p0420 w/ 2 year old magnaflow cat

Yes to all of the above. I have made a number of posts on P0420- use the search feature. A common source for exhaust leaks is the gasket at the spring loaded flex joint at the exhaust manifold. I find that an OE gasket from Toyota works the best- for any brand cat.

 

If you don’t have leaks, the o2 sensor is ok, and the cat is just worn. I have these on my Prius’. Our check engine lights never returned.

 

P420 is a common emissions code it could be alot of things even a leaky gas cap. Does not always point to the cat. But if it is the cat that tells me your engine probably burns oil and it fouled your new cat.

 

Well, the code definitely means that the car's self-test for the oxygen-storage capacity of the cat was carried out, and completed with a not-passing result.

So the only time it doesn't point to the cat would be when some other problem is causing the cat OSC test to falsely indicate failure.

That's kind of the coin-lands-on-edge case, but leaks in the exhaust system, or problems with the A/F or O₂ sensor, can do that sometimes.

 

Subbed


iPhone ?

 

I have one sitting here ready to go Angle just like this I guess I better get it on and clear and see how well it does I know it did not work for my Corolla but that's an AC Delco computer car that ACDelco made grave firmware mistakes on programming it.