Where's that bad cat?
 

P0430. Bad cat bank 2. If it is indeed a failing catalytic converter ( and I am not sure of this as we all know that sometimes these pesky codes are cryptic and mean that it's really somebody else's fault), which cat is to blame? Logically it would be the pre-cat as the O2 sensors are found fore and aft of that one in the model that I have. If the main cat is monitored, I don't see how.
Having found a nasty fouled and corroded O2 sensor on the aft side of the suspect pre-cat (since been changed), i fear that an oil overfill might have caused some damage.
So essentially, I would like to find a method to test the cat(s) to see where I should throw my money next!
Cheers!

The post cat o2 sensors test the cats every time you drive. If the code doesn't come back you are all good :)

Whew :eek:, I thought this was going to be another cat thread!

Well, at least it's not about IMS or tires! ;)

I cleared the codes on a friends car 911, 996. He had got never seize on the O2 sensor while installing post cat position this caused a heat cycle and heater fault. I forget his actual codes but if you foul the sensors they may fault and then later clear and stay clear.

To check the cats, you need to plot the O2 sensor voltages. The pre cat voltage should look like a sine wave, the post cat voltage should be close to a straight line. If the post cat voltage starts to look like sine wave, then you have a bad cat.

"Bad kitty!" - Cartman

Both pre and post are in roller-coaster mode which, of course, indicates a failing cat. I changed the contaminated/corroded O2 sensor and went on a trip of about 800 miles or so over 3 days. No CEL for that period. I get back and putter around town a bit and bingo! A CEL pops up.
Looking for a used bank 2 pre-cat.