Evap System code.......frustrating!

[skibumm100]

Hi guys (and gals),

 

98 Legacy GT, 2.5L DOHC. Well, after spending the better part of last February and March getting cozy with the innards of the 2.5 DOHC, I've run into another issue. We have an annual inspection here in NH and the car did fine on the safety part but failed emissions. They don't use a sniffer, they check codes on OBD II vehicles. My car has had a check engine light on for code PO 443, Evaporative Solenoid Valve, for some time. I can reset it with the laptop and it will stay out for a short time then comes back. So I reset it before going for inspection but now it will only stay out for one start. I have no problem with fixing this for mother nature's sake. Problem is.... there doesn't appear to be anyhting wrong, except for the code. I have a Haynes manual that is just about worthless but better than nothing. Here's what I have done so far:

 

1.) Checked the resistance across the terminals for the evap solenoid valve(or so I thought, tee hee). Spec is 10-100 ohms.....it's 26 ohms.

 

2.) Checked for voltage at the valve, KOEO. I've got 12VDC at the plug when disconnected. I also checked it after it was plugged into the valve and I still had good voltage so the valve isn't dragging the voltage down. I can also ground the ECM side of the plug and the valve clicks so the valve appears to be good also.

 

3.) I've rung out the wiring from the valve to the ECM. It all looks good. I had about 0.3 ohms resisitance for the wire running from the valve to the ECM. Haynes had the colors wrong(can you tell I'm on the wrong track here). The wire from the valve to the ECM is brown with a yellow stripe, not white/blue. I backprobed the ECM plug on the correct (wrong!) wire and had 11.8 VDC at the ECM with the KOEO.

 

I'm running out of ideas. I hate to just start changing out parts.

 

Does anyone have any other ideas on what to check? What other years have an ECM that would be interchangeable with mine? That's the only thing I can't really check.

 

*edited to point out my mistakes...read on if you dare*

[skibumm100]

An update...

 

I checked for voltage at the ECM pin coming from the solenoid valve by back probing the plug again. I got battery voltage KOEO, when I turned the key and started the engine, I still got battery voltage. The ECM should ground that pin through the circuit used to control the valve, correct? (it will if your on the right circuit bozo!) I checked resistance to ground with the ECM plug connected. I got around 12K ohms with the KOEO and around 7K ohms with it running (this was a bad idea as pointed out later). That was checked with the solenoid purge valve unplugged at the back of the car. I am thinking bad ECM but would like to hear from the experts. Does anyone have a factory service manual that they could look at to see what else I can check for PO443?

 

* edited to point out general buffoonery...wait... did I spell buffoonery right?*

[skibumm100]

Well, it's official.....I'm an idiot. (just pointing out the obvious, my specialty) I was posting this in the wrong sub-forum under "Older Generation Subaru's" and have been searching that same sub-forum for solutions. I had thought I'd asked this question before but couldn't find my old post. The old post was in "Newer Generation Subaru's" and Cougar had been kind enough to post a reply. I had worked on this problem but dropped it to work on a different problem and was prompted to get back to fix this one after failing my NH inspection. I still have one question about this evap system. My Haynes manual says this circuit should be the white/blue wire, Cougar's reply says it should be the white/blue wire. The valve I'm looking at has a brown/yellow wire. Is there a second evap solenoid valve somewhere that my Haynes manual doesn't mention? I saw something about a "second" valve in one of the posts I found here http://www.ultimatesubaru.org/forum/showthread.php?t=63955.

 

*the plot thickens*

 

 

Sorry about the confusion....I'm not sure I've cleared it up yet.

 

Here is my earlier post:

 

http://www.ultimatesubaru.org/forum/showthread.php?t=82144

 

Thanks!

 

*edited just for good measure*

[OB99W]

[...]Here is my earlier post:

 

http://www.ultimatesubaru.org/forum/showthread.php?t=82144

Actually, the following is your previous post concerning this problem:

http://www.ultimatesubaru.org/forum/showthread.php?t=77287

 

The original discussion began here:

http://www.ultimatesubaru.org/forum/showthread.php?t=60858&page=2

[OB99W]

[...]I checked for voltage at the ECM pin coming from the solenoid valve by back probing the plug again. I got battery voltage KOEO, when I turned the key and started the engine, I still got battery voltage. The ECM should ground that pin through the circuit used to control the valve, correct?

AFAIK, not all the time -- otherwise, what would be the point of having the ECU control it?

 

 

I checked resistance to ground with the ECM plug connected. I got around 12K ohms with the KOEO and around 7K ohms with it running.

Checking resistance in a powered circuit is almost never a good idea; things can get damaged, and the readings are rarely accurate. The proper way to test is via voltage readings under operating conditions. ECU Pin 72 should pull down to below 1 volt when the purge control is activated.

 

 

That was checked with the solenoid purge valve unplugged at the back of the car. I am thinking bad ECM but would like to hear from the experts.

P0443 is "EVAP System Purge Control Valve Circuit Low Input". I added the emphasis because that would seem to indicate that your ECU is not seeing battery voltage (greater than 10 volts) at Pin 72. You said "I backprobed the ECM plug on the correct wire and had 11.8 VDC at the ECM with the KOEO."; assuming that means you made the measurement right at ECU pin 72, it should have seen sufficient voltage. Is there any possibility that the ECU connector (B84) isn't making good contact?

 

 

Does anyone have a factory service manual that they could look at to see what else I can check for PO443?

You seem to have tested for the things the FSM suggests (voltage, wiring opens, solenoid resistance, etc.). The first test in the FSM is for greater than 10 volts at ECU pin 72 with key ON; if that's there, the FSM indicates that even if the MIL is lit, "the circuit has returned to a normal condition at this time" and "probable cause is deterioration of multiple parts". I'm not sure I agree with that second quote, however.

 

I'm not certain about this, but D-Check mode may cycle the purge control valve solenoid. You could try warming the engine, shutting it down and connecting the green under-dash connectors, then run D-Check. Monitor the voltage across the solenoid while D-Check is running.

[skibumm100]

OB99W,

 

Thanks for the reply. I need to double check that I'm on the 72 pin. I found the pin I'm checking by matching the color of the wire at the purge valve plug (brown w/yellow stripe) and checking continuity to the ECU harness plug with a multimeter and a really long jumper.

 

* I was on an evap valve....just the wrong one*

 

"P0443 is "EVAP System Purge Control Valve Circuit Low Input". I added the emphasis because that would seem to indicate that your ECU is not seeing battery voltage (greater than 10 volts) at Pin 72. You said "I backprobed the ECM plug on the correct (incorrect!) wire and had 11.8 VDC at the ECM with the KOEO."; assuming that means you made the measurement right at ECU pin 72, it should have seen sufficient voltage. Is there any possibility that the ECU connector (B84) isn't making good contact?"

 

If I'm on the correct pin (72), I am seeing the voltage. The plug and pins look to be in excellent shape. It should be making good contact.

 

How do I determine if I'm on pin 72? Is there an ECU plug diagram somewhere? Do I just count pins?

 

* I was on pin 35, not 72*

 

"I'm not certain about this, but D-Check mode may cycle the purge control valve solenoid. You could try warming the engine, shutting it down and connecting the green under-dash connectors, then run D-Check. Monitor the voltage across the solenoid while D-Check is running."

 

I'm not familiar with D-Check. Is there anywhere i can read up on it? I'll try a search here first.

 

Thanks again!

 

*edited because I can*

[OB99W]

Thanks for the reply.[...]

You're welcome.

 

 

How do I determine if I'm on pin 72? Is there an ECU plug diagram somewhere? Do I just count pins? [...]

See attachment.

[skibumm100]

Thanks for the pic!

 

I'm also pretty sure that's not the pin I'm on.

 

*DUH!*

 

I will take a look and see what pin it is that has the brown/yellow wire. (it's pin 35) I was a little concerned that I wasn't on the correct pin because of the color coding discrepency. I guess I need to go back to square one. PO443 is evap purge valve. It's located at the carbon canister next to the spare tire well at the right rear corner of the car. It has two wires going to the plug. On my car one is brown with a yellow stripe. The other is yellow w/red, if I remember correctly. The yellow w/red is 12VDC supply when the key is on.

 

* I still haven't put two and two together yet....well I did... but I got five*

[skibumm100]

OK, I looked at my ECU plug again, B84. Looking at the pic you posted, that's half of the plug, hence the squigly double line. I am also assuming that the view of the B84 plug in the pic is looking at the back (wire side) of the plug. If that is indeed the case, pin 72 is located on the bottom row near the top of the plug when it's inserted into the ECU. It is a white w/blue stripe wire as shown on the schematics. This all makes sense. When backprobed with KOEO, I did not find any voltage at that pin. That would explain the CEL and trouble code. Now, the questions I have are these:

 

1.) What is that solenoid valve that is located next to the carbon canister at the back of the car? It doesn't have a white w/blue wire going to it.

 

2.) Where is the evap purge control valve located?

 

3.) Where is the "Main Relay" located? This is supposed to supply 12VDC to the purge valve. Haynes shows it on the schematic but doesn't show a location for it.

 

FWIW, the "mystery" valve I have been working on has a brown w/yellow wire that goes to a pin on the other half of the ECU plug (not shown). I believe it's pin 35. That wire rings out to the brown w/yellow wire at that valve.

 

I hope I'm on the right track. I believe this "other" valve was eluded to in another post about PO446 but the post ended without decribing the location of the two valves.

[skibumm100]

Excerp from a post by Mikevan10:

 

"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!!!!"

 

He was dealing with PO446. His problem was the valve I have been working on. My code is PO443. It is now my understanding that this is a DIFFERENT valve.

 

Hopefully, I can get on the right track and get this fixed.

[OB99W]

[...]PO443 is evap purge valve. It's located at the carbon canister next to the spare tire well at the right rear corner of the car.[...]

Yes, P0443 is for the purge valve. No, the purge valve is not the one at the canister (that's the vent control valve). More to follow...

[skibumm100]

NOW WE'RE COOKIN' WITH GAS!!!!!

[OB99W]

OK, I looked at my ECU plug again, B84. Looking at the pic you posted, that's half of the plug, hence the squigly double line. I am also assuming that the view of the B84 plug in the pic is looking at the back (wire side) of the plug.[...]

Yes, half the connector is shown, being back-probed (see the lower left depiction in the diagram I posted).

 

 

1.) What is that solenoid valve that is located next to the carbon canister at the back of the car? It doesn't have a white w/blue wire going to it.

Answered above.

 

 

2.) Where is the evap purge control valve located?

Right beneath the cylinder #3 portion of the intake manifold. (Cylinder #3 is left/rear when facing the engine from the front of the car.) It may be easier to spot if you stand at the passenger side fender and look from the rear of the engine.

 

 

3.) Where is the "Main Relay" located? This is supposed to supply 12VDC to the purge valve. Haynes shows it on the schematic but doesn't show a location for it.

The main relay supplies power to several things; if it were the problem, we wouldn't be discussing P0443.

 

 

[...]I hope I'm on the right track. I believe this "other" valve was eluded to in another post about PO446 but the post ended without decribing the location of the two valves.

Yes, and light at the end of the tunnel probably isn't from the headlight of an oncoming train.

[OB99W]

Excerp from a post by Mikevan10:

[...]

He was dealing with PO446. His problem was the valve I have been working on. My code is PO443. It is now my understanding that this is a DIFFERENT valve.[...]

Exactly! The vent and purge valves do seem to get people confused.

 

 

NOW WE'RE COOKIN' WITH GAS!!!!!

Let's hope!

 

 

For future reference:

The ECU connector pins are numbered consecutively. For example, continuing past pin 30 for five more, you'd be at pin 35. The last one in that row is 44; the count then jumps down to the beginning of the next row, beginning at 45, etc.

[skibumm100]

 

For future reference:

The ECU connector pins are numbered consecutively. For example, continuing past pin 30 for five more, you'd be at pin 35. The last one in that row is 44; the count then jumps down to the beginning of the next row, beginning at 45, etc.

 

Yep, in my confused state I was at least able to count pin locations. That's how I figured it was 35.

 

I can't wait to get home and actually see the purge control valve with my own two eyes. Thank you SOOOOOOOOOOOOOOOOOOOOOOOOOO MUCH for helping me out! The Haynes manual really doesn't give you much help on this system. It almost points you in the wrong direction. Two halves of different stories. Put them together and what do you get.......bad info. I am forever indebted.

 

Gregg

[Skip]

Gregg, good luck on this one

" I can't wait to get home and actually see the purge control valve with my own two eyes"

 

You might see it but getting to it to replace it.

That is another bunch of bannanas.

 

OB99W is spot on when he says

"Right beneath the cylinder #3 portion of the intake manifold."

 

When mine went bad, I left the old one in place

and replumbed a new one mounted on top of the manifold.

[OB99W]

Gregg, I'm glad I was able to help move things along. However, how about if I don't " " until the problem is fully resolved?

[OB99W]

Gregg, good luck on this one

" I can't wait to get home and actually see the purge control valve with my own two eyes"

 

You might see it but getting to it to replace it.

That is another bunch of bannanas.

[...]

Yes, it's a bit tight in there. A couple of hoses (in addition to the ones going to the purge valve itself) may have to be disconnected to make life easier. That's one of the reasons I'm holding off on the dancing banana.

 

By the way, Gregg, if you get as far as installing the new valve where the old one was, the correct torque for the bolt is only about 12 ft-lbs.

[skibumm100]

It's possible this could be....gulp.....self induced. I'm not saying I didn't get all of my plugs and hoses put back together when I put the engine back in but.....well....there's a lot of them....and ....ummmm... it's possible something like that COULD have happened. I need to check when I get home. I am just happy to be working on a problem that is just valves and wires. This should be much better than the alternative I was looking at (new ECU). Thanks again for your help! I was going nowhere fast....and making good progress BTW. Thanks for taking the time to walk a Subie Newbie through the process.

[Skip]

After you get to the valve

measure the resistance of the solenoid

coil.

 

It should be around 35 ohms

IF it reads infinite (open) ->

You have your problem.

 

These solenoids have been a bane of all series Subaru

engines.

 

I replaced mine with a Honda version of the same valve.

Seems to be a better made part.

(search the old gen forum for "purge")

 

I will try and find a picture of where I mounted mine if

you are interested.

[skibumm100]

Thanks Skip!

 

I will check the resistance across the coil. How much do these things cost and are there alternative sources besides the dealer. My local Subaru dealer isn't very competitive on price. I bought all my genuine Subaru part from Jamie and even with shipping included, I saved a boatload of money.

[skibumm100]

I went out and checked out the car when I got home. I opened the hood, looked under the #3 intake runner and there it was, the famed purge control solenoid valve. How could I have missed it. It's sitting right there, buried under that stuff. Just a short distance away was the plug that was supposed to be connected to said valve.(I told you I was an idiot!) I missed reconnecting that plug when I reassembled the engine. Just for giggles I checked the resistance of the coil. It was around 26 ohms....perfectly fine and in spec. I plugged the pigtail into the valve and grabbed my laptop. Booted that baby up and started my scanner. I turned the key and it cranked and cranked and cracked and sputtered and cranked and sputtered and....well, you get the idea....no start. I thought to myself, "You really screwed something up this time." I thought "fuel pump going bad?"....."ignition problem?"....etc. The gas gauge read 1/8 of a tank but the little gas pump light was flickering when I was cranking it. I stopped myself from getting carried away and said, "Sounds like it's out of gas". When I couldn't get the car started, I stuck my head in the house and said, "Honey, have you been having trouble with the car starting?" She said, "Oh yeah, I forgot to tell you I couldn't get it started this morning so I took the truck instead." So the first thing I tried was to dump 4 gallons of gas in the tank. Cranked it and voila, it started right up. I guess my gas gauge is on the fritz because it never used to run dry at 1/8 of a tank. I reset the code with the laptop and restarted the car several times and I had no codes, zero, nada. So, all is right with the world, excepting my gas gauge...and I can live with that.

 

Thanks again for all the help! Hopefully, this thread will help someone else down the road.

[OB99W]

I went out and checked out the car when I got home. I opened the hood, looked under the #3 intake runner and there it was, the famed purge control solenoid valve. How could I have missed it. It's sitting right there, buried under that stuff. Just a short distance away was the plug that was supposed to be connected to said valve.(I told you I was an idiot!)[...]

Not an idiot, just human.

 

 

Thanks again for all the help! Hopefully, this thread will help someone else down the road.

You're very welcome. Congratulations . Thanks for getting back to us with the result. Now I can :banana: !

[skibumm100]

Dancing banana's all around! They're on me! It's sticka time!

 

:banana:

:banana: