Welcome to the North American Subaru Impreza Owners Club Saturday May 30, 2015
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Normally Aspirated Powertrain

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 11-19-2001, 05:11 PM   #1
tmat3
Scooby Specialist
 
Member#: 2817
Join Date: Nov 2000
Location: NYC and Troy, NY
Vehicle:
2001 Impreza 2.5RS
BRP

Default CE Code : PO 0420 - Part II

Ok, so I got another CE light with the same code (PO 0420 : Catalyst Efficiency Too Low). I've been experienmenting and it turns out that the CEL comes on only with a Stromung rear section.

Now that I have a OBD-II scanner, I checked the freeze data. I have 3 freeze data given with the same CE code. Well, all 3 happened at more than 50mph, light throttle, and the coolant temperature exactly at 181F. All 3 had 181F. Why is that? Does the car run at 181F? I thought cars run around 190-200 depending on load. Does the ECU give out this CE code if the rear O2 sensor reads low temperature and 181F coolant temperature? Is that how ECU determines catalyst efficiency?
* Registered users of the site do not see these ads.
tmat3 is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 11-19-2001, 05:54 PM   #2
Julian
Scooby Specialist
 
Member#: 1182
Join Date: Mar 2000
Location: Ventura, CA
Vehicle:
MY00 RS
BRP

Default

The code should be triggered after a set period of time (allowing the cat to get hot enough not to trip it). That your coolant is the same temp is interesting, but could be nothing. Are you able to run the OBD scan while driving, as in, can you monitor the coolant temp and when it hits 181F, see if the CE light comes on? It might rule it out.

It would seem the rear section has a lot to do with this code, as those with the MRT header and mid-pipe, but stock back box didn't get the code...but installing the MRT (higher flow) back box brought on the code.

Or, maybe we just shouldn't be at part-throttle!
Julian is offline   Reply With Quote
Old 11-19-2001, 06:17 PM   #3
munkis
Scooby Guru
 
Member#: 1847
Join Date: Jul 2000
Chapter/Region: Tri-State
Location: brokenmotorsports.com
Vehicle:
Team Broken: V6 GF
rallyarmor.com

Default

what are the fuel trim readings?

Ive had a stromung cat back on my car forever now...no ce light, do you have an intake?

Jay McDade
Auto Tech--Lincoln/Mercury/Jaguar
www.hometown.aol.com/impreza25rs2000
munkis is offline   Reply With Quote
Old 11-19-2001, 07:33 PM   #4
tmat3
Scooby Specialist
 
Member#: 2817
Join Date: Nov 2000
Location: NYC and Troy, NY
Vehicle:
2001 Impreza 2.5RS
BRP

Default

I have Ganzflow w/ K&N filter. My SAFC is set to 0% right now (since August). My theory is that the rear O2 sensor is getting sensitive. In August, I had one CE light. In September, I had one CE light. In October, I had 3 CE lights. In November, today is the 2nd one. All of them are the same codes triggering at very similar conditions : low throttle, 55mph cruise, about 5 minutes after starting an engine after a long drive (i.e. after going to bathroom at a rest area on a highway).

What's fuel trim? Here I'll give you what I got for today's freeze data:

PID SUP : SUP
DTC FRZF : PO420
SYS STAT : CL 0 NA
LOAD : 16%
ECT : 181F
SHRT FT 1 : -2%
LONG FT 1 : -3%
MAP : 13inHg
RPM : 2838RPM
MPH : 63MPH
tmat3 is offline   Reply With Quote
Old 11-19-2001, 07:35 PM   #5
tmat3
Scooby Specialist
 
Member#: 2817
Join Date: Nov 2000
Location: NYC and Troy, NY
Vehicle:
2001 Impreza 2.5RS
BRP

Default

I also went to a dealer, but they had no clue. They keep on resetting the codes. I can do that at home!

Because it's not a harmful code or anything, I'm not so worried about it, but it sure is annoying. Damn California emissioned vehicle!
tmat3 is offline   Reply With Quote
Old 11-19-2001, 08:30 PM   #6
munkis
Scooby Guru
 
Member#: 1847
Join Date: Jul 2000
Chapter/Region: Tri-State
Location: brokenmotorsports.com
Vehicle:
Team Broken: V6 GF
rallyarmor.com

Default

SHRT FT 1 : -2%
LONG FT 1 : -3%

this is what I wanted to see, and it looks perfect

basically I wanted to see long fuel trim, if its up to high around 20% that means the ecu is compensating for a lean condition, so it enrichens the fuel mixture....rich equals cold....low exhaust temps and what not....but yours looks ok.

the only reason that the code is being set at the same conditions everytimes is because on obdII cares the exhaust catylist efficiency tests needs to meet exact predertermined operating conditions before it runs a cat efficiency test. let me see what I can dig up with this info, ill ask my shop foreman, he may have some good suggestions for you.

Jay McDade
munkis is offline   Reply With Quote
Old 11-19-2001, 08:34 PM   #7
munkis
Scooby Guru
 
Member#: 1847
Join Date: Jul 2000
Chapter/Region: Tri-State
Location: brokenmotorsports.com
Vehicle:
Team Broken: V6 GF
rallyarmor.com

Default

Can you monitor the O2 sensor readings with your scan tool, while the car is running.

make sure the upstream o2 sesnor is constantly switching it should never stay the same voltage once the it is warmed up.

the rear O2 sensor should be a pretty constant voltage.

see if you can monitor them, let me know whats going on.

Jay McDade
munkis is offline   Reply With Quote
Old 11-19-2001, 09:38 PM   #8
tmat3
Scooby Specialist
 
Member#: 2817
Join Date: Nov 2000
Location: NYC and Troy, NY
Vehicle:
2001 Impreza 2.5RS
BRP

Default

It seems that I can only check the front O2 sensor readings. Also, I can check this while idling or revving in neutral since I'm using a desktop. Anyway I'll post that here tomorrow morning/afternoon.

I have an Autometer A/F ratio gauge which is hooked to the rear O2 sensor. When I use stock exhaust system, the reading is more stable than when I use Stromung. When stock, the A/F gauge stays right in the middle when cruising. But, when I use Stromung, it stays a little on the rich side and usually stable. However, there are a few occasions when it moves between lean and rich while cruising.

Thanks McDade for your help!!
tmat3 is offline   Reply With Quote
Old 11-20-2001, 02:11 AM   #9
ImprezaRSX
*** Banned ***
 
Member#: 10955
Join Date: Oct 2001
Chapter/Region: NWIC
Location: Lake Stevens, WA
Vehicle:
07, 06,01,93 I have
4 domtuned subys

Default

no headers or anything?
I had the same problem after I installed my intake and headers.
The increase in flow, combined with the headers not holding in as much exhaust heat wasn't allowing the Cat to get hot enough to act efficiently. I wrapped the headers two weeks ago and VIOLA to more CEL (same code you were getting). I have Borla Headers, Stromung cat back, Ganz Flow immitation intake, K&N, power pulley, and a bunch of suspension crap that doesn't change my exhaust temp....
I'm also running an Autometer AF on the rear sensor, it acts just like you say, a little on the rich side with occasional sweeps towards lean (and drops off scale low when decelerating).

An EGT (exhaust gas temp) or a cat mounted thermometer might help you trouble shoot.

Mine was coming in at the exact same times you describe. Cruising down the freeway around 55 miles an hour... etc etc.

Hope this helps your trouble-shooting

Dominic
ImprezaRSX is offline   Reply With Quote
Old 11-20-2001, 04:25 PM   #10
tmat3
Scooby Specialist
 
Member#: 2817
Join Date: Nov 2000
Location: NYC and Troy, NY
Vehicle:
2001 Impreza 2.5RS
BRP

Default

I don't have an aftermarket header. The only thing I have for external engine mod right now is :
Ganzflow, K&N air filter, and Stromung rear-section (w/ stock midpipe).

I took out the plastic piece below the right bumper turning signal to increase the airflow. Ever since then, the manifeld pressure at idling decreased by 30-50mmHg after I removed the plastic piece. But, if I put it back on, the manifeld pressure increases (goes back to original). Could that cause the CE light to pop up because there is more inflow, leading to cooler overall internal temperature? I don't see how though. The milesage hasn't improved or decreased, but performance has. So, nothing quite explains why I get CE lights.

I also fixed a broken exhaust gasket between the rear section and the midpipe. That didn't prevent the CE light either.

Anyway, I checked the O2 sensor readings. I cannot check the front O2 sensor. The rear O2 sensor is very stable at idling or 10% throttle cruise. Other sensors (MAP, TPS, ECT, Intake Temp, Load....) read perfectly.
tmat3 is offline   Reply With Quote
Old 11-21-2001, 10:20 AM   #11
Julian
Scooby Specialist
 
Member#: 1182
Join Date: Mar 2000
Location: Ventura, CA
Vehicle:
MY00 RS
BRP

Default

tmat3, a bit off topic, but you're saying there's a benefit to removing the front vent that feeds the fenderwell? Interesting...
Julian is offline   Reply With Quote
Old 11-21-2001, 08:52 PM   #12
ImprezaRSX
*** Banned ***
 
Member#: 10955
Join Date: Oct 2001
Chapter/Region: NWIC
Location: Lake Stevens, WA
Vehicle:
07, 06,01,93 I have
4 domtuned subys

Default

If I understand this right...
MAP sensors are a bit backwards than what you would think.
Apparently when you add high flow components, it makes the engine run more towards the rich side.
At higher throttle the vacuum in the intake drops(point 3) due to the butterfly valve being open more- (this creates less of a pressure drop accross it and therefore the drop in vacuum.)
The intake piping on the other side of the TB also has a vacuum(point 2) due to the restrictive nature of the intake piping. When the throttle body is full open, the vacuum in the intake manifold (point 3) is dependent on the total restriction of the system. If you decrease the restriction in the intake pipe(points 1-2) then total restriction goes down and therefore there is less vacuum at point 3. MAP sensor senses the vacuum and affects the fuel maps. The less the vacuum, the more fuel needed (due to more air, right?) So when you add these low flow components, you drop total vacuum at all points in the rpm band and therefore the map sensor tells the engine it needs more fuel. Therefore you run more rich. What about the O2 sensor you ask? Well it provides it's input. However the system is airflow dominant. The o2 sensor is just a feedback leg. The MAP sensor has a stronger affect on the fuel maps than the o2 sensor.

If your car is running too rich, the cat won't be able to compensate due to the quantity of unburnt fuel. However, the front o2 sensor won't be out of it's allowed voltage range. That means that the system will see the car running fine, but the rear o2 sensor will tell the system that the cat isn't doing it's job well enough. And VIOLA CE light.

Make sense? It's a little confusing at first, but read through a few times, look at the drawing (even though it is really crude) and I bet you'll understand.

Dominic
ImprezaRSX is offline   Reply With Quote
Old 11-22-2001, 09:33 AM   #13
tmat3
Scooby Specialist
 
Member#: 2817
Join Date: Nov 2000
Location: NYC and Troy, NY
Vehicle:
2001 Impreza 2.5RS
BRP

Default

So, are you saying my car is running a lot richer than I am anticipating when I increase the total air inflow to the engine? This is why I need an EGT. I diabled SAFC fuel compensation capability entirely last night (I basically disconnected the yellow wire to the MAP wire) and put the original plastic piece back into the hole under the bumper turning lights. We'll see what happens.
tmat3 is offline   Reply With Quote
Old 11-22-2001, 10:14 AM   #14
ImprezaRSX
*** Banned ***
 
Member#: 10955
Join Date: Oct 2001
Chapter/Region: NWIC
Location: Lake Stevens, WA
Vehicle:
07, 06,01,93 I have
4 domtuned subys

Default

Use the SAFC. only instead of richening, lean it out a little bit.
It's worth a try. Drop it down a couple percent 'til the A/F reads the lower two or three yellows (STOICH). You have to do this over a day, of course, slowly so the car can try and compensate a bit on it's own. But the only way you'll get your mixtures right is some sort of electronic component.... or put the stock stuff back on. Who the heck would want to do that, right? The SAFC's adjustablility is +/- 50%, right? That's more than enough.
ImprezaRSX is offline   Reply With Quote
Old 11-22-2001, 03:24 PM   #15
munkis
Scooby Guru
 
Member#: 1847
Join Date: Jul 2000
Chapter/Region: Tri-State
Location: brokenmotorsports.com
Vehicle:
Team Broken: V6 GF
rallyarmor.com

Default

where did you come up with that info??

the o2 sensors are what the ecu uses to determine fuel ratio, not the map sensor.

According to his fuel trim readings he is not running rich or lean.

Jay McDade
munkis is offline   Reply With Quote
Old 11-23-2001, 11:27 AM   #16
SubyTechMaster
Scooby Specialist
 
Member#: 4423
Join Date: Feb 2001
Location: Placerville, CA USA
Vehicle:
'04 08 Tribeca, SVX
Gold, Maroon

Default

Actually, according to his Freeze Frame, he is running slightly rich. Subarus run + numbers on the Short Term and 0 on the Long Term. For anyone unfamiliar; 0 = Stoichiometric, - is taking away fuel, + is adding fuel.

This may be normal. Since this vehicle is running an A/F sensor in the front this may be how the ECU tests the Cat. Richen the mixture and make the A/F see rich and look at the rear O2 to make sure the Cat is working. The Service Manual doesn't give the test parameters.

The Catalytic Converters on 2000 and newer are very fragile, if the are run rich just once they can be ruined, I've done it. If the code is coming up more frequently it may be a bad Cat.
SubyTechMaster is offline   Reply With Quote
Old 11-23-2001, 02:25 PM   #17
ImprezaRSX
*** Banned ***
 
Member#: 10955
Join Date: Oct 2001
Chapter/Region: NWIC
Location: Lake Stevens, WA
Vehicle:
07, 06,01,93 I have
4 domtuned subys

Default

Quote:
Originally posted by McDade
where did you come up with that info??

the o2 sensors are what the ecu uses to determine fuel ratio, not the map sensor.

Jay McDade
Ok.
I'm not the kind of guy to get in arguments or pissing matches on these forums. If I am incorrect, please tell me what the MAP sensor is for, and why it affects the drivablility and characteristics of an engine so drastically.
I believe that you are mistaken. The O2 sensors ARE a part of the total equation, but they are the fine tuning of the mixtures, where the MAP sensor combined with the temp sensor (intake) tell the ecu the quantity and quality (how dense) of the air entering the engine.

Dominic
ImprezaRSX is offline   Reply With Quote
Old 11-23-2001, 03:41 PM   #18
SubyTechMaster
Scooby Specialist
 
Member#: 4423
Join Date: Feb 2001
Location: Placerville, CA USA
Vehicle:
'04 08 Tribeca, SVX
Gold, Maroon

Default

You are on the right track. The O2/AFR is used to fine tune the mixture - when in closed-loop. According to the Freeze Frame data, this vehicle is in closed-loop at the time of the CEL.

The MAP/Air Temp. sensor combination tell the ECU the amount of air being drawn into the engine. MAP with the TPS and RPM are used to determine Engine Load. Engine load determines amount of fuel injector duration (and volume of fuel). The O2/AFR fine tune the mixture by telling the ECU if a complete combustion is occuring. Too many variables interfere with combustion and the ECU looks at downstream exhaust to make adjustments.
SubyTechMaster is offline   Reply With Quote
Old 11-23-2001, 04:46 PM   #19
BugBomb
Scooby Specialist
 
Member#: 1342
Join Date: Apr 2000
Chapter/Region: MAIC
Location: Pennsylvania, USA
Vehicle:
99 OBS & SUXASS
May your line be smooth

Default

This is all well and good, but it doesn't have much to do with the Catalyst efficiency code that everyone is getting from exhaust upgrades. The problem is simply boiled down to the Cat. The fuel mixture can vary all you want it to, the computer still only compares the readings between the two O2 sensors. When the front monitor reads at a certain voltage, the rear should read similar but at a lower voltage and at a later time. It is the comparison between the sensors that the ECU reads as a problem. If you get this code, your Cat is not working efficiently enough for the computer. You have few options. You can get a new cat, you can simulate the rear O2 sensor, or you can attempt to alter the signal from the rear O2 sensor so that the computer will be happy with it.

Keep in mind that the Catalyst system, including the rear O2 sensor, is for emissions only and will in no way affect the performance of the motor.
BugBomb 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

Similar Threads
Thread Thread Starter Forum Replies Last Post
Who's got the fastest Subaru in Houston?: Part II jefersun Texas Impreza Club Forum -- TXIC 41 06-20-2006 04:41 PM
CT : APEXi Super AFC II (SAFC), RS 6 spoke wheels + a few other parts GottaREX Private 'For Sale' Classifieds 23 11-24-2005 09:01 PM
thanks bill...asheville weekend part II..ce light on steve_d South East Region Forum 6 09-08-2003 11:35 AM
Part II : WRX vs S4 alvyman Proven Power Bragging 21 08-01-2003 07:17 PM
CE code : PO 0420 tmat3 Normally Aspirated Powertrain 11 10-27-2001 07:26 AM


All times are GMT -4. The time now is 12:39 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2015 Axivo Inc.
Copyright ©1999 - 2015, North American Subaru Impreza Owners Club, Inc.