2001 Nissan Maxima with 150K miles, P0430 code

CEL is on in my 2001 Nissan Maxima. Code from a homeowner scanner reads P0430…bank 2. I read on line this could be the downstream 02 sensor or the catalytic converter. Car rides fine and gets great gas mileage. Any suggestions on which it is? I’d assume change the 02 sensor first since it’s the most economical…just hate to waste the money if that’s not it. Thanks in advance.

The DTC P0430 means the catalytic converter is no longer doing its job.

The down-stream O2 sensor monitors the catalyst efficiency.

If there’s no code for the down-stream O2 sensor, don’t kill the messenger because you don’t like the news.


There are far more possible causes of the P0430 code than just a bad cat.

The causes can be;

Faulty Three-way Catalyst Converter
Bank 2 Exhaust Tube Intake Air Leaks
Faulty Oxygen (O2) Sensor
Faulty Fuel injector(s)
Leaking Fuel Injector (s)
Faulty Spark plugs
Improper Ignition Timing
Faulty Engine Control Module (ECM)
Dirty Air Filter

If your homeowner scanner can read data as the car is running, look at long term fuel trims for bank 2. Are they double digit negative? But bank one is single digits. That could point to a leaking injector that could set a P0430. LTFT OK, look for exhaust leaks.

If you can plot the rear O2 senor on a graph, watch how it switches high to low. It should be switching quickly. A failing O2 sensor will be lazy and switch slowly and won’t set a code for a failed O2 sensor. You might see a P0139 or P0159 for slow or lazy sensor but the P0430 may set first.

Work your way through all the possibilities to eliminate the causes one by one. What is left is the culprit.


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