Nissan Repair Questions? Ask a Mechanic for Answers ASAP
Hey there, thanks for the question.
are you saying you got these codes immediately after replacing the cats?
no, not true. If the hi flow catalysts were going to be an issue you would have seen it within 20 miles of driving.
the catalyst inefficiency codes are picked up when the rear sensor is essentially mimicking the front sensors readings instead of the catch and release fluctuations you generally see from a working catalyst.
The fact that you have a/f sensor codes and catalyst codes on both banks, tells us you could fuel trim issues
is the vehicle running poorly?