Codes P0421 and P0431

2009 PORSCHE CAYENNE
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PENGRR5200
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this car use only 60,000km.and the engine check light all get on. the fault codes are P0421 and P0431. we suggested the customer use some Fuel Additives, but some days later this happen again. we change the fuel filter , and clean the gas line and inject valve ,change the plug. Last time we disassembly the catalyst ,check it did not block. The car came back again. the engine light get on again. and the Phenomenon happen to many cayenne .so i really hope to know how to do ??
Jul 31, 2010 at 9:43 AM
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DANNY L
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Hello, I'm Danny.

Those 2 codes are for bank 1 and bank 2 primary catalytic converter deficiency. Here are a few catalytic converter tutorials showing description, testing, and replacement:

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

https://www.2carpros.com/articles/catalytic-converter-replacement

I've attached below picture steps of the testing procedures for your vehicle. Hope this helps and thanks for using 2CarPros.
Dec 7, 2020 at 5:38 PM