Intermittent CAT converter light

183k miles and CAT light occasionally turns on. Off now and has been for several weeks.
Should I let well enough alone or start using Cataclean or equivalent? Is there any way such products can make matters worse?
Thank you! (2015 Santa Fe)

What are you calling the CAT light? The little engine symbol? That is not a CAT light, it is a general error light that shows when a problem is identified.

It sets error codes that can be read with a scan tool. If it was a catalytic convertor failure code, it should be a P0420 or P0430. Have you had the codes read, and what exact code did you get? Post them here, please.

And it is unlikely Cataclean will do anything. Can’t hurt to try but don’t expect miracles in a bottle.

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There were some cars that had catalytic converter temperature warning lights!

A 2012 Ford Fusion has a catalytic converter temperature sensor!

Faulty recollection. When part of the CC failed previously, it triggered the “engine” light and at the time a PO420 code was read. I equated the two, but I now remember I was corrected by the tech.
Since the engine light is now off, I obviously won’t get a code so no point in checking. Will check when it happens.
Even though the CC may not have been the reason for the light, at least I have your opinion about Cataclean and similar products. Not really surprised.

I don’t find such a light listed for my vehicle. Thanks.

A bad cat SETS the check engine light. If it goes away, it no longer detects that problem. Don’t worry until it comes back. I have had a P0420 in my Mustang. I cleared it. It did not come back. Maybe it will eventually but I am fine now.

Unless you live in a state that checks emissions, it generally won’t affect the performance of the engine. It will fail you during an emission test, however.

That’s not true. Check the code.

This can be done if your scanner/code reader is capable of retrieving pending codes.

Otherwise, you won’t get a code with the check Engine light off.


When what you believe to be a dashboard light cat-warning turned on and off briefly, were you driving in a way that put an unusual burden on the engine, like going up a steep hill, or long periods of stop and go driving & idling? If not, and this warning occurred for no apparent reason, just during a routine drive, your cat is probably near the end of its lifespan. A shop with the proper equipment could compare the pre-cat and post-cat O2 signals and from that give you an idea is your cat should be replaced proactively.

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Turns out the light wasn’t CAT specific, just a general engine warning light, so the problem could have been anything.

Whenever the check engine light turns on, there will be a diagnostic code stored in computer memory. So next time it turns on, take your Santa Fe to your shop immediately and ask them to read the diagnostic codes. They will usually start with a “P” followed by a 4 digit number; e.g. P0430. If you post the code(s) here, you’ll likely get some more ideas.


Take it to a parts store like AutoZone, NAPA, or OReilly. THey will read the code for free. It might not be the cat as MANY things can cause a check engine light. There may be a “pending code” which isn’t on enough to trigger a light just yet. If a pending code, you will get a result but the light won’t be on.