DTC Description
WARNING: This page is about a different car, the 2021 Kia Soul. However, it is still accessible from the selected car via links, so may be relevant.
If the PCM detects that engine speed variation indicates a misfire sufficient to cause three-way catalyst converter damage or emissions level to exceed standard value, the PCM sets DTC P030400. If the misfire rate is high enough to damage the catalyst, the MIL will flash to alert the vehicle operator.