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P0420 - 2002 Prius 285000 miles

Discussion in 'Generation 1 Prius Discussion' started by kbbpll, Apr 19, 2022.

  1. kbbpll

    kbbpll Junior Member

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    Our 2002 Prius has 285000 miles on it and has had the check engine light on for a couple months. I had the shop pull the code and it's P0420, which indicates a catalyst system / catalytic converter problem. They gave me an estimate of $2123 to replace.

    I'm having a different shop more geared towards mufflers/exhaust look at it next week. $2123 seems extreme and I have no idea what all the first shop is including in that, as far as oxygen sensors etc.

    The engine has made a subtle knocking sound for over a year now, which seemed to coincide with the first shop replacing the ignition coils. I've just lived with it, but thought I'd mention it in case it's related. The check engine light / P0420 is much more recent. I've also noted over the past 6 months or so that the mpg has gone down from the high 40s (winter) - low 50s (summer) to consistently around 46, i.e. roughly a 10% drop. At first I thought this was due to new tires, but I'd never seen that kind of drop previously having gone through at least 5 different tire brands (currently Falken Pro Touring A/S).

    I'm not a DIY guy so I'm wondering what I could be getting into with this P0420 thing. The car still drives like a champ otherwise, but it's 20 years old, the dreaded big red triangle has gone off several times over the past year or two indicating a HV leak, and I'm not sure if we're at the "let it die" phase or not. I just put $650 into replacing one front wheel bearing (the mpg hasn't improved after that) and formerly the most reliable vehicle I've ever owned is becoming a money pit.

    Any insight appreciated. Thanks.
     
  2. ChapmanF

    ChapmanF Senior Member

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    At 20 years and 285,000 miles, that's a great life out of those catalytic converters.

    If you went to the Toyota dealer, they would have quoted a Toyota part. From Toyota, the whole exhaust system from the manifold back is only two parts: the rear pipe and muffler is one, and the front pipe assembly is the other, which includes the first catalytic converter, the second catalytic converter with hydrocarbon adsorber and valve actuator, and a sub muffler, all made out of stainless and ready to last 20 more years and 285,000 more miles. All of that figures into the price of the part.

    The exhaust shop will probably have a more economical aftermarket part they can sell you, cutting the original pipe and replacing just the cat converters.
     
  3. 2010moneypit?

    2010moneypit? Active Member

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    unless you Live in California.
     
  4. kbbpll

    kbbpll Junior Member

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    The above quote is from a local shop, not the dealer. I called the dealer where I purchased to get an estimate yesterday and they have not called back yet. The muffler/exhaust shop said it might just be an O2 sensor or something else. But after 20 years I'd guess it's the cat converter, over $2000 just seems extreme. Used/new cars these days are so expensive it could be worth it, but I'm also looking at having to replace the HV battery soon (at least three "HV leak" codes / red triangles in the past year) for another $3000... Thanks for any opinions.
     
  5. ChapmanF

    ChapmanF Senior Member

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    There can be battery codes indicating that modules have just irreversibly deteriorated, in which case replacement of the battery is about the only response (or a whack-a-mole version of the same). HV leak codes aren't exactly that, though. Sometimes the leaks, depending on where they are, can be cleaned up, a job that's mostly just labor.

    It shouldn't be put off indefinitely, though. The triangle and leak code will first appear when just one leak has developed. One leak is not an especially big deal (though it should make you follow all your safety and PPE precautions extra religiously when going anywhere near the high-voltage system).

    But often, when one leak has developed, another is not lagging too far behind. Should that second one complete a circuit with the first, you may have more of a problem.

    Of course, if your battery is also twenty years and 285,000 miles old, it could easily be sent off with a distinguished service medal at this point.
     
  6. Josey

    Josey Active Member

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    While it's not overly surprising that at catalytic converter would need to be replaced at that mileage, I've actually had them go many more miles than that (tho not on a Prius). They're largely passive things that just initiate a chemical reaction on the exhaust flow. And while they may simply degrade in various ways just from time and miles, they can also get compromised by various upstream problems - such as coolant leaks, running too rich, or misfiring (which has a similar effect as running too rich). A lot of catalytic converter failures are merely symptoms of other issues and people waste money by just having the converter replaced only to have it wrecked. (And it won't necessarily happen immediately).

    So I am going to connect a few dots and suggest that you have some other things looked at. First, someone should look at your O2 sensor output (as one shop noted they would) and what they are doing, along with the fuel trims, which are closely related. You mentioned having the ignition coils replaced - was that because of a problem or just something like a suggested maintenance. Then you mentioned a "knocking" noise? Could you describe that better? If something is off in your fuel/spark/air system, then the P0420/cat problem can merely be symptomatic - and it is possible for those problems to be minor enough to not trigger other codes.

    If you are having an such an upstream problem, this would also explain your lower fuel economy. (Except that if your HV battery is on its last legs, that would also explain it).

    It also, however, sounds like you might want to peruse this thread: Who should and should NOT buy a 2001-03 Prius | PriusChat (and pretend the title says "keep owning" rather than "buy.")
     
  7. ammdb

    ammdb Active Member

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  8. kbbpll

    kbbpll Junior Member

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    Sorry for disappearing. I'm not receiving alerts when someone posts here.

    As of yesterday: The second shop started with replacing the upstream O2 sensor. They seemed to have done more thorough diagnostics than the first shop. They noted "misfires not present at time of testing" - there was a "P0301 cylinder 1 misfire detected" in the stored codes along with the P0420 cat code. They could not get the O2 sensor off, so ended up replacing the exhaust manifold as well (according to what they said over the phone). The notes however say "replaced upstream oxygen sensor and O2 bung, due to seized sensor in bung" and the itemized parts are the O2 sensor, exhaust manifold gasket, and O2 bushing. So it appears they didn't actually replace the exhaust manifold itself. Knowing little about this, I'm guessing they just removed it in order to get at the O2 sensor. Looking under the car on my garage floor, nothing looks "new" that I can see.

    The check engine light is off now. However, they noted that "all passed except catalytic converter monitor, pending code, light is currently off, but likely to return." Now there's a warm fuzzy feeling for you.

    They said that the fact that it was so seized up meant the O2 sensor had never been replaced. I'll have to dig back through my records but certainly if it was it would have been at least 10 years ago.

    More recently, I had the front right wheel bearings replaced 04/11/22 as noted above. 05/21/21 it was in the first shop for the P3009 HV leak - I read on here or elsewhere that it could be causing by dirty transmission fluid, so I had them "power flush" the transmission. I recall that the big red triangle returned after that, around November, but went away on its own (weird?). So we've gone at least 6 months without the P3009 returning. 12/09/20 a bit further back we had the inverter coolant pump replaced after a P3130 out on the highway. 07/31/20 was when we had the ignition coils (and plugs) replaced. This was a previous time when the check engine light came on. They charged me for a diagnostic but did not note what the code was. The check engine light came on again shortly afterwards and I noted a strong solvent smell under the hood, took it back to the shop, they said it was because the throttle body was dirty, they apparently cleaned that but did not charge me for it, so I don't have any specifics on that one either other than my written note.

    I suppose all of this is just normal for a car at the end of life. I'll admit to not adhering to the "maintenance schedule" after about 150k miles, just oil and fluid changes and fixing whatever comes up. The big problem we now face as I see it is that the most recent shop said they can't find an after-market catalytic converter and I'm not sure if even the OEM one is available. So if the P0420 comes back, we have until September before our next emissions test. We're in CO and they require CA stuff. I'd sure like to take old Moonbeam to 300k but we'll see. It still drives and looks great, and I much prefer the sedan design over the post-2004 hatchback. I suppose we'll just go all-electric next anyway... we installed solar panels last year.
     
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  9. kbbpll

    kbbpll Junior Member

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    The check engine light came back on, two days after the O2 sensor was replaced.
     
  10. dabard051

    dabard051 Tinkerer-in-Charge

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    It's likely that the cat converter is, indeed, at or near end of life. Depending on the state in which you live, you can order a direct-fit Eastern Catalytic for about $250 (Rock Auto #642030 = Eastern 40544) and either install it yourself or have a shop do it. Might also require the #2 O2 sensor, if you can't get the one out from your current cat.

    If your state is extremely fussy (i.e., NY or CA; maybe others) you may need to go out of state to get the work done.

    A long shot is to buy a can of CataClean (about $26 at Walmart) and follow its directions. It alleges to clear out the stuff that accumulates in the cat converter to bring back some of its catalytic efficiency. FOLLOW THEIR DIRECTIONS. This might buy you more time with the existing hardware.

    The drop off in your MPG may be due to the engine having to spend more time running in order to get your HV battery pack up to charge. I'm working on the assumption that the HV pack is still original (congrats on keeping it for 20+ years!!).
    <edit> just read through the entire thread; josey already suggested this...

    Keep us posted!