P0446-Evap Emmis Control System

[BigMattyD]

I can't wait to find out the cause of this mysterious problem!!!

 

matt

[Mikevan10]

Nipper,

 

I read through the good stuff that OB99 posted but I don't see why you would say "like i said, the car wasnt warmed up yet.". Why did you make that comment?

 

Like I said, I'll let you guys know what I did wrong (as soon as I come up with a good story si I don't look like too much of an idiot...).

 

Mike

[nipper]

Nipper,

 

I read through the good stuff that OB99 posted but I don't see why you would say "like i said, the car wasnt warmed up yet.". Why did you make that comment?

 

Like I said, I'll let you guys know what I did wrong (as soon as I come up with a good story si I don't look like too much of an idiot...).

 

Mike

 

When the car is cold, its in an open loop. This means that the computer is running off pre programed set points. At 138 degrees the car is not warm. Once the car reaches (i think it said) 154 degrees, the car is warmed up. The computer now goes into closed loop. This means that the car is now reading all the sensors and ajusting to them. This is where a faulty sensor will show up, unless it was a gross fault (open circuit or short).

 

nipper

[ferret]

Freeze Frame data is taken at time of the failure, car warmed up or not. If the failure happens during warm up, then the snapshot is taken then. Doesn't matter if it's during Open or Closed Loop operation.

 

Some driving cycles may take a week or 2 to set as they are set over a variety of driving conditions. Some may not be set for months as they require the vehicle to maintain a speed over 55mph for a period of time. So driving a car around town may never set that cycle. Also don't remember if it was in this thread, but early Subaru OBDII cycles were reset when the ignition was turned off. This didn't present a problem until some states started using the driving cycle settings as part of their emissions settings.

 

Mike, if you went after the wrong valve or solenoid, don't feel bad, Subaru has renamed these and refers to them in different parts of their own manuals by different names. Has happened to the best of us. Glad you finally determined your problem. Now just get out there and enjoy driving your car.

[nipper]

Freeze Frame data is taken at time of the failure, car warmed up or not. If the failure happens during warm up, then the snapshot is taken then. Doesn't matter if it's during Open or Closed Loop operation.

 

Some driving cycles may take a week or 2 to set as they are set over a variety of driving conditions. Some may not be set for months as they require the vehicle to maintain a speed over 55mph for a period of time. So driving a car around town may never set that cycle. Also don't remember if it was in this thread, but early Subaru OBDII cycles were reset when the ignition was turned off. This didn't present a problem until some states started using the driving cycle settings as part of their emissions settings.

 

Mike, if you went after the wrong valve or solenoid, don't feel bad, Subaru has renamed these and refers to them in different parts of their own manuals by different names. Has happened to the best of us. Glad you finally determined your problem. Now just get out there and enjoy driving your car.

 

i've seen the part names vary from manual to manual

 

we all get caught by that.

 

nipper

[OB99W]

Freeze Frame data is taken at time of the failure, car warmed up or not. If the failure happens during warm up, then the snapshot is taken then. Doesn't matter if it's during Open or Closed Loop operation.

True, and in the case of P0446, which is supposed to set based only on electrical characteristics, it indeed shouldn't matter. However, sometimes determining if a failure occurs or not with systems warm (and what the "snapshot" looks like, if the code does set) can be useful. Some electrical failures only show within a range of operational temperatures, and determining if that's the case can help in diagnosis.

 

 

[...]Also don't remember if it was in this thread, but early Subaru OBDII cycles were reset when the ignition was turned off. This didn't present a problem until some states started using the driving cycle settings as part of their emissions settings.

It's mentioned on the first page ("18") of the Endwrench article I linked to in post #47 of this thread.

 

 

Mike, if you went after the wrong valve or solenoid, don't feel bad, Subaru has renamed these and refers to them in different parts of their own manuals by different names. Has happened to the best of us. Glad you finally determined your problem. Now just get out there and enjoy driving your car.

I agree; relax Mike, most of us here will admit to having goofed on occasion, and the rest are probably lying (umm, I mean "the rest may have short memories") .

[Olnick]

Like I said, I'll let you guys know what I did wrong (as soon as I come up with a good story si I don't look like too much of an idiot...).

 

Mike

 

Okay, Mike . . . spill it!!!

[nipper]

Okay, Mike . . . spill it!!!

 

does it involve beer, or you turning to your buddies and saying "hey guys, watch this"

 

nipper

[Mikevan10]

does it involve beer, or you turning to your buddies and saying "hey guys, watch this"

 

nipper

 

Alright you guys. This is starting to get out of af hand, and although fun, it will end up making my simple but dumb mistake anticlimactic so I'll end it now.

 

No it did NOT involve beer (although I am wondering how you know so much about me...) nor did showing off come into play. What DID happen was (and here's where the picture should get foggy as I take you back to a simpler time...)

 

A little over two years ago the MIL (CEL to anyone who is not as well read on the subject - and, yes, I am prone to sarcasm ) came on in my wife's 1997 Subaru Legacy 2.2, 5-speed manual Brighton (yep, the top of the line...). I ignored it (shame on me) until I tried to get the car past PA state inspection. This being my first OBDII equipped car, I was not prepared for what I was to find out: You don't get a sticker if your MIL is on!!! Now, I've been doing pretty much all the maintenance on my vehicles since I was a kid (I'm an old man of 50 years now) but I do not have diagnostic equipment for electronics. ***At this point I can see that if I carry on this way, my story will take too long for me to type and for you to read so I will switch to just the facts:

 

Summer 2004 - CEL on. Would not pass emmissions inspection. DTCs were P0446 and one or more cyl misfire codes. Took it to the dealer (make that stealer) since the local repair shop/inspection station did not seem likely to diagnose the problems easily or quickly and I was at a loss with ODBII. Dealer installed new ignition coil and wires. Cleared codes. He told me something to the effect of "There is a P0446 code in history so that fault may pop back up. We recommend you have us replace the vent/purge/drain solenoid valve soon as you can. We don't have one in stock but can have it for you in a couple days.". I paid the massive bill for the ignition system work and RAN. But before I ran, I spoke directly with one of the Subaru mechanics and I asked him where this solenoid valve was located. This guy was aware that I was dealing with DTC P0446, by the way... He pointed out what I NOW understand to be the Purge Control Solenoid Valve!!! Well, as soon as I started the engine to dive away from the dealer the MIL came back on. Pissed off, I drove back to the local garage/inspection station and the guy there told me he had figured out how to get around the system and give me a sticker. What a relief. I believe he had just learned about the 5,000 mile rule, but whatever, I got my sticker.

 

Next, I ordered a Purge Control Solenoid valve from Liberty Subaru using the part number they gave me at my local Subaru Dealer/Stealer. When I received the part I installed it. I did not have a scanner so I could not clear (or read) the codes but at that time my (false?) understanding was that even if I had fixed the root problem, that my light may not go off right away but that it would after I reached sufficient "cycles", what ever they are. Well, the light never went off but, heck, car ran fine and I had my sticker.

 

Cut to about a month ago. Brought car to my local garage but this time he screwed something up when hooking up the "The System" and now he could not give me a sticker with the MIL on!! The Horror!!! My only recourse seemed to be to fix the problem(s). At this point I borrowed a scanner from a friend and read the codes. There were 4 or 5 of them. Cleared them and when I started the car the MIL was off for the first time in years!! But, as I stated way above in one of my first posts on this epic thread, the light came back on the second time I started the engine. Read codes, only one, P0446. The next couple week's worth of troubleshooting is well documented above, but, as you know, I was chasing the wrong solenoid valve!!! In my defense, I started out on this (wrong) track due to the dealer's advice. And when I started working on this almost 2 weeks ago, all I had was a Haynes manual. The Haynes manual, in the Emmisions Controls chapter, only addressed one solenoid valve in the EVAP system. I "ASSUMED" that this must be the valve I replaced 2 years ago. Also, the Haynes manual even only shows one (1) solenoid valve related to the EVAP system in the wiring diagram!

 

Although at least one of you guys made comments that in retrospect should have given me enough clues to question whether I had the right component, I was just too dense to see this until I finally got my hands on a Subaru factory manual and started studying the EVAP system schematics and wiring diagrams. I had one of those Eureka moments at about midnight Monday night and almost had to wake up the wife and kids.

 

Once I went after the right component, following procedure 10AJ1 in the factory manual led me right to the cause in about 5 minutes - An open circuit in the tank harness so signal was not returning from the solenoid to pin 35 on the ECM!

 

Like I said, a long story and a very frustrating experience, but, on the other hand, I do understand alot more about these systems and most valuable of all was getting to "work" with you folks who tried to help me out. I had seeked advice from this board in the past and, frankly, was disappointed. But I am now a believer. Some of you guys have great technical minds and the rest of us are lucky to have you around! Thanks again for those of you who took the time to take my comments, think about them and apply it to what you know about these systems.

 

Hats off to Nipper, Cougar, OB99W and Ferret. You guys are the real deal. Also thanks to Matty D for getting me the bible, without which it seems like no amount of wisdom was going to get me to finally find the truth!

 

And thanks everyone else for bearing with us. This Long Strange Trip is over. I am starting a new one now!!!!

 

Mike V

[Cougar]

Your welcome for the help Mike. Thanks for the feedback and glad you got the problem solved finally.

[OB99W]

Alright you guys. This is starting to get out of af hand, and although fun, it will end up making my simple but dumb mistake anticlimactic so I'll end it now.

 

[...]Although at least one of you guys made comments that in retrospect should have given me enough clues to question whether I had the right component, I was just too dense to see this until[...]

Mike, it may not be your fault, and I can get you off the hook (well, sort of ) . I just checked my copy of Roget's Thesaurus, and in section 308.20 both "drain" and "purge" are listed; apparently Roget thinks they're interchangeable terms! (I assume, therefore, that Peter Roget never worked on a Subaru. )

 

 

[...]This Long Strange Trip is over. I am starting a new one now!!!!

Thanks for getting back to us; it's nice to find out what the resolution was. I'm glad we could help, even if the path was a bit convoluted. Congratulations on the repair, and have a nice ride!

[Mikevan10]

Oh yeah, I wanted to bring up just that point of providing feedback. I have noticed what seems to be a tendency for troubleshooting threads here to die unresolved. Which, I guess, could mean the problem was bever solved or the person with the problem did not bother posting the solution (maybe because they ended up paying someone to resolve it for them?). This is only meant as constructive criticism. For the good of the whole, PLEASE advise the board of the resolution (even if it was burning the car down).

 

As far as enjoying the ride, I am afraid that at this point I am rather paranoid. I will feel alot better when I get an inspection sticker. Probably a good thing it's my wife's car. I'd be watching the dash instead of the road, and a nervous wreck at that.

 

Gimme a pre-1996 any day.

 

Mike V.

[Wayne Boncyk]

Mike - What an EPIC saga! Sorry I've been away from the forum for a few days, or I might have jumped in earlier. Not that I'd have had anything to add to the incredibly detailed advice that you got from everyone else here! I'm just dropping in now to say Kudos to all the guys who helped you out. This has been an incredibly enjoyable read, mostly because it reminded me of some of the longer threads I've been a party to over the past few years in this forum.

 

As my kids would say, you guys all rock! There is absolutely no better source of information on Subes anywhere else in the world -- and it is all the better for being from guys who actually work on their own machines -- the ratio of real useful info to BS is extremely high on this board, and it is wonderful to see that there are so many folks out there who value their machines so highly that they are willing to share their decades of combined knowledge with the rest of Sube owners around the world. Nice job, gentlemen!

[nipper]

Mike, it may not be your fault, and I can get you off the hook (well, sort of ) . I just checked my copy of Roget's Thesaurus, and in section 308.20 both "drain" and "purge" are listed; apparently Roget thinks they're interchangeable terms! (I assume, therefore, that Peter Roget never worked on a Subaru. )

 

 

 

heheheh you funny.

 

When i worked for the fuel cell company, i wrote the manuals and got to name the assemblies and parts when they werent named already. This is true for most engineers, they get to name thier own parts (i wrote the manuals and desighned processes and parts).

We ddidnt need no stinkin books, we just made it up as we went along. I even named one part "widget"

 

nipper

[Olnick]

As my kids would say, you guys all rock! There is absolutely no better source of information on Subes anywhere else in the world -- and it is all the better for being from guys who actually work on their own machines -- the ratio of real useful info to BS is extremely high on this board, and it is wonderful to see that there are so many folks out there who value their machines so highly that they are willing to share their decades of combined knowledge with the rest of Sube owners around the world. Nice job, gentlemen!

 

Amen to that. The knowledge here is fantastic. The willingness--and desire--to share and help others is phenomenal.

 

It's the way life should be. Thanks all.

[DCor]

What an incredible read!

All though not quite ready admit to a pinpointed diagnosis,

this P0446 journey sounds alot like the way mine is following!

 

In the history of invoices, provided by the previous owner of my 2000 OBW, this P0446/Current - Evaporative Emission System Vent Control Circiut malfuction code keeps rearing it's head, when analized by Delphi SBQC.

 

The last mention of it, while in the prev. owners hands was at a garage, he took it to faithfully for a couple years. Suspiciously, I think the problem never really got properly fixed, but prehaps....ignored!

 

Here's what they did to fix the DTC:

Found code P0446A evap vent control malfunction.

Removed pcm, probe pin outs from pcm, perform continuity tests on all wiring from pcm to evap system, wire to evap vent soleniod has high resistence, removed wiring harness shield and located damamged wire above evap cannister.

Repaired damaged wiring to evap vent control soleniod, solder and & heat shrink connections.

Re-did the Delphi SBQC and No DTC Present.....at that time.

 

I have now owned the car almost one year. The CEL light comes and goes every once in a while. It had been on for a few days, so I took to get the codes read last week. Guess what.....P0446 comes up again! I got them to clear it.

Last night while on my way home, after driving it the most I have since clearing the code & putting about 200kms on, at various speeds, the CEL comes back on. This morn I start it up and no CEL.

 

I know I need to do more investigating but without the CEL on would the code be read again?? Any other advice is appreciative.

 

Thanks.

Edited June 2, 2009 by DCor
Add-on

[Cougar]

Code P0446 indicates a circuit problem so something is either wrong again in the wiring between the ECU and the device or the device itself is intermittent. The problem may be due to a dirty connnector contact. There will be a code record stored in the ECU unless the memory has been lost.

[DCor]

Ok thanks, Cougar!

 

I'll get investigating more tomorrow.

Sure wish I knew where everything was on this car.

Took me 3 months to find the Trany fluid dipstick, it was

very well hidden!!!

[Cougar]

You can get factory services manuals on Ebay for a reasonable price. Most are on CDs.

[DCor]

I have found a couple on ebay already.

Thanks again, Cougar.

[Cougar]

You're welcome.

[Mikevan10]

Holy crap! I forgot what a lengthy process that was and how much great help I received at that time. And very funny that the thread would be resurrected just as I make an unrelated return to this board!

 

By the way, the PO446 has never returned.

 

I plan to do various maintenance on both my Subarus ('92 and '97) this summer so I'll probabaly be talking with you. Glad to see several familiar (and respected) names still active here!

 

Mike V

[DCor]

Well I'm actively investigating this P0446 code, again.

I have had the PURGE CONTROL SOLENOID VALVE off, cleaned the connector,

checked the tubes, all looks good there.

Took off the Cannister, Drain Valve, and Drain Filter, again cleaned the connector to the Drain Valve, all the tubes are in good condition there too.

 

My copy of the FSM does not direct you to the area on the car the parts are at. I am now looking for a couple more parts, but just can't find them. Need help...Please.

 

1) FUEL TANK PRESSURE SENSOR / ATMOSPHERIC PRESSURE SOLENOID VALVE

 

2) PRESSURE CONTROL SOLENOID VALVE

 

The pics of these items in my FSM make them look nice and simple to view, but not to me.

Thanks for any help in direction.

What else could I check out?

DC.

 

Guess I should ad it's a 2000 OBW 2.5, so you don't have to read that a few pages back!

Edited July 10, 2009 by DCor
missing info

[Cougar]

The fuel tank pressure sensor is on the right side of the fuel tank and the pressure control solenoid valve is on the left side of the tank. The atmospheric pressure sensor is about in the middle of the right side fender area.

 

As for the purge control solenoid valve, the electrical connection to it is having a problem. My data shows that a yellow/red wire ties to it and should have 12 volts on it. That wire is spliced in from the yellow wire tieing to the idle air control solenoid valve. The return side of the purge valve ties to pin A2 of the ECU on a red/green wire. Check the voltage getting to the solenoid and if you have full voltage there then the problem is on the return side of the circuit if the solenoid itself is ok. To see if the solenoid coil is ok remove it and check the resistance across the contacts. You should see something around 40 ohms possibly. That is a guess.

[DCor]

Thanks again Cougar, for your insight and advice.

 

I did a bit more investigating today.

Tested the wire to the purge control soleniod valve while the engine was running and got very close to 14v. When I did the Ohm cross pin check on the pcsv itself I got nothing, but when I put a contact on each pin I got 26.5 Ohms.

 

Now for the vaccuum cycle. The line to the top on the IAC sucks toward it.

When I connect that tube onto one of the pcsv ports it stops, and then that same line on the other port it flows though the valve. I am under the impression that it should be hooked up the former, as to stop the flow at the valve. Is this correct?

 

I called my local dealership and they told me the pcsv was roughly $250!!!

Thanks but no thanks. No one else stocks them around here. Is a wrecker a good option, you think?

 

I also did an inspection in and around the gas filling pipe. took the door off then the metal flange, and the plastic fitting that the door release cable and drainage tube is connected to, all very nice and clean in through there. Actually hard to believe it is a 2000 and Canadian winter driven!

But what a nightmare to try to get that tube and the door cable back in place, Wow. Is there a trick to that procedure. Where does the other end of that drain tube go to?

 

Another day of learning more about my pride and joy...HA!