P0420 & P0430 Codes - 03 4Runner 165K

[kosan]

Did you replace the cats and still get the same error codes?

Since replacing the all the O2 sensors and both cats, I have not had an issue. If you live in a state that doesn't require emissions, I wouldn't of bothered to fix it.

 

[Ktorr]

this is why i asked about v6 vs v8.

i replaced the front cats with pacesetters, quick search yeilded 750045 and 750046 are the parts YOU need for a v6 49 state vehicle, they $350 and 375

what i would do in your case. from experience i would do this.

drive your truck with the rear window cracked open a little bit. check if you smell rotten eggs stink. if you do, you have bad cats. if you dont, there might still be hope and its just sensors going bad.

buy from rockauto.com all the oxygen sensors, should be 4. buy the denso oem ones. find a coupon code for rock auto. they always have 5 or 10% off floating around.

yes all 4, around $300 for the 4.

why?

if cats are bad, sensors are bad too.
if sensors are bad, and that fixes your problems then you dont have to spend the money on cats, headstuds, bolts and labor.
if sensors dont fix your problem still and you dont have stinky rotten egg exhaust, you can cheat and do the spark plug fouler mod for $10.

actually right now with the two p420/p430 codes you can do the spark plug fouler mod and it might work. in my case, i did not want to cheat since i wanted a properly running vehicle for the long term.

then again, my advice is subjective because i have a v8 and might be different scenario than your cali emission v6. none the less i feel your pain with the mixed advice from your mechanics and then us online mechanics LOL. if you are lucky hopefully someone can chime in that was in a similar situation like yours.

good luck

I have a similar situation going on, p0420 code came on after a missfire but was not there with the missfire code. Refused to believe it was the CAT going bad and shortly after got P0430, then I have confirmed it is definitely not the CATS. Since, I have swapped out 3 of 4 o2 sensors and code persists. After further examination we have found vacuum leak so I have swapped hoses and gaskets. Literally removed the CAT to examine but looks good, flushed with a bunch of gasoline and break cleaner to see if there were any damaged pieces that flushed out or dirt but everything came out clear. Code still comes back on. We have also checked the live stream data, swapped sensors one more time and see a big change in the spike when its idling versus when running.
Next, we will be replacing the fuel filter and if needed the pump and injectors. I am hoping this resolves the issue.

Any additional suggestions are greatly appreciated.

 

[Pabst13]

I also have been getting p0430 code as well as the VSC TRAC and VSC OFF lights on the dash. I just bought the truck, ‘04 Sport Edition 4wd w/203k miles. The prev owner said that the code was an O2 sensor but my technician says the Bank 2 CAT is bad. The downstream sensor seems loose, washer shakes, and it looks to have an exhaust leak at the junction just prior to the O2 sensor. Could a leak there cause a prob and trip there code? I’ll keep trying to upload a pic, but there looks like black burn marks on the flange and the support/nut is rusted when literally nothing else on the undercarriage is.

 

[MikeinNH67]

I also have been getting p0430 code as well as the VSC TRAC and VSC OFF lights on the dash. I just bought the truck, ‘04 Sport Edition 4wd w/203k miles. The prev owner said that the code was an O2 sensor but my technician says the Bank 2 CAT is bad. The downstream sensor seems loose, washer shakes, and it looks to have an exhaust leak at the junction just prior to the O2 sensor. Could a leak there cause a prob and trip there code? I’ll keep trying to upload a pic, but there looks like black burn marks on the flange and the support/nut is rusted when literally nothing else on the undercarriage is.

Yes an exhaust leak can do this. Fix that first. I was getting a similar code maybe once a month but after fixing my exhaust leaks getting this code is now rare for me. I wouldn't go swapping the cat yet. BTW, the OEM cats are worth some money to recyclers if you do end up replacing it.