Today my check engine light came on . I have a 2001 camry 4 cyl engine auto tranny. I run the code reader and i get code
P0420. code P0420 means Catalyst system Efficiency below Threshold (bank 1). what exactly does this means. also i live in the noetheast we just got hit with heavy snow. could all the slush being kick up into the car cause this problem? thank you for any help.

It's really cold, you could of gotten snow up in there or something. See if it happens again.