Okay, new problem! P0430 then P04020 CELs

[black_box]

Hey guys!

Just so you don't get bored, I have a new issue!

After I fixed the problem from before my clutch/IMS job (loose #6 plug), I took the car for a 250 mile joyride in upstate NY, and it threw a P0430 (bank 2 cat below threshold). I cleared that and then a few days later it throws P0420 (bank 1 cat). So....

air leak?
both cats going bad (unlikely)?
any ideas before I start ripping into it?

Thanks!

[sb01box]

my 01 boxster has similar is problem. whenever I set the cruise control on about 65mph and if the road is flat for about 5 minutes, CEL P0430 comes on. Never the other side.
car has 123K miles and did run into AOS failure 30K miles back (instant crop duster). maybe the O2 sensor was damaged.
I'm just resetting it and "thinking" about it.
no help but welcome to the party!!

[Jager]

What does the seal on your gas cap look like?

[black_box]

I'll check both possibilities tomorrow

[paulv]

Since you were working in that area, check the wiring/connectors to both downstream O2 sensors. Since these sonsors are in an area where things get hot, the wiring could be brittle and cracked. The diags info for these codes essentially says the cat is bad. Before doing any cat work, I'd have someone with a gas analyzer check the levels of emissions coming out of the exhaust to see if they're out of spec.

Regards,
paul...