Diagnostics and Meaning for the P0420 Chevy Malibu OBDII code

P0420 Chevy Malibu

This page was created to assist you in troubleshooting the problem. Chevy Malibu P0420 trouble code. This article covers Chevy Malibu OBDII P0420 symptoms, causes and potential solutions. OBDII P0420 in the Malibu is usually caused by a defective oxygen sensor. However, there are other possible causes.

The P0420 is one of the most frequent trouble codes for all Chevy cars. This is the code that you get when you connect your Chevy Malibu to an OBDII scaner. It doesn’t matter which model you have, this OBDII code has the same meaning for all of them.


P0420: Catalyst System Efficiency Lower Than Threshold


Índice de Contenido
  1. Chevy Malibu P0420 OBDII Code Defined
  2. Chevy Malibu P0420 Code Symptoms
  3. Here are the Top 5 Reasons Why P0420 is a Problem in Chevy Malibu
  4. Possible Solutions for Chevy Malibu P0420 Code

Chevy Malibu P0420 OBDII Code Defined

ChevyP0420 Code Symptoms

P0420 This is an OBDII Trouble Code. This code is technically:

The Catalyst Systems Efficiency is Below the Threshold

There are at most two oxygen sensors in the Malibu. One is before the catalytic converter, and one after. One of their many duties is to determine the level of emissions coming into and out the converter.

If the downstream and upstream oxygen sensors give similar readings, then the vehicle will soon turn on the service engine (P0420).

Your vehicle's software believes the catalytic convert is not doing its job.

If your vehicle has the P0420 code, it won’t pass emissions so please be aware of that.

Chevy Malibu P0420 Code Symptoms

ChevyP0420 OBDII Trouble Code

If your oxygen sensor is not working correctly, the P0420 code on a Chevy Malibu may be displayed. In most cases, the code will trigger the oxygen sensor that is upstream of the converter.

There aren’t usually any drivability issues associated with P0420. The first indication that something is amiss is usually the soon-light coming on in the service engine.

These are some of the symptoms you should look out for if your code is P0420.

  • Mileage- It is possible for your catalytic converter to become clogged.
  • Perilous times for Power– It is a really strange feeling to drive a vehicle with a catalytic converter that is going out. Typically, they’ll idle ok and drive normal under a light load. Whenever the engine is put under a heavy load it’ll feel like it is running out of gas. It’s very similar to the symptoms of a bad fuel filter.
  • Service Engine Light– Often, this is the only symptom of the Chevy Malibu P0420 code.


Here are the Top 5 Reasons Why P0420 is a Problem in Chevy Malibu

OBD2 Code P0420 Chevy

You can have the Malibu's P0420 code problem for many reasons. Below are the top ones.

  • Oxygen Sensor– The P0420 codes is thrown when the oxygen sensors on both sides of the exhaust have very similar readings. If the oxygen sensor fails, the code can be triggered. If the engine does not exhibit any of the decreased performance associated with a bad catalytic converter, it very well may be the oxygen sensor (if you haven’t noticed the performance loss yet).
  • Catalytic Converter– A catalytic converter is responsible for scrubbing out as much pollution as possible from the Malibu’s exhaust. They can get clogged over time. Modern catalytic converters should last for the lifetime of most cars, but if they have become clogged, there could be an underlying issue.
  • O2 Sensor The wiring– Over time, the oxygen sensor wiring can go bad. Because it's right beside the exhaust, this wiring is extremely volatile. It is more distant from the ECM which makes it even more volatile.
  • Spark Timing– If your Malibu is misfiring or the exhaust timing is off, this can affect the gasses that are actually going to the O2 sensors enough to cause the P0420 code to register.
  • Exhaust Leak– If there’s a noticeable exhaust leak coming from the vehicle it can change what the O2 sensors register enough to throw the P0420 code.
  • Motor Temp Sensor– If the computer doesn’t know what the engine temp is it’ll keep the fuel mixture rich. The O2 sensors will not see the mixture richly and could cause it to throw its sensor.


Possible Solutions for Chevy Malibu P0420 Code

The oxygen sensor often causes P0420. Specifically it’ll usually be the O2 sensor(s) on the upstream side of the catalytic converter.

But, don’t be surprised if it’s not. You should check your exhaust first for any leaks. It should be possible to detect an exhaust leak underneath the vehicle.

Unless you have an exhaust leak, you’ll probably need to test the O2 sensors and/or catalytic converters. Below are some good guidelines to assist you in this task.


You will be able to solve the problem with your Chevy Malibu by using these tips. Please let us know if you find any errors or suggestions to improve this article. We are grateful.

Other Common Malibu OBDII Codes:  P0171 Chevy Malibu: Fuel Trim System Lean Bank 1, P0700 Chevy Malibu Code: Transmission Control System Malfunction

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