GMC Repair: Purge vent valve, vent valve, valve question

Question
QUESTION: I have a 2000 Chevrolet 5.3. My service engine soon light comes on and sometimes will go off. I have taken my truck to a couple of parts stores and had it checked. Need to replace the purge vent valve. I done this the light still comes on. What are the next step I should take?

ANSWER: did you clear the trouble code after replacing the vent?  and are all the lines reinstalled securely?  If so, there is still a leak in the system somewhere, most times its a faulty gas cap.  Is the gas cap a factory cap?

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QUESTION: Yes I cleared the code and replaced the gas cap. My next step I was going to try is replace the Evaporator vent solenoid?????????  This was suggested by the dealer. And also replace the vapor canister?????? The dealer did say to wait on the canister, the vent soleniod may take care of it.I did have to replace the fuel regulator it was leaking by. Dont think this had anything to do with the light. What is your opinion??????????????  And Thanks for the help.

Answer
Sorry if there was some confusion, I mis read your statement and thought you had already replaced the solenoid and valve, that is the only way we replace them here.  Unless you can verify that the canister is leaking I would not spend the money on it, though I have seen them leak