Horn comes on and off none stop I stop it with.

The door ajar switch is located in the latch assembly and there is no familiar button as in older cars. I have the same car and was told by another mechanic to spray lube into the latch and then open and close the door several times. This did help when I did mine. Remove the battery cables and clean the connections as well. This will clear the computer at the same time. This did work on my Lincoln. Good luck