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Discussion Starter · #1 · (Edited by Moderator)
Hey guys! I have a 2wd 08 GMC Acadia, we had the check engine light come on about a month and a half ago, the code at that time was po455 I think? We replaced the gas cap, air intake hose and purge valve.
Now when its nicer I have no issues, but this last week or so that it has been cold it will flash tighten gas cap and then the check engine light will come in and when I read it the code is p0449. I will attach the photo of that read. At any rate I'm at a loss of what to do. Any pointers would be great :)
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Discussion Starter · #2 ·
I should add that it has no issues starting, no noticeable changes in the way it runs , and I do notice a stronger odor of gas when I first start it.
 

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Could be an issue with the wiring harness preventing the purge valve from activating. Need a scan tool that can activate the valve.

If that tests OK, I would be looking at an issue with the PCM.
 

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Could be an issue with the wiring harness preventing the purge valve from activating. Need a scan tool that can activate the valve.
The canister vent valve is different from the purge valve. The vent valve is located under the vehicle near the EVAP canister. It's going to require some good EVAP system troubleshooting to locate and repair the problem. The problem could be in the wiring, hoses, or canister itself.
 

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Discussion Starter · #5 ·
The canister vent valve is different from the purge valve. The vent valve is located under the vehicle near the EVAP canister. It's going to require some good EVAP system troubleshooting to locate and repair the problem. The problem could be in the wiring, hoses, or canister itself.
Okay thanks guys!. It has been getting frustrating. I am gonna do a freeze frame when I go to clear the code , apparently that will tell me how its affecting the vehicle ?
 

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Okay thanks guys!. It has been getting frustrating. I am gonna do a freeze frame when I go to clear the code , apparently that will tell me how its affecting the vehicle ?
Here's an interesting article about the vent valve, how it works, and troubleshooting on other makes: EVAP Vent valve (solenoid): how it works, problems, testing. You might find the information helpful. A scan tool (not just a scanner) would certainly be useful for troubleshooting the problem. You can find Acadia-specific information in the service manual. Several service manuals are available for download in another part of the forum. Fortunately, few if any changes have been made to the EVAP system during run of the Lambda platform, so troubleshooting guides in either the 2010 or 2013 manual should be similar.
 
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