Chevy Trax P0420: Catalyst System Efficiency → Below Threshold → Bank 1


Chevy Trax P0420 Diagnosis


This page was created to assist you in troubleshooting the problem. Chevy Trax P0420 trouble code. The P0420 definition, symptoms, causes and potential solutions are covered. OBDII P0420 often occurs with the Trax bad oxygen sensorThere are many other reasons. It can be costly to rush to replace the O2 sensor.  P0420 OBDII is the most popular code.


Índice de Contenido
  1. Chevy Trax P0420 OBDII Code Defined
  2. Chevy Trax P0420 Code Symptoms
  3. Top Causes and Solutions of P0420 on the Chevy Trax
    1. Oxygen Sensor
    2. Catalytic Converter
    3. The O2 Sensor Wiring
    4. Timing
    5. Check for Leakage
    6. Sensor to measure engine temperature
  4. Conclusion

Chevy Trax P0420 OBDII Code Defined

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

Low Catalyst System Efficiency

At least two oxygen sensors are installed in your Trax, one just before the converter and another after it. 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 vehicle will soon turn on the service engine (P0420).

These readings shouldn’t match, since the catalytic converter is supposed to be scrubbing the exhaust. The software on your Trax will determine if the readings match.


Chevy Trax P0420 Code Symptoms

P0420 Chevy Trax

A Chevy Trax'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. Most people will notice the light at the top of the engine.

If you are assigned code P0420, these are common symptoms.

  • Fuel Efficiency- 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 Trax P0420 code.

Similar to P0442 Chevy Trans


Top Causes and Solutions of P0420 on the Chevy Trax

You can have the P0420 Trouble Code in your Trax from many different things. These are some of the more common.

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.


Oxygen Sensor

When the readings of both the exhaust oxygen sensors have similar readings, the P0420 code is thrown. An oxygen sensor that is defective can trigger the code by giving a false reading. 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).

How to Test an O2 and Oxygen Sensor (YouTube)

New Oxygen Sensor – Chevy Trax (Amazon)


Catalytic Converter

A catalytic converter is responsible for scrubbing out as much pollution as possible from the Trax’s exhaust. They can get clogged over time. Even though modern catalytic convertors are designed to last the lifespan of vehicles, it is possible that there may be an underlying issue.

You can test your catalytic converter in just 15 minutes (YouTube)


The O2 Sensor Wiring

Oxygen sensor wiring can become damaged over time. Because it's right beside the exhaust, oxygen sensor wiring can become extremely volatile. Because it is far away from the ECM, the downstream oxygen sensor wiring can also be volatile. (More distance = greater chance of failure).

You can test wiring in under an hour (2 Auto Pros)



The P0420 registration code can be caused by a Trax that is not firing properly or an incorrect exhaust timing.

Check for Leakage

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. The O2 sensor could be thrown if the mixture of fuel and oil is too rich.



You will be able to determine the cause of P0420 in your Chevy Trax. Please feel free to leave a comment or message. We are grateful.

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