Trouble codes P0431 and P0421 on your Mitsubishi indicate a problem with the
Catalytic Converter (in the worst case) and simply several cold starts (in
the best case). Basically this means that the oxygen sensor downstream of
the catalytic converter detected that the CAT is not working as efficiently
as it should be. Most likely you will not notice any drivability problems.
After a week or two if the codes do not automatically clear you will want to have a smog check repair station conduct a hands on diagnosis.
posted by SmogTips Support
