P0420 Catalyst System Efficiency Below Threshold (Bank 1)?!

IH8PVMNT · 02-05-2008, 10:48 PM

so i was cruiseing home yesterday after work at say 40mph local road 2k rpm not beating on it and my check engine poped on i didnt feel any driveablity difrence so i turned back around and went to get my scann tool from work, pulled a p420 for the cats... now i know usually when i get htis code at work on a customer car the cats are known to go bad... o nthe jeeps at least.... but my car is so far completey stock as far as exhuast. all i currently have it a spt intake.... and ironicly have the coob ap and invidia 3 inch catless dp on the way.... any one goten this code before on an all stocker... some thing common??

dumdum · 02-06-2008, 06:03 AM

Has to do with the rear O2 sensor.Maybe the sensor is bad,shorted wire, or unplugged.You car should still be under warrenty right?For the 32 bit ECU cars (All STi's and 06+ WRX) this sensor is kinda important.I would get it fixed soon as ya can.

octoparrot · 02-27-2008, 09:24 PM

Quote:

Originally Posted by dumdum

Has to do with the rear O2 sensor.Maybe the sensor is bad,shorted wire, or unplugged.You car should still be under warrenty right?For the 32 bit ECU cars (All STi's and 06+ WRX) this sensor is kinda important.I would get it fixed soon as ya can.

Isn't this the code for an aftermarket exh (prob catless)? My buds got an 07 and i put a mecanical fix and it was great as soon as we put it on. i got an extra one, brand new for sale... email me if you want it agalambos@caton.com

Longshot · 02-28-2008, 06:48 AM

Quote:

Originally Posted by octoparrot

Isn't this the code for an aftermarket exh (prob catless)? My buds got an 07 and i put a mecanical fix and it was great as soon as we put it on. i got an extra one, brand new for sale... email me if you want it agalambos@caton.com

The code is for the rear sensor like dumdum said. If you were to switch to an aftermarket DP it may trigger this because of the increased airflow. In this case though, since it's only the stock DP, he's probably correct in saying it's the sensor itself, or the wiring. The OP doesn't need a mechanical fix.

IH8PVMNT · 02-28-2008, 09:24 AM

i figured it out its nothing to do with the sensors i probed them all checked out ok and what not,.... i jusr recently added that redline fuel system cleaner to my tank... and i think it dumped all of the crap into the cat and destroyed it i clear the code and it comes back every other tank of gas.... ive seen this happen b4 on the jeeps at my dealer... its ok catless dp this weekndf!!!!!!!!!1

octoparrot · 02-28-2008, 12:12 PM

My mistake, didnt see that it was stock dp.

413TreX · 12-17-2008, 07:18 PM

Quote:

Originally Posted by dumdum

Has to do with the rear O2 sensor.Maybe the sensor is bad,shorted wire, or unplugged.You car should still be under warrenty right?For the 32 bit ECU cars (All STi's and 06+ WRX) this sensor is kinda important.I would get it fixed soon as ya can.

would that same code come up if the rear o2 sencer was not in the same position as stock (when installing TXS stealth TBE w/cat accedently put it on pointing to the drivers side) or does it rely on just being plugged in?

03 CrazyTaxi · 12-18-2008, 03:41 PM

Just needs to be plugged in. Is it a high flow cat? That may have something to do with it.

413TreX · 12-18-2008, 06:24 PM

yeah its a hiflo cat

03 CrazyTaxi · 12-19-2008, 07:42 PM

I'm not trying to sound like a jerk but were you thinking that a cat is a cat so you wouldn't need a tune?

The increased flow through the aftermarket cat will be noticed by the ECU.