NEED HELP Evap Large Leak

Pygot

Original poster
Member
Dec 6, 2019
82
RI
Hi all, I have an 08 97x. Have replaced fuel canister, Rollover valve, gas cap and still am getting an evap code after about 100-200 miles of driving. Got codes read at stealership and they thought it was rollover valve (obv not). Now Im thinking it is the pressure sensors on top of the tank. No leaks when smoke tested. Any ideas or thoughts? Thanks
 

christo829

Member
Dec 7, 2011
497
Fairfax, Virginia
Did they actually give you the code #? There are also some valves that could potentially lead to a problem, though if those fail outright they usually throw their own code. Possibly one of them is leaking at a connector, but still talking to the PCM properly. Did you use an AC Delco cap? I had
an aftermarket cap on mine that didn't seal right, but that threw a small leak code.

Good Luck!

Chris
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Maybe the fuel pump seal? Or the top of the fuel pump module can rust through.

And yeah, having the actual code might help.
 

Pygot

Original poster
Member
Dec 6, 2019
82
RI
Did they actually give you the code #? There are also some valves that could potentially lead to a problem, though if those fail outright they usually throw their own code. Possibly one of them is leaking at a connector, but still talking to the PCM properly. Did you use an AC Delco cap? I had
an aftermarket cap on mine that didn't seal right, but that threw a small leak code.

Good Luck!

Chris
Yes I have the ac delco cap and I will get the exact code tomorrow when I stop by my mechanics. Sorry to not have it on hand
 

Pygot

Original poster
Member
Dec 6, 2019
82
RI
Maybe the fuel pump seal? Or the top of the fuel pump module can rust through.

And yeah, having the actual code might help.
Yea I realize that will have it tomorrow my bad. Also I have replaced the whole fuel pump module. Forgot to mention that
 

Mooseman

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Dec 4, 2011
25,262
Ottawa, ON
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Mooseman

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Dec 4, 2011
25,262
Ottawa, ON
He said he already smoked it and the code is a circuit issue.
 
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mrrsm

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NP... FWIW... Just making this suggestion based upon the possibility that the OP himself did not get the chance to do the work. If not, he'll never know whether or not "The Dealership" Tech actually did any work other than 'reading the codes'. If they DID .. Why didn't they detect the source of the problem? And just wondering what THAT visit cost him.
 
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Pygot

Original poster
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Dec 6, 2019
82
RI
NP... FWIW... Just making this suggestion based upon the possibility that the OP himself did not get the chance to do the work. If not, he'll never know whether or not "The Dealership" Tech actually did any work other than 'reading the codes'. If they DID .. Why didn't they detect the source of the problem? And just wondering what THAT visit cost him.
My neighbor who is a recert master tech did it with me so safe to say there is no actual leak. He hates working on pieces of shit lol but he put the tahoe springs in it too
 
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Mooseman

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Dec 4, 2011
25,262
Ottawa, ON
They should be the same. There were only some minor variances with options and BCM functions.
 

Pygot

Original poster
Member
Dec 6, 2019
82
RI
So update I have had the purge valve replaced and the wiring. Nothing. So maybe it is in the PCM itself? This part is where I need help bc it is a littoe bit beyond my knowledge
 

budwich

Member
Jun 16, 2013
2,027
kanata
what actual wiring did you replace... from where to where?

Based on limited readings, not sure about the P0445 being "shorted purge valve" code. I think its one of the possibilities (ie. short) but there are other electrical conditions (open) that may cause a "similar reaction". Testing of the electrical path would be a good idea.... hence the first question as I am not sure about "replace the wiring" which seems kind of extreme and involves "playing" with the PCM connectors which usually is not a good idea.

Note: the system does not have the ability to detect a short in the purge solenoid circuit.
 
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Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Are you sure about that code? I just searched GM-SI and there is nothing about the P0445 code. The info I got for that code is a generic OBD code that can apply to multiple brands however GM is not listed.


Information for specific makes
  • P0445 AUDI EVAP System Purge Control Valve Circuit Shorted
  • P0445 CHRYSLER EVAP Purge Solenoid Circuit
  • P0445 DODGE EVAP Purge Solenoid Circuit
  • P0445 HYUNDAI EVAP System Purge Control Valve Circuit Shorted
  • P0445 INFINITI EVAP Canister Purge Volume Control Solenoid Valve Circuit Shorted
  • P0445 JEEP EVAP Purge Solenoid Circuit
  • P0445 KIA EVAP Emission System Purge Control Valve Circuit Shorted
  • P0445 MAZDA EVAP Control System Purge Control Valve Circuit Shorted
  • P0445 MERCEDES-BENZ Evaporative Emission Control System Purge Control Valve Circuit Shorted
  • P0445 NISSAN EVAP Canister Purge Volume Control Solenoid Valve Circuit Shorted
  • P0445 SUBARU Evaporative Emission Control System Purge Control Valve Circuit Shorted
  • P0445 VOLKSWAGEN EVAP System Purge Control Valve Circuit Shorted
 

Pygot

Original poster
Member
Dec 6, 2019
82
RI
I will get it checked again but it was scanned with a snapon tool as a chevy trailblazer because the saab doesnt exist as Im sure many of you know. The code I am sure of though I saw it myself and wrote it down right away. Wiring is not my expertise, but I will try to explain what has been done. The wiring for the fuel pump has been replaced, but I do not believe the wiring for the purge valve has been replaced. If I knew what fuse to check or what harness to look at maybe I could try and diagnose it further? Sorry kind of new to electrical problems
 

budwich

Member
Jun 16, 2013
2,027
kanata
As mooseman indicated, p0445 doesn't show up against your vehicle but similar codes (eg. p0455) which might pass your "handwriting test"... :smile:

The problem is probably nothing to do DIRECTLY with a leak but more to do with the operation of valves that should have created a vacuum which didn't happen and hence the system coded.

You need to do some electrical checks along with checking the purge hose to ensure that it isn't plugged.
 
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Mooseman

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Dec 4, 2011
25,262
Ottawa, ON
For P codes, it can be scanned with any cheap code scanner available. The Snap-On would have scanned it too even if specifying a TB and it wouldn't give that code since it's not in GM's list.
 

Chemman

Member
Jul 13, 2013
35
Maryland
Just as an FYI, I looked up the P0445 code on the TechSmart Parts website (it has a DTC code lookup too) and for the Saab it says:

Evaporative Emission (EVAP) Purge Solenoid Valve Control Circuit Shorted

Here is the link to the website:


Scroll down to the 2nd section and on the left you'll see the DTC Lookup link.
 
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Mooseman

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Dec 4, 2011
25,262
Ottawa, ON
However, that could be for actual Swedish Saabs, not the North American TB that were badged as a Saab . In GM Service Information electronic service manual for the 9-7x or other GMT360's, this code does not exist.
 
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Pygot

Original poster
Member
Dec 6, 2019
82
RI
As mooseman indicated, p0445 doesn't show up against your vehicle but similar codes (eg. p0455) which might pass your "handwriting test"... :smile:

The problem is probably nothing to do DIRECTLY with a leak but more to do with the operation of valves that should have created a vacuum which didn't happen and hence the system coded.

You need to do some electrical checks along with checking the purge hose to ensure that it isn't plugged.
Yea so I am dyslexic, Im sure that helps a lot with the whole situation. Lol
 

budwich

Member
Jun 16, 2013
2,027
kanata
One can always go back to the source document, SAE J2012. Here is a copy from 2002 edition...


Edit: for some reason I can go to that link from a google search for SAE J2012,,,, but I cannot get a link that works pasted here??

2nd edit: think I have it edited to work now...


And a screenshot of the particular page...

View attachment 98258
As you know and have shown, there are lots of codes spec'd. However, it is unlikely that the p0445 (or p0444 for that matter) actually occur on the platform in question because of lack of supporting circuitry for detection as the circuit involved is a basic "drive circuit" (power and ground) which I don't think GM ever monitors for electrical conditions (ie. shorts, open). Anyway, the problem will become clearer when and if further information is provided and some tests have been performed.
 

TJBaker57

Member
Aug 16, 2015
2,897
Colorado
As you know and have shown, there are lots of codes spec'd. However, it is unlikely that the p0445 (or p0444 for that matter) actually occur on the platform in question because of lack of supporting circuitry for detection as the circuit involved is a basic "drive circuit" (power and ground) which I don't think GM ever monitors for electrical conditions (ie. shorts, open). Anyway, the problem will become clearer when and if further information is provided and some tests have been performed.

I had a look at a folder of GM DTC documents I collected some months ago. According to those docs it appears that from 2006 onward the EVAP purge and vent circuits are monitored. Perhaps with the change away from the P10 and P12 PCM?


Screenshot_20201027-211045.pngScreenshot_20201027-211105.png

At any rate the P0445 (and others) are as you say not supported.


l also noted discrepancy between the SAE doc and the GM doc for the code P0446. SAE calls it a circuit issue and GM says it's a restriction.
I understand the SAE doc is a guideline of sorts. Variations abound.
 

budwich

Member
Jun 16, 2013
2,027
kanata
The monitoring is not of the actual circuit (electrically) of those devices. The system monitors changes of conditions (eg. vacuum) that it expects to "see" if the device operates as expected. As a result, the system does NOT know if the devices / circuit is SHORTED, OPENED or otherwise as there are no components in the PCM to detect such things. Hence, those codes indicating such are basically "useless" or have no value or meaningless.
 

Chemman

Member
Jul 13, 2013
35
Maryland
Mooseman, I understand what you are saying, and I admit that you are far more capable of a mechanic than I. However, I have learned that GM does not always include all valid DTC codes for their vehicles in their factory service manuals (FSM). About 5 years ago I got a P0466 on our 99 Silverado with a 5.3 l engine. I could not find P0466 in my FSM for the Silverado, it was not on Alldatadiy.com, etc.

When I searched for it on Google, Google kept trying to change it to a P0446 code. Well, I finally found an obscure listing for a P0466 code and it led me to check out the fuel tank pressure sensor circuit. Low and behold, the fuel tank pressure sensor had died. I replaced it and no more P0466 code.

Also, I do agree with you that P0445 does not show up in my FSM for my '04 TrailBlazer. Now whether or not that means it can't throw a P0455 code, I do not know, but I would not be surprised if it did.

Regards!
 
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TJBaker57

Member
Aug 16, 2015
2,897
Colorado
Also, I do agree with you that P0445 does not show up in my FSM for my '04 TrailBlazer. Now whether or not that means it can't throw a P0455 code, I do not know, but I would not be surprised if it did.


For whatever this is worth... A specific code can be requested with a service $17 request. I think the Tech 2 can do it, I usually just do the request myself with an OBD adapter and a serial terminal app since it is far more convenient than lugging out more equipment. If the requested code is not recognized the module responds with a $7F message indicating that the request is out of range.

I have at my disposal a 2002 TrailBlazer, a used PCM for the same year, and a used PCM from a 2003. For these modules I made such requests for not only the P0445 code but several others in that range and found the P0445 not supported. P0440, P0442, and P0446 were supported. Also supported is P1441 which is supposed to detect a stuck open purge valve.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
We shall wait and see for confirmation from @Pygot of the actual code.
 

Pygot

Original poster
Member
Dec 6, 2019
82
RI
Dealing with stabiltrak issues again... will get back to the evap code when time permist (and money). Replaced power steering cooler too so I will get back to this after the inspection next week (I hate Rhode Island :/ )
 

Pygot

Original poster
Member
Dec 6, 2019
82
RI
Well it's time to fix that Evap Code to get it inspected. Replacing the PCM, and if that fails I will have to go back to a different dealership to have them diagnose what is likely a short somewhere. To be clear I replaced only the harness that goes to the fuel pump. Code is for sure a P0445 have confirmed this again.
 

Pygot

Original poster
Member
Dec 6, 2019
82
RI
NP... FWIW... Just making this suggestion based upon the possibility that the OP himself did not get the chance to do the work. If not, he'll never know whether or not "The Dealership" Tech actually did any work other than 'reading the codes'. If they DID .. Why didn't they detect the source of the problem? And just wondering what THAT visit cost him.
This comes back to haunt me just now... looking through stacks of things I fixed I never replaced the Purge control valve or personally checked the wiring to the purge control valve.
 

Pygot

Original poster
Member
Dec 6, 2019
82
RI
Well I'll leave this here so that someone in the future may benefit. Brought it to another dealership, with a competent mechanic who tested the PCM and grounds which were good and confirmed that the Purge Valve on the Engine was stuck closed mechanically- which is why the system held pressure when smoke tested but kept failing. An interesting situation nonetheless I am getting it inspected this week and if anything changes I will post here but hopefully I can finally call this thread complete. Thanks again to everyone for the help!
 

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