Diagnose and meaning of the OBDII Code P0420 Chevrolet Equinox

P0420 Chevy Equinox

This page was created to assist you in troubleshooting the problem. Chevy Equinox trouble code P0420. The Chevy Equinox P0420 definition, symptoms, causes, as well as possible solutions is covered. OBDII P0420 can often be caused by a defective oxygen sensor in Equinox. However, other reasons may also exist.

P0420 is a common code for Chevy vehicles. The P0420 code is the number given to your Chevy Equinox when it's plugged in to 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 Equinox P0420 OBDII Codified
  3. Chevy Equinox Code Symptoms
  4. The Top Reasons for P0420 in Chevy Equinox
  5. Possible Solutions for Chevy Equinox Code P0420

Chevy Equinox P0420 OBDII Codified

Chevy P0420 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 on your Equinox. One is before and one after the catalytic convertor. One of their many duties is to determine the levels of emissions coming into and out the converter.

If the downstream and upstream oxygen sensors give similar readings, then the service engine will be thrown out (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 Equinox Code Symptoms

Chevy P0420 OBDII Trouble Code

A Chevy Equinox's P0420 code will indicate that your oxygen sensors have stopped working properly. In most cases, the code will trigger the oxygen sensor before 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- You may or not experience any problems depending on the extent of catalytic conversion blockage.
  • 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 Equinox code P0420.


The Top Reasons for P0420 in Chevy Equinox

OBD2 Code P0420 Chevy

The P0420 Trouble Code in Equinox can be caused by many factors. These are some of the more common causes.

  • 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.  It is possible that the engine may not be experiencing the reduced performance caused by a poor catalytic converter. 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 Equinoxs exhaust. These converters can become blocked over time. Even though modern catalytic convertors are designed to last many years, there could still be an underlying issue if they have become clogged.
  • O2 Sensor The wiring– Over time, the oxygen sensor wiring can go bad. This is because it is directly next to hot exhaust. Because it's so far away from the ECM, downstream oxygen sensor wiring can be volatile (more travel).
  • Spark Timing– If your Equinox 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.
  • Sensor to measure engine temperature– 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 O2 sensor to see an exhaust that is out of normal range. This could result in the sensor being thrown.


Possible Solutions for Chevy Equinox 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. Checking the exhaust for signs of leakage is a smart idea. 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. Below are some good guidelines to assist you in this task.


It's your job to find the root cause of the problem with your Chevy Equinox. Please let us know if you find any errors or suggestions to improve this article. Many thanks.

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