May 26, 2011 · 2005 P0420 , P0430 codes. Jump to Latest Follow ... If it fails the test on successive drive cycles, the MIL is illuminated, and the pending code becomes hard logged. Regardless, he suggested simply ignoring the code unless fuel mileage starts to dip. I've got a Garmin GPS w/the bluetooth HD adapter that reads the codes, so it's easy enough to confirm the engine light is regarding the P0420 code and not something else that I shouldn't ignore.
Code P0420 Definition Catalyst system efficiency below threshold (Bank 1). What Does P0420 Mean? The function of the catalytic converter is to break down harmful pollutants that are created by your vehicle during the combustion cycle and convert them into less harmful gases.