PO420/PO430 Catalytic converter replacement???

[des16]

I started my 2004 Sienna AWD Limited and there were two indicator lamps: VSC and Malfunction Indicator Lamp. I brought it to a Toyota dealer who said they he read two codes off the car: PO420/PO430 and that they indicate that the catalytic converter needs replacement. I asked if there was any other diagnostics to be sure, and he said that it was unambiguous: those indicator symbols and the codes mean that the catalytic converter needs replacement, immediately, to ensure no damage to the car. Is this correct? Should he have done any other diagnostics. Could these codes mean anything else?

THANKS.

[fibber2]

Wow, lots of code questions this week. A change in the weather, maybe? Seriously, gas blends change with the season, and you might be a victim of the wrong fuel for the conditions.

OK, so you logged two codes - Catalytic converters functioning below normal threshold on both sides (bank 1 & bank 2). I could be that you simultaneously lost both cats, but I'd sure want to know why!! If there is an underlying problem, like a coolant leak, you are likely to wipe out the new cats in time. It could be a bad tank of gas (or the wrong blend) with contamination that dulled either the cats or the sensors. Sometimes this is reversible with a few tanks of premium. It could also be an ECU issue, and the cats are just fine.

Did they scope the outputs of the lower sensors thru the OBD port, or manually at the sensor terminals? Does it show a normal waveform, just displaced in voltage? Way out of spec, or just slightly? Did they try a tailpipe sniffer to see if it is rich in unburned hydrocarbons? Did they try clearing the codes to see if they immediately come back, or stay out for a while? From what you report, I wouldn't know if you should be changing cats or sensors!

If the upper sensors were throwing codes, this could spell real danger for the engine. The lower sensors are merely tattle-tale tellers, designed to prompt you to fix something that is causing an increase in pollution. Change the cats immediately? I think that's a bit rash!

Will they guarantee in writing that this will fix the issue? You are looking at $2k, with a reasonable likelihood that you'll be back there again because they didn't take the time to figure it out.

[pjksr02]

If the 2004 is anything like the 2001-2003 models, I'd suspect your oxygen sensors are degraded. That's not to say your cat is not degraded--it probably is less efficient at this mileage, exacerbated by colder ambient temperatures. But combine less responsive sensors and a degraded cat and you might just trip the P0420 logic quicker.

On my 2002 Sienna, I've had all these codes (P1135, 1155, 0420), which are now essentially gone after replacing my 3 sensors myself. The P0420 returns now and then, after multiple local trips where my cat doesn't heat up as much as on highway trips. When it does, I clear the code, and then have been ok ("ready" monitors). I have passed OBD emissions, haven't spent $1000+ on a new cat, and haven't seen P0420 since last June. Just my experience...

I agree with fibber. You deserve a guarantee fix if you get your converter replaced.

Someone else posted that VSC also lit with their P0420. Maybe this is a failsafe state.

[steelcity]

I would also like to add , I think there is an extended federal warranty for the emissions system maybe 100k and or 6 yr or longer ?? It may say in the manual . For your sake I hope it is longer and hopefully your under the mileage.

[fibber2]

Good point! From the EPA site:

There are three specified major emission control components, covered for the first 8 years or 80,000 miles of vehicle use on 1995 and newer vehicles: * Catalytic converters. * The electronic emissions control unit or computer (ECU). * The onboard emissions diagnostic device or computer (OBD).

[sirfixalot]

I think the part about immediately getting it done or you will cause damage is baloney, unless the catalytic converter is breaking apart internally and blocking exhaust flow. If the vehicle is running fine, you will not cause damage with an inefficient cat.

+1 on seeing if it is still covered under the federally mandated warranty.

[des16]

Thanks for everyone for their input. Based on what I learned from the forum, I called back the dealer and asked the service manager for more information, and raised the possibility that the cc did not need replacement, and the codes could reflect one of the many possibilities discussed above. He was adamant that the cc needed replacement. I asked him to double check with the mechanic who worked on the car, and send me a written report. He said he would. I have called back several times, and he doesn't return my call and never sent the report. I have since take the car to another dealer, and they said it may be the cc going bad, but no rush to have it replaced, and that in the short term I should, as suggested on this forum, clear the codes and hope for the best. They said they could find no problem with the censors. The codes have not returned after a week of use. I am hoping for the best. I would like my $80 back from the first dealer, and was thinking of calling Toyota to complain about the rushing to a $2000 repair and the poor service I received.

[des16]

I started the car today and the check engine/VSC lights were back on. is it surprising that the codes did not reappear for 10 days? One thing I was wondering is whether changing the spark plugs would help. I have never changed them and the car has 115,000 miles. If not, I am afraid I may not have any option at this point but to bring it to the dealer and shell out the 2K. Any further advice is appreciated.

[fibber2]

Step one is to get a new reading and see if it is the same codes, and to download the snapshot / freezeframe data to see exactly what the operating conditions are at the time the code is set. A good mechanic might be able to make some sense on what might be the true cause with this data in hand. At this point we're still guessing as to whether it's the cats or sensors. You need proper diagnostics before plunking down $2k!

[dan_g]

8 years back when I had the Dodge Caravan, I got similar code at 135k. In fact teh Dealer Service Manager was nice told me to do it outside as he would charge about $600. Ended up replacing the Cat convertor at a regular Muffler shop for $100 or less. The light went out after a few starts.
The Dodge had some cylinder seal problem where it would burn oil and so I guess that was the problem causing the CC to fail.
Is your gas mileage down or do you smell fuel from the exhaust. Another thingsto consider is try to change teh main O2 sensor and see if it helps.

Good Luck

[des16]

Thanks again for the excellent suggestions. I will definitely follow up. The big challenge is finding a high quality mechanic who is both honest and interested doing the careful diagnostic work, not just reading a couple of codes and pushing forward with major surgery. This dilemma is just like finding a good doctor, and seems just as elusive and expensive. But, I will persist and let you know what I find after asking them to to download the snapshot / freezeframe data.

[fibber2]

I'm not sure how much you want to get into the DIY aspects of diagnostics, but perhaps you have a knowledgeable friend who could help you. This probably isn't the best of breed, but for $30 it might tell you enough to either confirm or dispel the need to spend $2000.

http://www.amazon.com/dp/B002PYBZJO/...920_pe_vfe_dt4