5/04 fault

I have a slc 5/04 that will throw a fault occasionally, like once a week or two. When I get online with it and go to error it says check slot two, which is 1746-IA16 input card. I have changed the card out and it still does the same thing. Is there a way I can pin point the root cause of this fault without digging into everything that comes off that card? I guess I am at a stand still without knowing what is causing this. Seems like a pretty vague description.

I'd start by individually fusing every input on the troublesome 1746-IA16 module; 500mA each should be plenty.
You might be able to locate the culprit unless you have a faulty chassis.

On rare occasions, the SLC CPU will mis-identify the card causing the fault, and it will usually be one adjacent to it that is actually causing the problem. If an adjacent output module is suspect, the module itself may not be to blame, noise from inductive loads or faulty devices or wiring can get to the backplane especially with relay output cards.

As OkiePC says, surge protection across all inductive loads. Especially if you use the same power for your input module as you do any output modules.

Power Supply

It may not be the module itself but rather the power supply to the modules. If the quality of the power supply has deteriorated it will give these types of faults. It took many hours of troubleshooting and part replacements and wasn't a fun lesson to learn.

You have any OW16 cards in there. I had a problem years ago with series B cards I think it was where I would get random controller faults. Replaced all the cards on a Tech Note and everything was fine.