Which catalytic converter do I need?

2002 honda civic ex 1.7 is throwing a p0420. It would seem likely that its a fried cat due to driving it for some period of time with a cylinder not firing.  Im looking at oem replacements and im finding two different kinds... An exhaust manifold with a built in cat, and the bent pipe kind.  Which do i need? Or do i need both?

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  • not
    Lv 7
    1 month ago

    The cat in the manifold is the one being monitored and is setting that code. Notice the oxygen sensors are before and after that cat; the input and output are measured and compared by the computer to set that code. The other cat has no sensor after it so it can't be monitored. 

    There is a chance that both cats are damaged from misfiring. There is a strong chance the first cat's reactor came apart and is clogging up the second cat. A backpressure test to check for restriction or visual inspection will be needed to determine the condition of the second cat. 

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  • 1 month ago

    Hmm never tried fried cat, give me porterhouse steak any day

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  • Jay
    Lv 6
    1 month ago

    just go look at it

    • John1 month agoReport

      Looked. Both are present with an 02 sensor on each

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