (Logix 5000) fault T04:C83?

1. Bit index or Boolean array subscript beyond the array size: Read the index value at the fault and compare it with the BOOL array length or the bits in the data type. 2. Index calculated or entered without range checking: Limit-check the index where it is written.

The data tested was not inside the required limits. Rockwell notes that this occurs with array subscripts used with Boolean arrays and bit-level addressing. Corrective action: adjust the value to be within the valid range and do not exceed the array size or its defined dimensions.

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When it happens

In Run, when a bit index or Boolean array subscript goes out of range
At the change to Run (prescan), on controllers before revision 13

Likely causes and checks

1Bit index or Boolean array subscript beyond the array size

Points to it: Fault in logic like BoolArray[Index] or Word.[Bit] with an indirect bit number.
Check: Read the index value at the fault and compare it with the BOOL array length or the bits in the data type.

2Index calculated or entered without range checking

Points to it: Fault follows a calculation, HMI or recipe change to the index.
Check: Limit-check the index where it is written.

Telling it apart

T04:C20 covers array subscripts and CONTROL .POS/.LEN in general; T04:C83 is the out-of-range case Rockwell ties to Boolean arrays and bit-level addressing.
Like C20, it is cleared automatically during prescan from revision 13.0; outside prescan it faults the controller.

Evidence to collect

Major Faults tab screenshot
Index tag value and BOOL array size
Program export of the faulted routine
Controller firmware revision

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Rockwell Automation / Allen-Bradley ControlLogix / CompactLogix (Logix 5000) fault T04:C83: Program fault: value out of range