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op 1/29/2013
2001 Honda Prelude Base 4 Cyl 2.2L - Engine
P0420 failed smog test
Something about air injection
1 Answer
  • Jimm
    Jimm 1/29/2013
    P0420 = Catalyst system efficiency below threshold (bank 1)

    A code P0420 may mean that one or more of the following has happened:

    Leaded fuel was used where unleaded was called for
    A damaged or failed oxygen sensor (HO2S)
    Downstream oxygen sensor (HO2S) wiring damaged or connected improperly
    The engine coolant temperature sensor is not working properly
    Damaged or leaking exhaust manifold / catalytic converter / muffler / exhaust pipe
    Retarded spark timing
    The oxygen sensors in front and behind the converter are reporting too similar of readings
    Leaking fuel injector or high fuel pressure
    Cylinder misfire
    Oil contamination

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