Possible causes

– Catalytic converter deterioration or malfunction
– Exhaust system leaks
– Loose front or rear HO2Ss
– Faulty front heater O2 sensor
– O2 sensors harness is open or shorted
– O2 sensors poor electrical connection

Tech notes

As the code description implies the P0431 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 P0431 code is combined with other codes, try fixing the other codes first.

When is the code detected?

If the frequency ratio of front and rear HO2S is higher than threshold value, the PCM determines that a fault exists and the P0431 code is stored.

Symptoms

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

P0431 2003 KIA SEDONA Description

The catalyst’s efficiency is demonstrated by its ability to oxidize CO and hydrocarbon emissions. The Powertrain Control Module (PCM) compares the output signals of the front and rear oxygen sensors to determine whether the output of the rear sensor is beginning to match the output of the front oxygen sensor. Air/fuel mixture compensation keeps the frequency of the front oxygen sensor high due to the changes from rich-to-lean comvustio. The catalyst causes the rear oxygen sensor to have a lower frequency. As the catalyst wears, the rear oxygen sensor’s signal trace begins to match the front oxygen sensor’s signal trace. That is because the catalyst becomes saturated with oxygen and cannot use the oxygen to convert hydrocarbon and CO into H?O and CO? with the same efficiency as when it was new. A completely worn catalyst shows a 100% match between the frequency of the front and rear sensors.

2003 Kia Sedona Catalytic Converter Location

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