P0420 Lexus -

Question

my diagnostic reading said PO456, the emission system leak is very small, could this be why I also have PO420 catalyst system efficiency below threshold

Answer 1

Hi there,

These codes are unrelated and in 2 different systems. The evap small leak should be checked by doing a smoke test on the evap system. This might be simple like a gas cap that's not sealing properly. The other code, for the converter is normally caused by a bad converter or the rear O2 sensor.