Does fuel trim pull a P0420 code??

[bradycatsmokey]

Hello,
Would a STFT or LTFT throw a code of P0420?

I have changed CAT, O2 Sensor, and now thinking it might be this.
My STFT B1 S2 is giving me an NA.
My mechanic said that should not be like that.

What would throw this code in the fuel system?? Bad injector??

Any help would be great, thanks.
Jo

\2002 Grand PrixGT 3.8L

 

[Scottydoggs]

its a 02, you use a factory cat replacement? or a cheap high flow cat? hi flow cat will cause that code too.