Controllogix major fault after power out

[MrQ]

Hello,

My Controllogix PLC stops with a major fault after cycling of power. Why?

 

[Ken Roach]

After the power cycle, go online with the controller and open the Controller Properties dialog box. There will be information in the Major Faults tab about what has caused the most recent and the current Major Fault.

The most common reason for a major fault after a power cycle is that the memory backup battery is low, and the user program is erased on power cycle.

But there are dozens of other fault codes that are possible, so check the Major Faults tab.

 

[Steve Etter]

Another reason I have seen is having devices in your I/O configuration set to "Major Fault On Controller If Connection Fails While in Run Mode". Depending on the device, it may take longer to power-up than the processor and, thereby, cause a fault condition. Obviously some devices need to be set this way, but others may not.

 

[MrQ]

Fault codes:

(Type 01) Power-up Fault
(Code 01) Power lost and restored in RUN mode

 

[Ken Roach]

That's very useful information !

This is one of the things the Power Up Handler does.

If you define a Power Up Handler routine, the controller automatically faults with a Type 1 Code 1 fault on powerup. This places the system in a harmless fault mode until the powerup handler is complete and the Type 1 code 1 fault has been reset.

The Type 1 Code 1 fault can be reset with an SSV (Set System Variable) instruction.

There's a good example of this in the RA Knowledgebase (TechConnect Required): https://rockwellautomation.custhelp.com/app/answers/detail/a_id/27931

If you aren't using the Power Up Handler for any other purpose, you can just delete it and change the Controller Properties entry for the Power Up Handler to 'None'. The fault will no longer occur.