If you own a Subaru and have seen the check engine light illuminate on your dashboard, you may have come across the P0420 code. This is one example of engine codes that indicates an issue with the catalytic converters and can cause vehicles to fail an emissions test.
This article will decode the P0420 code in Subaru and explore its potential causes and solutions.
Whether you are a seasoned mechanic or a Subaru owner trying to diagnose an issue with your vehicle, this article will provide valuable insights into the P0420 code and how to address it.
Fixing the P0420 Code with Goodhood
Getting stuck somewhere with this trouble code can be frustrating, so it's best to find the right repair shop to help you out.
At Goodhood, we provide comprehensive diagnostic services. Our experienced technicians use state-of-the-art tools and equipment to diagnose your vehicle accurately and efficiently.
Once they identify the cause of the P0420 code in your Subaru, our mechanics can help you understand the necessary repairs and costs.
We will always give you honest advice on the best way to fix your vehicle so that you can get back on the road in no time.
Common Causes of P0420 Code in Subarus
Failed Catalytic Converter
This is responsible for reducing harmful emissions from the exhaust system. If it fails, it can trigger the P0420 code. This can be caused by age, damage, or contamination from other engine or exhaust manifold issues.
Oxygen Sensor Malfunction
The oxygen sensor measures the amount of oxygen in the exhaust stream and provides feedback to the engine control module (ECM) to adjust the fuel-air mixture. If it malfunctions, it can cause the ECM to misinterpret the data and potentially trigger the P0420 code.
Engine Misfire or Running Rich
An engine misfire or running rich (too much fuel in the air-fuel mixture) can cause excess fuel to enter the exhaust system and damage the catalytic converter. This can trigger the P0420 code.
An exhaust leak can cause the P0420 code by allowing excess oxygen into the exhaust stream and disrupting the catalytic converter's ability to reduce emissions.
Malfunctioning EGR System
The EGR system recirculates exhaust gases back into the engine to reduce emissions. It can cause excess emissions and potentially trigger the P0420 code if it malfunctions.
Issues with the Fuel System or Fuel Injectors
Issues with the fuel system, such as a clogged fuel filter or malfunctioning fuel injectors, can cause a rich fuel-air mixture and potentially trigger the P0420 code.
Damaged Wiring or Connectors in the Catalytic Converter or Oxygen Sensor Circuit
Damaged wiring or connectors in both these components can cause issues with the sensors' readings and potentially trigger the P0420 code.
How a Professional Mechanic Diagnoses and Fixes the P0420 Code
Use a Code Scanner
The mechanic will use a code scanner to read the P0420 code and any other related codes that may be present. This will give them an initial indication of where to begin diagnosing the issue.
Inspect the Catalytic Converter
The mechanic will visually inspect the catalytic converter for any signs of damage or contamination. They may also perform a pressure test or temperature test to determine if it's functioning properly.
Check the Oxygen Sensors
The mechanic will check the oxygen sensors for proper functioning and accurate readings. They may perform tests to ensure that the sensors are properly communicating with the engine control module.
Test the Exhaust System
The mechanic will check for any leaks in the exhaust system and ensure that it's properly sealed. They may also inspect the exhaust pipes and muffler for any signs of damage or corrosion.
Check the Fuel System
The mechanic will check the fuel system for proper pressure and ensure that the fuel injectors are working properly. They may also check the fuel filter for any signs of clogs or obstructions.
Inspect the EGR System
The mechanic will inspect the EGR system for any signs of damage or malfunction. They may perform tests to ensure that it's properly recirculating exhaust gases and reducing emissions.
Repair or Replace Components
Based on the results of their diagnostic tests, the mechanic will repair or replace any damaged or malfunctioning components, such as the catalytic converter, oxygen sensors, or EGR system. They may also clean or replace the fuel filter or fuel injectors.
Clear the Code
Once the issue has been addressed, the mechanic will clear the P0420 code and any related codes from the vehicle's memory. They will then test drive the vehicle to ensure that the code does not reappear.
Overall, diagnosing and fixing the P0420 code can be a complex process that requires expertise and specialized tools. It's best to take your Subaru to a professional mechanic if you're experiencing this issue.
The P0420 code is an indicator of a problem with the catalytic converter in your Subaru. Common causes can include failed or malfunctioning components, such as the oxygen sensor, fuel system, EGR system, and exhaust system.
It's best to take your vehicle to a professional mechanic for diagnosis and repairs. At Goodhood, our experienced technicians use state-of-the-art tools and equipment to help you get back on the road quickly.
Frequently Asked Questions
How long does it take to fix the P0420 code?
It depends on the cause of the issue. In most cases, a professional mechanic should be able to diagnose and repair the issue within a few hours.
Is it safe to drive with the P0420 code?
It is not recommended to drive with the P0420 code. The issue can cause your vehicle to fail an emissions test and may result in reduced fuel economy and engine performance. It's best to take your Subaru to a professional mechanic for diagnosis and repairs as soon as possible.
What's the job of the powertrain control module?
The powertrain control module, or PCM, is the computer in your vehicle that controls and monitors the engine's performance. It receives input from various sensors and components to adjust fuel injection, ignition timing, emission control systems, and other parameters as needed. It also stores diagnostic codes when a system fails or malfunctions. The PCM plays a vital role in ensuring that your vehicle runs smoothly and operates safely.
How can a faulty exhaust manifold cause the P0420 code?
A faulty exhaust manifold can cause the P0420 code by allowing excess oxygen into the exhaust stream and disrupting the catalytic converter's ability to reduce emissions. This can also be caused by clogs or leaks in the exhaust system, which a damaged exhaust manifold can cause. A professional mechanic will inspect your exhaust system's manifold and other components for signs of damage or malfunction. They may need to replace any faulty parts to fix the P0420 code.
Can a catalytic converter be repaired?
In some cases, a bad catalytic converter can be repaired. However, in most cases, it's best to replace the catalytic converter if it has failed. A professional mechanic will be able to evaluate the catalyst system's efficiency and provide advice on the best solution for your vehicle.