Its number three in the diagram unplug it and see if you can blow thru it if you can then its stuck open and needs to be replaced. Changing the gas shouldnt have effected the code P0455 that code is for the fuel pressure sensor detected vacuum when there wasnt supposed to be vacuum to the tank. Its not for a leak in the evap system.
November, 26, 2011 AT 12:44 AM
Hmm. Went to a dealer today to get the Evap Emission Vent valve/solenoid (he gave me a Delco/GM part #25932570, pic attached). I asked him if that was located on the engine. He said no, it's down at the gas tank/Evap Emiss Canister, the one on the engine is the purge valve.
I jacked the car up and I can't see anything that looks like this new part on or around the Evap canister. I looked up the canister on the internet & found photos of all sides of the canister and that new part is not on the canister, unless it's under a cover or located on the gas tank where I can't see it.
I took the top cover off the engine and did locate the solenoid valve (item #3) as you indicated in your thumbnail above. The new valve I got does not look anything like the one on the engine.
You said P0455 was vacuum in the fuel tank when it wasn't supposed to be there. Am I correct in assuming that the purge valve is what opens to provide the vacuum in the fuel tank when needed (during Evap System testing I guess)?
November, 26, 2011 AT 12:57 AM
The vent valve by the gas tank closes and the canister purge valve opens to allow vacuum to the gas tank to pull a vacuum in the gas tank. Then the fuel tank pressure sensor measures the vacuum being pulled on the gas tank so it can tell if there is a leak in the evap system. The P0455 means there is a vacuum present in the evap system when the ecm didnt command one. Most of the time its caused by the canister purge solenoid being stuck open all the time. Thats why I said to unplug the electrical connector to it remove the vacuum lines to it and blow thru it to see if its stuck open. If its stuck open then to replace it.
November, 26, 2011 AT 6:38 PM
OK, checked the purge valve on the engine. Unhooked the electrical connection & evap hose, blew into purge valve and no air passes through, so it is closed. So I can assume it's a problem with the vent valve (I had this diagnosed awhile back & one thing they found was the resistance on the vent valve was too high, the estimate to fix was $600 to start)?
I have found the vent valve by accessing the repair manual online. Seems it's mounted on the right rear of the gas tank behind the evap canister, very hard to see as it's mounted near the top of the gas tank. The instructions say to lower the exhaust system towards the rear of the car. Then lower (not remove) the gas tank to get access to the vent valve (there are other steps like unhooking the filler neck, etc.).
Unless you have some ideas I think I'm done. I doubt that I can change the vent valve from laying on the ground with the car jacked up, not enough room. Well It was worth a try to see if it was something that I could fix.
What prompted me to look at it was they are going to charge me another $100 to plug in their code reader again just to fix the same problem. I think that's a bit much.
November, 27, 2011 AT 9:01 PM
Changing the vent valve from the ground is do able if you get the back of the high enough. What code number is active now?
November, 28, 2011 AT 8:08 AM
Same as before, P0449.
November, 28, 2011 AT 7:04 PM
With the key in the run position make sure you have power to both sides of the emissions 2 fuse in the rear fuse box. If you do with the key still in the run position see if you have power at the connector of the vent valve terminal A its the red wire with a white tracer. Also make sure the terminals arent open at that connector. If all that is good with the key in the run position and thr engine off all these tests is with the engine off. With the vent valve connector plugged in back probe the white wire at the vent valve then ground that wire and unground it and ground it you should hear thumping noise while doing this meaning the vent valve is working. Let me know what you find.
November, 28, 2011 AT 9:04 PM
Fuse is good, juice at both sides of fuse. No thumping of the vent valve with the other tests. Looks like the vent valve is bad. Thanks for all your help. Hope someone else gets something useful out of these posts.
November, 28, 2011 AT 9:31 PM
Alright if you are cycling power and ground to the vent valve and you cant hear it thumping then yes it is bad. Glad I could help you figure the problem out.