code po420 for 2005 suzuki forenaz ex

Question

after fixing a intake hose leak when sitting still the car idles rough or shuts off when i turn on defrost or air condtioner and code po420 comes up

Answer 1

The P0420 code is for a bad catalytic converter. I would check to see if the converter is plugged or plugging up. Remove the upstream sensor and see if the idle smooths out and if the engine stops stalling.