code p0420

I believe there's a firmware update for this that you're Nissan dealer can install. Or, you can just reset the ECM and see if it comes back.

Where did you buy the reader? How much? (Sorry for going off topic).

-- Mr. Rajendra Singh

If you live in California: The ECM monitors the switching frequency ratio of front and rear heated oxygen sensors.

A warm-up three way catalyst with high oxygen storage capacity will indicate a low switching frequency of rear heated oxygen sensor. As oxygen storage capacity decreases, the rear heated oxygen sensor switching frequency will increase.

When the frequency ratio of front and rear heated oxygen sensors approaches a specified limit value, the warm-up three way catalyst malfunction is diagnosed.

Malfunction is detected when warm-up three way catalyst does not operate properly, warm-up three way catalyst does not have enough oxygen storage capacity.

Possible Cause

Warm-up three way catalyst Exhaust tube Intake air leaks Injectors Injector leaks Spark plug Improper ignition timing

There is a replacement 3 way cat and ecm reprogram 8/80 under warranty, may also need H2S1 B1 sensor replaced