Replaced cats, still throwing po430, what next?
Thread Starter
On The Tree
Joined: Apr 2007
Posts: 124
Likes: 0
From: Connecticut
Replaced cats, still throwing po430, what next? I have the MAC mid lengths with full exhaust. The first time I got the po430 code I replaced the o2 sensors, no luck so I replaced the catted y pipe and it's still throwing the code. I tried the search, but I didn't find any new ideas except for replacing the plugs. The last time I changed the plugs and wires was about 8,000 miles ago. Should I replace them again? What else should I check? By the way, right before the service engine soon light comes on, I can feel a vibration coming from the exhaust. It happens every time, when the exhaust vibrates in a certain way the light comes on. It's usually after driving about 45 highway miles and I stop at the traffic light at the end of the highway. Other than that it runs strong, no power loss, idles fine. There are no leaks between the headers and the cats.
Last edited by Cruz28; Jul 19, 2007 at 08:59 PM.
TECH Enthusiast
Joined: Jul 2006
Posts: 638
Likes: 0
From: San Diego
The p0420, and p0430 codes are very simple... Your cat(s) is bad, period. I doesn't matter if you just replaced them, most aftermarket cats I have come across are not truley OBD2 compliant. The code cannot set if you O2 sensors are the problem, in fact you know that all of your O2 sensors are working perfectly, because the code set. The ecm looks at the pre and post cat O2 activity, if the pre cat O2 switches rapidly, and the post cat O2 switches very slowly, then your cats are working, no problems. The issue is when the post cat O2 starts switching at the same rate as the pre cat sensor, then the ecm knows that the cat is not doing it's jod, and it throws either a p0420, or p0430 code, depending on which bank is acting up.
