When I did a cat, it was recommended that I go with Honda not generic parts. Only had to do one. Is it worth clearing the codes then seeing?

 

Just because P0420 or P0430 codes come up doesn't automatically mean replace catalytic converter(s). Replacing the cat is much like treating the symptom rather than the cause. The biggest trouble these engines have is oil consumption caused by cylinder deactivation, known as VCM. This causes certain cylinders to lay dormant when coasting, maintaining speed or in cruise. Excessive oil can be pumped up into these cylinders causing oil to blow past and into the exhaust system along with a host of other engine related problems. Most notably fouled spark plugs, dirty injectors and valves and worse, stuck piston rings. I was plauged by these emission codes until I disabled the VCM. I am currently using S-VCM to keep my engine running on all 6 cylinders 100% of the time. This along with a few other maintanance items and checks can very likely make this code disappear permanently.
Just one question 1st, was the timing belt water pump job done around 105k miles?

My list for a smooth running V6...

1. Disable the VCM
2. Air filter New/Clean, installed correctly, box sealed
3. Air intake tube crack/leak free
4. Clean Mass Airflow Sensor (MAF), unplug/remove, with CRC Electronic Cleaner or MAF cleaner, with a few short bursts spray directly into the visible electrodes to knock the dust off (no soaking), let dry completely before re-installing
5. Spark plugs New/Clean, replace every 100k miles, use NGK Laser Iridiums only
6. Seal spark plug tube oil leaks
7. Coils firing, clean of oil, replace oil soaked boots
8. Replace PCV valve
9. Replace EGR valve (high milage with unexplained rough idle)
10. Use full synthetic 0w20 oil, no Extended Performance or semi blend oils
11. Use a top tier 87 octane fuel or use injector cleaner regularly
12. City drivers after completing 1-11, take the vehicle on some long extended periods of highway speed drives.

 

Was this ever resolved? I’m having the same issue. I recently purchased a 2010 with 140k. After a month I got a p0420 after using questionable gas. I could get the light to go off with Shell gas. Regardless, the cat and flex pipe was changed and that code is gone. Now, to my surprise, I’m getting a p0430. It has me confused as to why this cat wasn’t a problem until I changed the other.

 

Btw, I disabled VCM after the first cat replacement.

 

How long has the VCM been disabled? It takes time for the carbon deposits to burn off.
Has the maintenance list above been done?

 

The VCM has only been disabled for a few weeks. I have not made it through the maintenance list yet, but plan to chip away at it.

My main question was that I couldn't figure out why "fixing" one cat code would lead to another popping up. Does this seem common or just a coincidence?

 

The VCM has only been disabled for a few weeks. I have not made it through the maintenance list yet, but plan to chip away at it.

My main question was that I couldn't figure out why "fixing" one cat code would lead to another popping up. Does this seem common or just a coincidence?

I wouldn't say either or. If another code came up and its after the VCM was disabled, then it could be other things on the list.
I don't want to give the impression that catalytic converters might not need replacing ever. I just know that if the problems that cause emission codes are handled soon enough, a cat clogged with carbon deposits can eventually burn off if the cat has not been damaged.
Yes, the rest of the maintenance items are important to do if you plan to keep the vehicle.

 

I appreciate all of the input. I'm prepared to have to replace that cat too just to get a fresh start. Perhaps I'll wait it out through the winter and see what the frequency of the code is. As of now, it's only the P0430. The car runs and drives great, though I'll probably tackle the old suspension next.