P0420 - Catalytic Converter Efficiency Below Threshold - Page 4 - Subaru Forester Owners Forum
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post #46 of 775 (permalink) Old 09-27-2008, 08:18 AM
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Originally Posted by pleiad7 View Post
Well, it's time for Slynki's (98 S) bi-annual smog inspection, and she's failed twice now with a recurring P0420. First time we suspected she wasn't properly warmed up. Second time she got a good romp on the freeway before the test and still failed the sniffer due to running too rich at idle. What's the consensus on replacement parts in this case? She's got about 200k miles, so we suspect that her cat might be at the end of its intended lifespan. Should we just shotgun the problem and address the O2 sensors as well?
bump for an answer...


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post #47 of 775 (permalink) Old 09-27-2008, 08:52 AM
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Silke, as I have stated in other threads, most don't want to hear it, but unless you have leaks, before the converter, or can prove an oxygen sensor is defective by plotting it's slow/low response, The cat is usually the real fix. Other repairs usually mask it for a while, but replacement is the long term fix.

I have seen this on many vehicles, not only Subaru's. The last guy I gave that information to came back to my house a few months later with an " EASTERN CATALYTIC CONVERTER" for his 99 Forester. That same dual cat fits 99-05 non turbo models. His brother in a parts supply house got it for him. He knew I loved working on Subaru's, and wouldn't do a bad replacement or hit him up for unnecessary parts. A few gaskets AND bolts and he was ready. He already tried the O2 sensors a few month earlier so they weren't too bad to remove and transfer over. His CEL is now gone.

They do list the 98 in their catalog, but it's not the same as the 99. Hopefully Greg still can get a jobber's price on parts.


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post #48 of 775 (permalink) Old 09-27-2008, 08:56 AM
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Thanks ferret, that's what I thought. I think we'll go OEM with the converter since Greg gets the discount... plus, CA laws are really anal about what converter can be used, too.

~ Silke ~
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post #49 of 775 (permalink) Old 12-08-2008, 07:39 PM
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ok guys now what

Ok, so this is a great forum, and either I missed something or it isn't there.

I have installed the $5 mechanical fix. I think that it's a good solution.

However, how do I reset the light? AutoZone will just read it and refuse to reset it.
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post #50 of 775 (permalink) Old 12-08-2008, 09:18 PM
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I'm not sure if you can reset the CEL by disconnecting the battery (ECM reset), or if it will eventually clear if the fault has cleared. I've never been overly patient, so I use my ScanGauge II or my Scan Tool to clear the CEL code.

Bobby...

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post #51 of 775 (permalink) Old 12-12-2008, 02:00 PM
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However, how do I reset the light?
Actron CP9125 PocketScan™ Code Reader. It comes with directions. Picked
mine up at Car Quest

-T
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post #52 of 775 (permalink) Old 12-16-2008, 06:44 PM
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thanks

Thanks guys!
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post #53 of 775 (permalink) Old 01-10-2009, 06:01 AM
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It's been about 19 months since I replaced my catalytic converter w/ an Eastern Catalytic converter. No P0420 for all that time. However, while traveling during Christmas holidays, CEL came on and I had checked at Autozone,...P0420.

Whatever is causing the cat to fail is still there. I suspect very slow loss of engine coolant is damaging converter w/ silicone from the coolant. No way to prove, but I do have a slow (1 pint per oil change) loss of coolant that I haven't been able to locate. I add coolant system seal, but rate is undiminished.

Engine runs beautifully and I don't think an exhaust leak is my problem. Corrosion is a non-issue in TX, and my engine is dead quiet. However, you can never be certain.

I think I'll install the mechanical fix to prevent turning the CEL off frequently.

Regards

See you down the ROW!
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post #54 of 775 (permalink) Old 01-10-2009, 08:05 AM
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Quote:
Originally Posted by TexasForester View Post
It's been about 19 months since I replaced my catalytic converter w/ an Eastern Catalytic converter. No P0420 for all that time. However, while traveling during Christmas holidays, CEL came on and I had checked at Autozone,...P0420.

Whatever is causing the cat to fail is still there. I suspect very slow loss of engine coolant is damaging converter w/ silicone from the coolant. No way to prove, but I do have a slow (1 pint per oil change) loss of coolant that I haven't been able to locate. I add coolant system seal, but rate is undiminished.

Engine runs beautifully and I don't think an exhaust leak is my problem. Corrosion is a non-issue in TX, and my engine is dead quiet. However, you can never be certain.

I think I'll install the mechanical fix to prevent turning the CEL off frequently.

Regards
you sure its not a head gasket issue?

2003 Subaru Forester XS Premium (5MT)
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post #55 of 775 (permalink) Old 01-10-2009, 03:04 PM
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Quote:
Originally Posted by David C View Post
UK '01 Manual All Weather Forester.

The annoying P0420 reappears between 70 and 200 miles. Two independent exhaust gas tests showed near-perfect lack of pollutants so I ended up looking at the oxygen sensors. There isn't much obvious information on these but I appear to have a wideband air:fuel sensor in the front, it has 5 wires and some device on the plug, another oxygen sensor? Is this correct?

The rear one seems conventional with 4 wires, (it's removal just brings up the "sensor heater missing" code).

I'd like to reflash the ECU to prevent P0420 appearing but, apart from anything else, I haven't found the ECU yet. On the RHS (driver's) there are the 2 green connectors but no sign of the unit with it's 3 connectors and mass of wiring. On the LHS there's mostly mouldings associated with the heating/air con. My wiring harness diagram is the US version.
Dave, I have the same model. Are you any further along with this problem?


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post #56 of 775 (permalink) Old 01-18-2009, 04:11 AM
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hi chaps - I picked up a 2002 fozzie automatic yesterday for my wife. When I picked it up the orange emissions light came on so we went to the dealers garage. The guy there hooked it up & told me it was a "cat below threshold" thing. He reset it and told me to keep an eye out. Tow hundred miles later and I've got the car home to my missus - no warning light. She jumps in it to try it for the first time and, hey presto - the damn light comes on again within half a mile. Thing is - the car passed its MOT emissions test last week and economy is great - I got 35mpg cruising at 70 - 75mph!!

What is this "mechanical fix" that I keep reading about?

BTW - I've now got a spare fozzie on the drive - 97R, 117k, 6 months MOT, lots and lots of history, full stainless exhaust (new last nov) silver, AWP and (most important of all) - GOOD non-self levelling rear shocks!!! The only reason I got the missus another one is because she wanted a "newer car with painted bumpers". I'm in the Humberside UK area if anyones interested in making an offer??
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post #57 of 775 (permalink) Old 01-18-2009, 05:08 AM
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"mechanical fix" info:
Rear O2 Sensor fix for CEL code P0420 - ScoobyMods

'02 L m/t. Insurance adjuster 4 U.
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post #58 of 775 (permalink) Old 01-18-2009, 07:03 AM
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I installed mechanical fix in my 99 Forester this past weekend, reset CEL off, and so far CEL has not returned. I hate a cludge fix, but I'm not putting another converter into this car.

BTW, I finally fixed the squeak/squeal caused by the Eastern catalytic converter. The new converter was slightly longer and pushed the rear exhaust system slightly rearward. One of the tail pipe hangers mushroom end was rubbing against the support bracket making the noise. I ground the bracket w/ a die grinder to eliminate the interference, and my wife was pleased.

Yes, coolant leak may be a head gasket, but the oil is clean and engine runs perfectly. I can live w/ a cup of coolant a month. I think the leak is external as I can smell antifreeze cooking smell every time I stop, but a detailed inspection has not revealed the source of the leak. I've seen some posts about external leak on driver's side cylinders, which is what I suspect. I will look closer next time I remove the undercover for oil change.

good luck

See you down the ROW!
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post #59 of 775 (permalink) Old 01-19-2009, 01:02 PM
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excellent post ddavidv - many thanks

I've tried looking for one of those spark plug non fouler things here in the uk with no joy - any ideas guys?
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post #60 of 775 (permalink) Old 01-19-2009, 01:31 PM
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just found this link - I know its not for scoobys but the pics are great - really support earlier comments & show how to machine "those thingies"

evolutionm.net - View Single Post - How to install the spark plug anti-foulers to remove the ses or cel light

interestingly, this link came from a Lexus site - lots of posts about getting around annoying CEL problems!!! Having spent time in Japan a few years back I can easily believe that the Japanese obsession with "engineering perfection" & emissions all stack up to this sort of issue a few years after a cars been built. I wonder what percentage of cars that have this annoying problem were NOT built in Japan?
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