Can catalytic converters be bad but not throw a CEL?

[gotaboutabuck]

Hey Jeepers,

I’m getting a rattling noise when I back off on the gas. My son and I isolated the rattle and it seems to be coming from the main/big cat just in front of the muffler - but not getting a CEL. I replaced that cat and the two mini cats with cats from Eastern about seven years ago. Checked for loose heat shields and they all seem solid. My question is: can that main cat be bad, or on its way to bad, without throwing the CEL and/or coughing up codes? Thanks for any input on this.

 

[gotaboutabuck]

BTW, the rattle is on my 2004 TJ Rubicon.

 

[Chris]

Absolutely! When mine went bad they didn’t throw a CEL for quite a while, but eventually it happened.

 

[gotaboutabuck]

That’s what I thought. Gonna replace it before I get the CEL. Thanks for following up

 

[Hunter Rich]

When I replaced mine a few weeks ago, I noticed that there isn't a sensor after the big cat. This tells me that until it causes back pressure problems affecting the two other cats you wont get a CEL.

 

[PatMc]

Yep. Mine was all broken up inside...rattling like crazy. I thought it was just the exhaust hitting the body when I bought it....went and smogged it, passed with great numbers, then a few weeks later did some work on the exhaust to get it off the body and it still rattled, so I pulled the cat out and it was mostly gone with a chunk rattling around.

 

[texvet]

Same, rattling like crazy, hard start at times, no codes at all.

 

[Steel City 06]

I had all sorts of issues (CEL, misfiring, limp mode) that suddenly went away. It turned out that one of my cats became clogged and eventually self-gutted. After that, the CEL went away until it realized there was no catalyst.