I have a 2001 Dakota, 3.9. Got P0420 Code. Changed O2 sensors and Cat and new flowmaster 40 series muffler, also changed plugs, wires, distributor cap and rotor. Code P0420 Just came back. HELP NEED TO PASS CALIF. SMOG TEST.

 

I will move this to the 2nd Generation Dakota sub-forum.

 

Either put a scanner on and erase the code, or take the negative battery cable off to reset the computer and clear the code. I had this code twice, and it's been off now for about a year or so. And I passed emissions a few months after having the code.

 

Is this a after market cat? And what brand of o2 sensors did you use. Hope they are not Bosh.