OBD-II Trouble Codes

P0431 Code: Warm Up Catalytic Converter, Bank 2—Efficiency Below Threshold

Reading Time: 3 minutes

Engine codes are crucial in identifying mechanical and electrical issues in cars. They come in a unique combination of letters and numbers that distinguishes whether the fault affects the body, chassis, powertrain, or network communication. Without these codes, it will be hard to trace what is causing the problem.

The P0431 code, for instance, indicates the powertrain control module (PCM) has perceived the warm up catalytic converter (on bank 2) is not operating properly. If your vehicle logs this code, it is important that you familiarize yourself with what it entails before troubleshooting. What does the engine code P0431 code mean, what are its possible causes, and how is it fixed? Read on to learn the answers to these questions and mode.

What Does the P0431 Code Mean?

Diagnostic trouble code (DTC) P0431 stands for “Warm Up Catalytic Converter, Bank 2—Efficiency Below Threshold.” It means that your car’s primary computer or powertrain control module has detected that the catalytic converter is not efficient enough based on factory specification.

Catalytic converter efficiency is monitored using upstream and downstream oxygen sensors. Most of these sensors contain zirconium dioxide-sensing elements enclosed by vented steel housings. These are connected to the lead wires in the oxygen sensor wiring harnesses via platinum electrodes.

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The PCM will store code P0431 if it reads that the upstream and downstream oxygen sensors of the catalytic converter on Bank 2 are reflecting similar exhaust oxygen concentration.

The PCM uses the data from the oxygen sensors, which come in the form of voltage signals, to compute ignition timing and fuel delivery strategy. If the signal output from the oxygen sensor is lower, it means more oxygen is present in the exhaust (lean condition). If the signal output is higher, it means less oxygen is present in the exhaust (rich condition).

The PCM will store code P0431 if it reads that the upstream and downstream oxygen sensors of the catalytic converter on Bank 2 are reflecting similar exhaust oxygen concentration. It will also activate the malfunction indicator lamp.

Note: The definition of code P0431 may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

Users have reported p0431 for the following makes: Mitsubishi (especially on a Mitsubishi Eclipse), Kia, Audi, Porsche, and Mazda.

What are the Possible Causes of the P0431 Code?

Here are the common causes of the P0431 code:

  • Bad catalytic converter
  • Faulty oxygen sensor that’s not working properly
  • Presence of an exhaust leak

What are the Common Symptoms of the P0431 Code?

Depending on the severity of the catalytic converter problem, other related DTCs may also be stored. Their symptoms may vary or overlap. Regardless of whether you’re dealing with multiple DTCs or just the P0431 code, you can expect an illuminated check engine light. Here are other symptoms you may experience with the code P0431:

  • Diminished fuel efficiency
  • Decreased engine performance
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An illuminated check engine light is a common symptom of error code P0431.

How to Diagnose the P0431 Code

Diagnosing code P0431 can get a little tricky as the process may vary depending on the year, make, and model of your car. For example, diagnosing a P0431 in a Mitsubishi may involve steps that are different from what the owners of other makes and models follow. The viable solution would be to seek a certified mechanic’s help to save yourself from costly mistakes.

How to Fix the P0431 Code

There’s no universal fix to clear the P0431 code as the solution varies based on the causes and the vehicle’s make and model. If you’re not confident with your DIY skills and knowledge about the code, it is best to let the professionals handle the job.

If you have decent DIY skills to work on your car, you may use online auto repair resources and guides to figure out the proper way of fixing DTC P0431. One of the best examples you could use is ALLDATA. This subscription will give you access to thousands of information that you can use for your convenience. Also, keep in mind to cross-check with the repair manual before starting the repair process.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic.

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