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

This page was created to assist you in troubleshooting the problem. Dodge Caravan P0420 trouble code. The article discusses Dodge Caravan P0420 causes, meanings, and possible solutions. OBDII P0420 in Dodge Caravan is usually caused by an oxygen sensor problem, although there are other possible causes. You may lose time and expense by not replacing your O2 sensor immediately.

The most common trouble code is P0420. This is the code that you get when you connect your Dodge Caravan to an OBDII scanner. It doesn’t matter which model you have, this OBDII code has the same meaning for all of them (1996+)

Dodge Caravan P0420 OBDII Code Defined

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

Low Catalyst System Efficiency

At least two oxygen sensors are installed in your Caravan, 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).

These readings shouldn’t match, since the catalytic converter is supposed to be scrubbing the exhaust. The software on your Caravan detects that the catalytic conversion isn't doing its job when the numbers match.

Dodge Caravan P0420 Code Symptoms

A Dodge Caravan's P0420 code will usually be caused by an oxygen sensor not working properly. The upstream oxygen sensor will usually trigger the code (before it is sent to 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- You may or not experience any problems depending on the extent of catalytic conversion blockage.
• 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 Caravan P0420 code.

Related: Dodge Caravan, P0442

Here are the Top 10 Reasons Why Dodge Caravans Have P0420

You can have the Caravan P0420 trouble code for many reasons. These are some of the more common.

• 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 Caravan’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 problem.
• Connecting O2 Sensors– 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).
• Caravan Timing– If your Caravan 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.

Dodge Caravan P0420 Code Possible Solutions

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. 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 two excellent guides for that purpose.

It's your task to find the root cause of P0420 on your Dodge Caravan. You can comment on the article or send a message if there are inaccuracies or any suggestions. Many thanks.