GMC Envoy EVAP Issue

This has been quite a journey for me.  I believe I’ve shared with all of you about how my wife hates to have lights on in her car, the Envoy being her car has therefore been quite troublesome as of late.  There is nothing seriously wrong with the truck and it runs great, but the EVAP system has had a small leak for a while now and it is driving me nuts.  No matter what I do to the truck, the check engine light remains.

I have replaced the Vapor Canister Purge valve.

The Vapor Canister Vent Solenoid.

And the Vapor Canister itself:

None of the solutions have resolved the issue.

The next steps in taking care of the problem are to run a smoke test on the entire system.  I’ve looked into making my own smoke machine and some of the internet video’s I’ve watched were quite compelling.

Unfortunately, the way the Envoy’s EVAP system works is to test the system the Vapor canister Purge Valve and the Vapor Canister Vent Solenoid get sealed and then the test is run.  There is a sensor somewhere that determines the amount of vapor in the system and when that number drops below a certain threshold, the Check Engine Light is triggered.  I had no way to properly seal the system with the “home made” smoke machine so I have thrown in the towel and took it to the dealer.  It was quite a blow to my ego to finally cave and take it there.  I figured that they would have the correct smoke machine and diagnostics equipment to finally get this problem solved.

So we take the truck to the dealer and drop it off.  I explained on the drop off envelope that the Check Engine Light is on for a small EVAP leak, that I’ve replaced all the easy stuff and that I think it needs a smoke test to find the leak.  The next day I get a call from their service writer that the Check Engine Light was not on and that they ran a smoke test on the entire system and could not find a problem!  My eyes must have bugged out of my head because I purposely did not clear the codes so that they would see them and be able to at least run down their list.

I ended up telling them to keep the truck for a day or two and drive it around; this was actually their suggestion, to see if the code would come back.  I don’t believe that they ever got the code to come back on but they did suggest replacing all the EVAP lines.  I’m not sure if this is actually going to fix the problem, but that would have been my next step as well.  I let them perform the work because I know, at least I hope, they spent a lot of time diagnosing the issue.  Even though they did not find anything, they seem to be pretty confident that the lines will solve the issue.  Maybe when they warm up they expand and the small leak starts?  I don’t know…..The wife and I have bets on when the light will come back on……

Anyway, they were also able to take care of the window switch recall (12180) on that GMC.  No fires for us!  The final cost was $796.25.  Now I know why I don’t take it to the dealer.  Way too expensive and they were not any better at diagnosing it than I was, even with the smoke machine.  At least my ego had a little boost out of it……

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