P0420 Chevy Cruze: The Catalyst System Efficiency is Below the Threshold

P0420 Chevy Cruze

This page will help you to troubleshoot your problem. Chevy Cruze P0420 trouble code. This article covers Chevy Cruze P0420 symptoms, causes and potential solutions. The most common cause of the Cruze's P0420 is a defective oxygen sensor. However, there are other possible causes.

The P0420 is one of the most frequent trouble codes for all Chevy cars. The P0420 code refers to a number you receive when your Chevy Cruze is plugged into an OBDII scanner. 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 Cruze P0420 OBDII Code Defined
  2. Chevy Cruze P0420 Code Symptoms
  3. Here are the Top 5 Reasons P0420 is in Chevy Cruze
  4. Possible Solutions for Chevy Cruze Code P0420

Chevy Cruze P0420 OBDII Code Defined

Chevy P0420 Code Symptoms

P0420 It is also an OBDII trouble code. This code is technically:

Low Catalyst System Efficiency

There are at least two oxygen sensors on your Cruze. One is before and one after the catalytic convertor. 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 Cruze P0420 Code Symptoms

Chevy P0420 OBDII Trouble Code

If your oxygen sensor isn't working correctly, the P0420 code on a Chevy Cruze may be misinterpreted. In most cases, the code will trigger the oxygen sensor before the converter.

There aren’t usually any drivability issues associated with P0420. Most people will notice the light at the top of the 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.
  • The loss of 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 Cruze P0420 code.


Here are the Top 5 Reasons P0420 is in Chevy Cruze

OBD2 Code P0420 Chevy

You can have the Cruze's P0420 trouble code. There are many reasons. These are some of the more common.

  • Oxygen Sensor– The P0420 codes is thrown when the oxygen sensors on both sides of the exhaust have very similar readings. An oxygen sensor that is defective can give false readings and cause the code to 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 Cruzes 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 Connectivity– Over time, the oxygen sensor wiring can go bad. Because it's right beside the exhaust, this wiring is extremely volatile. Because it's so far away from the ECM, downstream oxygen sensor wiring can be volatile (more travel).
  • Spark Timing– If your Cruze 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. If the fuel mixture becomes too rich it will cause the exhaust that the O2 sensors can see to be out of range, which could result in the sensor being thrown.


Possible Solutions for Chevy Cruze Code P0420

P0420 is often caused by the oxygen sensor. 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. An exhaust leak should sound easily beneath the car.

Unless you have an exhaust leak, you’ll probably need to test the O2 sensors and/or catalytic converters. These are some great guides that will help you.


It's your job to figure out the cause of P0420 in your Chevy Cruze. Please let us know if you find any errors or suggestions to improve this article. We are grateful.

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