2001 Nissan Pathfinder Failed emmisions test

My pathfinder failed an emmisions test with the following codes:
p0420 - Catalyst System efficiency below threshold (Bank 1)
p0430 - Catalyst System efficiency below threshold (Bank 2)
I believe this might be referring to oxygen sensors but dont know for sure. If it is is there anyway from the above code to know which ones need replacing. I think my vehicle has (4) 2 upstream which are under the engine which I can see and I believe 2 downstream on the outflow of the exhaust system. These are expensive enough anyway and only want to replace the necessary ones. Also I had a friend tell me not to replace them but to clean them with brake cleaner and they would be fine. Is this true or would that be a waste of time.
Do you
have the same problem?
Monday, January 16th, 2006 AT 2:07 PM

1 Reply

Nissan Pathfinder DTC P0420 And P0430

Q. Hello Vincent! I have a:
2001 Nissan Pathfinder 4WD
3.5 liter V-6
Automatic transmission
87,000 miles
fuel injected
ABS brakes
P/S, A/C, Cruise Control
Rack and pinion steering

The service engine soon light has come on recently. I brought the car to a local repair shop and the codes came up as P0420 and P0430. After looking at my car, the technician told me that these codes are basically saying that both my catalytic converters are bad. However, he said that this is rare and that all the oxygen sensors were functioning properly.

He cleared the code out of the computer and told me to keep driving and see if it comes back on. He said it may have been a fluke caused by bad gas or something of that nature. He did say that if the light did come back on it more than likely was the mass air flow sensor.

This morning the service engine soon light came back on. I went to Autozone to scan the codes and the same ones as before appeared, P0420 and P0430.

Does this sound correct to you? I have been doing some reading and I am a little skeptical. I know these sensors run in the $250 range and just want to be sure before I buy one and replace it myself. How much damage can be done if this does not get repaired?

Don't know if this has anything to do with the problem but I did have the rear muffler replaced recently because it had rotted along the flange. I would appreciate your advice.

Thank you,

A. DTC P0420 and P0430 indicate a possible problem with the Three Way Catalytic Converters (TWC). It is possible that an overly rich fuel mixture will damage both TWCs, but other than that I find it difficult both TWCs went bad, under normal conditions, at the same time.

There is a TSB on this problem.

Classification: EC02-020a
Reference: NTB02-087a
Date: January 22, 2003

2001 Pathfinder MIL "ON" With DTC P0420/P0430 Bank-1/Bank-2 Catalyst


"Chart A" was revised by changing the "Built from" date to 8/2/00 instead of 8/2/02.
Please discard previously distributed copies of NTB02-087. Use this bulletin NTB02-087a for complete information.
2001 Pathfinder (R50)

If an applied 2001 Pathfinder has a MIL "ON" and either or both of the following DTCs stored in the ECM:

Use the appropriate Service Procedure steps to determine if the bulletin applies to this vehicle. If the bulletin applies, complete the applicable Service Procedure steps to repair the incident, if it should occur.

You will perform the following, as required:

Determine the DTC Stored in the ECM from the CONSULT-II Self-diagnosis results.
ECM Part Number Check to determine if this bulletin applies.
ECM Reprogramming (required if the ECM P/N in the vehicle matches one of those listed under "Current ECM P/N" in Chart A).
IMPORTANT: Do NOT replace the catalytic converters as part of this procedure.

So I would wander into your Nissan Dealer and confirm this TSB applies to your vehicle and have the ECM reprogramming done. Hell of a lot cheaper than replacing both catalytic converters or a Mass Air Flow sensor.

Additional Information provided courtesy of AllDATA

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© 2006 Vincent T. Ciulla
by Vincent Ciulla
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