Welcome to the North American Subaru Impreza Owners Club Monday March 18, 2019
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Go Back   NASIOC > NASIOC General > Newbies & FAQs

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads. 
Reply
 
Thread Tools Display Modes
Old 02-15-2019, 07:54 PM   #1
konaid
Scooby Newbie
 
Member#: 497833
Join Date: Feb 2019
Chapter/Region: AKIC
Location: AK
Vehicle:
2006 FX
White

Exclamation 2006 n/a data interpretation for P0420

Hey guys. I have some questions about the usual P0420 error.

Most likely i just need new cats, BUT i wanted to see if anyone could look at some numbers i got from my blue driver, to see if it makes sense, or if i should be looking into other problems.

A little history on the car:
Car: 2006 FX n/a
Mileage: 178k
Condition: Good, just did TB, WP, bearings, and some other stuff.
MPG: Normal for winter and driving style- about 22 hwy at 75.
Daily driver, but sometimes i step on it.

Any info would be great and appreciated.

Cheers
* Registered users of the site do not see these ads.
konaid is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 02-16-2019, 09:32 AM   #2
Jack
Add Lightness
Moderator
 
Member#: 13699
Join Date: Dec 2001
Chapter/Region: NESIC
Location: Hopkinton, MA
Vehicle:
not my president
(From General)

Default

When we had a P0420 in our 04 Outback, I did all the "usual" attempts to solve it without replacing the cats. Spark plug defouler, RC, diode. None worked and as we never planned to keep the car long, I would reset the code, wait until all but 1 monitor was ready and get the inspection sticker (my state passes with 1 monitor not ready). The "right" way to go about this is to analyze what the O2 sensor signals are, then repair based on these. I don't have the equipment to do this.
Jack is offline   Reply With Quote
Old 02-19-2019, 03:52 PM   #3
konaid
Scooby Newbie
 
Member#: 497833
Join Date: Feb 2019
Chapter/Region: AKIC
Location: AK
Vehicle:
2006 FX
White

Question

Quote:
Originally Posted by Jack View Post
When we had a P0420 in our 04 Outback, I did all the "usual" attempts to solve it without replacing the cats. Spark plug defouler, RC, diode. None worked and as we never planned to keep the car long, I would reset the code, wait until all but 1 monitor was ready and get the inspection sticker (my state passes with 1 monitor not ready). The "right" way to go about this is to analyze what the O2 sensor signals are, then repair based on these. I don't have the equipment to do this.
Anyone know how to interpret data? I have some logged. I will post a link. Well, if i can figure out how to share it...
konaid is offline   Reply With Quote
Old 02-20-2019, 09:01 AM   #4
Charlie-III
NASIOC Supporter
 
Member#: 30669
Join Date: Dec 2002
Chapter/Region: Tri-State
Location: USA, North NJ, 07456
Vehicle:
1998 Legacy 2.5GT
Silver Sleeper BK, 5MT

Default

Typical things I do....
Plugs and wires (if not cop ignition)
Check for exhaust leaks near the O2 sensor and forward.
Then look at O2 activity, at your miles, I would likely just replace it.
Check LTFT's, should be within +/- 8% or less. Too far from "0" could be other issues like front O2.
Charlie-III is offline   Reply With Quote
Old 02-20-2019, 01:48 PM   #5
konaid
Scooby Newbie
 
Member#: 497833
Join Date: Feb 2019
Chapter/Region: AKIC
Location: AK
Vehicle:
2006 FX
White

Default

Ok, that is good to hear. I think the LTFT is -5.5%-0. occasionally +2%. Seems reasonable then. So then would i change out the big front ugly monstrosity, or the rear cats? It blows my mind how there are so many in this car!
konaid is offline   Reply With Quote
Old 02-20-2019, 02:36 PM   #6
Jack
Add Lightness
Moderator
 
Member#: 13699
Join Date: Dec 2001
Chapter/Region: NESIC
Location: Hopkinton, MA
Vehicle:
not my president
(From General)

Default

Does this have the 2 pipes going through brass sections then joining? I know the 08 Outback N/A very well and those brass sections will wiggle enough to open holes. If you have a lift, look with the car running and see if there's a leak. Like Charlie mentioned, a leak can throw this code.
Jack is offline   Reply With Quote
Old 02-20-2019, 03:11 PM   #7
konaid
Scooby Newbie
 
Member#: 497833
Join Date: Feb 2019
Chapter/Region: AKIC
Location: AK
Vehicle:
2006 FX
White

Default

Hmm... I will have to look at that. I do not know the answer to that yet. Good point though.
konaid is offline   Reply With Quote
Old 02-20-2019, 04:00 PM   #8
Charlie-III
NASIOC Supporter
 
Member#: 30669
Join Date: Dec 2002
Chapter/Region: Tri-State
Location: USA, North NJ, 07456
Vehicle:
1998 Legacy 2.5GT
Silver Sleeper BK, 5MT

Default

Quote:
Originally Posted by Jack View Post
Does this have the 2 pipes going through brass sections then joining? I know the 08 Outback N/A very well and those brass sections will wiggle enough to open holes. If you have a lift, look with the car running and see if there's a leak. Like Charlie mentioned, a leak can throw this code.
Quote:
Originally Posted by konaid View Post
Hmm... I will have to look at that. I do not know the answer to that yet. Good point though.
My "go to leak test" is......car up a bit, engine running, have a helper block off tailpipe/pipes and you listen to and feel around for exhaust leaks. Could be a rotted pipe, rusted off bolts, old gaskets. Especially the "spring bolt" connection undermthe front passengers feet.

We will all assume that exhaust is only pushing out, but I have seen leaks within a foot or so of an O2 pop this CEL.
Charlie-III is offline   Reply With Quote
Old 02-20-2019, 04:36 PM   #9
konaid
Scooby Newbie
 
Member#: 497833
Join Date: Feb 2019
Chapter/Region: AKIC
Location: AK
Vehicle:
2006 FX
White

Default

Thanks... I am having some muffler work done very soon. I will try to have them help me look, while it is on the lift.


thanks
konaid is offline   Reply With Quote
Old 02-20-2019, 08:20 PM   #10
CaptainSlowbaru
Scooby Newbie
 
Member#: 445600
Join Date: Apr 2016
Chapter/Region: Tri-State
Location: Rafferty Subaru, PA
Vehicle:
2002 Outback Sport
Green

Default

Quote:
Originally Posted by konaid View Post
So then would i change out the big front ugly monstrosity, or the rear cats? It blows my mind how there are so many in this car!
There is only one monitored cat. Here's the diagram:



Red: catalytic converter
green: A/F sensor
blue: O2 sensor
pink: clean-up cat

Here's a rundown on sensor data in regards to diagnosing the cat. With your car warmed up and idling, the a/f sensor should hover around 1.00, the MAF should read about 2.5 g/s, and fuel trims should be less than 10% (positive or negative). If all of those are reading correctly, then look at the rear O2 sensor (also known as Bank 1 sensor 2). If it's reading steady (usually in the .700 range) the cat is good. If it's switching back and forth from low to high (example: .135 and .875), the cat is no good.

The "clean-up" cat is irrelevant as far as the P0420 code is concerned. The rear O2 sensor's job is to monitor the cat, and the clean-up cat is down stream of that sensor. You could theoretically hollow it out and the car would never know. Don't waste your money replacing that one.

If it is the cat, you would have to replace the entire "catifold" (as we call it). Unfortunately, they are not cheap. And swapping over all of the heat shields is a major PITA if all the bolts are rusted.
CaptainSlowbaru is offline   Reply With Quote
Old 02-21-2019, 02:57 PM   #11
konaid
Scooby Newbie
 
Member#: 497833
Join Date: Feb 2019
Chapter/Region: AKIC
Location: AK
Vehicle:
2006 FX
White

Default

Thank you. That is exactly what i needed to now. I will look at my data sets. I suspect it is just the damn catifold. That will be fun. Sounds like a project for spring...
konaid is offline   Reply With Quote
Old 02-21-2019, 03:12 PM   #12
konaid
Scooby Newbie
 
Member#: 497833
Join Date: Feb 2019
Chapter/Region: AKIC
Location: AK
Vehicle:
2006 FX
White

Default

Looks like my B1S2 is from like -3 to +2, and often at zero. That is cruise and city. So... i think i may have found the problem.
konaid is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

All times are GMT -4. The time now is 11:26 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2019 Axivo Inc.
Copyright ©1999 - 2017, North American Subaru Impreza Owners Club, Inc.