Question about 2003 Subaru Outback

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P0420 and check engine light

I am considering buying a 2003 Subaru Outback wagon with 115k miles on it. It showed a P0420 trouble code in memory, but the check engine light was off. When I cleared the memory, the check engine light came on in about 60 miles/ 6 engine cycles and does not go out. The seller supposedly had the two O2 sensors replaced. This problem then recurred. I am told to just wait and the check engine light will eventually go out as the two O2 sensors must ''communicate with each other''. This does not seem right. What is the problem? I don't want to buy an expensive problem. Where I live I cannot register the car without it passing an emissions check which WILL check for any trouble codes.

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A p0420 code is set when the computer determines that the catalytic converter isn't doing it's job. In almost all instances that code can't set as a result of a bad o2 sensor so they probably didn't have to be replaced. The catalytic converter will need to be replaced, prefferably by an oem part. This can be pretty expensive and should be considered before purchasing the vehicle.

I have replaced a few bad converters on late model subarus in the past few years.

Posted on Apr 18, 2009

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Posted on Jan 02, 2017

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3 Answers

Computer diagnosis P0420


P0420 SUBARU - Catalyst System Efficiency Below Thresholdxicon.jpghttp://engine-codes.com/p0420_subaru.htmlForum CodePossible causes- Three way catalyst converter Bank 1
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- Engine Control Module (ECM) Tech notes The most common cause is the three way catalytic converter Bank 1 is worn out. Changing just the catalyst O2 sensor usually does not repair the problem. If the P0420 code is combined with other codes, try fixing the other codes first.

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I have a 2000 Subaru Outback wagon with approx. 75,000 miles on it...about a week ago my check engine light came on...my gas cap was loose so I tightened it and the light remained on for exactly one week. ...


you can get pop up trouble light going off if the battery is weak or even low ,, have the battery LOAD tested, you could have one cell bad, so it would show 12 volts but not actually the required amps necessary, this would make the alternator work overtime, which would draw from the power it needs to actually run the vehicle

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Check engine light comes on every 200 or so miles, code P0420. O2 sensor has been replaced. I read that there was a bad batch of catalytic converters in this model. Any other easy tests or fixes?


p0420 is set when the convertor is unable to store oxygen in the minerals used in the convertor. the lack of oxygen to mix with the exhaust gases causes the O2 sensor to set the code. if the O2 sensor has been replaced the only other thing to do is replace the convertor. you can check with the Subaru dealer and let them run your VIN to see if you had one of the defective convertors.

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Robert

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1 Answer

2005 Outback Wagon Code P0420


PO420 is for catalyst system efficiency below threshold. I have seen this many times on vehicles from 96 up. It is due to the system not burning the fuel at what it considers an acceptable rate. Todays fuels are not the best we could have for internal combustion and sometimes it will set off the light. I tell my wife she is too easy on the car and it's not burning the fuel proper. After a couple days it goes out. It will not harm your engine and should go out again. Fuel system cleaning additive will also turn of light. Good luck and enjoy your Subbie. Greatest car ever Built.

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2 Answers

2003 Subaru Outback check engine light stays on


You may have to take it to a shop and have them connect their OBD tool to the computer and clear the deep memory. If you have a code left in the deep memory it can reapear like that. Good luck. Please rate me so I know how I'm doing. Thanks.

Dec 30, 2008 | 2003 Subaru Outback

1 Answer

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Hope it works

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