Earlier today I got a p0420. I browsed many threads and it seems to be mostly an O2 sensor, or pre-cat issue. I don't have pre-cats, and I just replaced my o2's about two months ago for inspection.
Although the post cat sensor is ghetto rigged because the socket that was on it, didn't match up to the OEM one (thanks ebay ). So I cut it off, wired it up to the OEM wiring. Has worked
fine since.. no codes at all! How do I really tackle such issue? Check spark plugs and wires?

Side note: I do have a universal Magnaflow Cat Conv. welded on. I don't see how it could be clogged. I only got it within a year ago.

 

Cheap universal cats tend to burn out in short order. On my phone now so don't know what P0420 is but it sounds like your system is jacked.

 

http://www.obd-codes.com/p0420

 

So you would say $80 is cheap for a converter? I mean it's from a well known manufacturer.

 

you got what you paid for, nuff said.

 

Checked Cylinder 1 spark plug, seemed fine. Did a tap test on the converter, and no rattle. Erased the code. Let's play the waiting game.

 

I just had the same problem my cat was clogged and the main cat was hollow swapped everything over from a used 02 max into my 02 i35 so far so good

 

Below catylist thershold catyalic converter o2 sensor code downstream towards the cataylic converter. I would check for leaks of the cataylic converter and the o2 sensor.

 

Maybe I should def check leaks when it's running. The code hasn't come back yet, maybe something minor triggered it. Only thing that may be worth keeping mind of, is when I did the tap trick on the converter a small amount of smoke came out. The kind of smoke when it's blazing hot, not like a thick cloud. Probably nothing.. Might've been from the heat trapped within the shield around it.

 

Is this the old 0707 code? From the ECU screw method?

 

I don't believe so. I don't use the screw method. I have a OBD2 scanner.