Had both codes for catalyst deficiency for 3yrs now's, located in jersey. It's the cali ulev though.. due for inspection which simply consist of gas cap and check engine.

Any fool proof ways of getting the code off for a ulev? 98 accord f23a4. Thinking of either pulling the o2 out completely n sticking out of site while putting another o2 in just for looks...... not exactly sure what the downstream o2 reads though to trigger that code.

Other idea which is plastered all over the webs is drill out a defouler n use 1 or 2 to pull out farther from the cat...

Not trying to waste too much time but I'm open to suggestions. Ran cataclean n tune up 2 yrs ago, light came back as I was pulling out of the inspection station with my new sticker. Not getting that lucky this year lol

 

y not replace the O2 sensors? its the culprit 99% of the time. cat's dont go bad unless there's underlying issues to make them go bad(running to rich being the common cause)

 

What are the actual code(s)?
P0420 does not mean a dead catalyst, it is 'catalyst below threshold efficiency'. If the engine is out of tune or needs the valves adjusted this will cause incomplete primary combustion and the catalyst can only function if the primary combustion is within expected parameters. Too rich or too lean and secondary combustion(in the catalyst) will not be efficient.

 

O2 sensors rarely go bad compared to cats... not the other way around. Let alone the codes are not for a o2, it's for catalyst defficiency. And since it's ulev that oem cat like 600$. Throwing p0420 n the other for upstream/downstream catalyst deficiency.

Typically both codes doesn't mean a dead cat but the cat is not being effective enough. Not sure if a "tune up" even gonna do much. Currently not running a oem cat and it lasted only 6 months 3 yrs ago. Ignition system fairly new and did valve lash over winter.

My solution if I can't trick it is just get a f23a1 ecu n go to a dealer n let them flash it for the car. Just tryna see if defoulers actually work for cali emission cars

 

wrong, catalyst should live the life of the vehicle unless something else wrong with the vehicle causes it to go bad. an engine running rich causing combustion in the cat will ruin it but something else must cause that. overfilling oil will also ruin a cat. those are the most common. eitherway, O2 sensors go bad far more frequently than cats. the way they operate just causes them to, layers of carbon from years of combustion ruin their ability to read the exhaust gas passing through them.

If your downstream o2 sensor is bad or going bad, it will give a cat deficiency code. So will a bad engine temp sensor, MAP and IAT sensors rarely too.

If your engine was so out of tune its causing a cat deficiency code it would run like *****, you'd be able to tell.

 

I have successfully used defoulers on OBDII cars to get rid of the post cat O2 sensor errors when deleting converters. However, I'm not sure that they would pass cali ECU requirements.

Your best bet, where you live in NJ, would be to get rid of the ULEV ECU.

That or fix the underlying O2 sensor or engine performance/emission issues. 99% of the time, cat efficiency errors are not cat related. the 1% that they are were because the operator has been running an engine with O2 sensor errors or fueling/oil burning issues for a long time, 3 years would probably do it!

 

A 'tune up' is to verify components are within spec and parts that need it will be replaced.

49state catalysts are not built robust enough or with enough material to last. That's why Calif had to change and enforce new law to guarantee that a replacement catalyst would last 5 years.

Not sure on the ULEV vehicles, but most secondary O2s before '05 can be placed in a modified anti-fouler to get one by emissions testing via scanner.

Later model vehicles, and probably ULEV, use the after cat O2 to aid in fine tuning A/F mixture further.