PO449

My 2008 Silverado had a code PO449 and I checked it out and replaced the EVAP vent solenoid because it had power but was not clicking and that took care of the problem. This was about two weeks ago. Yesterday I don't know if this had any thing to do with it but I hit a puddle and noticed that the Engine light had come on so I checked it and the same code came back up. So I was wondering when I turn the key on should that solenoid have power all of the time or is it intermittent? also If I put power to that solenoid should it click continuously or just one time?
I'm trying to figure out if the solenoid went bad again or if I have other problems. I put a pigtail marker light in the plug to check for power but it only stays on for a second or two before the check engine light comes on and then I have no power at the plug

"So I was wondering when I turn the key on should that solenoid have power all of the time or is it intermittent? also If I put power to that solenoid should it click continuously or just one time?"

Should have continuous B+ Key on.
Should click once.
Keep in mind that the PCM provides a ground to the solenoid to turn on.
If you directly substitute the marker light for the solenoid then the circuit is dependent on the ground from the PCM.

BBBind.com has schematic.

I put power and ground to the solenoid off the truck and it clicked once. I reinstalled on the truck and engine light is now off and seems to be working. Not sure if solenoid was stuck and sending the code

Since this happened a few times suspect solenoid/circuit intermittent.
If solenoid worked consistently when tested off the truck then could be circuit or PCM intermittent.

Hopefully removing installing cleaned electrical contacts and all is well.