What does this code mean?

Code P0430 came up in my 96 wagon. Where do I go from here?

P0420 - Catalyst System Efficiency Below Threshold (Bank 2)
Indicates Bank 2 catalyst system efficiency is below the acceptable threshold.
Possible Causes
· Malfunctioning ECT/CHT
· High fuel pressure
· Damaged exhaust manifold
· Cylinder misfiring
· HO2S wiring concerns (shorted or chafed, bent pins, etc.)
· Damaged exhaust system pipe
· Damaged muffler/tailpipe assembly
· Retarded spark timing
Damaged Catalytic Converter:
· Use of leaded fuel
· Oil contamination/consumption
· Silicone contamination (sealants/cleaners)

Check engine light went off by itself? What gives?

I've not had this code on my vehicle but my daughter's car (95 Mitsu Eclipse) had a similar code for the same thing. It occured shortly after I had taken it for a test drive (play time), wound it up bigtime and banged thru all 5 gears. (many times) The next day or so we got the code. It too went away by itself. My guess is that I loosened up crud and rust in the exhaust system and it temporarily plugged up the cat converter partially. Either the crap blew out or settled into a "nicer" place. No light since. Just passed NJ inspection. Keep an eye out for the light and the same code. How rusty is your exhaust system?

It too just got thru NJ inspection. I had the oxygen sensor replaced last summer (the one before the cat-conv), and the light went off. It stayed off till last week, and like I said, it popped off again by itself.

I wonder if one of the other oxygen sensors can be acting up?

The code you mentioned is not "for" O2 sensors per se, but points to an exhaust system related component. There is (I think) an O2 sensor close to the cat, probably after, to measure the exhaust gases. If it is bad it could give that code.

After being off for a week, the light just came back on.

If itwas my car I'd replace the o2 sensor back by the converter. It only reports what's happening, it doesn't affect the fuel mixture like the front ones do. If that still doesn't fix it then I'd start thinking that there is a problem with the cat or restrictions in the exhaust system.

Code P0430 came up in my 96 wagon. Where do I go from here?

I've been getting this code off and on for about a year now on my '97 wagon. I'm guessing it's an O2 sensor, but the car has 4 of them (one before and after each converter), and I have no way of testing which one is the bad one. I've thought about maybe buying ONE sensor and then rotating it thru each of the four slots until the problem goes away but I don't know (yet) if the sensors are all identical, and I might end up destroying ALL the sensors in the process (they're all original and the car has 125k on it). Another thing I've heard it could be is a leaking vacuum hose, but I'm not sure how to find this because I don't know how many of these hoses exist, where they're located, and how to tell if they're cracked. I don't HEAR any hissing under the hood, but maybe you can't tell until you actually bend the hose...