Catalyst Converter Problem....

[IRA51]

a P0420 is bank 1 I think and it could be anything from an exaust leak to a bad cat . some times a bad O2 can set it . if the down stream O2 does not see much of a reduction it can set it . I would check the O2's first to see if they are good B4 changing the cat .check your coolant level,a leaking head gasket can kill cat's and O2's .