Dodge Ram P0420: Catalyst System Efficiency → Below Threshold → Bank 1

This page will help you to troubleshoot your problem. Dodge Ram P0420 trouble code. This article covers Dodge Ram P0420 symptoms, causes and potential solutions. OBDII P0420 in the Ram is usually caused by an oxygen sensor problem, although there are other possible causes. It can be costly to spend your time replacing the O2 sensor.

Dodge Ram P0420 Diagnosis


A very common trouble code, P0420. The code refers to a number you receive when your Dodge Ram 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 (1996+)


Índice de Contenido
  1. Dodge Ram P0420 OBDII code Defined
  2. Dodge Ram P0420 Code Signs
  3. Here are the Top 10 Reasons Why Dodge Rams Have P0420
  4. Possible Solutions for Dodge Ram P0420 code

Dodge Ram P0420 OBDII code Defined

Ram P0420 Code Symptoms

P0420 This is an OBDII Trouble Code. Technically, the code stands for:

Low Catalyst System Efficiency

There are at most two oxygen sensors on your Ram. 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 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 Ram will determine if the numbers match.


Dodge Ram P0420 Code Signs

P0420 Dodge Ram

A malfunctioning oxygen sensor can cause the Dodge Ram's P0420 code to appear. 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.

  • Fuel Efficiency- 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 Dodge Ram P0420 Code.

Similar: P0442 Dodge Ram


Here are the Top 10 Reasons Why Dodge Rams Have P0420

You can have the Ram P0420 trouble code 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. 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 Ram’s exhaust. These can get blocked 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.
  • Connecting O2 Sensors– Over time, the oxygen sensor wiring can go bad. This is because it is directly next to hot exhaust. It is volatile because it is further from the ECM.
  • Ram Timing– If your Ram 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.
  • Engine Temperature 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 Dodge Ram P0420 code

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. 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. These are some great guides that will help you.

You will be able to determine the cause of P0420 in your Dodge Ram. You can comment on the article or send a message if there are inaccuracies or any suggestions. We are grateful.

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