Contour Enthusiasts Group Archives Forums General Troubleshooting exhaust question

A few weeks ago I posted that my cel came on and gave me a P0420 code. Got some feedback but a new question has come up. Awhile back (four years ago) I had a custom exhaust put on from the cat back. Where the pipe is suppose to split into a y, the guy t"d it off. It went from a 2.5 inch pipe to 3 inch t then back to the 2.5 inch pipe to the mufflers. One, would this hamper the performance of the car. And two would this clog the cat. quicker causing the code to come on? Thanks.

well 3 " pipe o a 2.5 NA is way too big. Sounds like a hack job. Doubt it caused the cat to clog.

The cat monitors (2nd set of oxygen sensors that trigger that code) are after the pre cats and before the main cat, so, no, your cat back would not have effected the pre cats to help set that code.

You may not actually have a problem. That code is often set without there really being much wrong. There is a recent TSB that reprograms the PCM to widen the parameters for setting that code (although it doesn't apply to all cars, mine is excluded). Make sure the engine is running well, clear the code, drive it for a few weeks and see if the code returns.