Hi, I have a 2001 neon with a big fat catalytic in the manifold, California ULEV, I think, followed by a small cat in the pipe and am getting a p420 code which is bad cat. The O2 sensors are before and after the manifold cat.I am in western NY were OBD2 is in use for inspection and am looking for a quick fix. The car runs great as is with 110,000 miles and am thinking about using the plug fowlers to extend the rear O2 sensor out of the exhaust to get a low reading. Will this work? Other choice is to change the manifold and exhaust with a east coast system, i.e. cat in the exhaust pipe. Will that work with the PCM?
Thx for any help
Al

 

If you have a bad cat, moving the O2 sensor up may get rid of a CEL for a bad/faulty reading on a downstream O2 sensor (that's the whole purpose of that little "mod"), but I don't see it passing the actual test.

 

You might get worse readings, the farther away the O2s are from the cat the colder they get and the longer it takes for them to warm up. That's why they position the cat as close to the engine as possible in places like Cali.