Where is the Vapor Canister Vent Valve/Solenoid located?

It is behind the cover inside the right rear wheel arch mounted on the EVAP canister. To get to it you remove the right rear tire, then pull the push retainers and bolts that hold the liner in place. With it out you will see the pipe that runs from the fuel tank to the EVAP canister. Disconnect it and the vent line and the electrical connector. Then release the tab and you can lower the EVAP can enough to get to the release clips on the solenoid. Replace it and reverse the process to put it back together.

It is mounted on the canister itself. The OE is replaceable; however they generally don't sell just the solenoid, you instead buy the complete canister. Also, it looks like they updated the service info on it, the canister in the new information is next to the fuel tank. You lower the tank to get to the canister. The earlier info was for the Cts from the looks of it. Don't get many of the XTS in here so didn't question the info. Sorry about the wild goose chase.