2006 3.2L V6 Cayenne Tiptronic S

[Essdee56]

Hi all, my vehicle has just been diagnosed with Fault Code PO421 (Bank 1 catalyst warm up efficiency below threshold). The lambdas and MAF have been checked and are operating within their parameters so have now been informed that I require a new catalytic convertor on "Bank 1" on which there are actually 2 cats in this unit. This vehicle has just completed 77,000 trouble free miles and only high grade fuel, lubricants and parts have been used at all time notwithstanding that, until I purchased the vehicle a little over 12 months ago, the vehicle had been maintained meticulously by Porsche themselves. The cost of the replacement cat with labour and the dreaded VAT is over £1500 however I have the option to purchase the cat seperately and just pay for the labour. Any pointers and/or suggestions would be very welcome. Thanks in anticipation of some responses.

 

[Geoff_Fields]

Sometimes Lamdas can test OK when warm but play-up when cold hence can trigger that warning. Might be worth swapping them around to see if reported fault moves. I believe there is a CAT decarboniser, which can be added to fuel for a couple of fill ups that can sometime resolve this also.

 

[Essdee56]

Thanks Geoff, certainly worth a try and substantially cheaper if it works, thanks.