how to tell if catalytic converter is legit or not?

If you are not in CA or NY, that should be legal.

 

It may be a perfectly functional, used OEM Catalytic Converter. The issue (I think) in NY or CA is it's illegal to install a used Cat? That said, if you install it, and there's no warning lights, I think you're home free.

 

It won't meet your CARB inspection, no.

Last I checked, only a Cat from Toyota will pass CARB.


Aftermarket Catalytic Converter Database


Many cars are listed, but not a Prius

 

I was assuming it was aftermarket, like this:

Walker Ultra Direct-Fit Catalytic Converters 47833 - Free Shipping on Orders Over $99 at Summit Racing

If it is a Toyota cat, and you self install, you should be good.

 

Honestly it looks like a used exhaust that had its Cat stolen once and replaced. I would get it installed by muffler shop who you trust and they can tell you if its California compliant. I put money on it being ok. Story sounds legit unless you bought it for like $50. That would too good to be true.
Here is mine and its OEM from 2009. Cat never been stolen and its rounded and I think a cheap aftermarket cat has shields.
View attachment 184424
View attachment 184425

 

Take it toyota dealership maybe they can look up the cat stamp code to see if it's a legitimate cat replacement.

SM-J737T1 ?

 

He might be on the level that it's from his friend's totalled Prius, but that still leaves open the question: is it a stock cat:


On this page, it's item 1, and the part number is 17410-21500:

Exhaust Components for 2008 Toyota Prius | Toyota Parts

So I don't think what you've got is stock. Trumping that, anything, even a stock cat, that's not new, is illegal to install?

 

A stock Toyota cat from a Gen 2 will have GD4 stamped on the cat closest to the engine and EA6 stamped on the second cat. Next to each GD4 and EA6 will be a small stamped Toyota symbol. NO OTHER stampings. That is not an original Gen 2 exhaust.

Along with 2 complete OEM exhaust systems, I have a replacement "ACAT EXHAUST" cat set in the shop that has similar, but different markings as the OP. It was $130 delivered to my door from a canadian exhaust company. The OP may have a higher end version? If the part that bolts to the engine is a solid steel plate, it is definitely not a Toyota replacement. (I don't think it is, anyway)

The one I have is marked

ACAT RS4-7-030B-0303-00
EXAUST N AE 133000 0419

 

just research the numbers on the CAT to see if it's considered the one Toyota used on there cars...

 

Just because it's not OEM doesn't mean it won't pass CA emissions test. As I mentioned before get it checked out 1st and let a professional tell you the truth about your purchased. I think it would pass since it looks like it was used for a couple years and I'm sure it passed emissions then and it should pass emissions now.

SM-J737T1 ?

 

I’d respectfully disagree, at least if the Smog Check technician does the test according to the regulations.

As @JimboPalmer kindly pointed out, it’s unlawful, in California, to install anything but an original or CARB-approved aftermarket catalytic converter, and as far as I know, there are no aftermarket ones approved for Prius cars. The Smog Check procedure includes a visual inspection, described in the Smog Check Manual (PDF) starting on page 15, that is required to include the catalytic converter. If the catalytic converter doesn’t meet the requirements on page 50 of the Manual, including approval for use on vehicles of the configuration being tested, then the visual inspection, and thus the entire test, must fail.

I realize that some technicians may skip some or all of the visual inspection, and an aftermarket catalytic converter may work well enough that the car’s computers wouldn’t store any diagnostic trouble codes, so the functional test of the car’s OBD II system would pass. The actual tailpipe emissions are generally not tested on model year 2000 and later vehicles; see the Test Requirements chart on page 4 of the Manual.

 

So let's look at the concerns...

1. Does it fit? Yes, it's a direct replacement. Maybe only for 47 states, but that's most likely because small companies cannot afford the $$ needed to get CA certified, not because it doesn't work.
2. Does it work? I would imagine so. Thousands of these setups get sold and installed every year and function just fine.
3. Is it right? Based on paperwork and part numbers and serial numbers, etc? maybe not, due to lacking CA cert. Morally? I would say yes. It's not like you're jamming a straight pipe in there to make it quiet. You're trying to do what's right and putting a Prius cat system back into it. Not everyone has $2500 laying around to sink into an exhaust system just so it can have a Toyota symbol stamped on it.

Personally, I would bolt it in and roll on. If it gets failed on inspection, so be it. Then look at getting a Toyota one. I'll have 3 more OEM systems to add to my collection within the next 3 weeks. No, I don't steal them, but I did make a contact at a local salvage yard.