Of course, there are also other causes of a P0420 code.
From TSB,
�· Malfunctioning ECT/CHT
�· High fuel pressure
�· Damaged exhaust manifold
�· Cylinder misfiring
�· HO2S wiring concerns (shorted or chafed, bent pins, etc.)
�· Damaged exhaust system pipe
�· Damaged muffler/tailpipe assembly
�· Retarded spark timing
Damaged Catalytic Converter:
�· Use of leaded fuel
�· Oil contamination/consumption
�· Silicone contamination (sealants/cleaners)
