Symptoms

- Engine Light ON (or Service Engine Soon Warning Light)

Possible Causes

- Three way catalyst converter Bank 2 - Engine Control Module (ECM) Program - Exhaust tube - Intake air leaks - Fuel injectors may be faulty - Fuel injector leaks - Spark plugs may be faulty - Improper ignition timing - Engine Control Module

When Detected

- Three way catalytic converter Bank 1 does not operate properly. - Three way catalyst converter Bank 1 does not have enough oxygen storage capacity.

Tech Notes

Very common problem with Nissan vehicles. There are a few Nissan bulletins regarding the P0420 code. 2001 Nissan Frontier Service Bulletin P0420 OBDII Code 2001 Nissan Xterra Service Bulletin P0420 OBDII Code

Description

The ECM monitors the switching frequency ratio of heated oxygen sensors 1 and 2. A three way catalyst converter(Manifold) with high oxygen storage capacity will indicate a low switching frequency of heated oxygen sensor 2. As oxygen storage capacity decreases, the heated oxygen sensor 2 switching frequency will increase. When the frequency ratio of heated oxygen sensors 1 and 2 approaches a specified limit value, the three way catalyst (Manifold) malfunction is diagnosed.