Q: My car has two error codes

Getting a hold of the OBD codes is definitely a great first step to diagnosing your Mitsubishi, but it must be noted that OBD codes are only a starting point, not a diagnosis. The codes P0401 and P0431 are actually two separate concerns going on with your Galant.

First, we will start with the code P0401, which represents insufficient EGR flow. There are a few different reasons that can cause this code to pop up. This includes lack of vacuum to activate the EGR valve, the EGR valve itself has failed, or there is a blockage in the EGR system preventing flow.

Now in regards to your second code, P0431, this represents a Warm Up Catalyst Efficiency Below Threshold signal. With this code, it is possible that the catalytic converter is no longer functioning efficiently and you may have an exhaust leak. There is also the chance that the oxygen sensor that monitors the catalytic converter is failing.

As you can see, there is a long list of possibilities that could be causing your Galant to give these codes. To be 100% certain, it may be time to enlist the assistance of a certified mechanic. They will be able to comprehensively inspect your vehicle and determine exactly why these codes are in your computer as well as assist you in making the necessary repairs to keep your vehicle running at its best.