ControlLogix Major Fault Type 1 Code 1 (Power-Up): Causes and Fix

Q: What causes Rockwell Automation / Allen-Bradley ControlLogix / CompactLogix (Logix 5000) fault T01:C01?

1. Supply interruption while in Run, with a Power-Up Handler that does not clear the fault: Compare the fault timestamp with plant power records; open the Power-Up Handler in the program export. 2. Intentional design: the plant chose not to restart automatically after power loss: Confirm with the controls owner whether automatic restart after power loss is allowed for this machine. 3. Unstable controller or chassis supply: Measure the controller/chassis supply and check the power supply module and its input.

The controller was powered up while in Run (or Remote Run) mode. Rockwell’s corrective action is to execute the Power-Up Handler. If the Power-Up Handler is empty, the controller stays in the faulted state after power is restored instead of returning to Run; if the handler clears Type 1 Code 1, the controller runs the handler logic and then resumes normal operation.

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 after a supply loss while the controller was in Run or Remote Run
After a planned power cycle with the key switch in RUN

Likely causes and checks

1Supply interruption while in Run, with a Power-Up Handler that does not clear the fault

Points to it: Fault time matches a power event; Power-Up Handler program exists but is empty or does not clear T01:C01.
Check: Compare the fault timestamp with plant power records; open the Power-Up Handler in the program export.

2Intentional design: the plant chose not to restart automatically after power loss

Points to it: Power-Up Handler deliberately left empty; site procedure requires a manual restart.
Check: Confirm with the controls owner whether automatic restart after power loss is allowed for this machine.

3Unstable controller or chassis supply

Points to it: T01:C01 repeats without a known plant outage; other devices on the same supply reset too.
Check: Measure the controller/chassis supply and check the power supply module and its input.

Telling it apart

T01:C01 says only that power returned in Run mode; the reason power was lost is outside the controller, so look at the supply first.
If the controller lost the program as well, look for T01:C40 (battery/ESM could not save the program on power-down) instead.
A fault that clears and returns to Run without intervention means the Power-Up Handler is clearing it; check that its logic brings the machine to a safe state before resuming.

Evidence to collect

Major Faults tab screenshot with timestamp
Plant power or UPS event log at that time
Power-Up Handler program and routine from the program export
Controller supply voltage measurement

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Rockwell Automation / Allen-Bradley ControlLogix / CompactLogix (Logix 5000) fault T01:C01: Power-up fault: power lost and restored in RUN mode