P0420: Catalyst Efficiency Failure

[AcuraTech]

Has anybody had a car that threw this code?

I see this on Acuras once in a blue moon. We replace the cat, and that's about it. Pretty cut and dry.

What I don't get is how a cat can deteriorate on a seemingly normally maintained car. Type of fuel? Type of oil?

Looking for thoughts on this. It's a generic OBDII code, so any car could throw it.

 

[oilyriser]

air leak at the cat gaskets?

 

[punisher]

Originally Posted By: AcuraTech
We replace the cat, and that's about it. Pretty cut and dry.


That is the only way I have fixed cat efficiency codes as well.

Biggest surefire killer is engine missfires, hence mandatory missfire monitors for OBDII. I saw a lot of weekend warriors who ran leaded high octane fuel kill their cats after awhile as well. I have run into improperly manufactured cats, which usually end up under a TSB/program, or an emission recall. At the same time I have seen cars blowing visible oil smoke out the tailpipe that had no cat problems.

After that, it is a guessing game.

 

[alreadygone]

What punisher said.

Bob

 

[MrCritical]

Remember, the 8/80 warranty on the converter is for converter defects, not a converter damaged by missfires or oil consumption.

 

[mikered30]

Test the voltage in the downstream O2 sensor.

 

[TexasHonda]

I have had this code on a 99 Subaru Forester.

After resetting ECU, the code would return after some time, weeks to months in some cases. I replaced the converter on the Subaru w/ an aftermarket Eastern "direct replacement". It fit but just barely and only after some major surgery to cut a hole through heat shield for O2 sensor and plugging the extra O2 sensor bung w/ a spark plug. That's been over a year and code has not returned.

regards

 

[-Clayton-]

I'd also check the downstream Oxygen sensor, I've had them do that before.

 

[ccs v2.0]

My Nissan Maxima throws the P0420 on a regular basis and it's not the cat, but the rear bank 1 sensor (Usually. P0430 would be for the bank 2 sensor).

 

[Duffman77]

Originally Posted By: AcuraTech
What I don't get is how a cat can deteriorate on a seemingly normally maintained car. Type of fuel? Type of oil?

Looking for thoughts on this. It's a generic OBDII code, so any car could throw it.


They have been cutting back the amount of Zinc and Phosphorus allowed in the latest engine oil specs becuase they apparently wear down cats over time. Does you car burn any significant amounts of oil?

 

[lewk]

had this same code on my astro van.after going thru several days of torture , I discovered a cracked cat. also had hi nox readings.use a inspection mirror and check the hidden sides on a COLD exhaust!

 

[brianl703]

Ford has released updated firmware to fix this problem on some cars. Apparently the original program is too sensitive.

I've heard of cars with catalyst efficiency codes passing the sniffer test.

 

[JTK]

Originally Posted By: AcuraTech
I see this on Acuras once in a blue moon. We replace the cat, and that's about it. Pretty cut and dry.


Pre 2005 3.5L Honda Odysseys have P0420 problems as well. Not sure if this was the solution or not, but Honda went from 1 to 3 cats on the 2005+

Joel

 

[AcuraTech]

Originally Posted By: JTK
Originally Posted By: AcuraTech
I see this on Acuras once in a blue moon. We replace the cat, and that's about it. Pretty cut and dry.


Pre 2005 3.5L Honda Odysseys have P0420 problems as well. Not sure if this was the solution or not, but Honda went from 1 to 3 cats on the 2005+

Joel


Yep, the latest one I saw was on a Acura 3.5RL. I see it on TL's from time to time though, too, with the 3.2 engine. Can't see how it would be cat design though, since the RL's cat is like a foot and a half long. BTW this isn't my car. Just cars in the shop I see.

 

[Papa Bear]

What does the company (Honda) say about this code ?? Tech support ...

 

[JTK]

Originally Posted By: Papa Bear
What does the company (Honda) say about this code ?? Tech support ...

Here's one TSB on it: TSB 03-073 Another suspected cause on Honda 3.5's in 1999-2004 Ody's is the EGR plumbing is prone to plugging. Lack of EGR can cause a high enough exhaust temp to melt the cat substrate material.

Joel

 

[dkryan]

ccs V2.0:

What year Maxima?

I replaced the front(?)cat on my 2001 Infiniti I30 (VQ30DE) last July. The CEL threw front O2 sensor codes and they were replaced 2-3 three years prior. The "420" showed up and I was able to obtain a printout of the steps Nissan (Infiniti) recommended to resolve the code.

The dealer (without me telling him I had that multi-page printout) had the car for 2.5 days and called me with updates. He basically followed the steps outlined in the printout to resolve the code. After test driving for 10-15 minutes for each "step," the code re-appeared. It quit re-appearing after a new (but not cheap) cat was installed.

No junk oil in my ride, excellent maintenance, yadda, yadda, yadda. So, what's killing the cats on Japanese rides?

The service writer acknowledged oxygen sensor problems were common with this engine, followed by really bad EGR problems from owners using 87 octane fuel in that engine, versus the recommended 91 octane.

 

[NYEngineer]

My Yukon had a check engine light. I hooked up the code reader and it said Cat Insufficient Flow or something like that. I swapped out all four O2 sensors, end of problem.

 

[ccs v2.0]

Originally Posted By: dkryan
ccs V2.0:

What year Maxima?

I replaced the front(?)cat on my 2001 Infiniti I30 (VQ30DE) last July. The CEL threw front O2 sensor codes and they were replaced 2-3 three years prior. The "420" showed up and I was able to obtain a printout of the steps Nissan (Infiniti) recommended to resolve the code.

The dealer (without me telling him I had that multi-page printout) had the car for 2.5 days and called me with updates. He basically followed the steps outlined in the printout to resolve the code. After test driving for 10-15 minutes for each "step," the code re-appeared. It quit re-appearing after a new (but not cheap) cat was installed.

No junk oil in my ride, excellent maintenance, yadda, yadda, yadda. So, what's killing the cats on Japanese rides?

The service writer acknowledged oxygen sensor problems were common with this engine, followed by really bad EGR problems from owners using 87 octane fuel in that engine, versus the recommended 91 octane.

01 VQ30DE 108K miles w/ no "junk oil" and 91 plus octane gas only. I have a theory on what is apparently killing the cats, but it's just that, a theory.

 

[dkryan]

ccs v2.0:

Thanks for the reply. I've listened to alot of "feedback" on this board, so your "theory" on the "cat killer" is more than welcome! Especially since we share the same model engine.