AutoCodes.com | All About OBDII Engine Codes
AutoCodes - Mitsubishi - P0420 Mitsubishi

P0420 Mitsubishi Code - Catalyst System Efficiency Below Threshold Bank 1

- Code Popularity: 78,018 Views
- Repair Importance Level: 2/3
- Repair Difficulty Level: 2/3
Table of contents
Share on Facebook   Share on Twitter   Share on Linkedin

What are the Possible Causes of the DTC P0420 Mitsubishi?

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
  • Faulty Three-way Catalyst Converter Bank 1
  • Exhaust Tube
  • Intake Air Leaks
  • Faulty Oxygen (O2) Sensor
  • Faulty Fuel injector(s)
  • Leaking Fuel Injector (s)
  • Faulty Spark plugs
  • Improper Ignition Timing
  • Faulty Engine Control Module (ECM)
  • Dirty Air Filter
⚠ Does your Mitsubishi have Safety Recalls? → Check here

How to Fix the DTC P0420 Mitsubishi?

Review the 'Possible Causes' mentioned above and visually examine the corresponding wiring harness and connectors. Ensure to check for any damaged components and inspect the connector pins for signs of being broken, bent, pushed out, or corroded.

Code Tech Notes

As the code description implies the P0420 code means that the vehicle's control module has detected that the three-way catalytic converter is not working properly (is not as efficient as the factory is expecting). Replacing the oxygen (O2) sensors may sometimes fix the code, but in most cases the catalytic convert needs to be replaced to fix the problem. If the P0420 code is combined with other codes, try fixing the other codes first.

Search for P0420 Mitsubishi Questions and Answers: Search here →

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0420 Mitsubishi code, it typically requires 1.0 hour of labor. The specific diagnosis time and labor rates at auto repair shops can differ based on factors such as the location, make and model of the vehicle, and even the engine type. It is common for most auto repair shops to charge between $75 and $150 per hour.

When is the Code Detected?

- Three way catalytic converter Bank 1 does not operate properly.
- Three way catalyst converter Bank 1 does not have enough oxygen storage capacity.

What are Code Possible Symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)

Code P0420 Mitsubishi Description

The Engine Control Module (ECM) monitors the switching frequency ratio of heated oxygen sensors 1 (front O2 sensor) and heated oxygen sensors 2 (rear O2 sensor).
A three way catalyst converter (Manifold) with high oxygen storage capacity will indicate a low switching frequency of heated oxygen sensor 2. As oxygen storage capacity decreases, the heated oxygen sensor 2 switching frequency will increase.
When the frequency ratio of heated oxygen sensors 1 and 2 approaches a specified limit value, the three way catalyst malfunction is diagnosed.

OBDII Code P0420 Mitsubishi - Catalyst System Efficiency Below Threshold Bank 1 - AutoCodes.com
P0420 Mitsubishi Code - Catalyst System Efficiency Below Threshold Bank 1

Need More Information on the Code?

Need more information on how to fix the P0420 Mitsubishi code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0420 Mitsubishi code diagnosed by a professional: Find a repair shop in your area

Code P0420 Mitsubishi comments

Help us improve AutoCodes.com. Leave a comment below or tell us if the information above helps you fix the code. What are the symptoms on your vehicle for the P0420 Mitsubishi code? Have you replaced any parts?
Any information is appreciated. Thanks