Ford Econoline P0420: Catalyst System Efficiency → Below Threshold → Bank 1


Ford Econoline P0420 Diagnosis


This page was created to assist you in troubleshooting the problem. Ford Econoline P0420 trouble code. The definition of P0420 includes symptoms, causes and potential solutions. OBDII is commonly caused by OBDII, P0420. 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. Ford Econoline OBDII code P0420
  2. Ford Econoline Code P0420 Symptoms
  3. Top Causes and Solutions of P0420 on the Ford Econoline
    1. Oxygen Sensor
    2. Catalytic Converter
    3. The O2 Sensor Wiring
    4. Timing
    5. Check for Leakage
    6. Motor Temp Sensor
  4. Conclusion

Ford Econoline OBDII code P0420

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

The Catalyst Systems Efficiency is Below the Threshold

There are at least two oxygen sensors in an Econoline. One is before and one after the catalytic convertor. One of their many duties is to determine the level of emissions coming into and out the converter.

The vehicle will light the service engine when the oxygen sensor readings show identical readings (P0420).

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


Ford Econoline Code P0420 Symptoms

P0420 Ford Econoline

If your oxygen sensor is not working properly, the P0420 code will be displayed in a Ford Econoline. 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- You may or not experience any problems depending on the extent of catalytic conversion blockage.
  • 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 Ford Econoline code P0420.

Related: P0442 Ford Econoline


Top Causes and Solutions of P0420 on the Ford Econoline

Many things can lead to the P0420 code on your Econoline. Below are some common causes.

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. 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.


Oxygen Sensor

If the two exhaust oxygen sensors have identical readings, P0420 is thrown. When the oxygen sensor is bad, it can cause a false reading and trigger the code.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 (or you haven’t noticed the performance loss yet).

How to test an O2 sensor or oxygen sensor (YouTube)

New Oxygen Sensor – Ford Econoline (Amazon)


Catalytic Converter

A catalytic converter is responsible for scrubbing out as much pollution as possible from the Econoline’s exhaust. These can become blocked over time. Modern catalytic converters should last for the lifetime of most cars, but if they become clogged, 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. The oxygen sensor wiring is particularly volatile because it sits next to hot exhaust. It is volatile because it is further from the ECM.

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



Your Econoline may be misfiring, or your exhaust timing is incorrect. This can cause gasses to go to O2 sensors and the registration code P0420 to occur.

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.

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 not see the exhaust that the O2 sensors can detect and could throw the sensor.



You will be able to identify the cause of P0420 in your Ford Econoline. You can comment on the article or send a message to suggest improvements. Many thanks.

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