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EVAP system on Chevy Uplander

7 messages,  Last post on Jan 14, 2013 at 11:09 AM

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#1 of 7 EVAP system on Chevy Uplander by mr_val

Oct 08, 2011 (6:02 pm)

Hi guys
I am having problems with my EVAP system. The trouble code is P0455. I have been trying to resolve this issue for quite some time, checking almost every possibility. I tried replacing the gas cap, I checked all the vacuum hoses and all the wiring. The engine light appeared after I overfilled my gas tank. So now I'm thinking maybe I flooded my charcoal canister. I am not sure.
 
The other thing that I noticed is that when I refill at the gas station, the gas nozzle kicks back without the tank being full. Now I have heard of people having this problem when their vent solenoid wasn't working. but the thing is that I don't get any other code (like P0466), all this time I've been getting the p0455.
 
I don't want to take my car to a mechanic just yet. Maybe some of you guy have any opinions or have had similar problem. What would be your advice?
 
Thanks

#2 of 7 Re: EVAP system on Chevy Uplander [mr_val] by 442dude

Oct 09, 2011 (6:22 am)

Replying to: mr_val (Oct 08, 2011 6:02 pm)
P0455 is telling you that there is a large leak...you've changed the gas cap and you don't have fuel spilling on your floor and you traced the lines and didn't find any damage...
 
Presuming that you have found nothing that looks out of place, I would investigate the EVAP vent valve solenoid - I'm not sure where its located on the Uplander - you may have to drop/lower the fuel tank to access it. I would bet that the solenoid is stuck closed and its unable to pull vacuum on the fuel tank so it thinks that there is a big leak. The other thing that may be faulty is the fuel tank pressure sensor - if it can't read the negative pressure of the fuel tank during the test it will throw the code as well
 
If your a backyard mechanic, you can try replacing them and see what happens...they should be fairly inexpensive parts - it may take a few days for the code to clear as you have to wait for the test to run...or if you have a good scanner you can clear the code yourself.
 
Or if you go to your mechanic you at least have an idea of what's going on. Good Luck!

#3 of 7 Re: EVAP system on Chevy Uplander [442dude] by mr_val

Oct 09, 2011 (1:14 pm)

Replying to: 442dude (Oct 09, 2011 6:22 am)
Thanks for the reply!
At least now I have something to work with.
 
I was wondering how do you investigate a vent solenoid? I read that one way is to disconnect the vacuum hose from the vent solenoid, capping it off and see if the refueling improves, that is the nozzle would not kick back until the tank is full. So if the refueling does improve then there is a problem with the vent solenoid.
Is there any way to visually tell if the vent solenoid is broken or does not vent?
 
I have heard many people say that "you have to do a smoke test", well I guess I am too stubborn to go the a mechanic, especially since it is not always certain that the problem would be fixed. So I try to basically check off any possibility until I find the problem. Plus all of that is done at home without any special tools.
 
I have never had this problem before, it appeared right after I overfilled the tank, I am suspecting that when I was pouring the gas, some of it went to the charcoal canister. But at the same time I think that overfills happen a lot and manufacturers would think of something to prevent that. That's the confusing part, I don't know if I flooded my canister.
 
Thanks again!

#4 of 7 Re: EVAP system on Chevy Uplander [mr_val] by 442dude

Oct 09, 2011 (1:33 pm)

Replying to: mr_val (Oct 09, 2011 1:14 pm)
If solenoid is above the fuel tank so the only thing you can really check is whether or not the wires are attached to it and are not damaged. The smoke test involves pressurizing the fuel tank with smoke and then cycling the valve with a Tech 2 scanner - if smoke doesn't come out then the valve/solenoid is not working. I don't think overfilling your tank had anything to do with it unless you're still burning the same tank of fuel, then it might take a little time to clear. If you are, then you might want to be patient and wait a couple of weeks before doing anything.
 
If its been a few tanks of gas since the overfill, here's what I'm thinking: If you're mechanically inclined, get a Haynes book or Chilton and replace the solenoid and the valve...You won't even spend $50 total for both of them. I'm confident that will fix your problem.

#5 of 7 Re: EVAP system on Chevy Uplander [442dude] by mr_val

Oct 09, 2011 (6:09 pm)

Replying to: 442dude (Oct 09, 2011 1:33 pm)
Thank you 442dude!!
I will try replacing vent solenoid.

#6 of 7 Re: EVAP system on Chevy Uplander [mr_val] by maddog0324

Dec 12, 2012 (10:12 am)

Replying to: mr_val (Oct 09, 2011 6:09 pm)
mr val,
I know it's been a while since your last post. What resolved your issue? I have a 2006 Uplander LS which has giving me the "Check Gas Cap" message then setting a P0455. I have replaced my gas cap and cleared the codes, but it hasn't resolved my issue. Please let me know.
Thanks,
maddog0324

#7 of 7 Re: EVAP system on Chevy Uplander [maddog0324] by maddog0324

Jan 14, 2013 (11:09 am)

Replying to: maddog0324 (Dec 12, 2012 10:12 am)
Update:
I replaced the EVAP Vent Valve solenoid, then cleared the codes. Two days later, the "Check Gas Cap" message reappeared, but no P0455. I then replaced the EVAP Purge Solenoid and cleared the codes again. It has been two weeks (three re-fuelings & 500 miles) without the "Check Gas Cap" message. All of the I/M monitors have been completed except for the EVAP monitor, which is still showing incomplete. Thankfully, no codes have set. Any ideas why the EVAP monitor is not completed?

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