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Old 02-25-2011, 04:00 PM   #1 (permalink)
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I got a 2000 subaru outback, 90,000 miles a few months ago, I love it, it is my first and I am sold! Just recently my check engine light came on, I took it to the free autozone reading, code P0420, I replaced the 02 sensor coming out of the catalytic converter, reset my engine light by unplugging the battery for 20 minutes. The light went off!!! It worked......so about 400 miles later the light is back on....I took it back in and got the same reading P0420....I replaced the front O2 sensor and reset the check engine light with the diagnostic computer. One day of driving and the check engine light is back on...I am guessin P0420.... what next, is it the catalytic converter?
ned
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Old 02-25-2011, 04:25 PM   #2 (permalink)
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Time for a cat (which might not fix it) or a drilled-out spark-plug anti-fouler.

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Old 02-25-2011, 04:53 PM   #3 (permalink)
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It's not the cat. PO420 is THE most common code and can be caused by a long list of things including vacuum leaks, exhaust leaks. I don't know why you changed the O2 sensors you would more than likely had a different code for them. Don't keep throwing parts at it, especially something as expensive as a cat.
Do a search on this forum (or any other) and get ready to do a lot of reading.
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Old 02-25-2011, 05:00 PM   #4 (permalink)
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Please replace your Catalytic converter--it must be "pure" Subaru. That said, I hope your technician is competent and honest. In order to ascertain the exact problem, my "techie" when through my car with a "fine tooth comb." Mine just cost 1,800.00 including parts, labor, and CA. tax. Yes! It is worth it. I have a 2001, ten-year two months old Outback with 177,000 miles--manual transmission, large Rhino Rack 4' X 6' mounted to Thule feet and bars. Also, I have complete winter package. I am so elated and ecstatic. I exceeded all California smog requirements. This weekend I go to snow country to purchase fresh organiz ice cream from my friend's factory in Pine Grove, CA. That is a 120 mile drive east of Napa. Yes! I have SSC cable chains despite AWD.
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Old 02-25-2011, 05:10 PM   #5 (permalink)
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I'm gobsmacked at that reply... can't tell if you're funning us or need your caffeine intake cut down!

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Old 02-25-2011, 05:11 PM   #6 (permalink)
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I've had the PO420 code on 3 different Subarus, a Pontiac Vibe and a GMC truck and never was it the catalytic converter at fault.
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Old 02-25-2011, 05:26 PM   #7 (permalink)
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What brand O2 sensor did you use?

Have you checked for exhaust and vacuum leaks?
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2003 Outback: "Kaylee". 142,000 and counting.
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Old 02-25-2011, 07:14 PM   #8 (permalink)
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I used a bosch o2 sensor for the downstream and a subaru one for the upstream. Can I check myself for exhaust or vaccum leaks?
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Old 02-25-2011, 08:31 PM   #9 (permalink)
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Subaru O2 sensors are made by Bosch so they should be fine.
Checking for exhaust leaks is easy. To cause the light to come on the leak is most likely before the rear O2 sensor because beyond that point there is nothing to monitor the gases. Lay under the car with the engine running and look, feel and listen for escaping exhaust. Of course it's easiest to see when you start the engine cold and the high idle is on and a lot of vapour is coming out.
Vacuum leaks are a little harder to find. Check for any loose or broken lines and hoses. If you spray starting fluid around suspect areas with the engine running and the engine increases in speed, you've found a leak.
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Old 02-25-2011, 09:12 PM   #10 (permalink)
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Thanks blacky, upon reading different posts I think I should also clean/replace my pcv valve...and maybe use seafoam....would this help..
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