Code P0420 2005 Nissan Altima

2005 Nissan Altima Code P0420I have a 2005 Nissan Altima 2.5l 4 cylinder and Service Engine Soon light is on and ran code. It is Code P0420 with catalyst below threshold bank 1. Now my car revs at high rpms but I am not loosing gas or mileage or performance. My question is do I replace the catylitic converter or could I just do a tune up for now because the catalytic converter is not cheap.?


The most common fix for this code is to replace the catalytic converter. There is a chance that the O2 Sensor is sticking and sending a false signal, but not as common. There is no reason to replace the catalytic converter at all when it comes to drivability. The converter is installed as part of a government mandated regulation. The catalytic converter reduces emissions. You could effectively never replace the converter and not worry about the performance of your car.  Now with that said, if the vehicle has less than 75,000 miles the converter is covered under warranty and up 100,000 miles on newer vehicles. The warranty coverage is also a government mandated law.

NISSAN Code P0420 – Catalyst System Efficiency Below Threshold Bank 1

As the code description implies the P0420 code means that the vehicle’s control module has detected that the three-way catalytic converter is not working properly (is not as efficient as the factory is expecting). Replacing the oxygen (O2) sensors may sometimes fix the code, but in most cases the catalytic convert needs to be replaced to fix the problem. If the P0420 code is combined with other codes, try fixing the other codes first.

There is a Technical Service Bulletin for this also. it calls for reprogramming the ECM.

Nissan Code P0420 Possible causes

– Three way catalyst converter Bank 1
– Exhaust tube
– Intake air leaks
– Fuel injectors may be faulty
– Fuel injector leaks
– Spark plugs may be faulty
– Improper ignition timing
– Engine Control Module (ECM)