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Discussion Starter #1
My 05 Silverado check enging light went out when I replaced the gas cap. It came back on after 2 tanks of gas and won't go out now. Advance Auto Parts read the code and it still is still saying it is a bad gas cap. They replaced the new cap but the light is still on. What else could it be? I don't know exactly what the code read but they said something about a bad solenoid which they said meant gas cap.
 

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It is picking up a slight EVAP system leak that normally is repaired by tightening or replacing the gas cap, but if it has come back, you may have a leak in one of the vent hoses between the gas tank and the engine.
 

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Have them print out the code if they can so you know what it is. Then come back here and post the code, someone can look it up for you.
 

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Discussion Starter #4
the codes are

P0449
EVAP Emission Control System
Vent Vlv/Sol Malf

and

P0455
EVAP Emmision Control System
Leak (Large)
 

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Sounds like the EVAP solenoid has either gone bad or become disconnected and is causing a vacuum leak. There may be an emission diagram under the hood showing it's location.
 

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Discussion Starter #6
I found the evap soloniod release valve on the top of the engine. I unscrewed it and found a valve like you would find on a tire. Should I push it to see if that helps clear the problem? Would it cause damage or problems if I did?
 

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I have had this happen several times- each time because the wife put gas in and did not have the gas cap tight enough- i.e. there was not back pressure in the gas tank. Each time, I tightened it down, and sure enough the light went out after 3-4 starts.

I also remember this happening repeated each time she filled up at one particular gas station.... Since this is an emmissions issue, I wonder if bad gas could cause this to happen ?
 

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Did this ever resolve itself?
 
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