P0420 Nissan – Causes and How To Fix The Error Code

Clyde Goering Image
Written by Clyde Goering

May 6, 2020

P0420 Nissan

P0420 Nissan OBDII Code Defined

The code PO420 OBDII is a generic code. It’s generic since it affects all vehicles from the 1996 models and newer ones. But the repair steps vary, and for our case, we will focus on the Nissan car.

Car diagnotic tool scanner

P0420 Nissan code usually indicates that the catalytic converter is not performing its functions well. This converter is responsible for breaking down the harmful pollutants to harmless gases. The toxic pollutants result from the combustion cycles of the Nissan. Therefore, the code means that there is an increase in the release of harmful contaminants from your car.

Besides this code, there are other popular ones, i.e., PO171, P0300, PO442, and P0455. Bookmark these codes should in case you encounter additional problems in the future.

What Does P0420 Mean for Your Nissan?

The code P0420 simply means that the control module of your vehicle is not functioning or is less efficient in its functions. It’s a common problem with most Nissan models.

A P0420 Nissan code indicates a problem with the catalytic converter. The work of the catalytic converting is breaking down the harmful pollutants released from the combustion processes. The catalytic converter uses gold meshes and fine platinum to lower the number of emissions that are expelled via the exhaust pipe.

This catalytic converter comes with two oxygen (O2) sensors. One sensor is in the front (upstream)of the converter, while the other is located in the rear (downstream).

When the upstream O2 sensor is performing its functions well, then there should be a fluctuation of the readings when your vehicle is in the average operating temperature and when it’s operating in closed loops. If the rear O2 sensor is working efficiently, and the catalytic converter has no issue, then there should be steady readings.

When both O2 sensors have the same readings, it usually means that the catalytic converter is not performing well. If the voltage reading in the rear oxygen sensor goes down and begins to vary like the front oxygen sensor, then there are too high levels of oxygen, and the Powertrain Control Module (PCM) triggers the P0420 Nissan trouble code. The code turns on the engine light.

Top Causes of P0420 Nissan

  1. Faulty Oxygen Sensors
  2. Dirty Air Filter
  3. Leaks in The Exhaust System
  4. Wearing Out and Internal Failures of the Catalytic Converter
  5. Leaking Fuel Injector (S)
  6. Faulty Control Module (ECM)
  7. Faulty Spark Plugs
  8. An issue in one or more fuel Injectors
  9. Muffler Leaks or Damage
  10. Fuel Injector Leak
  11. Defective Rear or Front O2 Sensors
  12. Higher Than the Normal Fuel Pressure

When does the Nissan detect the P0420 code?

P0420 Nissan means Catalyst System Efficiency Below Threshold (Bank 1). The vehicle detects the error when:

  1. When the catalyst (three-way) converter bank (1) is not operating properly
  2. When the catalyst (three-way) converting bank (1) doesn’t have enough storing capacity for the oxygen

Nissan Code P0420 Common Diagnosis Mistakes

More often, other codes come with the P0420 one, and don’t forget to check them. These include the codes P0300, P0302, P0304, P0305, P0307, P0174, and P0171. These codes may also indicate false readings, which creates the perfect condition for triggering the P0420 code. In case there are other codes, then address them first.

How do I fix code P0420, Nissan?

There are many possible solutions for fixing or troubleshooting this error. They include:

  1. Checking for any exhaust leaks at the pipes, manifold, catalytic converter and repairing the damaged parts
  2. Using a scope for diagnosing the oxygen sensors (Tip: The oxygen sensor located at the front of the catalytic converter usually features a fluctuating waveform. On the other hand, the sensor located at the back of the converter should have a steady waveform). Check the downstream heated oxygen sensor and replace it when necessary. You can also install another catalytic converter.

Cost of diagnosing the P0420 Nissan code

The cost of diagnosis of the code varies between different garages around the same city and even country. But they compute the prices per hour. But the average charges for this service is $75 to $150 hourly.

Since different factors can cause the code, the mechanic of an auto repair shop has to take the time to diagnose the vehicle to find the trigger behind the issue.

Once he diagnoses your problem, the mechanic will hand you a quote for fixing the issue and other information you’ll need for P0420 Nissan.

P0420 Nissan Diagnosis

  1. Check the Nissan to see whether there are other codes besides the P0420. In case there are different codes, then address them first.
  2. Check the exhaust system for any leaks or damages. Monitor the gaskets, exhaust manifold, and exhaust pipes pre-catalytic converter closely. In case of any leaks, fix the leaks, clear the code then do some drive cycles to ascertain whether what you tried fixed the issue.
  3. As soon as you keep the Nissan running and it’s at its average operating temperature, check the amount of voltage in the downstream O2 sensor by using a digital multimeter. The downstream O2 sensor usually displays a voltage of about 0.45V when the catalytic converter is at its optimum functioning. On the other hand, If the voltage of this sensor keeps changing from 0.1 V to 0.9V, then the catalyst is damaged, and you’ll have to replace the catalytic converter.

Tools Needed to Diagnose P0420 Nissan:

  • OBD2 Code Scanner: Onboard Diagnostics 2 (OBD2) is a self-diagnostic standardized system that is used in cars and trucks. The OBD2 software monitors and regulates your car’s functions. It can relay commands to various systems to ensure your car’s overall health is well-maintained. Besides, it can also correct the anomalies in vehicle ignition and fuel mixture by itself.
  • Digital multimeter: A digital multimeter is a testing tool that measures the electrical values (2 or more)- usually voltage, current, and resistance. Most electricians use it as a diagnostic tool in their distinct industries.

The P0420 Nissan issue is one of the most common, which affects Nissan cars and other models too. Knowing how to solve the problem is crucial as it’ll enable you to make your vehicle long-lasting and also to protect others from dangerous pollutants.

Clyde Goering Image
Written by Clyde Goering


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