Chevy Corvette OBDII Code Diagnosis

P0420 Chevy Corvette

This page was created to assist you in troubleshooting the problem. Chevy Corvette P0420 trouble code. This article covers Chevy Corvette OBDII P0420 symptoms, causes and potential solutions. OBDII P0420 occurs in Corvettes due to a poor oxygen sensor. But there may be other reasons.

The P0420 is one of the most frequent trouble codes for all Chevy cars. The code refers to a number you receive when your Chevy Corvette 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 Corvette OBDII code P0420
  2. Chevy Corvette P0420 code Symptoms
  3. The Top Reasons for P0420 in Chevy Corvette
  4. Possible Solutions for Chevy Corvette Code P0420

Chevy Corvette OBDII code P0420

ChevyP0420 Code Symptoms

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

The Catalyst Systems Efficiency is Below the Threshold

At least two oxygen sensors are installed in your Corvette, one just before the converter and another after it. 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 Corvette P0420 code Symptoms

ChevyP0420 OBDII Trouble Code

If your oxygen sensor isn't working correctly, the P0420 code on a Chevy Corvette may be displayed. 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- 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 Code Chevy Corvette P0420.


The Top Reasons for P0420 in Chevy Corvette

OBD2 Code P0420 Chevy

P0420 can be caused by many factors. Below are the top three most frequent.

  • 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 Corvette’s exhaust. They can get clogged over time. Modern catalytic converters should last for the lifetime of most cars, but clogging can indicate a deeper problem.
  • O2 Sensor Connectivity– 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).
  • Corvette Timing– If your Corvette 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 O2 sensor to see an exhaust that is out of normal range. This could result in the sensor being thrown.


Possible Solutions for Chevy Corvette Code P0420

Often, P0420 can be caused by an 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. Below are some good guidelines to assist you in this task.


It's your job to figure out the problem with your Chevy Corvette. Please let us know if you find any errors or suggestions to improve this article. We are grateful.

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