hi guys,

mods on the car:
Espelir downpipe
Helix hi-flow cat
Espelir catback
K&N drop in filter

about a month ago i started getting a P0420 code.
"Catalyst System Efficiency Below Threshold (Bank 1)"

i've reset the ECU twice now, the code goes away for a bout a week, then comes back.
i got it again yesterday.

it seems to me like this started happening with warmer weather in Cali.
what could be the problem?
i've had full exaust with hi-flow cat for about 5 months before this started happening without any issues.

 

I would bet its your high flow cat for some odd reason.

 

why did it take so long to throw a code?

 

For some reason the high flow cat you have is all the sudden is too high flow. Get a test pipe and a O2 sim and put the stock cat on at emissions time.

 

ehh, dont want to go through the hastle of driving arround with a test pipe.
i'm always scared of stopping at a red light with a cop next to me or behind me.
if i can smell it, i'm sure they can too.

 

I love that smell... dunno why. lol.

 

0420 code = "lack of use of search feature"

 

Try the single sparl plug antifouler trick listed in the how to section and keep your high flow cat. You may still have to swap in your stock cat at emissions time if your high flow is not doing the trick.

 

To be fair to the OP Al, he does have a high flow and not a TP. Plus this started happening after it worked for 5 months

 

Yea do this if your worried about a cop looking under your car or somthing

 

a statement: "0420 code = lack of use of search feature" ="inability to understand my first post"

 

Well if its any consolation, I got the same code despite me still being on the stock exhaust a few months ago. Every week or so, I kept getting the P0420 until I eventually changed out my stock cat for a 2.5" Ultimate Racing test pipe. I haven't gotten a CEL since, and no, I am not taking it in for warranty either lol. Only had about 4500 miles before it started giving me issues and I only had a flash at the time.

 

you did'nt by any chance bottom out your car recently, did you? If you crushed up the cat a little, it'll do that too.

 

Did someone say 4:20?? J/p man.

 

The 04 Subies are notorious for throwing those. You could read about it on their forums - just an idea.