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

This page was created to assist you in troubleshooting the problem. Dodge Journey P0420 trouble code. The article discusses Dodge Journey P0420 causes, meaning, and possible solutions. OBDII P0420 in Dodge Journey 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 Journey P0420 Diagnosis


The most common trouble code is P0420. The code refers to a number you receive when your Dodge Journey 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 Journey P0420 OBDII Codified
  2. Dodge Journey P0420 Code Symptoms
  3. The Top Reasons for P0420 In the Dodge Journey
  4. Possible Solutions to the Dodge Journey P0420 code

Dodge Journey P0420 OBDII Codified

Journey P0420 Code Symptoms

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

Low Catalyst System Efficiency

At least two oxygen sensors are installed on the Journey. One is before the catalytic convertor and one is after. They are responsible for measuring the emission levels entering and leaving 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. If the numbers are consistent, your Journey software believes the catalytic convert is not doing its job.


Dodge Journey P0420 Code Symptoms

P0420 Dodge Journey

A malfunctioning oxygen sensor can cause the P0420 code to appear in your Dodge Journey. The code is usually triggered by an oxygen sensor upstream (behind 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.

  • 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 Dodge Journey Code P0420.

Related: Dodge Journey P0442


The Top Reasons for P0420 In the Dodge Journey

P0420 can be caused by many factors. Below are some common causes.

  • 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 Journey’s exhaust. These can become blocked over time. Even though modern catalytic convertors are designed to last the lifespan of vehicles, they can become clogged.
  • The O2 Sensor Wiring– Over time, the oxygen sensor wiring can go bad. Because it's right beside the exhaust, this wiring is 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).
  • Journey timing– If your Journey 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. The O2 sensor could be thrown if the mixture of fuel and oil is too rich.


Possible Solutions to the Dodge Journey P0420 code

P0420 can often 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. Checking the exhaust for signs of leakage is a smart idea. 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. Below are some good guidelines to assist you in this task.

You will be able to identify the cause of P0420 in your Dodge Journey. Please let us know if you find any errors or suggestions to improve this article. Many thanks.

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