Code B2409 and how do I go about fixing this?

The B2409 code tells you there is an issue with the driver side key cylinder switch. I would remove the door lock on the driver's side and check to make sure none of the wires got broken. By chance have you had the door slim jimmed? This can break wires internally. You will need to remove the door panel which I have included in the images below along with the door lock assembly. Check out the images (below). Please upload pictures or videos in your response to the problem so we can see what's going on.