Well, long story short make sure you replace your catalytic converters with either OEM or aftermarket with correct OEM equivalent "loads". The load refers to the amount of precious metals inside the cat.

I have been fighting catalytic efficiency codes for the last 5 month. I had this problem show up a few days after I purchased the car. Previous owner was resetting ECM to hide it. Did a lot of research, no leaks, had a shop replace cats with Magnaflow high flow cats but the loads were too small. I knew nothing about this at the time. 2,000 miles later 430 is back instead of 420. After a number of resets and about another 3,000 more miles decided to replace both post-cat 02 sensors just to be safe. Codes came back after the usual 300 miles of driving. Getting both 420 & 430 now. Reset again and as usual codes are off for another 300 miles or so. Checked many times and there were no leaks whatsoever.

So, after talking to Magnaflow and realizing that my car is a CA car even though it never spent any time in CA, they said there are only two cats that can be used on my car. The first, 444005 is the for if your car currently in CA and the other, 51004, for use outside CA. Anyway, it is quite interesting as Magnaflow shows these cats whether your car is a CA car or not. I'm wondering if there really is any difference between a CA certified LS400 or non CA certified.

Long story short, muffler shop is ordering me the correct CAT's and I will be installing them again. Hopefully never to deal with PO420 & 430 for the life of the car. I did not need new post-cat 02 sensors but I guess it did not hurt to replace them. The lesson here is make sure to replace with the correct loaded cat for smooth sailing. The cheap cats are not going to work out very well.

 

thats interesting im surprised the shop you went to didnt set you up with the correct cats! I had magnaflows installed on my car awhile back with no issues so far xD. this is great to know though for sure!

 

How can I know if my car is Cali or not ? Cause I am having P0430 on now and I live in North Jersey ...

 

catalytic converters are one of several items that I wouldn't care to ever use aftermarket, the original Toyota cats are fantastic, do not hurt performance or gas mileage, and are very often misdiagnosed when not the problem, and when they are removed, it always seems to result in a sad tale of woe.

 

code P0430 is rarely ever a bad cat on an LS400, unless it has like 350K or more miles or has been abused with aftermarket engine or exhaust mods causing it to severely overheat for an extended period.

code P0430 is far more often O2 sensors or a faulty ECU

 

I don't know for sure, but I would think that a CA car (if different from a 49-state car) would be so identified on the emissions placard under the hood.

 

The FSM shows some more parts connected around the egr valve for CA models, at least for UCF1x. I've never looked at anything newer so I can only speculate. On the UCF1x there's some kind of air pump.

 

My 99 did not have an egr valve. Also, I replaced both 02 sensors. Codes came back as mentioned. What solved the problem was proper rated cats for how sensitive the post cat O2 sensors are. $450.00 vs $2000. I'll pass on the OEM cats.

 

'98+ 1UZ did not have EGR systems.

 

@Lavrishevo How did your magnaflow cats perform finally though. I am looking for a replacement as well I guess.

 

Been using 2 aftermarket cats on mine here in aus. Ucf10 so only need pre cat sensors