bchristian

My average Joe work has been verified by another mechanic, and a local Honda dealer that it appears both of my catalytic converters have failed (P0420 & P0430). The issue was attributed to likely the effects of poor fuel quality upon reaching 130,000 miles.

All the alternative culprits have been addressed, all alternative repairs & solutions have been tried, and all possible tests have been performed. Therefore, I am not looking to hear about potential other causes from members but thank you for your input in advance.

I would ignore the item as emission are not required in my area, however the fuel economy appears to be noticeably impacted. I was told the car's exhaust is "back-flowing" due to a likely severe clog in the exhaust system / catalytic converter.

The process for removing the front primary catalytic converter is straight forward and do-able for the average Joe.

The rear catalytic converter is another story. It includes but is not limited to the following: draining ATF, detaching the exhaust, removing the intermediate shaft which requires numerous steps and possible special service tools. I would assume my vehicle specific factory service manual would provide the simplified directions if it were even possible. Therefore, I assume it is not possible.

There is a guy on youtube that appears to have done it. He does not have a hybrid, however the underbody looks extremely similar as it relates to the position of the intermediate shaft and converter. His video is a bunch of rambling and doesn't clearly describe the order of operations or process.

My question is:
Has anyone removed the rear bank catalytic converter on this application before, without removing the intermediate drive shaft?

bchristian

If I had to guess more specifically what caused the problem was unburned hydrocarbons. The PCV valve was quite carbonized and the intake was heavily carbonized upon my inspection. I believe this then resulted in a raised temperature for the converter.

I more recently learned that the PCV Valve is a culprit with other codes on many Hondas. The PCV valve has its own codes that were not triggered in this case.

Almighty-Si

Both catalytic converters failing at the same time is impossible. If the dealership told you that both were bad, they were looking to make some quick bucks. I had an 07 Pilot owner come into the dealership smug, thinking going to his local mechanic and having him scan trouble codes is proper diagnostic procedure and walked in and demand we change both catalytic converters under warranty. When I looked the car over and told him there was nothing wrong with the catalysts he was furious cause what the car really needed wasn't covered under warranty. After arguing with me, the service writer and my service manager for an hour he decided to pay for the repair. So I went back and replaced bank 2 secondary 02 sensor and he was on his way. My service manager called him once a week for a month asking if everything was ok, he said "car is great". A couple weeks after that, saw the man at the service counter and ask if the check engine light returned he said "no, just here for an oil change", I laughed and went on my way.

Your catalyst efficiency is measured by oxygen sensors. These sensors are heated and it's usually the heater circuit that fails which will cause a check engine light but, just because there isn't a check engine light on for one doesn't mean it's not failing. As long as the heater circuit is working and the sensor is reporting data the PCM can't distinguish if the data it's receiving is false and will not set a trouble code for it. This is what we call a "lazy" sensor. What happens is this lazy oxygen sensor reports false data or slow, and the PCM will make changes to how the engine runs to get the catalyst efficiency back to normal range. When it adjusts enough and it can't get it back into this range, it sets the check engine light. What also happens here, is when it makes these changes, it doesn't effect only half your engine but the entire engine. When the PCM tries to get the "faulty" catalyst back into it's normal efficiency range, it can do so, so much that it drives your other catalyst out of it's efficiency range effectively causing the trouble code for the other catalyst as well. These adjustments made by the PCM are specifically made to cater to the catalysts to help prevent further damage. These adjustments made also affect other aspects of the engine as well (performance, fuel consumption).

So before condemning both your catalyst I would seriously suggest trying to find someone who can properly diagnose your problem before you shell out all that money on that repair. Good luck

bchristian

Again speaking as an average Joe, it seams feasible to me that both could fail as they share the same heavily carbonized intake exhaust gases. It is also my understanding that code P0141 is for the oxygen sensor heater failures. My car did not exhibit this code. I did also examine the physical wires on the oxygen sensor as I was aware of that as a potential problem. The Honda factory service manual walked me through these items before ending at the catalytic converter failure.

But your thoughts are a lazy sensor might not trigger the P0141 code but may trigger the P0420 & P0430?

Almighty-Si

Oxygen sensors are 4 wire...2 for the heater circuit, 2 that collect data for the PCM. As long as there is no interruption in the heater circuit it will not cause a P0141 even if data being collected by the sensor is wrong as that circuit is separate from the circuit that collects data for the PCM. Even a lazy sensor will not throw a code until it becomes so lazy that you may trigger a DTC P0133. For reasons I stated above, it can absolutely cause a P0420 & P0430 code.

Again, from my experience, there has never been a case that I've had (or heard of) that needed both catalysts replaced at the same time. As a matter of fact, out of the last 10 instances I have diagnosed these problems, 9 times I have found that other causes were the source of the P0420 and P0430 code. Out of those 10 times I had to replace 1 catalyst which cleared both P0420 & p0430 catalyst codes that were on in that car.

bchristian

Almighty-si you are on it dude! You gave me another idea. So I cleared the code and drove with my Actron on until it captured the code while connected. It appears that P0430 is being triggered first, then P0420 follows soon thereafter. I am going to proceed with checking the wires on the oxygen sensor as the Actron voltage readings appear to be in range and not mirroring each other.

bchristian

To take a step back for those following the conversation.
I have a pre-owned 2007 Honda Accord Hybrid V6 with 130,000 miles that is reading codes P0430 & P0420. In a nut shell down-stream oxygen sensor is “signaling” the catalytic converter is not operating correctly. I say “signaling” and not “detecting” because I am not sure at this time if the issue is upstream, the catalytic converter itself, or the oxygen sensor yet.
Symptom: MIL and MPG around 25 MPG on the highway as compared to historically nearly 35+ MPG!
The code appears after about 4 drives for a combined 200 miles at highway speeds around 70 MPH. The code does not clear unless manually cleared by my Actron.
The V6 has 3 catalytic converters. 2 primary converters labeled bank 1 and bank 2. Both are monitored by A/F sensors at the top and heated oxygen sensors at the bottom and attached to the engine/intake. There is a 3rd catalytic converter near the center of the vehicle that is not monitor by any sensors.
Items of note / full disclosure:
-New tires
-Newer spark plugs
-New air filter
-New battery with higher than OEM CCA
-The correct spec oil (Mobil 1 synthetic) and OEM oil filters always used.
-Intake has been decarbonized and codes have been cleared. P0430 & P0420 both returned.
-EGR value has been decarbonized and codes have been cleared. P0430 & P0420 both returned.
-I had a software update from Honda for the “popping” upon acceleration. Description: HONDA: 2006-2007 ACCORD HYBRID. THERE IS A POPPING NOISE WHEN AT LOW SPEEDS OR ACCELERATION. IT IS A SOFTWARE PROBLEM. *RM NHTSA Reference #10040512. TSB Reference #SB-09-069. The popping was corrected.
-P0430 & P0420 came on within a few months of the software update being performed.
-IMA batteries were replaced 2 years ago.
-No other mechanical or electrical issues.
-Tried 1 bottle of CataClean as directed in desperation, and it did not clear any codes nor did it have any effect on de-carbonizing the intake or EGR valve.
-No accidents or visible physical damages to the converter or sensors.
-No converter rattles or discoloration.
-Oxygen sensors appear to be reading the correct voltage (.5V).
There is no code thrown for P0141 or P0031 related to oxygen sensor heater failure.
I have caught with the Actron that P0420 is being triggered and then soon thereafter that P0430 is triggered.
No rough idle.
No misfires.
No noticeable hesitation on acceleration, I would assume the electric from IMA would mask it anyways.
Upper intake manifold gasket was replaced and seals well.

Current thoughts: a lazy A/F sensor (upstream), possible catalytic converter failure pulling resulting in sensors pulling other catalytic converter readings out of spec.

Almighty-Si

If P0430 is being triggered first, this is your problem area. As you saw, the P0420 code is being set afterward is because of the PCM trying to correct condition to bring your bank 2 catalyst back into it's efficiency range. The 02 sensor voltage you should be monitoring is bank 2 sensor 2 (downstream) as this is the sensor that determines if the catalyst is operating normally. This sensor should read .5volts +/- .1volt (.4 thru .6). If the sensor is making large cycles say, .1 thru .6 or higher at idle (with the code cleared as well) I would replace that sensor and test drive.

bchristian

Another update.

I was test driving with my Actron scanning live data. That car is equipped with A/F sensors on top of the cats and oxygen sensors on the bottom / exit of the cat.

I noticed the 02S22 (oxygen sensor, bank 2, sensor 2) lagging for about 7 seconds around .04 volts before jumping up to .4 volts to .6 volts in range. I am sure I differentiated between the A/F and O2 sensors because the Actron differentiates them and measures the A/F in mV and the O2 in V. Is this what you would expect in the case of "a lazy" oxygen sensor?

I disassembled the catalytic converter setup attached to the front of the motor. The catalytic converter has no rattle, no physical damage, and the honey comb is near perfect condition. The honey comb is white, as opposed to carbonized and black, and there is no melting or physical break down of the honey comb. The sensors are slightly ashy, and the wiring looks good. I started simple by using a wire brush and a small amount of carb cleaner on the sensors. Then I re-installed and will proceed to test drive.

It would be nice if a simple cleaning may be the fix!

The rear catalytic setup is going to be challenging to further inspect due to the location of the components.

However it is looking like I may have isolated the problem already.

bchristian

Therefore, I believe I have debunked the "double catalytic converter failure" I was told. It also proves the codes are not indicative of a definate catalytic converter failure, as a possible sensor issue on one catalytic converter can pull the other out of spec and result in a code.

DCFIVER

You didn't fix anything and needlessly sold an individual an O2 sensor. It is completely impossible for a vehicle of that model year to behave in the manner you described. It would violate the code set criteria and protocol.


Also your explanation of how the the PCM works regarding the codes is complete bull. You really have no clue what you are talking about and need to stop giving this poor guy bad information.

I suggest you catch up on your modules.....

DCFIVER

Unlikely.No. That is not how it works at all.



The rear O2 is not lazy. The catalyst failure testing protocol requires testing of the rear oxygen sensor at least twice prior to failing the cat. The testing criteria for the rear O2 would require a full lean and full rich condition for an unspecified amount of time. The time varies between vehicles because the OSC (oxygen storage capacity) between catalyst varies greatly. Some cats are high OSC and some are low OSC. Their is no published information regarding which type of vehicle has which type of cats.


Because of this there are only 3 things to check when dealing with cat codes:

1. Fuel trims
2. the presence of OEM or equivalent cats
3. Any TSBs regarding PCM reflashing.



If those 3 check out,you need a cat(s) Plain and simple.

Almighty-Si

So what you're saying is that, I never got a car into the shop with a P0420 & P0430, cleared them, performed the drive cycle confirming 1 of the DTC's, monitor said DTC's secondary 02 sensor voltage, returning to the shop, replaced a downstream 02 sensor, performed the drive cycle again and have no DTC's return?

Because the first time I got a vehicle with these codes, I went to my service manager and told him the car needed to 2 cats that needed to be covered under warranty, he called the DPSM and the DPSM told me it was "IMPOSSIBLE" (exaggerated just like that) for both cats to be bad and made me do exactly what I said above.

Yes I needlessly sold that man an 02 sensor as well as the other 3 that I have changed on other vehicles as well, that all have not comeback for anything other than service work. But i'll just continue to sit here and lie because it benefits me, how exactly?

DCFIVER

Sorry guy,the vehicles are not fixed,and your lack of understanding regarding Hondas Catalyst Monitor running criteria are your downfall.I suggest training rather than simply hanging parts.....

Almighty-Si

Right, because who wouldn't come back after dishing out a few hundred dollars on a (according to you) "non-repair" that is covered under a 12/12 warranty. I'm going to go out on a limb here and say, that only makes sense to you.

No reason to sit and brag about training cause if we're being honest, anyone with common sense and basic automotive/electrical knowledge can pass ASE exams.

DCFIVER

So of course you are a Master Technician/ w Advanced level certification like myself,then correct?


So from one colleague to another,why are you passing along such bogus information????

Almighty-Si

No, never went for advanced level certification and I'm sure my master certification has expired by now and I couldn't care less because frankly, they're bullshit.

DCFIVER

Riiiiight......

Coach Steve

I replaced both pre-cats on my '03 V6 Accord last April. After reading the procedure in the service manual and reading all the steps necessary to remove the rear cat, I decided to do some research to see if all those steps were absolutely necessary. Turns out they weren't. I was able to pull the rear cat up and out through the top. saved A LOT of time and effort.
If you do end up having to buy one or both pre-cats, you'll find the absolute best price for OEM's at Sons Honda (sonshonda.com). Both cats delivered with gaskets was $515.00.
Also, if you have to buy them, go with OEM cats. There's plenty of documented info regarding the life expectancy of aftermarket vs. OEM. You'll replace the aftermarkets twice before you have to replace an OEM.

Good luck with this! It wasn't my most favorite repair I've ever done but it wasn't the worst either. The most annoying thing was the time it took to get all systems to ready state. Geez!

bchristian

Another status update:

I have attached PDF freeze data for two different days when I captured the vehicle triggering P0430 & P0420. Feel free to review the data yourself. I am not a mechanic and do not know how to interpret all the data.

Thanks again for those commenting on the this thread. I would like this to be a cordial learning experience for all those participating. I would also like this to be a start to finish problem and solution to share with others.

I brought the vehicle to the local Honda dealer with my information in-hand. I requested a diagnostic service which is $135. So the story goes like this: I dropped the car off last Saturday. They asked to keep it until Monday. I said sure. I got a call on Tuesday saying it looks like you need 2 cats from the service manager.

I said I have P0430 freeze data I can email you. He said send it over. I called back on Thursday evening and asking if the data helped. Service manager says he didn’t get my email. I say ok, stay on the phone with me until you receive my email. He says he didn’t get it again. Thursday evening I hand deliver a PDF print out of the freeze data I captured.

Friday morning I get a call and say my car is ready. I show up to pick up my car and I ask what the technician’s diagnosis is. Different service manager says word for word “he recommends replacing the rear cat first”. I again asked the diagnosis. They repeatedly dodged a straight forward answer and said “he recommends replacing the rear cat first”. I mentioned I have a problem with that diagnosis because to me that sounds like throw parts at it. 1 cat leads to 2 cats leads to 4 sensors and now we are looking at maybe $3,000+ in repairs. I said please let me talk to the tech or the original service manager I spoke with, meanwhile I will leave the car here. I was told the tech was busy.

I call again the next day requesting to discuss the situation with the tech and confirm he received my data. I am told he is unavailable. I show up later that evening and say I am here to pick my vehicle, I by pass any more service managers and go to the GM. The guy was super nice and clearly has superior customer service skills. I tell him as simply as possible I am looking for a diagnosis, and would to confirm my data reached the tech. I had to pay the $135 to get my car back. As of right now, I am awaiting a call from the GM.

I guess what I expect is a “hey give us another chance to figure this out for you”. Alternatively, I expect “hey we don’t have an answer for you, and would like to return partial credit for you as more complete testing could have been performed or a solution may arise at a later date”.

I would like to emphasis I have been completely nice to everyone in the process and not your typical rude customer. I am just looking for honest answers. I told the GM if the tech is not positive I can live with that answer. I realize the tech needs to get compensated for his time, in turn I would expect some documentation or answers to justify the recommendation or an explanation of the tests performed. I also realize that cars can have flaws and software issues can cause havoc for a tech.

I think if I visit the doctor and he says take some pills, I say why and he says just take these pills and if that doesn’t work we can try some other pills, I feel I have some grounds to ask the simple question why do you think I need these pills.

Meanwhile, I stumbled across a TSB for a Honda Civic Hybrid which may be comparable to the Accord Hybrid because of the IMA system, generation of production, possible shared parts and software, and comparable symptoms.

Service Bulletin No.: SB-11-043
Component(s): ENGINE AND ENGINE COOLING
NHTSA ID Number: 10042649
Manufacturer: Honda (American Honda Motor Co.)
HONDA: SEE DOCUMENT SEARCH BUTTON FOR OWNER LETTER. THE SOFTWARE UPDATE INFORMATION FOR SOME VEHICLES CONCERNING THE CATALYTIC CONVERTER BECOMING HOT, AND THE SOFTWARE MISINTERPRETS SIGNAL FROM HEATED OXYGEN SENSOR, INCORRECTLY INDICATING A DETERIORATION OF THE CATALYTIC CONVERTER. *PE UPDATED 5/3/2012. *JS

DCFIVER

TSBs are designed for specific vehicles. The Civic TSB would not apply to your Accord,unless specifically stated otherwise. I have not had a chance to review your data PIDs,I will tonight or tomorrow as time permits.

bchristian

I have no doubt fundamentally what you are saying is correct. As a professional mechanic, have you ever recommended 2 catalytic converters to someone, at the same time, with no explanation of a failure to a customer? I am just trying to understand. I also feel for the mechanic battling software and manufacturing issues.

I am in a situation where there are symptoms that could possibly be related to a $100 autozone sensor or snow ball into 2 OEM cats and 4sensors per the deal in excess of $3,000. I have to protect myself and exhaust all options as a customer.

I realize at times problems can outpace TSBs. My example would be my Lexus IS had a hesitation upon acceleration on a few occasions. It was almost impossible to duplicate. The dealer suggested a carbon build up. They were partially correct based on symptoms and by the book diagnostics. Years later Lexus had a campaign to repair a few years of IS and GS models due to poorly machined piston rings allowing carbon to escape and cause this hesitation.

DCFIVER

No. The information is all in the datastreams and if necessary, subsequent testing can be carried out on any suspected part to verify the fault. You shouldnt. Like any job, there are varying degrees competence with todays mechanics. The information to be really good and to stay on top of the changes in software and mechanical construction is widely available to professional mechanics. But it requires an investment of time, money and commitment, of which few individuals are willing to give. Once the job is done they just go home. No training,no studying,no practicing. 8-5 is it for them.

Many customers(and lesser informed mechanics) believe it is the engineers that come up with the solutions that lead to TSBs. This is usually not the case. Technicians like myself,who specialize,excel and enjoy diagnostic challenges are usually the ones the find the solutions. We do not do "by the book" diagnostics. We think out side of the box. We utilize critical thinking along with experience to determine the best path that will lead to a solution to a fault.


Im not alone,there is an entire network of technicians like my self. We collaborate through the internet and network via the various training events going on around the country,city, county at any given time.....


But I digress,the data you posted looks good for what it displays(numbers are not the only thing of importance. the trend is as well. It is necessary to graph the various PIDs and view their patterns and behaviors under various loads) The vehicle was in fuel control the whole time. This is absolutely essential to proper Catalyst operation. Mode 6 data shows the rear O2 passed its testing criteria. Id feel confident recommending the 2 primary cats. (The third cat is not monitored,so it will never flag a failure.)


I would not replace any of the O2 sensors.




FWIW Honda cats seem to have a life span of about 100k. Ive replaced dozens at that juncture(as well as other manufactuers)

bchristian

At this point, I am still searching for an evidence based diagnosis so I can put this issue to bed.

For example, if the cat was a scheduled maintenance item at 100K and mine outlasted that.

I guess I am thinking the tech is going to say something specific like: physical damage, overheating, blockage, contamination or something along those lines. I would feel better with that smoking gun answer I can visualize.

As for right now, I just wait to hear back from the dealer. Thanks again for your input.

DCFIVER

Catalyst degradation is almost never visual, unless the failure occurred in some catastrophic event. Essentially the cat is poisoned to death via oil and unburned fuel vapors. Even the healthiest running engines produce oil and unburned fuel, and over the years/mileage this destroys the cats ability to produce a chemical reaction. Also vibration and heat wear out the substrate and reduce its size. This in turn reduces the catalysts ability to effectively reduce emissions. With tighter emissions standards,come stricter monitoring. Honda cats are designed to flag a code when they fall below 99% efficiency.....