P0420 NISSAN - Catalyst System Efficiency Below Threshold Bank 1

The function of the catalytic converter is to break down harmful pollutants that are created by your Nissan during the combustion cycle and convert them into harmless gases. Code P0420 indicates that the catalytic converter is not functioning efficiently, therefore increasing the output of harmful pollutants by your Nissan.

P0420 Nissan What causes the code?

1. Faulty Three-way Catalyst Converter Bank 1 
2. Exhaust Tube 
3. Leak in exhaust system
4. Faulty Oxygen (O2) Sensor 
5. Faulty Fuel injector(s) 
6. Leaking Fuel Injector (s) 
7. Faulty Spark plugs 
8. Improper Ignition Timing 
9. Faulty Engine Control Module (ECM) 
10. Dirty Air Filter

P0420 Nissan Fault Code Related Video 

P0420 Nissan Tech notes 

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.

p0420 Nissan When is the code detected? 

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

Nissan P0420 Symptoms

• Check Engine Light is on
• Lack of power from the engine
• Decreased fuel economy
• Rotten egg or sulfur smell

P0420 Nissan Description 

The Engine Control Module (ECM) monitors the switching frequency ratio of heated oxygen sensors 1 (front O2 sensor) and heated oxygen sensors 2 (rear O2 sensor). 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 malfunction is diagnosed.

Nissan P0420 Diagnosis

Scan your Nissan to verify P0420 is the only code present. If other codes are present, they must be addressed first.

Examine the exhaust system for damage and leaks. Pay close attention to the exhaust manifold, gaskets, and exhaust pipes pre-catalytic converter. If any leaks are found, repair the leak, clear the code, and complete several drive cycles to verify that was the fix.

With the Nissan running and at normal operating temperature, use the digital multimeter to check the voltage reading of the downstream O2 sensor. The downstream O2 sensor produces a relatively steady voltage reading of approximately 0.45V if the catalytic converter is functioning properly. If the voltage of the downstream O2 sensor is constantly jumping between 0.1V and 0.9V, the catalyst is worn and the catalytic converter needs to be replaced.