c_smith707070

Ok, here's the story. I bought a 2005 Honda Accord Hybrid with 91,500 miles used two weeks ago, and about a week ago, the check engine light went on showing code P0430. I took it to the dealer and they said the Bank 2 catalytic converter needs to be replaced. I asked if it could be an O2 sensor and the "advisor" said no. He said they cleared the code and it came right back. However, it has happened twice so far that the code went away on its own (without being cleared by me) and the MIL light came back on with the same code (third time the light came back on). I am noticing no driveability issues whatsoever. I went through the service records of the previous owner and saw that he failed an emmissions inspection and had a code P0409 (EGR Valve). The shop did a "decarbonization" service and the light apparently went off and stayed off, and he passed his emmissions inspection (about 750 miles before I bought the car). So far, I've changed the air filter (engine and cabin), changed the spark plugs, did a 3-part fuel-system cleaning service (by Sears), in addition to an oil change. The MIL light has only been back on since yesterday. So, is it possible the EGR valve issue caused the bank 2 cat to go bad? Can it be a bad O2 sensor (which the dealer said it could not be, but I'm almost certain the O2 sensors were not checked)? I just don't want to pay $1,000 to have the cat replaced, if the CAT is not a problem (CAT not under warranty). I also don't want to unnecessarily pay to have O2 sensor(s) replaced if not necessary. Does the fact that the MIL light goes on and off indicate something that I'm missing? I really appreciate any assistance anyone can offer. Thanks!!

slowcivic2k

Decabonizing the EGR ports with the wrong cleaners can foul the converter or cause damage to the substrate. It is not recommended to use anything but the fuel specified. If a part requires cleaning it should be removed, cleaned, and replaced to prevent this kind of damage. I discourage fuel system cleaning as proper maintenance negates the purpose that most of these services are meant to address. Even throttle body cleaning is discouraged in most situations.

A P0430 will only result after the PCM verifies that bank 2 sensor 2 is functioning correctly. If the sensor malfunctions it will produce a DTC relating to the sensor only. Then after the sensor is replaced and it passes its function check, it will then monitor converter efficiency. Therefor you will need a converter, the question is still why. I would bet the EGR cleaning/ "fuel system cleaning" may have done it.

Many techs try the easy way, by removing the valve and probing the passages with pipe cleaners, and solvents, with mixed results.

The converter should still be under emissions warranty. I'm still sending 96-00 civics back to the dealer for the manifold cats under warranty.

c_smith707070

Thanks. That definitely makes sense about the EGR Valve cleaning done incorrectly. The Sears fuel system cleaning I did after the light was already on. The thing that is making me crazy is the fact that the light literally is coming on and then going off on its own. In the last 24 hours the light went off, came back on, went off again, and then came back on again. I have been messing with the gas cap and I think (hope!) that could be the issue? I'm going to replace it today. If the cat is bad, why is the MIL going off on its own? I read something about intermittent failure. But how can a cat be failing intermittently?

I hope this is what's happening on the car:

http://x.nissanhelp.com/forums/front...cheap-fix.html

We'll find out shortly.

By the way, I have had a mini argument with the dealer who is saying that the emmissions parts on this vehicle are 8hyrs, 80,000 miles. However, an 06 Accord Hybrid has an emmissions warranty of 15yrs, 150,000 because CT is a PVEZ (or something like that) state as of 2006 but not 2005 apparently. That is very frustrating.

forted

When the efficiency of the catalytic converter drops below a certain percent it will set that trouble code. Anything that effects the way the engine runs can cause a decrease in the catalytic converter efficiency. A front O2 sensor or air fuel ratio sensor can be almost failing and contributing to the decrease in efficiency of the converter but not set a trouble code.
As far as the emissions warranty the length changes from car to car and year to year. If its covered under warranty the dealer will normally happily perform the work because they are getting paid from Honda.

Mode 6 data would show you how close to failing the O2 sensor is. Most shops don't check this.

If the light has been coming and going I would drive the car several thousand miles and see if the light stays off.

c_smith707070

Very good tip. Do you think another fuel system cleaning will do any good?

slowcivic2k

If the O2 sensor is obviously skewed rich or lean, or has a poor cycle time, the computer will see it and produce a DTC. The question is why is it skewed lean or rich. It could be the sensor, or it could be an air leak/excessive fuel/purge flow problems. Much better diagnosed using fuel trim readings. It will not show you if it is "close" to failing. It either fails, or it doesn't.

slowcivic2k

The MIL will turn off if the catalyst monitor is passing its test intermittently. After 3 successful tests, it will shut it off and keep the DTC stored. On the next failure, it will come back on. It takes a total of 40 passing drive cycles for the DTC to go away on its own.

The EGR valve controls mostly NOX emissions, which the O2 sensor cannot see. This is why you see converters with an O2 sensor in between the substrates, or the center of the converter assembly. The rear substrate is a NOX reducer, and its performance cannot be measured, only by a tailpipe test. (Most diesel trucks use NOX sensors to determine emissions produced, most cars do not) It is possible, depending on how long the EGR system did not function, that converter temperature was too high, damaging the catalyst. I doubt it personally, as most vehicles will model the converter temperature to prevent a failure like the EGR from melting/damaging the catalyst.

c_smith707070

Thanks for your responses. I changed the gas cap about a week ago and two days later the light went off and stayed off for three days. Then yesterday I stopped for gas and for the first time in about 1.5 weeks, I used 87 octane instead of 93 octane, which I had been using. About 10 minutes after I get gas, the light comes back on! WTF?? I retightened the cap, and from now on, I'm only going to use 93 octane. We'll see what happens....

I know there's a very good chance that it has nothing to do with the gas or the cap, but it just seems like a huge coincidence that the light came back on right after getting gas. Thanks again for your help.

slowcivic2k

Check and see what the DTC is, so we can figure out whats going on.

DCFIVER

Possibly but unlikely, however the info is in the datastream....


Mode 6 is not now, nor has it ever been designed to be used for diag purposes on our end. Those who utilize it, incorrectly assume working knowledge of the parameters set. Monitoring the trims is a much more accurate way of determining fuel control and stft is better still for monitoring O2 efficency...

DCFIVER

You have already gotten good advice. Bottom line, you need a cat. Dont waste your money on replacing the O2's for this code.

portenio78

iTrader: (1)

I had a similar problem and also did not want to dish out money for a cat. Had a spare 02 chillen in the garage and decided to swap it into the cat. Problem fixed! My 2 cents ;-)

DCFIVER

On an '05 Accord Hybrid???

DCFIVER

Warranty is only 8 years /100k. (which ever comes first) How are you getting them warrantied?

slowcivic2k

I sent an HX last week to Bemis for a converter, and they warrantied it for her. My interpretation, as a prior Ford tech, is that warranties are discretionary to say the least. Where I was at it depended on the mood of the service manager.

DCFIVER

Sure, Goodwill. They usually reserve Goodwill for loyal dealer customers though. There is very little chance of a vehicle that old getting warrantied under normal circumstances. The OEM will not pay for it once the time /mileage is up, so it would be up to the dealership to foot the bill.

c_smith707070

The code that's back is P0430, and I guess it's throwing the code twice, whatever that means. I think I'm going to resign myself to the fact that I need new cat. I'll find one online and have the dealer replace it. But not without calling Honda customer service first to see if I can get "goodwill" since this is the first Honda I've owned and I'm 31, so I can be a customer for many years to come. Not sure if they will look at that, but what the heck, I'll give it a shot...