Code P0430

You mean 420, right? Change the rear O2 sensor first.

P0430 (Left Bank, -B2) Three Way Catalyst function for 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 valiue, the warm-up three way catalyst malfunctoin is diagnosed.

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

Possible cause:

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

Hope this helps.

depending on your mileage and in service date, if the cat is judged to be bad it would be covered under warranty

Dealer replaced the cat under warranty. Thanks for the help.