Im sure the millionth p0446 question.
 

98 Yukon, p0446 code. From what I can tell, the module is in the front driver side of the engine compartment. My finger is on the end of the vent, i think, its got a sponge inside which i cleaned out. I think the actual valve is forward of the sponge cartridge. Do I need to pull that, test the voltage, and clean it? Maybe replace? What is the correct name for these two parts if i need to replace them. Thanks.

the part you have your finger on is the vent valve or evap vent valve. the thing its attached to is the canister. try taking the valve apart and shoot some wd40 in the solenoid and rig up some wires so you can jump 12v in it try both directions and see if it activates. if so its good, activate it a couple times to work in the wd40 and see if it holds air when you blow through it and seals when you activate it

Sounds good. Thanks for the idea. How did you apply 12V to it? I would think directly off the battery is a bad idea.

Direct from the battery ... in a safe manner of course.

i use little insulated alligator clips to jump it to the battery you just dont want anything that will allow them to touch, unless you like molten metal and sparks. probably available at radio shack