In this article we will learn about P0420 code. We will also learn causes, symptoms and how to fix this error code.
Table of Contents
What Is P0420 Code?
The P0420 code is a diagnostic trouble code that signals a low catalyst system efficiency in a vehicle. The catalytic converter is an essential component of the vehicle’s exhaust system and is responsible for converting harmful pollutants, such as unburned fuel and carbon monoxide, into less harmful substances.
To ensure that the catalytic converter is functioning properly, the vehicle is equipped with two oxygen sensors – one located upstream of the converter and one located downstream. These sensors measure the level of oxygen in the exhaust and compare the readings to determine if they’re within the desired range. If the readings are not within the desired range, it may indicate a problem with the vehicle’s exhaust or fuel systems.
In such cases, the Powertrain Control Module triggers the P0420 code and turns on the check engine light to alert the driver of the issue.
The P0420 code can be a tricky diagnosis, and it’s best to seek the assistance of a professional mechanic to accurately diagnose and resolve the issue.
If your vehicle’s check engine light comes on and displays a P0420 code, it’s a clear indication of a low catalyst system efficiency and a problem with the vehicle’s exhaust or fuel systems.
To ensure the issue is resolved correctly, it’s recommended to seek the assistance of a professional mechanic.
Causes
The P0420 code can be caused by a variety of factors, including a faulty catalytic converter, damaged oxygen sensors, leaks in the exhaust system, improper muffler deletions, incorrect placement of the catalytic converter, and issues with wiring or sensors.
Other potential causes include a rich or lean air-to-fuel ratio, damaged engine components, engine misfiring, higher than normal fuel pressure, and contamination in the catalytic converter oil.
Symptoms
- Check engine light illumination – The check engine light will come on when the fault code is detected.
- Rotten egg smell – A bad smell like rotten eggs may come from the exhaust pipe, indicating a problem with the catalytic converter.
- Reduced engine power – The vehicle may experience reduced engine power, making it difficult to accelerate or travel at speeds above 30-40 mph.
- Rough idle – The engine may run roughly and misfire, leading to a hard shifting and truncated driveability.
- Increased fuel consumption – The vehicle may consume more fuel than usual due to the decreased engine performance.
- Sulfur smell – There may also be a smell like sulfur or rotten eggs coming from the exhaust pipe.
- Inability to accelerate quickly – The vehicle may have difficulty accelerating quickly due to reduced engine power.
How To Fix
To fix the P0420 code, the first step is to ensure that it is the only engine code present.
Then, clear the code and take a test drive for about 15 minutes. If the code returns after the test drive, repeat the process several times to confirm the issue.
Next, inspect the exhaust system for any signs of damage, holes, rust, or leaks, including the exhaust manifold which is a common source of leaks. Check the voltage readings from the O2 sensor. The readings should be between 0.4 to 0.5 volts on most engines.
If the readings are significantly off or fluctuating, it may indicate a problem with the catalytic converter.
In some cases, minor engine problems can cause fault codes to appear randomly, and clearing and deleting the code may resolve the issue.
However, if the P0420 code persists, it is necessary to identify the root cause of the problem. The steps outlined above can help diagnose issues with exhaust leaks and cat failure.
If there are additional engine codes present, a more in-depth problem-solving approach may be required to find the source of the issue.
FAQS
What is P0420 code?
It’s a code indicating low catalyst system efficiency.
Causes of P0420?
Bad converter, clogged air filter, vacuum leak, or faulty O2 sensor.
How to fix P0420?
Identify and address the root cause, e.g. replace faulty converter or fix vacuum leak.
Is P0420 serious?
No, it affects performance and fuel efficiency but not immediate harm.
Can I drive with P0420?
Yes, safe to drive, but repair as soon as possible.
How long to fix P0420?
Varies, from a few hours to a day, depending on root cause.
Will P0420 affect emissions test?
Yes, it indicates a problem with emissions control system.
Can P0420 be reset?
Yes, by clearing vehicle computer, but likely reappear if not fixed.
Cost to fix P0420?
Ranges from a few hundred to a few thousand dollars.
Can I diagnose P0420 myself?
Yes, with a basic OBD-II scanner, but professional help is recommended.