p0420 catalyst system efficiency below threshold bank 1

Alrighty, so I'm running a bone stock N/A 2.5 SOHC.

Two days ago, CEL showed up, stayed through my drive to lunch yesterday, but when I left work for O RLY auto parts, the light was gone. Pulled the following code:

p0420 catalyst system efficiency below threshold bank 1

Cleared said code, the car ran a touch rough for a minute after I cleared it, but now it's running normally again. CEL hasn't come back.


Being that it's N/A and bone stock, I'd like to keep it that way, or close to it, so performance exhaust setups are out of the question. Being that I'm cheap, and I've heard OEM cats are bleeding expensive, I'm open to other options that might sacrifice some quietness for lower cost.

So, that leaves me with two questions:

1. Is this consistent with "dying cat. converter" symptoms?

2. If the cat is dying, what are good budget options for repair / replace?


Advice? Thanks in advance guys!

 

year/miles?

 

Yup, those year legacies go through cats like no tommorow. IMO ide just live with it, it shouldnt make it run rough at all though, must have been a fluke. Just an annoying CEL, The most budget approach would be to put some pipes in there, and sell the cats, and get a mechanical fix or resistor for the rear o2. Or just try a sparkplug anti fouler in the rear o2.

 

2000, 142k miles

 

I must have something wrong with me because I CAN NOT drive a car with an engine light on. It's infuriating to me.

As far as the fixes you listed, you lost me after the "replace cats with pipes" part. What mechanical fix would replace the o2 sensors? Is the anti-fouler device you mentioned a different type of sensor, or am I not thinking correctly here?


EDIT: and for that matter, how long could I reasonably expect to get out of a replacement? 40k?

 

90k or so miles. The anti fouler is just a spacer that the rear o2 screws into, it puts it further away from the exhaust stream so it cannot smell that the cats are gone or going. Napa would sell these.

 

Hell, if I can feasibly make it to 220k with a new cat, I'd probably just spring the funds for a new one.

All of this is assuming that code actually comes back...

 

If it came on once, and your car is not misfiring... then it will more than likely come back on. The cats for those are not cheap though, which is why lots of people just leave the light on... or cheap out and buy aftermarket cats which usually fail faster.

 

This!!!

 

So, would I be any better off with the OEM cat for $700 or whatever it costs than I would with the aftermarket bolt on cat for $375 with the 8 year 80k warranty?

 

EDIT: because if the failure rate of the aftermarket were as bad as failing just out of warranty at 81k and the OEM lasted 90-100k, would it be worth twice the price for the difference? Will it perform better or run quieter/smoother with the OEM to make it worth more?

 

Leave what you have for converters (its not like they're plugged and robbing power/mileage), spend $6 on a plug anti-fouler/mechanical fix and hope it works. If it does, WIN. It not, THEN look into other methods.

Or feel free to over complicate things, that's fine too. :biggrin:

 

If you can find aftermarket cats with that good of a warranty and they will stand behind it, go for it if you feel the need. I have yet to see a Subaru cat get plugged, if anything they burn a hole right through them. IMO Subaru just uses to picky of a rear O2 sensor.

 

I got the 420 code on my car and a few weeks later it was taking 20 seconds to get to 60. morries said it was a clogged cat and they fixed it for free because of the extended emissions warranty, which is why I asked about miles. sounds like he's out of that warranty period though.

 

The thing that's making me only question this instead of take action is that the car is performing exactly the same as it has since I've had it, which is as well as it probably ever did.

I'm just exploring my options and seeking advice. Trying to learn from all of y'all's mistakes. :hsugh:

So, if the light comes on, I'm going to get an anti-fouler spacer. If it continues to come on, or performance degrades, I'll act on it then, by actually replacing the cat.




To stir the pot some more, how often do the sensors go bad? Is it rare enough to just count it out as nearly impossible?

 

They can go out, but they would throw a different code.

 

There are many codes they can throw if they go bad.

High Input
Low Input
Heater element not working
Slow response
and I have seen them throw the inefficient code you speak of, too.

 

mmmmmmmmhmmmmmmmmm.....


Well, it's day 2 with no return of the CEL, so hopefully it was just a fluke. We'll see though.

On a lighter note, I'm thinking about buyin some Rallitek swaybars. Thoughts? :laugh:

 

It might take as long as 2 weeks.

 

I get this same efficiency code maybe twice a year, usually in the summer. No performance differences at all. No discernible problems. No other codes.

I just stop by Autozone and have them clear it and go on my merry way.

 

I also work at Morrie's, so I see this all the time, and you had one of the very, very, very rare ones.

 

Its all in your driving style. It can come back as in little as your first two drive cycles.

As for the rear O2 sensors going bad, it does happen, but far and few. There are some tests you can do to verify what it is, but you need the right scan tools to do this.

 

Same exact thing happened today. Still runs normally.

Is this spark plug anti-fouler thing you guys speak of something the store folks would know about readily?

 

Yes sir, they should know exactly of what you speak.