Codes

So my truck started throwing codes p420 and p430 last week. I was recommended to replace both cats. Left the truck sitting for the long weekend since the holiday. Today when I started it this morning the light was on. drove for about 15mins parked it when I came back out about an hour and a half later the check engine light was off. Not sure why that would happen and now I’m not sure if replacing them is still the way to go. Could it be something else causing it to throw a code? thoughts?

 

When i was younger i had that code on an open header honda i was trying to get through Pennsylvania emissions. I ended up welding chunks of scrap metal in the exhaust to reduce the airflow, (increase backpressure, if you will), i would weld a piece, clear code, take for ride until readiness hit, then when code came on, i welded another piece, and kept going until it passed. it worked. idk it was a wild guess but i got it to pass and readiness to set.

but yea that code coudl be a bunch of things, in my case its an air leak, but yoru secondary o2 could also be causing it. What kind of code scanner do you have? sometimes the MILight goes off, but the code is still stored in the ECU.

check the exhaust and look for leaks. OBD2 codes are always correct, a lot of times its a good indcation of where to start looking though. Regardless, i wouldnt take this code seriously unless you are trying to pass emissions.

 

Yeah those codes typically indicate bad cats, but they could also be related to a faulty O2 sensor or the sensor wires. I'd make sure the wiring to all the O2 sensors looks good first- specifically the downstream one, then start throwing money at it.

 

Converter codes and evap codes can be finicky. They can set, get cleared and take weeks to reappear. It's because of the strategy used to monitor and detect failure. Not a perfect system

Long story short, in my opinion, of the fuel trims are stable and there's no exhaust leaks anywhere it probably needs cats

Any history of active misfires? Like a bad plug or coil? The raw fuel that goes down the exhaust can harm converters and make them fail prematurely

 

I have seen converters that are marginal fail the monitor under some conditions and pass it in other conditions but yea exhaust leaks, fuel trims, and proper AFR & O2 Sensor function should be verified before condemning the converters.

 

I’ve always wanted to try this but never have
https://youtu.be/5icTmYItwiE

 

Do you try use seaform to clean it up and put some at your gas tank.