I have both the p0420 and p0300 codes. is there a common cause?

Question

it sputters when I accelerate. sometimes idles rough. doesn't do it right away on start up.

Answer 1

HI there,

The most common cause is faulty ignition coils, if it's misfiring on bank 1 it can cause the P0420 converter code. I would resolve the misfire issue, then clear the codes and see if the converter code comes back.