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P0420 Code - Converter and sensors only 3 years old, 30K miles - 2000 Civic GX

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  • P0420 Code - Converter and sensors only 3 years old, 30K miles - 2000 Civic GX

    I just got a 2000 Civic GX from a friend. It has 290K miles and I got it with 4 misfire codes and the P0420. I ended up running bludevil through it and the misfire codes went away, but #2. The #2 injector was working intermittently so I replaced and misfire codes are gone now. The P0420 is still there though.

    I have screenshot of the code

    Calc Load 67.5%
    ECT 189F
    STFT B1 -9.4%
    LTFT B1 -6.3%
    FP 33.1
    MAP 20.1
    RPM 2169
    IAT 86F
    TPS 17.3%

    The car has newer O2 sensors and cat. When I monitor the live data the B1S1 sensor is usually around ~0.6v then drops down intermittently and creeps back up, which I think is supposed to be normal. The B1S2 sensor is a steady ~0.8V.

    I check for vacuum leaks and didn't see anything obvious. The car was pretty meticulously maintained professionally. Im thinking I'm going to pull the injectors and run some cleaner through them to see if maybe that helps as the STFT B1 seems pretty low? Other than that, I don't know what to do next or how to diagnose further. It seems really unlikely that the O2 or cat is actually a problem after only 3 years and 30K miles?

    The car seems to run good now, haven't put too many miles on it though either. Attached is a picture of the rest of the maintenance on the car.
    Attached Files
    Last edited by Bhollehday; 11-13-2018, 06:19 PM.

  • #2
    From what I've read here on cngchat, some say that it doesn't take many misfires to ruin a catalytic converter. Sensor failures are rare.