sjrougeau

I have a 2001 996 Carrera Cabriolet with 61K on it. I just started getting the fault code of P0430 "Catalyst System Efficiency Below Threshold Bank 2" When I bought the car last year all four 02 sensors were replaced so I'm bit skeptical whether this could be the problem but then again anything is possible. What is the probability that any of the o2 sensors would go bad after 16 months? I've heard that normally catalytic converters do not go bad but then again some have. I've reset the check engine light several times and the light comes back on intimately after 20 to 50 miles of driving. Does P0430 specifically indicatate that my Cat is bad or are there other things I need to look at before spending the time and money to replace the cat or the 02 sensors?

JimmyB

Try a couple of bottles of Techron and some expensive gas - did the trick on mine for a while until I got around to having the exhaust system replaced

dwhitlow

Catalytic converters definitely can go bad on these cars. The OEM ones cost an arm and a leg. Two years ago, I replaced my failing OEM cats (was getting P0420 and P0430, both banks) that had ~90K miles on them with a pair of OEM takeoffs from a parts car that had <70K miles on it. I did not replace the O2 sensors, and it cleared up my codes. I now have 112K on the car, and still haven't gotten those codes again. I figure I bought myself some time to coordinate a refresh of my now 'extra' cats with someone like Gert at Carnewal. (though I've dragged my feet on actually send the extra ones out to him for refresh)

Jaycote

I'm in the same boat. My mechanic says it's not a big deal, but it still bothers me when that check engine light pops up. I can't ignore it because I want to make sure the light isn't coming on for something else, unrelated. I passed emissions inspection right before it started, so I have a couple years before I have to find a fix for it. I did get an 02 Sensor code one time, but it has not come on again, so i'm unsure if this is related to my O2 sensor, or if it truly is the Cats. Prior to this issue, I had a coolant leak into Cylinder 1, and swapped engines. I'm thinking that Coolant got into the Cats and is what is causing the issue to pop up immediately after the engine was swapped.

Gert

The early 996 sometimes have cat elements that break loose .
This triggers fault code 420 or 430 .

Knock on the housing (like you would bang on a door) .
If the element is loose, you should hear the element moving inside.

This is what's left over of the elements, after some time :