Catalytic Converters... How do they fail?

[eric_rosenwald]

Do catalytic converts go bad over a long period of time, or can they fail rapidly?

My car passed a California smog check only a week and a half ago, but I'm suspicious that it currently has a problem with the cat converter. Is it possible that they can go bad that fast?

Also... Is it possible that in some instances you might have a cat converter go bad without the ECU indicating check engine code, for whatever reason? Wouldn't a bad cat converter ultimately trigger some sort of check engine response? I'm occasionally hearing a squeaky/gurgling sound. Shouldn't something as unusual and alarming as that kind of sound trigger some kind of "check engine" code?

 

[maco33]

I just replaced the original cat. converter yesterday on my '98 CRV, the reason why it went bad was because the ign. coil failed and i keep cranking the engine not knowing that all that raw fuel was killing my cat. And still went to the parts store got some starting fluid and kept cranking the engine, thinking it was a fuel problem, a couple of weeks later after replacing the coil my CAT failed triggering the check engine light right away, so if the check engine light is not on don't worry about the cat. converter being bad, your 02 sensor will let you know when it goes bad.

 

[BlackWorksInc]

Catalytic Converters should theorectically never go bad in a properly running engine that is meeting its specifications, that being said I would say 300k+ range should be a good minimum for a catalyst under normal conditions.

There are a multitude of reasons why a catalyst could fail, many of them fuel trim and engine performance related; but if you're including DTC (Diagnostic Trouble Code) failures then I will point out that many of these "Catalyst Failures" are not even related to the catalyst at all.

If you'd like some better understanding and reading I explain catalyst diagnosis and provide links on catalyst operation in this thread:

http://www.toyota-4runner.org/4th-gen-t4rs/132953-toolbox-how-use.html#post1272379

 

[eric_rosenwald]

Catalytic Converters should theorectically never go bad in a properly running engine that is meeting its specifications, that being said I would say 300k+ range should be a good minimum for a catalyst under normal conditions.

There are a multitude of reasons why a catalyst could fail, many of them fuel trim and engine performance related; but if you're including DTC (Diagnostic Trouble Code) failures then I will point out that many of these "Catalyst Failures" are not even related to the catalyst at all.

If you'd like some better understanding and reading I explain catalyst diagnosis and provide links on catalyst operation in this thread:

http://www.toyota-4runner.org/4th-gen-t4rs/132953-toolbox-how-use.html#post1272379

Thank you so much for that link. It's incredibly useful information, and the wisest, most reasonable and rational statement on cat converters that I've come across. It made me realize that my P0420 code was truly an anomaly, and not indicative of an engine problem. The engine was well-maintained by it's previous owners. I know I lack evidence, but I get the sense that putting the 4Runner in new, 4WD off road, relatively high altitude conditions (that it had never done before) triggered it. That article really put me at ease. A few days ago I was stressing over potentially having to pay a lot for a new one!

I like the fact that you stress that the ECU gets information from sensors, and that it's important to remember that sensors can fail, too.