Since the issue is running the Battery down, I would replace the PCM power relay for stuck or burned closed contacts that never removes power to the system.
Ford DTC list says short to battery/damaged PCM relay.
Seems to fit the cause.
Check out #66, see page 292.
Check out #109, see page 294.
Remember, the system normally supposed to go into sleep mode after 30 to 45 minutes.
That is not happening.
Good luck.

 

Did you ever track down the solution?

 

I hate when people don’t come back and mention the actual solution!!!! Too many information takers and not enough information givers.

 

Did you ever figure out what was wrong with it? I am having the same issues with my 15