Catalytic converter

In order to reason objectively, the detected error code is necessary.

A constantly lit check engine light is dangerous because you get used to it and can miss a serious problem.

 

You can't damage the valves, if the car is running rich. You can fry the CAT if it's running rich or you have excessive oil burn. We can't see, smell, or hear the car over the internet, that's why we're asking for error codes.

There's a communications issue here. Either you misunderstood what the mechanic told you or the mechanic is full of CRAP. As I explained above. There's several ways to kill a new CAT or that CAT was defective. That's why we ask for the error codes. A good, professional repair shop would've checked for those other issues, before installing a new CAT; because they need to warranty their work. If a customer drags in their own part and tells them to just replace this. That's all they're going to do. The only warranty your going to get is that it won't fall out of the car.

@MAX2 stated; if another fatal issue crops up; you won't know, until the car just stops running - since your CEL is already lit.

 

Those P-codes are what we need to do a remote diagnostic. Anyone can say what they think the problem is (ie. low cat efficiency - P0420); but that's their interpretation of that code. Was there any other codes the car kicked out? A lot of us with experience fixing cars, can tell you the most likely part failures, when you give us a bunch of error codes the ECU kicked out. But when you tell us your mechanic thinks is this - what do you want us to say?

Price has nothing to do with it. Both Amazon and E-bay are flooded with counterfeited parts. If your car is running correctly, it shouldn't have destroyed the CAT. Figure out what the warranty is on that part, normally 2 years or 24K miles - but you'll need to prove that it was installed correctly and the car was also running correctly. If you had a repair shop sell you the entire job, they would be on the hook for the warranty repair.
Catalytic Converter Warranty: Owners' Peace of Mind

Good Luck.....

 

I replaced mine about 4 years ago with a similar aftermarket cat. It lasted about 13 months before the P0420 code. I then installed a spacer on the same aftermarket cat and went another 2 years until I recently got some other codes (P0606 and P0137). Based on some research/guessing, I replaced the cat with another aftermarket cat and also switched out the downstream O2 sensor. It's been about 300 miles and the codes have yet to return. I'll be happy if this cat gets me through the next two emissions test.

 

Congrats on passing smog for an additional two years; but if that smog station saw that spacer - that would've been an automatic failure. That wasn't a fix, you simply took the sensor out of the exhaust gas flow stream. (ie. fooled the ECU, but it eventually figured it out.)

YMMV

 

Yes, I'm well aware of what the spacer does. Of course, after replacing the cat, I no longer have the sensor attached but I'll do it again when this latest cat fails... worth the risk for me. I've never dropped under 46 mpg and the car runs well.

 

I always thought when comparing a $150 replacement to the $1700 original, that it was surprising that the aftermarket worked at all. I think 1 year of trouble free service is reasonable to expect for these cheaper parts.
In my mind it was enough to get me through emissions for another two years and if i had to replace it again in two years, so be it. Of course i am not paying labor for these.
The aftermarket must provide just enough to rare metals to make it work... whatever chemical reaction happens, it will slowly reduce its effectiveness over time... The OEM part was well equipped to handle the conditions but the aftermarket... should be no surprise it has such a short life.
I always believed that code said it was not meeting the expected efficiency, not that it wasn't working at all. Just old and tired. This may have some change to the way the engine runs, but I don't know that I would be that concerned.

I hate the check engine lights being on, but if you have a bluetooth OBDii reader and an app on your phone you can periodically check that there are no other codes for peace of mind.

The last prius I had with an aftermarket cat got great mileage... a trip from NJ to Ohio had me up around 49 MPG. I wonder if that aftermarket cat might have helped with lower back pressure or something... who knows. After that car I had one with the OEM unit and i was lucky to see 45 MPG. It did have 275K miles and burned some oil... also a big factor.