P0430 - Which Cat? 2003 S
 

P0430, associated with the bank 2 catalytic converter - the "three way" or "main" cat

Which one is that? The one that's part of the manifold assembly? Or the one after that? Which is the correct part to change associated with a P0430 on a 2003 S?

the one circled in red (99611310407)

or the one circled in blue (996-113-023-BX)

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Before anyone suggests local shops, I only really trust the main Porsche dealer here now. The local indys here in St Louis want to raid my wallet to diagnose the 02 sensors (which I can swap myself to test) but tbh I'm not impressed with any of the 3 indys I have to choose from, and shocked by the simple things they've missed. Like overfilling at every oil change, completely missing my failing 2nd gear synchro at PPI and a visit to a different indy, and somehow missing my totally toasted engine mount even though I specifically asked for it to be checked. So now I do the work myself if Porsche is backed up. That and the highway robbery: $450 for an alignment at one shop (Porsche STL charges $250, a local track prep shop $220...), trying to charge me $1100 at another well-known shop for an oil change and coolant flush ($550 at the dealership...)

I'd bring it into Porsche but my Cayenne is going in next week for a DEF tank heater, and since my QuickJack just arrived and I'll have a Macan loaner I was going to tackle this problem on the 986 myself.

And yes, I do need a Durametric now.

Awesome.

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What kind of diagnostic tools do you have? Any that will display the wave form of the O2 sensors signals?

https://986forum.com/forums/boxster-general-discussions/77357-p0430-what-do-post626811.html#post626811 had the same problem and there is a discussion there on what he was checking including the wave forms he was seeing.