Hello I'm Chris a Ford Employee and Certified Engine/Transmission Specialist.
Thanks for asking your question. I am eager to get your vehicle back up and running correct, I am here to help you out for a small fee far less than a dealership and easier on the wallet, so if this information is of aid PLEASE PRESS ACCEPT and help me out financially by paying the small fee. Please reply if further discussion is needed.
This is not a common problem and there is not a simple answer. I am posting the exact same ford instructions I would use at my dealer to diagnose this. Reply if you need help with this test.
This is the diagnostic pinpoint test we at the ford dealer use to diagnose an inoperable malfunction indicator lamp.
MIL=check engine light
B+= battery 12 volt power
Junction box= fuse box
Break out box= a dealer piece of testing equipment.
Does this help. Hopefully you will not get to the step for the break out box since you want own one.