ControlLogix T01:C01 after power loss, what to check first?
My ControlLogix controller faulted with T01:C01 after a power bump on the machine. The RUN indicator is off and it won't restart automatically. What should I investigate first?
A Type 1 Code 1 (T01:C01) fault on a ControlLogix controller indicates that the controller powered up in Run or Remote Run mode after a power loss. This fault prevents the controller from automatically returning to normal operation if its Power-Up Handler is not configured to clear it. The primary cause is often an external power interruption.
Likely causes and checks
1Supply interruption while in Run mode, with an unconfigured Power-Up Handler
- Points to it
- The controller lost power while it was in Run or Remote Run mode. When power was restored, the controller attempted to resume operation but encountered the T01:C01 fault because its Power-Up Handler routine was either empty or did not contain logic to clear this specific fault.
- Check
- Compare the fault timestamp with plant power records to confirm a power event. Then, open the Power-Up Handler in the program export to see if it exists and if it contains logic to clear T01:C01.
2Intentional design choice to prevent automatic restart
- Points to it
- The system may be deliberately configured not to restart automatically after a power loss. This is often a safety or operational decision, where a manual restart procedure is required after any power interruption.
- Check
- Confirm with the controls owner or relevant personnel whether automatic restart after a power loss is permitted or desired for this specific machine or process.
3Unstable controller or chassis power supply
- Points to it
- Fluctuations or instability in the power supply to the controller or its chassis can cause unexpected power cycles, leading to the T01:C01 fault without a clear external power outage.
- Check
- Measure the input voltage to the controller/chassis power supply module. Also, check the power supply module itself for any diagnostic indicators or signs of malfunction.
Next check: First, verify if the fault timestamp correlates with any known power events in the plant. If so, examine the controller's Power-Up Handler routine to see if it's designed to clear T01:C01. If not, investigate the stability of the controller's power supply.
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