I keep getting a P0420 - Powertrain Catalyst system efficiency below threshold (bank 1)
I'm pretty sure I have a leak at my flange gasket (manifold to intermediate pipe)
Would this cause this code?

 

Not smoking enough doobies ... is it still the original cat?

 

I believe it is

 

From the above, I could say the reason for a blown gasket I guess... A clogged cat?

..more seriously, the CAT code is thrown on comparison O2 sensors before/after cat. Not much place for an error... I mean You could try fixing the gasket and clearing the code, but more likely the cat is over.

 

Was hoping to avoid the $250 cat.
Well, I'll change the donuts, re-set the code and see if it pops again.

Thanks guys

 

You can try gambling with the cheap ones, I lucked out with mine. But christine had a nightmare with hers.

 

Well not cheap, I get them at cost

 

Yeah, on ours the upstream sensor is on the manifold and the downstream is behind the second cat, so it could be the leaky donut gasket.
I replaced the donut and re-set the code, I'll see if it pops the code again, if so then I'll replace the cat

 

So I swapped out the donuts and the code popped again.
Ran the smog check and it says that the catalytic converter passed but the evap didn't.
I'm posting pics of the results, any ideas would be nice, I will replace the cat system, both front and rear if I have to, but I would like to know if I can avoid it.

 

any ideas?