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P0420

This is a discussion on P0420 within the General Help forums, part of the LSx Technical Help Section category; I'm having one hell of a time with this thing. I just passed emissions last week thank god (after 2 ...

  1. #1
    Member Guerrillakilla13's Avatar
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    2002 Trans Am WS6

    P0420

    I'm having one hell of a time with this thing.

    I just passed emissions last week thank god (after 2 months overdue registration, but that's another, very long story). After fixing the small evap leak from the tank, just yesterday the Service Engine Soon light came back on AGAIN! So I took it in to autozone and I came up with a P0420 and another code pending. Apparantley that has something to do with my catalyst system...

    What are the most common problems with these cars when they get the P0420? Where should I start?


    Over the course of the last 3 weeks, I have spent over $1k on JUST repairs. Now I have this. Can I get some good news from you guys or am I about to have another headache?

    Car is WS6, only has borla catback, and has 45k miles on it.

  2. #2
    Veteran 0rion's Avatar
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    99% of the time that's a cat on it's way out. 420 is bank 1 which is your drivers side. That's the bad news. The good news is there is a 10 year 120k mile warranty on your cats so you may be able to get those replaced under warranty depending on your build date, mileage, and vin.


    post 13 of this thread has all the info

    P0430: 2nd Bank not efficient..could this be prob

  3. #3
    Moderator Firebirdjones's Avatar
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    Time for headers and an off road Y

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    Member Guerrillakilla13's Avatar
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    Thank you Orion! Its a 02 w/ 45k miles, should be under warranty but I called my local dealership and they didn't say anything about it. Told then the code and my VIN..I'm guaranteed that warranty? It wasnt something extra you had to pay for?

    Firebird Jones....EXACTLY gives me a great reason for pacesetters and tsp Y
    2014 Camaro: Check. 2SS: Check. 1LE: Check. 6 Speed manual? CHECK

  5. #5
    Veteran 0rion's Avatar
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    that warranty was gm issued coverage adjustment so you didn't have to pay for it........it will probably come down to your build date. Also, most dealerships probably don't know about it so you'll have to ask them to look it up. Give them the number........05513

  6. #6
    Drop&Drag matt evans's Avatar
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    long tubes all the way delete the cats and run a x-pipe. You can still have your rear o2s put back in the pipe and you wont see any codes. I found this out doing it to 3 different f-bodies this way and no SES lights at all. And you can pass emissions,,assuming they dont look for the cats.

  7. #7
    ʢ ൧ ൨ ൩ ൪ ൫ ൬ ൭ ൮Ր Ց Ւ Փ Smittro's Avatar
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    You can have the rear 02's turned off also..

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