PLC Fault Code????


Thread Starter


Fault code 5A in unknown slot stopping our process several times a week. What is fault code 5A "Hardware Inturrupt Problem". The 1F preceeding it states that the slot is unknown. I cannot find any documentation on this fault, what causes it, or how to resolve our problem. Thanks for any help in advance
"Our AB SLC 5/04 faults with 1F5A "
Sorry, I only included the processor MFG / Model
in the question description.

Larry Lawver


I'm guessing that you are having this problem with an Allen-Bradley SLC500, because your information is consistent with the error code system in that product. Please send me your processor file(s), in any format convenient
to you, and I'll take a look at them.

Hope this helps!

Larry Lawver
Rexel / Central Florida
[email protected]


What brand of PLC?

If AB, check the processor status on the error page, and see if there is any consistency in which rung/program file it crashes on. This may provide a clue. Depending on your program, you may be able to play with the slot disabling, etc. to try to isolate which slot it is in. What specialty modules are you using? Typically they will be the culprit more than just a plain digital I/O module.

Try replacing modules, one at a time, and see if the problem goes away. Try swapping the modules with ones from a different machine. See if the
problem moves to the other machine. If not, replace the backplane.

Swap out the processor if all else fails.

Trying to isolate which module is faulty will go a long way towards solving
your trouble.

--Joe Jansen

Barb, Manufacturing Programmer, Hewlett-

A SLC 5/04 is an Allen-Bradley PLC.

1F5A (unknown slot, hardware interrupt problem) implies something wrong with the controller itself. Or, some intermittent condition happens that the firmware can't handle?. (Normally things that cause faults in this word, S:6, are conditions which prevent the controller from ever running at all.)

What is connected to this SLC5/04? What modules are in the rack? What other controllers/PCs might it be communicating with, and how-- DH+? Ethernet? Serial?