Weld-On Catalytic Converter

I'm guessing I need a 2"? I have a P0420 with a new o2 sensor.



which cat should I purchase? I have read the magnaflows cause a p0420

Reply 1 : Weld-On Catalytic Converter

I wouldn't blame the cat right away - which O2 sensor did you replace? Did you use a Denso sensor?

Need more info - mileage, model year? Any oil consumption issues?



If it is indeed a bad catalytic converter. Then it becomes and issue of how long you want it to last. Aftermarket ones are considerably less expensive than OEM, but also have a considerably shorter lifespan - some cases less than a year or two for some drivers.



Size of the piping is not too important if you cutting the old one out anyways, the shop can weld in pipe reducers to get it to the diameter they need. As for Magnaflow causing CELs? I'd say that is more a question of who installed it and if there were any other issues with the car. Magnaflow itself makes very good aftermarket parts, so they would not cause a P0420, unless it was installed incorrectly or the wrong part used.

Reply 2 : Weld-On Catalytic Converter

Check for exhaust leak. I've got one right where the O2 sensor bolts on to the flange to the left (sitting in driver seat) of the exhaust manifold. I'm just lazy and haven't bothered to fix it yet. It's a small leak.