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Thread: CEL with code P0421. Its a failing Catalytic convertor

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    Default CEL with code P0421. Its a failing Catalytic convertor

    So I just got a CEL on my 2.5L Gen2 hatch and Mazda quoted me $1500 to replace the cat. I did a bit of research and found this https://www.carid.com/2010-mazda-3-e...-98136520.html


    Curious if anyone's tried these out and if they help throw out some more power? Also, if anyone's selling a used headers+cat combo, hit me up?

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    Default Re: CEL with code P0421. Its a failing Catalytic convertor

    In all honesty, its a cat. Any muffler man will throw in a universal for around $100. They don't really do anything special. Unless your looking sound specific, I don't see the sense in spending the money. Most out last the vehicle. Odd one fails.

    Sent from my Nexus 6P using Tapatalk

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    Default Re: CEL with code P0421. Its a failing Catalytic convertor

    @dailydose

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    Default Re: CEL with code P0421. Its a failing Catalytic convertor


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    Default Re: CEL with code P0421. Its a failing Catalytic convertor

    I have the same problem,year, and model. I haven't fixed it but I would clean the O2 sensor first if that doesn't work get new ones. The cat shouldn't be going out at all.

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    Default Re: CEL with code P0421. Its a failing Catalytic convertor

    Quote Originally Posted by LinkinEffect View Post
    In all honesty, its a cat. Any muffler man will throw in a universal for around $100. They don't really do anything special. Unless your looking sound specific, I don't see the sense in spending the money. Most out last the vehicle. Odd one fails.

    Sent from my Nexus 6P using Tapatalk
    Cant cut the cat without effecting the exhaust manifold.

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    Default Re: CEL with code P0421. Its a failing Catalytic convertor

    That's depressing because I personally need a new cat. Sigh.

    Sent from my Nexus 6P using Tapatalk

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    Default Re: CEL with code P0421. Its a failing Catalytic convertor

    Quote Originally Posted by LinkinEffect View Post
    That's depressing because I personally need a new cat. Sigh.

    Sent from my Nexus 6P using Tapatalk
    Your converter is cheaper to replace then the following year the most I've seen is 380 for a new one on rock auto.

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    Default Re: CEL with code P0421. Its a failing Catalytic convertor

    Install an 02 extender from eBay. Makes the light disappear lol. Doesn't fix the problem though.

    Sent from my LG-H812 using Tapatalk

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    Default Re: CEL with code P0421. Its a failing Catalytic convertor

    how many km on your car? It might still be eligible for emissions warranty coverage
    2005 Mazda3 SP23 hatchback (auto)
    2016 Mazda3 Sport GT (auto)

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    Default Re: CEL with code P0421. Its a failing Catalytic convertor

    nah not a chance. Its done almost 217k kms.

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    Default Re: CEL with code P0421. Its a failing Catalytic convertor

    Quote Originally Posted by Dk_krypton View Post
    nah not a chance. Its done almost 217k kms.
    Do you have emissions testing in your province? If so do you know if they do the tail pipe test or OBD2 test?

    Sent from my LG-H812 using Tapatalk

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    Default Re: CEL with code P0421. Its a failing Catalytic convertor

    Quote Originally Posted by messupdude View Post
    Do you have emissions testing in your province? If so do you know if they do the tail pipe test or OBD2 test?

    Sent from my LG-H812 using Tapatalk
    Oh I'm the GTA, so as far as I remember its both obd2 and the tailpipe

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