hotdawwg

Hey guys, my 1999 LS400 has flipped over to 264k. I have the oh so common P0420 Trouble Code and I am confident that my cat(s) are going. The main reason is the crazy amount of heat that comes off the exhaust when idling. Any ways, I am in the market to replace the cats but don't know where to buy them from. I live in California, so being a CARB state, it is a bit of a challenge to find a good replacement that will last more than a year that are CARB Compliant. What are your recommendations my fellow UCF owners?

1on1

I doubt you need a new cat since this is a common issue. Go to oreilly's, autozone, or winchester auto parts and pick-up the O2 sensor spacer. Catalytic converters is a hardware item and are not controlled electronically. What monitors the readings are the O2 sensors. Please view the following video below and this helped my buddy pass smog as he thought he needed to purchase two catalytic converters. **Remember to reset the ECU by pulling the EFI fuse or unhook the battery**

Worse case scenario, you can purchase new O2 sensors.

PureDrifter

iTrader: (10)

1. exhaust leaks
2. failing o2 sensors


If you have trouble passing the CA smog test due to high HC or CO then consider a new set of cats.

hotdawwg

So, what if I need to take the next step to buy cats, any recommendations?

1on1

I would suggest going to your local auto parts store to purchase the correct catalytic converter. The carb number on the cat needs to match the year of your car. For example, I had a buddy who purchased california cats online. The car passes smog but due to the carb number on the cat didn't match his year, he failed the test (The cats are for 95+ ls400 and he owns a 91).

wnyjazz

Very happy with the 2 Magnaflow cats I bought.

timmy0tool

iTrader: (7)

if I were in your shoes, I would use car-part.com and try to source a used set that way. not sure how easy it is to buy used cats in the cali market as cars I see at the junkyard had their cats removed already. trying to have a muffler shop weld in a set of aftermarket cats will not only be expensive but will not guarantee a pass. with OE stuff, despite used, it's less likely to be refuted by a smog shop.

of course take care of defective O2 sensors and any leaks.

jaaa

Have you made sure it isn't leaking past the top of the driver side cat(at the flage where the y pipe mates to the back of the cat). I had same code as you and it was just an air leak. A $5 can of VersaChem Weld repair and sealer fixed mine in no time.

PureDrifter

iTrader: (10)

IF you need cats then start emptying your wallet. The factory cats are very expensive, aftermarket cats for the CA market have to be CARB legal for that exact model, so don't come cheap. 49-state cats won't pass smog (on the visual) as they won't be stamped with the right EO number.

spuds

So you had the same ones as Calif? And they welded them in and no problems at smog test? also did you get the 444005 or 444006,was there a difference,were yours marked in any way the ones you replaced?
https://www.ebay.com/itm/Magnaflow-4...5aZuDV&vxp=mtr

Sherl

Any developments on this? Appears mine is at 230k and would swap Cats before they start stressing my engine. Mine is CA as well.

Sin1UZFE

Are they on junkyard ones? or look at someone parting out they might have it.

Sherl

Is junkyard cats any good? Read since they are like consumables, they are prone to fail as well. I was looking into magnaflow and they are 350 total but no reviews for CA cats.

Sin1UZFE

Ive used one on an old escort I had, didnt have problems with it. If it saves me $1000 I think its a risk well worth it.

But I wanna say california signed a law mandating removal or at least no selling them from junkyards. Thats why I recommended seeing if someone is parting out their LS.

timmy0tool

iTrader: (7)

correct! junkyards cannot sell you used cats.
people were snagging them just for the precious metals inside (like platinum).

aftermarket CA cats need to be stamped with an EO number or they will not pass the visual test, though not all shops care to do the visual.

this part needs to be welded to work but it has the right EO number stamped right on the side of the unit that matches the car.
https://www.magnaflow.com/products?partNumber=444005