2004 WRX CEL - How to get code - Page 3
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This is a discussion on 2004 WRX CEL - How to get code within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Originally Posted by MisterNBG I know it's been awhile, I haven't done anything to fix my problem yet. So here's ...

  1. #31
    and the Funky Bunch Calvinball's Avatar
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    Quote Originally Posted by MisterNBG View Post
    I know it's been awhile, I haven't done anything to fix my problem yet. So here's the story, Took my car down the car wash, I let her sit and idle for the 5 minutes it took me to clean the car. After that I drive out to some back roads to dry my car off fast, I pushed the car pretty hard, took her up to redline from 1st through 3rd, once I hit 4th gear, turbo fully spooled and gas pedal floored, the CEL disappeared... I slowed down, started driving like I normally would, I heard no noises and didn't smell anything so what happened? Is the problem solved?

    This seems to me like it was 99% the sensors fault... So like did the sensor melt? is it still there? lol!

    Car idles fine, no smell of gas anymore when starting the car up when it's cold. I guess my problem is solved right?
    If the sensor "melted" then you certainly would still be getting a code. More likely, though usually unlikely, is that you may have blasted out some blockage or buildup that was causing an issue by getting everything nice and hot with the WOT runs. There are those that suggest you should make it a point to do a WOT pull periodically for the car's health, this would be one of the reasons why.

    I may be out of my element here though, admittedly, as there is something that doesn't add up. I believe that the P0420 code requires some driving time to reset itself, so all that I said above may have been butkus.
    Last edited by Calvinball; 08-14-2013 at 10:25 AM.
    - Will
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    Current Car: 2014 Golf TDI
    Previous Cars:2012 WRB WRX Hatch, 2004 RSX-S, 1998 Grand Prix GTP
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  3. #32
    Registered User MisterNBG's Avatar
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    It's been awhile but I just figured I should update.

    I changed the rear o2 sesnor, and what a PITA it was, that thing was stuck in there like you wouldn't believe. I bought the Denso o2 sensor for like $50.



    This is the sensor, the one closes to the rear of the car (it's actually in the middle of the car underneath, but you know what I'm talking about)

    So now I reset the ECU and will report back in 100ish miles to whether or not the CEL came back on.

    Fingers crossed it doesn't lol

  4. #33
    Registered User Obeisance's Avatar
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    100 miles yet? I ask because I too have recently had the P0420 on a car with a stock downpipe. I have yet to properly diagnose the code (which comes right after a day of stop-and-go commuting for 30 miles), so I'd like to hear if you've solved it.
    David - '05 WRX

  5. #34
    Registered User MisterNBG's Avatar
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    Hey sorry to hear you're having the same annoying problem I've been having! Well I put the new sensor in, reset the ecu and roughly 30 miles in the CEL comes back on

    So my solution, I bought the $650 Cobb AP v3. This isn't the cheapest solution. But it sure is the easiest. (in my defense, I was going to get one eventually anyways) so I hooked it up to my car and put on the stage 1 map. This cleared the code instantly (also gained a few hp and mpgs). So I am now 150 miles in and no CEL, car drives so much better with this tune as well.

    Again, may not be the cheapest

  6. #35
    Registered User MisterNBG's Avatar
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    Your car will not pass inspection if it's throwing this code. So hopefully now I'll be able to pass, I'll report back with what happened.

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